Start by fixing the assembly reference, actuator and test conditions. Then record electrical actuation on the press stroke, electrical opening on release, and the key's final returned position separately. Force, displacement and electrical state need to refer to the same operation. A curve from a loose metal dome, or return felt by a finger, cannot replace verification of the complete panel.
This article discusses normally open keys: pressing closes the circuit and releasing opens it. Other circuit arrangements need their own defined initial and released states.
Record travel, actuation force and return separately
“Moves when pressed,” “feels crisp” and “has made electrical contact” describe different observations. A drawing with only one travel value still leaves the measurement's start and end positions unspecified, along with whether electrical actuation has occurred at that point.
Panasonic's explanation of tactile-switch travel describes travel as the distance pressed. Its travel selection guide discusses different operating needs associated with press depth. These references concern tactile switches. They can help define measurement positions, but do not prescribe a universal value for custom membrane switches.
Omron's basic-switch terminology defines operating and releasing positions separately. Use that distinction when recording the operation: mark where electrical switching occurs on pressing and where it returns on release. The basic-switch parameters and test conditions should not be applied directly to this membrane-switch project.
| Stage observed | What to record on the sample | Question the record answers |
|---|---|---|
| Pressing from the initial state | Reference plane, actuator contact point, actuation position and force at that point | Where and at what force does electrical actuation occur? |
| Continuing after actuation | Project-permitted end position, structural stop and changes in the curve | Are the actuation point and permitted further travel distinguished? |
| Releasing from the pressed state | Position or time of electrical opening, with corresponding force and displacement | When is the input released during the return stroke? |
| After full release | Final key position, any sticking, and electrical state | Do mechanical return and electrical release both meet the agreed requirements? |
| Scope and sources of this table | Suggested project records for normally open keys; use Panasonic's tactile-switch travel explanation and Omron's basic-switch terminology to distinguish measurement positions | Not universal membrane-switch parameters or a test standard. Do not directly transfer tactile/basic-switch values or conditions; agree methods and criteria for the project |
The records need to describe the same operation. A force–displacement curve without continuity markers does not directly identify the electrical actuation point. Continuity records alone do not show the key's final returned position. Put these observations into the project verification plan. Agree measurement methods, target ranges and sample quantities against the drawing and operating method. If return speed is required, define the timing start, end and measurement method separately. “Looks fast” in a video is not a universal criterion.
Confirm the assembly before comparing curves
Use consistent actuator dimensions and location, press direction, speed, support and instrumentation when comparing samples. Record the sample configuration again after changing a housing step, overlay or adhesive. Two curves from the same dome type can still represent different complete assemblies.
For metal-dome constructions, Snaptron's actuator discussion addresses actuator geometry and centering in relation to operating feedback. The guidance applies to the dome assemblies it discusses. Select the actuator for the actual dome and complete membrane-switch stack; do not copy a catalog proportion without checking applicability.
Retain separate data for loose parts, panel samples with their overlay and adhesive fitted, and prototypes assembled in the housing. Do not combine them into one average. If off-center pressing or repeated operation needs checking, specify positions and operating conditions on the drawing first. Without agreed conditions, “works the same at the edge” or “repeated pressing is fine” is not a reproducible acceptance record.
Turn an assisted-return design into sample-check questions
The published utility-model document “一种薄膜开关及薄膜开关按键” (CN222300514U), naming Shenzhen Baoshengda Technology Co., Ltd. as patent holder, has a publication date of January 3, 2025. Its published PDF describes a combined structure with mechanical supports. The base carries a conductive switching part. Top and side membranes form the key section, and a linkage at the center of the top membrane faces the conductive part. Spring supports at the four corners support the membrane, with spring posts beneath. The document describes the linkage moving into contact when pressed, with the supports and spring posts assisting return on release.
If a project uses this type of structure, check the sample: are the pressing part, linkage and conductive part aligned? Do the supports and housing leave the agreed movement space? Can the returned key position and electrical opening be recorded separately? This design is not representative of every conventional printed membrane switch. It does not establish the return speed, actuation force, travel or operating life of products currently supplied. The publication describes a technical design; current legal status, supplied construction and sample results need separate checks.
Make the acceptance record usable by the next colleague
Keep the sample identity, measurement conditions and criteria together so another person can repeat the checks:
- Sample ID, drawing and stack revision, and whether the housing, adhesive and actual supports are included.
- Reference plane, key center, actuator contact position, press direction and test speed.
- Instrumentation and measurement circuit, closure and opening criteria, and original curve or data file.
- Press-actuation, release-opening and final-return records, including the exact location and conditions of abnormalities.
- Project criteria, measured results and items needing further checks, rather than only “key feel passed.”
If electrical contact occurs without clear tactile feedback, record the electrical result and tactile behavior separately. If the key feels normal but intermittently fails to close, keep the data for the abnormal operation before examining contacts, the dome or spacer, and supporting assembly. A symptom alone is not enough to name one component as the cause.
Baoshengda's custom membrane switch page provides the scope for discussing construction, interfaces, samples and acceptance inputs. The instrumentation application page addresses key location and accumulated tolerances in relation to assembly drawings. For silicone, mechanical support and membrane-circuit combinations, also see combined keypads and key assemblies.
When selecting a construction, see metal-dome versus non-tactile membrane switches (Chinese). For electrical criteria, see the membrane circuit acceptance checklist (Chinese). Prepare the housing drawing, key positions, intended operation and existing sample records, then use the contact page to discuss the project. Confirm acceptance conditions in the project documents.