Steve,
I have experienced the exact same part and the associated
problems, in fact I have some of the buggers sitting on my desk right
now. Search for a company named teka that makes the pc 104 connectors
with solder and flux in the leads. All you have to do is hand place
them before smt reflow and everybody is happy. Good luck.
John Koleszar
> -----Original Message-----
> From: Stephen R. Gregory [SMTP:[log in to unmask]]
> Sent: Tuesday, January 12, 1999 12:59 PM
> 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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