Want to do a good job of high-complex PCB and PCBA: First, do the DFM of these PCBs and PCBAs from the engineering design; Second, for these PCBs and PCBAs, you need to choose suppliers with particularly strong engineering capabilities.

DFM of high-complex PCB

We need to pay special attention to suppliers, materials, design, etc. when doing high-complexity PCB DFM. For example, in PCB design, the more layers, the layer alignment accuracy will decrease. Therefore, when considering the aperture Be especially careful with the distance from the hole to the line. Similarly, the hole width of the vias should also be increased, because the alignment is not accurate, and the disk may be broken when drilling. Therefore, when we design a board with a large number of layers, we must appropriately increase the diameter of the inner orifice disk. In addition, when considering the distance from the hole wall to the trace, we must pay special attention to the shrinkage of the high Tg board under thermal shock conditions.

When designing high-complexity PCBs, you must be careful about surface treatment. Judging from the situation we currently use, hot air leveling is not suitable for high-rise, large-size and high-complexity boards. For ENIG, due to some fine-pitch and dense-pitch devices on high-complexity boards, the size of the pads is very small, which will greatly increase the sensitivity to black disks. Therefore, we are basically on high-complexity boards. The use of ENIG surface treatment is prohibited. For OSP, it is necessary to consider its adaptability to ICT testing.

DFM of high-complex PCBA

For the DFM of PCBA, the process route of reflow soldering is preferred, and a small number of plug-ins, such as coaxial connectors, cable connectors, etc., consider the use of through-hole reflow soldering. When the number of plug-ins is large, the centralized layout should be considered, and the process route of reflow soldering plus partial wave soldering or selective wave soldering should be adopted to avoid manual repair soldering.

In addition, there must be corresponding requirements in various aspects such as the accuracy of graphics positioning, the impact of the diversity of device types on the assembly process and stencil design, and the assembly capabilities and maintenance of equipment.

High-complex PCBA assembly engineering capabilities of EMS manufacturers

For EMS manufacturers, the biggest problem we encounter is that EMS factories are not classified. From the perspective of personnel quality, equipment capabilities, and on-site process control capabilities, whether they are suitable for high-complexity boards, there is no clear positioning. We have also considered using different methods for different suppliers, such as the use of fixed-line methods to solve the problem. However, is there a clear requirement for the improvement of the entire EMS factory's capabilities and the improvement of personnel capabilities? Moreover, there is also a question whether the ability of the line you set can be quantified. For example, for a board with a complexity of more than 200, the corresponding relationship between the technical capabilities and equipment capabilities of the corresponding personnel is still unclear.

Highly complex PCBA assembly requirements

Whether it is an EMS factory providing assembly services or our own processing, for the control of high-complexity PCBA, it can be quantified into five aspects-personnel, equipment, materials, methods, and environment.

Personnel: Designate a special production line to process high-complexity boards, and formulate strict regulations and requirements for its equipment maintenance and operation personnel, including training, examination, and job standards, etc.

Equipment: There are strict control requirements for each equipment of each high-complexity product production line, including strict operation guidelines, inspection requirements and other detailed regulations.

Materials: Control and reduce tube-type materials; 0402, 0201 micro-devices should have good dimensional stability and welding end consistency; pay attention to check whether the PCB has obvious deformation; various types of device coatings and welding ends have basically the same requirements for welding temperature ; The size of the reflow soldering deformation of the large-size connector and module package should be within the allowable range and so on.

Method: For the control of the process regulations, we now have a more than 30-page control procedure for the assembly of high-complexity PCBA. Each step includes the replacement and addition of tin printing and tin paste, and the stencil before loading the board. There are strict control requirements for the inspection before going on the machine, as well as the net paper, washing water, etc.

Environment: Strict control should be carried out in all aspects of material storage environmental conditions, anti-static management, moisture-sensitive device management, storage and turnover of IC devices.

The application value of PCB and PCBA complex quantification methods

EMS manufacturers adopt different strategies in personnel composition, equipment configuration, and process control for PCBAs of different complexity to form layered processing capabilities to meet different customer needs; different processing costs can be required according to different PCBA complexity.

Through the operation of high-complex PCB and PCBA, ODM manufacturers' PCB production yield and PCBA assembly quality have been significantly improved, reducing the cost and reliability risks of rework, and achieving good economic benefits. It can also be used to evaluate personnel input and process design strategies. , Management model optimization.

At present, the quantitative standards of PCB and PCBA are applied by a few companies, but they have not been widely recognized and applied by the industry; and the projects involved in the quantitative standards are not yet complete and need to be further optimized. The industry peers are required to participate together to form a unified The quantitative standards of PCB and PCBA are implemented in the industry.