Graham,
Dave and Julia bring up good points, but I'll tell you where I am coming from. We have used these so-called Airborne connectors and after sorting and screening for a variety of reasons, we realized the final gold thickness was somewhere between 30 and 50 micro-inches.
With a controlled process and meeting all other acceptance criteria(less than 4% final gold content, homogenous uniformity of the final alloying) for establishing a Class 3+ solder joint, we have no confirmed failures of connectors that were not pre-tinned prior to placement and reflow.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Thursday, August 16, 2012 8:36 AM
To: [log in to unmask]
Subject: Re: [TN] gold removal question - to remove or not?
Hmm...
Firstly, I should clarify - I'm talking about PTH parts, and while I cite an Airborne connector there are numerous other vendors we get gold leads from - part of the joys of military stuff.
The problem I have is making an assumption that we are OK because we wave solder it. I am uncomfortable making that call without a good basis to do so.
J-STD-001E says I don't have to tin:
If there is documented objective evidence, available for review, that there are no gold related solder embrittlement issues,
or other metallic surface finish solder joint integrity problems (e.g., with Sn or SnBi) associated with the soldering process
being used.
And when I tin:
A double tinning process or dynamic solder wave may be used for gold removal prior to mounting the component on the
assembly.
Note the word "prior". Just because I am wave soldering the part I'm not absolved from the requirement. Hence, per J-STD-001 I have three options:
1) Ensure less than 100 ìin of gold plating
2) Collect and document evidence that the process being used will not result in gold embrittlement issues
3) Tin the parts before assembly
Am I missing something here? I cannot be J-STD-001 compliant without doing one of those actions, as I read it. Ref: J-STD-001E, section 4.5
regards,
- Graham
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Wednesday, August 15, 2012 9:54 PM
To: [log in to unmask]
Subject: Re: [TN] gold removal question - to remove or not?
:) Dewey,
Was that intentional? Wrong use of the word "disillusionment".
Graham,
I agree with Dewey that it is certainly overkill for PTH parts. For SMT parts, have you done the math to figure out % Au in a completed SMT joint with different thicknesses of gold?
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask] <mailto:[log in to unmask]> ] On Behalf Of Whittaker, Dewey (EHCOE)
Sent: Wednesday, August 15, 2012 3:44 PM
To: [log in to unmask] <mailto:[log in to unmask]>
Subject: Re: [TN] gold removal question - to remove or not?
Graham,
OK, we'll consider you a dip until proven otherwise. I hope you are talking about SMT components? There is a good case for not pre-tinning (sounds more technical than dip) PTH parts where there is a reasonable expectation of disillusionment of the gold in your flow solder process.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask] <mailto:[log in to unmask]> ] On Behalf Of Graham Collins
Sent: Wednesday, August 15, 2012 12:16 PM
To: [log in to unmask] <mailto:[log in to unmask]>
Subject: [TN] gold removal question - to remove or not?
Hello Technet
I'm in the midst of a debate about gold removal. Our policy on component leads is to double dip tin all gold. J-STD-001 says I do not have to do it if there is less than "2.54 ìm [100 ìin]" of gold, but is it realistic to operate on that basis? For example, looking at an Airborne brand connector I find the spec sheet says that there will be 50 ìin gold, minimum. Which is not totally helpful as it does not tell me maximum. I'm assuming given the price of gold that they aren't looking to put a lot more than the minimum on, but how controllable is the process? Could we check the thickness once and assume we are safe?
(and as you can tell from my phrasing I'm of the more conservative camp on this one, still dipping the parts until proven wrong)
regards,
Graham Collins
Halifax Production Engineering
(902) 873-2000 ext. 6215
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