Hi Werner-
You may recall I brought this issue up a few months ago too. The basic question I have is
If solder joint height is important for longevity/reliability, why aren't there IPC guidelines/requirements for them? As noted previously, tungsten rods are available in almost any diameter and they can be used as a simple "quick check" tool for this application.
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Tuesday, July 20, 2010 1:01 PM
To: [log in to unmask]
Subject: Re: [TN] solder joint height
)Dale,
The answer is a qualified YES.
What are the sizes of these ceramic chip components and the Alloy-42-dominated SOT? When do you see those cracks [thermal history]? What are the QUAL requirements?
What is the real use environment?
I take it this is SnPb solder.
Regardless of these answers, a greater SJ height enhances reliability-you may want to take a look at the attached reliability article (Engelmaier,W., "Achieving Solder Joint Reliability in a Lead-Free World, Part 1," GlobalSMT & Packaging, Vol. 7, No. 6, June 2007, pp. 40-42). .
Werner
-----Original Message-----
From: Hart, Dale L CTR USAF AFMC AFRL/RXSA <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Jul 20, 2010 12:51 pm
Subject: Re: [TN] solder joint height
Air Force often uses CCA's as circuit card assemblies, sorry for the confusion.
The type of components are surface mount resistors, capacitor and I believe a
SOT with gull wing leads.
My problem is do I suggest their solder joint height isn't sufficient enough to
ensure a reliable assembly on an aircraft.
dlh
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Tuesday, July 20, 2010 11:19 AM
To: [log in to unmask]
Subject: Re: [TN] solder joint height
Hi Dale,
Do you mean CGA's [column grid arrays]? If not, what do you mean by cca?
610, Class 3 or otherwise, only addresses quality, not reliability-for that you
need to go to IPC-D-279.
While the absence of solder fillets can reduce fatigue life, the presence of
fillets, 'robust' or otherwise, does not have any positive first-order impact.
However, solder joint height does.
You may be looking at IMC crystals.
Werner
-----Original Message-----
From: Hart, Dale L CTR USAF AFMC AFRL/RXSA <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Jul 20, 2010 9:23 am
Subject: [TN] solder joint height
We have been doing a some analysis of cca's for the Air Force consisting of
SMT. The visual inspection of the solder joints looks very good all
characteristics above the suggest minimum for class 3 of 610. The solder
fillets in some instances could be characterized as being robust. In
cross-sectional analysis however, the solder joint height of the components
electrical termination above the land has been perhaps 0.025 mm to the point
of needing a SEM to look at the land-solder-component lead interface.
Closer examination in these areas revealed small cracks in the grain
boundaries. I used the term grain boundaries because the solder in these
areas do not resemble the colonies observed in the bulk solder of the
fillet. In some of these instances the land is often deformed in the shape
of the component lead.
Would these joints although stronger be more susceptible to fatigue or
overload failure?
What are the implications if these cca's are encapsulated?
What suggestions could be offered to the manufacturer?
Dale L. Hart
Universal Technology Corporation (UTC)
Failure Analysis
1270 North Fairfield Road
Dayton, Ohio 45432-2600
(937) 656-9165
Fax (937) 656-4600
Email: <mailto:[log in to unmask]> [log in to unmask]
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