Hi Victor,
 
I have many friends in the laminate business that could go into a more deep dive but I'll take a stab.
 
After the sizing is burnt off the woven glass fabric, the adhesion promoting treatment is applied.
Unless things have changed, the adhesion promoter, which is an organometallic compound with one end of the chain loving to bond with glass, and the other end of the chain tailored for bonding with a specific resin type.
 
Unless things have changed, the adhesion promoter is checked continuously along the fabric web as the woven glass fabric is spooled onto the carrier. I believe the adhesion promoter presence is checked by UV or some specific type of instrument for that purpose.
 
When the woven glass fabric is sent to the laminator, the glass cloth is used to make pre-preg for bonding sheets used to make either laminate or bonding sheets for multilayer processing. At this point, unless things have changed, the laminator may check for the promoter by the same method as the glass manufacture, however, the pre-preg web is definitely checked for resin take-up visually or by optical guage. Finally, the treated weight of the pre-preg is measured. Any gross lack of resin would appear here as well as later when the resin coated pre-preg rolls are slit into panel size pre-preg sheets.
 
Resin starvation or dry weave is a non-conforming condition that relates to inadequacies in what is described above and can easily be identified with practical methods available to board shops both at incoming as well as after surface etch.
 
So, there are three different areas where gross amounts of the defect are checked and could be seen glass cloth, laminator, and board shop. Actually, depending on the assembler, an incoming could detect this non-conformance, which would make a fourth area for inspection. So, with all this surveillance, detectable amounts of unbonded resin-to-glass are reduced. Tiny amounts are possible but remote.
 
As for exothermic events, a lot of other things would need to be happen. Basically the lack of treatment or resin attached to glass would need to create a capillary gap bridging conductors and PTHs. This would enable process acids/salts to enter the gap and remain. Next the usual conditions needed to grow a dentrite. Last, you'll see the evidence of the thermal event.
 
It would be very difficult and expensive to look inside a stack-up of a failed PWB and identify a small lack of glass treatment or lack of resin-to-glass bonding as a root cause. Not impossible, but difficult and expensive.
 
Just my $0.02 . 
 
Hope this helps.
 
Gerry Gagnon 
 
 

 
> Date: Wed, 25 Sep 2013 14:16:20 -0500
> From: [log in to unmask]
> Subject: Re: [TN] PWB / PCB fabrication
> To: [log in to unmask]
> 
> Brs,
>    What is the likelihood that the woven glass cloth had some spots/areas which did not accept the treatment process.   I believe that the term for this is resin recession, non-wetting.   Is it possible that this anomaly could cause an exothermic event to occur?
> Victor,
> 
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerry Gagnon
> Sent: Wednesday, September 25, 2013 2:09 PM
> To: [log in to unmask]
> Subject: Re: [TN] PWB / PCB fabrication
> 
> Hi Victor,
> 
> Treatments for the different resin types are typically applied by the glass fiber/glass cloth manufacturer.
> 
> Brs,
> 
> Gerry Ggnon
> 
> > Date: Wed, 25 Sep 2013 10:45:15 -0500
> > From: [log in to unmask]
> > Subject: [TN] PWB / PCB fabrication
> > To: [log in to unmask]
> >
> > Fellow TechNetters;
> >
> >    When is the glass woven cloth condition to accept the resin for laminate bonding?   Is this a portion of the fab process or is the vendor of the woven glass cloth condition by the vendor?
> 
> >
> >
> > Victor,
> >
> >
> > ______________________________________________________________________
> > This email has been scanned by the Symantec Email Security.cloud service.
> > For more information please contact helpdesk at x2960 or
> > [log in to unmask]
> > ______________________________________________________________________
> 
> 
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________
> 
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask] 
> ______________________________________________________________________
 		 	   		  

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________