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July 1997

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From:
Vickie Chapman <[log in to unmask]>
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Date:
Wed, 2 Jul 1997 12:42:17 -0700
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Tom --

Thanks for your reply. 

We, too are trying to use the WSO for process control. We've had it for a year 
or so, but have only been using it on a 
regular production basis for the past couple of months, on just one machine 
where we have had some ongoing solder defect rate problems for several years.

We are currently gathering baseline data with the WSO, with the express purpose 
of putting control limits in place for statistical process control of topside 
preheat temperature, immersion depth, and parallelism. 

The Optimizer seems to point out some unacceptable problems with our equipment's 
ability to control wave height and preheat temperature, but, since I have no 
data from other machines and no historical data to compare our data to, I am not 
sure whether these really ARE problems, whether we need to buy a new machine, a 
different monitoring device, or what! My questions mainly relate to how much 
natural variation can be expected in the measurements taken by the Optimizer.

I would very much appreciate any more information you have on any of the 
following:

1. Preheat temperatures: We seem to have easily a 30 degree variation in topside 
preheat temperature from run to run, with measured temperatures anywhere from 
174F to 207F on our most commonly used recipe. How does the overall size of this 
range compare to what you're seeing?

2. Parallelism: The Optimizer manual says that we should be able to control 
parallelism within +/-0.2s of zero. Yet our measured values, even when centered 
 on zero, will range more like +/- 0.4s (that is, up to a 0.4s difference 
between left and right contact time, varying from run to run). How does this 
compare with what you're seeing?

3. Immersion depth: We regularly see measured immersion depths of ZERO, and 
variation from .012" to .084" from one run to the next is not uncommon. How does 
this compare with what you're seeing?

4. Are you using the Optimizer with a "rough" wave or a smooth wave only? I am 
concerned that trying to take immersion depth measurements with a rough wave may 
give inaccurate results.

Thanks again.

-- Vickie Chapman
--------------------------------------------------


On Wed, 2 Jul 1997 10:10:46 -0700 Lepsche, Thomas G (NM75) wrote:

> From: Lepsche, Thomas G (NM75) <[log in to unmask]>
> Date: Wed, 2 Jul 1997 10:10:46 -0700
> Subject: RE: ASSY: Wave Solder Optimizer
> To: 'IPC TechNet' <[log in to unmask]>,
>      "[log in to unmask]" <[log in to unmask]>
> 
> Vickie
> 	As far as "Trustworthy" data - we run some simple calibrations on the
> "Wave Solder Optimizer" (WSO) to maintain repeatability of the data
> during the runs by the WSO. Those calibrations provide us a high
> confidence in the data reported. Without verification of instrumentation
> any readings may prove to vary and become invalid. 
> 	We believe the value of the WSO to be in verification of the wave
> solder machine on a process control basis. We are therefore monitoring
> the WSO runs for shifts that would indicate the wave solder machine has
> changed and the parametric settings we have developed for specific PWA's
> may not produce the soldering quality results we have previously
> experienced. The frequency for running the WSO would  reflect your
> confidence in the stability of your machine factored with rework costs,
> inspection frequency, etc.
> 
> Semper Fi
> Tom   

------------------------------------
On 6-29, vikcha wrote:> 
> >
> >I am interested in hearing from anyone out there who is using a piece of 
> >equipment called the "Wave Solder Optimizer" to monitor and improve wave 
> >soldering quality in production.
> >
> >I would especially like to know how "trustworthy" you think the reported data
> >is, (temperatures, immersion depth, parallelism), and why.
> >
> >Thanks!
> >
> >
> >



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