SMD Boards

Through Hole vs SMD Boards: Choosing the Right PCB Technology

All electronic equipment requires a printed circuit board to hold its electronic components in place. This board serves a dual purpose. Apart from providing a mechanical anchoring place for electronic components, the board also provides electrical connections to the components. This allows the components to interact with each other and function to let the electronic equipment perform as intended.

Types of Boards

OEMs use two typical boards for their equipment. One of the types uses through-hole components, while the other uses surface mount components. Rush PCB Ltd makes both types of boards of the highest quality.

Through Hole Boards

The use of through-hole components started earlier, and these components had long leads. Boards using these components must necessarily have multiple holes through which the leads pass for soldering on the other side.

If the boards are double-sided or multilayered, the holes are typically plated through. That means an electroplating process creates a thin barrel of copper on the wall of the hole. Additionally, the hole has two pads on the top and bottom surface to which the copper barrel connects. This creates an electrical connection from one side of the board to the other. When an operator passes a component lead through the hole and solders it, the solder wicks into the hole and anchors the component firmly.

Advantages of Through Hole Boards

Printed circuit boards using through-hole components have several advantages:

  • Easy to Assemble—As through-hole components are larger, it is easy to handle them manually. Thus, it is also easy to manually insert and assemble them on the board.
  • Easy to Repair—it is easy to solder and desolder boards with through-hole components.
  • Easy to Troubleshoot—It is easy to troubleshoot malfunctioning or non-functioning boards with through-hole components.

Disadvantage of through-hole Boards

  • Mechanically Weak—The presence of large numbers of holes makes a through-hole board much weaker.
  • Low Component Density— The larger size of through-hole components does not allow placing many of them on a unit area of the board.
  • Low Routing Density—For multilayer boards, the size increases as the presence of a larger number of holes reduces the routing density of copper traces.
  • Large Equipment Size—With low component density, the overall equipment size must also be large.

SMD Boards

SMD Boards

To reduce the size of electronic equipment, it is also necessary to reduce the size of their printed circuit boards. For this, OEMs tended to move to smaller electronic components such as SMD or Surface Mount Devices. In place of long leads, SMDs use small end caps, and therefore, SMD boards do not require through holes.

The printed circuit on SMD boards has pads matching the SMD footprints. Assembly of SMD boards requires placing small amounts of solder paste on the pads, followed by the SMD. Once the board passes through a reflow oven, the solder melts and anchors the components to the board.

Advantages of SMD Boards

SMD boards offer several advantages over through-hole boards. These are:

  • High Component Density—With SMDs being much smaller, and having no leads, it is easier to achieve a high component density. Many SMD ICs have pins on all four sides to offer high functionality in small sizes.
  • High Routing Density—The absence of through holes allows multi-layered boards to achieve high routing density. This helps to reduce the size of the board significantly.
  • Higher Mechanical Strength—The absence of through holes allows the SMD board to retain its mechanical strength. This allows it to withstand higher stress and vibrations without damage. As a consequence, the reliability of the equipment improves.
  • Smaller Equipment Size—With higher component density and smaller PCB size, SMD boards significantly reduce the form factor of electronic equipment.
  • Higher Functionality—With smaller components, designers can provide electronic equipment with higher functionality.

Disadvantages of SMD boards

Although SMD boards have many advantages, they also have some disadvantages:

  • Require Automated Assembly—Manual handling of very small SMDs is difficult and requires automated machines for placement and soldering during assembly.
  • Require Automated Inspection—Many SMDs have pins on the underside of their packages. Once soldered, the solder joints are neither visible nor accessible. Inspecting them requires automated machinery.
  • Difficult to Repair—Closely packed SMDs present a formidable challenge for troubleshooting and repair.

Conclusion

Although Rush PCB Ltd makes both through-hole boards and SMD boards, the popularity of the latter is significantly higher among customers. We have many varieties of SMD boards, including rigid, flexible, and rigid-flex types. Contact us for any type of board you require for your project.