How to dissolve FR-4

[victor43]

Hello.

 

I have read that FR-4 substrate is made of fiberglass and epoxy resin and would like to learn on how to dissolve this material ? I have these two chips that appear to be packaged by the same material (FR-4) which I would like to have removed (decapsulate) leaving the die/circuitry intact.

 

 

Any ideas would be appreciated

 

Thanks

 

Victor

[John Cuthber]

It's hard to be certain because there are lots of different epoxy resins.

Quite a lot of them are soluble in 100% formic acid.

If you take this approach please note that your fingers will also be soluble.

 

The glass fibre is more difficult to dissolve and the only obvious contenders are HF or very strong bases which would attack the chip (as well as your fingers). However, once you have washed the resin away the glass fibre can be removed by un weaving it.

 

The other problem is that anything that dissolves the epoxy resin will attack any other plastic packaging of other components present.

 

What are you hoping to achieve here?

[Enthalpy]

Acetone is a known solvent for epoxies, and would harm the chip little, but it will take long! You might warm it, or circulate its vapour as is done in industrial cleaners.

 

Etching would be less slow, yes, but may corrode the chip's thin and exposed contact pads - a copper alloy since you chips seem to be from the Coppermine series, possibly covered with gold.

 

The underside of the package is welded to the motherboard by hundreds of metal balls. Melting them would destroy the mobo.

[victor43]

@Enthalpy: Thanks for the reply. It does not matter to me if the process of decapsulation takes a long time..I'm in no hurry. As to causing damage to the board that is fine as the purpose of the decapsualtion is to examine the die structures.

 

@John Cuthber: Thanks for the reply. As for my fingers being prone to the acid used... my plan is to use gloves which should protect in the case of minor splashes. My goal is to study the die once the chip has been decapsulated. Not for live analysis.

[pcbman]

Acetone is a known solvent for epoxies, and would harm the chip little, but it will take long! You might warm it, or circulate its vapour as is done in industrial cleaners.

 

Etching would be less slow, yes, but may corrode the chip's thin and exposed contact pads - a copper alloy since you chips seem to be from the Coppermine series, possibly covered with gold.

 

The underside of the package is welded to the motherboard by hundreds of metal balls. Melting them would destroy the mobo.

 

 

I was just browsing for relevant posts for my project and I happened to stumble upon yours. Thanks for the useful information!

 

 

 

dave