With also much depending on the construction and geometry - CTE can impact a sequentially laminated build, certainly where different resin systems may be used for processing windows. Concerning the dark IG pads - check for skip plating as this is hallmark condition post thermal cycle. They will solder OK post cycle, but it is shelf life that is impacted, as well as potential adhesion issues depending on the copper pad condition under the IG.
Jeffrey Bush
Sr. Principle Product Assurance Engineer
Space Systems and Electronics - Performance Excellence
BAE SYSTEMS
P.O. Box 868, MER24-116A
Nashua, NH 03061-0868
Facility: 144 DW Highway
Merrimack, NH 03054
Office +1 603.885.8137
Mobile +1 603.318.8056
Fax +1 603.885.5258
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Monday, May 04, 2009 11:03 AM
To: [log in to unmask]
Subject: Re: [TN] PCB baking
Hi Rob,
No 'baking ' benefit is likely from baking above Tg; however, I am really concerned about solderability as well as damage to the PCB resin, sitting this long above Tg with its large CTE.
Werner
-----Original Message-----
From: Rob Strecker <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, 4 May 2009 10:54 am
Subject: Re: [TN] PCB baking
I have read the same thing. 105 - 125C around 4 hours. Our PCB supplier has had
issues with the pressing time in there process and we are seeing more
delamination on our boards again. They have recommended we bake our existing
stock, 5 boards stacked in the oven, at 180C for 2 hours (including ramp). My
main concern is the solderability of the ENIG finish after this baking profile.
They have shown me some pictures after bake and the gold is darkening. They are
asking us if this is acceptable because the boards passed a solder dip test. We
are going to bake some boards ourselves, paste and reflow to see the impact.
Any thoughts on the 180C bake temp? It seem as though they want the bake
temperature above the Tg temp (170) not sure why?
Rob Strecker
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Monday, May 04, 2009 7:57 AM
To: [log in to unmask]
Subject: Re: [TN] PCB baking
Hi Ioan,
No there is not, and there really cannot be.
The temperatures used are in the range of 105 to 125-I tend towards 10
5 C, but
the duration depends on a whole lot of factors. Among them: moisture content
[bake time ranging from 0 to 24 hours plus], construction [thickness, P/G layer
location, PCB resin, resin content, PTH/via pitch/diameter], reflow
process/temperature, etc.
My recommendation is to determine it yourself on some coupons supplied with the
PCBs.
Werner
-----Original Message-----
From: Ioan Tempea <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, 4 May 2009 9:25 am
Subject: [TN] PCB baking
Dear Technos,
I know this has been oftenly discussed here, but I would like to lively up the
traffic a little bit...
Is there any IPC standard reglementing the bake out time for PCBs, in terms of
temperature/dwell time?
Thanks,
Ioan Tempea, ing.
Ingénieur Principal Fabrication / Sr. Manufacturing Engineer
30 ans déjà! - Already 30 years!
950 rue Bergar, Laval, Québec, H7L 5A1
t : 450-967-7100 ext : 244
Mtl : 514-990-5762
f : 450-967-7444
[log in to unmask] <mailto:[log in to unmask]>
www.digico.cc <http://www.digico.cc/>
P N'imprimer que si nécessaire - Print only if you must
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