Is the edge distance value correct for no circuitry?

Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Sunday, March 01, 2015 8:07 PM
To: [log in to unmask]
Subject: Re: [TN] Required Confromal Coating of Edges of PCB's

Rich,
MIL-I-46058 is simply a materials qualification document. It does not address the coating of board edges. I would disagree with Graham and I do not believe that conformal coating edges of boards is a value added process. Most boards in high performance electronics have routed edges.
The routing process tends to smear the resin over the glass reinforcement, sealing the edges. And since most design standards do not allow internal circuitry closer than 25 mils from the edge of the boards, water or external contaminants would have to penetrate 25 mils of epoxy resin to get to circuitry. If the edges of the boards were sheared or snapped, where the resin did not seal the ends, then perhaps the sealing would be justified. I can say that Rockwell has coated some board edges and left other edges free. We have no field failure, ever, that can be traced to lack of coating the board edges.


Doug Pauls
Principal Materials and Process Engineer Rockwell Collins

On Fri, Feb 27, 2015 at 10:51 AM, Richard Kraszewski < [log in to unmask]> wrote:

> Does anyone recall which MIL document calls out the requirement to
> cover the PCB edges of assemblies?
> I have been led to believe that one exists but that more than likely
> it is not MIL-I-46058C.
>
> Any thoughts??
>
> Rich Kraszewski
> Plexus
>
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