Thanks, Dave. That certainly CLINCHES it for me!
From: David Hillman [mailto:[log in to unmask]]
Sent: Monday, March 30, 2015 9:46 AM
To: TechNet E-Mail Forum; Wayne Thayer
Subject: Re: [TN] Leaded component, lead pull test
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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