PCB Tech - Processing details of high-precision multilayer boards

The core of high-precision multilayer circuit boards is the pressing process between multilayer boards. Because customers have not been engaged in the PCB production industry, they usually lack understanding of the pressing process and are not very familiar with the production process and production standards of various manufacturers. This led to quality control problems such as obvious delamination, warping, and even disconnection of the inner layer after getting the multi-layer board. Old Chen will reveal the secret to everyone today. The main reason for this quality control problem is that the factory’s production line is not complete. The pressing process can only be sent out to amateur pressing factories. Many foundries have many defects in process, equipment, and talents, resulting in pressing. The quality is unreliable. Common problems include:

.The foundry is not equipped with hot melt machine and X-RAY drilling target machine, but only through the riveting process, the tolerance of the rivet hole will affect the alignment accuracy between the multi-layer plates, and the impact of the pressing machine during the pressing will cause The rivet is deformed, causing the deflection between layers

(The solution is to increase the distance between the hole and the line to reduce the scrap rate of high-precision boards, but this also limits the customer's PCB design)

.The equipment of the foundry pressing machine is old, the failure rate is high, and the frequent shutdown events cause low production efficiency and fail to deliver on time, which affects the delivery time.

However, the hardship behind the introduction of a press production line is not simple. The factory needs to comprehensively consider equipment accuracy, cost reliability and other aspects. It also needs specialized personnel to operate it. The high cost has caused many manufacturers to stay away. Zhuolu Electronics also tried outsourcing in the early stage of its start. Due to the shortage of funds, this is not ashamed. But after a period of trial, it was found that the quality and efficiency of OEM production could not keep up with our development, so we stopped decisively and started to fully assemble our own pressing line.

We have invested in the introduction of pressing machines (2 vacuum hot presses, 1 cold press) manufactured by "MEIKI" and other supporting equipment to form the pressing line stage of the production line for high precision at this stage 4-12 layer PCB pressing. The reason why we choose a famous machine mainly considers these two reasons:

(1) Rich manufacturing experience:

MEIKI (MEIKI) is one of Japan's professional manufacturers of laminating machines and laminating machines. It was founded in 1933. It still has deep manufacturing experience and core technology in the field of laminating machines. Verification and recognition by a large number of large PCB companies in Europe and the United States (MEIKI developed Japan's first heat press for plywood as early as 1942, and developed a vacuum press for multilayer printed circuit boards in 1985)

(2) High reliability & high stability:

The famous machine has a precision program of a specially tuned dedicated controller (VISTAC-2C), which can accurately control the heating and cooling thermal cycle of the hot plate and the hydraulic pressure and temperature control; the operation of the cold press can effectively eliminate the stress and achieve high efficiency High quality for every pressing. Moreover, the machine itself has excellent processing accuracy, reliability and low failure rate, coupled with high-hardness, flat imported steel plate (one of the core accessories for pressing), Shengyi high-quality PP sheet (bonding sheet) and supporting professional equipment, It can effectively avoid process defects and improve the quality of pressing. The equipment of the famous machine can do:

.Avoid excessive flow of glue and uneven glue content between inner layers, which may lead to process defects such as warping and delamination of the board, and fully guarantee the high yield rate of multi-layer board lamination!

.The extremely low failure rate and precise automatic control can reduce production risks, maintain efficient and stable production, and save time for customers!

Finally realize the requirements and standards of high reliability + high stability.

MVLP vacuum and pressurization process: The vacuum chamber is composed of upper and lower hot plates, each with built-in heaters. The product is put into the hot plate, the hot plate is closed (a cavity is formed), and the inside is in a vacuum state. After the set time, the air cushion gets compressed air supply and expands, pressing the product on the hot plate. Through this pressing force and heat, the pressing is performed.

In addition, what other factors will affect the pressing yield?

(1) Quality of laminated steel plate:

Steel plate is one of the core accessories for pressing. The hardness and poor flatness of the laminated steel plate will have a huge impact on the process. If the quality is not good, it will cause serious consequences to the production of PCB (such as: the precision of the thickness tolerance Not high, there are indentations on the board surface, etc.)

(2) High-precision X-RAY drilling target machine, hot melt machine:

The X-ray drill target machine is used for interlayer alignment after pressing. The principle is to project the pad through X-ray perspective after pressing the multilayer board to judge the degree of fit between the inner layers and drill holes at the location (drilling target); The hot melt machine uses high temperature and pressure to bond and fix the PP board and the core board (commonly known as "fusion"), while the common riveting process presses, the disadvantages are as mentioned above. The alignment accuracy between the layers is affected by the tolerance of the rivet hole, and the impact during pressing will cause the rivet to deform and cause the deviation between the layers.

(3) PP bonding sheet:

PP sheet is a kind of sheet material in which the resin is in the B-stage. Under the action of temperature and pressure, it has fluidity and can quickly cure and complete the bonding process, and together with the carrier, it forms an insulating layer. The quality of the PP sheet also affects the reliability and stability of the multilayer board.

Therefore, if PCB factories want to produce high-quality PCBs, they must master this technology.