This pcb came from a vehicle interior with the board side seen in the attachment facing downwardly with some space below it. It was installed inside the vehicle. The car is about 2 years old.

Any idea what would have caused this corrosion on the transistor leads? The unit is not working and this would appear to be the cause. I cannot tell from visual inspection if any components failed.

Appreciate all the help I can get!

 

It appears to me that something corrosive drained or dripped onto the board and ran down across a few components.
It appears to cover a small area in toto.

 

Agreed on the liquid damage, but it doesn't need to be a corrosive liquid, water will do it as the applied voltage will produce electrolysis and corrode the metal.

 

The white residue suggests water with a non-trivial mineral content. Is there any chance someone spilled some drinking water (from a bottle, etc.) in such a way it could get to the board?

 

The white residue suggests water with a non-trivial mineral content. Is there any chance someone spilled some drinking water (from a bottle, etc.) in such a way it could get to the board?

Or some kind of beer?

 

Or some kind of beer?

Seems like that would be messier!
My comment is based on experience with bottled water into notebook computers, a common problem.

 

Coke, sweat, even condensation caused by the car filling with humid air on a cold part (cooled by the AC).
the white powder is likely tin oxide/hydroxide and the light blue powder is copper oxide/hydroxide. Other white oxides or carbonates may be present depending on the pH and cation.

what is the round component below the transistor? They appears to be a pressure sensor or gas sensor? Also, the blue powder around that indicates the corrosion may be deeper there as it is down to the copper (beyond the tin solder).

 

Thanks for all the comments.

This module is mounted in the center console between the vehicle seats with the side of the pcb facing downwardly so it is not clear how liquid would have gotten onto that side of the pcb from a spill, but that is what I am trying to determine.

Could the corrosion be just from a couple instances of liquid exposure, as opposed to just humidity itself causing it? There is a second same transistor nearby (not shown in the picture) that has the same thing - heavy corrosion on the collector terminals.

That is the real issue I am trying to determine and get input on - was this caused by liquid spills that crept under the center console top and somehow got onto the bottom of the board or would it have to have been some longer term exposure such as from humidity over the course of a couple summers, or something else?

The reason it matters is because the dealer is asserting that it is customer (my) fault and not a warranty item. From my standpoint, I don't recall any instances of spills, but there might have been one or two. If it is my fault then I'm willing to pony up the large sum for the replacement part and labor, although even then I have to wonder about it being essentially a design flaw if a couple of spills could cause that underneath the console top. My problem is that I don't see or have any more evidence of it being my fault than either a manufacturing or design problem. Moreover, before they even looked at it they mentioned that these cars have that problem not infrequently.

- Jim

 

Honestly, it looks like water-on-the-PCB type damage and I would be surprised if humidity could cause it. On the other hand, how water got in to do that is a mystery. Is there any chance it came from under the car? (A leak in rainy conditions and puddles, for example)

 

If water landed on the top side of the board it could have run across and round the edge of the board.

 

Honestly, it looks like water-on-the-PCB type damage and I would be surprised if humidity could cause it. On the other hand, how water got in to do that is a mystery. Is there any chance it came from under the car? (A leak in rainy conditions and puddles, for example)

I don't think outside water could get in there, it is well up into the interior cabin with a solid underbody. The moon roof has never been left open in the elements. I know because the one time I tried to leave it open, just the air moving in and out through the top kept setting of the interior monitoring alarm!

MrSalts:

what is the round component below the transistor?

I don't think it's a sensor, I think it is a rubber seal of some sort - there are several, and this module is just for radio and display screen menu control. And actually, if you look at the first pic I posted, it looks as though that rubber seal is cracked. Maybe that's how the water got in there and is what accounts for all the mineralization around that seal.

I added a couple of pics below. First is the top of the module - a couple coaxial rotary knobs (function switch and volume pot), and a couple of micro-deflection switches. You can see a little water stain on the one switch, but again, how should that be able to get under the module and onto the downward facing side of the circuit board. Certainly possible to wick around the edge, per AlbertHall, but would that be enough in one or two instances to cause that corrosion all by itself?

Second picture is the full underside of the module with the two transistors that have corroded collector terminals.

 

In my opinion, the manufacturer is being sloppy. The entire board should have been protected with conformal coating.

 

In my opinion, the manufacturer is being sloppy. The entire board should have been protected with conformal coating.

Yes, agreed, and exactly what I said to the service rep. But, OEMs and their dealers will never admit to design defects, they will just cover under warranty what they agree is a manufacturing defect.

The rep said he talked to his manager who said that the tech believed it had been exposed to water, which must mean a spill by the customer, and therefore is customer damage and the manufacturer wouldn't approve it if they sent it in for a warranty claim.

Probably my only relief will be either on the basis of "customer relations" or if I get the module from them and can fix it myself.

 

FWIW it looks repairable but you should practice on sacrificial targets before attempting it.

 

Followup - the dealer checked with the OEM who said they don't consider it a manufacturing defect, but would cover the cost of the part and dropped the labor charge down so the total cost to me to a little under half of what they first quoted. Thanks for the assistance!

 

Followup - the dealer checked with the OEM who said they don't consider it a manufacturing defect, but would cover the cost of the part and dropped the labor charge down so the total cost to me to a little under half of what they first quoted. Thanks for the assistance!

Could you see which company made the part? It might be molded into the plastic or silk-screened on the PCB

 

Could you see which company made the part? It might be molded into the plastic or silk-screened on the PCB

I don't have it, but when I pick up the car today I'll see if I can take a look. As I understand it, they're just going to throw the old on out!

 

Worth a try asking if you can have the old one?

 

Worth a try asking if you can have the old one?

I did and the service rep said he would check and give it to me if so. I get the feeling they'd rather not.

 

Unless replaced under warrenty, the item is yours, by rights? .
.