Placing component on a THT PCB

SMD vs THT: Which is Best for Your Semiconductor PCBA Design?

A wise person once said that the only constant in life is change. And this simple truth can be observed virtually everywhere. Yet, people often find it difficult to accept change—and that’s understandable. We are, in fact, creatures of habit, and change typically means breaking a habit or two. However, incorporating change does not always mean that what was done previously must be abandoned completely.

An examination of the history of circuit board manufacturing indicates that the process of building PCBAs has gone through evolutionary modifications as equipment technology has advanced and improved. Similarly, board and component sizes have continually decreased in size, which has led to the expanded usage of PCBAs and smarter products. Even with the introduction of more advanced semiconductor components and surface mount technology (SMT), older through-hole technology (THT) continues to be utilized. The question for designers is when is it best to opt for SMD vs THT for your semiconductor board design?

The Challenges of New Product Introduction

Although PCBAs and electronics are used in most industrial products made today, the electronics industry is still highly competitive—especially when introducing a new semiconductor board such as an evaluation board built around a high-performance semiconductor IC (e.g. MCU or FPGA).

Design Challenges

Semiconductor evaluation boards, although customized, are typically intended to be implemented for applications that may cross several industries. Therefore, designs often include different signal types that present unique EMI and grounding concerns. This makes semiconductor and board material selections, as well as tracing and via design, critical for performance optimization and manufacturing efficiency.

Manufacturing Challenges

Building boards designed to be both comprehensive and adaptable can be challenging for several reasons. For example, non-traditional stackups may be required to accommodate different signal types. This means that multiple impedance control or dielectric constant requirements may need to be met, not just a single constraint. Another significant concern for high-performance semiconductor boards is thermal management for manufacturing.

Design Validation Challenges

A standard aspect of your design process should be design verification. Although your CM will perform verification, such as checking for DFM rules compliance, you should also do this to help facilitate an efficient development process. Additionally, be sure to incorporate an effective design validation or testing regimen for your semiconductor PCBA development process. This may include board testing and inspection to ensure good solder joint quality, decontamination and structural integrity.

As indicated by the list above, bringing up a new semiconductor PCBA is a complex process that extends throughout the DBT cycle. Another important decision that will impact many of the stages of development is whether to use SMD vs THT for the primary semiconductor component.

The Guide to PCBA Development for Semiconductor Applications

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How to Choose Between SMD vs THT for Your Design

For semiconductor packaging, SMD is the newer technology, and it has distinct advantages. Chief among these is the ability to route more signals from high-pin count semiconductors in a compact space by utilizing multiple layers. The alternative, THT, is older but has advantages as well. For example, components attached to leads that run vertically through the entire board have much stronger connections; they are also far less likely to become unattached due to vibration or other motion. As many high-performance semiconductor chips are manufactured in both SMD and THT packages, you should employ guidelines to help you make the best selection for your design.

Design Attributes/Requirements SMD Either THT
If the component is heavy X
If minimal surface area is an objective X
If the board has size restrictions X
If signal integrity requirements mandate no stubs from drill holes X
If thermal protection of components is a high concern X
If your board is a flex board X
If  the board will be subjected to constant motion or vibration? X
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  • Performs multiple automated inspections during PCB assembly to ensure quality for prototyping and low volume production.
  • Comprehensive process documentation, including testing regimens and verifications.

As shown in the table above, the choice of whether to use a SMD vs THT semiconductor is not a simple one. It should be based on design requirements and constraints, as well as CM capabilities; some manufacturers shy away from via-in-pad fabrication. At Tempo Automation, the industry leader for fast, high-quality PCBA prototyping and on-demand production, we will work with you to select the best component technology for your design.

And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on SMD vs THT for your semiconductor board design, contact us.

 

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