I suggest a via plug from the BGA side to prevent issues under that
device. If the via is drilled .3 mm or less a standard LPI flood coat
will provide sufficient via plug from that side. This will also leave
the back side open for any testing requirements post assembly. Filling
the via is more costly and in this case appears not to be needed.
Jeffrey Bush
Director, Quality Assurance and Technical Support
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302-1890
Tel. 802.257.4571.21 Fax. 802.257.0011
[log in to unmask]
http://www.vtcircuits.com
-----Original Message-----
From: Tempea, Ioan [mailto:[log in to unmask]]
Sent: Friday, October 01, 2004 9:50 AM
To: [log in to unmask]
Subject: Re: [TN] Via filling
Close the via, to solve the conflict between plugging or covering the
via from the solder side, but also covering the vias that are inside the
BGA land patterns, on the component side. A via covered from both sides
will outgass, throwing caps all over the place and eventually disturbing
the BGA joints.
Why not covering the vias of the BGA only and leave all others open at
both ends? To avoid via-via and via-pad shorts due to wave soldering (we
really have high density here) and to avoid vacuum loss during ICT.
Regards,
Ioan
> -----Original Message-----
> From: Jeffrey Bush [SMTP:[log in to unmask]]
> Sent: Friday, October 01, 2004 9:34 AM
> To: TechNet E-Mail Forum; Tempea, Ioan
> Subject: RE: [TN] Via filling
>
> What is the purpose of the via filling - via in pad or just to close
> the via?
>
>
>
> Jeffrey Bush
> Director, Quality Assurance and Technical Support
>
> 76 Technology Drive - POB 1890
> Brattleboro, Vermont 05302-1890
> Tel. 802.257.4571.21 Fax. 802.257.0011
> [log in to unmask]
> http://www.vtcircuits.com
>
>
>
> -----Original Message-----
> From: Tempea, Ioan [mailto:[log in to unmask]]
> Sent: Friday, October 01, 2004 9:22 AM
> To: [log in to unmask]
> Subject: Re: [TN] Via filling
>
>
> Thank you Werner,
>
> I'm saving it in the right place now.
>
> But does the filling percentage play a role? Should I push my PCB
> suppliers to measure and guarantee something close to 100% filling?
>
> One supplier told me they are printing the solder mask in the vias and
> check with blotting paper if the stuff gets through. And if not, they
> make a second pass. For me this is an overkill and we must be paying
> something extra for it.
>
> By the way, our products are telecom, some for outdoors and high-rel,
> like 911 systems and power line protection.
>
> Best regards,
> Ioan
>
> > -----Original Message-----
> > From: Werner Engelmaier [SMTP:[log in to unmask]]
> > Sent: Friday, October 01, 2004 9:02 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] Via filling
> >
> > Hi Ioan,
> > PTVs filled with solder mask/epoxy during the soldering processes
> > will
>
> > experience less compressive loads on the copper barrel, and thus
> > less tensile stresses which are part of the loading leading to
> > innerlayer separation. During operationall use, this fill plys no
> > significant reliability role. PTVs filled with solder of course
> > offer no advantage during the
> soldering
> > processes--they are filled during them. In operational use, fully
> filled
> > PTVs are
> > subjected to reduced loads on the copper barrel than empty ones, and
> PTVs
> > with voids in the solder fill will experience localized higher loads
> due
> > to the
> > stress concentrations---having said this, it needs to be emphasized
> that
> > this
> > is only significant if the operational conditions are severe, such
> > military and automotive.
> >
> > Regards,
> > Werner Engelmaier
> > Engelmaier Associates, L.C.
> > Electronic Packaging, Interconnection and Reliability Consulting 7
> > Jasmine Run Ormond Beach, FL 32174 USA
> > Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
> > E-mail: [log in to unmask], Website: www.engelmaier.com
> >
> >
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