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<http://www.asteelflash.com>
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-----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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