TechNetters,
I seem to have lost the original e-mail and the subsequent ones before
Julie's. Not in my Delete folder either. Weird.  So hopefully I am not
repeating something someone has already covered. 

Size AND number are important. If all the solder balls are microscopic but
all interball distances are each less than the minimum electrical clearance
there is potential for trouble. 

I can't speak for the 610 committee, but I can say that the 5-24b Solder
Paste Task Group (under the leadership of Dr. Karen Tellefsen) which is
responsible for J-0005 (solder paste) and its associated TM-650 test methods
is rewriting the test method for solder balls.  We are including more
examples of various degrees of coalescence of the solder in one or more
solder balls because the four old photographs that originally came from the
Mil Spec are just not cutting it any more.  The new categories take into
account the sort of thing that is being discussed with relation to 610.  

Julie,
It might be worthwhile to see if you can bring your company's
recommendations forward for a 610 discussion in San Diego.

And I haven't said anything about entrapment.  :)

Regards,
Bev Christian
HDP User Group Facilitator


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Friday, December 23, 2016 12:31 PM
To: [log in to unmask]
Subject: Re: [TN] Solder balls requirement in IPC-A-610

Agree.  in addition, the size of the solder ball matters little if you do
not know the pitch of your BGA, fine pitch is not going to be tolerated
0.13 mm size of loose solder ball as clearance is very tight... As Julie
said, process improvement is needed.  if select proper paste and MFG
condition, even 80 micron PITCH (not space) can be achieved...
http://www.mmc.co.jp/adv/ele/en/products/assembly/past-special03.html
Happy Holiday every body.  

From Julie Silk
> This is one of the few IPC 610 criteria where Keysight Technologies has an
> objection and includes alternate criteria in our supplemental
> specification.  Likely this objection is also still present in the Agilent
> standards.  (Maybe even HP?  Our leveraging covers several company
> transformations.)  Functionally, the IPC criteria doesn't protect from
> shorting risks.  One objection is to the definition of entrapped.  Over
> time (and our products are in the field for a long time), the balls could
> become dislodged.  Our criteria ignores whether a solder ball is entrapped
> and has size, quantity and reduction in conductor distance requirements.
>
> Your basic problem is that you have work to do on solder paste selection
> and process optimization.  You shouldn't have that sort of spattering.
>