PIC18 MCU Teardown: Examining 40-Pin DIP

[Lancelot59]

I have a burnt out PIC18. It's a 40 pin DIP. I want to open it up and look around inside of it. What's the best method of getting inside of a chip like this without damaging the internals? I don't plan on putting it back together. I just want to look inside it before I recycle it.

 

[Topher925]

This is normally done with nitric and very good safety equipment. See link for more details,

http://www.sparkfun.com/commerce/news.php?id=384FYI, unless your an experienced chemist or a professional chip take-apart-er I don't recommend you do this!

 

[Lancelot59]

This is normally done with nitric and very good safety equipment. See link for more details,

http://www.sparkfun.com/commerce/news.php?id=384


FYI, unless your an experienced chemist or a professional chip take-apart-er I don't recommend you do this!

Indeed. I don't have the tools and equipment to do that safely. I'm not planning on putting it back together, so it doesn't have to be neat. I just want to take a look inside before I recycle it.

 

[berkeman]

If you have a large pair of dykes (diagonal cutters), you can sometimes cut the top part off just above the lead frame. The dykes should be big enough to get a bite on the end of the DIP so that it is at least half way up the cutting blades. Be careful not to slip and slice yourself, obviously (not that it's ever happened to me).

 

[mdjensen22]

If you have a large pair of dykes (diagonal cutters), you can sometimes cut the top part off just above the lead frame. The dykes should be big enough to get a bite on the end of the DIP so that it is at least half way up the cutting blades. Be careful not to slip and slice yourself, obviously (not that it's ever happened to me).

That's the best way to do it if precision isn't a key (that's how I've done it...)

Through google you can usually find internal images of the parts without the casing if you just want to look. A lot of time somebody has already identified the parts of the die.

 

[berkeman]

Through google you can usually find internal images of the parts without the casing if you just want to look. A lot of time somebody has already identified the parts of the die.

Good idea. The keywords are decapsulation or decapsulated. I did a Google Image search on decapsulated, and got lots of good images:

http://www.google.com/images?hl=en&source=imghp&q=decapsulated&gbv=2&aq=f&aqi=&aql=&oq=&gs_rfai=

.

 

[Lancelot59]

If you have a large pair of dykes (diagonal cutters), you can sometimes cut the top part off just above the lead frame. The dykes should be big enough to get a bite on the end of the DIP so that it is at least half way up the cutting blades. Be careful not to slip and slice yourself, obviously (not that it's ever happened to me).

I don't have that tool unfortunately. Could I grind it off with a sander?

 

[berkeman]

I don't have that tool unfortunately. Could I grind it off with a sander?

You could try the sander, but it won't give you as clean a cut. You might try putting it in a vise, so that as you clamp down with the vise, it fractures the IC at the lead frame plane. (So you put the DIP in with 20 pins touching one jaw of the vise, and the other 20 pins touching the other jaw...)

 

[Lancelot59]

You could try the sander, but it won't give you as clean a cut. You might try putting it in a vise, so that as you clamp down with the vise, it fractures the IC at the lead frame plane. (So you put the DIP in with 20 pins touching one jaw of the vise, and the other 20 pins touching the other jaw...)

That sounds like a much more entertaining method.

 

[Topher925]

You could try the sander, but it won't give you as clean a cut. You might try putting it in a vise, so that as you clamp down with the vise, it fractures the IC at the lead frame plane. (So you put the DIP in with 20 pins touching one jaw of the vise, and the other 20 pins touching the other jaw...)

I may try that just to see if it works. I think I've got a 28-pin DIP lying around somewhere that I can take apart.

 

[berkeman]

Please everybody remember to wear safety glasses if you try this!

I just tried it with a 14-pin DIP, and it worked pretty well. It ended up popping off the bottom half of the plastic, exposing the lead frame from below. Not sure if there's a trick to make it preferentially pop off the top half to expose the IC topside...

 

[Lancelot59]

Please everybody remember to wear safety glasses if you try this!

I just tried it with a 14-pin DIP, and it worked pretty well. It ended up popping off the bottom half of the plastic, exposing the lead frame from below. Not sure if there's a trick to make it preferentially pop off the top half to expose the IC topside...

Oh definitely. Plastic shards in your eyes would ruin your day. I'll give it a try tomorrow. The way I've seen them laid out in pictures leaves a relatively clear line, until you get close to the centre of the chip. I think I could get better results only grinding off one of the ends down to the seam, and then thinning out the rest over the actual IC. Then it's just a matter of prying it off, depending on how much of the plastic is fused together.

 

[Lancelot59]

Well I did it...although I think I destroyed the IC. I didn't have a proper sander available to me, so I just went at it with a sandpaper bit on a drill. A few times the drill got traction and pulled around, which trashed a few pins. Other than that I just had a vacuum next to it to suck up the plastic dust.

Picture is attached. Did I trash the IC? Or can I still get to it?

 

[berkeman]

Very nice!

 

[Lancelot59]

Actually, I think that is just plastic. I'm looking for a way to get it off without destroying the IC. I'm told proper use of a torch should safely melt it off. Can anyone confirm this?

 

[berkeman]

Actually, I think that is just plastic. I'm looking for a way to get it off without destroying the IC. I'm told proper use of a torch should safely melt it off. Can anyone confirm this?

It looks like the lead frame and IC to me. You think the lead frame looks plastic?

 

[Lancelot59]

It looks like the lead frame and IC to me. You think the lead frame looks plastic?

No the little bit in the middle. On closer inspection it appears I ripped off the IC. Look at the leads close to the centre where they converge. They're silver. I doubt they go into the plastic to hook up to the IC. Does anyone have any more info?