Table of Contents


This part was taken from a Motronic M1.7.3 engine control unit (ECU), which was commonly used on 1.6L & 1.8L 4-cylinder BMWs of the mid-E36 generation. While this chip was likely used on a number of ECUs, the specific one in this case had Bosch PN 0 261 203 661.

Functionally, this chip is a high current low-side switching transistor arranged in a Darlington pair. It is used to charge the ignition coils by providing the primary coil a switched path to ground, with peak primary currents of up to 10A. It also provides flyback clamping at approximately 325V based on oscilloscope measurements. Bosch has made many custom power transistors for this application over the years, and part numbers vary across Motronic units, sometimes even within a single unit! Variants of these are / were also sold commercially with part numbers like BIP373 and BU323Z.


Label (top):

[Bosch Logo]
30051 (Bosch internal PN)


Decap Steps:
(Bic lighter + water quench) x 3 cycles
Selective crushing with pliers and bench vise

Capture Details:
Imaging device: Keyence VHX-2000
Magnification: 50X

(none apparent)

Removing the die from the package proved to be difficult. The bonded wires were very large, due to the high currents being switched, so pulling the encapsulation off caused the wires to take chunks of the die with them. A second transistor was decapsulated, with more heating+quenching cycles, which prevented tear-out. Attempts to remove the polyimide coating smudged the metal layer badly.

felinefriendly/bosch/b30051.txt · Last modified: 2018/07/27 22:30 by e30tuner
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