How true.
I guess in the simplest of perspectives (something I'm better at) we are for
the most part creating a Tin - Copper interface. From that perspective we
haven't changed anything, so why throw out the 50? years of development for
the implementation of Lead Free and elimination of lead in the mix? It
still is Tin and we have plenty of that in lead free. We have variations in
the surface coverage/plating over the materials that we have always used.
The iron base lead types like alloy 42 and Kovar have all been around
forever.
I think that the key is visual appearances (repeat - doesn't look like it
used to) is an obstacle that can be accomplished with training. The rest of
the criteria should still apply.
Mel Parrish
Director, Training Materials and Resources
Soldering Technology International
102 Tribble Drive
Madison, AL 35758
256 705 5530
256 705 5538 Fax
[log in to unmask]
www.solderingtech.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of joyce
Sent: Thursday, July 17, 2003 12:41 PM
To: [log in to unmask]
Subject: Re: [TN] High temp pastes for wave soldering...
I thought heel support (wetting angle) do have critical effect on the
crack initiation when early 610 and 001 drafted. There are many thermal
shock data regarding the geometry of the heel and toe wetting angle vs.
on/off cycles based on the field data and HAST (too long ago, can't
remember who did what). Being said that, current warrantee is only 1
year possibly without any extension. Everybody (even Mil) only
interested infant failure (burn-in cycle)... I guess it means nothing
when you talking about long term failure=thing in the past (disposable
cell phone every 6 month, who cares....as some of leadfree guys point
out)...
jk
P.s. dave, don't jump in.....
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of
>Dave Hillman
>Sent: Thursday, July 17, 2003 12:10 PM
>To: [log in to unmask]
>Subject: Re: [TN] High temp pastes for wave soldering...
>
>
>Hi folks! Guy - Mel did a much better response than I was
>going to put together! You are right - having a great wetting
>angle(s) is not end-all evidence that a good solder joint has
>been formed, just as having a bright and shiny solder joint
>does not always indicate good solder joint formation. However,
>many folks use the combination of wetting angles, solder joint
>geometry, and surface topography as a set of solder joint
>formation indicators. The Pbfree soldering process(es) will
>need to be evaluated to understand if the same criteria we use
>today to "measure" solder joint formation is going to still be
>valid. The 610 and 001 committees are working diligently to
>answer that question. We may need to recalibrate ourselves -
>the introduction of immersion surface finishes has force the
>industry to rethink having complete solder flow on a surface
>pad as the HASL finishes have better flow but the overall
>solder joint quality is the same. Lots of work ahead of us!
>
>Dave
>
>
>|---------+---------------------------->
>| | Mel Parrish |
>| | <mparrish@SOLDERI|
>| | NGTECH.COM> |
>| | Sent by: TechNet |
>| | <TechNet@listserv|
>| | .ipc.org> |
>| | |
>| | |
>| | 07/17/2003 09:05 |
>| | AM |
>| | Please respond to|
>| | "TechNet E-Mail |
>| | Forum."; Please |
>| | respond to Mel |
>| | Parrish |
>| | |
>|---------+---------------------------->
>
>>--------------------------------------------------------------
>----------------------------------------------------------------|
> |
> |
> | To: [log in to unmask]
> |
> | cc:
> |
> | Subject: Re: [TN] High temp pastes for wave
>soldering...
> |
>
>>--------------------------------------------------------------
>----------------------------------------------------------------|
>
>
>
>
>Guy,
>We are in the process of looking at the criteria for 610 and
>001. Some thoughts-and discussion. Much of the content and
>criteria for filleting accomplished to a termination is based
>upon physical properties of the termination or attachment. A
>case in reference is the lack of requirement for a toe fillet
>in Gull Wing leads per 001C, but the specification of a fillet
>in the Heel area even though it's minimal. If in fact we did
>not have a heel fillet, the lead geometry could contribute to
>a separation failure, even with adequate fillet transition of
>the termination in other areas. Consider that all of the lead
>configuration dimensions and design attributes commonly used
>today were created for performance with SnPb alloys. We don't
>have lead designs created for Pb free specifically, and even
>if we did there is certainly a significant number of
>combinations that would be necessary to cover the field. This
>being the case, fillets where fillets were required in the
>past should still be required unless and until we have design
>definitions for each of the lead/board/solder combinations
>that fall within Lead Free. Surface appearance of the solder
>connection criteria went out of the standards 20 years ago, so
>that should not be an issue except for education of inspection
>when "it looks different" becomes an issue. Fillet transition
>(commonly wetting) is still another issue. We have used Sn96
>in production soldering for as many years as I've been in the
>industry with success based upon the standardized criteria.
>It is a Lead Free alloy. Should we, at this transition time,
>eliminate the criteria to say that wetting to the terminations
>is not required? I certainly hope not. In the exception cases
>where fillets do perform in operation even though they don't
>wet to the surface (such as when Inert atmosphere is not
>employed or Flux performance is minimal) there may be
>justification for exception to standard requirements, but at
>this time that might require sample testing to determine the
>success of the metallurgy within the attachment. Barring that
>we have the appearance of a fillet transition (wetting) to
>determine success of the process to attach to the surfaces
>involved. It's still a good indication for the ability of the
>surface to accept the metallurgical bond.
>
>Best regards,
>Mel
>
>
>Mel Parrish
>[log in to unmask]
>www.solderingtech.com
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Guy Ramsey
>Sent: Thursday, July 17, 2003 7:41 AM
>To: [log in to unmask]
>Subject: Re: [TN] High temp pastes for wave soldering...
>
>
>Why do we care what the wetting angles are? (Indirect overhead
>question)
>
>SnPb on SnPb finish yields solder contact angles we expect, we
>infer that certain process outputs exist because of the
>appearance of the solder joint.
>
>With Pb free finishes and SnPb finishes we still expect the
>same appearance but is the inference still true?
>
>Now, add Pb-free solder to the mix. Why would we expect the
>contact angels and solder joint geometries to be the same. The
>process inputs are different.
>
>I feel the more important, and largely unanswered question,
>remains. Given the variety of lead and board finishes, and
>variety of Pb-Free solder alloys, changes in performance from
>small shifts in alloy composition . . . Can we expect to have
>a single visual acceptance criteria, acceptance criteria that
>are data driven and performance based.
>
>I have observed that SnAgCu solder wets Immersion silver
>plated leads quite differently than PdNi finishes. What looks
>"normal" on the latter would definitely be a defect on the
>former. And neither of these would come close to what we call
>"target" today.
>
>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave
>> Hillman
>> Sent: Wednesday, July 16, 2003 1:15 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] High temp pastes for wave soldering...
>>
>>
>> Hi Mel and crew! Sorry for the lack of response - been chasing
>> alligators in the swamp and they seem bigger than normal this week.
>> Mike F. and Gebbard hit the nail on the head - because of the higher
>> temperatures of a Pbfree soldering process the thermal stability of
>> many of the current fluxes is pushed to the limit (and/or over the
>> cliff). We are going to need to rely on the flux supplier's
>> expertise in reformulating our fluxes to have better thermal
>> stability and hopefully have the same level of
>> noncorrosivitivity. The NIST webpage/database has a good
>> listing of Pbfree surface tension values if anyone is
>> interested in alloys properties type information. One
>> industry concern which has been expressed in a number of
>> conferences is what changes in our expectations of "assembly
>> cleanliness" do we need to be prepared for as the flux
>> formulations are adjusted. If we expect to achieve the same
>> wetting angles and solder joint geometries we'll have to make
>> adjustments in our assembly materials.
>>
>> Dave Hillman
>> Rockwell Collins
>> [log in to unmask]
>>
>
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