PCB Markings

[EFLImpudence]

Does anyone know what has caused these dark markings on this PCB?

It is from my van and is the security (anti-theft) system which more and more frequently caused it not to start.
There was dust/rust/sparkly bits - something like that - on the parts in the dark areas. I brushed them off with a tooth brush and have had no trouble starting since.
There is no sign of water ingress on the module or nearby nor any markings on the other side.

 

[bernardgreen]

It definately looks like some fluid has splashed on the board and with it some dissolved material.

How is the board packaged ? Are there any vent holes in the case / box ?

 

[EFLImpudence]

The board is in its own plastic housing fitted behind the dashboard - no vent holes.

 

[sparkymarka]

That left hand IC is well corroded on the upper 2 pins !

 

[EFLImpudence]

They did clean up quite well with the brushing. I didn't think to take another picture.

 

[bernardgreen]

he board is in its own plastic housing fitted behind the dashboard - no vent holes.

Strange then that liquid got in there, I had one failure where an electrolytic on a poere modul PCB boiled, vented and sprayed it's liquid onto another board/

 

[jj4091]

Maybe condensation, but looks like some sort of chemical reaction, perhaps something was spilled on it during assy. & took a while to cause a problem.