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 serves as a transistor driver. It drives the base directly, acting as a current source. These are no externally-visible passives to indicate that the base current can be adjusted, so drive current would seem to be fixed internally on the die. Additionally, it looks to have the capacity to drive up to 8 transistors. In the application in which it was taken from, it was driving the bases of high-current Darlington-pair transistors which switch the primary sides of ignition coils.

Label (top):

[Bosch Logo]
30 237
DW/1296
BJ611.1

Decap Steps:
Grind bottom side of package with 60 & 240 grit sandpaper until die is exposed
Grind top side of package until ~0.5mm remains above die
Use precision diagonal cutters to fracture remaining packaging off of die
Use CA glue to bond die to glass slide (the "glob top" material is still present at this stage)
Use optical swabs and IPA to scrub "glob top" coating off
Rinse with IPA
Clean with fine polishing cloth and IPA
Polish with fine polishing cloth and 0.5 micron polycrystalline diamond suspension

Capture Details:
Imaging device: Keyence VHX-2000
Magnification: 500X

Markings:
[Bosch Logo]
CK07 (likely a reference to the commercial PN used by Bosch)
[Butterfly emblem]

Imaged using normal / center lighting:

Note: This is a ~4X downsampled version of the original image. A full resolution version (11MB) can be provided. On the to-do list…

Imaged using edge lighting, for enhanced shadow contrast:

Note: This is a ~4X downsampled version of the original image. A full resolution version (17MB) can be provided. On the to-do list…