Hi: The northbridge (Intel 865G) on the motherboard, I took the heatsink away expecting to find silicon grease beneath and found it had a solidified yellow sticky substance on it. I rubbed the surfaces with isopropylic alcohol but it removed nothing. How should I proceed now?

Another solvent...

Put a drop of Acetone on the hardened paste and wait, in order to see if the Acetone will dissolve it. The Acetone may take the paint off the chip, but that shouldn't matter; just don't get it on anything else You can also try Benzene if Acetone doesn't work.

If you can soften but not dissolve the paste, scraping it up starting from the edge of the mass with the sharp edge of a plastic card might help.

Was the heatsink clipped to the chip? If so you'll need to use grease when you re-attach it. If it's not clipped you'll need to stick it. I remember using a two part system when replacing heatsinks on the original Sun E3000/4000 CPU/Memory boards; you put the paste on the chip and painted the activation fluid on the heatsink then held them together for a couple of minutes to set. (The crappy plastic heatsink clips used to break.) Nope! I can't remember a brand name. As mentioned by Thor above, you have to ensure both chip and heatsink are perfectly clean before re-fixing.

Play Bonny!

Hi,

I have used petroleum distillate to remove pads from chips. You can use WD-40 (Trade-name) to remove. Acetone can damage the Motherboard. Another thing that could be used is denatured alcohol but you should use caution when using this. Just be careful not to damage the silk screen or circuit board by lifting traces on the board.

Hope this helps.
Have fun & enjoy!

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Thanks guys! "Was the heatsink clipped to the chip?": yes, by two spring wire fasteners. The chip is 4 x 4 cm with a tower in the center, with a 1 x 1 cm base and 1 mm tall. The flat top of the tower is metallic and here is the glue deposited. But this surface I touched it, and though colored by the glue the finger does not notice roughness. There is kind of a rubber layer on the chip too, outside the tower, to help level the tiny top surface with the rest of the top, under the action of the springs pulling the heatsink downwards, some of it having been removed when I pulled the heatsink away.

How I envy people knowing to say something with few words, but the WD-40 I hope will do its job. It seems a universal remedy to fix the widest class of problems, a sort of panacea.

Hi,

For WD-40, be sure to spray on a rag and not on the board to wipe the surface.

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Hi,

One other note is that you can use a single edge razor blade (plastic/metal) be sure not to scratch the surface. If you do scratch then be sure to use enough compound to fill scratch(s) and so to dissipate to the heat sink.

Thanks onebuck. I'll try to do a fine job.