Hello and hello and hello to everyone out there, this is likely the last blog post in the infamous 2025. Today I am going to talk a bit about a recent decapping experiment, where another fun liquid was used.

So there is this fun substance named dimethyl sulphoxide, also known as DMSO, which is supposedly useful in decapping plastic (well, epoxy-based) IC packages. Until recently, though, I have not heard of anyone actually having success using it. A couple days ago I happened upon a couple forum posts claiming success, so in the spirit of science I set out to replicate their findings.

Here is my test subject.

A DIP package of a brown-ish colour

The subject was placed in a test tube, then immersed in DMSO. Then, heat was applied using a hot air station.

Slightly boiling test subject

Noteworthy, my DMSO appears to be water-logged; the liquid started to boil rather vigorously and at a lower than expected temperature. After some time, however, water seem to have evaporated enough and the temperature rose. I detected this by noticing that I don’t have to remove the heat gun all the time to prevent the contents shooting out.

Normally boiling test subject

After some time, around 10-15 min, the package started to visibly disintegrate…

Kinda disintegrating test subject

…and further boiling led to the package falling apart.

Test subject visibly in pieces

The contents was then dumped into a beaker and diluted with some deionised water. The die, which happened to be quite small, can be found among the debris.

Glorious remains

Notably, a particular smell was detected evolving from the solution, kind of like a cabbage soup. Not particularly pleasant, but not overtly offensive either. As a precaution, it is recommended to work in a fume hood or outdoors at least for the final steps where liquid is allowed to fume.

Thoughts

Undeniably, there is truth to the anecdotal evidence of DMSO being effective as a decapping medium. That said, the package used as a test subject was not glass-filled, unlike the vast majority of stuff made after the 1960s outside the Soviets. It is currently not known whether reported failures could be attributed to a difference in epoxy composition or the precense of filling material. In the absence of a way to analyse chemical composition of the materials involved, it is hard to draw any sound conclusions for other packages.

Please get in touch and share your own experience using DMSO. I will be happy to amend the post with new information.

Wish you all merry festivities and hope the next year will be better for all of us.

/DJ