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geekhack Community => Keyboards => Topic started by: maroder on Fri, 04 September 2015, 12:49:03

Title: Plastic layer between PCB and case?
Post by: maroder on Fri, 04 September 2015, 12:49:03
Hi,

I just received my second aluminium CNC case. There is a thin piece of plastic inlay in the case, I guess to protect the PCB from the aluminium seatings. I much would prefer to remove the plastic and seat the PCB directly onto the CNC aluminium, as the keyboard would then sit completely flush within the case.

Will this harm the PCB or is the plastic just a precaution for installation?
Anyone got an idea?
Title: Re: Plastic layer between PCB and case?
Post by: Parak on Fri, 04 September 2015, 12:51:04
Aluminum is conductive. Any exposed point on the PCB that comes into contact with it will be shorted with other contact points. This is a bad.
Title: Re: Plastic layer between PCB and case?
Post by: jbondeson on Fri, 04 September 2015, 12:54:44
You could also put a thin non-conductive (plastic) washer between the standoffs and the pcb.

Out of curiosity, what case is this?
Title: Re: Plastic layer between PCB and case?
Post by: ika on Fri, 04 September 2015, 12:56:55
Aluminum is conductive. Any exposed point on the PCB that comes into contact with it will be shorted with other contact points. This is a bad.

Regular anodized aluminum should not be conductive, although conductive anodizing exists. Check with a multimeter first.
Title: Re: Plastic layer between PCB and case?
Post by: heedpantsnow on Fri, 04 September 2015, 13:05:33
I always put something in my alu keyboard cases.  Always.  A piece of foam shelf liner, Tyvek, or the really thin foam bags that LCD's come wrapped in.  Why take the risk?  Sure, some anodizing is non-conductive, but your solder joints can/frequently do scratch through.
Title: Re: Plastic layer between PCB and case?
Post by: platypus on Fri, 04 September 2015, 13:35:20
+1 for drawer liner, if you don't have any laying around, you can get it on amazon, or at a dollarama, target, walmart, home depot, etc.

It also reduces "ping" and resonance similar to placing your keyboard on a mat.
Title: Re: Plastic layer between PCB and case?
Post by: maroder on Fri, 04 September 2015, 14:08:24
Thanks for the replies. Its a Pexon CNC case. I will just put some drawer liner in between.
Title: Re: Plastic layer between PCB and case?
Post by: jd29 on Fri, 04 September 2015, 14:59:03
How about some short standoffs? I don't know if you want the PCB as low as possible, or dislike the plastic for some other reason.

The highest contact points on your PCB are probably the switch pins, so I doubt setting it on the aluminum would destroy anything but your keyboard definitely won't work.