Through hole and SMD board: Choose the right PCB technology

All electronic devices require printed circuit boards to hold their electronic components in place. The board has a dual purpose. In addition to providing a mechanical anchoring place for electronic components, the board also provides an electrical connection to the components. This allows components to interact and function with each other, making the electronics function as intended.

Type of board

Original equipment manufacturers use two typical boards for their equipment. One type uses through-hole elements, while the other uses surface-mount elements. Rush PCB Ltd produces two types of the highest quality circuit boards.

Through-hole plate

The use of through-hole elements, which have long leads, began earlier. The board using these components must have multiple holes through which the leads are welded on the other side.

If the plate is double-sided or multilayered, the holes are usually plated. This means that the plating process creates a thin copper barrel on the wall of the hole. In addition, the top and bottom of the hole have two pads to which the copper cylinder is attached. This creates an electrical connection from one side of the board to the other. When the operator passes the component lead through the hole and welds, the solder is sucked into the hole and firmly holds the component in place.

Advantages of through-hole plates

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

Easy to assemble - Easy to handle manually due to the large through-hole components. Therefore, it is also easy to insert and assemble them manually on the circuit board.

Easy servicing - Solder and de-solder the circuit board using through-hole components.

Easy Troubleshooting - Troubleshooting a faulty or non-functioning board is easy with a through-hole assembly.

The shortcomings of the through hole plate

Mechanical weakness - The presence of a large number of holes makes the through hole plate weaker.

Low component density - The size of the through-hole components is large and does not allow many components to be placed on the unit area of the board.

Low wiring density - For multilayer boards, as the number of holes increases, the wiring density of copper wires decreases and the size increases.

Large device size - When component density is low, the overall device size must also be large.

SMD board

In order to reduce the size of the electronic device, it is also necessary to reduce the size of its printed circuit board. For this purpose, Oems tend to turn to smaller electronic components, such as SMDS or surface mount devices. SMDS use small end caps instead of long leads, so SMD boards do not require through-holes.

The printed circuit on the SMD board has a pad that matches the SMD package. The assembly of the SMD board requires placing a small amount of solder paste on the pad and then SMD. Once the board passes through the reflow furnace, the solder melts and secures the components to the board.

Advantages of SMD board

Compared with through hole plates, SMD plates have several advantages. These are:

High component density - SMDS are much smaller and have no leads, making it easier to achieve high component density. Many SMD ics have pins on all four sides to provide high functionality in a small size.

High wiring density - Without through-holes, multi-layer boards can achieve high wiring density. This helps to significantly reduce the size of the board.

Higher mechanical strength - The absence of through-holes allows SMD boards to maintain their mechanical strength. This allows it to withstand higher stresses and vibrations without damage. As a result, the reliability of the equipment is improved.

Smaller device size - SMD boards feature higher component density and smaller PCB sizes, significantly reducing the form factor of electronic devices.

Higher functionality - Using smaller components, designers can provide higher functionality for electronic devices.

Disadvantages of SMD board

While SMD boards have many advantages, there are also some disadvantages:

Automatic assembly required - Handling very small SMDS manually is difficult and requires automated machines to mount and weld during assembly.

Automatic detection is required - many SMDS have pins on the bottom of the package. After welding, the solder joint is neither visible nor easily accessible. Checking them requires automated machinery.

Difficult to repair - Tightly packed SMDS present a huge challenge for troubleshooting and servicing.