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Preventing pin and mounting holes from going all the way through the board
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victorsuciu 4 months ago
I'm an electronics noob so sorry if this is a dumb question. I am designing a very simple bipolar EMG probe. It consists of three copper electrodes on the bottom, each wired to a 3.5mm headphone jack on top. I'm planning to connect it to an off-the-shelf EMG amp like the [Grove EMG detector](https://www.seeedstudio.com/Grove-EMG-Detector-p-1737.html) or the [OYMotion Gravity EMG sensor.](https://www.dfrobot.com/product-1661.html) Here's a picture: ![Screen Shot 2023-01-18 at 2.31.48 AM.png](//image.easyeda.com/pullimage/XIBPDxdcPzdno7Jg1wzvdqQA6OzDvU5qHkP4Yq78.png) As you can see, the headphone jack's mounting holes go all the way through the entire board including the electrodes, reducing their contact area. The headphone jack [(PJ-621C)](https://atta.szlcsc.com/upload/public/pdf/source/20211105/FE62175CE755441EFCD415EDEBDCA661.pdf) has extremely tiny pins that do not extend below the component body so I don't see why it needs to penetrate 3 whole layers of fiberglass on this 4-layer board. Is it possible to stop drilling the holes before reaching the bottom layer? Even better, would that be possible on a 2-layer board with only a single sheet of fiberglass? I did find [this post](https://easyeda.com/forum/topic/How_to_create_blind_vias_-lb5ZTbsKE) about vias that said only through-holes were supported and blind vias were not, but that was only about vias and it's a 5-year-old post. Thank you
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andyfierman 4 months ago
"... so I don't see why it needs to penetrate 3 whole layers of fiberglass on this 4-layer board." You can't solder a through hole component to a PCB unless the holes go all the way through the board because you can't solder the pins under the jack socket if they cannot be accessed from the bottom of the board. The simplest solution is to make a 2 layer PCB and use a surface mounted jack socket on the top layer. Then via the connections for the jack socket through to the contact strips on the bottom layer: [https://jlcpcb\.com/partdetail/Korean\_HropartsElec\-PJ\_3937A/C128990](https://jlcpcb.com/partdetail/Korean_HropartsElec-PJ_3937A/C128990)<br> <br> Or just move the jack socket so that it doesn't foul the contact strips. FYI: [https://jlcpcb.com/capabilities/pcb-capabilities](https://jlcpcb.com/capabilities/pcb-capabilities)<br> <br> ![image.png](//image.easyeda.com/pullimage/9PXEFlZ2xuo5W3HyoIkDn2TzxsRCjUpK3oCCHVNa.png) See also: [https://easyeda.com/forum/topic/Z-axis-milling-cee033d76f224535a178051691addb03](https://easyeda.com/forum/topic/Z-axis-milling-cee033d76f224535a178051691addb03) [https://easyeda.com/forum/topic/Pockets-Z-Milling-support-for-regular-PCBs-31e27fe9129b4dd4bb80025bcf8dc737](https://easyeda.com/forum/topic/Pockets-Z-Milling-support-for-regular-PCBs-31e27fe9129b4dd4bb80025bcf8dc737)
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victorsuciu 4 months ago
Thanks! I replaced the headphone jack with one that has only surface mount pins and no mounting holes and it fixed the issue.
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