Terry,

Here's something you might try. We developed at test pattern with 4 sections of line widths and spacing. Starting with .003/.003 and ending with .006/.006. We fanned out the last part of each group so that each line would terminate into a pad spaced on a .100 mil grid. We then generated a test fixture to perform a final test. We process groups of 25 18x24 panels with these patterns. The panels are processed without any inspection or special handling until after etch. We then AOI the etched panels and document the number of defects (nicks, pin holes, shorts and opens) detected in each group. Although I don't employ one, a C chart can be used to monitor the number of defects per unit at this point ( a unit being one test pattern of a certain line width). We correlate data by circuits defected vs circuits produced which each individual circuit being its own entity. The defects are categorized separately on a Parato chart by type and grouping (grouping being the line width). The panels are then processed thru the shop and tested at final. Final yields are accumulated and charted on a P-Chart. 

We process 2 sets of test panels, one as a print and etch to define inner layer capabilities and one as a pattern plate to define outer layer capabilities. 

Basically, after several processed groups,  we have a fairly good picture of our process capability with regard to expected defects by type and anticipated end yields by type and density. Using data from a c chart or P chart, you could express the capability as either a Cp or Cpk .Copper thickness can be varied to provide even more data if that is a variable of concern. Our tests have only been done on 1 oz inner layers and 1/2 oz outer layers. 

Hope this helps...

Ed Cosper
Graphic Electronics Inc.
Tulsa, OK 


----------
From:  Terry Zhu[SMTP:[log in to unmask]]
Sent:  Tuesday, October 28, 1997 12:19 AM
To:  [log in to unmask]
Subject:  [TN] SPC for primary image process

Hello the world:

I am looking for help from some of you who have experience of implementing SPC
over the primary image process for fine line production (3mil/3mil). Could you
share information about data you collect and the anlysis conducted for
determining the process capability ? How many of you actually achieve reasonable
yield without using liquid ink and collimated or point light source.

Imput is really appreciated !

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