Hengchuanki: What is an EMI-Shielded Metal Dome and Its Manufacturing Process?

 What is an EMI-Shielded Metal Dome? 

An EMI-shielded metal dome is a metal spring integrating electromagnetic shielding functionality. Based on traditional metal domes (which enable circuit conduction and tactile feedback), it adds a shield structure to simultaneously meet the needs of key actuation and electromagnetic interference (EMI) protection. 

 Core Feature: "Dual Function in One Component" 

- **Retains basic dome functions**: Conducts circuits upon pressing and provides mechanical feedback. 

- **Adds shielding capability**: The metal shield isolates the key area from surrounding circuits, blocking external electromagnetic interference (e.g., radio frequency signals, high-frequency noise) and preventing internal circuit electromagnetic radiation leakage, ensuring signal stability of electronic devices—especially suitable for EMI-sensitive scenarios such as communication equipment and precision instruments. 

 Manufacturing Process of EMI-Shielded Metal Domes 

The process builds on traditional dome manufacturing, adding shield forming and integration steps as follows: 

 Shield Production 

**Material Selection** 

The main material is typically high-elasticity stainless steel (e.g., 301, 304) or beryllium copper (to ensure spring elasticity). High-conductivity materials (e.g., brass) are used in some shield areas to enhance shielding performance. Material thickness balances elasticity (dome: 0.1-0.3mm) and shielding strength (shield: 0.2-0.5mm). 

**Composite Structure Design & Mold Development** 

Design an integrated structure of the dome (arc凸起) and shield (enclosed/semi-enclosed structures like sidewalls or top covers) to ensure the shield fully wraps the key area without affecting dome actuation. Develop dedicated multi-station progressive dies to simultaneously form the dome’s arc and the shield’s complex structures (bending, sidewall forming, etc.). 

**Precision Stamping (Core Step)** 

1. First, form the dome’s arc structure via stamping (similar to traditional dome processes) to define actuation force and rebound performance. 

2. Synchronously stamp the shield structure, forming "shield walls" or "top covers" around the dome via bending and stretching, ensuring seamless connection between the shield and dome to create an enclosed electromagnetic shielding space. 

Key requirements: No gaps at the connection to avoid electromagnetic leakage; dome arc must remain unaffected (to prevent abnormal key feel). 

**Surface Treatment** 

- Dome area: Electroplated with nickel or gold (to enhance conductivity and wear resistance). 

- Shield area: Electroplated with tin, nickel, or silver (to improve conductive shielding performance and reduce electromagnetic reflection loss); grounding treatment is applied in some cases (e.g., reserved grounding contacts to connect the shield to the device’s ground terminal, diverting interference signals to the ground). 

**Shielding & Functional Testing** 

- Electrical performance testing: Test dome conduction resistance and actuation force (to ensure normal key function). 

- Shielding performance testing: Use EMC test equipment (e.g., spectrum analyzers) to measure the shield’s attenuation of electromagnetic signals at specific frequencies (e.g., 1MHz-1GHz), ensuring compliance with EMI/EMC standards (e.g., CE, FCC certifications). 

- Structural testing: Inspect connection strength and dimensional accuracy (e.g., shield sidewall height, sealing) to avoid shielding failure due to structural defects. 

**Packaging & Integration** 

Usually packaged in arrays (fixed by adhesive film) for subsequent assembly with PCBs or key modules; some products have reserved welding points to fix the shield to the device’s ground terminal. 

EMI-shielded metal domes are mainly used in scenarios with high electromagnetic compatibility requirements, such as smartphone RF modules, 5G communication equipment, and medical instruments. Their production demands higher mold precision (to control both spring elasticity and shield sealing) and material performance matching.