PCB Design Challenges for 10-Layer Multilayer Boards

Designing 10-layer or multilayer PCBs presents significant manufacturing challenges compared to conventional circuit board products. High-layer boards are characterized by a thicker board, more layers, denser circuits and vias, larger unit dimensions, and thinner dielectric layers. The requirements for inner layer space, interlayer alignment, impedance control, and reliability are more stringent.

I. Interlayer Alignment Challenges

Due to the multiple layers in high-layer boards, customers have increasingly strict requirements for interlayer alignment, typically controlled within ±75μm. Factors such as the larger unit size design of high-layer boards, environmental temperature and humidity in the graphic transfer workshop, and the inconsistency in expansion and contraction of different core board layers contribute to the increased difficulty in controlling interlayer alignment.

II. Inner Layer Fabrication Challenges

High-layer boards use special materials such as high-TG, high-speed, high-frequency, thick copper, and thin dielectric layers, which pose high demands on the fabrication of inner layers and control of graphic dimensions. This includes the integrity of impedance signal transmission, increasing the difficulty of inner layer fabrication. Small line widths and spacings lead to an increase in open and short circuits, micro shorts, and low yield rates. The probability of AOI inspection missing defects in dense signal layers is higher. Thin inner core board thickness is prone to wrinkles, leading to poor exposure and rolling during etching. Most high-layer boards are system boards with larger unit sizes, resulting in a higher cost of scrap.

III. Lamination Challenges

When multiple inner core boards and prepreg sheets are stacked, lamination production can easily lead to defects such as滑板、delamination, resin voids, and bubble residue. In the design of the lamination structure, it is necessary to fully consider the thermal resistance, voltage resistance, filling amount of materials, and dielectric thickness, and set a reasonable lamination program for high-layer boards. The control and dimensional compensation of expansion and contraction cannot be consistent due to the multiple layers; the thin interlayer insulation layer can easily lead to interlayer reliability test failure issues.

IV. Drilling Challenges

The use of special materials such as high-TG, high-speed, high-frequency, and thick copper boards increases the difficulty of hole roughness, burrs, and debur. With multiple layers, the cumulative total copper thickness and board thickness lead to easy breakage of drill bits; dense BGA leads to CAF failure issues due to narrow hole wall spacing; and board thickness easily leads to drilling inclination issues.