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Corrosion due to RTV adhesive

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#53595

Corrosion due to RTV adhesive | 7 February, 2008

We are experiencing corrosion and subsequent pcb contamination from the RTV material used to secure a Power Supply. The degradation takes place over a few weeks. The power supply vendor is balking at liability, our OEM customer is screaming. Anyone heard of this previously? The RTV is not placed by us, but by the power supply manufacturer.

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#53596

Corrosion due to RTV adhesive | 7 February, 2008

We bet your customer has freaked-out. Some common RTV out-gas ammonia during cure. Many types of RTV depend on strong acetic acid to work. Also, ammonia plus water in the air produces ammonium hydroxide, an aggressive alkali. We've talked about this previously. Here's an example from the fine SMTnet Archives http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=33826

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#53600

Corrosion due to RTV adhesive | 8 February, 2008

Hey that was me way back! Anyways, use Dow 3140 (self leveling) or Dow 3145 (peanut butter consistency) and call it a day. No out gassing/acidic properties. 3140 also contains a UV tracer for black light inspection. Any tall caps should be epoxied if you're really looking to strengthen things though. A bead of RTV around the base of a 2" tall cap is just about useless in a vibe environment.

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#53611

Corrosion due to RTV adhesive | 11 February, 2008

3145 is methoxy cure, so the cure by product is methanol.

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