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Date: | Mon, 10 Nov 2008 13:32:43 +0000 |
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Hi John
Yes!
The reason that no-clean fluxes pass old SIR tests is because they
volatalize at temperatures ~>40DegC but the SIR used to call for
85DegC/85%RH. If they are tested at 40DegC/90%RH as per the new SIR
methods, you will probably see a different story. HP found that and
reported on it - and many others also, but I am not sure they have
published their problems.
No clean flux = very low or no solids = higher preheat = more
absorbtion into a swollen laminate = possible electro-chemical
reliability issues.
Lead-free = much higher process temperatures = a bigger problem?
Graham Naisbitt
On 9 Nov 2008, at 15:32, John Goulet wrote:
> Is there any information on products with No-Clean flux being
> effected by moisture over a period longer than that tested in SIR
> tests with the SIR comb test coupons? Some customers make products
> for vehicles and toys that are subject to more humid conditions. The
> No-Clean fluxes used always pass SIR which have high resistance
> values even after 196 hours. However if the humidity levels rise
> and fall but never to the point of drying out the moisture. I
> thinking that the humid spring and summer months could be a problem
> if not sprayed with a conformal coat. The other situation I'm
> testing is when a moisture sensitive part is used. Tests on three of
> the boards showed that the moisture sensitive part was dragging the
> surface insulation down. When I localized the heating to this part
> with a small Leister heat gun, the resistance across the battery
> terminals with the battery removed went back to infinity. Usually
> the moisture sensitivity is a factor relative to the SMT reflow proc!
> ess and
> not an issue in operation. Any info on this? PS this batch was the
> first ones using Pb-Free solder paste and that means I'll have to
> check if the BOM changed to a different RoHs version of this special
> moisture sensitive part.
>
>
> -------------- Original message --------------
> From: John Burke <[log in to unmask]>
>
>> FYI Werner has developed an Accelerated reliability model for
>> SAC405/305
>> solder joint creep-fatigue. Details below
>>
>>
>> John Burke
>>
>> (408) 515 4992
>>
>>
>> -----Original Message-----
>> From: Leadfree [mailto:[log in to unmask]] On Behalf Of Werner
>> Engelmaier /*
>> Sent: Friday, November 07, 2008 2:15 PM
>> To: [log in to unmask]
>> Subject: [LF] Accelerated reliability model for SAC405/305 solder
>> joint
>> creep-fatigue
>>
>> Hi all,
>> Just to let everybody know, I have developed a creep-fatigue model
>> for
>> SAC405/305 solder joints. It will be published in a presentation at
>> the
>> IPC/JEDEC
>> Conference on Transitioning to Lead-Free: Strategies for
>> Implementation on
>> December 8 to 10, 2008 in Dallas, TX.
>>
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>> or
>> 847-615-7100 ext.2815
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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
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