About 13 years ago, before Revision C to J-STD-001 and IPC-A-610, the task groups were struggling to resolve comments for hole fill requirements. The 

leader of the IPC Assembly and Joining committee at that time was Jim Maguire, then at Boeing and moved on to Intel. Jim pulled together a bunch of pages (224 to be exact) about hole fill from publications and technical presentations by industry experts. We scanned them to a pdf file way back when so they are images only--not searchable text. They can be downloaded from http://files.ipc.org/HoleFill-complete.zip



When referring to the hole fill criteria in J001 and 610, it's important to remember that the criteria is intended as visual assessment--what are the visible levels of solder within the hole. 75% fill means that there is no more than 25% of visible barrel space (counting both top and bottom). It was not intended and it is not appropriate to state that 75% fill requirement is related to total volume of solder.



The topic of voids within the solder in the barrel--not visible without x-ray or destructive analysis--has been discussed at IPC committee meetings. More than one person has made the statement that voids within a solder connection, including inside the solder in barrels, actually provides stress release for the surrounding areas. 



There is no current industry consensus on the maximum amount of voiding that should be acceptable in solder mass within a barrel, in a BGA ball, or within the solder between two flat surfaces (bottoms of BTC, gull wing leads, chip components, etc.). Having followed these discussions for the 15 years I've been in IPC committee meetings, it's obvious that there are a lot of opinions and even some good test data. Some of the Class 3 avionics and weapon system manufacturers in particular want the conservative approach (lower void levels) so it's been hard to move away from the 25% in BGA balls and nothing has been established for other connections.



Regarding voids within PTH, I sometimes suggest to users that they find the oldest functioning through-hole assembly they can find (some military systems are 30-40 years old) and x-ray the assembly to see how much voiding is in the holes. Find the connections with the largest void area in connections that have not failed and measure. That isn't necessarily an indicator of how much void will never fail, but I believe anyone that does this will be surprised to see how many voids & the size of the voids that have been in the products for decades without failure.



Jack Crawford

IPC Director Certification and Assembly Technology

IPC International Inc.

3000 Lakeside Dr. Suite 309S

Bannockburn, IL 60015

847-597-2893

Fax 847-615-5693

[log in to unmask]

www.ipc.org

www.ipc.org/status  www.ipc.org/certification  www.ipc.org/downloads