PCB multilayer blind hole resin plug hole technology

With the development of electronic products in the direction of diversification, high precision and high density, the same requirements are put forward for circuit boards. The most effective way to increase the pcb density is to reduce the number of through holes to achieve precise placement of blind and buried vias.

1.Advantages of multilayer blind via circuit boards:

●Eliminate a large number of through-hole designs, improve wiring density, and effectively save horizontal space.

●The design of the internal interconnection structure is diversified

●The reliability and electrical performance of electronic products are significantly improved.

2. The role of blind hole plate:

The production of blind via boards makes the circuit board production process three-dimensional, effectively saves the horizontal space, adapts to the high density of modern circuit boards, the technological update of interconnected electronic products, and the structure and installation methods of electronic chips are also constantly improving and changing. . Its development is basically from components with plug-in feet to highly dense integrated circuit modules with ball-shaped matrix arrangement of solder joints.

3.Problems faced by conventional HDI laser blind via process:

There are voids in the blind vias, and air remains in them, which affects reliability after thermal shock. The conventional method to solve this problem is to fill the blind hole with resin or fill the blind hole with resin plug by pressing the plate. However, the reliability of the PCB boards produced by these two methods is difficult to guarantee and the production efficiency is low. In order to improve the process capability and improve the HDI process, the process of filling blind holes by electroplating is adopted. The advantage is that the blind holes can be filled with electroplated copper, which greatly improves the reliability. Blind holes are superimposed on the graphics, which greatly improves the process capability to adapt to the increasingly complex and flexible designs of customers.

The ability of electroplating to fill blind holes is affected by the material of the PCB board and the hole type of the blind holes. In order to achieve a good effect of filling blind holes and the surface copper thickness is up to standard, advanced equipment, special copper plating solution and copper plating must be used. Additives, these are also the focus and difficulty of this technology.

4.Resin plug hole

Resin plug hole background:

The technology of resin plug hole is more and more widely used in PCB, especially in high-layer, high-precision PCB multi-layer circuit board. Use resin plug holes to solve a series of problems that cannot be solved by using green oil plug holes or press-fit resin. Because of the characteristics of the resin used in this circuit board process, there are many difficulties in circuit board fabrication.

5. Definition

The resin plug hole process refers to the use of resin to plug the buried holes in the inner layer, and then press-fit, which is widely used in high-frequency boards and HDI boards; it is divided into traditional silk screen resin plug holes and vacuum resin plug holes. The general product manufacturing process is the traditional silk-screen resin plug hole, which is also the most common process method in the industry.

6.control difficulty

Common quality problems of resin plug holes and their improvement methods

⑴ Common problems

A, orifice bubble

B. The plug hole is not full

C, resin and copper layering

⑵ Consequences

A. There is no way to make a pad on the orifice; the orifice hides the air, and the chip mounts and blows.

B. There is no copper in the hole

C. The pads are protruding, causing the components to not be attached or the components to fall off

⑶ Prevention and improvement measures

A. Select the appropriate plugging ink, and control the storage conditions and shelf life of the ink.

B. Standardized inspection process to avoid holes in the orifice. Relying on excellent plug hole technology and good screen printing conditions to improve the yield rate of plug holes.

C. Select the appropriate resin, especially the selection of material Tg and expansion coefficient, appropriate production process and degumming parameters, so as to avoid the problem of detachment of the pad and the resin after heating.

D. For the problem of resin and copper delamination, when the thickness of copper on the hole surface is greater than 15um, the problem of such resin and copper delamination can be greatly improved.

7.Inner HDI buried hole, blind hole resin plug hole

⑴Common problems

A. Explosion board

B. Blind hole resin protrusion

C. hole without copper

⑵ Consequences

The above problems directly lead to the scrapping of the product. The protrusions of the resin often cause unevenness in the lines, resulting in open and short circuits.

⑶ Prevention and improvement measures

A. Controlling the fullness of the inner HDI plug hole is a necessary condition to prevent the board from bursting; if the plug hole is selected after the line is selected, the time between the plug hole and the pressing and the cleanliness of the board surface should be controlled.

B. The resin protrusion control needs to control the grinding and flattening of the resin, and grind the boards horizontally and vertically to ensure that the resin on the board surface is clean. If the parts are not clean, the resin can be repaired by hand grinding; the resin concave after grinding the board should not be larger than 0.075mm mm. Electroplating requirements: According to the customer's copper thickness requirements, electroplating is carried out. After electroplating, slicing is performed to confirm the concave degree of the resin plug hole.

8. in conclusion

After years of development, the technology of blind hole + resin plug hole continues to play an indispensable role in some high-end products. Especially in blind buried vias, HDI, thick copper and other products have been widely used, these products involve communications, military, aviation, power, network and other industries. As a manufacturer of PCB products, we know the process characteristics and application methods of resin plug holes. We also need to continuously improve the process capabilities of resin plug hole products, improve product quality, solve related process problems of such products, and achieve higher Manufacturer of technically difficult PCB products.

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