6 key points of quality control during PCB process

PCB process involves a series of processes such as PCB board manufacturing, component procurement and inspection of pcba incoming materials, SMT processing, DIP plug-in processing, program burning, testing, aging, etc. The supply chain and manufacturing chain are pretty long, and any defect in the link will lead to quality of the PCBA board is not qualified, which has serious consequences. Therefore, the control of the entire pcba SMT processing is particularly important. This article mainly analyzes from the following aspects.

1. PCB circuit board manufacturing

It is especially important to hold a pre-production meeting after receiving an order for PCBA processing. The main purpose is to analyze the craft of PCB Gerber files and submit a manufacturability report (DFM) according to different customer needs. Many small manufacturers do not pay much attention to this, but mostly tend to herein. Not only is it easy to produce poor quality problems but also a lot of rework and repair work caused by bad PCB design.

2. PCBA incoming components procurement and inspection

It is necessary to strictly control the procurement channels of components, and must obtain goods from large traders and original manufacturers, so as to avoid the use of second-hand materials and counterfeit materials. In addition, special PCBA incoming inspection positions are required, and the following items are strictly checked to ensure that components are not faulty.

PCB: Check the reflow oven temperature test, whether the fly-free via is plugging or leaking, whether the board is bent or not.

IC: Check that the screen printing is exactly the same as the BOM and store it at constant temperature and humidity.

Other commonly used materials: check screen printing, appearance, power measurement value, etc.

3.SMT assembly

Solder paste printing and reflow oven temperature control systems are key points of assembly and require the usage of laser stencils that are more demanding in quality and more responsive to processing requirements. According to the requirements of the PCB, some of the steel mesh holes or U-shaped holes need to be added or reduced, and only the steel mesh can be made according to the craft requirements. The temperature control of the reflow oven is critical to the wetting of the solder paste and the firm welding of the stencil and can be adjusted according to the normal SOP operating guidelines.

In addition, strict implementation of AOI testing can greatly reduce the defects caused by human factors.

4.DIP plug-in processing

In the plug-in process, the mold design for wave soldering is the key. How to use the mold to greatly improve the yield rate is a process that PE engineers must continue to practice and summarize.

5.Program burning

In the previous DFM report, the customer may be advised to set some test points on the PCB (test point) in order to test the circuit continuity in the PCBA processing after all components of the PCB are welded. If conditions permit, the customer can be required to provide a program to burn the program into the master control IC through the programmer, which can more intuitively test various touch actions to verify the integrity of the entire PCBA function.

6.PCBA processing board test

For orders with PCBA test requirements, the main test content includes ICT (circuit test), FCT (function test), burn test (aging test), temperature and humidity test, drop test and so on.

The knowledge of PCBA processing and PCBA incoming material is much more than that. Each of the above points can be elaborated with long article. This article only expounds the empirical control key points of pcba SMT processing board from a macro perspective, hoping to be helpful to practitioners.