JP2009259879A - Wiring board, and multilayer wiring board - Google Patents

Abstract

【Task】
In order to reduce skew between wirings in high-speed signal transmission using differential wiring, there is a method of shortening the change in relative permittivity by inclining the wiring pattern and setting the angle between the wiring and the glass cloth. In this method, there is a problem that the degree of freedom of arrangement of the wiring pattern is lowered.
[Solution]
An insulating substrate having a glass cloth knitted with a plurality of warp yarns made of glass and a plurality of weft yarns made of glass, and a wiring board having a core layer comprising a differential wiring,
A filler is provided at a position to reduce a difference in relative permittivity between a region affecting the transmission characteristics of the first wiring of the differential wiring and a region affecting the transmission characteristics of the second wiring of the differential wiring. A wiring board characterized by.
[Selection] Figure 6

Description

  The present invention relates to a wiring board using a glass cloth for high-speed signal transmission.

  The server / router backplane board performs high-speed, long-distance (about 100 cm) signal transmission, so the quality of the signal waveform deteriorates due to the loss of the transmission line, and the influence of power supply / ground noise (common noise) increases. . In order to reduce the common noise, differential transmission is generally used in the backplane substrate. In differential transmission, signals are transmitted using a pair of signal lines, and signals in opposite phases are transmitted to the two signal lines (P wiring and N wiring). As a result of signal transmission, common noise having the same phase is placed on the two signal lines on the receiving side. Therefore, the common noise can be removed by taking the difference between the signals.

FIG. 1 is a sectional perspective view of a conventional multilayer wiring board used for high-speed transmission such as a backplane board. FIG. 2 is a conceptual diagram showing the configuration of a glass cloth used for the wiring board constituting the multilayer wiring board, and FIG. 3 is a cross-sectional view of the conventional wiring board.
A conventional multilayer wiring board 52 shown in FIG. 1 is formed by laminating a plurality of wiring boards 51a, 51b, 51c. Each wiring board 51a, 51b, 51c has a conductor layer 7 and an insulating layer 8. The conductor layer 7 includes a differential wiring 6 constituted by a P wiring 6p and an N wiring 6n, and a power / ground plane 11. And is configured.

  In FIG. 2, the conceptual diagram showing the structure of the 1st glass cloth 2a used for the conventional wiring board is shown. The first glass cloth 2a has a structure in which a plurality of glass warp yarns 4a and a plurality of glass weft yarns 5a are knitted, an intersection region 300 where both the warp yarns 4a and the weft yarns 5a exist, and the warp yarns 4a. And the weft yarn 5a are divided into a region (basket hole) 200, a region 100 where only the warp yarn 4a exists, and a region 101 where only the weft yarn 5a exists.

FIG. 3 shows a cross-sectional view of a conventional wiring board 51. The conventional wiring board 51 includes a first glass cloth 2a and a second glass cloth 2b knitted by a plurality of glass warps 4a and 4b and a plurality of glass wefts 5a and 5b, respectively, and these glass cloths. The insulating layer 8 is composed of a resin 3 that cures 2a and 2b, and the conductor layer 7 is composed of a power / ground plane 11 and a differential wiring 6. 3 includes a core layer 112 having a power / ground plane 11, a first glass cloth 2a, a resin 3, and a differential wiring 6, a second glass cloth 2b, and a resin 3. And a connection layer (prepreg layer) 113 having
The cross-sectional view of the conventional wiring substrate 51 shown in FIG. 3 is divided into a crossing region 300 and a region 101 where only weft yarns exist. Generally, in a substrate for high-speed transmission, the dielectric constant of glass cloth is the dielectric constant of the resin. Therefore, the inside of the wiring board has a relatively high density of glass cloths 2a and 2b having a relatively high dielectric constant, and a high density density of resin 3 having a low dielectric constant (area where only weft yarns exist) 101. It becomes a structure with a heterogeneous relative dielectric constant. As shown in FIG. 3, in most cases, the glass cloths 2a and 2b are not line-symmetrically arranged with respect to the center line of the differential wiring 6. For this reason, variation occurs in the relative dielectric constant inside the wiring board 51 as viewed from the differential wiring 6. The relative dielectric of the surrounding 3W region affecting the transmission characteristics of the P wiring 6p of the differential wiring and the surrounding 3W region affecting the transmission characteristics of the N wiring 6n with respect to the wiring width W120 of each wiring of the differential wiring. If there is a difference in rate, a skew (transmission waveform delay) occurs due to a difference in relative permittivity between both wirings. Further, the skew caused by the difference in relative permittivity between the P wiring 6p and the N wiring 6n is accumulated according to the angle between the glass cloth thread and the wiring. For this reason, when the differential wiring 6 and the warp or weft are arranged substantially in parallel, the smaller the angle, the greater the skew, which causes signal waveform deterioration.

  FIG. 4 is a diagram showing the difference in the differential transmission waveform due to the difference in the relative permittivity of the wiring board. FIG. 4A shows a transmission waveform of each wiring when there is no difference in relative permittivity of the wiring board and no skew, and FIG. 4B shows a difference in relative permittivity of the wiring board and there is a skew. It is a transmission waveform of each wiring in the case. If there is a difference in the relative permittivity of the wiring board, as shown in FIG. 4 (b), the transmission waveform is distorted due to the occurrence of skew due to the difference in the relative permittivity, leading to deterioration of the quality of the transmission waveform. Become.

  Conventional signal transmission also uses the above-mentioned differential transmission, which played an important role in removing common noise, but transmission system signal transmission compatible with recent high-speed and large-capacity server and router equipment As the speed increases, the reduction of the common noise removal rate due to the occurrence of skew between the differential wirings becomes remarkable. In order to further increase the speed of signal transmission, it is necessary to reduce the skew between wirings and sufficiently reduce common noise. Various proposals have been made for this requirement.

  In Non-Patent Document 1, the wiring pattern is inclined to form a certain angle between the glass cloth and the wiring, thereby shortening the change in relative permittivity and suppressing the accumulation of skew.

Design con 2007 6-TA2: Fiber Weave Effect: Practical Impact Analysis and Mitigation Strategies

  In the invention described in Non-Patent Document 1, the change in relative permittivity is shortened by inclining the wiring pattern and setting the angle between the wiring and the glass cloth. There is a problem that the degree decreases.

  An object of the present invention is to provide a wiring board and a multilayer wiring board that can suppress the occurrence of skew without lowering the degree of freedom of arrangement of wiring patterns and can be used even in high-speed signal transmission.

The following is a brief description of an outline of typical inventions disclosed in the present application.
(1) A wiring board having a core layer comprising a glass cloth knitted with a plurality of glass warps and a plurality of glass wefts, and a differential wiring,
A filler is provided at a position to reduce a difference in relative permittivity between a region affecting the transmission characteristics of the first wiring of the differential wiring and a region affecting the transmission characteristics of the second wiring of the differential wiring. A wiring board characterized by the above.
(2) A wiring board having a core layer comprising a glass cloth knitted with a plurality of warp yarns made of glass and a plurality of weft yarns made of glass, and a differential wiring,
Of the first region provided between adjacent warps among the peripheral regions that affect the transmission characteristics of the differential wiring, or the second region provided between adjacent wefts of the peripheral region A wiring board having a filler in at least one region.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a skew can be suppressed without reducing the freedom degree of arrangement | positioning of a wiring pattern, and the wiring board and multilayer wiring board which can be utilized also in high-speed signal transmission can be provided.

  Embodiments relating to the present invention will be described below with reference to the drawings.

<Example 1>
A first embodiment of the wiring board according to the present invention will be described with reference to FIGS.
FIG. 5 is a cross-sectional perspective view of a wiring board according to the present invention. FIG. 6 is a cross-sectional view of the wiring board of FIG. 5 taken along X1-X2. FIG. 7 is a cross-sectional view of the wiring board of FIG. 5 taken along Y1-Y2.

The cross-section of the wiring board shown in FIG. 6 includes a first glass cloth 2a knitted with a power / ground plane 11, a glass warp 4a and a glass weft 5a, and a resin 3 for curing the first glass cloth 2a. A core layer 112 including a differential wiring 6 as a signal layer and a filler 30 having a relative dielectric constant comparable to that of the first glass cloth 2a and the second glass cloth 2b, the second glass cloth 2b and the second glass cloth 2b And an adhesive layer (prepreg layer) 113 including a resin 3 for curing the glass cloth 2b.
The cross section of the wiring board shown in FIG. 6 is divided into an intersecting region 300 where the warp yarns 4a, 4b and the weft yarns 5a, 5b intersect, and a region 101 (region where the resin density is high) where only the weft yarns 5a, 5b exist. The region 101 is provided with a filler 30 having a relative dielectric constant comparable to that of the glass cloths 2a and 2b. The peripheral area 116 that affects the transmission characteristics of the differential wiring 6 is an area that is about three times as wide as the wiring width around the wiring. Of the areas 101 where only the weft threads 5a and 5b are present (area where the resin density is high) 101 When the filler 30 having a relative dielectric constant comparable to that of the glass cloths 2a and 2b is provided at least in the first region 117 which is a region included in the peripheral region 116, the relative dielectric constant of the peripheral region 116 is reduced. Since the difference is reduced and the variation in relative permittivity that affects the skew between the wirings of the differential wiring 6 is suppressed, the skew between the wirings of the differential wiring can be reduced, and the deterioration of the quality of the transmission waveform is suppressed. it can.

That is, in the cross-sectional view of the wiring board in FIG. 6, when the thickness of the glass cloth and filler in the height 122 of the wiring board is the glass cloth and filler thickness 123, the glass cloth in the peripheral region 116 and When the variation in the filler thickness 123 is small, the variation in the relative permittivity that affects the skew between the wirings of the differential wiring 6 can be suppressed, so that the skew between the wirings of the differential wiring can be reduced, and transmission Waveform quality degradation can be suppressed.
At this time, the filler 30 may be provided in the area | region which is not contained in the 1st area | region 117 among the area | regions 101 where only a weft exists.

FIG. 7 is a cross-sectional view of the wiring board of FIG. 5 taken along Y1-Y2. The wiring board shown in FIG. 7 includes a first glass cloth 2a knitted with a power / ground plane 11, a glass warp 4a and a glass weft 5a, a resin 3 for curing the first glass cloth 2a, and a signal layer. A core layer 112 including a P wiring 6p, a filler 30 having a dielectric constant comparable to that of the first glass cloth 2a and the second glass cloth 2b, and the second glass cloth 2b. It has a connection layer (prepreg layer) 113 including a resin 3 for curing the second glass cloth 2b.
The cross section of the wiring board shown in FIG. 7 is divided into an intersecting region 300 where the warps 4a, 4b and wefts 5a, 5b intersect, and a region (region where the resin density is high) 100 where only the warps 5a, 5b exist. In the region 100, a filler 30 having a relative dielectric constant comparable to that of the glass cloths 2a and 2b is provided. For example, assuming that the cross-sectional area shown in FIG. 7 is an area included in the peripheral area 116 that affects the transmission characteristics of the differential wiring, the glass is formed in the second area 118 provided between the adjacent wefts 5a and 5b. By providing the filler 30 having a relative dielectric constant comparable to that of the cloths 2a and 2b, the difference in relative dielectric constant is reduced, and variation in relative dielectric constant that affects the skew of the differential wiring is suppressed. The skew between the wirings can be reduced, and the quality deterioration of the transmission waveform can be suppressed.

Here, the power / ground plane 11 and the differential wiring 6 provided on both surfaces of the core layer 112 of FIG. 6 may be a base material formed of copper foil.
The warp yarn 4a and the weft yarn 5a of the glass cloth 2a provided in the core layer 112 are preferably yarns having a diameter of about 330 μm, in which about 100 glass fibers having a diameter of about 10 μm are bundled.
Further, the filler 30 is granular and has a dielectric constant comparable to that of the glass cloth 2a, and is preferably smaller than the diameter of the glass cloth 2a, and particularly preferably has a diameter of about 10 μm. However, when the relative permittivity of the filler is a value between the relative permittivity of the glass cloth and the relative permittivity of the resin, the difference in relative permittivity inside the wiring board 51 can be reduced.
In addition, the material of the filler 30 is not limited to epoxy and may be glass resin.
Further, the relative dielectric constant of the filler 30 is preferably a value close to that of glass cloth, and in particular, one having a relative dielectric constant of 4 to 5 is desirable.

  At this time, the amount of filler provided in the first region 117 in FIG. 6 or the second region 118 in FIG. 7 is larger than the amount of filler provided in the region included in the intersection region 300 in the peripheral region 116. In some cases, since the difference in relative permittivity in the peripheral region 116 can be reduced, the skew can be reduced and the quality deterioration of the transmission waveform can be suppressed. In this case, the filler 30 is provided in the intersection region 300. May be.

Further, the differential wiring 6 and the warp threads 4a, 4b or the weft threads 5a, 5b need not be arranged substantially in parallel, and the filler can be used even when the wiring pattern is arranged with an inclination. 30 can provide the same effect. That is, in this embodiment, it is possible to realize a wiring board in which the skew between wirings is reduced without reducing the wiring flexibility of the wiring pattern.
Moreover, although the connection layer 113 shown in FIG. 6 is comprised by the 2nd glass cloth 2b knitted with the warp 4b and the weft 5b, and the resin 3, similarly to the 1st glass cloth 2a, it is 2nd. In the glass cloth 2b, a filler 30 similar to the glass cloth 2a, 2b is formed in a region 101 where only the weft yarn 5b exists (region where the resin density is high) 101 or a region where only the warp yarn 5b exists (region where the resin density is high) 100. It may be provided. By making the adhesive layer 113 have not only the resin 3 but also the glass cloth 2b, the strength of the wiring board can be enhanced.
FIG. 8 is a cross-sectional view taken along line X1-X2 of the wiring board shown in FIG. 5. As shown in FIG. Also good. By forming the adhesive layer 113 from the resin 3, the distribution of the relative dielectric constant in the adhesive layer 113 becomes more uniform, and the occurrence of skew due to the adhesive layer 113 can be greatly reduced.
Further, the relative permittivity of the first region 117 or the second region 118 shown in FIG. 6 and FIG. 7 and the third region not included in any of the first region and the second region among the peripheral regions 116. When the filler is provided at a position where the difference from the relative dielectric constant of the region is reduced, variation in the relative dielectric constant in the peripheral region 116 is reduced.
Further, among the plurality of warp yarns and the plurality of weft yarns, the plurality of yarns provided substantially in parallel with the differential wiring, by having a filler in a region provided between adjacent yarns in the peripheral region 116, The difference in relative permittivity can be reduced. At this time, the total thickness of the glass cloth and the filler 123 in the region provided between the adjacent yarns in the peripheral region 166 and the region provided between the adjacent yarns in the peripheral region are included. When the filler is provided at a position where the difference between the glass cloth and the total thickness 123 of the filler in the non-existing region is reduced as compared with the case where the filler is not provided, the relative dielectric constant inside the wiring substrate 51 Variation in rate is reduced.

The multilayer wiring board is formed by laminating a plurality of wiring boards described in the embodiments of the present invention. A multilayer wiring board is formed by alternately laminating a plurality of conductor layers and insulating layers constituting the wiring board. At this time, the number of conductor layers and insulating layers can be arbitrarily selected.
At this time, when the glass substrate is included in the adhesive layer portion constituting the wiring board, high strength can be realized for the multilayer wiring board.
Also, if the adhesive layer part that constitutes the wiring board does not contain glass cloth and is made of resin, the occurrence of skew due to variations in the relative permittivity of the adhesive part can be suppressed, and the quality of the transmission waveform deteriorates. Can be suppressed.

  Next, the manufacturing process of a filler is demonstrated using FIG. Glass fibers 124 having a diameter of about 10 μm are converged to create glass fiber yarns 125 (step step 1). Next, the glass fiber yarn 125 is finely cut to produce a glass fiber piece 126 (step step 2). Then, the glass fiber piece 126 is grind | polished and the glass filler 30a is created (process step3).

  Next, the manufacturing process of the core layer 112 of the wiring board according to the first embodiment shown in FIG. 6 will be described with reference to FIG. The first glass cloth 2a is formed by knitting yarns of about 100 glass fibers having a diameter of about 10 μm (step step 1). At this time, the warp 4a and the weft 5a having a diameter of about 330 μm are almost orthogonal to each other. Next, the filler 30 (with a relative dielectric constant of about 5 and a diameter of about 10 μm) is mixed with the resin 3 to create a paste-filled resin, and the entire first glass cloth 2a is immersed in the resin (step step 2). ) After the filler-filled resin is infiltrated into the gaps of the first glass cloth 2a, the first glass cloth 2a is dried to semi-harden the filler-filled resin (step step 3). At this time, FR4 resin (epoxy resin) may be used as the resin. The first glass cloth 2a semi-cured including the resin containing filler is dipped in resin 3 (assuming that it does not contain filler) (step step 4) and dried to semi-cur the resin 3 (step step 5). One glass cloth 2a is cut into a size of 60 cm (warp direction) × 120 cm (weft direction) to form an insulating layer portion of the core layer 112 having a thickness of about 150 μm (step step 6). After that, a conductor layer 7 is formed by copper etching on both sides of the cut first glass cloth 2a, and a core layer 112 is prepared in which a ground plane 11 is provided on one side and a differential wiring 6 of a stripline transmission line is provided on the other side. (Step step 7).

  Next, a process for forming the adhesive layer 113 of the wiring board shown in FIG. 8 will be described. For the adhesive layer 113, an insulating base material that does not include a glass cloth having a thickness of about 150 μm as in the core layer 112 is formed using a resin. A base material mixed with a filler having a high relative dielectric constant may be used instead of resin for the purpose of adjusting the relative dielectric constant, or the base material of the adhesive layer 113 and the base material of the core layer 112 may be exchanged. May be.

  Next, the manufacturing process of a multilayer wiring board is demonstrated using FIG. The daughter board 1 a is electrically connected to the differential wiring 6 in the multilayer substrate 1 via connectors 9 a and 9 b installed on the multilayer substrate 1. The differential wiring 6 provided in the core layer of the wiring board has a wiring width of 100 μm, a wiring interval of 100 μm, and a conductor thickness of 20 μm in order to obtain a characteristic impedance of 30Ω, and electrically connects a distance of 100 cm between the connectors 9a-9b on the board. To do. A plurality of core layers 112 and adhesive layers 113 are arbitrarily selected and laminated alternately, and then pressed and bonded at a high temperature to form a multilayer wiring board. The differential wiring 6 may be a microstrip line transmission line instead of the strip line transmission line, or may be a single-end wiring instead of the differential wiring. As a finishing process, the resin that has flowed out to the outer periphery of the multilayer substrate 1 is cut and removed to finish a multilayer wiring board having a finished dimension of 50 cm (warp direction) × 110 cm (weft direction).

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. Not too long.

It is a figure which shows the conventional multilayer wiring board. It is a block diagram of the glass cloth used for the conventional wiring board. It is sectional drawing of the conventional wiring board. It is a figure which shows the difference in the differential transmission waveform by the difference in the dielectric constant of a wiring board. It is a section perspective view of the wiring board concerning the present invention. It is sectional drawing of the wiring board which concerns on the 1st Example of this invention. It is sectional drawing of the wiring board which concerns on the 1st Example of this invention. It is sectional drawing of the wiring board of the modification based on 1st Example of this invention. It is a figure which shows the manufacturing process of the core layer of the wiring board which concerns on the 1st Example of this invention. It is a figure which shows the manufacturing process of the multilayer wiring board comprised by the wiring board which concerns on the 1st Example of this invention. It is a figure which shows the manufacturing process of a filler.

Explanation of symbols

2a 1st glass cloth, 2b 2nd glass cloth, 3 resin, 4a, 4b warp, 5a, 5b weft, 6 differential wiring, 6p P wiring, 6n N wiring, 7 conductor layer, 8 insulating layer, 9a, 9b Board connector 11 Power / ground plane, 30 filler, 30a glass filler, 51, 51a, 51b, 51c wiring board, 52 multilayer wiring board, 100 area where only warp yarn exists (area with high resin density), 101 weft Region where only resin exists (region where resin density is high), 112 core layer, 113 connection layer (prepreg layer), 116 peripheral region, 117 first region, 118 second region, 122 height of wiring board, 123 Glass cloth and filler thickness, 124 glass fibers, 125 glass fiber yarns, 126 glass fiber yarn pieces, 200 basket holes, 300 crossings region

Claims (15)

An insulating substrate having a glass cloth knitted with a plurality of warp yarns made of glass and a plurality of weft yarns made of glass, and a wiring board having a core layer comprising a differential wiring,
A filler is provided at a position to reduce a difference in relative permittivity between a region affecting the transmission characteristics of the first wiring of the differential wiring and a region affecting the transmission characteristics of the second wiring of the differential wiring. A wiring board characterized by. An insulating substrate having a glass cloth knitted with a plurality of warp yarns made of glass and a plurality of weft yarns made of glass, and a wiring board having a core layer comprising a differential wiring,
Of the first region provided between adjacent warps among the peripheral regions that affect the transmission characteristics of the differential wiring, or the second region provided between adjacent wefts of the peripheral region A wiring board comprising a filler in at least one region. The wiring board according to claim 2,
The filler is a position that reduces a relative dielectric constant difference between a region that affects the transmission characteristics of the first wiring of the differential wiring and a region that affects the transmission characteristics of the second wiring of the differential wiring. A wiring board, characterized in that it is provided on the wiring board. The wiring board according to claim 2 or 3,
The wiring board, wherein the filler is more than a filler provided in a third region that is not included in either the first region or the second region in the peripheral region. The wiring board according to claim 2 or 3,
The filler provided in the first region or the second region is surrounded by the plurality of warp yarns and the plurality of weft yarns in the peripheral region, and any of the plurality of warp yarns or the plurality of weft yarns exists. A wiring board characterized in that there are more fillers provided in the third region. The wiring board according to claim 4 or 5,
The wiring board according to claim 1, wherein the filler is provided at a position that reduces a difference between a relative dielectric constant of the first region or the second region and a relative dielectric constant of the third region. The wiring board according to any one of claims 1 to 6,
The wiring board according to claim 1, wherein the filler has a relative dielectric constant comparable to that of the glass cloth. A wiring board according to any one of claims 1 to 7,
A wiring board having an adhesive layer bonded to the core layer and including a resin. The wiring board according to claim 8, wherein
The wiring board, wherein the adhesive layer includes a second glass cloth knitted with a glass warp and a glass weft. The wiring board according to claim 9, wherein
A fourth region where either the warp or the weft of the second glass cloth is present;
The wiring having the second filler in at least one region of the fifth region surrounded by the warp yarn and the weft yarn of the second glass cloth and in which neither the warp yarn nor the weft yarn exists substrate. A wiring board according to any one of claims 2 to 10,
The wiring board according to claim 1, wherein the peripheral region is a region that is three times the wiring width of each of the wirings of the differential wiring. The wiring board according to any one of claims 1 to 11,
Either of the plurality of warp yarns or the plurality of weft yarns is a plurality of yarns provided substantially parallel to the differential wiring. The wiring board according to claim 12, wherein
A wiring board comprising a filler in a sixth region provided between the adjacent yarns in the peripheral region. The wiring board according to claim 13,
The sum of the thickness of the filler and glass cloth provided in the sixth region, and the sum of the thickness of the filler and glass cloth provided in a region not included in the sixth region of the peripheral region A wiring board, wherein a filler is provided at a position to reduce the difference. A multilayer wiring board comprising a plurality of the wiring boards according to claim 1, which are stacked.

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