In this passage, we will tell you about the methods to choose right type of PCB substrate material. Come and check the content below.
Copper Foil Requirements
PCB substrate materials play an integral role in determining the durability and quality of your board. It is noticeable that the manufacturers are trying to move towards fine lines and high density.
You may have heard of the term HDI PCB. It stands for High-Density Interconnect Printed Circuit Board. Approximately ten years ago, a board needed to have line space (S) and line width (L) of not more than 0.1mm to be classified in the HDI category.
Today, the standards vary from one industry to another. Electronic products often have S and L set as low as 60μm, and they can even go to 40μm in advanced applications.
During circuit pattern formation, S and L can reach a value as low as 30μm once you apply a thin substrate made of copper foil. The recommended thickness can go from 9μm to 12μm.
The problem is that CCL (copper clad laminate) that is so thin can be expensive and prone to defects. It is the best explanation for why companies resort to using 18μm-thick copper foil. However, if S and L are not more than 20μm, the copper foil of standard thickness might not be the best solution.
1.1. How Surface Roughness Can Affect the Quality of Your PCB
If your goal is to design a suitable circuit, you also need to consider how rough the copper foil surface will be. Roughing will ensure that the conductors have peel strength and that bonding of the substrate material and the copper foil is optimal. The standard roughness nowadays is set to around 5μm.
If you want to boost peel strength, it may be wise to embed hump on the foil into the substrate. In this case, you want to keep the roughness as low as possible (preferably up to 1.5μm, but no more than 3μm).
You may be wondering how to peel strength will be kept if you reduce the foil roughness. The answer lies in the superior finish you apply to the surface of both the substrate and the foil. That way, the conductors can maintain optimal peel strength and ensure the reliable performance of your PCB.
2、Insulating Dielectric Laminates
The building up process is an essential property of HDI printed circuit boards. If you use resin-coated copper (RCC) or combine copper foil lamination with the prepreg cloth of epoxy glass, there is a good chance you will design a suitable circuit.
The manufacturers have also implemented the MSPA and SAP technologies. That secured generation of the copper conducting plane by applying insulating dielectric film lamination with chemical copper playing. It is the thin copper plane that is the main reason why we can produce suitable circuits.
2.1. Why Lamination Dielectric Material Is Crucial for SAP
We need to consider lamination material and its requirements if we are going to design HDI PCBs. Some considerations include dielectric performance, thermal capacity, insulation, and bonding.
If you look at packages with semiconductivity, the IC package may turn organic substrate from the ceramic. A decrease in the size of the FC package is noticeable as the values of S and L are around 15μm, with the tendency to become even more compact.
Multi-layered PCB substrate materials should reduce the thermal expansion coefficient and dielectric property while securing optimal resistance to heat. This type of substrate is the right choice as it can achieve all performance goals while maintaining an acceptable cost.
We use SAP technology in the manufacturing process of circuits when their space and width are below 10μm. In fine circuit production on a large scale, MSPA can be applied to thin copper foil to insulate dielectric lamination.
Why High Speed and High Frequency Are Important for Your PCB?
Technology is making tremendous progress every day. We have seen innovations like using wireless connections, high speeds, and high frequencies.
Smartphones are already taking advantage of the 5G network, which has impressive data speed and bandwidth capabilities. The high-speed design has been the topic of many experts in the industry.
The data traffic boost means we need to design devices that can handle those high speeds and frequency. It is essential to use materials that can deliver extraordinary performance while keeping the integrity of the signal and minimizing interference.
We can make a difference between:
• Medium Dk/Df laminate PCBs have Df no higher than 0.010, and Dk of maximum 4.
• Low Dk/Df laminate PCBs – in these boards, Df is less than 0.005, while Dk is no more than 3.7.