Improved Reliability for Failing GPS Application
The Problem
The maker of GPS devices for use with heavy machinery was receiving a concerning number of user complaints related to the reliability of the keypad on one of their products. Customers were experiencing keyboard instability, inconsistent key response during activation and, at times, complete device failure.
The Challenge
The GPS manufacturer needed an experienced printed electronics supplier able to expertly diagnosis the root cause of the keypad assembly issues and swiftly resolve the field failures customers were experiencing.
Upon initial evaluation by Reliatrace® engineers, three major causes of the assembly inconsistencies were identified:
The platform supporting the assembly showed signs of warping, causing the keypad to shift out of the correct pin-out position during use
The elastomeric (i.e., silicone rubber) keypad had a poor fit with the membrane switch circuit it covered, causing the inconsistent tactile feel reported by users
The membrane switch used single-sided construction, which contained cross-over connections –inherent points of weakness – as well as a suboptimal tail exit where traces were in expansion instead of compression, leading to terminal fractures
Single-sided membrane switches have significant reliability issues, as they require a dielectric layer to separate the printed silver circuit traces that are printed over one another in this type of construction. More susceptible to silver migration, the dielectric layer has micro-pores that can allow the top silver trace to leach through and contact the bottom silver trace. These designs often pass initial electrical testing, but can fail over time.
The low-reliability design, quality issues and lack of reliable circuitry presented 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 GPS, employing a specialized screen printing process that enables 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.
Additionally, Reliatrace made the following improvements to increase the reliability of the keypad assembly:
Printed tail traces on the bottom of the circuitry substrate, placing them in compression, NOT expansion, thereby reducing the risk of terminal trace fractures
Worked with the client’s engineering team to implement spec changes for the platform, eliminating the warping and keyboard stability issues
Redesigned the molded elastomeric keypad to for optimal conformation to the electronic circuitry, preventing keypad shifting and increased tactile response
Added a carbon ink overcoat to further thwart silver migration and protect the circuitry from the harsh outdoor environment
The Results
For over 18 years, this Reliaswitch application has performed with exceptional reliability, achieving circuitry defect rates close to zero while operating in rugged outdoor environments. Reliatrace enabled the GPS device manufacturer to reduce the costs of the previous field failures, significantly cutting losses due to repairs and returns.
