Through-Hole PCB Assembly Services in UK & Europe

It might seem strange that in this era of miniaturization, Rush PCB UK is continuing with THCs or Through-Hole Components. THCs are considerably larger than their surface mount counterparts, making it nearly impossible to achieve the same component density. Moreover, they require a different PCB design with holes to anchor them in place. Therefore, using THCs may seem to go against the trend in electronics. However, there are many reasons why using THCs may be necessary, especially when integrated within a full turnkey PCB assembly solution for high-reliability applications.

1. Mechanical Strength and Durability:

Through-hole assembly requires component leads to be inserted into holes in the PCB before soldering. This means the components are held mechanically before soldering, providing a stronger bond than is possible with SMCs, which are anchored only by solder. This allows TH assembly boards to be more capable of withstanding physical stress, such as vibration and shock in severe environments. Withstanding physical stress is an essential and critical factor for PCB assemblies used in industrial, military, aerospace, and automotive environments. Through-hole technology is therefore suitable for applications where the PCB must withstand excessive stress and must also feature longevity and low maintenance.

2. Enhanced Heat Dissipation:

Being considerably larger than SMCs, THCs feature greater thermal mass per component. The presence of higher quantities of metal in the form of larger end caps and leads provides better thermal conductivity, resulting in better heat dissipation because of a larger surface area of the component and larger PCB layers.

3. Ease of Assembly:

Where SMCs require an automated machine to mount them in place, THCs are better suited for manual assembly. Therefore, THC PCB assembly is suitable for smaller production runs, as opposed to SMC technology, which is better suited for automated high-volume manufacturing. Manual assembly of THC PCBs is a versatile option for custom or unique configurations.

4. Range of Component Types:

You can select from a wide range of component types in THC assembly. The range covers large components for high power dissipation to small components for low power consumption. THCs include all types of ICs, capacitors, resistors, transformers, and other active and passive components.

5. Tolerance Factors:

With their larger bodies, THCs offer a greater room for manufacturing tolerances. Also, component leads inserted into PCB holes allow for a more lenient approach to assembly errors related to positioning and alignment.

6. Easier Inspection and Testing:

TH assemblies, with their larger spacing and visible leads, offer easier physical inspection and testing. In comparison to PCBs assembled with SMC, visual inspection and testing of TH assemblies are simpler and may not need AOI or X-ray machines.

7. Less Expensive:

For prototypes or small production lots, TH assemblies can be less expensive compared to their SM counterparts. Assembling SMCs requires expensive automated devices and machinery that are better suited for high-volume production. SMC technology becomes cost-effective only when the production is scaled up. On the other hand, TH technology does not rely on sophisticated machinery and is therefore more economical and practical for small and medium production runs.

8. Better Repairability and Longer Lifecycle:

The larger dimensions involved with THC result in better repairability without the need for sophisticated equipment. Moreover, THCs have a longer lifecycle due to their better heat dissipation capability and robust mechanical anchoring.

The difference between THC assembly and SMC assembly is best demonstrated in the following table:

How TH PCB Assembly Works?

The PCB assembly is a well-established process. Component leads are inserted into holes in the PCB before soldering. This process creates a reliable and durable connection resistant to mechanical stress. Creating a PCB suitable for THCs requires a few additional processes during fabrication:

1. Hole Drilling:

During fabrication, the PCB manufacturer must drill holes for the THCs. The location, spacing, and dimensions of these holes are precisely designed to enable them to match the size of the component leads to be inserted. The hole diameter must closely match the component lead for an effective mounting and a strong soldering process.

The holes serve a dual purpose—mechanical and electrical. Mechanically, the holes provide a precise location for the placement of a component. Electrically, the hole, along with a copper pad and a trace, provides an electrical pathway for interconnections.

2. Component Insertion:

Depending on the complexity and volume of the project, THCs may be inserted into their respective holes in two ways:

Manual Insertion: Skilled technicians form the leads of the components before inserting them into their respective holes. This is a flexible and precise operation, as humans can easily handle components of different sizes and shapes.

Automated Insertion: For larger production runs and boards with numerous components, insertion machines are often used by assemblers. Typically, two machines are necessary, one for forming the component leads by bending and trimming the leads to their proper dimensions, and preparing a suitable tape of components for the second machine, which handles the insertion.

3. Soldering:

Once the board has been populated by all the TH components, the leads are soldered to the board to establish a mechanical bonding and an electrical connection. The two primary methods of soldering THCs are:

Manual Soldering: For smaller batch numbers or prototypes, manual soldering is the preferred method. This involves using a hot iron tip to melt solder onto the lead and pad, thereby bonding them mechanically and electrically. The manual method sequentially soldered each joint.

Wave Soldering: This method is more useful for soldering large batches. Here, the assembled board with THCs passes over a wave of molten solder. Capillary action pulls the molten solder into the holes, thereby bonding the lead with the pad. As the wave soldering process creates many solder joints simultaneously, it is suitable for large batches of identical boards.