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One note to add. I was faced with the same type of issue a few years back
with 50% vertical fill. I left the company before any of the product failed
in the field ;-)
But seriously, the biggest issue that I wrestled with at that time was the
thought of pcb defects that are "covered up" by good vertical hole fill,
such as cracked barrels. A cracked barrel that is filled with solder may
never cause a problem, but one that is void of solder at the location of the
crack can result in intermittent connection between two layers... resulting
in field failure. I personally never came across such a failure, but I was
told (by a reputable source) that it has happened.
Good luck
> -----Original Message-----
> From: Vaughan, Ralph H [SMTP:[log in to unmask]]
> Sent: Friday, June 26, 1998 1:49 PM
> To: [log in to unmask]
> Subject: Re: [TN] Thru-hole Reliability
>
> Al,
>
> I agree with other comments that it shouldn't be too difficult to
> demonstrate joint reliability with destructive testing, but if your
> customers are like some I know, they my think that the letter of the
> spec is the only definition of acceptability. If so, we have improved
> heavy board solderability by pre-heating to around 200'F just before
> placing on the solder conveyor. This is not very handy 'cause the part
> is so hot, but it may get you over the hump.
>
> Ralph Vaughan
> Boeing-Atlanta
>
> > ----------
> > From: McMonagle, Michael R.[SMTP:[log in to unmask]]
> > Reply To: TechNet E-Mail Forum.;McMonagle, Michael R.
> > Sent: Friday, June 26, 1998 1:22 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Thru-hole Reliability
> >
> > If you have already done everything you can with wave parameters such
> > as
> > preheat/speed/dwell/flux activity you now have a quandry with quality
> > assurance and possibly end users. You may want to approach it from the
> > same way you would prove integrity of an intrusive reflow/pin in paste
> > connection. If you cannot achieve acceptable volume per industry spec,
> > you need to assure quality/engineering/customer of a robust
> > physical/electrical connection. Begin by cross sectioning a variety of
> > connections on a few boards to get real average expected volume
> > measurements under your existing process and to show
> > consistency/repeatability. It will also show that the joint, though
> > minimal, has no hidden voids which would further reduce volume. You
> > can
> > then take non-cross sectioned joints from the same boards and perform
> > pull testing to demonstrate physical integrity. Pull testing will
> > normally prove that either the pin breaks before the joint, or the
> > whole
> > barrel will come out of the board with the pin. Rarely (I have never
> > seen) will the solder joint itself fail. Best of luck....
> >
> > > -----Original Message-----
> > > From: Alan Kreplick [SMTP:[log in to unmask]]
> > > Sent: Friday, June 26, 1998 9:42 AM
> > > To: [log in to unmask]
> > > Subject: [TN] Thru-hole Reliability
> > >
> > > I have a board that is .250" thick with 34 layers with 1 and 2 oz.
> > > copper. I
> > > have been able to achieve a 25-50% hole fill both by hand and wave
> > > soldering.
> > > The only component that is being soldered are sixty-four tantalum
> > > capacitors
> > > (assembled with a partial clinch).
> > >
> > > We normally follow IPC's 75% hole fill guideline.
> > >
> > > Is the solder connection reliable both electrically and mechanically
> > > (we build
> > > ATE products that do not require thermal cycles or vibration tests)?
> > >
> > > Is 25-50% of .250 (.062"-.125") hole fill more reliable than a 75%
> > > hole fill on
> > > a .060" board (.045 hole fill)? I've used this argument to say that
> > > it is more
> > > reliable even though it does not meet the 75% hole fill criteria.
> > >
> > >
> > > Thanks for any help,
> > >
> > >
> > > Al Kreplick
> > > Sr. Mfg. Eng.
> > > Teradyne, Inc.
> > > 617-422-3726
> > >
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