From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: 1523 joints
Date: Wed, 23 Oct 2002 01:01:30 GMT
NNTP-Posting-Date: Tue, 22 Oct 2002 18:01:30 PDT
"Christopher R. Carlen" wrote:
> Hi folks:
> I have a design in the works, and it looks like it will involve two PCBs
> with a total of 1523 solder joints per assy. I will likely need to
> produce between 4-10 of these over the next few months.
> The objectional quantity of solder joints is making me consider having
> them manufactured by a local custom electronics assembly shop.
> But I dread the thought of something going wrong, and having to waste
> time figuring out what went wrong, and straightening it out with the
> possible cost of wasting my PCBs or having to salvage them. Plus, the
> time to document the assembly procedure and kit all the parts probably
> will equal at least one or two assembly times.
> Finally, the main PCB has the active stuff on one side, and the other
> side has a bunch of BNCs and LEDs, that have to be placed in the board,
> and then the board has to be placed into the panel in which it will
> live, before soldering the parts, so that the LEDs will stand off at the
> right height, and the BNCs will not get soldered with little tolerance
> errors that would make it impossible to get the PCB into the panel if
> they were soldered without first mating to the panel. Trying to
> describe this and then hope they do it right, is also dreadful.
> In short, the thought of other people doing my work and screwing it up,
> is dreadful.
> But I'm sure those among us who are used to manufacturing have learned
> to deal with this. For me it represents a substantial obstacle to
> opening up my mind to outsourcing some of my assembly work--something
> which I have never done before. The sadder part is that there are
> terribly few techs. here at the lab who can do this work with the kind
> of care that I would hope for, and none in my immediate facility. The
> only master builder we had left. Then he regretted it, but couldn't
> bring himself to reverse the error.
> Oh well. Any comments welcome on your experiences and wisdom with
> getting jobs outsourced, how to describe what to do, how to cover one's
> buttocks if there is an error, etc.
Currently we are using a small outside shop for board assembly in low
volume (around 10 at a time). One board that we make has more than 1200
solder joints that I can recall without reference to the schematic or
the BOM. It is mostly surface mount. This leads to several frustrations.
One of the worst is that capacitors cannot be varified and must be
replaced if it is suspected that a wrong value was used. We have not
found marked capacitors in 1206 size. Another problem is parts marked
"Do Not Stuff" on the BOM and the schematic. They are quite often suffed
anyway with seeming arbitrary values. Bad solder joints and occasional
joints not soldered at all give very puzzling problems - especially in
the analog power circuits.
In spite of these problems, we prefer outside assembly. Each board takes
about 12 hours to assemble and quite frankly, I could not assemble them
myself because my eyes are not good enough. Trouble shooting takes a few
hours per board and, in many cases, I send the board back to the shop
for repair after I find the problems.
It's a mixed bag but because none of us involved in the design of the
boards will assemble them, we have no choice.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org