Steve,
It sure sounds like something I went through at a CM I was at a couple
of years ago. Is kester telling you the truth? That I can not answer,
but I think I have a solution for you. There is a company called TEKA
Interconnection, they make connectors like you have described. These
connectors have what they call solder bearing technology. They look
pretty cool. I was in the process of trying this out but never finished,
I moved on to another CM. Anyway, if you would like this information
please send me you fax # and I will send to you.

Angie Marques
Quadrus Manufacturing
SR. Process Engineer
408-918-5045
[log in to unmask]

> -----Original Message-----
> From: Stephen R. Gregory [SMTP:[log in to unmask]]
> Sent: Tuesday, January 12, 1999 9:59 AM
> To:   [log in to unmask]
> Subject:      [TN] Assy:Through-hole Solder Preforms...
>
> Good Day Ya'll!
>
>      We just got a new customer here last week and built two 10-board
> proto
> kits for them. Those boards are a type of power supply, and we're
> going to be
> doing another board that they call a 4-port RS-232 + 48 digital I/O
> PC/104
> Module. All 3 assemblies are roughly 3.5" square and are mixed
> technology.
>
>      There's another thing common between all three assemblies besides
> their
> size, what they call dual-mount headers. Each board has two of these,
> one is a
> 64-pin (2X32 pins), and the other is a 40-pin (2X20 pins). These are
> basically
> real long gold plated headers with plastic female type receptacles at
> one end.
> They're installed with the header pins going THROUGH the board and
> soldered.
> The header pins stick out the backside of the board 10mm, and you have
> your
> female sockets on the topside, so now what you have is a stackable
> type of
> board connection system.
>
> Cool connection system, BUT, there's a big problem with soldering
> these dad-
> blamed things! You can't wave solder them because: 1.) They're gold
> plated, no
> solder on the contact area (solder fillet must stay below .100" as
> measured up
> the pin from the surface of the PCB). 2.) Even if the gold plating
> wasn't an
> issue, they stick out 10mm on the bottom...you'd need a wave that
> shoots up
> and looks like "Old Faithful" to reach the bottom of the board!
>
> "So hand solder em' ya big weenie!" some of you may be muttering under
> your
> breath now. Well there's a problem there too. The way these two
> connectors are
> laid-out on the boards couldn't be any worse, they're parallel right
> next to
> each other, spaced .100" apart. We've got 4-rows of 10mm long gold
> plated
> pins, .100" apart, that we've got to solder and not get any solder on
> the gold
> plating...just peachy huh?
>
> My senior rework lady Trang, got us through the two proto kits of
> 20-boards.
> She somehow was able to thread her soldering iron down thru the pins
> and
> solder the connectors in without so much as a pimple of solder on the
> pins
> (She simply amazes me sometimes! Goes to show what clean livin' and no
> caffeine can do for ya!) But we simply can't do that in production,
> it'll take
> forever, and I don't wanna burn Trang out, she's the only one steady
> enough to
> do it.
>
> So I called around to get quotes on some preforms. I've seen
> daisy-chained
> donut preforms that you can use for headers and what have you that has
> the
> same kind of footprint. I've used preforms before, but the kind for
> edge clips
> for little SIP modules, not for PTH. So I called Indium, AlphaMetals,
> Bow
> Solders, and Kester...they all make preforms. Everybody has quoted me,
> but
> Kester told me that they think I may still may have a problem. They
> said that
> from their experience, I'm going to have difficulty obtaining
> consistent
> solder joints using preforms. They said that unless I can ensure very
> consistent heating between all the pins, that I'll probably wind-up
> with some
> joints being insufficient because the solder will tend to wick to the
> hottest
> pin. I was planning on using a heat gun to provide the heat, and maybe
> even
> going so far as to make a nozzle that will enclose all the pins. But I
> can't
> put it in a reflow oven unless I want to hand solder eight 10-pin SIP
> RPACKS,
> and a 2-pin metal canned crystal afterwards...I still need to look and
> see if
> the plastic on the headers can take the heat anyway.
>
> So after reading this journal, my question is (boy, I sure take the
> scenic
> route sometimes don't I?); have any of you had any experience with the
> kind of
> preforms I'm thinking of using? Is what Kester saying true?
>
> 'Preciate any info at all!!
>
> -Steve Gregory-
>
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