Claims:1. A power microwave integrated circuits (MIC), comprising:
a power amplifier device (101, 201) mounted on a composite multilayer printed circuit boards (PCBs) (202), wherein the power amplifier device (101, 201) is attached to a first layer of the composite multilayer PCBs (202), and
wherein the power amplifier device (101, 201) is configured to receive an input RF energy from a driver amplifier (102) to thereby generate a required RF power output for operating an electronic device.
2. The power MIC as claimed in claim 1, wherein the power amplifier device (101, 201) is attached to the first layer (203) of the composite multilayer PCBs (202) using a conductive material (215), the conductive material is one of an epoxy paste or a solder paste.
3. The power MIC as claimed in claim 1, wherein the power semiconductor device includes a plurality of the thermal plated vias passing through the composite multilayer PCBs (202) that transfers heat generated from the power amplifier device (101, 201) to a heat sink or a metal plate (214).
4. The power MIC as claimed in claim 1, wherein at least the first layer (203) of the composite multilayer PCBs (202) is adapted to realize RF traces and supply and controls traces.
5. The power MIC as claimed in claim 1, wherein the power MIC comprises a controller and sequencer device (110) to monitor an estimate RF level being fed to the power amplifier device (101, 201) and thereby control the input RF energy generated from a driver amplifier (102).
6. The power MIC as claimed in claim 1, wherein the power MIC comprises a drain pulsing circuit (104) and a gate supply circuit (109) coupled to the controller and sequencer device (110), wherein the drain pulsing circuit (104) and the gate supply circuit (109) adapted to control operations of the power amplifier device (101, 201).

7. The power MIC as claimed in claim 1, wherein the power MIC comprises one or more charge storage capacitors (105) positioned in near proximity of the power amplifier device (101, 201) for pumping current drawn by the power amplifier device (101, 201) and for preventing noise feedback path in diet current (DC) lines.
8. The power MIC as claimed in claim 1, wherein the power amplifier device (101, 201) is one of a gallium nitride (GaN) or a gallium arsenide (GaAs) based device using a surface-mount technology (SMT).
9. The power MIC as claimed in claim 1, wherein the power MIC comprises at least one of temperature sensors, RF detectors, and a protection circuit to monitor and control one or more operations of the the power amplifier device (101, 201).
10. The power MIC as claimed in claim 1, wherein the composite multilayer printed circuit boards (PCBs) (202) is coupled to one of a metal plate (214) or a heat sink using an adhesive (213).
, Description:TECHNICAL FIELD
[001] The present disclosure relates to a field of high power electronic components. More particularly, the present invention relates to microwave integrated circuits (MIC’s) with surface mount high power electronic device. More specifically, present disclosure relates to method and procedure to employ surface-mount technology (SMT) type high power radio frequency (RF) device attached to composite multilayer printed circuit boards (PCBs).

BACKGROUND
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Because radio frequency (RF) devices such as power amplifiers, couplers, baluns, etc., are integral parts of every wireless device or system, they must also do more in a smaller footprint. Accordingly, size reduction, improved heat dissipation, power handling, and cost reduction are important considerations for today's RF component designs.
[004] A prior-art reference US 7365273 B2 titled “Thermal Management of Surface-Mount Circuit Devices” discloses a circuit board assembly having a laminate construction of multiple layers, such as a LTCC ceramic substrate, with conductor lines between adjacent pairs of layers. A heat sink is bonded to a first surface of the substrate, and a cavity is defined by and between the heat sink and the substrate such that a base wall of the cavity is defined by one of the layers with conductor lines thereof being present on the base wall. A surface-mount circuit device is received within the cavity, mounted to the base wall, and electrically connected to the conductor lines on the base wall. The device is received within the cavity such that a surface of the device contacts a surface region of the heat sink. The surface of the device is bonded to the surface region of the heat sink to provide a substantially direct thermal path from the device to the heat sink.
[005] Another prior-art reference US 6784837 B2 titled “Transmit/Receive Module For Active Phased Array Antenna” relates to a transmit/receive module for a high power Active Phased Array Antenna System operating in L-band based upon a combination of Hybrid Microwave Integrated Circuit (MIC) as well as Monolithic Microwave Integrated Circuit (MMIC) technology. The transmit/receive module includes a power monitoring means, transmitter protector means, and a receiver protector means. The module comprises a signal transmit chain incorporating power conditioner and a signal receive chain incorporating control electronics and bias- Sequencer modulator. The transmit chain has Switching means for Switching the module to transmit mode which is connected to the transmit amplifier chain through a shared digital phase shifter. The amplified signals from the transmit amplifier chain are conveyed to a duplexer means. In receive mode, the receive chain receives. Signal through drop-in circulator and high power switch and comprises of high power limiter, low noise amplifier means, and a digital attenuator means connected to the shared digital phase shifter through T/R Switch means. Electronic means are connected through integrated control electronic, bias Sequencer modulator and power conditioner for controlling the operation of the device.
[006] Another prior-art reference US 5912809 titled “Printed Circuit Board (PCB) Including Channeled Capacitive Plane Structure”, teaches electrical potentials and very high frequency (VHF) currents in a circuit board are controlled by patterning the power plane of a multiple layered, capacitive plane printed circuit board in selected geometric patterns. The selected geometric patterns are both simple and complex, control voltages and currents by channeling the capacitance capacity for usage directed to a particular integrated circuit or circuits, isolated to a particular integrated circuit or circuits, or shared between integrated circuits. Accordingly, the capacitive planes including the geometrically patterned power plane are channelled capacitive planes (CCP) that are formed on multiple layers of a single printed circuit board to support flexible, three-dimensional control of VHF electrical currents.
[007] Yet another prior-art reference US 2017/0041038 A1 titled “UNIVERSAL TRANSMIT/RECEIVE MODULE FOR RADAR AND COMMUNICATIONS” discloses a universal transmit-receive (UTR) module for phased array systems comprises an antenna element shared for both transmitting and receiving; a transmit path that includes a transmit-path phase shifter, a driver, a Switch-mode power amplifier (SMPA) that is configured to be driven by the driver, and a dynamic power Supply (DPS) that generates and supplies a DPS voltage to the power supply port of the SMPA; and a receive path that includes a TX/RX switch that determines whether the receive path is electrically connected to or electrically isolated from the antenna element, a band pass filter (BPF) that aligns with the intended receive frequency and serves to suppress reflected transmit signals and reverse signals, an adjustable-gain low-noise amplifier (LNA), and a receive-path phase shifter. The UTR module is specially designed for operation in phased array systems. The versatility and wideband agility of the UTR module allows a single phased array system to be designed that can be used for multiple purposes, such as, for example, both radar and communications applications.
[008] In today’s scenario, it is intended to have miniaturised, compact and dense RF sub modules meeting all the required RF performance in addition to managing thermal issues efficiently. Typically Transmitter, Up-converter modules for various applications house devices that are suitable to emit high RF powers typically in order of tens to hundreds of Watts (CW or pulsed mode) accommodated in compact real estate. For simple assembly process and realizations of circuits on composite PCB without any PCB breaks (discontinuities) calls for surface mount high power devices instead of bare die. Though bare die would be better choice for better thermal management and minimum parasitic losses as compared to packaged devices.
[009] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0010] In some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0011] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

SUMMARY
[0012] The present disclosure relates to a field of high power electronic components. More particularly, the present invention relates to microwave integrated circuits (MIC’s) with surface mount high power electronic device. More specifically, to method and procedure to employ surface-mount technology (SMT) type high power radio frequency (RF) device attached to composite multilayer printed circuit boards (PCBs).
[0013] The present disclosure relates to use of surface mount high power RF devices, typically a gallium nitride (GaN) or a gallium arsenide (GaAs) based. These high power devices are mounted on a composite multilayer printed circuit board to realize microwave integrated circuits (MIC’s). This configuration is typically for applications where both RF circuitry and digital circuitry are densely populated and interconnection, routing and distribution are done on single composite multilayer card. Managing thermal and RF performance to optimum level is a key design and implementation challenge. Thus the present invention is a solution to mentioned challenges.
[0014] The present invention proposes method and procedure to employ SMT type high power RF device attached to multi-layer composite PCB (N-layers). This method is combination of configurations and key process steps. The configuration is combination of various devices (surface mount PA, driver amplifier and sensors), circuits (pulsing circuits, monitoring and sequencing), passive samplers, and plurality of suitable capacitors. All these are realized as Microwave integrated circuits (MIC’s) on a single composite multilayer PCB for ease of assembly and design for manufacturability.
[0015] SMT type RF device can generate typically up to few 100’s of Watts’s peak power, or 10’s of Watts’s of CW (average) power. Placement of pulsing circuits and charge storage capacitors ensures the duration for which High power RF device is to be kept ON. It also ensures optimum RF and thermal performance Presence of sensors, monitoring and sequencing circuit ensures to maintain health of high power RF device. Presence of Controller and sequencer which are the mastermind, monitors these output of sensors and monitoring circuits and flags if presence of any anomaly besides switching of the high power device to prevent any damage.
[0016] The next key design aspect of entire scheme is how the configuration is layed out on single composite multilayer PCB formed by combination of substrates suitable for RF designs and substrates that are economical and suited for lower frequency designs. For N-layer composite board, Layer 1, 3 . . . N-2 is only employed for designs. Layers 2, N-1and N are realized as complete Cu layers devoid of any routing. There can be additional layers with complete Cu layers devoid of any routing if RF traces realized in inner layers. Power patches and dedicated power planes to transfer high currents with minimum ohmic losses. Power vias/ signal vias are restricted to carry signals only up to N-2 layer. Plurality of thermal vias (PTH) to stitch all ground layers for optimum RF performance and better heat transfer are filled with conductive substance and cap plated are used to connect all N layers.
[0017] Various adhesives are suitably chosen as binding material at different interfaces considering the thermal and RF performance aspects. This entire assembly is directly attached to broad mechanical enclosure or metal base using a conductive adhesive, for maximum heat transfer and for providing optimum RF and supply ground reference
[0018] Step by step inspection and assembly steps ensure proper contact between each items suited for applications for optimum RF and thermal performance.

BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0020] In the figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
[0021] FIG. 1 illustrates an exemplary configuration for thermal and RF performance of high power amplifier, in accordance with an exemplary embodiment of the present disclosure.
[0022] FIG. 2 illustrates an exemplary stack of surface mount high power RF device on a composite multilayer board (PCB) that is attached to a metal plate or heat sink, in accordance with an exemplary embodiment of the present disclosure.
[0023] FIG. 3 illustrates an exemplary layout design of key layers for better RF and thermal management, in accordance with an exemplary embodiment of the present disclosure.
[0024] FIG. 4 illustrates an exemplary method of for inspection and attachment to achieve optimum performance, in accordance with an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION
[0025] The following detailed description is made with reference to the technology disclosed. Preferred implementations are described to illustrate the technology disclosed, not to limit its scope, which is defined by the claims. Those of ordinary skill in the art will recognize a variety of equivalent variations on the description.
[0026] Examples of systems, apparatus, computer-readable storage media, and methods according to the disclosed implementations are described in this section. These examples are being provided solely to add context and aid in the understanding of the disclosed implementations. It will thus be apparent to one skilled in the art that the disclosed implementations may be practiced without some or all of the specific details provided. In other instances, certain process or method operations also referred to herein as “blocks,” have not been described in detail in order to avoid unnecessarily obscuring the disclosed implementations. Other implementations and applications also are possible, and as such, the following examples should not be taken as definitive or limiting either in scope or setting.
[0027] In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific implementations. Although these disclosed implementations are described in sufficient detail to enable one skilled in the art to practice the implementations, it is to be understood that these examples are not limiting, such that other implementations may be used and changes may be made to the disclosed implementations without departing from their spirit and scope. For example, the blocks of the methods shown and described herein are not necessarily performed in the order indicated in some other implementations. Additionally, in some other implementations, the disclosed methods may include more or fewer blocks than are described. As another example, some blocks described herein as separate blocks may be combined in some other implementations. Conversely, what may be described herein as a single block may be implemented in multiple blocks in some other implementations. Additionally, the conjunction “or” is intended herein in the inclusive sense where appropriate unless otherwise indicated; that is, the phrase “A, B or C” is intended to include the possibilities of “A,” “B,” “C,” “A and B,” “B and C,” “A and C” and “A, B and C.”
[0028] Some implementations described and referenced herein are directed to systems, apparatus, computer-implemented methods and computer-readable storage media for detecting flooding of message queues.
[0029] Thus, for example, it will be appreciated by those of ordinary skill in the art that the diagrams, schematics, illustrations, and the like represent conceptual views or processes illustrating systems and methods embodying this disclosure. The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing associated software. Similarly, any electronic code generator shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the entity implementing this disclosure. Those of ordinary skill in the art further understand that the exemplary hardware, software, processes, methods, and/or operating systems described herein are for illustrative purposes and, thus, are not intended to be limited to any particular named.
[0030] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0031] The present disclosure relates to use of surface mount high power RF devices, typically GaAs or GaN based. These high power devices are mounted on a composite multilayer printed circuit board to realize microwave integrated circuits (MIC’s). This configuration is typically for applications where both RF circuitry and digital circuitry are densely populated and interconnection, routing and distribution are done on single composite multilayer card. Managing thermal and RF performance to optimum level is a key design and implementation challenge. Thus the present invention is a solution to mentioned challenges.
[0032] RF performance and thermal management are the key aspect of any RF design especially when RF sub modules for various applications demand high performance in small real estates. Thus High power devices are packaged in small form factors. The present disclosure relates to use of surface mount high power RF devices, typically GaAs or GaN based. These high power devices are mounted on a composite multilayer printed circuit board to realize microwave integrated circuits (MIC’s). This configuration is typically for applications where both RF circuitry and digital circuitry are densely populated and interconnection, routing and distribution are done on single composite multilayer card.
[0033] For simple assembly process and realizations of circuits on composite PCB without any PCB breaks (discontinuities) calls for surface mount high power devices instead of bare die.
[0034] The present invention proposes method and procedure to employ SMT type high power RF device attached to multi-layer composite PCB (N-layers). This method is combination of configurations and key process steps. The configuration is combination of various devices (surface mount PA, driver amplifier and sensors), circuits (pulsing circuits, monitoring and sequencing), passive samplers, and plurality of suitable capacitors. All these are realized as Microwave integrated circuits (MIC’s) on a single composite multilayer PCB for ease of assembly and design for manufacturability.
[0035] SMT type RF device can generate typically up to few 100’s of Watts’s peak power, or 10’s of Watts’s of CW (average) power. Placement of pulsing circuits and charge storage capacitors ensures the duration for which High power RF device is to be kept ON. It also ensures optimum RF and thermal performance Presence of sensors, monitoring and sequencing circuit ensures to maintain health of high power RF device. Presence of Controller and sequencer which are the mastermind, monitors these output of sensors and monitoring circuits and flags if presence of any anomaly besides switching of the high power device to prevent any damage.
[0036] The next key design aspect of entire scheme is how the configuration is layed out on single composite multilayer PCB formed by combination of substrates suitable for RF designs and substrates that are economical and suited for lower frequency designs. For N-layer composite board, Layer 1, 3 . . . N-2 is only employed for designs. Layers 2, N-1and N are realized as complete Cu layers devoid of any routing. There can be additional layers with complete Cu layers devoid of any routing if RF traces realized in inner layers. Power patches and dedicated power planes to transfer high currents with minimum ohmic losses. Power vias/ signal vias are restricted to carry signals only up to N-2 layer. Plurality of thermal vias (PTH) to stitch all ground layers for optimum RF performance and better heat transfer are filled with conductive substance and cap plated are used to connect all N layers.
[0037] Various adhesives are suitably chosen as binding material at different interfaces considering the thermal and RF performance aspects. This entire assembly is directly attached to broad mechanical enclosure or metal base using a conductive adhesive, for maximum heat transfer and for providing optimum RF and supply ground reference
[0038] The configuration as seen in FIG. 1 consists of driver amplifier (Item-102) and high power RF amplifier (PA, Item-101). Typically, Item-102 is a GaAs based SMT type, some special application it can be GaN based also. Item-101 is high power (multi-stage) amplifier i.e. GaN/GaAs based operating at voltages (> +5V). Item- 102 provides necessary RF power to Item-101 after amplification of RF energy fed to it. This RF power fed to Item -102 can be sampled out using Item-112 and fed to a detection circuit Item-113. The video output M5 from Item-113 is monitored by controller and sequencer (Item-110). This information helps Item-110 to estimate the RF level fed to Item-101. If more RF power needs to be pumped in, then Item-110 sends a control C4.
[0039] Typically, Item-102 is surface mount GaAs based RF device. Item-102 may operate on drain supply only. But some other applications may need both drain and gate supply for its operation. Also based on recent trends Item-102 can be GaN based too. Associated circuitry for turning on Item-102 plays crucial role. It is associated with gate supply circuit (item-111) is Item-102 operates on dual supply. In this case Item -111 is to sense gate voltage and send status M4 to Item-110, so that drain voltage can be sequenced according to presence of gate voltage. Item-110, generates and provides C5 control to Item-111 in case of gate pulsing. Item -111 is combination of high speed analog switches (-ve voltage operating) and couple of necessary capacitors. Item-110 generates control C1 to pulse drain supply circuit (ckt) (Item-103) for either types of Item-102 (single supply or dual supply based amplifier). The control C1 and C5 helps to manage power consumption and thus thermally manage Item-102 when operated in pulsed condition based on duty cycle. Item -103 is combination of high speed analog switches (+ve voltage operating) and couple of necessary capacitors.
[0040] Item-101 is the high power RF device (power amplifier). It boosts the RF energy fed in by Item-102 to required RF power level. These high power devices (Item-101) are internally multi-stage and typically have multi-stage supply lines. Item-109 is gate supply circuit to Item-101. Item-109 is combination of high speed analog switches and combination of capacitors that are strategically chosen and placed for high speed pulsed operations. C2 is pulsed information provided by Item-110 to control Item-101 based on input provided by Item-109. M1 is fed to Item-110 to indicate presence of –ve gate voltage. This input is processed by Item-110, and control C3 is fed along with drain pulsing information if any into Item 104 (Drain pulsing circuit). The control C3 ensures drain voltage is not available to Item-101, until gate is present. Item 104, is combination of high speed MOSFET drivers and a low ON resistance MOSFET or GaN based drivers. Associated with is effective charge storage capacitors Item-105 that are placed strategically closed to Item-101. Item-105 is combination of high value charge storage capacitors (in uF range) with other low value capacitors (in nF and pF range) close to power amplifier, for pumping current drawn by PA and for preventing any noise feedback path in DC lines. Tantalum based capacitor having low Effective Series Resistance (ESR) is used for high value charge storage capacitors. Ceramic capacitors with necessary rating used for low value capacitors. More number of capacitors may be used for providing enough charge, in turn current requirement of Item-101.
[0041] For protection and RF monitoring Item-106 (temperature sensor) and RF power sampler (item-107) and RF power detector ckt (Item-108) play important role. Item-106 is placed in closed vicinity of Item-101, which provides temperature data sensed by it in terms of voltage to Item-110 to take decision. If Item-110 detects any anomaly, then flags and triggers command C3 to Item-104 to turn OFF Item-101. Similarly, a tapped RF power out of Item-107 is processed in Item-108, and equivalent voltage data is sent to Item-110 for analysis and determine RF health of Item-101.
[0042] The key design aspect of entire scheme is how the configuration is layed out. Stack of Surface Mount high power RF device on a composite multilayer board (PCB) that is attached to a metal plate or heat sink is shown in FIG.2. Here Item-201 is the high power surface mount RF device that is placed on composite multilayer stack up (Item-202). Item-201 is attached to layer 1 (Item-203) of Item-202 by using conductive epoxy or solder paste (Item-215). Item-203 is used to realize all RF traces and supply and controls traces. All the devices are attached onto Item-203 only.
[0043] In and around high power devices and supply lines carrying significant current have power patches etched in Item-203. Distributions of supply and control lines also take place in inner layers Item-207 …Item-210. If RF traces run in inner layers then layer beneath and above are dedicated ground layers. Item-206 is dedicated ground layer, i.e entire copper patch is used as GND reference for RF and thermal relief of Item-203. Substrates suitable for RF designs are used to route RF traces, supply and control traces are typically routed in layers formed on economically viable substrates. Plurality of supply vias or RF vias (Item-204) are used to connect traces/ power patches realized in layers 3,…, N-2, to traces realized on Item-203. Item-204 is realized as plated, conductive epoxy filled and cap plated blind via.
[0044] Item-205 in plurality are the plated through holes that are conductive epoxy filled and cap plated. And stitches all ground layers. It connects all layers from Item-206 to Item-212. Item -211 and Item-212 are layers N-1 and layer N of Item-202. These layers are complete copper patch with no presence of any traces or Item-204. These only aid for effective attachment of Item-202 onto Item-214 that is mechanical enclosure or a metal base (cold plate) with help of adhesive Item-213. Adhesive Item-213 is suitable for efficient heat conductivity that transfers heat generated from Item-201 through Item-202 to Item-214. Also plurality of the thermal plated vias (Item-216) are placed under Item-201 are suitably placed to take away heat generated by high power RF devices (Item-201).
[0045] Layout design of key layers for better RF and thermal management, is shown in FIG.3. Here the top most layer is where all the SMT devices are mounted and RF as well as supply and control traces are realized. Item-301 is the high power RF device. We can see many thermal vias holes strategically placed underneath, Number of these thermal via’s and minimum distance between them is planned based on the heat which is generated by High power device and manufacturability of PCB. Also having the plurality of these via’s provides minimum inductive path for RF ground reference, which is necessary for superior RF performance. Item-303 are power patches in top most layer that carry high current on drain side. All pulsing and supply circuits are associated with these patches to provide supply to high power RF devices. These patches provide minimum ohmic losses by increasing area of current flow. Also multiple signal via’s used to connect to inner layers.
[0046] Item-302, is charge storage capacitor that are tantalum based with relevant rating and are distributed close to Item-301. Item-304 is the pulsing circuit placed to Item-304 as was explained in FIG.1. Item-305 is the temperature sensor that is placed at closed proximity of Item-301 and provides the details of temperature data present around it. Item-306 is RF power sampler and RF power detector ckt which provide data on RF health at output of Item-301. As RF is realized on top most layer, for its optimum performance the layer just beneath it is realized as complete copper patch as seen (Item-307). This copper patch is complete ground and provides ground reference to RF and supply traces realized on top most layer. This also aids in spreading thermal heat generated over wide area. Also live signal via’s have necessary clearance on this patch. Item-308 are power patches in inner layers to distribute high currents, which are connected to top most layer by having plurality of signal vias. Item-309 is traces to connect controls and distributions in inner layers. Item-309 also can be used to connect RF traces; in that case it would be realized as stripline trace with GND layers realized immediately above and beneath it. Item-310 is complete ground layers realized in layer N and Layer N-1. Here we make out from FIG.3, that there are no live signal vias and on plurality of thermal vias are present. And the copper patch in layer N is completely exposed, this helps to attach the entire assembly onto the mechanical cold plate as shown in FIG.2 for optimum heat transfer.
[0047] The key to achieve optimum performance of configuration is explained as flow chart in FIG.4. At onset individual articles are to be initiated for check (Item-401). Item-402 is inspection of high power SMT type RF device. As these devices are sensitive to ESD, they are to be handled carefully. Visual check is first step of inspection to check for any damage. Here check whether exposed leads/pads are free of unwanted particle and is clean for attachment. (Very important step to ensure SMT package has maximum area and least parasitic paths available for attachment). Next is to see electrical parameters, (Gate lines show resistances typically (>k? range), when probed between Gate pad and centre GND patch, ensure ‘–ve’ probe of multi-meter used for probing and ‘+ve’ is used to probe GND). If DC blocks are present inherently, then RF path shows resistance in (M? range/Open).
[0048] Based on observations for electrical and visual check decision Item-404 can be taken to proceed with next stage of attachment or assembly.
[0049] Similar to check of Item-402, Item-403 is check for N layer composite PCB. The entire concept is depended on how well the design and manufacturing of this PCB ensures RF and thermal management. Manufacturing report check is first step, to see whether proper layer stack is ensured with necessary Cu thickness in each layer. Plurality of vias (Diameter of 0.3mm) may be properly plated, filled with conductive epoxy and cap plated. Electrical check is done to see if any shorting is observed on board. Visual check ensures that pad are proper, surfaces are clear of any grease or foreign particles and ready for assembly process. Based on observations for electrical, visual and manufacturing report check for composite multilayer PCB decision Item-405 can be taken to proceed with next stage of attachment or assembly.
[0050] Item 406, are assembly steps or attachment process, where PCB is cleaned and baked in oven. Solder paste is applied on Pads, and SMT device is placed on the PCB with aid of Pick and place machine. This assembly is passed through an oven with different temperature zones as per profile recommended for attachment. Once done Item-407, is check for assembly, the key step to check if attachment of SMT is suitable for RF and thermal performance. Here visual check of alignment is done, electrical checks are done on PCB pads to see the resistances of device correlates after attachment. Also, X-ray done to see if any air voids are present in assembly or not. As these voids creates localised areas where heat is trapped resulting in poor thermal and RF performance of the assembly. If output of Item-407 is satisfactory then this assembly is ready for attachment with heat sink.
[0051] Item- 410 is inspection check for metal base/ mechanical enclosure or heat sink. Here the material properties, type, plating, surface roughness are examined. Visual check is to ensure absence of any surface burr, grease and smooth finish which aids for optimum attach condition for outcome of Item- 407. Item- 411, is decision on heat sink for attachment and if found satisfactory then proceed with Item- 408, which is attachment of assembly (Output of Item- 407) and heat sink (output of Item- 411) with aid of conductive adhesive. After attachment, checks done for any lump, flow of adhesives (visual checks) shorting, performance checks (electrical checks), IR imaging, thermocouples (thermal checks). If checks are fine then output of Item-409 is satisfactory and we successfully achieve the required performance. Item-412,414 is feedback processes, when outcome of Items-409,407 are not satisfactory. These are again inspected as Item 413,415 and if found satisfactory then steps in Item-408,406 continued, else traced back to Item-401.
[0052] Thus this way we can ensure optimum RF and thermal performance for high power SMT RF device when attached to N-layer composite printed circuit board.
[0053] In an embodiment, as shown in FIGs. 1, 2 and 3, a power MIC is provided. The power MIC includes a power amplifier device (101, 201) mounted on a composite multilayer printed circuit boards (PCBs) (202), wherein the power amplifier device (101, 201) is attached to a first layer of the composite multilayer PCBs (202). The power amplifier device (101, 201) is configured to receive an input RF energy from a driver amplifier (102) to thereby generate a required RF power output for operating an electronic device
[0054] In an exemplary embodiment, the power amplifier device (101, 201) is attached to the first layer of the composite multilayer PCBs (202) using a conductive material (215), the conductive material is one of an epoxy paste or a solder paste.
[0055] In an exemplary embodiment, the power amplifier device (101, 201) is attached to the first layer of the composite multilayer PCBs (202) using a conductive material (215), the conductive material is one of an epoxy paste or a solder paste.
[0056] In an exemplary embodiment, at least the first layer is adapted to realize RF traces and supply and control traces. In another exemplary embodiment, all the layers of composite multilayer PCBs (202) may be adapted to realize RF traces and supply and control traces except the last two layers of the composite multilayer PCBs (202).
[0057] In an exemplary embodiment, the power MIC comprises a controller and sequencer device (110) to monitor an estimate RF level being fed to the power amplifier device (101, 201) and thereby control the input RF energy generated from a driver amplifier (102).
[0058] In an exemplary embodiment, the power MIC comprises a drain pulsing circuit (104) and a gate supply circuit (109) coupled to the controller and sequencer device (110), wherein the drain pulsing circuit (104) and the gate supply circuit (109) adapted to control operations of the power amplifier device (101, 201).
[0059] In an exemplary embodiment, the power MIC comprises one or more charge storage capacitors (105) positioned in near proximity of the power amplifier device (101, 201) for pumping current drawn by the power amplifier device (101, 201) and for preventing noise feedback path in diet current (DC) lines.
[0060] In an exemplary embodiment, the power amplifier device (101, 201) is one of a gallium nitride (GaN) or a gallium arsenide (GaAs) based device using a surface-mount technology (SMT).
[0061] In an exemplary embodiment, the power MIC comprises at least one of temperature sensors, RF detectors, and a protection circuit to monitor and control one or more operations of the the power amplifier device (101, 201).
[0062] In an exemplary embodiment, the power MIC is used as microwave integrated circuits (MIC’s).
[0063] In an embodiment, a method and procedure to employ SMT type high power RF device (typically up to few 100’s of Watts’s peak power) when attached to multi-layer composite PCB (N layer). It consist of a configuration that comprises of: a combination of a surface mount power amplifier, combination of bias and pulsing circuits, Combination of charge storage capacitors, Combination of monitoring and protection circuits, a composite multilayer PCB, each layer designed for optimum RF and thermal performance, a mechanical enclosure or a metal base, and a collection of different adhesives between each interfaces and key process steps, to minutely ensure the inspection and attachment process that are to be followed judiciously with care to guarantee optimum performance and with high probability of first pass success.
[0064] In an exemplary embodiment, the surface mount power amplifier can be GaAs or GaN based. SMT package type with leads available for attachment and a broad metallic patch underneath for efficient heat transfer and optimum RF grounding. RF device can generate typically up to few 100’s of Watts’s peak power, or 10’s of Watts’s of CW (Average) power.
[0065] In an exemplary embodiment, the both Gate and Drain pulsing approaches can be incorporated to ensure the device is ON only when required, and OFF when not operational for better thermal management.
[0066] In an exemplary embodiment, the Pulsing circuit for Gate is combination of high speed analog switches and strategically chosen combinations of capacitors.
[0067] In an exemplary embodiment, the Pulsing circuit for Drain is combination of high speed MOSFET drivers and a low ON resistance (RDS) P-Ch. MOSFET’s.
[0068] In an exemplary embodiment, the Pulsing circuits are placed close to amplifier, for fast pulsing operations.
[0069] In an exemplary embodiment, the charge storage capacitors are distributed strategically and placed closed to power amplifier. Placement of high value charge storage capacitors (in uF range) in combination with other low value capacitors (in nF and pF range) close to power amplifier, for pumping current drawn by PA and for preventing any noise feedback path in DC lines. Tantalum based capacitor having low Effective Series Resistance (ESR) is used for high value charge storage capacitors. Ceramic capacitors with necessary rating used for low value capacitors.
[0070] In an exemplary embodiment, the combination of monitoring and protection circuit which comprises of temperature sensors located in close vicinity of PA, RF detectors to sense sampled RF power, protection circuit to sense gate lines, controller and sequencer (microcontroller or FPGA).
[0071] In an exemplary embodiment, the composite multilayer printed circuit board (N-layer) which is designed and manufactured in a fashion to aids for better RF and thermal performance management. It is formed by combination of substrates suitable for RF designs and substrates that are economical and suited for lower frequency designs.
[0072] For a N multilayer composite board, Layer 1, 3, . . . N-2 is only employed for designs. Layers 2, N-1and N are realized as complete Cu layers devoid of any routing. There can be additional layers with complete Cu layers devoid of any routing if RF traces realized in inner layers. Plurality of these layers helps aiding in better RF grounding and thermal management.
[0073] In an exemplary embodiment, the optimum RF reference grounding and efficient thermal management is achieved by plurality of plated through holes (thermal vias). These thermal vias are filled with conductive paste and cap plated.
[0074] In an exemplary embodiment, the Power patches and dedicated power planes for high currents with minimum ohmic losses and edge plating of PCB to provide common ground reference at the interface
[0075] In an exemplary embodiment, a mechanical enclosure or a metal base with high thermal conductivity and with minimum surface roughness.
[0076] In an exemplary embodiment, different adhesives that are used at various interfaces. Surface mount PA is attached to layer1 of composite multilayer PCB using solder paste of conductive epoxy. Multilayer composite PCB is formed using pre-pregs (adhesives) that is having thermal conductivity and dielectric constant similar to the substrates chosen. Conductive epoxy with good thermal and electrical conductivity used as adhesive between composite multilayer PCB and mechanical enclosure or a metal base.
[0077] In an exemplary embodiment, key process steps to ensure proper attachment of SMT high power RF device on a composite multilayer PCB and in-turn attach of this assembly onto a metal base. Key process steps involved are: inspection (visual and electrical checks) of SMT high power RF device, inspection (visual, electrical and composition checks) of N layer composite PCB, attachment inspection, and inspection (visual, material properties) of metal base (heat sink). Finally attachment inspection for better RF and thermal performance.
[0078] The novel aspects of the present invention are:
• Surface mount high power RF device
• Composite multilayer printed circuit board designs.
• RF routing realized in Layer 1 and in certain inner layers where GND layers are immediately above and below it.
• Layer with RF designs having immediate proximity layer realized as reference GND layers
• Supply and control lines distributed in all layers except in dedicated copper GND layers,
• Power planes in inner layers for high current signals
• Distribution of plurality of PTH holes (Thermal via’s)
• Layer N & N-1 being complete copper layers devoid of live signals,
• Protection mechanism by sensing temperature at close proximity to high power device
• Charge storage capacitors distributed and laid at close proximity to high power RF device
• Protection by sensing negative supply for gate before feeding positive supply to drain.
• Pulsing circuits are placed closed to High power RF devices.
[0079] Although the system has been elaborated as above to include all the main modules, it is completely possible that actual implementations may include only a part of the modules or a combination of those or a division of those into sub-modules in various combinations across multiple devices that can be operatively coupled with each other, including in the cloud. Further the modules can be configured in any sequence to achieve objectives elaborated. Also, it can be appreciated that system can be configured in a computing device or across a plurality of computing devices operatively connected with each other, wherein the computing devices can be any of a computer, a laptop, a smartphone, an Internet enabled mobile device and the like. All such modifications and embodiments are completely within the scope of the present disclosure.
[0080] As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other or in contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously. Within the context of this document terms “coupled to” and “coupled with” are also used euphemistically to mean “communicatively coupled with” over a network, where two or more devices are able to exchange data with each other over the network, possibly via one or more intermediary device.
[0081] Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C ….and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.
[0082] While some embodiments of the present disclosure have been illustrated and described, those are completely exemplary in nature. The disclosure is not limited to the embodiments as elaborated herein only and it would be apparent to those skilled in the art that numerous modifications besides those already described are possible without departing from the inventive concepts herein. All such modifications, changes, variations, substitutions, and equivalents are completely within the scope of the present disclosure. The inventive subject matter, therefore, is not to be restricted except in the protection scope of the appended claims.