Sam,
Lets take your questions one at a time.

How can we analyze a defective board that has blow holes which occurred
during the assembly process?
[John Guy]  I'm not sure what kind of analysis you would like to do.  You
either have them or you don't and you can usually pick this defect up by
doing a visual inspection.  This defect is often accompanied by solder
balls.  If your consern is the reliability of the resulting solder joint,
you could do some kind of ESS testing or inspect that the solder joint
meets some minimum requirement.

What could cause the defect?
[John Guy]  If the assembly is surface mount, this defect is most often
caused by improper reflow profiling.  You are not sending enough time at
the preheat temperatures before ramping to the boiling point of the
volitals in the solder paste, or the temperatures you are using to preheat
are too low.  Colecting a temperature profile should give you a lot of
insite into the root of the problem.  If you are talking about through
hole, there are a number of sources.  You could have excessive moisture in
the laminate and it is outgassing, or the profile or board layout could be
possible sources.

How can the root cause be determined?
[John Guy]  You could record a thermal profile to determine if the solder
paste/flux requirements are being met.  You coudl also inspect the boards a
look for trends in the locations of the blow holes.  If you can provide a
bit more information, I'm sure someone on the forum has had a similar
problem and found the solution to it.

Thank you for your input.

I hope this helps.

John Guy
ACI / EMPF
714 N. Senate Ave.
Indianapolis, IN 46202-3112
voice:  (317) 655-EMPF ext.130
fax:    (317) 655-3699
e-mail:         [log in to unmask]


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