Texas Instruments Cuts Costs and Improves Reliability for High-Performance Industrial Printer
The Problem
High program tooling and production costs for the keypad assembly on a line of heavy-duty industrial printers was causing difficulties for Texas Instruments (TI). Additionally, a larger number of components than desired was being used to meet design requirements, yet the overall assembly was still failing to achieve reliability standards in the printers’ demanding, high-dust environment.
The Challenge
Texas Instruments not only needed to reduce costs and improve the reliability of their Human-Machine Interface (HMI) assembly, they also needed to:
Create a universal circuit pattern for three separate applications
Reduce the number of components used to build the membrane switch
Incorporate an LCD display into the switch circuitry
Design a high-density keypad in a limited space
Explore alternatives for carrying the circuitry from the keypad to the PCB, which currently used a 20” cable
Develop a more compact shielding solution
Upon initial evaluation of the existing keypad circuitry, Reliatrace pin-pointed the main cause of the assembly’s reliability issues: a dual-circuit/multi-tail design. Built with single-sided construction, the membrane switch used cross-over connections – inherent points of weakness that commonly cause circuitry failure.
This design not only reduced reliability, it also required extraneous materials to accommodate the need for shielding from electrostatic discharge (ESD), including two full circuitry sheets stacked on top of another, each with a separate tail. When flexed, the stress between the tails and the switch body increased, causing the pressure sensitive adhesives (PSAs) to sheer and pull away over time.
Not ideal for TI’s high-use, high-dust environment, this membrane switch design was exposing circuitry to contaminants, significantly reducing the assembly’s durability and longevity. Additionally, it unnecessarily increased material, tooling and production expenses, presenting significant opportunity for improvement using Reliaswitch®.
The Solution
Employing our proprietary Double-Sided Polymer Circuitry (D/SPC®) technology, Reliatrace redesigned the membrane switch used in the keypad assembly, greatly reducing the risk of delamination, tail fractures and open traces. Reliatrace’s specialized screen printing process enabled the new Reliaswitch circuitry to be printed on both the top and bottom of the circuit substrate. Connecting traces with vias, Reliaswitch replaced the inherently weaker cross-over connections used in the previous single-sided design.
how does reliaswitch work?
For a detailed explanation of the Double-Sided Polymer Circuitry (D/SPC) technology used in Reliaswitch, please visit our Proprietary Technology page.
Not only did the Reliaswitch technology vastly improve the reliability of TI’s membrane switch, because it doubled the design space available on the circuit substrate, the number of components needed to meet requirements were greatly reduced. Using only one circuitry layer, Reliatrace was able to:
Accommodate the high-density keypad within the same circuitry footprint as the previous single-sided design
Provide a common circuit pattern for TI’s three separate industrial printing applications
Create a compact ESD shielding solution, eliminating the need for a second tail
Safely and efficiently route traces around the LCD display without the use of cross-over connections or a dual-circuit design
Consolidate components with one, unitary circuit for the LCD, keypad and circuit tail, replacing the 20” cable that was previously used to connect to the PCB
The Results
For over 27 years, this Reliaswitch application has performed with exceptional reliability, achieving circuitry defect rates close to zero in a high-volume printing environment. Twice honored with TI’s Supplier Excellence award, Reliatrace enabled TI – as well as the current commercial owner (Lake Erie Systems) – to significantly and sustainably reduce overall program, tooling and productions costs.
