[SUNNY_physics]

Hello. I am a student working on a condensed matter physics project. I am wondering about the nature of the interactions at the interface between inorganic semiconductors and polymers, and if there was a non-mechanical way to disrupt the interactions between the semiconductor and the polymer.

I'm personally baffled by how hard it is to remove semiconductors from polymer packaging without damaging it. I need remove a fragile semiconductor device from the silicone packaging in which it is embedded. I am guessing that there should be very weak interactions between the semiconductor surface and the silicone because a thin inert oxide layer should form on the surface of silicon, and silicon dioxide should have an unfavorable interaction with silicone polymer. Of course the reality is that the silicone sticks onto the device.

I do not think heating would work, as silicones decompose into silicon dioxide on heating and that may destroy surface features on the device. I've tried to disrupt the mechanical stability of the polymer film by swelling it with a solvent mix of toluene and acetone, which should increase the stress in the surface layer until it breaks, but it seems to have very little effect.

Any contribution would be welcome, on either the basic science or the specific problem I'm having. Thank you!

[jaspevacek]

Scientific answer: The four primary causes of adhesion are 1) mechanical interlocking (i.e., Velcro), 2) electric attraction (static electricity) 3) interdiffusion (heat-sealed plastics) and most importantly in your case 4) van der Waals interactions, which dominate when the two materials are in intimate contact.

The swelling approach is a good one, but the choice of solvents will depend on what the packaging material is. All plastics are not the same and different solvents are needed for each. Unfortunately, in some cases, solvent alone is not enough and heat will be needed too.

Nonscientific answer: Contact the supplier and ask them how to get their stupid packaging apart. Tell them that there are lots of good packaging engineers in need a job that could help with this problem and avoid upsetting their customers.

[SUNNY_physics]

Scientific answer: The four primary causes of adhesion are 1) mechanical interlocking (i.e., Velcro), 2) electric attraction (static electricity) 3) interdiffusion (heat-sealed plastics) and most importantly in your case 4) van der Waals interactions, which dominate when the two materials are in intimate contact.

The swelling approach is a good one, but the choice of solvents will depend on what the packaging material is. All plastics are not the same and different solvents are needed for each. Unfortunately, in some cases, solvent alone is not enough and heat will be needed too.

Nonscientific answer: Contact the supplier and ask them how to get their stupid packaging apart. Tell them that there are lots of good packaging engineers in need a job that could help with this problem and avoid upsetting their customers.

thank you... the problem is I cannot contact the supplier because this is actually due to an error on my part... heh...

i need total removal of the plastic (it is silicone) which is tough because its apparently inert to nearly every reagent that doesn't also destroy silicon and is amazingly flexible so it can take alot of mechanical stress (swelling doesn't work to break it the way it does for other thin films).

what i was thinking was adding some crosslinker and heating it to harden and enbrittle it, then swell it with solvent, but this might destroy the component if it goes wrong.

[jaspevacek]

Most silicones will swell quite readily in toluene. You local (big box) hardware store should have some if you want it quickly and cheaply.  Make sure you have good ventiliation, and do not heat it however, as it is quite flammable.

[billnotgatez]

Sometimes paint stores have tolulene, xylene, and/or acetone
whereas some of the big boxes do not

[SUNNY_physics]

Most silicones will swell quite readily in toluene. You local (big box) hardware store should have some if you want it quickly and cheaply.  Make sure you have good ventiliation, and do not heat it however, as it is quite flammable.

OK, I've tried what you did, and it doesn't work. The reason is because this silicone film is not continuous, instead it is just very small bits of leftover silicone millimeters in diameter, and I need it to be completely off, but can't.

When I put it in toluene for 3 days, nothing happened because I suspect that as it swelled, it didn't get mechanically stressed like brittle thin films would, but rather spread out on the silicon.

[jaspevacek]

Did the toluene-soaked silicone swell at all  - turn Jello-like? It should have, and if it did, it should have been easier to pick/scrape it off the surface, regardless of its size.

A question that probably should have been asked earlier: how do you know the packaging is silicone?

[SUNNY_physics]

I just bought a new component.

I know it's silicone because I dipped the entire thing in silicone =) it was part of a new process that I was testing but it went horribly wrong.