Gentron Corporation

Lance R. Kaufman

John A Dombeck

Lance R Kaufman

Richard F Schmerda

Herbert O Frederickson

An electric circuit assembly and method provides direct bonding of a copper lead frame pattern (430) on a ceramic substrate (402), including the provision of numerous isolated lead frame segments of small size, without requiring individual oxidation nor placement of same on the substrate, and eliminating loss of alignment during fusing during direct bonding. The lead frame pattern (430) includes a plurality of lead frames (432) interconnected and held together by support bridges (434) therebetween. The support bridges (434) are designed to vaporize, open, retract and disappear during the direct bonding operation, resulting in direct bonded fusion of the copper lead frames (432) to the ceramic substrate (402), and eliminating any remnant of the support bridges (434).

Method of making a circuit assembly

A current sense circuit (100) includes a semiconductor power switch such as a MOSFET (102) having a source metallization contact pad (14) with a conductor jumper bond wire (106) directly connected thereto in the MOSFET module housing (104), which bond wire is connected to a source terminal lead frame within the module, which lead frame extends externally of the module for connection to a load (22) and load voltage (24). The current sense circuitry includes amplifier circuitry (150, 168) having first and second inputs (122, 124) connected to the source bond wire (106) at spaced points (126, 128) along the bond wire within the module housing (104) without insertion of additional series shunt resistance in the bond wire (106) between such points (126, 128), and sensing current flow through the bond wire (106) by sensing voltage between such points (126, 128) and amplifying such voltage. A comparator (218) compares the amplified voltage against a reference voltage (226) and generates an output signal ( 232) when the amplified voltage exceeds the reference voltage by a given amount. The output signal disables gate drive to the MOSFET. The speed of the gate drive signal is improved by providing a separate gate return jumper bond wire to the MOSFET source. Another comparator (242) compares thermistor (238) voltage, measuring MOSFET temperature, against a reference voltage (246) and generates an output signal (260) which disables gate drive to the MOSFET when the latter's temperature exceeds a given level, to provide overtemperature protection in combination with overcurrent protection.

Current sense circuit

In an electric circuit assembly (2) having conductive lead frames (8-10) directly bonded to an insulating substrate (6) by a eutectic, the lead frames are further subjected to a work hardening step (32, 34) to stiffen the lead frames and enable push-on fastener connection (12) to the lead frames without collapse thereof.

Growing community of inventors

Glendale, WI, United States of America

John A Dombeck