TWI339553B - Two-layer printed circuit board and method that make impedance controlled - Google Patents

Description

1339553

[丨 09 09 09 09 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 六 六 六 六 六 六 六 六 六 六 六 六 六 六 六 六 六 六 六 、 六 、 、 、 、 、 、 、 In particular, a two-layer printed circuit board and method for achieving impedance control in high-speed signal wiring. [Prior Art] [0002] As the output switching speed of integrated circuits increases and the wiring density of PCBs increases, 'signal integrity has become a concern for high-speed digital p C B design. The parameters of components and PCBs, the layout of components on the PCB, and the wiring of high-speed signals can cause signal integrity problems, resulting in unstable system operation or even no stomach. The design process takes full account of the signal integrity |, ^% # control measures has become a hot topic in today's PCB design industry ^ ‘for the PCB threat line.' (4) (four) integrity is the most important impedance matching. When the characteristic impedance of the transmission line does not match the load impedance, the y part of the energy after the signal is received will be reversed along the transmission line, causing the signal waveform to become erratic or even overshoot and undershoot the signal. If the signal is reflected back and forth on the transmission line, a round-trip oscillation will occur. The beta of the impedance of the transmission line = the width of the steel wire, the thickness of the steel wire, and the dielectric constant of the medium: the thickness of the pad = the thickness of the pad, the path of the ground wire, and the impedance of the transmission line around the trace The method can refer to the corresponding formula, such as.

[0003] where is the characteristic impedance of the transmission line '0 £ is the dielectric constant r' of the medium is the width of the transmission line ' _ ί is the thickness of the transmission line, is the medium 093131362 Form number Α 0101 $ 4 pages / a total of 15 pages 0993344619-0 1339.553 September 24, 2009, shuttle 1 replacement page

The thickness. In the prior art, four or more layers of PCBs achieve the required transmission line impedance by the transmission line structure formed by the transmission line and the reference ground plane, and different transmission line types require different transmission line standard impedance values. The industry standard PCB thickness is about 62 mils (one thousandth of an inch, about 0.0254 mm), as shown in the first four-layer PCB structure, including a plurality of transmission lines 100, dielectric layers 110, 130 and ground layer 120, which can The standard impedance of the transmission line that achieves impedance matching is 60 ohms. The dielectric layer 110 has a dielectric constant of 4, the transmission line 100 has a width of 5 mils, the transmission line 100 has a thickness of 2.1 mil, and the dielectric layer 110 has a thickness of 4.4 mil. The characteristic impedance of the transmission line is calculated according to an empirical formula. 54. 7 ohms, basically meet the requirements of impedance matching. In addition, it can also be imitation: true: soft release multiply pair; calculate the impedance of the transmission line, input the two-dimensional cross-section of the transmission line, the medium nose and the transmission of the % line structure into the simulation software, imitation 'true soft seven will know ^ The electromagnetic field generated by the transmission line and the ground plane calculates the impedance of the transmission line. [0004] In an I/O card, the use of a two-layer PCB does not require a ground plane I··· _ in the dielectric layer, which can greatly reduce the cost per unit area. However, it is known that the two-layer PCB # structure does not have a standard wiring specification, and is generally used in the blank of the PCB. X · • · · A large area of copper is applied to the ground to be used as a ground line, so that it is used in high-speed signal wiring. It is difficult to achieve impedance matching. The two-layer PCB structure as shown in the second figure includes a plurality of transmission lines 150, a ground layer 160, and a dielectric layer 170. The thickness of the dielectric layer is 56 mil. According to the above empirical formula, the characteristic impedance of the transmission line 150 is 150 ohms, which obviously does not meet the requirements of impedance matching. If the characteristic impedance of the transmission line 150 is equal to 60 ohms, according to the above empirical formula, γ is The width of the transmission line 150 needs to be 82 mils, which is an unreasonable design in the PCB. And a ground layer 160 is also 093131362 Form No. A0101 Page 5 of 15 0993344619-0 1339553 Correction of replacement on September 24, 099 [0005] [0006]

The plurality of transmission lines 150 are not considered to have a pain resistance control requirement. When the simulation software is used, the two-dimensional wear formed by the plurality of transmission lines 150 and a ground layer 丨60 cannot control the characteristic impedance value of each transmission line 15 。. SUMMARY OF THE INVENTION It is an object of the present invention to provide a two-layer printed circuit board and method for achieving impedance control. For the purpose of the present invention, the two-layer printed circuit board of the present invention comprises a dielectric layer and a plurality of high-speed signal transmission lines disposed on the dielectric layer. The dielectric layer is further disposed adjacent to each high-speed signal transmission line. Stratum. The high-speed signal transmission line and the high-speed signal transmission line and the ground layer are in a pair of parameter values corresponding to a characteristic impedance value, and the high-speed signal transmits the differential signal transmission line. The method for achieving impedance control of the two-layer printed circuit board of the present invention is to arrange a ground layer adjacent to each high-speed signal transmission line on the dielectric layer of the two-layer printed circuit board, and then to form a two-dimensional cross section of the two-layer printed circuit board. The graphic is input to a simulation software, and the simulation software calculates that the characteristic impedance value of the high-speed signal transmission line is compared with the standard impedance value, and if the

If the impedance value is not equal to or close to the standard impedance value, adjust the parameter value of the high-speed signal transmission line and the relative position of the high-speed signal transmission line and the ground layer, and then re-calculate the two-dimensional graph of the above-mentioned section until the obtained characteristic impedance value Equal or close to the standard impedance value. [0007] Hey! The trick is that the two-layer printed circuit board can simulate the soft second transmission line with the characteristic impedance value of the signal transmission line to achieve high-speed transmission line matching with other negative impedances. [Embodiment] 093131362 Form Dock Number Α0ΠΗ Page 6 of 15 0993344619-0 [0008]

[0008] Uy9 years old September 24th g Zheng J I U years old September:

The first embodiment of the present invention can realize two-layer printed circuit board and method for impedance control. π Refer to n two-layer printed circuit board 3 including a plurality of high-speed signal transmission lines (in this embodiment, single-ended transmission line 10), a dielectric layer 20, a plurality of grounding layers 3 (3 and (4) low-key lines 4 〇. Each side of the single-ended transmission line 1G is disposed - the ground layer 30, the ground layer 3G and the single-ended transmission line ίο are arranged side by side on the dielectric layer 2 (), The thickness t of the grounding_ is equal to the thickness t of the single-ended transmission line 1G, the length of the grounding layer 3G, the length of the material transmission line 10. The width of the single-ended transmission line 10 is, the distance from each grounding layer 30 to the single-ended transmission line 1G & To achieve the impedance control of the single-ended transmission line 1 'first input the two-dimensional circular shape as shown in the third figure to a simulation software' such as 2D Extract〇r, Ning will divide the two-dimensional graphic components of the section Electromagnetic field 'calculates characteristic impedance

The value 'if the calculated characteristic impedance t is not f. Combined with the standard impedance value of the transmission line required by the brush board 3, the value of the parameter w, s, t is adjusted (the thickness t of the single-ended transmission line 10 is generally 2) The lmu is mainly adjusted to the value of W'S, and then the other two-dimensional graphics determined by these three parameters are input to the simulation software, and the characteristic impedance value of the single-ended transmission line is recalculated. After multiple parameter values: adjustment, multiple conversion of two-dimensional pattern, multiple calculations of simulation software, find the group parameter value close to or equal to the standard impedance value 'according to this set of parameter values to the single-ended transmission line 10 and Two-layer 3G wiring can be used to achieve the impedance control of the single-ended transmission line 1G. In the present invention, only one grounding layer can be provided on one side of the single-ended transmission line, and the desired parameter value can be obtained by calculation of the simulation software. However, compared with _ each set-ground layer, the latter has the advantage of being able to eliminate the interference of other transmission lines to the single-material transmission line (four). The present invention can realize two-layer printed circuit board and method for impedance control. 093131362 Table arranging soft AG1G1 « _ 0993344619- # 7 page / total 15 pages ^39553 Correction replacement 09 on September 24, 099

Referring to the fourth figure, the two-layer printed circuit board 5 for USB2.0 signal transmission includes a plurality of high-speed signal transmission lines (the differential signal transmission line 50 in this embodiment), a dielectric layer 60, a plurality of ground layers 70, and a plurality of A low speed signal line is 8 〇. The differential signal transmission line 50 includes two transmission lines 5 2, 5 4 of constant pitch, uniform length, and opposite signals. A plurality of ground layers 70 and differential signal transmission lines 50 are disposed on the dielectric layer 60. A ground layer 70 is disposed on each of both sides of each of the differential signal transmission lines 5A. The thickness of the ground layer 70 is equal to the thickness of the differential signal transmission line 50. The length of the ground layer 70 is equal to the length of the differential signal transmission line 50. The distance from each ground layer 30 to the adjacent transmission line is s, and between the transmission lines 52, 54. The distance is Κ. USB2.0 transmission line standard resistance <

The resistance is 90 ohms. The fourth shape is input to the simulation software, and the differential signal resistance value is calculated. After comparing with the standard impedance value, the reference parameter is adjusted and the number is 'F' T (the thickness T of the differential signal transmission line 50 is generally about 2. lmil). Main adjustment w, S, K

The value of the value). The other two-dimensional graph determined by the adjusted four parameters is input to the simulation software' to recalculate the characteristic impedance value of the differential signal transmission line 50. After multiple adjustments of the parameter values, multiple inputs of the two-dimensional pattern, and multiple calculations of the simulation software, find a set of parameter values that are close to or equal to the standard impedance value. In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. However, the above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art of the present invention should be included in the following claims. BRIEF DESCRIPTION OF THE DRAWINGS [0010] The first figure is a schematic cross-sectional view of a conventional four-layer printed circuit board impedance control. 093131362 Form No. Λ0101 Page 8 of 15 0993344619-0 1339553 September 24th, 2008, the second page is a schematic diagram of the two-layer printed circuit board. [0011] The third figure is a cross-sectional view of a first embodiment of a two-layer printed circuit board and method for achieving impedance control in accordance with the present invention. [0012] The fourth figure is a cross-sectional view of a second embodiment of a two-layer printed circuit board and method for achieving impedance control in accordance with the present invention. [Explanation of main component symbols] Two-layer printed circuit board: 3, 5 [0014] Transmission lines: 100, 150, 52, 54 [0015] Low-speed signal lines: 40, 80 [0016] Ground plane: 120, 160, 30 ' 7ΰ; ; . . : ;. [0017] Single-ended transmission line: 10 [0018] Dielectric layer: 110, 130, 170 ' 20 ' 60 [0019] Differential signal transmission line: 50 • · 093131362 Form No. A0101 Page 9 / Total 15 pages 0993344619-0

Claims (1)

1339553 _ September 24, 099 Amendment 苜7, the scope of application for patents: 1. A two-layer printed circuit board that can achieve impedance control, comprising: a dielectric layer; a complex pair of differential signal transmission lines, which are disposed on the dielectric layer Each pair of differential signal transmission lines includes a first signal transmission line and a second signal transmission line. The widths of the first and second signal transmission lines are first parameter values, and the distance between the first and second transmission lines is a second parameter. value; a plurality of grounding layers disposed on the dielectric layer, each of which is provided with a grounding layer on each side of the differential signal transmission line, and the distance between each of the grounding layers and the first or second signal transmission line adjacent thereto is the third The parameter values, the first to third parameter values are such that the pair of differential signals are transmitted or equal to the standard of the differential signal transmission line of the pair of differential signal transmission lines. The method includes the following steps: a0. Configuring a plurality of differential signal transmission lines on the dielectric layer, the differential signal transmission line includes a first signal transmission line and a second signal transmission line. The width of the first and second signal transmission lines is a first parameter value, and the distance between the first and second transmission lines is a second parameter value; a. on each side of each pair of differential signal transmission lines on the dielectric layer Each of the pool layers is disposed, and the distance between each ground layer and the first or second signal transmission line adjacent thereto is a third parameter; b. the pair of differential signal transmission lines, the ground layer, The two-dimensional graphic of the two-layer printed circuit board formed by the quality layer is input to a simulation software; c. the characteristic impedance value of the pair of differential signal transmission lines is calculated by the simulation software; d. the characteristic impedance value calculated by the c step and the pair High-speed signal transmission line mark 093131362 Form No. A0101 Page 10 / Total 15 page 0993344619-0 1339553 On September 24, 099, the shuttle is replacing the quasi-impedance value comparison; e. If c step A, the characteristic impedance value and the standard impedance value If they are not equal or not close, the first to third parameter values are adjusted, and the process returns to step b, and if the values of the two are equal or close, the process ends. 093131362 Form No. A0101 Page 11 of 15 0993344619-0