SMT, SMD, THT — The acronyms used in our industry can make PCB assembly sound a lot more complicated than it needs to be. However, knowing the difference between these common terms can help you decide on which SMT machines you need for a cost-effective, efficient assembly line.

What Is THT?

THT or through-hole technology is the oldest of the three terms. As the name implies, through-hole technology involves drilling holes in PCBs, then placing the leads of your components through these holes. Solder is usually placed between the component and the board and on the back of the board at the leads.

The extra strength this provides is important, especially when dealing with a connector, like an HDMI or USB port.


  • Creates Strong Bonds
  • Great For Connectors
  • Popular For Prototyping


  • Drilling Increases Production Costs
  • Slower Than SMT
  • Components Take Up More Space

What Is SMT?

As our devices have become smaller and more advanced, surface mount technology (SMT) has been replaced or been combined with THT for most applications. In SMT, a pick and place machine places your components (SMD's), and then the boards are sent through a reflow oven to bond the SMD's to each board.


  • Compatible With A Wider Range Of Components
  • Compatible With Compact, Lightweight PCBs
  • Can Place A Higher Density Of Components
  • SMD's Can Go On Both Sides Of The Board
  • Pick & Place Machines Place 1000s Of Components Per Hour
  • Better For Components Exposed To Vibration
  • No Drilling Required


  • Smaller Leads Are More Difficult To Repair
  • Not Ideal For High-Temperature Applications
  • SMT Machines Cost More Upfront
  • Fewer Solder Points Can Mean Weaker Joints

SMD Vs. THT Components

Unlike SMT and THT, SMD is not a process for attaching components to a printed circuit board. SMD stands for surface mount device. Capacitors, chip resistors, diodes, and transistors are all examples of the electrical components attached to a PCB through SMT — the SMD's.

THT components are different from SMD's in that they are often larger and attached through the THT process. So, they have long metal leads to use during that type of PCB assembly.

Used SMT Equipment For Sale

Whether you're in the market for THT machines or SMT machines used to place SMD's, we can help you save money. At Capital Equipment Exchange, we offer quality used screen printers, wave solder machines, reflow ovens, pick and place machines, ICT, and AOI testing equipment for PCB assembly. Check out our inventory and give us a call to place your order today.