I concur with all Dennis said and speculated.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dennis Fritz
Sent: Friday, April 20, 2018 4:48 AM
To: [log in to unmask]
Subject: Re: [TN] R: [TN] R: [TN] PCB failure
Comment on resin detection. If you have SEM/EDX capability, see if you can focus on the area between the innerlayer copper and the deposited copper.
If you can detect bromine, that is from the circuit board. If there is no
bromine, then the organic is the potting compound and you have smeared while polishing.
I agree there is no etchback, but there does appear to be glass frosting as the deposited copper seems to have penetrated the exposed fiber bundles in the hole.
Not sure about drilling. There does not seem to be any chunks torn out from the sidewalls. However, I do see the glass as a bit roughened in the holewall. In my experience, drilling too fast or with dull bits will make
a rougher sidewall than I see here. Perhaps you have the opposite - slow
drill speed overheating the resin and possibly smearing it across the
internal copper posts. Possibly, poor or no entry material is allowing
the drilling to be too hot.
Do you know for sure that the desmear is wet chemistry -
swellant/permanganate? Not plasma? Is there a chance the desmear was
skipped, or the swellant or permanganate way too weak?
In my 30 year old definition, this is post separation. Resin recession to
me is straight copper sidewall with resin pulling back from the copper.
Holewall-pullaway is straight laminate wall and bulges in the copper itself. I see neither in this section - just post separation.
As others have said - section some boards before assembly soldering. I
bet you see the "weak interface" line in those, especially horizontal sections.
Denny Fritz
On Thu, Apr 19, 2018 at 8:28 AM, David Hillman < [log in to unmask]> wrote:
> Hi Gil - I know when our FA lab is working this type of issue, they
> can see the difference between the board resin and the cross section
> potting compound. I do know its a cross section that needs to be
> prepared carefully as that area can smear if the wrong
> pressure/grinding/polishing process is not followed.
>
> Dave
>
> On Thu, Apr 19, 2018 at 7:22 AM, Zilber Gil <[log in to unmask]> wrote:
>
> > Thanks Dave,
> > I will do it. But, I am afraid that during the sample preparation,
> > this area is contaminated by the resin used for the metalorgic cross-section.
> Do
> > you have experience if we can distinguish between the PCB's resin
> > and the sample resin?
> > Regards,
> > Gil
> >
> >
> >
> > נשלח מסמארטפון ה-Samsung Galaxy שלי.
> >
> >
> > -------- הודעה מקורית --------
> > מאת: David Hillman <[log in to unmask]>
> > תאריך: 19.4.2018 13:56 (GMT+01:00)
> > אל: TechNet E-Mail Forum <[log in to unmask]>, Zilber Gil <
> [log in to unmask]>
> >
> > נושא: Re: [TN] R: [TN] R: [TN] PCB failure
> >
> > Hi Gil - if you have the resources, you should put that cross
> > section in the SEM and look for possible resin smear on the inner
> > layer/PTH
> interface.
> > Resin smear could cause the defect you are seeing.
> >
> > Dave Hillman
> > Rockwell Collins
> > [log in to unmask]
> >
> >
> > On Thu, Apr 19, 2018 at 4:02 AM, Zilber Gil <[log in to unmask]> wrote:
> >
> >> Thanks
> >> It is a leaded hand soldering of that device. I will check if the
> >> other failed location has hand soldering also. The material is a
> >> high tg
> material
> >> (Isola 370 HR).
> >> Regards,
> >> Gil
> >>
> >>
> >>
> >> נשלח מסמארטפון ה-Samsung Galaxy שלי.
> >>
> >>
> >> -------- הודעה מקורית --------
> >> מאת: SALA GABRIELE <[log in to unmask]>
> >> תאריך: 19.4.2018 10:46 (GMT+01:00)
> >> אל: 'TechNet E-Mail Forum' <[log in to unmask]>, Zilber Gil <
> >> [log in to unmask]>
> >> נושא: R: [TN] R: [TN] PCB failure
> >>
> >> Gil,
> >>
> >> you could show the picture to TNetters by mailing it to Steve
> >> Gregory [log in to unmask] whom very kindly support us when we need
> >> to attach picture (many thank Steve for you service) so all the
> >> TNetters will see
> the
> >> picture.
> >>
> >> I have seen your picture, yes it is a IPS (Inner Plane Separation)
> >> from PTH.
> >> It may be due to thermal stress in Z assy, but why ?
> >> You made baking to PCB so it should not be a matter of internal
> >> over pressure due to moisture blow-off.
> >>
> >> Or may be too low Tg of laminate or high CTE in Z assy ?
> >> Are you running Lead Free Reflow ?
> >>
> >> Etc...
> >> Gabriele
> >>
> >>
> >> -----Messaggio originale-----
> >> Da: TechNet [mailto:[log in to unmask]] Per conto di Zilber Gil
> >> Inviato: giovedì 19 aprile 2018 10:27
> >> A: [log in to unmask]
> >> Oggetto: Re: [TN] R: [TN] PCB failure
> >>
> >> Thanks Gariele,
> >> The PCB is new, and it was baked before assembly.
> >> Thanks,
> >> Gil
> >>
> >>
> >>
> >> נשלח מסמארטפון ה-Samsung Galaxy שלי.
> >>
> >>
> >> -------- הודעה מקורית --------
> >> מאת: SALA GABRIELE <[log in to unmask]>
> >> תאריך: 19.4.2018 10:07 (GMT+01:00)
> >> אל: [log in to unmask]
> >> נושא: [TN] R: [TN] PCB failure
> >>
> >> Hi Gil,
> >>
> >> did you handled correctly PCB against moisture absorption ? Like
> >> guide lines of IPC-1601A ?
> >> Shelf life of your PCB ?
> >> Any Baking before reflow?
> >>
> >> Gabriele
> >>
> >> PS: no picture is attached
> >>
> >> -----Messaggio originale-----
> >> Da: TechNet [mailto:[log in to unmask]] Per conto di Gil ZIlber
> >> Inviato: giovedì 19 aprile 2018 09:27
> >> A: [log in to unmask]
> >> Oggetto: [TN] PCB failure
> >>
> >> Hello Tech,
> >> We encounter a PCB discontinuing. Cross section shows conductor
> >> separation from TH.
> >> The PCB manufacturer claims it is due to overheating during
> >> assembly. To me, it looks like bad PCB manufacturing.
> >> Please look at the picture and give me your feedback.
> >> Thank you
> >>
> >>
> >> ---
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