How to unbend circuit boards?

[KT]

Hi,

I purchased some unpopulated circuit boards from a private seller a short time ago. Out of the pair, one got bent in shipping somehow.

It's a curve that doesn't prevent the board from being used, but it's not flat, and I'm afraid I'll put some stress on the board and solder connections when I bolt it to the chassis, and force the board into being flat.

I was wondering if there is a standard way of straightening out the board prior to soldering. It seems like just putting some heavy books on it would held somewhat but won't get it back to a fully flat position.

Any ideas?

Thanks,
KT

 

[Rodeodave]

What's it made of? Maybe bake it.

 

[nigelwright7557]

Hi,

I purchased some unpopulated circuit boards from a private seller a short time ago. Out of the pair, one got bent in shipping somehow.

It's a curve that doesn't prevent the board from being used, but it's not flat, and I'm afraid I'll put some stress on the board and solder connections when I bolt it to the chassis, and force the board into being flat.

I was wondering if there is a standard way of straightening out the board prior to soldering. It seems like just putting some heavy books on it would held somewhat but won't get it back to a fully flat position.

Any ideas?

Thanks,
KT

You need to bend it past midway to get it to bend eventually back to a flat position. You need to be careful just how much weight you use otehrwise you split the copper.

 

[thermal runaway]

If it's glass fibre it will need heat , time and to bent slightly in the opposite direction as advised above.

 

[KT]

Yes, it's a regular green glass fiber circuit board. To be specific, it's one of the Pass Pearl phono amp boards.

How much heat do you suggest?

KT

 

[thermal runaway]

I would estimate around 60 Deg C.

 

[peranders]

You can bend them cold also. I have done that.

 

[thermal runaway]

I've always found they tend to return to bent again if heat isn't used. Suppose materials vary.

 

[Pingrs]

The pcb assembly industry would sandwich FR4 board between two flat plates in an oven at about 120 deg C (around the glass transition temp, Tg) for 4 hours, then switch off and cool down slowly to room temp.

Brian.

 

[KT]

I'll try it with 60 C to begin with. This is pretty moderate, so I don't suppose it would affect the screen printing ink, would it?

Thanks,
KT

 

[DaveG]

I recently flattened an improperly stored software CD. It was smushed in a box in a paper sleeve and had so much warp it would hit the mechanism. Almost 1/8" warp.

I used 2 pieces of glass out of some picture frames, cleaned them well, and set the glass CD sandwich directly on the oven racks, with no additional weight. I prewarmed for an hour on the lowest setting, then took it up to about 200F for 10 minutes and let it cool down for an hour. It took out some of the warp, and did not hurt the silk screen image.

Since it did not appear to hurt anything, and I knew 200F is not really enough, I repeated the same prewarm procedure and took it to 280F, then a long cool down with the oven door closed.
Huge improvment, almost flat, did not hurt the printing and the software installed fine.
Dave

 

[Doomlord_uk]

You can bend them cold also.

By the sound of it that's what happened in the post in the first place, so you'd think so

 

[c2cthomas]

3.2 Bow and Twist Repair