What material is the metal spring of the membrane switch made of?
The selection of the material for the metal spring clips (also known as pot clips) of the membrane switch needs to take into account factors such as conductivity, elasticity, corrosion resistance, cost, and high humidity conditions. Here is a detailed analysis of the materials:
1. Comparison of Core Materials
| Material | Electrical Conductivity (IACS) | Elastic modulus (GPa) | Corrosion Resistance | Cost | Life Span | Applicable Scenarios |
| Stainless Steel 301 | 2-3% | 200 | Good | Low | 100-300 million cycles | General-purpose, cost-sensitive |
| Stainless Steel 304 | 2-3% | 200 | Excellent | Low | 100-300 million cycles | Highly humid environment, corrosion-resistant |
| Phosphor Bronze | 15% | 110 | Good | Medium | 50-100 million cycles | Requires better electrical conductivity |
| Beryllium Copper | 22% | 130 | Good | High | 100-500 million cycles | High reliability, high-frequency operation |
| Brass | 28% | 100 | Poor | Low | 50-100 million cycles | Low-end application, not recommended |
2. Surface Treatment Comparison
| Surface Treatment | Contact Resistance | Corrosion Resistance | Cost | Applicable Scenarios |
| Nickel Plating | Medium | Good | Low | Home appliances, general electronic devices |
| Silver Plating | Low | Poor (Susceptible to Sulfidation) | Medium | Low humidity environment, high conductivity requirements |
| Gold Plating | Extremely Low | Excellent | High | Precision instruments, medical equipment, high-end devices |
3. Selection suggestions in high-humidity environments
In high-humidity conditions (humidity > 80%) with intense industrial activities, the air contains more hydrogen sulfide (H₂S) and sulfur dioxide (SO₂), which accelerate the corrosion and sulfidation of metal shrapnel. Therefore, when selecting, special attention should be paid to the corrosion resistance and anti-sulfidation ability.
| Environmental factors | Effect on shrapnel | Recommended materials | Recommended surface treatment |
| High humidity | Accelerates electrochemical corrosion, resulting in increased contact resistance | Stainless steel 304, beryllium copper | Gold plating, nickel plating |
| Industrial pollution | Hydrogen sulfide and sulfur dioxide cause sulfidation, resulting in increased contact resistance | Stainless steel 304, beryllium copper | Gold plating (resistant to sulfidation) |
| High temperature | Accelerates chemical reactions, reducing the lifespan of the shrapnel | Stainless steel 304, beryllium copper | Gold plating (resistant to high temperature) |
| Salt spray | Accelerates corrosion, causing shrapnel to break apart | Stainless steel 304, beryllium copper | Gold plating (resistant to salt spray) |
4. Selection Steps
Determine the conductivity requirements:
High conductivity (contact resistance < 1Ω): Select beryllium copper or phosphor bronze, and choose surface treatment of gold plating or silver plating.
General conductivity (contact resistance < 5Ω): Select stainless steel 304, and choose surface treatment of nickel plating.
Determine the lifespan requirements:
High lifespan (> 1 million cycles): Select beryllium copper or stainless steel 304.
General lifespan (50 - 1 million cycles): Select phosphor bronze or stainless steel 301.
Determine the environmental requirements:
High humidity/high pollution environment: Select stainless steel 304 or beryllium copper, and choose surface treatment of gold plating.
General environment: Select stainless steel 301, and choose surface treatment of nickel plating.
Determine the cost budget:
Cost-sensitive: Select stainless steel 301, and choose surface treatment of nickel plating.
Performance priority: Select beryllium copper, and choose surface treatment of gold plating.
Summary: Metal Fragment Material Selection Guide
| Requirements | Recommended Material | Recommended Surface Treatment | Reasons |
| Cost-sensitive | Stainless Steel 301 | Plated Nickel | Lower cost, performance meets general requirements |
| High humidity environment | Stainless Steel 304 | Plated Gold | Resistant to corrosion, anti-sulfation |
| High conductivity | Bezol Copper | Plated Gold | Excellent conductivity, long lifespan |
| Long service life | Bezol Copper | Plated Gold | Excellent elasticity, long fatigue lifespan |
| Precision instruments | Bezol Copper | Plated Gold | Stable contact resistance, reliable signal transmission |
| Medical equipment | Stainless Steel 304 | Plated Gold | Resistant to corrosion, anti-sulfation, in line with medical standards |
| Automotive electronics | Bezol Copper | Plated Gold | High reliability, resistant to vibration, resistant to high temperatures |
| Industrial control | Stainless Steel 304 | Plated Nickel | Resistant to corrosion, moderate cost |
Suggestion: When choosing the material for the metal shrapnel, stainless steel 304 + gold plating is the best combination for dealing with high humidity environments. Sample testing is the only reliable method to verify the reliability of the shrapnel. It is essential to conduct thorough tests under harsh conditions such as high humidity, high temperature, and salt fog.