How to do PCB four-layer board conventional laminated structure and design solder mask

With the increasingly complex and high-speed circuit design, how to ensure the integrity of various signals (especially high-speed signals), that is, to ensure the signal quality, has become a difficult problem. At this time, it is necessary to analyze with the help of transmission line theory, and control the characteristic impedance matching of the signal line becomes the key. If the impedance control is not strict, it will cause considerable signal reflection and signal distortion, resulting in design failure.

Common signals, such as PCI bus, PCI-E bus, USB, Ethernet, DDR memory, LVDS signals, etc., all require impedance control. Impedance control ultimately needs to be realized through PCB design, and higher requirements are also put forward for the PCB board process. In the early stage, our company has released technical documents such as impedance calculation rules and basic knowledge. In order to meet the needs of some customers, the following will introduce our company's conventional 4-layer Laminated structures of various plate thicknesses and some common impedance calculation results, customers who need it can design the impedance line width and spacing according to the following recommended parameters:

1.The thickness of the finished plate is 1.6mm (laminated structure):

2.The thickness of the finished plate is 1.2mm (laminated structure):

3. The thickness of the finished plate is 1.0mm (laminated structure):

4. The thickness of the finished plate is 0.8mm (laminated structure):

The above four laminated structures are our 4-layer conventional laminated laminated structure. As can be seen from the figure, the PP used in the conventional laminated structure is 2116, and the thickness is about 0.12mm.

For our company's conventional pressing structure, the parameters of conventional impedance lines (such as L1 layer impedance line refer to L2 layer & L4 layer impedance line refer to L3 layer) parameters can refer to the following calculation results:

1. The outer layer line width is 0.195mm, and the single-ended impedance is controlled to 50+/-10% ohm (L1 Ref L2 layer, L4 layer Ref L3 layer)

2. Double-sided line width 0.19mm, line-to-copper spacing 0.254mm, control single-ended coplanar impedance 50+/-10% ohm (L1 Ref L2 layer, L4 layer Ref L3 layer)

3. Double-sided line width 0.1524mm, line spacing 0.2032mm, control differential impedance 100+/-10% ohm (L1 Ref L2 layer, L4 layer Ref L3 layer)

4. Double-sided line width 0.1868mm, line spacing 0.1778mm, control differential impedance 90+/-10% ohm (L1 Ref L2 layer, L4 layer Ref L3 layer)

This is the conventional laminate structure and design solder mask of the PCB four-layer board.