PIC18 MCU Teardown: Examining 40-Pin DIP

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Discussion Overview

The discussion revolves around methods for safely opening a burnt-out PIC18 40-pin DIP microcontroller to examine its internals. Participants explore various techniques for decapsulation, including the use of tools and chemicals, while considering safety precautions and the potential for damaging the chip.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the best method to open the chip without damaging it, expressing a desire to inspect the internals before recycling.
  • Another participant suggests using nitric acid for decapsulation but warns that it requires safety equipment and expertise.
  • Several participants propose using diagonal cutters (dykes) to cut off the top part of the chip, emphasizing the need for caution to avoid injury.
  • Some participants mention the possibility of finding internal images online as an alternative to physically opening the chip.
  • One participant suggests using a sander to grind off the casing, while another recommends using a vise to fracture the IC at the lead frame plane.
  • A participant shares their experience of successfully removing the bottom half of a 14-pin DIP, exposing the lead frame, but questions how to preferentially pop off the top half to access the IC.
  • Another participant recounts their attempt to open a chip using a drill and sandpaper, expressing concern about potentially damaging the IC in the process.
  • There is a discussion about whether a torch could be used to melt off the plastic casing without harming the IC, with differing opinions on the appearance of the lead frame and IC.

Areas of Agreement / Disagreement

Participants generally agree on the need for safety precautions when attempting to open the chip, but there are multiple competing views on the best method to do so without causing damage. The discussion remains unresolved regarding the effectiveness and safety of various techniques proposed.

Contextual Notes

Participants express uncertainty about the condition of the IC after various attempts to open the chip, highlighting the potential for damage during the process. There are also unresolved questions about the best practices for decapsulation and the implications of using different tools or methods.

Lancelot59
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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.
 
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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!
 
Topher925 said:
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.
 
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).
 
berkeman said:
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 said:
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?
 
Lancelot59 said:
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...)
 
berkeman said:
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.
 
  • #10
berkeman said:
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.
 
  • #11
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...
 
  • #12
berkeman said:
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.
 
  • #13
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?
 

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  • #14
Very nice!
 
  • #15
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?
 
  • #16
Lancelot59 said:
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?
 
  • #17
berkeman said:
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?
 

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