Patent GB-1463925-A (GB)
Title: Radio frequency power amplifier constructed as hybrid micro electronic unit
IPC: H05K1/03
Filed: 1975-06-17
Abstract: 1463925 Printed circuit component assemblies MOTOROLA Inc 17 June 1975 [5 Aug 1974] 25795/75 Heading H1R A hybrid microelectronic power amplifier comprises a flat ceramic substrate with a conducting coating on one side and a predetermined conductor pattern on the other side comprising plural portions; connection between a conductor portion and the coating, terminals connected to plural conductor portions applying inputs thereto and deriving outputs therefrom; a semi-conductor die and electrodes secured to a conductor portion with the electrodes connected to other distinct conductor portions one of which is shaped to form an inductor and a conducting housing for the substrate which has a portion supporting the conducting coating and making an electrical ground thereto; the housing serving to conduct heat away from the substrate. The rectangular ceramic substrate 10 (Figs. 1, 3) is conductively coated at 12 on its underside, with conducting portions 14 on its upper side to which electronic components are connected. It is enclosed in a conductive housing 16 on a base 18 having a raised central portion 19 supporting the substrate and connecting to the coating 12 thereon. The base and walls of the housing 18, 20, 21, 22 form a heat sink, while an insulant closure 23 fitting into slots 24 of side walls 21, 22 carries terminals 26, 27, 28 connected to conductors 14. A conducting closure plate 29 is soldered into recesses of walls 20, 21, 22 and retains the closure 23. The amplifier module is supported on chassis 11 whose sockets 13 receive connecting pins 26, 27, 28 while openings 15 of walls 21, 22 receive conducting pins 17 of the chassis for ground connection and heat conduction. Housing wall 22 is recessed at 25 for an interconnecting clip 37 to an adjacent module. The power amplifier (Fig. 4, not shown) is constructed (Fig. 5) on the substrate with input terminal 26 connected to monolithic chip capacitor 30 and monolithic chip capacitor 31, grounded to conductor 55 connected over via holes to the underlying coating 12. The join of the capacitors is connected over strip coating 65 to spiral coating 60 forming an inductor having a loop portion 66 with plural tuning strips bridged thereacross and removable, e.g. by laser cutting to adjust the inductive value. A grounded chip capacitor 32 is connected to the free end of the inductor and the join is connected over strip conductor 68 to further inductor 72 comprising severable tuning bridges 74, 75; which in turn connects over conductor 77 to grounded output resistor 35. A transistor die 82 is base connected to resistor 35 over strip conductor 70 to resistor 35, its collector electrode to conductor 80, and its emitter to ground 58 over conductors 86. A chip inductor choke 88 is connected between conductor 80 and positive supply strip conductor 90 returned to terminal 27, and the choke may be shunted by resistor 39 and grounded over chip capacitor 40. The output at the collector is applied to air wound coil 93 and is grounded over chip capacitor 41, while the free end of the coil is connected over conductor 92, bridged S-shaped conductor 95 with removable tuning bridges 96, 97, and conductor 94 to grounded chip capacitor 42; the output thereacross being connected over further coil 100 in series with bridged S-shaped indicator 105 whose bridge 106 is removable for tuning. The free end of the combined inductor is grounded over chip capacitor 43 and coupled over chip capacitor 47 to output terminal 28 shunted by resistor 48. Conductor 80 is connected over conductors 110, 112, and chip capacitor 50 to conductor 114, resistor 51, and a portion of inductor 72 to the base of transistor 82 to provide negative feedback. In fabrication, the transistor is gold flashed and electrically cemented to the gold plated conductor 80; the chip capacitors and inductors; the air coils, resistors and tuning bridges are simultaneously soldered in position, and the substrate is mounted on the base 18 of the heat sink housing 16 at lower temperature. The module is then tested and tuned by selectively cutting out bridging conductors, e.g. by laser beam.