JP2008270239A - Multilayer printed wiring board - Google Patents

Abstract

Provided is a multilayer printed wiring board in which even if the characteristic impedance of a transmission line and the characteristic impedance of a signal transmission through hole are mismatched, the characteristic impedance of the entire transmission line is not mismatched depending on the location.
A characteristic impedance between the first transmission line 10 which is set to Z _{0 (Omega),} the first connection line 12 connected to the first transmission line 10, the characteristic impedance is set to Z _{0 (Ω)} A second transmission line 11, a second connection line 13 connected to the second transmission line 11, and a signal transmission through hole 14 connected to the first connection line 12 and the second connection line 13. The length of the through-hole vicinity line 15 composed of the first connection line 12, the signal transmission through-hole 14, and the second connection line 13 is set to L (mm) calculated by the equation, and the first connection Both are the multilayer printed wiring boards in which the characteristic impedance of the line 12 and the second connection line 13 is set to Z ₁ (Ω) calculated by the equation.
[Selection] Figure 1

Description

  The present invention relates to a multilayer printed wiring board having a transmission line connected by a signal transmission through hole, and more specifically, even if the characteristic impedance of the transmission line and the characteristic impedance of the signal transmission through hole are mismatched, The present invention relates to a multilayer printed wiring board capable of matching the characteristic impedance of the entire transmission line including a through hole for signal transmission.

  In this type of multilayer printed wiring board, the characteristic impedance of the signal transmission through-hole, where the signal quality is not taken into consideration, is small compared to the characteristic impedance of the transmission line connected to the signal transmission hole. The current situation is to do. In this case, the transmission signal is reflected at the connection point between the transmission line and the signal transmission through hole, resulting in a decrease in the transmission quality of the transmission signal.

Therefore, as a technique for setting the characteristic impedance of the signal transmission through hole to match the characteristic impedance of the transmission line connected to the signal transmission through hole, there is a technique of providing an additional material as an installation potential around the signal transmission through hole. Yes (see Patent Document 1 and Patent Document 2).

  However, since these techniques provide an additive around the signal transmission through-hole, when the multilayer printed wiring board is intended to be densely wired, the additive becomes a barrier. Also, if the adduct must have a fine structure, the manufacturing difficulty increases.

  Therefore, as a technique for matching the characteristic impedance of the signal transmission through hole and the transmission line without providing any additional material around the signal transmission through hole, the signal transmission through hole is connected to the signal transmission through hole. By devising the shape of the vicinity of the hole, there is a technique of matching the characteristic impedance of the part composed of the signal transmission through hole and the vicinity with the characteristic impedance of the transmission line (see Patent Document 3 and Patent Document 4). reference).

Patent Document 3 discloses a multilayer printed wiring board having a through-hole connection portion composed of a through-hole and a planar circuit, for matching adjustment for adjusting the characteristic impedance of the through-hole connection portion to the planar circuit of the through-hole connection portion. A multilayer printed wiring board provided with a planar circuit is described. The planar circuit for matching adjustment includes a transmission line for matching adjustment and a stub connected to the other end of the transmission line for matching adjustment, or a plurality of serially connected plural lines having at least two different line widths. It consists of a transmission line for matching adjustment. According to the present invention, the characteristic impedance of the through-hole connecting portion and the characteristic impedance of the transmission line can be matched by appropriately setting these widths and lengths.

  In Patent Document 4, the transmission line is provided with a wide portion and a narrow portion, and by setting the length of the narrow portion to a specific setting range, the characteristic impedance near the through hole is reduced. A multilayer printed wiring board capable of preventing the above is described.

Japanese Patent Laid-Open No. 05-206678 Japanese Patent Laid-Open No. 11-150371 JP 2001-308547 A JP 2006-211070 A

  According to the techniques described in Patent Document 3 and Patent Document 4, manufacturing difficulty is small and high-density wiring can be handled. However, in these techniques, a method for giving an optimum set value for various configurations is not clearly described. Therefore, obtaining the optimal setting value is only by trial and error, and it is not easy to obtain an appropriate setting value.

  Therefore, the present invention provides a multilayer printed wiring board having transmission lines connected by signal transmission through holes, even if the characteristic impedance of the transmission lines and the characteristic impedance of the signal transmission through holes are mismatched. It is an object of the present invention to provide a multilayer printed wiring board that can match the characteristic impedance of the entire transmission line including the through-hole for use and can easily obtain an appropriate set value for the matching.

The invention according to claim 1 for solving the above-described problem is that a first transmission line whose characteristic impedance is set to Z ₀ (Ω) on one surface and a first connection line connected to the first transmission line are provided. A second transmission line having a characteristic impedance set to Z ₀ (Ω) and a second connection line connected to the second transmission line are provided on the other surface; The second connection line is a multilayer printed wiring board in which signal transmission through holes are connected.

Specifically, in the multilayer printed wiring board, the length of the through-hole vicinity line composed of the first connection line, the signal transmission through-hole, and the second connection line has the length (1) according to claim 1 and It is set to L (mm) calculated by (2), and the characteristic impedances of the first connection line and the second connection line are both calculated by the equation (3) according to claim 1. It is set to be Z ₁ (Ω).

  The multilayer printed wiring board according to claim 1 can easily match the characteristic impedance of the line near the through hole to the characteristic impedance of the first transmission line and the second transmission line. In other words, even if the characteristic impedance of the transmission line and the characteristic impedance of the signal transmission through-hole are mismatched, the characteristic impedance of the entire transmission line is not mismatched depending on the location. Can be easily obtained.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged view of the vicinity of a signal transmission through hole 14 provided in a multilayer printed wiring board of the present invention. Specifically, referring to FIG. 1, a first transmission line 10 having a characteristic impedance set to Z ₀ (Ω) and a first transmission line 10 connected to the first transmission line 10 are provided on one surface of the multilayer printed wiring board. 1 connection line 12 is provided, and on the other side, the second transmission line 11 whose characteristic impedance is also set to Z ₀ (Ω) and the second connection line connected to the second transmission line 11 are provided. 13 is provided. Further, the first connection line 12 and the second connection line 13 are connected by a signal transmission through hole 14. In the actual multilayer printed wiring board, the first transmission line 10, the first connection line 12, the second connection line 13, and the second transmission line 11 are covered with a solder resist. In FIG. 1, this solder resist is not shown.

FIG. 2 is a diagram schematically showing a cross section of the multilayer printed wiring board taken along line AA in FIG. In FIG. 2, the solder resist and the wiring formed in the inner layer are not shown. In FIG. 2, a transmission line including the first connection line 12, the signal transmission through hole 14, and the second connection line 13 is referred to as a through-hole near line 15. The length of the through-hole vicinity line 15 is set to L (mm) calculated by the following formulas (1) and (2). Furthermore, the characteristic impedances of the first connection line 12 and the second connection line 13 are both set to be Z ₁ (Ω) calculated by the following equation (3).

ｌ_ｔｈ：信号伝送用スルーホール１４の長さ（ｍｍ）
ｌ_１：第１接続線路１２及び第２接続線路１３の長さ（ｍｍ）であって、下記式により算出する。
ｌ_１≦（Ｌ−ｌ_ｔｈ）／２
Ｚ_ｔｈ：信号伝送用スルーホール１４の特性インピーダンス（Ω） _{T r = 0.35 / f s ···} (1)
L = (T _r · C ₀ ) / (n · √ε _r ) (2)
T _r : rise time (s) of the signal flowing through the signal transmission through hole 14
f _s : frequency component (Hz) of signal flowing through signal transmission through hole 14
C ₀ : Light speed n: Constant (3.5 to 10) that defines the length that can be treated as a concentrated constant
ε _r : dielectric constant of insulating layer

l _th : Length of signal transmission through hole 14 (mm)
l _{1 is} the length (mm) of the first connection line 12 and the second connection line 13 and is calculated by the following equation.
l ₁ ≦ (L− l _th ) / 2
Z _th : Characteristic impedance (Ω) of through hole 14 for signal transmission

In FIG. 1, the widths of the first connection line 12 and the second connection line 13 are smaller than the widths of the first transmission line 10 and the second transmission line 11, respectively. This is the case when Z _th <Z ₀ .

On the other hand, when Z _th > Z ₀ , the widths of the first connection line 12 and the second connection line 13 are larger than the widths of the first transmission line 10 and the second transmission line 11, respectively, as shown in FIG. It becomes a big form.

In a multilayer printed wiring board in which the dielectric constant of the insulating layer is 4.7, the length of the through hole 14 for signal transmission is 1.60 mm, and the characteristic impedance Z _{0 of} the first transmission line 10 and the second transmission line 11 is 50Ω, characteristic impedance _{Z th} transmission through hole 14 was 45.6Omu.

When a signal with a frequency of 4 GHz is passed through the signal transmission through hole 14, the rise time T _r (s) of the signal flowing through the signal transmission through hole 14 is T _r = 0.35 / (4 × 10 ⁹ ) = 87. .5 × 10 ⁻¹² = 87.5 ps
It is.
Therefore, the length L of the through-hole vicinity line 15 at this time is n = 4.
L = (87.5 × 10 ⁻¹² × 3.0 × 10 ⁸ ) / (4 × √ (4.7))
= 3.03 × 10 ⁻³ (m)
= 3.03 (mm)
It becomes.

The length of the first connecting line 12 and the second connecting line 13 is l ₁ are as follows.
Since L = l ₁ + l ₁ + 1.60 = 3.03,
l ₁ = (3.03-1.60) /2=0.72 mm
It becomes.

Therefore, the setting value Z ₁ of the characteristic impedance of the first connection line 12 and the second connection line 13 is Z ₁ = 50 × (1 + 1.60 / (2 × 0.72)) − (45. 6 × 1.60 / (2 × 0.72))
= 54.9
(Ω)
It becomes.

  Therefore, the first connection line 12 and the second connection line 13 are both 0.72 mm in length, and their widths are set so that their characteristic impedance is 54.9Ω. This setting method may be a conventionally known method.

Close-up view of signal transmission through-hole on multilayer printed wiring board AA line cross-sectional view of multilayer printed wiring board View the enlarged vicinity of the signal transmission through holes in the case of Z _th> Z ₀

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 1st transmission line 11 2nd transmission line 12 1st connection line 13 2nd connection line 14 Signal transmission through-hole 15 Through-hole vicinity line

Claims (1)

A first transmission line whose characteristic impedance is set to Z ₀ (Ω) and a first connection line connected to the first transmission line are provided on one surface, and the characteristic impedance is Z ₀ (Ω) on the other surface. A second transmission line connected to the second transmission line, and a multilayer in which the first connection line and the second connection line are connected by a signal transmission through-hole. In the printed wiring board, the multilayer printed wiring board has a length of a through-hole vicinity line composed of the first connection line, the signal transmission through-hole, and the second connection line expressed by the following formulas (1) and ( 2) is set to L (mm), and the characteristic impedances of the first connection line and the second connection line are both Z ₁ (Ω) calculated by the following equation (3) and To be Multilayer printed wiring board, characterized in that it is.
_{T r = 0.35 / f s ···} (1)
L = (T _r · C ₀ ) / (n · √ε _r ) (2)
T _r : rise time (s) of signal flowing through signal transmission through hole
f _s : frequency component (Hz) of signal flowing through signal transmission through hole
C ₀ : Light speed n: Constant (3.5 to 10) that defines the length that can be treated as a concentrated constant
ε _r : dielectric constant of insulating layer

l _th : Length of signal transmission through hole (mm)
l _{1 is} the length (mm) of the first connection line and the second connection line, and is calculated by the following equation.
l ₁ ≦ (L− l _th ) / 2
Z _th : Characteristic impedance (Ω) of through hole for signal transmission

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