Yes. The problem is that the old fogies have passed on the bias towards US cleaning to young fogies who may not understand the details that you pointed out. There is a LOT of more recent work out there. Crest has a lot of papers on the subject on their website that I posted in my original response. Here is a link to one in particular. Dr. Awad has written a number of papers on the subject:
http://www.crest-ultrasonics.com/wp-content/uploads/2013/06/lit-ultrasonic-cavitations.pdf
Thanks
dean
-----Original Message-----
From: Mike Fenner [mailto:[log in to unmask]]
Sent: Tuesday, March 31, 2015 10:44 AM
To: 'TechNet E-Mail Forum'; Stadem, Richard D.
Subject: RE: [TN] Leaded component, lead pull test
Industry received wisdom persists so this keeps coming up.
I can't recall complete details after >35 years, but that's how long since I read the first investigative paper (by I think Marconi/GEC Labs here in UK) which showed that the then fixed frequency u/s cleaners did not damage wire bonds, but might cause poor quality - that is to say short service life - bonds to fail. So that would be a good thing if it happened you would think.
Since then the U/S frequency range has changed and is swept to avoid possibly damaging resonances building.
Perhaps it's so long ago that only a few old fogies remember. Certainly pre-internet and therefore for many before the world was created :) Which suggests there must be more recent work.
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Monday, March 30, 2015 5:14 PM
To: [log in to unmask]
Subject: Re: [TN] Leaded component, lead pull test
That is correct. Ultrasonic energy alone, unless associated with a resonant energy over a period of time longer than a couple of milliseconds, does not typically hurt solder joints or wirebond connections.
If it did, you would not be able to use a Sonoscan or other similar acoustical scanning equipment. Nor could you use standard wirebonding or diebonding equipment, which operate in the ultrasonic range.
But these are used routinely in assembly and inspection of electronics at both the component and assembly level! One must understand that the energy level, sweep frequency, and length of time are miniscule in comparison to US cleaning equipment that allows cavitation to occur (not intended for electronics use).
For electronic assemblies, an "evil association" is now linked to any ultrasonic energy use in electronics, but the truth of the matter is that only cavitation from non-staggered US energy in cleaning equipment ever hurt wirebonds, solder joints, or diebonds.
On equipment intended to clean carburetors!
Many savvy electronics manufacturing providers use large-scale US cleaners as their primary cleaning process on "delicate" electronics on a daily basis with no ill effects or loss of reliability whatsoever.
This equipment is designed to do no harm to electronics.
Unfortunately, because some large customers still have an ignorant, irrational, and irremovable attitude (reflex reaction) towards the word "ultrasonic", many potential users who could benefit from the superior performance (and lower cost) of saponified ultrasonic cleaners, don't.
http://www.crest-ultrasonics.com/optimum-console/
But you still need to qualify, qualify, qualify.
dean
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Monday, March 30, 2015 10:39 AM
To: [log in to unmask]
Subject: Re: [TN] Leaded component, lead pull test
Hi Victor-
Now there's an interesting question! You should be arrested for cruel and unusual punishments to solder joints! Have you already researched the reservoir of knowledge which Inge bestowed on us? Inge put an incredible range of information in his DropBox account and gave anyone who wished access. I made a full copy. Lots of good stuff...
Now for the "off the cuff" answer:
It's kind of hard to get a decent amount of ultrasonic power into a solder joint unless you deliberately hit it with one of those Westbond monsters.
Otherwise, the ultrasonic waves get eaten up by all of the dissipative mechanical arrangements in most structures. I THINK I recall seeing passives SMT soldered directly to the piezoceramic stacks on the end of the driving horn for an ultrasonic welder, so that would suggest no problem.
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Monday, March 30, 2015 10:39 AM
To: [log in to unmask]
Subject: Re: [TN] Leaded component, lead pull test
Fellow TechNetters:
Thanks to all who contributed with their experience. What a wealth of
knowledge is out there. Never seems to amaze me. On another note, will
an ultrasonic environment loosen the component lead so that it will works itself out of the LF solder joint.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
Sent: Monday, March 30, 2015 8:46 AM
To: [log in to unmask]
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 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
> indestructible.
>
> 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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