Fault Finding - temperature dependant fault.

[steve]

Repairing production failures of pcbs.
Description - PIC controls relays. At switch on, PIC software
initialzes relays and monitors, if on/off.

Passed in the morning.
Failed in the afternoon.

Gently heated board with warm air. - Failed
Cooled down - Pass.

Gently heated different parts of board with warm air - Failed
Cooled down - Pass.

Cant believe its dry joints at this temp.

Ideas?

 

[Don Pearce]

Repairing production failures of pcbs.
Description - PIC controls relays. At switch on, PIC software
initialzes relays and monitors, if on/off.

Passed in the morning.
Failed in the afternoon.

Gently heated board with warm air. - Failed
Cooled down - Pass.

Gently heated different parts of board with warm air - Failed
Cooled down - Pass.

Cant believe its dry joints at this temp.

Ideas?

I'll take on that bet. Get the board warm enough to fail, then use a
freezer spray to locate the part that makes it work again.

d

Pearce Consulting
http://www.pearce.uk.com