PCB Plug hole processing technology

- Jul 26, 2018-

In the era of HDI high-density connection technology, the trend of line width and line spacing will inevitably become smaller and denser. As a result, different types of PCB structures emerge, such as Via on Pad, Stack Via, etc. Under this premise, embedded holes in the inner layer are usually required to be fully filled and ground flat to increase the wiring area of the outer layer.The market demand not only tests the PCB's manufacturing process capability, but also forces the original material suppliers to develop more hi-tg, Low CTE, Low water absorption rate, solvent-free, Low shrinkage rate, easy grinding and other characteristics of plug ink to meet the needs of the industry.The main processes of the plug section are drilling, electroplating, roughening of the hole wall (pre-treatment of the plug hole), plugging hole, baking, grinding, etc.The manufacturing process of resin plug hole is introduced in detail.
At the same time, all Via holes should be filled with ink or resin for the outer circuit due to the need of encapsulation, so as to prevent the tin in the hole from causing other functional hazards.
Current plugging methods and capabilities
The current plugging methods generally adopt the following techniques:
1. Resin filling (mostly used for inner hole plug or HDI/BGA packaging plate)
2. Printing surface ink after hole drying
3. Use blank network plug and seal
4. Plug the hole after HAL
Analysis on the technology of three-plug hole and its advantages and disadvantages
The screen printing plug hole is a kind of plug hole operation commonly used in the industry at present, because the main equipment printing machine platform it needs is widely owned by various enterprises.And necessary tools such as: printing plate, registration Pin under the screen, scraper, and so on also is almost everywhere in the regular material, its process is not a very difficult operation, with a single stroke of the scraper printing in consistent with the inner plug hole aperture location on the screen, by printing pressure will ink into aperture, at the same time to make the ink smoothly into hole inner lining plug hole plate below, need to prepare a plate under for plug hole aperture breathable, make the hole in the process of plug hole smooth discharge of the air inside, and the effect of 100% full.Even if to conform to the requirements of the plug hole quality, the key lies in optimizing the parameters of the operations, which contains the screen mesh, tension, scraper hardness, Angle, speed, etc all can affect the quality of plug hole, and different plug hole aperture aspect ratio have different parameters, has the experience of workers required to get the best operation conditions.
Advantages disadvantages
The printing machine is widely used, which can be used in welding resistance, word printing and other processes
As a general plugging method, the process arrangement is relatively easy to complicate and complicated operation parameters
The hole diameter without plug hole can be set on the screen plate to avoid poor ink production efficiency
No need to purchase additional plug hole equipment, suitable for the industry existing production process each type of plug hole plate needs to be made in addition to the corresponding network plate
The advantages and disadvantages of various drilling techniques are as follows:
 The method of hole plugging is to plug the hole first and then print the ink on the board
Efficiency is faster, slower and slower
The volume control of plug hole is easy, difficult and easy
Plug holes often run into problems
Foaming/cavitation is more likely to exist than not
The tin bead is easy to exist (with insufficient plug hole) and will not appear (except for tin spraying).
There is no bomb oil
The existence of blasting hole will not exist
The transmission crack will not be easy (the amount of hole plug is insufficient) and will not be easy (the amount of hole plug is insufficient).
The heavy industry can do it or not.