Hi, TechNetters!
What plugging is recommended for vias near BGA pads on the BGA side?
Our PCB supplier does not use solder mask. The plugs are printed after hot air
levelling on both sides, with a much thicker material. Sometimes the plugs are very
high . Could it cause problems during solder paste printing?
One other question: How do you ensure that all the pads for BGA have good wetting? When
a SMD component solder joint must be reworked due to a problematic pad, you can see it.
When a solder ball is not connected due to the same problem, you are in big trouble.
How does your incoming inspection deal with this problem?
Thanks,
Gaby
Ryan Grant wrote:
> Hi Jeff,
> The vias immediately adjacent to BGA pads should be plugged with
> solder mask. Savvy board shop are smart enough to perform this operation
> last so no chemicals need to be washed off the bare board and out of the
> plugged vias. Provided your SMT and Wave process does not introduce flux
> into the vias; the only "chemical" that might get trapped is the dirty water
> from the wash (for OA fluxes).
>
> The via plugging near BGA pads on the BGA side really helps drive
> down the DPMO numbers for BGA soldering defects. Rework will really prefer
> the plugged vias as well. It is common for the solder mask web to come off
> during rework BGA pad prep. The via plug helps hold down the webbing, and
> prevents solder robbing down vias, as well as ball to ball bridging.
>
> However, in the end, you have to decide for yourself how much this
> extra effort is worth.
>
> Ryan G.
>
> > -----Original Message-----
> > From: Jeff Hempton [SMTP:[log in to unmask]]
> > Sent: Tuesday, March 14, 2000 8:28 AM
> > To: [log in to unmask]
> > Subject: [TN] ASSY & FAB: vias: To plug or not to plug
> >
> > Hi Technetters,
> > We are researching moving away from plugging our vias with solder
> > mask (problems and reliability issues) and plugging with solder thru
> > the wave solder process.
> > I have read all of the archives, and printed a major novels worth
> > (thanx for past info group, those archives are a wealth!!) bit one
> > item is still missing I hope you can respond with info on:
> >
> > ASSY: Do you have problems with, or design guidelines that address,
> > the solder filled vias under components, or is this even an issue?
> >
> > FAB: How do most of your customers address this?
> >
> > Please, deluge me with your wisdoms, responses and help on this
> > issue.
> > Thanx in advance group.
> >
> > Jeff Hempton, Sr. SMD Mfg. Engineer
> > United Technology Electronic Controls
> > e-mail: [log in to unmask]
> >
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