In modern electronic devices, control boards serve as the core components responsible for implementing complex functions, and relays are indispensable elements on these boards. Their role extends beyond functioning as simple switches; relays are critical to ensuring the stable operation of the equipment. From the perspective of a control board assembly engineer, this article delves into the fundamental principles, selection criteria, layout considerations, and testing and maintenance of relays to help readers gain a comprehensive understanding of their applications in control boards. Today, we will focus on relay placement and testing, examining the pivotal role of relays in control board design and manufacturing.

PCB Layout

• Space Requirements: Relays tend to be relatively large components, so careful planning is required when determining their placement on the PCB. Sufficient spacing must be ensured between relay pins and other components’ pads and traces to prevent short circuits or soldering issues.
  • Example: When designing an electric bed control board, relay placement should maintain a reasonable distance from motor drive circuits and power modules to avoid unnecessary interference or overheating during current flow.
• Thermal Considerations: Relays generate heat during operation, especially in high-current applications. PCB designs should account for heat dissipation by incorporating features like additional thermal vias, heat-conductive materials, or increasing copper area near the relay.
  • Example: In high-power devices, adding thermal vias and heat-conductive pads near relays can reduce operational temperatures and extend the relay’s lifespan.
• Electromagnetic Interference (EMI) Protection: When relays open or close, they generate electromagnetic interference, which can affect other sensitive components on the control board. Proper relay placement relative to signal lines and microprocessors is essential. Adding ground isolation or shielding can minimize EMI.
  • Example: In control boards for communication equipment, placing relays away from signal processing circuits and adding ground planes or shielding helps maintain signal integrity and reduces EMI.

Installation Methods

• Installation Type: Relays are typically available in through-hole technology (THT) or surface-mount technology (SMT). THT relays are preferred for higher current applications, while SMT relays suit compact designs.
  • Example: THT relays are commonly used in industrial control boards due to their ability to handle higher currents and their superior mechanical strength, making them suitable for long-term use. In contrast, SMT relays are favored in compact consumer electronics for saving space and simplifying assembly.
• Soldering Considerations: During the soldering process, temperature control and timing are crucial to avoid overheating and damaging the relay’s internal structure. This is especially important for SMT relays, where excess solder can compromise connections.
  • Example: In automated soldering processes, the ideal soldering temperature for relays is between 240°C and 260°C. Excessive heat exposure can damage internal coils or contacts. After soldering, visual or X-ray inspections are recommended to ensure soldering quality meets standards.

Through proper PCB layout and precise installation techniques, relay operation in control boards can be stabilized, ensuring longevity and reliability. These steps are vital to producing high-reliability, low-failure-rate products.

Functional Testing

• Contact Resistance Testing: Contact resistance measures the resistance between relay contacts when closed. Low contact resistance ensures minimal voltage drop and power loss during current flow.
  • Example: In an electric bed control board, high contact resistance in relays can reduce motor drive efficiency, impairing the bed’s lift function. Therefore, production tests must rigorously maintain contact resistance within specified limits.
• Pull-in and Release Voltage Testing: Pull-in voltage is the minimum voltage required to activate the relay, while release voltage is the voltage at which the relay returns to its rest state. These parameters determine relay sensitivity and operational voltage range.
  • Example: In smart home appliance control boards, excessive pull-in voltage can prevent relays from operating at rated voltage levels. Testing ensures pull-in and release voltages meet design specifications, guaranteeing product stability.

Durability Testing

• Electrical Durability Testing: This test assesses a relay’s performance after repeated operations, including whether contacts function properly and whether electrical performance remains stable over time.
  • Example: In industrial control boards, where relays undergo frequent switching, durability testing ensures the relay maintains contact integrity and functionality after numerous cycles, enhancing equipment reliability.
• Mechanical Durability Testing: This test evaluates a relay’s physical structure under repeated mechanical operations without power, checking for wear and deformation of key components like springs, cores, and contacts.
  • Example: In automotive electronic control boards, mechanical durability is crucial due to the vibrations and repeated operations experienced during vehicle use. This test ensures the relay operates reliably in such harsh environments.

These functional and durability tests allow manufacturers to verify relay performance and reliability, ensuring control board quality and long-term stability. These testing steps are essential for product quality control and building customer trust.

Conclusion

In summary, relays play a critical role in control board design and manufacturing. From placement and layout to testing and validation, every stage influences control board performance and reliability. As technology advances, relays are evolving to offer more intelligent and efficient solutions. As control board engineers, mastering relay usage techniques and staying informed of the latest trends helps improve product quality and extend equipment lifespan, providing superior solutions to customers.