Hi Gause,



I believe that I can give you some direction on Survivability testing. It is a new method we have been developing with some of our customers. 



I am concerned that we are going beyond the scope of this forum however. I suggest we establish a direct line of communication for the specifics of IST testing. I would gladly continue this discussion with interested parties off the IPC forum. We at PWB are sensitive to conflicting interests. Please consider me a ready resource for PWB reliability testing but IST testing, criteria, cost benefits etc should be a direct communication with PWB Inc.



Could you contact me directly?



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 HuGause

Sent: Monday, January 14, 2008 9:48 PM

To: [log in to unmask]

Subject: Re: [TN] IST for lead free assembly PCB monitoring





Hi Paul and DW,

 

Thank you very much for your response and informative input.

 

You are right, we plan to precondition 6x 260 degree C at IST tester (NOT assembly reflow oven) prior to 220 degree C IST cycling. It's for survivability testing purpose before PCB ship out. Currently, we have limit data to setup a proper pass/fail criteria for the test to failure.The IST coupon were built at the panal border of actual part, then, the IST cycling result will be affected by the stackup structure, min. via holes size, copper thk, aspect ratio.... we are considering 20 cycl min. as criteria.

 

do you have any idea of how to setup the pass/fail criteria?

 

Best Regards,

 

Gause

 

> Date: Mon, 14 Jan 2008 07:43:22 -0800> From: [log in to unmask]> 

> Subject: Re: [TN] IST for lead free assembly PCB monitoring> To: 

> [log in to unmask]> > Gause,> I second Paul's comments. Been there, done 

> that. Got the T-shirt.> > I understand your interest in testing to 

> fail faster by running IST to > failure at reflow temps. However, you 

> should also be thinking about > hierarchy of failure above Tg vs below 

> Tg.> > Test to fail above Tg is more of a reflow survivability test 

> than a > reliability test (unless you've done the work to establish 

> that fails above > and below Tg correlate well).> > Test to fail above 

> Tg may stimulate different failures than with > preconditioning above 

> Tg, followed by test to fail below Tg. On the other > hand, it may not 

> -- depending on the pwb design. It needs to be > proven/demonstrated 

> to be true before shifting to the high temp test.> > Paul can expand 

> on this thought with more authority than I.> > cheers,> dw> > > > At 

> 06:38 AM 1/14/2008, Paul Reid wrote:> >Hi Gause,> >> >We recommend 

> that you precondition the IST coupons to simulate assembly > >(3X) and 

> assembly and rework (6X) prior to testing at 150°C. Tin/lead > 

> >preconditioning is to 230°C; lead free preconditioning is at 245°C 

> or > >260°C. Preconditioning at 260°C is the default lead free 

> temperature. > >Preconditioning on the IST tester will give a tighter 

> data set (and has > >better control) than preconditioning in a thermal 

> oven but methods are used.> >> >The reliability data we have is based 

> on 150°C testing (hundreds of > >thousands or tests) so 150°C is the 

> default test temperature. You can > >establish a reliability profile 

> for your company at any test temperature.> >> >Most IST reliability 

> testing is performed at 150°C. Microvias are tested > >at 190°C 

> (powering on the microvia). Flex circuits are tested at 210°C. > 

> >Survivability testing is preformed at 220°C or above. Field life 

> testing > >is performed at three temperatures usually just below Tg 

> (ex. 150°C, > >160°C and 170°C).> >> >You can expect that a well 

> made circuit will have a 50% reduction in > >reliability due to 

> lead/free assembly and rework at 260°C. Because of > >that 

> observation many people are trying to reduce the assembly temperature 

> > >to 245°C if at all possible.> >> >It is important to note that 

> delamination extends thermal cycles to > >failure so you have to be 

> vigilant to monitor for delamination and > >crazing. We monitor for delamination and crazing electronically and > >confirm with microsections. Delamination is dramatically increased with > >lead free assembly and rework. Grid size has an inverse relation to > >propensity to delaminate.> >> >Werner has observed, and I concur, that lead free assembly has had a large > >impact on electronic reliability and the reliability of circuit boards has > >been the hardest hit. It is important to do your home work when you switch > >to lead free assembly. Design, material and copper quality work must all > >be optimized to meet the lead free challenge.> >> >Please feel free to contact me directly if you need more information.> >> >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 HuGause> >Sent: Friday, January 11, 2008 1:49 AM> >To: [log in to unmask]> >Subject: [TN] IST for lead free assembly PCB monitoring> >> >> >TechNeters,> >> >> >We used IST data for PCB supplier process health monitoring, for > >conventional stardard Tin/lead assembly, we follow PWB recomeend cycling > >temperature from room temperature to 150 degree C. Now, our product > >transition to lead free assembly,the assembly reflow temperature go up to > >245--260 degree C. We are considering to increase the IST cycling > >temperature to 230 degree C. The pass/fail criteria as 20 to 50 cycles.> >> >I would like to know anyone has the experiece of higher cycling > >temperature for IST, and any comment on the peak temperature and criteria. > >Thanks.> >> >> >Best Regards,> >> >> >Gause Hu> >> >_________________________________________________________________> >MSN 中歇网，最歰时尚生活资讯，白领聚集门户。> >http://cn.msn.com> >> >---------------------------------------------------> >Technet Mail List provided as a service by IPC using LISTSERV 15.0 To > >unsubscribe, send a message to [log in to unmask] with following text in the > >BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or > >(re-start) delivery of Technet send e-mail to [log in to unmask]: SET > >Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: > >send e-mail to [log in to unmask]: SET Technet Digest Search the archives of > >previous posts at: http://listserv.ipc.org/archives Please visit IPC web > >site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional > >information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 > >ext.2815> >-----------------------------------------------------> > ---------------------------------------------------> Technet Mail List provided as a service by IPC using LISTSERV 15.0> To unsubscribe, send a message to [log in to unmask] with following text in> the BODY (NOT the subject field): SIGNOFF Technet> To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)> To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest> Search the archives of previous posts at: http://listserv.ipc.org/archives> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815> -----------------------------------------------------

_________________________________________________________________

天凉了，添衣了，心动了，“七件”了

http://get.live.cn