Roger:

I'll take a whack at this.

> Esteemed Colleagues,
> An engineer here wants to reject some SMD assemblies that were assembled
> by
> hand.  I have reviewed the A-610, but it doesn't necessarily cover all the
> problems we see.  The product has been exhibiting random field failures,
> and some are failing at temperature extremes (-20deg C or +70 to 85deg C).
>
        To start with, what did you ask the CM to do? Build em' so they work
or did you specify a workmanship requirement?

> 1) Some pads are missing under a MQPF-144 device.  "Former" pads with a
> connection have the lead raised off the board and wire soldered from lead
> to a via under the device.  Some unconnected pads are missing and no
> solder
> joint is possible.  Accept or reject?
>
        Missing pads indicate either really bad circuit boards or a solder
operator who is used to using a jackhammer. Unless you gave the CM the
authority to perform "repairs" as opposed to "rework" I would reject them
all. Again, it depends on what you specified.

> 2) On same device, the wire fix for the removed pad raises the device so
> that the leads had to be bent to the board and then soldered.  Looks bad.
> Accept or reject?
>
        Anything that looks bad shouldn't be accepted. Anytime a lead needs
to be bent out of the normal shape in order to make a connection is
rejectable. But then again, what did you ask for?

> 3) What are your thoughts about manual SMD assembly with fine pitch parts
> down to 0.5mm for production?  (By manual I mean manual part placement and
> manual soldering.)
>
        A couple of ways to handle this. Using a hot air tool is a bit more
forgiving than hand soldering with an iron. However, I would only do this on
a limited basis. For a "production" run, NO!

> 4) What are your suggestions as to having our CM improve their soldering
> techniques?
>
        Obviously training. But more importantly, finding someone with the
right touch. Even training can't make a watchmaker out of everyone. Identify
those with the talent and go with them.

        Hope this helps. Good Luck.

Bill Kasprzak
Moog Inc., Electronic Assembly Engineering

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