Roger, 

I've added my comments to each question.  Hope this helps.  If you need more assistance let us know. 

Kathy 

>>> [log in to unmask] 08/27/01 03:38PM >>>
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?

**  If you didn't give prior approval I would reject.  The CM should have gotten approval prior to repair.  The end use should be considered when making modifications. You might also be able to bring up section 10.7.2 of the IPC-610 rev c.  This criteria is judged by the amount of height the pad is lifted.  Basically if the damaged pad is more than 1 pad height off of the PCB it is a defect.  Considering they are missing I would say that is more than 1 off.  

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?  

** I would reject again.  The soldering operator shouldn't have stretched the lead to fit and put stress on the lead and component junction without your approval.  The J-STD-001 has a criteria that allows the lead to be more than 2 thicknesses off of the pad and it is acceptable.  If the pins had not been forced down would the lead had been 2 thicknesses above the PCB pad?  We call this a 2T violation.  

re 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.)

** Not a problem if performed properly.  I've hand placed and hand soldered 100's of these devices with no problem.  

4) What are your suggestions as to having our CM improve their soldering
techniques?

***  Training, training, and more training...  Do they have anyone at the CM site that has formal soldering training that was obtained within the last 3-5 years?  

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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