Design Factors for Optimal Performance

Leveraging surface-mount technology (SMT), surface-mount devices attach directly to printed circuit boards in electronics, providing significant advantages over their through-hole mounting counterparts. SMD benefits include:

• Smaller Size: Occupying less space on the board enables efficient use of real estate and facilitates the design of smaller electronics.
• Reduced Need for Drilled Holes: Without requiring drilled holes for placement, engineers can design components with higher routing density, especially more compact ones.
• Placement Flexibility: Because SMDs can be positioned on both sides of the circuit board, component density and connection speed are increased.

Understanding the characteristics of diverse SMD components and how to apply them to product design can lead to products that last longer and perform better.

SMD Package Design Considerations

There are several factors that go into determining the appropriate SMD package for a product’s design and application:

• Power Dissipation & Thermal Characteristics: Confirm the package can manage your design’s required power levels without overheating.
• Signal Integrity: Determine how package design influences signal performance, especially in high-frequency applications.
• Component Cost and Application Needs: Selection should balance specific application needs and budgetary constraints.
• Space Constraints: Optimize your design by assessing the available area for component placement on the board.

Because package choice dramatically impacts overall performance, we created an SMD Dimension Selection Guide with over 140 types and their specifications.

Additional Variables That Influence Selection

From mechanical properties to environmental compliance and availability, there are several additional factors engineers should review when selecting an SMD package:

• Mechanical Strength: Consider how well the package withstands mechanical stress, such as vibration and shock, during assembly and operation.
• Moisture Sensitivity Level (MSL): Review the package’s susceptibility to moisture absorption, which can negatively impact soldering processes as well as long-term reliability.
• Lead Configuration: Evaluate the type and placement of leads like gull-wind or J-leads for ease of soldering and suitability with current manufacturing processes.
• Compatibility with Assembly Processes: Verify that your chosen package will work with your assembly methods, such as automated pick-and-place or reflow soldering.
• Supply Chain & Availability: Determine availability from multiple suppliers, paying close attention to lead times and their impact on design timelines.
• Environmental Compliance: Confirm the package adheres to all applicable environmental regulations, such as RoHS compliance.
• Electrical Performance: Weigh characteristics like parasitic capacitance and inductance, which can impact performance in high-frequency applications.
• Effects of Working Conditions: Factor in how long-term exposure to temperature, humidity, and other environmental conditions could influence performance and reliability.
• Total Cost of Ownership: Consider expenses related to assembly, testing, and potential failures throughout the product lifecycle, as well as initial component cost.

Effective Thermal Management: A Must for SMD Circuit Reliability

Excessive heat can cause component failure, reduced performance, and shortened lifespan. To help manage thermal load and performance, the following techniques should be examined:

• Thermal Pads: Elements made of silicone or thermal interface materials (TIMs) are placed between the component and the PCB, providing a pathway for heat to move away from the components to ensure operation within safe temperatures.
• Heat Spreaders: Metallic or thermally conductive plates are used to distribute heat away from the high-temperature components across a larger area of the PCB to prevent hotspots and enhance thermal efficiency.
• Proper PCB Layout Design: The PCB layout can be optimized for thermal management with various methods, including placing high-power components away from sensitive areas, ensuring adequate spacing between components to allow airflow, and using thermal relief techniques in copper pours. Thermal vias (thermal pads) can also be incorporated to connect heat-generating components to larger copper areas on the board for better heat dissipation.
• Active Cooling Solutions: When passive methods are not enough, active solutions, such as fans, heatsinks, or liquid cooling systems, can be added to significantly reduce operating temperatures and enhance reliability.
• Thermal Simulation and Analysis: Leveraging thermal simulation software during the design phase to predict heat flow within a circuit can help identify potential hotspots and inform design optimization before prototypes are produced.
• Material Selection: Choosing PCB substrate and component materials with high thermal conductivity can facilitate better dissipation, and insulating materials help protect sensitive areas.
• Monitoring Systems: Using thermal monitoring systems to inform dynamic adjustments to cooling strategies and alert engineers to potential overheating before component failure.

Engineers can utilize these techniques to help ensure their SMD circuits remain efficient and reliable, enhancing their performance in various applications.

Download our selection guide for 140+ SMD package size charts used in modern power electronics.

Choosing the Right SMD Package

With so many variables to review, finding the right SMD package can be complex. MCC is here to help, providing expert insights and guidance on various package types, their applications, and design considerations.

Whether you’re an experienced engineer or in the early stages of your career, use these resources to enhance decision-making, and ultimately, the product:

Guide to Surface Mount Devices Package Types

SMD Applications & Examples