[time-nuts] Parts Selection

Greg Broburg semiflex at comcast.net
Fri Mar 25 18:52:47 UTC 2011


I have assembled hundreds of such parts using only a
low cost Antex 15W soldering iron, some fine diameter
solder and some solder wick. A hot air gun makes
removal very easy and I have never damaged a PCB
using the hot air removal method.

Solder diameter should be .010 - .015 mils Large
diameter solder is a problem with this method.

To put a .5mm pitch part down without any fancy stuff

1: Carefully align the part with the pads, double check
that Pin 1 is in the correct alignment. Now solder a
couple of pads at two opposite corners to stabilize the
part. Expect to solder two to four pads at the corners
and that they will be shorted. Do not worry if you have
shorts between closely spaced pads. We will fix that later.

2: If the pad alignments are not perfect then reheat one
of the two opposite corner pad (s) and move the part
until it is correctly aligned.

3: When all pads are aligned then carefully solder all of
the leads to all of the pads. Do not worry if some pads
are shorted. do not worry if all pads are shorted.

4: Using .025 mil solder wick dipped in RMA solder flux
if not already fluxed, desolder all of the pads. In other
words, the solder wick is not effective at removing all of
the solder. What is left from surface tension will be the
correct amount.

5: Using a QTip with alcohol / acetone / dope thinner
clean all pads of flux. Do this twice or more each time
with a fresh QTip tip.

6: Inspect using magnification if necessary, to verify no
shorts or solder balls between pads. If so, use the solder
wick to remove the short.

I have done this hundreds of times.

Greg



> With regards to soldering .5mm pitch parts:
>
> I've never done that professionally or as a hobby.
>
> I don't see myself doing this at home.


On 3/25/2011 11:07 AM, Bob Camp wrote:
> Hi
>
>
>
> Just a show of hands sort of thing. It comes up each time we talk about
> projects and never really gets answered. Rather than trying to work it out
> as a part of a project, let's see if it can be addressed by it's self.
>
>
>
> How many people are willing to solder up a project with multiple 0.5mm
> spacing>=144 pin package IC's on it? There's a typical package drawing at
> the end of:
>
>
>
> http://www.national.com/ds/DP/DP83816EX.pdf
>
>
>
> I'm sure it's a "what's in it for me?" sort of question. Let's assume it's
> just neat piece of bench gear rather than a home grown cesium standard for
> $100.
>
>
>
> I don't think this part really matters, but it might to some people. Say
> each chip is well below $100, but above $20 each. There might be only one
> part like this on some projects, but for the sake of this poll, let's say
> there are two or three of them. Net is roughly 250 to 500 pins like this to
> solder, on some number of packages. It's part of a project that will cost
> you $250 to $500.
>
>
>
> I'm not talking about opinions on weather it can or can't be done. It
> certainly can be done and is done every day. What I'm asking is - would you
> buy a bag with the parts all in it? If you do are you going to put it
> together in a reasonable amount of time?  Reasonable time might mean
> different things to different people. For the sake of completeness, yes you
> also need to get it working after you assemble it.
>
>
>
> Next layer (you knew there had to be more) - have you done it before
> (anywhere)? / done it in the last 2 years (at home)? / are you set up to do
> it today (at home)?
>
>
>
> I'm not trying to get into "how would you do it / what would you need /
> could you farm it out". Those are also neat questions, but not part of this.
>
>
>
>
> I'll start off the voting (and yes the answers are out of order):
>
>
>
> Done it in the before - yes.
>
>
>
> Done it in the basement / last 2 years - no.
>
>
>
> Set up to do it in the basement - yes, but not set up well.
>
>
>
> Would I buy one - done that before. Likely would again. (counts as a yes).
>
>
>
> Would actually do it in a reasonable amount of time - unlikely.  (That
> counts as a no).
>
>
>
> Any more votes?
>
>
>
>
>
> Bob
>
>
>
>
>
>
>
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