Hi Roger,
as Kathy said, training, training, training...
It´s possible to handsolder QFP´s even with 0,4mm pitch, we´ve done it many
times.
But with pads loose or missing it shows that there´s not enough training,
maybe inadequate equipment and not the right attitude regarding workmanship.
I know it´s quite annoying to quarrel about acceptance of such mess if the
CM doesn´t admit your claim. To do that would be the first step towards
improvement. Otherwise it would be good to look for other (better) shops.
Wolfgang
-----Ursprüngliche Nachricht-----
Von: Roger M. Stoops [mailto:[log in to unmask]]
Gesendet am: Montag, 27. August 2001 22:38
An: [log in to unmask]
Betreff: [TN] SMD Assembly Problems
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).
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?
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?
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.)
4) What are your suggestions as to having our CM improve their soldering
techniques?
Sorry I don't have pictures for Steve-o's web site. Something I will have
to work on for the future. We rarely have problems from our CMs (congrats
to the CMs out there...).
Big TIA,
Roger M. Stoops, C.I.D., PCB Designer
Trimble
Engineering and Construction Division
5475 Kellenburger Rd.
Dayton, OH 45424-1099 USA
Ph: +01 937.233.8921 or +01 937.233.4574 ext 288
Fax: +01 937.233.7511
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