Sam,

We basically have improved our process control by a combination of improved instruction and physical testing. In this day in age, we feel that accurate information being readily available to the operators is everything! In drilling we are primarily concerned with hole quality and hole placement accuracy. 

First off, we have initiated a drill card that is pulled for every traveler. This card contains instructions and information regarding the established feeds/speeds, and number high for that particular part. It may also list information on any issues with the part that was obtained during previous runs.  Our process engineering establishes the initial card information then it is or can be modified as more information about the part quality is obtained. We have conclude that some designs occasionally need a little "tweak" from the industry established norm to yield a better or more consistent part. 

Accuracy of the machines are maintained by drilling a standard test pattern and having the location variation from program nominal measured and plotted. This is done quarterly and is relatively inexpensive. We review the data and react accordingly. We have learned that despite our annual calibration, some of our machine are more accurate and better suited for smaller holes sizes that others. 

Drill bit quality is of most importance. We have provided formal training to all operators regarding proper drill bit evaluation. Each station has been provided with a drill bit inspection scope and our procedures require each drill to be inspected and measured before it is placed in a pod. I feel you will be surprised by your finding one you institute a 100% drill bit evaluation. We have place this responsibility on our operators since this can be done while loads are running. Basically the drill operators have time. 

Another factor with plays a major role in hole quality is the laminate cure. Especially in multilayers. Although this really isn't a drill process control, I feel it important to note since it has such an impact. Make sure you laminate is properly cured. 

These are some of the major things we have to improve process control in our drill areas. I sure there are many other opportunities for improvements. Good luck in your endeavor. I hope this information is helpful to you.

Ed Cosper
Director Quality Assurance and Engineering

----------
From:  sam mccorkel[SMTP:[log in to unmask]]
Sent:  Friday, February 06, 1998 8:47 AM
To:  [log in to unmask]
Subject:  [TN] FAB: Process controls for drilling

We want to improve the process controls that we have in our drilling
department and I'd like to see what other board manufacturer's are doing.

We're drilling FR-4 materials anywhere from 2 - 10 layers.

I'd appreciate your input!

Sam McCorkel

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