PCBA is the English printed Circuit Board +assembly abbreviation, that is, in the PCB empty board first through the SMT (Surface Mount Technology) on the piece, and then through the dip (double row of direct-insert packaging technology) plug-in production process.
PCBA wiring layout also tends to be more sophisticated, PCBA which has a higher demand for production, in other words, the reliability of production has a greater demand, the production process of high reliability, the production of products will have higher reliability.
The manufacturability and reliability design of PCBA can improve the process level of circuit industrial design effectively. However, due to the lack of relatively mature theory on the manufacturability and reliability design of PCBA, there are some human and technical problems in the manufacturability and reliability design of PCBA. PCBA To analyze the cause of the problem, it is very important to put forward an effective improvement measure to realize PCBA manufacturability and reliability design.
1 The concept of PCBA
The so-called PCBA is printed circuit board is on the insulating substrate, according to the predetermined design, made of printed wiring, printed components or a combination of the two conductive graphics made of the board. As the support of the components and the electrical connection required for the system circuit work, PCBA it is an important basic component for miniaturization, lightweight, PCBA assembling mechanization and automation of electronic products, which is widely used in the electronics industry.
2 PCBA manufacturability and problems in reliability design
2.1 Drilling Problems
The factory carries on the hole processing, through the mechanical work, the engineering department provides each kind of parameter disposition, on a copper clad laminate, according to the engineering department provides the borehole parameter chart to carry on each kind of hole processing. In fact, on a PCBA board, the aperture is not exactly the same, because some holes are used as plated holes, PCBA and some holes do not need copper plating, which results in a different size of the aperture. At the same time, the hole on the PCBA board is a millimeter-level unit, which requires a high precision for the machine.
However, because the line is too dense, hole and hole distance between the reasons, the phenomenon of hole drilling has occurred frequently, and has been occupying the largest proportion of bad projects. As described in the previous design principle, the distance between the hole to the line and the distance between the hole and the hole has an optimal range of recommendations, which is worthy of the designer's attention and is considered in the usual design. PCBA At the same time, the size of the pad also has a certain impact on the problem, for example, the pad design is more lenient, then even if the hole is slightly biased, it does not affect the reliability of PCBA board. Of course, the design of the pad to take into account the overall layout of the panel, not because of this reason the wiring exceeds the allowable range of density, and caused another problem, so that the reliability of the PCBA board has caused the same or greater impact.
Immersion copper is a very important part of the PCBA process, in the PCBA production, double panel and multilayer Board is the most production of the plate type, and sinking copper this process is very important, he makes the different levels of the board connected together to form a whole, therefore, PCBA the success rate of immersion copper determines the output of PCBA board production level.
In the previous article has been introduced, immersion copper is mainly through chemical reaction to make the plate surface of copper foil thickening, so that the hole wall left a thin layer of copper, PCBA in order to facilitate the electroplating process behind. Due to the need for copper plating in the hole wall, it is decided that the actual aperture size is different from that of the design. and immersion copper is done by chemical reaction, PCBA we can only pass some parameters, for example, the problem, solution concentration, to control the degree of copper immersion and progress, so the accuracy of the grasp is not very accurate, this requires design, designers should fully consider the process objectively existing difficulties, to design PCBA wiring diagram, Thus, PCBA the reliability of the machined plate can reach the maximum possible range.
In addition, because the production of PCBA factory is large-scale, rather than individual, this determines the production process, PCBA the workers can not be every piece of production and processing of the PCBA to take care of, therefore, this is more required designers to fully consider the objective difficulties in processing.