Victor,
Besides a washer, you also need to specify a torque. If the fastening operator happened to be the body building champion of the company, wanting to make sure the screw won't ever come out, this is what you end up with.
Cheers,
Ioan
-----Message d'origine-----
De : TechNet [mailto:[log in to unmask]] De la part de Robert Kondner
Envoyé : August 17, 2018 11:39 AM
À : [log in to unmask]
Objet : Re: [TN] PWB PTH mounting Hole Damage
Hi,
Holy Cow, No flat washerin the world is going to help here. When you tighten that screw the washer will tilt and only the very edge of the PCB "Hole" (I barely call it that) will provide support. If it is well tightened the washer will ben, PCB edges with crunch and the screw will bend. If you get it tight it will not stay tight as the PCB material is failing and it will crush causing the screw to become loose.
You need something under the washer so the the washer can come down flat. It might have seemed like a neat idea when it was designed but it does not look so hot now.
Bob K.
-----Original Message-----
From: TechNet <[log in to unmask]> On Behalf Of Steve Gregory
Sent: Friday, August 17, 2018 11:17 AM
To: [log in to unmask]
Subject: Re: [TN] PWB PTH mounting Hole Damage
Hi Victor,
That's a pretty iffy looking mounting hole, and to tell you the truth, that kind of damage doesn't surprise me. There was a flat washer beneath that screwhead wasn't there?
http://stevezeva.homestead.com/PTH_Diameter_vx_Screw_Head_Overlap.pptx
Steve
On Fri, Aug 17, 2018 at 8:54 AM, <[log in to unmask]> wrote:
> Fellow TechNetters:
>
> I am searching for hardware mounting selection guidelines for the
> purpose of avoiding future damage to PWB PTH external copper pad by
> retaining screw head.
>
> Example pics and current dimensions have been sent to Steve Gregory,
> [log in to unmask]<mailto:[log in to unmask]>
>
>
>
> Givens:
>
> - PWB PTH Slot Diameter, 138.450 mm
>
> - Screw Head Diameter, 159.640 mm
>
> - Screw Shank Diameter, 87.740 mm
>
> - Potential mating overlap, 21.190 mm
>
>
>
> Victor,
>
--
Steve Gregory
Kimco Design and Manufacturing
Process Engineer
(208) 322-0500 Ext. -3133
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