Dear Luis,
I am going to briefly discuss voiding from our perspective. For additional information I encourage
you to visit our more detailed article on this topic located at
http://www.aimsolder.com/techarticles/tech%20sheet%20BGA%20voiding-%20reducing%20through%20process%20optimization.pdf
There is still a debate as to the negative effects of voids. In general, large voids that take up a
high percentage of the volume of the joint are considered problematic. These voids are more likely
to have a more significant effect on the mechanical integrity and heat dissipation ability of the
solder joint. Smaller, evenly dispersed voids that take up a lower percentage of the volume of the
joint are often considered "normal" and non-problematic. I'm sure that others can comment more on
this.
Voiding can be impacted by the materials in use as well as the SMT process. In our experience
voiding under BGAs can be significantly reduced through process optimization.
Handling- If BGAs are not stored and handled property a variety of processing defects can occur,
including voiding and popcorning. The key is to follow the manufacturers recommendations regarding
moisture levels, baking, storage time, etc. A common practice is to bake BGAs and vacuum seal them
with a bag of desiccant in a Mylar bag.
Printing- BGA solder defects are often traceable to the printing operation. If the printing is
mis-registered, or if the volume printed is insufficient, it is likely that the resulting BGA solder
joints will not have the desired integrity. For this reason, it is imperative that printing
equipment be properly calibrated, set-up and verified. 100% inspection of printed BGA sites may be
required prior to placement to verify paste coverage, uniformity, and volume.
Reflow Profiling- Two types of reflow profiles are most commonly utilized when reflowing SMT
assemblies: Ramp-Soak-Spike (RSS) and Ramp-to-Spike (RTS). Optimizing these profiles per the solder
paste manufacturer's guidelines can help to reduce voiding. In addition, one can also utilize the
"LSP" (low soak profile) profile, which has proven to significantly reduce voiding when used in
conjunction with several types of BGA components. The success of the LSP profile lies in its
ability to dry out the solvent of solder paste before the reflow zone. I'll be happy to send
additional info on the LSP profile to you if you like.
Regards,
David Suraski
[log in to unmask]
AIM
+1-401-463-5605
www.aimsolder.com
> -----Original Message-----
> From: Luis Gallegos [mailto:[log in to unmask]]
> Sent: Monday, January 26, 2004 10:02 AM
> To: [log in to unmask]
> Subject: [TN] PBGA Void/pin holes>
>
> Good morning Technetters.
> I am having some occasionally voids/pin holes on our PBGA. We are
currently
> using NC293 Sn63/Pb37 Aim solder paste. The board is silver plated.
Printing
> with a 6 mil stencil.
> Is it normal to have occasionally voids?
> We have bake our PBGA's prior to reflow, and also work with the oven
> profile. Any suggestions.
> Thank you
>
> Luis A Gallegos
> Automation Senior Technician
> SANMINA-SCI
> Pleasant Prairie WI
> Phone: 262 947-7700
> [log in to unmask]
>
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 1.8e
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to
> [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to
> [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
> for additional information, or contact Keach Sasamori at [log in to unmask] or
> 847-509-9700 ext.5315
> -----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
