Hole in PCB due to corrosive reaction?

Question

I have an Xbox One controller where the X button did not work anymore. I disassembled it today, to find the reason for this. It turns out, there is a hole in the motherboard near the X button:

There was this sticker right above the hole (it seems that "XJY" is an abbreviation of "Shenzhen Xinjiaye Electronics Technology Co., Ltd.", which is a chinese company that builds such motherboards):

Now to my question: is it possible that the adhesive of the sticker in combination with the flowing electricity on the motherboard has caused a corrosive reaction, resulting in the hole? I think there is no mechanical cause, since the wires in the hole are still largely intact and the "missing" part of the motherboard was not inside the controller.

Answer 1

It's unlikely.

• The hole is very nearly circular, and has smooth edges, indicating the hole was deliberately drilled.

• Somebody has added thin wires to try to repair the damage, indicating the defect was found and "repaired" before the product left the factory.

Most likely the hole is meant for mounting the board into the housing. The damage to the surface layers is a fabrication defect that they tried to fix rather than scrapping the board.

Edit: As pointed out in comments, another possibility is that the hole was drilled deliberately to remove some incorrectly designed wires, and then the added wires you see were added to replace the connections broken by the drill.

Answer 2

Those wires you see aren't the bonded copper traces, which you think are left behind from the corrosion. They are wires added after the fact to correct the broken board. You can tell by the blobs of solder that were manually added, like the blob above the carbon trace that is not perfect (unlike what you see from wave soldering), or the solder added to the trace above that (north west of your red X), which you would never see on a etched board.

Considering that holes are normally drilled after most of the board is done in a typical PCB fabrication, and if it was a one off problem that would have been pitched, this is likely one of MANY boards that look exactly like this. The cost benefit of ditching these and a second run probably exceeded the cost of having these reworked manually. Material is more expensive than labor over there. The source issue was likely fixed before the next batch, but retooling a manufacturing process is also expensive, so who knows.

As to how that happened, speculation but:

• Drill was too big for the material OR
• the wrong bit was mounted OR
• the speed/torque was set wrong, so it chewed up the PCB material OR
• the depth was off so the collet holding the drill bit crushed the board OR
• Questionable material. Material is cheap, Labor is cheaper, but that leads to quality issues.

Answer 3

Corrosion does not make perfectly round holes in PCBs... The edges of the hole kinda look like a crater, soldermask and tracks have been ripped off like someone hacked at it with an x-acto knife.

There are several copper wires soldered across the hole...

This looks like a very "ghetto" botched repair job.

Now, what does the virgin PCB looks like? A bit of internet search and...

There doesn't seem to be anything in the area of the hole that would blow up and then require someone to fix the damage, like a tantalum capacitor. Also, an important detail is that there is no hole on the original board.

So, where does the hole come from?

Now, the edges of the hole are really destroyed. This wasn't done by drilling. It looks like it has exploded.

I'm going to go with the hypothesis that this controller was shot with a .22LR bullet from the back of the board (referring to your photo), then refurbished. Please check if the diameter of the hole is the same as a .22 bullet, I'd really like to know!

Answer 4

It is a reject board that had a hole punched in it before scraping to prevent reuse. However some company (probably in the electronics recycling industry) figured since the boards were basically free the cost of the bare minimum repairs would turn a reasonable profit in the off brand controller market. This happens more often then most people realize. This is why some manufacturers have gone the extra step of punching/drilling holes or a quick saw cut into the reject parts to hopefully prevent another company from offering a comparable product at a lower price. They will already have lost the sale by the time your x button stops working and you realize you saved a few bucks to literally buy remanufactured garbage.

Answer 5

As others have mention - this is not corrosive damage and those wires were put on after the fact to attempt to hide the mistake. As to how the hole actually got there...

You can see that board was assembled before the hole was created. Check the edges of the hole - the solder points are all intact along with some of the underlying board.

If it was broken during manufacturing of the board, the solder wouldn't be nice and perfect like that. Adding those solder points is usually one of the last steps in manufacturing. In fact, it would should have been rejected in QA and not made it to solder flow.

My guess is someone messed up and broke the board during final assembly and this was their attempt to correct the issue by hand. Others have pointed out that this hole isn't on a "typical" xbox one controller board, but you didn't provide information as to the brand to properly verify how it should look.

Did you buy this secondhand? If so, it is also possible that someone took it apart to look at it, messed it up and then tried to cover it up. Though generally if someone does that it's just kind of left there since no one will see it.