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Case Studies

Pressure Sensor for Medical Application

A global medical instrumentation manufacturer had an application for a membrane switch to serve as a sensor.  The membrane switch approach was desired to reduce the weight and space required to perform the task in an ambulatory infusion pump.  Superior accuracy was required to ensure the appropriate administration of fluids.

GDSI was invited to address the following problems:

1) The actuation force of the sensor exhibited unacceptable variability. 

GDSI’s response was routine.  By using its standard screen printing process utilizing optics to establish image to image registration, superior screen printing control for the position of the sensor circuit in relation to the cut edge of the circuit substrate reduced the variability of actuation force to well within acceptable performance levels.

Additional precision with pressure sensitive adhesive layers for the remainder of the sensor construction was also enhanced by optical indexing for die cut layers, and a close tolerance steel rule die.

As a test of compliance and assurance, GDSI performed a full performance parameter functional test on each sensor before shipping to the customer.  The customer accepted the test procedure as qualification for ‘dock to stock’ receipts, reducing the cost of their incoming inspection.
2) Silver migration was commonly evident in field failures

GDSI provided its standard response to silver migration – printing carbon over silver with tight tolerance print images made possible by optical imaging.

3) Millimeter spacing on circuit tail was needed to match a ZIF connector

Again, the optical indexing of GDSI screen printing allowed the tight tolerances on the circuit tail to meet the demanding specification of the tight tolerance ZIF connector required by the weight and space limitations of the project.

The result of GDSI’s involvement reduced the cost of production, increased the yield of acceptable product, and helped the customer provide a more reliable instrument for the medical market.

Heavy Duty Industrial Printer

GDSI design expertise was enlisted to create a membrane for a heavy duty industrial printer.  The environmental requirements included resistance to a high dust environment, heavy keypad use, and performance reliability and longevity.  Additional requirements included a consolidation of parts, a cable to connect to the CPU/PCB, and a turn key product for the customer’s printer assembly.

There was also a significant demand for extreme density of keypads due to the limited space available for a 4 x 5 matrix of switches, and the ability to carry the switch circuitry to a cable traveling 20” from the keypad to the PCB.  A compact shielding solution was the final requirement.

GDSI responded with a design which utilized Double Sided Polymer Circuitry® to achieve the following:

1) incorporated an LCD display into the circuitry of the switch

2) provided one unitary circuit for the LCD, keypad and circuit tail traces to cover the 20” length terminating in an AMP connector

3) stayed within the space limitations to provide a 4 x 5 switch matrix on a single layer of circuitry

4) designed a shield which eliminated the need for a second circuit tail

5) provided a common circuit pattern for 3 separate applications, reducing overall program tooling and production cost

6) reduced the number of components required to build the switch

7) improved reliability and performance

8) met the customer’s requirements for a turnkey product

This product has a fifteen year performance history and is still being used in commercial applications.  The printer is a known leader in the industry for reliability and high volume forms printing.

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