There are two places where the track pad connects - the logic board (red) arrow and to the track pad PCB (red square)
Image Source: Ifixit.com
If what you're referring to is what's identified by the red square at the bottom of the image above, then it's the PCB. It's not sold as a separate assembly (AFAIK) and you have to replace the entire track pad assembly (PN# 923-00518). If it's the top portion (red arrow), you have to get the logic board repaired/replaced.
It's possible you could buy a salvaged track pad from eBay just to get the PCB, but it's an "unknown." You could end up getting a track pad with a bad PCB again, but if the price is good, it may be worth the gamble.
Finally, if you got a spark when connecting the flex cable, replace the flex cable as well. When you see a spark, that means enough voltage passed through the cable to arc which could have permanently damaged the cable - it's cheap enough that you should just do it anyway and not try to salvage a cable of questionable function.