Mixed Technology PCB Assembly

Imagine holding a sleek, compact electronic device in your hand, marveling at its high performance and reliability. Have you ever wondered what goes into making such a device? One of the key elements that contribute to the success of electronic devices is the printed circuit board (PCB). PCBs serve as the foundation on which electronic components are mounted, and play a critical role in determining the performance, reliability, and manufacturability of the final product. An increasingly popular approach to assembling PCBs is through mixed assembly, which combines both surface mount technology (SMT) and through-hole technology (THT). In this article, FS Technology will explore the advantages and disadvantages of mixed PCB assembly and how it can contribute to the creation of high-performance and cost-effective electronic devices. So, get ready to dive into the world of PCB assembly!

Types of PCBA Service

To ensure optimal performance from a PCBA board, a high-quality fabrication process and assembly method are crucial. Depending on the complexity of the circuit and the electronic parts involved in the design, a specific assembly type can be selected for the PCBA production process. At FS Technology, we offer the following PCB assembly methods:

THT PCBA Service
SMT PCBA Service
Mixed Technology PCBA Services

Through Hole Assembly (THT)

During through-hole assembly, DIP components are carefully inserted into pre-drilled holes on the PCB and soldered to the pads using molten solder. This can be done either through manual soldering or wave-soldering methods. The process involves three critical steps:

Firstly, technicians must precisely place the components in their designated positions according to the design files to ensure optimal performance. Following regulatory standards for through-hole mounting is recommended.

Secondly, automatic inspection techniques are utilized to verify the accuracy of the PCB component orientation against a standard reference board. If any errors are detected during this step, necessary corrections will be made before proceeding to the next step.

Lastly, components can be soldered to the board using manual soldering or wave soldering. Manual soldering is suitable for simple circuits or personal projects, while wave soldering is an automated process typically used in commercial high volume PCB assembly. In wave soldering, the PCBA board with DIP components in place and inspected is passed through an oven on a conveyor belt. Molten solder is applied to the PCB components at high temperatures from the bottom surface of the board.

Surface Mount Assembly (SMT)

Surface Mount Technology is a highly efficient and fully automated assembly method used to mount smaller surface-mount components. Compared to the Through-Hole Technology method, SMT assembly requires less time and is highly cost-effective. The SMT assembly process includes three steps.

The first step involves the application of solder paste. A stainless-steel stencil is used to apply the solder paste uniformly on the pads. The solder-paste squeezer can be configured to apply the appropriate amount of solder paste. The PCB is then inspected for uniform solder-paste application before moving to the next step.

In the second step, an automated pick-and-place machine is used to place the surface-mount parts on the PCB. The x-y coordinates of all components are fed to the automated machine, which accurately places the surface-mount parts in the position where solder pastes are already applied.

The final step involves passing the PCBA board through a long furnace at approximately 260°C to undergo reflow soldering. The high temperature melts the applied solder paste, creating a permanent connection between the SMD parts and the PCBA.

Mixed Assembly

Mixed/hybrid assembly is an assembly technique that requires both SMD and DIP components on one board. In this process, PCBA manufacturers mount smaller and more compact SMD components directly onto the surface of the board through a mounter. Once the SMT assembly process is completed, the PCBA board is then transferred to the through-hole assembly workshop, where the leads of the DIP components are passed through the holes in the PCB and soldered to the other side using either manual or automated machines. It should be noted that in mixed assembly, advanced patch assembly is usually used for plug-in assembly.

Mixed technology PCB Assembly can be a more cost-effective and efficient method of assembling electronic products because it allows for the use of different components, depending on their size, complexity, and functionality. For example, SMT can be used for smaller, more complex components that require high-speed signal processing, while THT can be used for larger, more robust components that require higher current capacity or mechanical strength.

Compared to pure SMT or THT assembly services, hybrid PCB assembly services require PCBA manufacturers to prepare a different set of tools and equipment. Both placement and insertion of components require dedicated machines. Additionally, the soldering process must be carefully controlled to ensure that both types of components are securely attached to the PCBA board.

One potential challenge of mixed technology PCB assembly is the need for more complex quality control and inspection procedures. Since two different types of components are being used, there is a greater risk of defects or errors during assembly. To reduce this risk, operators must carefully inspect and test the PCB to ensure that all components are properly installed and functioning correctly.

Features of PCB Hybrid Assembly

Advantages

Improved functionality: A PCBA board comprises two parts, bare board and components, and the main function of the bare board is to establish electrical connections between components. Hybrid PCBA technology allows a variety of components, including small IC chips for high-speed signal processing and capacitors, to be integrated onto the board. By assembling components with different functions, the final product can perform better and be more reliable.
Reduced size: Many electronic applications require small size, technological sophistication, or size reduction. The size of the shell is determined by the complexity of the internal structure. Hybrid assembly is a flexible option for medical PCB or portable electronics, as it allows components to be assembled without wasting space.
Cost-effectiveness: Hybrid PCBA technology combines two assembly methods (SMT and THT), allowing designers to use a wider range of components without limitation. Designers can choose the most suitable components based on the specific application, and there are more alternatives available when facing cost issues, resulting in cost savings in the manufacturing process and the final product.
Improved manufacturability: Mixing components improves the manufacturability of electronic products. Manufacturers can leverage the strengths of each assembly technology to optimize the manufacturing process. For example, during mass assembly, the automated SMT process can accelerate the assembly speed, while manual insertion can reduce the risk of expensive component failure.
Compatibility with legacy components: Many older electronic components are designed for THT assembly, but hybrid assembly allows them to be used with more advanced SMT assembly. Compatibility is especially important for manufacturers who need to keep up with older products or components. FS Technology’s hybrid assembly service makes this possible.

Disadvantages

Complexity: Hybrid PCB assembly is a more complex method that requires careful consideration of factors such as component compatibility, assembly, and soldering. The complex process flow can increase the risk of errors and defects during manufacturing, leading to a negative impact on product quality and speed to market.
Assembly time: Complex applications require multiple assembly methods, and the use of hybrid assembly with both SMT and THT processes can add to the overall assembly time. As SMT processes are typically faster than THT processes, adding DIP components may not be conducive to fast turnaround PCB assembly, resulting in longer lead times for the final product.
Component availability: Due to the increasing use of SMD components in electronic applications, the procurement of DIP components for mixed assembly may face some difficulties in maintaining a supply and demand balance. This may require the procurement of dedicated components from multiple suppliers.
Manufacturing cost: Requires two types of assembly equipment, which can increase capital investment and ultimately lead to increased manufacturing costs. These costs are often passed on to customers, impacting the overall cost-effectiveness of the final product.
Soldering issues: Soldering DIP components is more challenging and this can increase the risk of soldering defects, such as cold joints or insufficient solder. These defects can negatively impact product quality and reliability.

FS Technology's Mixed PCB Assembly Services

In the above discussion, we have explored the advantages and characteristics of different PCB assembly methods. In Mixed assembly technology, we have observed that it can be complex, demanding, and lead to longer assembly times. However, in today’s electronic application environment, we must face these challenges. Therefore, it is important to choose a reliable PCBA manufacturer to handle these complexities. FS Technology offers several advantages:

Seven SMT assembly/DIP assembly lines for rapid assembly.
Strong component procurement capabilities to avoid component compatibility issues.
A robust design team that optimizes your design schemes.
Perfect value-added services to improve project revenue.
Advanced assembly equipment to ensure project quality.