Client Background

Our client is a leading security systems integrator and product manufacturer based in Southeast Asia, specializing in outdoor access control terminals, time attendance systems, and gate controllers. Their product line is deployed across commercial properties, gated communities, industrial facilities, and government buildings in tropical and coastal environments — regions characterized by high humidity, heavy rainfall, salt spray, and extreme temperature variations.

The existing keypad on their flagship outdoor access terminal was the #1 source of field failures. The membrane switch had an average lifespan of approximately 18 months before delamination or switch failure, resulting in expensive on-site replacement calls and dissatisfied property managers. The client needed a complete redesign that would deliver industrial-grade reliability in outdoor conditions.

The Challenge

Outdoor access control terminals face a unique combination of environmental and mechanical stressors:

• Water ingress: During monsoon rains, the terminal surface can be exposed to a continuous water film for hours. Any failure in sealing leads to corrosion of the switch contacts within weeks.
• Temperature extremes: Surface temperatures can reach 70°C in direct tropical sun and drop below freezing in winter months. The keypad must function reliably across the full range.
• Vandalism and mechanical abuse: Keypads are subject to aggressive pressing, impacts from objects, and attempted forced entry. The assembly must resist physical damage.
• Ultraviolet exposure: Constant tropical sunlight degrades standard graphic overlays and adhesives. Yellowing, embrittlement, and loss of adhesion are common failure modes.
• High cycle life: In busy commercial installations, individual keys (particularly "Enter" and "0–9" digits) can see 1,000+ actuations per day. The keypad must reliably exceed 5 million cycles per key position.

Our Solution

SanTeXing proposed replacing the client's existing membrane switch design with a stainless steel metal dome switch array mounted on a rigid PCB, encapsulated in an IP68-rated housing with a vandal-resistant stainless steel top plate:

1. Metal Dome Switch Array

We designed a 4 × 4 metal dome switch array using 8 mm diameter stainless steel snap domes (350 gf actuation force). Each dome is positioned over gold-plated concentric contacts on a rigid FR-4 PCB. The domes are held in place by a polyimide spacer layer with precisely punched pockets. The snap-action mechanism provides both tactile and audible feedback — the 350 gf force delivers a decisive click that users clearly feel even with wet or gloved fingers, while remaining comfortable for repeated daily use.

2. Secondary Contact Protection

To eliminate the corrosion risk that plagued the previous design, we applied a conformal coating (silicone-based) to the PCB assembly before dome placement, leaving only the gold-plated contact pads exposed. After dome placement, the entire assembly receives a second pass of conformal coating — a selective coating step that protects all solder joints and traces while leaving the dome-to-contact interface free. This dual-coating approach was verified by 1,000-hour salt spray testing (ASTM B117) with zero contact resistance degradation.

3. IP68 Enclosure Design

Rather than relying on adhesive bonding (which had failed in the previous design), we worked with the client's mechanical engineers to design a compression-sealed enclosure. The keypad assembly uses a silicone rubber gasket compressed between the stainless steel front plate and the enclosure base, providing a reliable IP68 seal without adhesives. The tail exit uses an overmolded strain relief boot rated to IP68.

4. Vandal-Resistant Construction

The top surface is a 1.5 mm 304 stainless steel plate with laser-etched key position markings. The plate is secured to the enclosure with tamper-resistant Torx screws. The steel construction withstands impacts of up to 5 J (equivalent to a heavy key strike or a thrown rock) without deforming enough to cause false actuation.

5. UV and Weather Resistance

The laser-etched markings on the stainless steel surface require no ink, adhesive, or overlay — eliminating the UV degradation failure mode entirely. The enclosure body is molded from UV-stabilized polycarbonate/ABS blend, tested to 2,000 hours of accelerated UV exposure (ISO 4892-2) with no significant color shift or embrittlement.

Results

The redesigned access control terminal was launched in Q1 2026. Results after 6 months of field deployment:

• Zero field failures reported across 8,200 units deployed in Singapore, Malaysia, Indonesia, and the Philippines — covering tropical rain, coastal salt spray, and high-heat urban environments.
• IP68 verification: Third-party tested to 72 hours continuous submersion at 1.5 meters with zero water ingress.
• Mechanical endurance testing: 5 million cycles per key position at 60 actuations per minute — contact resistance remained below 200 mΩ throughout (limit was 500 mΩ).
• User feedback: The tactile click was rated 4.5/5 in user surveys; property managers reported a noticeable reduction in maintenance calls.
• The client has adopted the SanTeXing metal dome array as the standard keypad platform across their entire product line, including indoor models (where IP68 is reduced to IP65 for cost optimization).

Related Products

This project demonstrates SanTeXing's custom metal dome switch manufacturing capabilities. Explore our membrane switch solutions for indoor access applications and FPC designs for compact control interfaces.