To all,
I thought for a moment we were going to have an old fashioned duel between
David and Graham.It would have been a shame to loose all that intellect and
humor in one fell swoop.We would have missed Graham, also( just kidding
Graham).
Everybody has made valid points.1B31and other types of AR coating are
glorified dust bags.I can say that because I developed that material and
qualified it and it's process for our Aerospace use.I have qualified other
materials and processes over the years(SR,UR and XY) and even re-qualified
newer versions of 1B31(lower VOC,,etc.),but the Conformal Coat of choice is
AR.We have to support rework and a product life of plus 25 years.You(and
almost anybody)can completly strip the coating off, do the repairs, clean
the assembly, verify an acceptable level of cleanliness and re-coat the
assembly.Since AR is basically an acrylic adhesive, it is amazing how clean
an assembly gets when it is stripped.
We realize the shortcomings of AR and deal with it in the design and use.We
choose other coatings when appropriate and also do combinations so as not to
penalize the whole assembly because a few problem areas.The key is to
understand the end use environment and choose the coating that has the
widest processing window, tolerates rework and functionally does the job.
I think it's an old Iowa proverb that says"Why wear a latex suit, when a
dust bag will do just fine".
Dewey
> -----Original Message-----
> From: David Douthit [SMTP:[log in to unmask]]
> Sent: Wednesday, March 24, 2004 6:13 PM
> To: [log in to unmask]
> Subject: Re: [TN] acyrlic coating deformed BGA balls
>
> David,
>
> Thank you for the mediation.
>
> Given the rapid changes occurring in the electronics industry matching
> coatings to the correct application for a given use environment has become
> a daunting complex challenge. It's significance can not be over estimated
> or ignored.
>
> David A. Douthit
> Manager
> LoCan LLC
>
>
>
> David D. Hillman wrote:
>
> >Hi Gang! I'll take a swipe at finding the middle ground on this one! Both
> >Graham and Dave are correct from each of their perspectives - Graham has
> a
> >multitude of real life use data of AR type conformal coating being used
> in
> >a number of severe use environments successfully and Dave has been
> involved
> >in some of the "uglier" aspects of when AR type conformal coating is an
> >incorrect application for a given use environment. Collins published a
> >paper on an investigation comparing AR and Paralyene conformal coating
> >types with BGA style components. The investigation shows both coating
> types
> >work well and the application method (as other TechNetees have mentioned)
> >can be critical in impacting solder joint reliability. Steve - if I send
> a
> >copy of the paper can you put it out on your website?
> >
> >Dave Hillman
> >Rockwell Collins
> >[log in to unmask]
> >
> >
> >
> >
> > Steve Gregory
> > <[log in to unmask] To: [log in to unmask]
> > M> cc:
> > Sent by: TechNet Subject: Re: [TN] acyrlic
> coating deformed BGA balls
> > <[log in to unmask]>
> >
> >
> > 03/23/2004 10:01
> > PM
> > Please respond to
> > "TechNet E-Mail
> > Forum."; Please
> > respond to
> > SteveZeva
> >
> >
> >
> >
> >
> >
> >
> >Hi Graham,
> >
> >I must say, I find your comments pretty harsh. David Douthit has many
> >publications that are accepted as factual, and he always back-ups
> >everything that he
> >says with documentation that proves what he says is fact.
> >
> >If you can show, or lead us to anything that he says is false, please
> >provide
> >us links, or anything else that would substantiate what you are saying...
> >
> >Best regards,
> >
> >-Steve Gregory-
> >David
> >
> >Your comment is grossly misleading.
> >
> >You cast aspersions on the intelligence of the users
> >
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