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May 2010

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Subject:
From:
Jack Olson <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jack Olson <[log in to unmask]>
Date:
Fri, 28 May 2010 10:57:32 -0500
Content-Type:
text/plain
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text/plain (182 lines)
Yes, the STII calculation combines multiple factors to get
a nice indicator of overall performance, but do bare board
fabricators know what STII is?
Are drawings actually specifying minimum STII as part of
the fab notes?
Jack
On Fri, May 21, 2010 at 11:18 AM, Paul Reid <[log in to unmask]>wrote:

>  I think that the material slash sheet are good general indicators but
> also provide challenges in selecting a good material. Werner’s STII method
> helps focus the materials selection process.
>
>
>
>
>
> Sincerely,
>
> Paul Reid
>
>
>
> Program Coordinator
>
> PWB Interconnect Solutions Inc.
> 235 Stafford Rd., West, Unit 103
> Nepean, Ontario
> Canada, K2H 9C1
>
> 613 596 4244 ext. 229
> Skype paul_reid_pwb
> *[log in to unmask] <mailto:[log in to unmask]<[log in to unmask]>
> >*
>
>
>  ------------------------------
>
> *From:* Jack Olson [mailto:[log in to unmask]]
> *Sent:* May 21, 2010 11:29 AM
> *To:* Paul Reid
>
> *Cc:* TechNet E-Mail Forum
>  *Subject:* Re: [TN] My first RoHS circuit board!
>
>
>
> That seems like very good advice, thanks for sharing it.
>
> I'm happy to report that my crisis of confidence has passed.
>
>
>
> Several people wrote to me to say that the materials my supplier suggested
> (S1000-2 and IT-180) are rated for /126 and /129, even though the data
> sheets I was given say /99 and /24.
>
> I now have newer data sheets for both materials, and they do say /126 and
> /129 on them
>
>
>
> I feel like a goofball getting everyone involved when I could have looked
> it up myself, but I never would have suspected my supplier's data sheets
> could be out of date!
>
> thanks,
>
> Jack
>
>
> .
>
> On Fri, May 21, 2010 at 9:30 AM, Paul Reid <[log in to unmask]>
> wrote:
>
> Hi Jack,
>
> Our experience has been that it is not a good idea to ask a fabricator
> to use a material with which they have no experience unless they are
> willing to test the material and make various process changes to
> maximize the PWBs robustness. If you force a material on a fabricator
> then you own the results, good or bad. If the fabricator suggests a
> material then they can be held accountable for the results.
>
> We have seen dicey cured material that tested reliable for lead free
> assembly in low layer count, low aspect ratio PWBs. The default lead
> free, FR4 material, however, is phenolic cured because in general
> phenolic cure materials are usually more robust in HDI, RoHS compliant
> applications.
>
> I know, and I believe Werner and Dewey would agree, that some high Tg
> materials offer no reliability advantage over lower Tg materials. Tg
> should be considered an indicator but not a definer of overall material
> robustness. I am beginning to think elasticity and the ability to
> maintain elasticity after the thermal excursions associated with lead
> free assembly and rework may be just as important as Tg and Td.
>
> In challenging applications fabrication, material, design and
> construction all need to be maximized is order to achieve acceptable
> reliability.
>
> All that being said we promote reliability testing of representative
> coupons to determine which materials are best suited for an application
> particularly with challenging designs and high reliability expectations.
>
>
> Sincerely,
> Paul Reid
>
> Program Coordinator
> PWB Interconnect Solutions Inc.
> 235 Stafford Rd., West, Unit 103
> Nepean, Ontario
> Canada, K2H 9C1
> 613 596 4244 ext. 229
> Skype paul_reid_pwb
> [log in to unmask] <mailto:[log in to unmask]>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
>
> Sent: May 20, 2010 9:03 PM
> To: [log in to unmask]
>
> Subject: Re: [TN] My first RoHS circuit board!
>
> Thanks for the advice (everyone!)
>
> Here's an update if anyone is interested:
>
> I sent a sample fab dwg to our primary supplier (in China) with notes
> that incorporated several of your recommendations (the main one being
> material /126 170Tg 330Td 30minT288) to see if it would cause them any
> problems before I send them the real order. They looked at it and said
> "No
> Problem. Our default material meets those requirements"
>
> So I told them that since I'm trying to learn about his I would like to
> know
> what kind of material it was, and could they send me a data sheet.
>
> Well, they sent a data sheet for something called S1000-2 which it says
> right on the data sheet is /99, but the parameters are 175Tg 335Td
> 10minT288
> So I wrote back and asked if they had another material that is more
> robust,
> and they sent me data for a material called IT-180 which it says is /24
> Tg180 Td350 >60minT288(?)
>
> I really don't think they are trying to be deceptive, but that they
> honestly
> think the only thing that matters is the Tg and Td numbers. And those
> numbers look pretty good!
>
> So now I'm wondering how hard I should push to get them to literally buy
> /126, and if by forcing them to use a material they aren't familiar
> with, if
> there will be other problems related to drilling, or desmear or plating
> or
> routing or whatever could be different from the /99 they are used to. Is
> there a "learning curve" with these materials?
> Jack
>
> .
>

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