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Designing for Manufacturability: Through-Hole vs. Surface Mount

Posted by Circuit Pak, Inc. on | Leave a Comment

Designing for manufacturability (DFM) optimizes the design, materials, and manufacturing process of a product so that it can be produced as efficiently and cost-effectively as possible. For printed circuit boards (PCBs), a key DFM consideration is how the board is assembled, whether it’s with through-hole technology (THT) or surface mount technology (SMT). Here, we take a closer look at through-hole assembly and surface mount assembly options to help you choose the best production method for your PCB assembly.

Through-Hole Technology (THT)

Through-hole technology (THT) or through-hole assembly is a method of producing printed circuit boards in which the PCB has holes and leads are soldered through those holes. The result is a stronger, more dynamic board. It can handle a greater volume of parts and heavier components, as well as higher currents and voltage levels. Components on THT PCB assemblies are also much easier to rework, repair, or remove over time because doing so does not require specialized tools.

To decide if THT is right for your PCB assembly, consider these specific factors:

  • Holes and Leads: The PCB first has holes bored into it. Then, manufacturers insert leads through the holes and solder them to pads.
  • Manual or Automated: Automated machines can insert and solder the leads into place, or the process can be done manually.
  • Size of Components: THT components are larger to accommodate the insertion technique and placement through the PCB.
  • Components Used: THT constructions typically feature capacitors, inductors, integrated circuits (ICs), and resistors.

Typical applications of through-hole assembly PCBs include the following:

  • Aerospace: Aerospace assemblies rely on THT-style PCBs because the connections are less likely to fail.
  • Automotive: Because THT PCBs are reliable and robust, manufacturers often prefer them for control modules in automotive applications.
  • Industrial Electronics: Manufacturers use THT construction for industrial motor controllers, power supplies, and sensors.

Surface Mount Technology (SMT)

Surface mount technology (SMT) PCBs feature smaller, high-density components attached to the surface of the PCB. The parts are miniaturized to facilitate more compact designs on the limited surface area. This style of production is cost-effective, as the boards are smaller and don’t require as many drilling processes. Surface mount assembly PCBs also save time and money to assemble, as the entire process can be automated to reduce labor costs.

Here are the main features to consider with SMT PCB assemblies:

  • Automation: SMT processes are relatively simple but require a high degree of accuracy, which automation can easily provide.
  • Size of Components: SMT components are smaller and lighter than THT components.
  • Components Used: SMT PCBs have miniaturized microcontrollers, capacitors, ICs, and resistors.
  • Direct Soldering: Parts are applied to the PCB via direct soldering, a process that can be automated.

Due to the direct contact between the components and the PCB itself, SMT boards tend to have better heat dissipation. However, they must be properly designed to ensure effective thermal performance. Some of the common applications of SMT PCBs are:

  • Consumer Electronics: Small consumer electronics, such as tablets, wearable tech, and smartphones, benefit most from SMT design.
  • Miniaturization: SMT PCBs benefit projects that have compact form factors, such as medical devices.
  • Telecommunications: These PCBs are ideal for telecommunication devices and assemblies.

Tips for PCB Design

When you’re choosing between THT and SMT processes for the manufacturability of your PCB assembly, consider these five elements:

  • Clearance and Tolerances: Each component requires enough clearance for accurate initial placement and proper function during use.
  • Thermal Dissipation: In addition to integrating the proper space between components, you should also address any other potential thermal management issues with the board.
  • Component Placement: Your design should allow for the best possible component placement to facilitate efficient assembly processes.
  • Design for Testability: Designs also need to accommodate testing during production so errors can be caught as early as possible. Build in test points.
  • Pad Design: Different industries set different requirements for pad sizes and shapes, which may affect what manufacturing method is best.

Through-Hole Assembly and Surface Mount Assembly PCBs From Circuit Pak

Both THT and SMT assembly processes offer significant advantages, but each one works best for specific industries and use cases. Consider your project parameters, budget, expected product use case, and environmental factors to determine which one is best. Reach out to the experts at Circuit Pak to discuss both methods in more detail, or request a quote to get started.