E密斯: The "Invisible Guardian" and "Information Bridge" for Modern Industrial Equipment Contact Gaskets

In today's era of increasingly sophisticated and high-power electronic devices, Electromagnetic Compatibility (EMC), thermal efficiency, and structural stability have emerged as the three key factors determining product reliability. As the core of electronic devices, PCBs (Printed Circuit Boards) face severe challenges in their working environment. Against this backdrop, E密斯Contact PadAs a classic and efficient solution, it plays an indispensable role in the electromagnetic shielding and grounding applications of PCBs.

Figure 1: E密斯 Gold Plated Contact Pad

I. Understanding Materials and Their Characteristics

Material Definition:

H62 is a common brass alloy, composed of approximately 60.5% to 63.5% copper (Cu) and the remainder zinc (Zn). This copper-zinc ratio strikes a balance between cost, mechanical properties, and conductivity.

Outstanding balance.

2. Core Features:

• Excellent Conductivity and Thermal Conductivity: As a copper alloy, H62 boasts exceptional electrical and thermal conductivity, enabling it to provide low impedance grounding and shielding pathways while assisting in dissipating heat on PCBs.
• Thermal management of components.
• Excellent Mechanical Properties and Elasticity: The H62 material possesses certain elasticity and ductility. When processed into shims (usually in the form of springs), it can produce and maintain spacing between two connecting surfaces.
• Maintaining consistent contact pressure, compensating for structural tolerances, ensures reliable contact under vibration or shock conditions.
• Easy to Process and Form: H62 brass is easy to stamp, bend, and shape, enabling the production of various complex-shaped shielding leaf springs to accommodate different PCB and housing structural designs.
• Weldability: The H62 shim can be securely attached to the PCB through welding methods such as reflow soldering or wave soldering, forming a permanent and reliable connection.
• Cost-Effective: Compared to high-end shielding materials like beryllium copper and gold-plated stainless steel, H62 brass offers a lower cost, making it an ideal choice for many consumer electronics and industrial control products.

II. Main Application Scenarios of Conductive Shims in PCB Boards

Conductive washers' applications on PCBs mainly revolve around two core functions: electromagnetic interference (EMI) shielding and electrical grounding.

Shielding connection between PCB and metal casing/shielding cover:

This is the most common application. At the edges or specific areas of PCBs, there are designated termination areas, usually plated with gold or tin-coated copper foil. H62 conductive spring strips are pre-welded or crimped onto these termination areas.

When the PCB is inserted into the metal housing or covered with a metal shielding cover, the spring is compressed, ensuring a tight metal contact between the housing/shielding cover due to its elasticity, thereby:

• Create a Faraday cage: Enclose sensitive circuits on the PCB (such as MCUs, RF modules) within a continuous conductive cavity, effectively blocking external electromagnetic interference from penetrating.
• 抑制内部辐射： Prevent electromagnetic noise from high-frequency circuits on PCBs (such as clock circuits, switching power supplies) from radiating outward, to avoid affecting other devices or causing the entire product to fail EMC testing.

2.接地 between modules/sub-boards and the mainboard:

Internally, there may be multiple PCB modules. For instance, a radio frequency module needs to maintain the same reference potential as the mainboard by grounding. Contact pads can be used for grounding connections between two circuit boards, ensuring signal integrity and reducing common-mode interference.

3. Providing grounding or heat dissipation paths for specific components:

For large components requiring individual grounding or heat dissipation, a ground pad can be designed on the PCB beneath them, along with a contact washer. As the component is installed and secured, it will press the washer tightly, creating an additional low-impedance path.

III. Advantages and Limitations Compared to Other Materials

Advantages:

• The King of Value for Money: H62 is one of the most cost-effective solutions, ensuring excellent shielding performance.
• Touch Reliability: Its inherent elasticity and resistance to stress relaxation ensure long-term contact pressure maintenance, outperforming solutions that solely rely on conductive adhesives or conductive fabrics.
• Environmental Adaptability: The surface is typically tin-plated, nickel-plated, or treated with a ternary alloy, effectively preventing brass oxidation and maintaining good weldability and long-term contact stability.

2. Limitations:

• H62's elasticity is inferior to beryllium copper: Compared to high-performance beryllium copper alloys (such as C17200), H62 has a lower elastic limit and fatigue life. BeCu springs offer superior long-term reliability in environments requiring frequent disassembly or extreme vibration.
• Corrosion Resistance: While the surface coating offers protection, its long-term corrosion resistance in harsh environments with high salt雾 and humidity (such as marine or outdoor communication) is not as good as stainless steel or phosphor bronze.
• Heavier Weight: Copper has a higher density, making it less of a preferred choice in applications where weight is extremely sensitive (such as aerospace and high-end portable devices).

Key Considerations for Using Contact Pads in PCB Design

To fully harness the effectiveness of conductive shims, meticulous planning is essential during the PCB design phase.

Ground Pad Design

Pad width should be slightly larger than the contact lead width of the shim to ensure a secure weld.

Surface Treatment: Recommend using Electroless Nickel Immersion Gold (ENIG) or Gold Plating for the best solderability and oxidation resistance. OSP (oxidation prevention) treatment is not suitable for soldering.

2. Installation Method Selection:

SMT Soldering: This is the most mainstream automated installation method. The pads are pre-packaged and precisely placed onto the PCB pads by the SMT machine, followed by welding in a reflow oven. Design must adhere to SMD pad specifications.

Design Standards.

Perforated Welding: Some gasket designs feature pins that can be inserted into PCB through-holes for wave soldering, resulting in higher connection strength; however, the degree of automation is slightly lower.

3. Structural and Design Coordination

Compression Volume and Force: Collaboration with structural engineers is essential to determine the free height of the gasket, the compression volume, and the corresponding contact pressure. Insufficient pressure leads to poor contact, while excessive pressure may cause the gasket to deform permanently or bend the PCB.

The mating surface: The metal housing or shielding cover surface in contact with the gasket should be flat and clean, free of insulating coatings (such as paint, anodized layer) to ensure low impedance contact.

V. Summary and Outlook

E密斯' Contact Shrapnel, with its exceptional comprehensive performance and cost-effectiveness, has emerged as a classic solution for PCB electromagnetic shielding and grounding issues across a broad spectrum of fields, from consumer electronics to industrial control. Although it is not the top-performing,

The material is not the most advanced, yet it remains the "gold standard" that meets the needs of the vast majority of application scenarios.

With the development of 5G, the Internet of Things, and automotive electronics, the requirements for shielding will become increasingly stringent. In the future, contact pads may complement more new materials (such as conductive elastomers, metallized plastics) or surface treatment techniques.

Further optimized in technology and structural design to meet the challenges of higher frequencies, smaller spaces, and harsher environments. However, in the foreseeable future, it will still be an indispensable and reliable tool in the PCB engineer's toolkit.

E密斯 has been specializing in the production of various precision metal shot and beryllium copper spring strips for over 15 years. With deep expertise in material selection, electroplating, and precision stamping, we offer customized bulk services in connector systems and shielding solutions to our clients.