If correctly done  Pressfit makes a cold metallurgical bond rendering a hot one made by
soldering unnecessary. If you solder a Pressfit you lose any advantage from the Pressfit
joint as the thermal excursion is beyond its design limits and has probably bust it, let
alone the pth barrel etc., and end up with a solder joint which at best looks OK. Or maybe
that's worst as it looks OK.

----- Original Message -----
From: Stephen R. Gregory <[log in to unmask]>
To: <[log in to unmask]>
Sent: 21 September 1999 22:39
Subject: [TN] Okay, try not to laugh...


> Hi Techies!
>
> This one you'll get a kick out of. I've been working quite a bit in wave
> solder here recently, and today an assembly that has been built once here
> before (prior to me starting here) came down to my area to be waved soldered.
>
> It had suprised me to see the boards at wave solder because earlier I had
> noticed that there was two right angle connectors being pressed into the
> board. I asked why were they bringing me the boards and I was told; "To wave
> the connectors..." (they were the only through-hole on the board BTW) "But
> why?" I asked, "They're press-fit connectors!" The reply was; "Well, that's
> the way we did them last time..." I tried not to laugh...honestly I
> did...kept a pretty straight face actually.
>
> So when ya'll get through laughing, tell me this, what kind of problems can
> occur from trying to wave solder press-fit connectors...besides the obvious
> barrel fill issues that come from the design of compliant-pin press fit
> connectors keeping the solder from flowing up the barrel..."No wonder we had
> some many solder problems last time.." I was told by a few of rework
> operators here...kept a straight face on that comment too. (These are Harting
> press-fits by the way, a kind of triangular spade looking pin that almost
> fills the whole barrel).
>
> Me in my logic, thinks that since the connectors were pressed in, there's got
> to be some slight barrel deformation and/or strain put on the barrel walls.
> Then running it across a 500-degree pot of molten solder just adds to the
> strain from the thermal expansion it's going to see and could create some
> problems.
>
> Now I might entertain wave soldering a press-fit if I got a board in that had
> holes way out of spec and the connectors could be almost pushed in with your
> hands. But these connectors have good contact throughout the barrel, and the
> pins have been deformed (complied) with the barrel as they were pressed-in.
>
> There's a rumor a-foot that some think we should wave them anyway so they
> look like the ones we built before. I think that's almost the stupidest
> reason I've ever heard to do something like that. I wanna know if there's
> anything detrimental to waving these boards with a nice tight press-fit
> already done...I think there is. What do ya'll think?
>
> -Steve "I'm about to pull my hair out!" Gregory-
>
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