Ignition Control Module Heat Sink Question

[George7941]

The Ignition Control Module failed for a second time on my truck. First time was in 2011, so the replacement genuine GM ICM lasted fifteen years. After the first failure, I bought a spare module and left in in my glove box. This time, when the module failed, I recognised the symptoms, changed the module in the Home Depot parking lot and was on my way without a tow and not missing a day of work.
I bought a cheap ICM off Amazon to keep as a spare. I tested it and it runs my engine

https://www.amazon.ca/dp/B0C4TSLHR1

The mounting surface of this module is not flat as on the GM module, but has a recessed portion. I filled up the recess with thermal paste and bolted the module to a spare heat sink and left it in my glove box in case the ICM fails again.
I was wondering why the recess.

 

[Trav]

Use this on the recessed portion.

https://a.co/d/02N6HsAl

 

[grasscutter]

This is the stuff I used on my ICM :

https://www.amazon.com/dp/B019MSVEBY?ref=ppx_yo2ov_dt_b_fed_asin_title

 

[George7941]

I used something similar

This can is about forty years old . I don't think they deteriorate with age.

 

[Lubener]

This is the stuff I used on my ICM :

https://www.amazon.com/dp/B019MSVEBY?ref=ppx_yo2ov_dt_b_fed_asin_title

Won't do a thing in his case if the recessed heat pad isn't contacting the heat sink.