Dave,
I don't know if this will work, but it may be worth a trial. We had problems
with large voids some years ago. Reason was outgassing from hydrogen
imbedded in the nickel plate. I do no know how this happened, but a plating
bath chemist ought to have the answer.
Don't you have comments on my own bga question? How strong and reliable is
the less-than-micron thick P-rich SnNi IMC?
Inge
--------------------------------------------------
From: "Zilber Gil" <[log in to unmask]>
Sent: den 25 February 2010 08:07
To: <[log in to unmask]>
Subject: Re: [TN] Suggestions on Making BGA Voids
> Hi Dave,
>
> What was the PCB finish? If it is HASL the voids will be much smaller
> then if it ENIG.
> You can also use microvia between 1-3 or playing with the laminate
> thickness.
>
> Regards,
>
> Gil
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
> Sent: Thursday, February 25, 2010 5:43 PM
> To: [log in to unmask]
> Subject: [TN] Suggestions on Making BGA Voids
>
> Hi gang! Ok, I have a fairly crazy request for suggestions on how to
> make BGA voids. First here is the background - Dr. David Bernard
> (Dage), Dave Adams (Rockwell Collins) and I are working on a
> collaborative project to investigate the thermal cycle solder joint
> integrity of BGA components. We are attempting to produce data which the
> IPC JSTD 001 committee can use to revise the 25% maximum void criteria.
> Despite public rumor, this current IPC JSTD 001 void requirement is
> based on actual IPC Class 3 field equipment results submitted to the
> committee several years ago. However, BGAs have changed in both size,
> pitch and solderball diameter since the creation of the void criteria
> thus the reason for collaborative project.
> We have a test vehicle which contains BGAs at 0.5mm, 0.8mm and 1.0mm
> pitch with each having a corresponding larger solderball diameter. We
> have put uvias in the BGA pads to "create" voiding. Great plan, figured
> we had it
> made- however, after running the test vehicles thru a standard reflow
> process (this effort is focused on tin/lead right now) we find that we
> have an average void size in the range of 0-5%! My production process
> folks are very proud of that result but it doesn't do our voiding
> investigation much good (you can imagine the look I got when I told them
> they didn't make enough voids greater than 25%). I know that a number
> of the Technet community have tried to accomplish this voiding task with
> only mild success (i.e. Bev Christian, Martin Wickham, etc.).
>
> My Technet request is - do you have any suggestions on how to increase
> the solderball void size without causing a biased negative impact on the
> solder joint quality? I can obviously make some huge solderball voids
> (such as pouring Doug's Diet Mt. Dew on the test vehicles) but the
> overall quality of the solder joint would not be representative of the
> real world product.
>
> Thanks in advance
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
>
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