Analysis of Key Burnout Failure in BSD-5010-R3-2670 Membrane Switches

        Regarding the quality of the membrane switches (Model: BSD-5010-R3-2670, 4P interface, 280gf force, with adhesive backing, FPC connection), we would like to know whether this batch underwent full testing and what the specific testing procedures were. Our production line recently reported cases of key malfunction: one unit was found to have blackened and burnt internal circuits upon disassembly, while another showed no visible defects but failed to function. We request your assistance in identifying the root cause and providing a solution.

Analysis and Handling Report on Key Function Failures in Some BSD-5010-R3-2670 Membrane Switches

Recently, we received feedback from a customer that among 32 units of BSD-5010-R3-2670 membrane switches (4P interface, 280gf force, adhesive backing, FPC connection) in use, two units experienced key burnout resulting in functional failure. Verification confirmed that there are currently no production orders for this model. We immediately advised the customer to suspend usage and return all products for a comprehensive inspection.

I. Inspection Findings

The factory performed a full inspection of returned products under magnification and confirmed that both defective units had non-functional "ESC" keys. An additional inspection of six units from the same batch in stock revealed no similar defects.

II. Failure Analysis

Circuit testing with a multimeter confirmed an open circuit in the "ESC" key line. Initial assessment indicates that the silver paste line connected to the key was printed too thinly, causing it to burn out during the customer’s power-on test due to insufficient current-carrying capacity.

Physical inspection of the circuit layer revealed slight discoloration at the failure point. The measured width of the silver paste line was only 0.32mm, below the specified design width of 0.5mm.

Tracing back to the printing process, it was found that the screen used for silver paste printing had a 16-up layout. One of the patterns had clogged meshes, resulting in abnormally thin printed lines. This was caused by residual silver paste that remained after inadequate cleaning of the screen.

During production, inspectors failed to perform actual measurement and comparison of the line width on silver paste printed sheets, and finished product testing also did not identify the defect, allowing non-conforming products to be shipped.

III. Root Cause

The primary cause of this quality issue is inadequate cleaning of the silver paste printing screen, leading to partial mesh clogging and resulting in printed line width below specification. Furthermore, the absence of quantitative line width inspection and first-article confirmation during the process allowed the defect to go undetected.

IV. Corrective and Preventive Measures

Request the customer return all remaining products. We will conduct 100% inspection under magnification and reprocess or replace all identified non-conforming products.

Immediately scrap the current screen and produce a new one. Implement strict validation of silver paste line width against standards for all new screens.

Enhance silver paste printing inspection standards. Designate line width as a key inspection characteristic and mandate actual measurement confirmation during first-article validation.

Enforce strict screen cleaning procedures. After each use, screens must be thoroughly cleaned and inspected under a light table to ensure no mesh clogging or residue before storage.