The increasing importance of laminating and laminating technology in all of these industries, including PCB, is increasing rapidly.
In order to prevent quality problems, such as dislocation, during lamination, it is usually required to integrate PCB manufacturing processes before lamination. Compared with traditional fusion technology, modern fusion technology has the advantages of high efficiency, easy operation and low cost, which makes it easy to make multilayer PCB. Based on the basic technology of the fusion PCB manufacturing, this paper discusses the parameter factors that affect the fusion effect and the application level of the fusion technology, so as to provide a reliable reference for obtaining the best fusion parameters.
Principle fusion technology
As a traditional technology, rivet technology has been widely used in PCB manufacturing. However, the rivet technology also has some disadvantages, such as the high cost of rivets, the dislocation caused by the deformation of PCB, the easy damage of the template, the indentation of the rivet shape on the circuit board, etc., and the high cost of PCB. Therefore, fusion technology has been continuously used to replace rivet technology.
Brief introduction of PCB rivet technology
According to the melting characteristics of epoxy resin prepreg, the melting technology can make the prepreg melt at a certain temperature, so as to convert B-phase epoxy resin into C-phase epoxy resin, and the inner layers are connected by adhesive. Fusion lamination is one of the most important processes, and its performance directly determines the lamination behavior. The key elements of convergence technology include:
Accuracy of positioning system
The type of positioning system is directly related to the alignment accuracy between inner layers, which further affects the percentage of pass rate. An excellent positioning system should be stable, reliable and repeatable.
Fusion point design
Point fusion is an essential problem, because fusion technology involves many shapes, such as square, circle and ellipse. Fusion points should be consistent in area, because fusion points with too small area tend to lead to less firm fusion welding, while fusion points with too large area tend to lead to image penetration, which may lead to white spots, loose connection between inner layers or
Equipment flatness
The flatness of the equipment will affect the angle of PCB in the fusion process, the force distribution and time balance in the fusion process. Non-uniformity will lead to the deformation of the circuit board, which will further lead to interlayer dislocation.
And temperature and time control.
During the implementation of fusion technology, the temperature and time should be carefully controlled to avoid burning, white spots, desoldering and aging. In addition, the lamination of PCB plays an important role in determining the fusion effect.
Factors affecting the fusion performance in the manufacturing of FusionPCB
Welding joint
Different fusion and fusion effects are summarized in the following table, which is suitable for different types of fusion welded joints.
The welding head shape is between L1/2 and PP, between L3/4 and PP, and between L5/6 and PP.
Circle6.194.515.995.62
5.814.826.07
6.065.385.77
Rectangle9.777.899.468.71
9.906.789.58
8.756.949.32
Based on the above table, because the area of rectangular fusion welded joints is three times larger than that of circular fusion welded joints, the bonding produced by rectangular fusion welded joints is obviously larger than that produced by circular fusion welded joints. However, the resin flow produced by rectangular fusion welding joint is much larger than that produced by circular fusion welding joint. When the resin flow rate is too large, part of the board side may be higher than the board side, which may lead to false pressure on the board side. For small-sized PCB products, the melting point that can be designed is very limited, and the area of circular welding joint is small, so the welding effect is insufficient. Therefore, the rectangular welding joint should be selected, and the welding position should be carefully designed. As the plate moves inward, the defect of resin overcurrent can be eliminated.
Melting temperature
When the melting temperature reaches, the melting point is 300°C, and the fusion expansion area is large, which seriously affects the polymerization effect. When the melting temperature reaches 270℃, the fusion expansion area is uneven, and the risk of cracking is high, resulting in fusion effect. When the melting temperature reaches 285℃, the fusion expands evenly and there is no risk of cracking, which leads to the best fusion effect. Therefore, it can be concluded that at the same melting time and lamination, 285°C is the best melting temperature for multilayer PCB manufacturing.
Melting time
At the equivalent melting temperature and lamination, different fusion time will affect the fusion expansion area and fusion effect. When the melting time is 12 seconds, the fusion expansion area is uneven, which has the risk of cracking and bad fusion effect. When the fusion time is 18 seconds, the fusion expansion area is large and the fusion effect is poor. When the fusion time is 15 seconds, the fusion expansion is uniform, and there is no crack risk and the best fusion effect. Therefore, at the equivalent melting temperature and equivalent layer stacking, 15 seconds is the best fusion time for multilayer PCB manufacturing. Too long or too short fusion time will bring bad fusion effect.
overlap
Equivalent fusion temperature and fusion time, different layers determine the fusion area and fusion effect. Under the equivalent melting time and melting temperature, when prepreg 2116 is applied, there is even no crack in the fusion expansion area, resulting in the best fusion effect. Under the equivalent melting time and melting temperature, when the prepreg 7628 is applied, the fusion expansion area even has cracks. This shows that at the same melting time and melting temperature, the thinner the prepreg, the better the fusion effect will be. Therefore, it can be concluded that the lamination of 2116 prepreg or lower layer is suitable for the realization of melting technology in the manufacturing process of multilayer PCB.
According to the discussion in this paper, there are many factors that affect the fusion effect: the shape of fusion joint, melting temperature, fusion time and lamination. Rectangular fusion welding joint has better fusion effect than circular fusion welding joint. When equivalent layers are stacked and fused, the higher the fusion temperature, the larger the fusion expansion area. If the melting temperature is too low, the fusion expansion area will be uneven, and there is a risk of cracking. The longer the fusion time, the larger the fusion expansion area. When the fusion time exceeds 15 seconds, the fusion expansion area will expand, resulting in bad fusion effect. The thinner the prepreg structure, the more uniform the melt expansion. Therefore, prepreg of 2116 or lower is the most suitable for fusion.
