With the development of high-density and high-precision electronic products, new requirements are imposed on circuit boards. An effective method to increase PCB density is to reduce the number of vias and incorporate blind holes. To meet these demands, HDI boards can be produced, exemplified by professional 32-layer circuit boards.

1. Halogen-free materials have unique properties.

The water absorption performance is 1.1.

The water absorption rate of halogen-free materials is lower than that of standard epoxy resins. This is primarily because the isolated electrons of nitrogen and phosphorus in nitrogen-phosphorus epoxy resins are less prone to forming hydrogen bonds in water compared to halogen compounds. Consequently, the water absorption rate of these materials is lower than that of traditional halogen flame-retardant materials. Reducing the water absorption rate will significantly impact material performance, especially in professional 32-layer circuit boards.

This improves the reliability of the materials.

2. Enhancing the stability of materials during the PCB process.

This also improves the thermal performance of the material.

1.2. The dielectric constant.

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The factors that affect a material’s dielectric constant are primarily determined by the following elements: the dielectric constant of glass fiber, epoxy resin, and fillers. The overall dielectric performance of the epoxy resin can be somewhat compromised when it is replaced with P or N. Consequently, the electrical insulation of halogen-free epoxy resin tends to be superior to that of halogen-containing epoxy resin. A quick sample of a 32-layer circuit board shows that the insulation performance of the material is rated at 1.3.

The halogen-free epoxy resin enhances the polarity of traditional epoxy resin to some extent, improving both the insulation resistance and impact resistance of the medium.

The process flow and technology for buried and blind via multilayer boards generally utilize the sequential lamination method. This involves the following steps: forming a core board (akin to a traditional double-sided or multilayer board), followed by lamination. The subsequent processes mirror those of a conventional multilayer board.

Note 1: The formation of the core board refers to a double-sided or multilayer board created using traditional methods. The buried or blind via multilayer board is structured according to specific design requirements. If the thickness of the via is relatively large, it should be filled to ensure reliability.

For a 32-layer circuit board: when the temperature rises to a certain range, the substrate transitions from a glassy state to a rubbery state. This temperature is referred to as the glass transition temperature (TG) of the material. In other words, TG indicates the temperature at which the base material retains its rigidity. Standard PCB substrate materials not only soften, deform, and melt at elevated temperatures but also exhibit a significant decline in mechanical and electrical characteristics.

Why is the copper foil so thin? There are two main reasons: First, uniform copper foil has a consistent temperature coefficient of resistance, resulting in lower signal transmission loss, which is critical for capacitance requirements. Capacitors require a higher dielectric constant to achieve greater capacity in a limited volume, making them smaller than aluminum capacitors. Second, the temperature of thin copper foil rises under high current conditions, aiding heat dissipation and prolonging component life. This principle applies to digital integrated circuits as well, where copper wire widths are less than 0.3 cm. A well-made PCB finished board is characterized by its uniformity and soft gloss (due to the brushed solder resist), easily visible to the naked eye.

Dingji Electronics is a company specializing in the processing and production of printed circuit boards, offering advantages in single-sided, double-sided, and multilayer printed circuit boards. We can provide high-quality, high-precision eight-layer circuit board production.

The holes and blind holes in boards with more than eight layers are drilled from the top layer to the bottom layer, with blind holes being invisible from either the top or bottom surface. In other words, blind holes are drilled from the surface without penetrating all layers. Another type of hole, known as a buried hole, means that the bottom of the inner layer through hole is concealed. The advantages of buried and blind vias include increased wiring space.