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MANUFACTURING
The Business Problem
A leading
bare board (PCBs) manufacturer enjoys around 70% of the bare
board market. During the past few months they have been receiving
complaints from their customers about defective Printed Circuit
Boards and also threatening to move the business to their competitors.
The VP Operations looks towards Six Sigma to solve this problem
which may lead to huge revenue and image loss.
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Benefit Analysis
A Six Sigma Black Belt assigned to
this problem first tries to understand the full impact of
this problem. The Black Belt realizes that this problem is
costing approximately $400,000 per month because of replacements,
$75,000 because of rework and scrap and an opportunity cost
of $1,000,000 because of lost sales. The manufacturing yield
was down to 95%. Attaching actual cost to the problem brings
out the gravity of the problem. Looking at the figures, the
VP Operations assigns another Black Belt to the bare board
problem.
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Problem Identification
The
two Blackbelts get to work to understand the cause of the problem.
Upon analysis, the blackbelts realized that the majority of
the defects were due to the tracks getting cut during the etching
process. The required track length was 20±0.1 microns.
Upon examining they realized that the mean of the track length
of the boards manufactured was around 19.95 microns. However,
the standard deviation was 4.2 microns. Therefore, the problem
lay in the consistency of the etching process.
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Root Cause Analysis
The Blackbelts collected data and analyzed
to find that the etch bath temperature, time and solution
strength were the three critical factors towards track width.
Solution
To find the optimal values for
the above parameters to reach a target track width they proceeded
to do a Design Of Experiments (DOE). Once these solutions
were implemented, the track width mean became 20.02 microns
with a standard deviation of 0.1 micron.
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Result
The Bareboard manufacturer's
Cost Of Quality reduced and the yield went to 99.99%. This solution
was immediately noticed by the customers as their defect rate
reduced. |
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