Paul, the offset should result in a statistically difference in the
height (and hence volume) of the deposit and should show up in the final
results. The SPI should also be able to identify when the print is
offset from the center. Most of our stencils have a two mil aperture
reduction, so depending upon the offset, the deposit may not go off pad
at all.
Regards,
Amol Kane
Process Engineer
AsteelFlash US East Corp
Tel: (607) 687.7669 x349 (O)
www.asteelflash.com
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From: Paul Edwards [mailto:[log in to unmask]]
Sent: Wednesday, March 21, 2012 10:48 AM
To: TechNet E-Mail Forum; Amol Kane (Asteelflash,US)
Subject: Re: [TN] Evaluating solderpaste inspection machines
Amol,
If you print off the pads how are you going to compensate for the height
difference of the underlying substrate wheither you have soldermask or
base PCB dielectric next to the pad...
Paul
Paul Edwards
[log in to unmask]
Surface Art Engineering
"Amol Kane (Asteelflash,US)" wrote:
Thank you for your responses so far....I will be using actual product
assemblies without introducing deliberate defects. I have been told that
the SPI programming would be from the stencil aperture area (and not the
assembly pad area). If that's the case, then it will truly reflect the
paste volume that should be deposited on the pad, with gasketting not
affecting the release to a large extent (there may be some release
issues if the positioning is grossly off), which gives me another idea.
All of my tests focus on volume measurements so far. What I CAN do is
introduce a deliberate offset in the printer and see if that number is
reproduced in the SPI machine to determine its ability to detect shift.
For simplicity, I will assume that the printer prints "dead on pads"
with zero offset and that board stretch is consistent across the date
code (I don't have the resources to incorporate blocking in my DOE to
account for noise factors)
Regards,
Amol Kane
Process Engineer
AsteelFlash US East Corp
Tel: (607) 687.7669 x349 (O)
www.asteelflash.com
This e-mail and any attachments are confidential. It is intended for the
recipient only. If you have received this e-mail in error, please
immediately notify the sender by replying to this e-mail and delete the
e-mail and all copies from your computer. Although the sender and
AsteelFlash have taken every reasonable precaution, the e-mail and
attachments may have some errors or omissions and may contain viruses.
We cannot accept liability for any damage that you sustain as a result
of that.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl Ray
Sent: Wednesday, March 21, 2012 8:32 AM
To: [log in to unmask]
Subject: Re: [TN] Evaluating solderpaste inspection machines
Amol,
One of the biggest issues we encountered over the years doing SPI
Evaluations is the positioning accuracy of the printer up line. Not sure
which equipment you are evaluating but with the equipment we have the
measurements were referenced off the surface area of the PWB. When we
ran the tests we seen significant impact of the repeatability of the
printer which affected the gasketing on the test vehicle which affected
our volume and area measurements. So you might want to take this into
count when you chose your test vehicle. If your using a stencil that is
cut one to one and the printer exhibits drift then your gasketing will
be affected causing variation in your readings of area and volume. This
would reflect more on the printer than the SPI but a good SPI you will
see this and make conclusions as to the effect on your process.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Wednesday, March 21, 2012 8:13 AM
To: [log in to unmask]
Subject: Re: [TN] Evaluating solderpaste inspection machines
Amol,
One possible small paste target deposit is the small round solder
deposits used to define "Solder Bump" test point. I think they were 10
mil rounds.
Not sure.
Just an idea.
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Amol Kane
(Asteelflash,US)
Sent: Wednesday, March 21, 2012 8:08 AM
To: [log in to unmask]
Subject: [TN] Evaluating solderpaste inspection machines
Dear All,
I am in the process of coming up with a testing plan for evaluating
solderpaste inspection (SPI) equipment and have some questions. One of
the first things I want to perform is a GR&R study on a NIST certified
target of the smallest possible size. I can understand the repeatability
part, but is reproducibility a valid measurement criterion as the only
operator involvement in this case will be assembly loading/unloading and
all other external conditions will remain the same?
I also plan to evaluate the effect of board rotation (0 vs 90 degrees)
on volume measurements by a simple DOE using ANOVA, investigate process
control using control charts and calculate Cpk for the calibration
target and actual volume measurements on the most technologically
complex assembly we build (0201s, QFNs, fine pitch BGAs etc.,). Don't
have anything with a 01005 as of yet. Is there anything else that I
have not included (but is a critical data driven factor for evaluation)?
Also, If anybody else has performed SPI evaluation in the past and is
willing to share their evaluation plan, I can combine it what I have and
publish it on technet for future use with due credits.
Thanks,
Amol
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