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We made some 6 layers PCB boards (4.5" x 4.5") recently. But we have concerns about the quality. When pressing/bending/twisting the boards with very small force by hands, we can hear very obvious sound from inside of the boards, like the sound from potato chips. I checked some other PCB board at hand, some of them also have this kind of sound when twisting it.But they are very slightly, I have to put the boards very close to my ears to hear the sound. Does anyone know if that sound is the sign of poor in quality? Thanks in advance.

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    \$\begingroup\$ After bending / twisting / pressing do they still work? \$\endgroup\$ – Tyler Jul 31 '17 at 19:48
  • \$\begingroup\$ Yes, they still work. \$\endgroup\$ – Cindy Jul 31 '17 at 19:53
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    \$\begingroup\$ Unless your PCBs come with a specification describing how much pressing, bending & twisting they're supposed to be able to handle, It's probably safest to assume that they should be handled & mounted such that they aren't subjected to these forces. Most rigid PCBs aren't intended to be flexed - that's what flex PCBs are for ... \$\endgroup\$ – brhans Jul 31 '17 at 20:04
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    \$\begingroup\$ I didn't describe the issue clearly. I realized sound issue when I was installing this board to another board. There are some board to board connectors used to connect two boards. I just gave some pressure to push the board in and the sound is very obviously. We don't have this issue(may be not a issue) from our older version boards. This time we chose a different manufacture because of the low price. @brhans \$\endgroup\$ – Cindy Jul 31 '17 at 20:17
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    \$\begingroup\$ Do the bare boards do that or only after they have been populated? \$\endgroup\$ – Spehro Pefhany Jul 31 '17 at 21:05
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Most decent PCB manufacturing places will provide a cutaway of the PCB encased in epoxy, check for layer separation or copper separation. If you're not flexing these PCB's by a few degrees or putting a lot of pressure on them then they could be manufactured wrong. You get what you pay for.

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  • \$\begingroup\$ Thank you. Do you mean the sound is because there is no cutaway of the PCB encased in epoxy? Do you know if this would cause any potential problems? We still have some unpopulated boards, I am thinking should I populate them or not. \$\endgroup\$ – Cindy Jul 31 '17 at 21:10
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    \$\begingroup\$ No, you can inspect the quality of the PCB with a cutaway and a microscope. \$\endgroup\$ – laptop2d Jul 31 '17 at 21:10

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