How are capacitors on G4 MDD motherboards attached?

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Level 3

735 points

How are capacitors on G4 MDD motherboards attached?

Hi all,
I noticed, on closing one of my G4 MDDs, that one of the capacitors (C680) near where the power supply 24pin plug plugs into the motherboard was bent. I tried moving it slightly back to the upright position. It promptly popped off entirely!

Looking carefully at the capacitor that popped off and the two near it on the motherboard, it appears that these are all glued onto the motherboard, not soldered.

Does anyone know what kind of glue is used to attach these capacitors to the MDD motherboard? The capacitor itself is fine, never had any issue with frying or overheating. No discoloration on the capacitor.

I don't see much residue of glue on either the underside of the capacitor, or on the motherboard, making me think a small dab of clear electrically conducting glue was used. Would rubber cement do it?

Any tips or ideas would be greatly appreciated.

Thanks!

Ed

PB G4 (1Gb RAM, 10.2.8), Mac OS X (10.4.11), PM G4s (2Gb RAM, OSX Server 10.2.8), PM G5 (8Gb RAM,10.4.11), FCS2, ProTools

Posted on Feb 15, 2010 6:27 AM

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Answer 1

Feb 15, 2010 10:46 AM in response to Ed Mansky

As a handy home fixer, you are not burdened by the need to hold dozens of components still while heating up the entire board to get the tiny dots of solder to melt. You may not need any glue at all, but some of those Videos state you WILL need additional flux, and probably solder-removal braid to clean up any mistakes.

You need only make the electrical connection to the contacts on that capacitor, and you are allowed to use "any method that works". Remember that most electrolytic capacitors have a plus and a minus lead that should be honored.

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Answer 2

Feb 15, 2010 8:24 AM in response to Ed Mansky

Surface Mount components are soldered, but the techniques may be different from what you are used to. In some cases, tacky flux is used to temporarily hold the component in place. A broad general discussion can be found in this wikipedia article on the subject, and several "how to" videos are available on youtube.

http://en.wikipedia.org/wiki/Surface-mount_technology

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Answer 3

Ed Mansky Author

Level 3

735 points

Feb 15, 2010 10:07 AM in response to Grant Bennet-Alder

Thanks for the very helpful Wikipedia link on SMT. I hadn't seen that. I will look at the various how-to videos on soldering. Soldering components attached via SMT is a lot different from the old circuit boards I use to work on in the 70s.

I ran across this Wikipedia entry on Capacitor plague . In it they mention a clear resin used to attach capacitors call Evo Stik .

Apple's motherboard plants may well have used Evo Stik or some other soldering paste to hold the component down while the machine soldered the component.

Ed

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