# Preparing of large PLCC & TQFP Chips (mechanical)



## JaMora (Dec 15, 2021)

*Introduction*

The reason for this post is because I find *A LOT* of the PLCC and TQFP style chips on automotive computers.
This process could be beneficial, only really for those doing this strictly as a hobby as this requires more prep work (although, I personally can't call this work haha).
For my e-scrap source ($free), I get 95% of electronics from automotive industry (my best friend owns a junk yard).
These chips are almost always Infineon, Motorola, Siemens, Delco, etc.
They are big and ugly as you know, but they have a heart of gold, that of which we love.

For those of you getting e-scrap from a wide range of sources, you would need to be more careful due to the possible differences of internal silicon wafer dimensions based on the wider range of these style chips you'd come across.
As a note of warning, in my experience, one in every one hundred PLCC / TQFP style chips will contain a highly inconsistent or different internal structure.
Although this is uncommon, this method will not work as intended – I always forget to take a picture of those oddballs chips.

As for me, these companies (Ford, GM, BMW, Mopar, etc.) seem to use the same manufacturer sources across the board, for many many years.
Because of this, my e-scrap income is very consistent .
This process is great to minimize the mass of these common large automotive chips before further processing.

*Purpose:*

Help community minimize the mass of large PLCC and TQFP style chips before incineration, pyrolysis, or other processes to follow prep work.
Method reduces weight up to 1/6th the original weight on average if done correctly
Removes base metal wires, wherein gold bond wires will remain in plastic. Never has a gold bond wire stayed attached in thousands of times doing this process (microscope verified, pictured below)
Further mechanical reduction of chip is possible regarding removal of heatsink and non gold bearing backside.
*Presumptions:*

For those who can’t justify chemically processing those base metal wires.
For those who want to greatly reduce loss of gold bond wires before ever firing the chips (only a small weld point of gold material is leftover on base metal wires, as pictured below).
One must be aware that not all PLCC and TQFP will have exact same internal dimensions (silicon wafer and gold bond wires). 1 out of 100 will be vastly different in my experience.
Cutting too far into the plastic will cause inability to ‘pull’ the base metal wires out during process.
One must know that using this process is not beneficial for ICs containing gold plated base metal wires, although in my experience, I’ve found only 1 in thousands of these style ICs contain gold plated wires – so… probably not a worry.
Yes, some rare chips will have gold on heatsinks. That’s a personal decision if you want to go for it.
*Materials needed:*

Safety Glasses
Dremel with plastic cutting wheel
Small vacuum
Trigger clamps
Quick release vise
Pliers (two)
*Instructions:*

Setup quick release vise in a way to quickly add/remove chips
during the process, you will be slightly cutting into the chip (essentially trimming way more than the exposed base metal wires).

Setup Vacuum to catch dust created from the Dremel cutting wheel.
Place two chips next to each other in vise as pictured.
Before cutting, identify the black indentions (dots, as pictured) – these are on almost every chip (some front, some back). These are used for reference where to cut on each chip.
Before cutting a line, remember not to cut so deep as to cut the internal base metal wires. Don't even cut so deep as to visibly expose the base metal wires. You are simply creating weak points in the chip to use as a break point.
Cut a line across both chips that are next to each other (as pictured), just at the inner sides of dots.
Remove the ICs and spin once to cut another line across so that the chips are now cut on all four sides.
Remove the ICs and grab your pliers, one in each hand.
With pliers in both hands, crack the IC in half while pulling apart in a single motion. This will pull the wires out almost every time. This wont work if you cut to far into the chip and cut the base metal wires. Just remember, you are only creating weak points, to break in a controlled method.
I usually stop here, but I plan to eventually soak in AP to dissolve base metal heatsink and remove the backside of the chip, pictured in last photo.
Like everything, repetition makes this process worthwhile and for me, I was able to master this method after processing about 20 chips. I get about 50 of these large chips per week so they start adding up. Had to figure out how to make these more valuable while I continue studying chemical processes (Still in 'collect and study' phase).

Anyways, this process will reduce the overall weight down to 1/3rd the original. If you want to get real fancy, soak the now ‘trimmed’ chips in AP (for a few weeks) and the back half will come right off since the base metal heat sink will have dissolved away which was once helping to hold the two halves together. This is where you get the weight down to 1/6th the original weight!!!

It’s cool how small you can reduce the size of these without losing gold, at least to a degree that would bother me. But everyone is different. This is only a suggestion of technique.

Been collecting for about two years now. Dropped YouTube ideologies when I found this forum! Re-learning and generating new processes based on new knowledge and safety factors. Thanks forum members!!!!!

P.S. some rare chips will have gold on both front and back sides of silicon chip, although rare, always verify!

Bye!


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## canedane (Jan 2, 2022)

Wow, i am impressed! Good descripsion and good photos, Thank you for share this
Henrik


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