When designing printed circuit boards (PCBs), one of the most fundamental choices is between Surface Mount Technology (SMT) and Through Hole Technology. Each approach offers distinct advantages and limitations that can significantly impact your product’s performance, manufacturability, and cost.
What is Surface Mount Technology (SMT)?
Surface Mount Technology involves mounting components directly onto the surface of a PCB. Components designed for SMT (known as Surface Mount Devices or SMDs) have small metal terminals or leads that are soldered to pads on the PCB surface.
Key characteristics of SMT:
- Components are typically smaller than their through-hole counterparts
- Components are placed on one or both sides of the board
- No holes are required for component leads
- Soldering is typically done using reflow soldering techniques
What is Through Hole Technology?
Through Hole Technology is the traditional method of PCB assembly where component leads are inserted through holes drilled in the PCB and soldered to pads on the opposite side. The leads physically pass through the board, creating a strong mechanical connection.
Key characteristics of Through Hole:
- Component leads pass through holes in the board
- Components are typically larger than SMT equivalents
- Provides stronger mechanical bonds
- Soldering is typically done using wave soldering or manual techniques
Key Differences: SMT vs Through Hole
| Characteristic | Surface Mount Technology (SMT) | Through Hole Technology |
| Size & Space | • Components 1/4 to 1/10 the size of through-hole• Higher component density• Components possible on both sides• Smaller overall board size | • Larger components• Lower component density• Holes occupy space on all board layers• Typically components on one side only |
| Assembly Process | • Automated pick-and-place placement• Reflow soldering process• Up to 10x faster than through-hole• Lower labour costs | • Manual or automated insertion• Wave or manual soldering• Slower production process• Higher labour requirements |
| Mechanical Strength | • Relies on solder joints for mechanical connection• More vulnerable to physical stress• May require additional support for heavy components• Less suitable for high-vibration environments | • Physically anchored through the board• Superior resistance to shock and vibration• Better for high-stress environments• Preferred for larger, heavier components |
| Electrical Performance | • Shorter connection paths• Reduced lead inductance and resistance• Better for high-frequency applications• Lower parasitic effects | • Can handle higher power loads• Better thermal dissipation• More reliable for high-current applications• Less susceptible to thermal stress |
| Cost Considerations | • Lower assembly costs in volume• Components generally less expensive• More efficient board space usage• Higher yields in automated production | • Higher assembly costs• Components typically cost more• Larger board sizes increase material costs• Lower yields in high-volume production |
| Repairability | • Requires specialised equipment• Challenging to replace components by hand• Difficult to modify during prototyping• Less suitable for field repairs | • Easier to replace components manually• Better for prototyping and modifications• Can be soldered with basic equipment• More suitable for field repairs |
Common Applications
Best Uses for SMT:
- Consumer electronics (smartphones, tablets, etc.)
- High-volume production runs
- Products requiring miniaturisation
- High-frequency or high-speed applications
- Lightweight devices
Best Uses for Through Hole:
- High-reliability applications (medical, aerospace, industrial)
- High-power or high-voltage circuits
- Products subject to mechanical stress or vibration
- Prototypes and low-volume production
- Products requiring field serviceability
Hybrid Approaches
Many modern PCBs use a hybrid approach that leverages the advantages of both technologies:
- Mixed Technology: Critical components that require mechanical strength use through-hole mounting, while smaller components use SMT for space efficiency.
- Selective Placement: High-power or high-stress components use through-hole, while signal processing and control circuitry use SMT.
- Design Optimisation: Through-hole components on one side with SMT on both sides, maximising the advantages of each technology.
Making the Right Choice for Your Project
When deciding between SMT and through-hole technology, consider:
- Environmental conditions – Will the product be exposed to extreme temperatures, vibration, or physical stress?
- Production volume – Higher volumes typically favour SMT for cost efficiency.
- Size constraints – Space-critical applications benefit from SMT’s smaller footprint.
- Electrical requirements – High-frequency applications often perform better with SMT, while high-power applications may require through-hole.
- Expected product lifecycle – Products requiring field service or long-term repairability might benefit from through-hole components in critical areas.
- Budget considerations – Initial prototyping budgets might favour through-hole, while high-volume production economics often favour SMT.
How ABL Circuits Can Help
At ABL Circuits, we specialise in both SMT and through-hole PCB assembly, offering:
- Expert guidance on technology selection for your specific application
- Mixed-technology assembly capabilities
- High-quality automated SMT placement and soldering
- Precision through-hole component insertion and soldering
- Rigorous testing and quality control for both technologies
- Flexible production volumes from prototypes to high-volume manufacturing
Our experienced team can help you navigate the decision-making process and implement the best solution for your specific requirements. Contact ABL Circuits today to discuss your project needs and discover how our expertise in both SMT and through-hole technology can benefit your next PCB design.
Call ABL Circuits on 01462 414336 or visit www.ablcircuits.co.uk to learn more about our PCB assembly services.
