SMD vs Through-Hole Components: Complete Comparison

Every PCB design starts with a fundamental decision: SMD vs through hole components. This choice affects everything from board size and assembly cost to reliability and repairability. Having worked on projects ranging from high-volume consumer electronics to rugged industrial equipment, I’ve learned that neither technology is universally better—the right choice depends entirely on your specific requirements.

This guide breaks down the SMT vs THT comparison across every factor that matters: size, cost, performance, assembly, and reliability. Whether you’re optimizing a new design or deciding how to approach a prototype, understanding these tradeoffs will help you make informed decisions that serve your project well.

Understanding SMD and Through-Hole Technology

Before diving into comparisons, let’s clarify the terminology that often confuses newcomers to PCB design.

What is Surface Mount Technology (SMT)?

Surface Mount Technology (SMT) is a method of mounting electronic components directly onto the surface of a printed circuit board. Components designed for this process are called Surface Mount Devices (SMD). The terms SMT and SMD are related but distinct: SMT refers to the assembly process, while SMD describes the components themselves.

SMT assembly follows a highly automated workflow: solder paste is applied to PCB pads through a stencil, pick-and-place machines position SMD components onto the paste, and the assembly passes through a reflow oven where the solder melts and creates permanent connections.

What is Through-Hole Technology (THT)?

Through-Hole Technology (THT), also called Through-Hole Mounting (THM), involves inserting component leads through holes drilled in the PCB and soldering them on the opposite side. This older technology predates SMT and remains relevant for specific applications.

Through-hole assembly can be manual or semi-automated. Components are inserted into plated through-holes (PTH), then soldered using wave soldering, selective soldering, or hand soldering techniques.

SMD vs Through Hole: Key Differences at a Glance

Size and Space Efficiency: SMT vs THT

The most obvious difference in the SMD vs through hole comparison is physical size. SMD components are dramatically smaller than their through-hole counterparts.

SMD Component Sizes

SMD passive components (resistors, capacitors) use standardized size codes. The code represents length and width in hundredths of an inch:

The 0603 and 0402 sizes dominate modern designs, offering excellent balance between density and manufacturability. Sizes 0201 and smaller require advanced pick-and-place equipment and are typically reserved for smartphones, wearables, and other ultra-compact products.

Through-Hole Component Sizes

Through-hole components use standardized lead pitches rather than body sizes. Common pitches include 2.54mm (0.1″), 5.08mm (0.2″), and 7.62mm (0.3″). A typical through-hole resistor measures 6mm long with 10mm lead spacing—vastly larger than even the biggest SMD alternatives.

Space Impact on PCB Design

SMT enables component placement on both sides of the PCB, effectively doubling available real estate. Through-hole components typically mount on one side only, with leads occupying space on the opposite side. For complex designs, this density advantage often determines whether a design fits on a reasonably sized board.

Assembly Process: SMT vs THT Manufacturing

Assembly methods differ fundamentally between the two technologies, with significant implications for cost, speed, and quality.

SMT Assembly Process

The SMT process is highly automated and efficient:

Solder Paste Application: A precision stencil applies solder paste to PCB pads. Stencil thickness (typically 0.1-0.15mm) and aperture design affect paste volume.

Component Placement: Pick-and-place machines position components at rates of 10,000-50,000+ components per hour. Modern machines achieve placement accuracy of ±0.025mm.

Reflow Soldering: The assembly passes through a controlled temperature profile, typically peaking at 230-250°C for lead-free solder. All joints form simultaneously in a repeatable process.

Inspection: Automated Optical Inspection (AOI) verifies component presence, orientation, and solder quality at production speeds.

Through-Hole Assembly Process

THT assembly involves more manual steps:

Component Insertion: Manual insertion or semi-automated machines place components through PCB holes. Much slower than SMT placement.

Soldering: Wave soldering passes the board over molten solder, or selective soldering targets specific areas. Hand soldering remains common for prototypes and small volumes.

Inspection: Visual inspection is straightforward since joints are visible from the solder side.

Assembly Speed Comparison

The speed difference is dramatic. A modern SMT line processes thousands of components per hour with minimal human intervention. THT assembly, even with automation assistance, processes tens to hundreds of components per hour and often requires significant manual labor.

Cost Analysis: SMD vs Through Hole Economics

Cost considerations vary significantly based on production volume and product requirements.

Low-Volume and Prototype Costs

For prototypes and small batches, THT often costs less overall:

• No stencil fabrication required
• Simple hand soldering with basic equipment
• Easier component handling and placement
• Lower rework costs when design changes occur

SMT prototyping requires stencils (or expensive stencil-free techniques) and reflow equipment. However, many PCB assembly services now offer affordable SMT assembly even for small quantities.

High-Volume Production Costs

For production volumes above a few hundred units, SMT wins decisively:

• Automated assembly eliminates labor costs
• Smaller components cost less
• Smaller PCBs reduce material costs
• Higher throughput maximizes equipment utilization
• Consistent quality reduces inspection and rework

The crossover point depends on board complexity and assembly service rates, but SMT typically becomes more economical above 100-500 units.

Total Cost Considerations

Beyond assembly costs, consider:

• PCB Cost: SMT boards may require more layers for routing, but smaller size reduces material cost
• Component Cost: Most SMD components cost less than THT equivalents at equivalent specifications
• Testing Cost: SMT boards require more sophisticated test fixtures
• Rework Cost: THT rework is simpler and cheaper when needed

Electrical Performance: High-Frequency Advantages

When comparing SMT vs THT for electrical performance, SMT holds significant advantages at higher frequencies.

Lead Inductance and Parasitic Effects

Through-hole component leads introduce parasitic inductance (typically 5-15nH per lead) and capacitance that degrade high-frequency performance. These parasitic elements cause:

• Signal distortion at high frequencies
• Increased noise susceptibility
• Reduced bandwidth in analog circuits
• EMI issues from longer current loops

SMD components have minimal lead length, reducing parasitic inductance to under 1nH. This makes SMT essential for RF circuits, high-speed digital designs, and precision analog applications.

Frequency Performance Guidelines

Modern microprocessors, wireless modules, and high-speed interfaces all require SMT assembly for proper operation. For lower-frequency circuits like power supplies and basic digital logic, THT remains viable.

Mechanical Strength and Reliability

Mechanical considerations often determine the SMD vs through hole decision for specific applications.

Through-Hole Mechanical Advantages

THT components excel in mechanically demanding environments:

• Stronger Connections: Leads passing through the board and soldered on both sides create robust mechanical bonds
• Vibration Resistance: The through-board anchoring resists forces that would shear SMD solder joints
• Connector Support: High-insertion-force connectors require THT mounting to withstand repeated mating cycles
• Thermal Cycling: Through-hole joints better tolerate CTE mismatch between PCB and components

SMD Reliability Considerations

SMD connections rely entirely on surface solder joints, which can fail under:

• Mechanical shock or drop impacts
• Repeated thermal cycling
• Board flexing during installation or use
• Vibration in automotive or industrial environments

However, proper design mitigates these concerns. Techniques include underfilling critical components, adding mechanical retention features, and selecting appropriate package sizes for the application environment.

Application-Specific Recommendations

Use Through-Hole for:

• Connectors subject to insertion forces
• Components in high-vibration environments
• High-power components requiring heat sinking
• Transformers and inductors with significant mass
• Military and aerospace applications with extreme reliability requirements

Use SMD for:

• General consumer electronics
• Space-constrained designs
• High-frequency circuits
• Cost-sensitive high-volume production
• Portable and handheld devices

When designing with Altera FPGA devices, package selection often determines whether SMT-only assembly is possible or whether through-hole connectors require mixed assembly.

Read more IC types:

ADC vs DAC: Analog-to-Digital and Digital-to-Analog Converters Guide

ASIC Design Guide: Application-Specific Integrated Circuits

Audio Amplifier ICs: Types, Selection Guide & Applications

BGA (Ball Grid Array) Package: Guide to High-Density ICs

Codec ICs Explained: Audio & Video Encoding/Decoding

Comparator IC: Working Principle, Types & Applications

CSP & WLCSP: Chip Scale Packaging for Miniaturization

Data Converter ICs: ADC, DAC & Sigma-Delta Converters

Digital Logic ICs: AND, OR, NOT Gates & Flip-Flops Guide

Digital PCB & IC Design: Logic Circuit Board Layout Guide

DIP (Dual In-Line Package): Classic IC Package Explained

DSP (Digital Signal Processor) IC Guide for Beginners

ECL (Emitter-Coupled Logic): High-Speed IC Technology

FPGA vs ASIC: Complete Comparison Guide [2025]

GaAs & SiGe: High-Frequency Semiconductor Technologies

IC Fabrication Technologies: CMOS, BiCMOS, TTL & More

IC Package Types: Complete Guide (DIP, SMD, QFP, BGA)

LDO vs switching regulatorLDO vs Switching Regulator: Which Voltage Regulator to Choose?

Microprocessor vs Microcontroller: Key Differences Explained

Mixed-Signal ICs: Bridging Analog and Digital Worlds

Operational Amplifier (Op-Amp) Basics: Complete Beginner’s Guide

PLL (Phase-Locked Loop) IC: Working Principle & Applications

Power Management IC (PMIC): Complete Selection Guide

RF IC Basics for Wireless Applications: A Practical Radio Frequency IC Guide

SiP (System in Package) & MCM: Advanced IC Packaging Guide

SMD vs Through-Hole Components: Complete Comparison

SOIC vs SSOP vs TSSOP: Small Outline Package Comparison

TTL vs CMOS Logic: Complete Comparison Guide

Types of Analog Integrated Circuits: Complete Guide

Types of Digital Integrated Circuits: Complete Guide

Types of Memory ICs: RAM, ROM, Flash, EEPROM Explained

Voltage Regulator ICs Explained: LDO, Linear, and Switching Types

What is a Microcontroller? Beginner’s Complete Guide

Thermal Management: Heat Dissipation Differences

Power dissipation capabilities differ significantly between SMD and through-hole components.

Through-Hole Thermal Advantages

Larger through-hole packages can dissipate more power:

• More surface area for convection and radiation
• Longer leads provide heat paths to the PCB
• Easy attachment of external heat sinks
• Better suited for power resistors, regulators, and transistors

A standard 1/4W through-hole resistor handles more power than most SMD resistors while running cooler.

SMD Thermal Limitations

Small SMD packages concentrate heat in tiny areas:

• Limited surface area restricts convection
• Solder joints provide the primary thermal path
• Thermal vias and copper pours required for heat spreading
• Package power ratings assume ideal PCB thermal design

Proper SMD thermal design requires attention to copper areas, thermal vias, and component spacing. Exposed pad packages (like QFN or PowerPAD) significantly improve thermal performance when correctly implemented.

Rework and Repair: Serviceability Comparison

Field serviceability often influences technology selection.

Through-Hole Rework Advantages

THT components are simple to replace:

• Accessible from the solder side
• Standard soldering iron sufficient
• No special equipment required
• Technicians can easily identify and replace failed parts

This makes THT attractive for prototyping, field-serviceable equipment, and applications where component replacement is expected.

SMD Rework Challenges

SMD rework requires more skill and equipment:

• Hot air rework stations needed for most packages
• Fine-pitch components require magnification
• Some packages (BGA, QFN) need X-ray inspection
• Risk of damaging adjacent components
• Specialized tools for each package type

While professional rework of SMD assemblies is routine, field repair by end users is generally impractical.

Mixed Assembly: Combining SMT and THT

Most real-world designs use both technologies, combining their respective strengths.

Common Mixed Assembly Applications

• Connectors: THT for mechanical strength
• Power Components: THT for thermal dissipation
• Signal Processing: SMT for density and performance
• User Interface: THT switches and displays for durability

Mixed Assembly Process Considerations

Mixed assembly complicates manufacturing:

1. SMT components placed and reflowed first
2. Through-hole components inserted
3. Selective or wave soldering for THT joints
4. Multiple thermal exposures stress SMD joints

Design for manufacturing (DFM) becomes more important with mixed assembly. Minimizing THT component count reduces process complexity and cost.

Industry Trends: The Shift Toward SMT

The electronics industry has moved decisively toward SMT over the past three decades. Today, over 90% of PCB assemblies use surface mount components as their primary technology.

Driving Forces Behind SMT Adoption

Several factors accelerated SMT dominance:

Miniaturization demands from smartphones, wearables, and IoT devices pushed designers toward smaller components. A modern smartphone contains thousands of SMD components that simply couldn’t fit using through-hole technology.

Automation benefits made SMT economically compelling. Pick-and-place machines, reflow ovens, and automated inspection systems dramatically reduced labor costs while improving quality consistency.

Component availability increasingly favors SMD. Many new ICs release only in surface mount packages, with through-hole versions never developed. Legacy through-hole parts are gradually discontinued.

Where Through-Hole Persists

Despite SMT’s dominance, through-hole technology maintains important niches:

• Power electronics requiring robust thermal management
• Industrial equipment designed for decades of service life
• Hobbyist and educational projects using breadboard-compatible parts
• Military and aerospace applications with stringent reliability requirements
• Repair-friendly designs for field service

The future likely sees continued SMT growth, but through-hole technology won’t disappear entirely. Understanding both technologies remains essential for well-rounded PCB design skills.

Useful Resources for Component Selection

When working with SMD and through-hole components, these resources prove valuable:

Component Databases:

• DigiKey, Mouser: Parametric search with footprint data
• Octopart: Cross-reference and availability
• LCSC: Extensive SMD component library

Package Standards:

• JEDEC: Industry-standard package specifications
• IPC-7351: Land pattern design guidelines
• EIA-481: Tape and reel standards

Design Tools:

• IPC-7351 Land Pattern Calculator
• Component footprint libraries (Ultra Librarian, SnapEDA)
• Manufacturer package drawings and recommendations

Assembly Guidelines:

• IPC-A-610: Acceptability of Electronic Assemblies
• J-STD-001: Soldering requirements
• Manufacturer-specific assembly application notes

Frequently Asked Questions About SMD vs Through Hole

Is SMD better than through-hole?

Neither technology is universally better—each has optimal applications. SMD excels in high-volume production, compact designs, and high-frequency circuits where small size, automated assembly, and low parasitic inductance matter. Through-hole remains superior for mechanically stressed components, high-power applications, prototyping, and situations requiring field serviceability. Most modern designs use both technologies strategically, selecting the best approach for each component based on its specific requirements.

Can I hand solder SMD components?

Yes, many SMD components can be hand soldered with practice and proper techniques. Components in 0805 and larger packages are manageable with a fine-tip soldering iron and flux. Sizes 0603 work with good technique, while 0402 and smaller require magnification and exceptional skill. Fine-pitch ICs can be soldered using drag soldering techniques. However, some packages like BGA or QFN with hidden pads cannot be hand soldered and require reflow processes.

Why are some components only available in through-hole packages?

Some components remain through-hole only due to physical constraints or performance requirements. High-power components need larger packages for heat dissipation. Transformers require bulky magnetic cores. Some connectors need through-hole mounting for mechanical strength during repeated mating cycles. Certain legacy components continue production only in through-hole form. However, the industry trend pushes toward SMD availability for most components, and SMD versions of previously through-hole-only parts continue appearing.

What is the cost difference between SMT and THT assembly?

For high-volume production, SMT assembly typically costs 30-50% less than equivalent THT assembly due to automation advantages. However, for prototypes or very small batches (under 50-100 units), THT may cost less because it avoids stencil fabrication and works with simpler equipment. The crossover point depends on board complexity, component count, and assembly service pricing. Many designers find that SMT becomes more economical above 100-500 units, though this varies significantly by project.

How do I decide between SMD and through-hole for my design?

Start by identifying components that require through-hole mounting: connectors subject to insertion forces, high-power components needing heat sinks, and any parts only available in through-hole packages. Use SMD for everything else unless you have specific reasons not to. Consider your production volume, required board size, operating frequency, and serviceability needs. For prototyping, SMD works well if you have access to reflow equipment or assembly services. Mixed designs combining both technologies often provide the best overall solution, leveraging each technology’s strengths.