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Old 27th November 2009, 09:04 PM   #1
KT is offline KT  United States
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Default How to unbend circuit boards?

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
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Old 27th November 2009, 09:07 PM   #2
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What's it made of? Maybe bake it.
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Old 27th November 2009, 09:33 PM   #3
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Quote:
Originally Posted by KT View Post
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.
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Old 27th November 2009, 09:36 PM   #4
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If it's glass fibre it will need heat , time and to bent slightly in the opposite direction as advised above.
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Old 29th November 2009, 02:06 AM   #5
KT is offline KT  United States
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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
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Old 30th November 2009, 11:50 AM   #6
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I would estimate around 60 Deg C.
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Old 30th November 2009, 12:57 PM   #7
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You can bend them cold also. I have done that.
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Old 30th November 2009, 03:23 PM   #8
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I've always found they tend to return to bent again if heat isn't used. Suppose materials vary.
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Old 1st December 2009, 12:53 AM   #9
Pingrs is offline Pingrs  United Kingdom
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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.

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Old 1st December 2009, 09:33 PM   #10
KT is offline KT  United States
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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
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