The audit auditor from TUV Rheinland showed up at our Qingdao factory at 8:30 AM on a Tuesday last month. He walked straight to the incoming material inspection room, opened a box of SUS301 stainless steel coil, and asked to see the material certification. We handed him the mill certificate, the incoming inspection record, and the SPC chart for the coil hardness. He flipped through the documents for two minutes, then said, "Show me what happens when a coil fails incoming inspection."
This is the part of ISO 13485 audits that catches manufacturers off guard. It is not enough to have documents that say you inspect incoming materials. You have to show a record of an actual failure, what you did with it, and how you prevented it from reaching production. We pulled the record from March, when a coil of SUS301 came in with a hardness reading of Hv 420 instead of the specified Hv 380-400. We quarantined the coil, notified the supplier, and re-sourced from a different mill. The auditor nodded and moved on to the production floor.
We passed the surveillance audit with zero major non-conformances. This means our metal domes, dome sheet arrays, and silicone button assemblies are qualified for medical device customers who need ISO 13485-certified components.
Medical device control panel built with our ISO 13485-qualified dome sheet assembly.
What ISO 13485 actually requires for dome manufacturers
Most component manufacturers think ISO 13485 is just a paperwork exercise. It is not. The standard is built around risk management and traceability, and for a metal dome supplier, that means four specific things.
First, traceability of raw material. Every coil of SUS301 stainless steel we use has a mill certificate tied to a lot number. That lot number is linked to every die press run, every AOI inspection result, and every shipment. If a medical device customer finds a force drift in the field, we can trace the dome back to the exact coil, the exact die, and the exact shift that produced it.
Second, controlled production. Our die press parameters are locked: stroke speed, press force, die temperature, and feed length. The operator cannot change these settings without a supervisor password. Every shift, the first 100 domes are measured for actuation force and conductivity. If the force drifts more than ±10g from the nominal, the press is stopped and the die is inspected.
Third, change control. If we want to change the stainless steel supplier, the die design, or the PSA adhesive, we have to run a validation protocol first. We produce three batches under the new condition, test them against the old condition, and get the results approved by our quality manager. We cannot just switch suppliers because one is cheaper.
Fourth, complaint handling. Every customer complaint goes into a CAPA (Corrective and Preventive Action) system. We investigate the root cause, implement a fix, and verify that the fix worked. The auditor spent an hour going through our last five CAPA records, checking that each one had a root cause analysis, a corrective action, and a verification result.
What changed in our facility
We built a dedicated medical-grade production area last year, separate from our consumer electronics line. The room is a Class 100,000 cleanroom with controlled temperature (23C ±2C) and humidity (45% ±10%). Operators wear smocks, gloves, and hairnets. The die presses in this room run only medical-grade orders, so there is no cross-contamination from automotive or industrial production.
Four-legged stainless steel domes produced in our medical-grade cleanroom.
We also installed a dedicated ESD-protected assembly line for membrane switch panels and FPC button assemblies that go into medical devices. Every workbench has an ESD mat and a wrist strap. We measure contact resistance on every 50th panel, and we keep the test data for 15 years, as required by the medical device quality system.
What this means for our customers
If you are a medical device OEM looking for a qualified metal dome supplier, you need a partner that understands ISO 13485, not just a supplier that stamps parts. We can provide the validation documentation, the traceability records, and the change control process that your regulatory team needs.
We also support your design transfer process. When you move a product from prototype to production, we provide the design history file (DHF) summary, the process validation protocol, and the initial qualification data. We have done this for infusion pump keypad, patient monitor buttons, and diagnostic equipment panels.
The surveillance audit was the second one since our initial certification in 2023. The next recertification audit is in 2028. We are also working on adding IATF 16949 for automotive customers, which should be complete by Q2 2027.
- John Smith, Senior Application Engineer, Shanyo
