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Difficulties and precautions in processing thick copper circuit boards
2023/05/24

Heavy Copper PCB Manufacturing

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Thick copper PCB is divided into single-sided thick copper circuit board, double-sided thick copper circuit board and multi-layer thick copper circuit board. Because of the thicker copper thickness,thick copper circuit board brings a series of processing difficulties to PCB processing. For example, multiple etching is required. , Insufficient glue filling on the pressure plate, cracking of the innerpad of the drilled hole, difficulty in guaranteeing the quality of the hole wall, etc. The minimum aperture of mechanical drilling in pcB processing has dropped from the original 0.4mm to 0.2mm, or even smaller, so the aperture of the metallized hole is getting smaller and smaller. Copper PCB reliability. So, what are the difficulties and precautions in processing thick copper circuit boards?



1. Difficulties in etching

With the increase of copper thickness, due to the difficulty of chemical solution exchange, the amount of side erosion measured will become larger and larger. In order to reduce the large amount of side erosion caused by liquid solution exchange as much as possible, multiple times of rapid etching are required. To solve the problem, as the amount of side erosion increases, it is necessary to compensate for the side erosion by increasing the etching compensation coefficient.


2. Difficulties in lamination

With the increase of copper thickness, the line gap is deeper, and under the same residual copperratio, the required amount of resin filling needs to increase accordingly, so it is necessary to use multiple prepregs to meet the problem of glue filling; due to the need to use resin to the maximum Filling line gaps and other parts, high glue content, and good resin fluidity prepreg is the first choice for thick copper plates. The commonly used prepregs are 1080 and 106. When designing the inner layer, place copper points and copper blocks in the copper-free area or the final milling area to increase the residual copper rate and reduce the pressure of glue filling.


An increase in the amount of prepreg will increase the risk of slippery boards, and the method of adding rivets can be used to strengthen the degree of fixation between the core boards. Under the trend of increasing copper thickness, resin has also begun to be used to fill the blank areas between graphics. Since the total copper thickness of the thick copper plate is generally above 205.8um (6 oz), the CTE matching between the materials is particularly important [for example, the CTE of copper is 0.0017%(17ppm), and the CTE of glass fiber cloth is 0.0006%-0.0007%(6ppm -7ppm), the resin is 0.02%]. Therefore, in the process of PCB processing, the selection of plates with fillers, low CTE and high Td is the basis for ensuring the quality of thick copper circuit boards.


As the copper thicker than the board thickness increases, more heat is required for lamination. The actual heating rate will be slower, and the actual duration of the high temperature section will be shorter, which will lead to insufficient curing of the resin of the prepreg, thereby affecting the reliability of the board; therefore, it is necessary to increase the duration of the lamination high temperature section to ensure The curing effect of the prepreg. If the prepreg is not cured enough, it will cause a large amount of glue removal relative to the core board prepreg, forming a ladder sh

ape, and then the hole copper will break due to the stress.


3. Drilling difficulties

As the copper thickness increases, the thickness of the thick copper PCB also increases. Thick copper plates usually have a plate thickness of more than 2.0mm. Due to the thicker plate thickness and thicker copper thickness during drilling, it is more difficult to manufacture. In this regard, the use of new tools reduces the service life of drill tools, and segmental driling becomes an effective solution for drilling thick copper plates. In addition, the optimization of drilling-related parameters such as feed speed and retract speed has a great influence on the quality of the hole.



For the problem of milling target holes, when drilling holes, the energy of X-RAY gradually decays with the increase of copper thickness, and its penetration ability will reach the upper limit. Therefore, for PCBs with thicker copper thickness, it is impossible to confirm the first board when drilling. In this regard, the deviation confirmation target can be set at different positions on the edge of the board, and the deviation confirmation target line can be milled out on the copper foil accordi

ng to the target position in the data when cutting the material, and the target hole on the copper foil and the inner surface can be cut out during lamination. Layer target holes correspond to production.


The problem of cracking of inner layer thick copper pads (mainly for large holes above 2.5mm) There are more and more needs for thick copper plates, and the inner pads are getting smaller and smaller, and the problem of cracking pads often occurs when PCB is drilled. There is little room for improvement in this type of problematic material. The traditional improvement method is to increase the pad, increase the peeling strength of the materiall, and reduce the drilling speed. From the analysis of PCB processing design and process, an improvement plan is proposed: copper removal treatment (that is, concentric circles smaller than the hole diameter are etched away when the pad is etched on the inner layer) to reduce the pulling force of the copper in the drilled hole. Drilling Drill a lead hole 1.Omm smaller than the hole diameter first, then perform normal drilling (that is,perform secondary drilling) to solve the problem of cracking of the inner thick copper pad.


Traditional thick copper plates are generally used in fields such as power control and military industry. However, with the rapid promotion of new energy vehicles, the importance of thick copper plates in the field of circuit boards has risen rapidly. It can be expected that the demand for thick copper plates will increase in the near future. There will be explosive growth. But at the same time, the increasingly high requirements of customers have also brought a lot of challenges to PCB man

ufacturers. Leading circuits believes that with the advancement of material technology and PCB manufacturers' technology, many problems will be solved.


If you are looking for a Heavy Copper PCB manufacturer, Ucreate offers complete solutions that you need for your PCB development.




Send Your Inquiry to Sales@ucreatepcb.com, we will quote you in 2 hours!



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