Poor connection made when flexing the PCB

[looxuser]

I have a situation where the device i'm trying to fix works intermittently and fine when i flex the pcb. If i relax the flex the board starts misbehaving again. I've checked everything under microscope and cannot see any issues. Has anyone every come across broken vias through a board please? Also there a potted IC nearby, same question?

 

[Externet]

I would attach the board edge? to a bench vise, a meter probe to perhaps soldered to its ground and the other probe at many places with one hand while the other hand deforms the board to get near the problem trace or solder. Yes, found open vias.

 

[Harald Kapp]

cannot see any issues.

There may be a hairline crack in a trace. This type of crack is very small and almost invisible.
Also cold solder joints can lead to such a behavior. These also may be hard to detect. Re-soldering any suspect joints often helps.

anyone every come across broken vias through a board

Haven't seen that type of failure, though that doesn't mean it's not possible.

a potted IC nearby, same question?

A bonding wire may break lose within an IC housing, but that would probably be a permanent failure as the housing is stiff compared to the PCB and won't flex much.

 

[Martaine2005]

May also help to put pressure on each component when checking. The dry/cracked joint may show its ugly head sooner.

Martin

 

[Kiwi]

I have used Rapid Freeze on circuit boards looking for intermittent issues like this before. Makes any cracks to open up so they are easier to spot.

 

[narkeleptk]

I have a situation where the device i'm trying to fix works intermittently and fine when i flex the pcb. If i relax the flex the board starts misbehaving again. I've checked everything under microscope and cannot see any issues. Has anyone every come across broken vias through a board please? Also there a potted IC nearby, same question?

I run into this a lot with cluster repair work.
1- Bad joint on something (even if you cant see it under microscope, its there.) Usually the bigger smd components like large resistors or resistor arrays.
2- Cracked trace. Typically where it meats a via or pad and is highly stressed like a connector.

That's about it for the symptoms you describe

 

[looxuser]

I run into this a lot with cluster repair work.
1- Bad joint on something (even if you cant see it under microscope, its there.) Usually the bigger smd components like large resistors or resistor arrays.
2- Cracked trace. Typically where it meats a via or pad and is highly stressed like a connector.

That's about it for the symptoms you describe

many thanks going to solder through the via and see if that fixes it.

 

[kingcrediepcb]

I have a situation where the device i'm trying to fix works intermittently and fine when i flex the pcb. If i relax the flex the board starts misbehaving again. I've checked everything under microscope and cannot see any issues. Has anyone every come across broken vias through a board please? Also there a potted IC nearby, same question?

Hi,

Any updated news about your question? Have you fixed it?

 

[bidrohini]

That means there is a broken trace or via. Here you'll get some troubleshooting guidelines: https://www.mclpcb.com/blog/common-flex-pcb-issues/