Hi Wayne - But I didn't say "solder" was indestructible, plated thru holes
are indestructible. The clinched lead acts as the mechanical connection and
the solder acts as the electrical connection. I completely agree with you
that solder is a very poor mechanical material - any time we use a material
that actively recrystalizes in its use environment, we had better be very
good with our designs. As an industry, we "re-learned" that lesson when
Leadless Ceramic Chip Carriers (LCCCs) were introduced and in some sense,
we again went back to school with the introduction of BGAs (we all got "Fs"
for LCCCs and "B-" for BGAs).  As you detailed, good design uses materials
intelligently within their limits with an understanding of the product use
environment constraints. Not understanding the limits of a material can
result in a predicted failure, as demonstrated by your PTH spring example.

Dave

On Mon, Mar 30, 2015 at 8:30 AM, Wayne Thayer <[log in to unmask]> wrote:

> I can't agree that "Plate thru hole solder joints are truly
> indestructible."
>
> Solder is a strange material to use for mechanical connection. As a metal,
> it
> is pretty weak under the best of circumstances. Depending on temperature
> and
> rate of stress, it is EXTREMELY weak. Years ago we had a mechanical
> engineer
> who used a through-hole solder joint to maintain stress on a spring. Held
> for
> about a year! I suggest you repeat that experiment, with the through hole
> solder joint suspending a weight about 600mm above your keyboard and let us
> know how long it lasts!
>
> But we all design modules which depend on the solder as a mechanical
> connection. As long as the time constant of the stress is low enough (shock
> loads, diurnal temperature stress, etc.), it works pretty well when
> compared
> with organic adhesives (until grain growth and cyclic fatigue do their
> work).
>
> Wayne Thayer
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
> Sent: Monday, March 30, 2015 8:47 AM
> To: [log in to unmask]
> Subject: Re: [TN] Leaded component, lead pull test
>
> Hi Victor - not much data in the public domain on that topic. About the
> best
> you can do is get a copy of the International Tin Research Institute's
> Publication 656 titled "Solder Alloy Data". Publication 565 contains
> tensile,
> fatigue and shear data for a number of solder alloys over various
> temperature
> and stress/strain rates. The testing we completed back in the early 1990's
> at
> Rockwell Collins on plated thru hole strength nearly always resulted in
> failure of the plated thru hole/laminate rather than the solder joint
> itself
> using slow tensile speeds (unpublished). Plate thru hole solder joints are
> truly indestructable.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Fri, Mar 27, 2015 at 3:10 PM, Victor Hernandez <
> [log in to unmask]> wrote:
>
> > Fellow TechNetters;
> >
> >    Does anyone have information on the following:
> >                Finish hole size, lead diameter, solder type, thickness of
> > board and lead length.   How much force does it require to pull out a
> lead
> > from the solder joint.   Will the lead come out cleanly or elongated and
> > snap,
> >
> > Victor,
> >
> >
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