When a product team specs a silicone keypad for a remote control, a medical device, or an industrial handheld, the drawing usually lists color, logo, and key layout - but almost never the three numbers that decide whether the keypad feels cheap, mushy, or right. Those numbers are Shore A hardness, key travel, and conductive pill material. This guide walks through each one the way an experienced product engineer would spec it, and points out where cheap silicone keypads usually cut corners.
1. Shore A hardness: the single most-felt number
Shore A is the durometer scale for soft rubber. A typical consumer remote control key is Shore A 40–50. A medical infusion pump key is Shore A 50–60, because it must resist accidental presses. A heavy-industry keypad exposed to gloves can run Shore A 65–70. Anything below Shore A 30 feels like jelly; anything above 75 feels like hard plastic and loses the soft-touch feel buyers expect from silicone.
The mistake buyers make: they ask for "soft" without a number. A supplier's idea of soft is Shore A 40; yours may be Shore A 30. Spec the Shore A on the drawing, with a ±5 tolerance. Our medical silicone key line is molded at Shore A 55 ±5 for exactly this reason.
2. Key travel and snap ratio: how deep the button goes
Travel is the distance the key moves from rest to bottom-out. A well-designed remote control silicone key has 1.0–1.5mm of travel. Below 0.8mm, the key feels numb; above 2.0mm, it looks cheap and slow. The "click" feel comes from either a four-leg metal dome inserted under the key, or a conductive carbon pill with a molded snap profile.
For high-volume consumer products, the carbon-pill route is cheaper. For medical and industrial applications where reliability matters more than 0.02 USD per key, we recommend embedding a real stainless steel snap dome inside the silicone key. The dome gives a consistent F1 across millions of actuations; the carbon pill degrades slowly and its actuation force drifts.
3. Conductive pill: carbon vs gold vs nickel
The conductive pill is the bottom of the key that touches the PCB pad. It must be soft enough to spread over the pad, conductive enough to carry the signal, and wear-resistant enough to last the rated life. Three options dominate:
- Carbon pills (black, 50–100Ω): cheapest, fine for consumer remotes. The contact resistance drifts upward over time.
- Gold-plated pills (gold-colored, <30Ω): stable contact, used for automotive and medical. Adds roughly 0.05–0.10 USD per key.
- Nickel-graphite pills: mid-tier, used for home appliance keypads where a little drift is acceptable.
If your PCB uses gold-plated pads, match the pill plating to avoid galvanic corrosion. Carbon-on-gold is fine; carbon-on-tin is not.
4. Surface finish: laser-etched vs pad-printed vs domed
Legends on silicone keys wear off - that is the #1 reason customers complain. Pad printing (ink on top) looks cheap after a year. Laser etching (the surface is charred to a darker shade) lasts the life of the part but only works on dark silicone. Doming (a clear epoxy coat over the legend) is the premium option: it survives 10,000+ alcohol wipes, which matters for medical devices that get disinfected between patients.
For a medical keypad, spec doming. For a TV remote, laser etch or pad print. For an industrial keypad used with gloves, laser etch on a high-contrast two-shot key.
5. The integration question: silicone key alone vs dome sheet array vs membrane switch
Buyers often compare three parts as if they were alternatives. They are not:
- Silicone key alone (the molded rubber part): you supply the PCB and the contact. Cheapest per part, but you do the assembly.
- Silicone key + PET dome sheet array: we laminate the dome sheet to the back of the key, you just solder it to your PCB. One extra part, much cleaner feel.
- Finished membrane switch: we build the whole assembly including the overlay, the dome layer, the spacer, and the tail. Highest price, lowest integration risk.
For a new product with a tight schedule, the membrane switch route is usually the right call. For a cost-down on an existing product, the silicone-key-plus-dome-sheet route saves the most.
6. Tolerances buyers forget to spec
Three small tolerances cause most field complaints:
- Key height tolerance ±0.15mm. A 0.2mm variation across a 12-key array looks visibly uneven in the mold.
- Color tolerance ΔE < 1.5. Silicone yellows over time; if you match the color at day 0 with ΔE = 2, it will look mismatched at month 6.
- Flashing < 0.05mm. Excess flashing around the key edge feels sharp under a fingernail and is the #1 reason keypads get returned at incoming inspection.
SUNAURA Machinery molds silicone keypads, embeds metal domes, and laminates dome sheet arrays in the same Qingdao plant - which means the tolerances above are controlled in one factory, not negotiated across three. If you are designing a new remote, medical handpiece, or industrial control panel and want a second opinion on your key spec, send us the drawing. We will mark up the drawing with the three numbers we would change, before you commit to tooling.
