BACKGROUND

This study addresses the improvement of an encapsulation process used in electro-optical image intensifiers to isolate the electrically active surfaces from ambient influences. The need for improvement came from customer-imposed environmental test requirements which were not being consistently met in the production environment, resulting in customer dissatisfaction and increased costs due to rework and scrap.

The customer-imposed environmental testing simulated the system's end user's conditions. The system consists of this electro-optical image intensifier, housing and associated power supply subsystems.

PROCESS

The approach selected for this improvement effort was product and process parameter design optimization using Dr. Taguchi's methods. The figure of merit used to select the optimum parameter set was a double-signal dynamic signal-to-noise ratio. This engineering metric replaced the customer's quality level metric called "luminance gain" typically measured using the image intensifier module. At the customer's quality level, constant "luminance gain" was ideal, but this characteristic was impacted by many other parameters at the product level, so it was necessary to isolate the electrical encapsulation process and measure "coupons" designed to simulate the function of the encapsulant, electrical insulation.

An orthogonal array was used to efficiently study eight process and product control parameters against two noise parameters, one environmental and the other a manufacturing condition. The orthogonal array allowed evaluation of 4,374 possible control parameter combinations using only 18.

BENEFITS

As a result of the improvement effort, the following benefits were realized:

• Scrap and rework were...