JP7223356B2 - Signal transmission board and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a signal transmission board and a manufacturing method thereof.

Conventionally, there have been proposed various techniques related to an interposer that relays a motherboard and an IC chip that have different terminal pitches. For example, Patent Literature 1 discloses an interposer having a through-electrode penetrating through a glass substrate from a first surface to a second surface. According to the interposer, the signal layer on the first surface is electrically connected to the signal layer on the first surface, the signal layer on the second surface, and the through electrodes electrically connecting the signal layers. Signals can be transmitted between the connected IC chips and a motherboard electrically connected to the signal layer on the second side.

JP 2014-139963 A

In order to efficiently transmit signals between the motherboard and the IC chip via the interposer with little loss, it is desirable to match the impedance between the signal layer on the first surface and the signal layer on the second surface. . As a technique for matching the impedance, it is conceivable to adjust the thickness of the insulating layer on the first surface and the thickness of the insulating layer on the second surface.

However, even if the thickness of the insulating layer is adjusted to match the impedance, the stress acting on the insulating layer on the first surface causes stress on the first surface side acting on the substrate from the first surface side and stress on the second surface side. It is difficult to balance the stress acting on the upper insulating layer with the stress acting on the substrate from the second surface side on the second surface side. Further, it is difficult to balance the stress on the first surface side and the stress on the second surface side, which may cause the substrate to warp.

The present disclosure has been made in consideration of the above points, and aims to provide a signal transmission board and a method of manufacturing the same that can achieve both improvement in signal transmission efficiency and suppression of board warpage. do.

In order to solve the above problems, in one aspect of the present disclosure,
a substrate having a first side and a second side opposite the first side;
a first signal layer located on the first surface;
a first insulating layer located on the first signal layer;
a first ground layer located on the first insulating layer;
a second signal layer located on the second surface, electrically connected to the first signal layer, and having a dimension in the width direction intersecting the signal transmission direction that is larger than that of the first signal layer;
a second insulating layer located on the second signal layer and having a larger dimension in the thickness direction intersecting the first surface and a smaller elastic modulus than the first insulating layer;
and a second ground layer located on the second insulating layer.

The difference between the product of the dimension in the thickness direction and the elastic modulus of the first insulating layer and the product of the dimension in the thickness direction and the elastic modulus of the second insulating layer is the dimension in the thickness direction of the second insulating layer. It may have a ratio below the threshold to the product with the elastic modulus.

The threshold may be 15%.

The difference between the product of the coefficient of thermal expansion, the dimension in the thickness direction, and the elastic modulus of the first insulating layer and the product of the coefficient of thermal expansion, the dimension in the thickness direction, and the elastic modulus of the second insulating layer is the second It may have a ratio equal to or less than a threshold with respect to the product of the coefficient of thermal expansion, the dimension in the thickness direction, and the elastic modulus of the insulating layer.

at least one third insulating layer positioned between the first surface and the first signal layer and/or on the first ground layer;
at least one fourth insulating layer positioned between the second surface and the second signal layer and/or on the second ground layer;
The sum of the product of the dimension in the thickness direction and the elastic modulus of the first insulating layer and the product of the dimension in the thickness direction and the elastic modulus of the third insulating layer, and the dimension in the thickness direction and the elasticity of the second insulating layer The difference between the product of the modulus and the sum of the product of the dimension in the thickness direction of the fourth insulating layer and the elastic modulus is the product of the dimension in the thickness direction of the second insulating layer and the elastic modulus and the fourth insulating layer. It may have a ratio equal to or less than a threshold to the sum of the product of the dimension in the thickness direction of the layer and the modulus of elasticity.

A through electrode may be further provided which penetrates the substrate from the first surface to the second surface and is electrically connected to the first signal layer and the second signal layer.

a third ground layer located on the first surface and adjacent to the first signal layer in the width direction;
A fourth ground layer located on the second surface and adjacent to the second signal layer in the width direction may further be provided.

A capacitor electrically connected to the first signal layer on the first surface or electrically connected to the second signal layer on the second surface may be further provided.

The substrate may contain glass.

It may be mountable on a wiring board on the second surface side, and an integrated circuit may be mountable on the first surface.

In another aspect of the present disclosure,
providing a substrate having a first side and a second side opposite the first side;
forming a first signal layer on the first surface;
forming a first insulating layer on the first signal layer;
forming a first ground layer on the first insulating layer;
forming on the second surface a second signal layer that is electrically connected to the first signal layer and has a larger dimension in the width direction intersecting the signal transmission direction than the first signal layer;
forming on the second signal layer a second insulating layer having a larger dimension in the thickness direction intersecting the first surface and a smaller elastic modulus than the first insulating layer;
and forming a second ground layer on the second insulating layer.

forming the first insulating layer includes thermally curing the first insulating layer at a first temperature;
The step of forming the second insulating layer includes thermally curing the second insulating layer at the first temperature when thermally curing the first insulating layer,
The product of the coefficient of thermal expansion of the first insulating layer, the temperature change with respect to the first temperature, the dimension in the thickness direction, and the modulus of elasticity, at least in the temperature range from the first temperature to the second temperature after thermosetting. , the difference between the coefficient of thermal expansion of the second insulating layer and the temperature change with respect to the first temperature and the product of the dimension in the thickness direction and the elastic modulus is the coefficient of thermal expansion of the second insulating layer and the first temperature may have a ratio equal to or less than a threshold with respect to the product of the temperature change with respect to and the dimension in the thickness direction and the elastic modulus.

According to the present disclosure, it is possible to achieve both improvement in signal transmission efficiency and suppression of substrate warpage.

3 is a cross-sectional view showing the signal transmission board according to the embodiment; FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1 showing the signal transmission board according to the present embodiment; FIG. 2 is a cross-sectional view taken along line III-III of FIG. 1 showing the signal transmission board according to the present embodiment; FIG. 4A to 4C are cross-sectional views showing the method of manufacturing the signal transmission board according to the present embodiment; FIG. 5 is a cross-sectional view showing the method for manufacturing the signal transmission board according to the embodiment following FIG. 4 ; FIG. 6 is a cross-sectional view showing the method of manufacturing the signal transmission board according to the embodiment following FIG. 5 ; FIG. 7 is a cross-sectional view showing the method of manufacturing the signal transmission board according to the embodiment following FIG. 6 ; FIG. 8 is a cross-sectional view showing the method of manufacturing the signal transmission board according to the embodiment following FIG. 7; FIG. 9 is a cross-sectional view showing the method of manufacturing the signal transmission board according to the embodiment following FIG. 8 ; FIG. 10 is a cross-sectional view showing the method of manufacturing the signal transmission board according to the embodiment following FIG. 9; FIG. 11 is a cross-sectional view showing the method of manufacturing the signal transmission board according to the embodiment following FIG. 10 ; FIG. 12 is a cross-sectional view showing the method of manufacturing the signal transmission board according to the embodiment following FIG. 11; FIG. 10 is a diagram showing a correspondence relationship between temperature, stress of the first insulating layer according to the temperature, and a parameter correlated with the stress in an experimental example of the signal transmission board according to the present embodiment; FIG. 10 is a diagram showing a correspondence relationship between temperature, stress of a second insulating layer according to the temperature, and a parameter correlated with the stress in an experimental example of the signal transmission board according to the present embodiment; FIG. 5 is a perspective view of an indenter that can be used to measure the indentation elastic modulus that correlates with the stress of the first insulating layer and the second insulating layer in the experimental example of the signal transmission board according to the present embodiment. FIG. 5 is a cross-sectional view showing a measurement example of the indentation modulus of elasticity of the first insulating layer and the second insulating layer in an experimental example of the signal transmission board according to the present embodiment; 5 is a graph showing a measurement example of indentation elastic moduli of a first insulating layer and a second insulating layer in an experimental example of the signal transmission board according to the present embodiment; FIG. 10 is a cross-sectional view of the signal layer side on the first surface showing the signal transmission board according to the first modification of the embodiment; FIG. 10 is a cross-sectional view of the signal layer side on the second surface showing the signal transmission board according to the first modification of the embodiment; FIG. 11 is a cross-sectional view of the signal layer side on the first surface showing a signal transmission board according to a second modification of the embodiment; FIG. 11 is a cross-sectional view of the signal layer side on the second surface showing the signal transmission board according to the second modification of the embodiment; FIG. 11 is a cross-sectional view showing a signal transmission board according to a third modification of the embodiment; FIG. 3 is a diagram showing an example of a product on which a signal transmission board is mounted;

Hereinafter, the configuration of the signal transmission board and the method of manufacturing the same according to the embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments shown below are examples of the embodiments of the present disclosure, and the present disclosure should not be construed as being limited to these embodiments. Also, in this specification, terms such as "substrate", "base material", "sheet" and "film" are not to be distinguished from each other based only on the difference in designation. For example, "substrate" and "base material" are concepts that include members that can be called sheets and films. Furthermore, terms used herein to specify shapes and geometric conditions and their degrees, such as terms such as "parallel" and "perpendicular", length and angle values, etc., are bound by strict meanings. However, it is interpreted to include the extent to which similar functions can be expected. In addition, in the drawings referred to in this embodiment, the same reference numerals or similar reference numerals may be assigned to the same portions or portions having similar functions, and repeated description thereof may be omitted. Also, the dimensional ratios in the drawings may differ from the actual ratios for convenience of explanation, and some of the configurations may be omitted from the drawings.

Signal transmission board 10
Embodiments of the present disclosure will be described below. First, the configuration of the signal transmission board according to this embodiment will be described. The signal transmission substrate of this embodiment can be used, for example, as an interposer substrate that transmits high frequency signals. FIG. 1 is a cross-sectional view showing a signal transmission board 10 according to this embodiment. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1 showing the signal transmission board 10 according to this embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1 showing the signal transmission board 10 according to this embodiment.

As shown in FIGS. 1 to 3, the signal transmission substrate 10 includes a substrate 12, a through electrode 22, a first wiring structure portion 30, and a second wiring structure portion 40. FIG. Each component of the signal transmission board 10 will be described below.

(substrate 12)
Substrate 12 includes a first side 13 and a second side 14 opposite first side 13 . Further, the substrate 12 is provided with a plurality of through holes 20 penetrating from the first surface 13 to the second surface 14 . FIG. 1 shows only one through hole 20 as a representative. The signal transmission board 10 can be mounted on a mother board (not shown) on the second surface 14 side, and an IC chip (not shown), that is, an integrated circuit can be mounted on the first surface 13 .

Substrate 12 includes an inorganic material having a certain insulating property. For example, the substrate 12 may be a glass substrate, a quartz substrate, a sapphire substrate, a resin substrate, a silicon substrate, a silicon carbide substrate, an alumina (Al ₂ O ₃ ) substrate, an aluminum nitride (AlN) substrate, a zirconia oxide (ZrO ₂ ) substrate, etc. Alternatively, these substrates are laminated. The substrate 12 may partially include a substrate made of a conductive material such as an aluminum substrate or a stainless steel substrate.

Examples of the glass used for the substrate 12 include alkali-free glass. Alkali-free glass is glass that does not contain alkaline components such as sodium and potassium. Alkali-free glass includes, for example, boric acid instead of an alkaline component. Alkali-free glass also contains, for example, alkaline earth metal oxides such as calcium oxide and barium oxide.

In the example shown in FIG. 1, the through hole 20 formed in the substrate 12 has a shape whose width decreases from the first surface 13 and the second surface 14 of the substrate 12 toward the central portion of the substrate 12 in the thickness direction D3. are doing. However, the shape of through-hole 20 is not particularly limited. For example, the side wall 21 of the through hole 20 may widen along the thickness direction D3. Moreover, a part of the side wall 21 may be curved.

(Through electrode 22)
The through electrode 22 is a member positioned inside the through hole 20 and having conductivity. In the present embodiment, the thickness of the through electrode 22 is smaller than the width of the through hole 20 , so there is a space inside the through hole 20 where the through electrode 22 does not exist. That is, the through electrode 22 is a so-called conformal via. In the example of FIG. 1, the space inside the through-hole 20 is filled with a first-surface first organic layer 34 and a second-surface first organic layer 42 located inside the through-electrode 22, which will be described later.

The configuration of the through electrode 22 is not particularly limited as long as the through electrode 22 has conductivity. For example, the through electrode 22 may be composed of a single conductive layer, or may include a plurality of conductive layers. Also, the through electrode 22 may include a seed layer and a plating layer that are arranged in order from the side wall 21 side of the through hole 20 to the center side. In this case, an intermediate layer may be provided between the sidewall 21 of the through hole 20 and the seed layer. As a material forming the intermediate layer, for example, titanium, titanium nitride, molybdenum, molybdenum nitride, tantalum, tantalum nitride, etc., or a laminate thereof can be used. The intermediate layer is formed, for example, by a physical film-forming method such as a vapor deposition method or a sputtering method. The intermediate layer serves, for example, to enhance the adhesion of the seed layer or plating layer to the sidewalls 21 . The intermediate layer may also play a role of suppressing the diffusion of metal elements contained in the seed layer or the plating layer into the substrate 12 through the sidewalls 21 of the through holes 20 .

(First wiring structure portion 30)
Next, the first wiring structure portion 30 will be described. The first wiring structure portion 30 has layers such as a conductive layer and an insulating layer provided on the first surface 13 side of the substrate 12 so as to configure an electrical circuit on the first surface 13 side of the substrate 12 . In the example of FIG. 1, the first wiring structure portion 30 includes a first surface first conductive layer 31, a first surface first organic layer 34 which is an example of a third insulating layer, and a first surface second conductive layer 33. , a first surface second organic layer 36 which is an example of a first insulating layer, and a first surface third conductive layer 35 .

The first wiring structure portion 30 has a strip line sandwiching the front and back of the signal line between ground planes via an insulating layer. Hereinafter, the strip line included in the first wiring structure portion 30 is also referred to as the strip line on the first surface 13 side. As shown in FIGS. 1 and 2, the strip line on the first surface 13 side includes a signal layer 331 that is an example of a first signal layer, a ground layer 311, and a ground layer 351 that is an example of the first ground layer. have

[First surface first conductive layer 31]
The first surface first conductive layer 31 is a conductive layer located on the first surface 13 of the substrate 12 . The ground layer 311 in the strip line on the first surface 13 side is composed of a part of the first surface first conductive layer 31 .

As shown in FIG. 1 , the first surface first conductive layer 31 has a seed layer 221 and a plating layer 222 . A seed layer 221 is located on the first surface 13 of the substrate 12 . A plating layer 222 is located on the seed layer 221 .

The seed layer 221 is a conductive layer that serves as a base for depositing metal ions in the plating solution and growing the plating layer 222 during the electroplating process for forming the plating layer 222 by electroplating. be. As a material for the seed layer 221, a conductive material such as copper can be used. The material of the seed layer 221 may be the same as or different from the material of the plating layer 222 . For example, the seed layer 221 may be a laminated film in which titanium and copper are laminated in order, chromium, or the like. The seed layer 221 may be formed by, for example, a sputtering method, a vapor deposition method, an electroless plating method, or the like.

The plating layer 222 is a conductive layer formed by plating. The plating layer 222 contains copper. The plating layer 222 may contain alloys of copper and metals other than copper, such as gold, silver, platinum, rhodium, tin, aluminum, nickel, and chromium, or copper and metals other than copper. may be laminated.

[Ground layer 311]
The ground layer 311 is a layer that controls the characteristic impedance of the signal layer 331 that is located on the first surface 13, is electrically connected to a reference potential such as a ground potential, and is electrically insulated from the through electrode 22. be. The ground layer 311 is positioned on the first surface 13 so as to be adjacent to the signal layer 331 with a space therebetween in a thickness direction D3 perpendicular to or intersecting the first surface 13 in a downward direction D32 in FIG. 1 and 2, the ground layer 311 faces the signal layer 331 with the first surface first organic layer 34 interposed therebetween. Ground layer 311 has a larger total area than signal layer 331 . In order to control the characteristic impedance of the signal layer 331 to a desired value, the ground layer 311 and the signal layer 331 have a predetermined distance d3 in the thickness direction D3.

[First surface first organic layer 34]
The first surface first organic layer 34 is a layer that is located on the first surface 13 or the first surface first conductive layer 31, contains an organic material, and has insulating properties.

The first surface first organic layer 34 has a dimension in the thickness direction D3 in consideration of both impedance matching of the transmission line between the first surface 13 side and the second surface 14 side and stress balance due to the insulating layer, that is, the thickness You may have h3. In addition, the first surface first organic layer 34 may have an elastic modulus in consideration of both impedance matching and stress balance. As an example, the first surface first organic layer 34 may have a thickness h3 of 10 μm and an indentation modulus of 3.70 GPa at 25° C., ie, room temperature.

The first surface first organic layer 34 may comprise an organic material having a dielectric loss tangent of 0.003 or less, preferably 0.002 or less, more preferably 0.001 or less. As an organic material for the first surface first organic layer 34, polyimide, epoxy resin, or the like can be used. By configuring the first surface first organic layer 34 using an organic material having a small dielectric loss tangent, it is possible to suppress part of the electrical signal that should pass through the signal layer 331 from passing through the first surface first organic layer 34. can do. Thereby, the band of the signal transmission board 10 can be widened to the high frequency side.

The first surface first organic layer 34 may be formed, for example, by exposure processing and development processing using a photosensitive film containing an organic material, or a liquid containing an organic material may be applied by spin coating. and dried.

[First surface second conductive layer 33]
The first-surface second conductive layer 33 is positioned on the first surface 13 so as to be adjacent to the first-surface first conductive layer 31 with a gap in the upward direction D31 of FIG. 1 in the thickness direction D3. is a layer having In the example of FIG. 1, the first surface second conductive layer 33 is located on the first surface first organic layer 34 . A signal layer 331 in the strip line on the first surface 13 side is composed of a part of the first surface second conductive layer 33 .

The thickness of the first surface second conductive layer 33 may be the same as or different from the thickness of the first surface first conductive layer 31 .

The first surface second conductive layer 33 may include a seed layer and a plated layer that are laminated in order on the first surface first organic layer 34 in the same manner as the through electrode 22 and the first surface first conductive layer 31. good. The material forming the first surface second conductive layer 33 is the same as the material forming the through electrode 22 and the first surface first conductive layer 31 .

[Signal layer 331]
The signal layer 331 is located on the first surface first organic layer 34, which is an example on the first surface 13, is electrically connected to the through electrode 22, and is a layer that transmits an electric signal such as a high frequency signal. . Examples of high-frequency signals include electrical signals of 0.1 GHz or higher. The signal layer 331 extends along the first surface 13 in the extension direction D1 of FIG. 1, which is an example of the signal transmission direction, ie, the direction perpendicular to the paper surface of FIG. In the example of FIG. 1, the signal layer 331 is electrically connected to the through electrode 22 via a portion of the first surface first conductive layer 31 at one end in the extending direction D1.

The thickness of the signal layer 331 is preferably 5 μm or more. Since the conductor resistance loss of the signal layer 331 can be reduced by setting the thickness of the signal layer 331 to 5 μm or more, the signal transmission loss can be suppressed. More preferably, the thickness of the signal layer 331 is 20 μm or less. By setting the thickness of the signal layer 331 to 20 μm or less, interfacial stress between the signal layer 331 and the first surface first organic layer 34 can be suppressed, so peeling of the signal layer 331 can be suppressed.

An IC chip having a smaller terminal pitch than the motherboard is electrically connected to the first surface 13 side. Therefore, in the signal layer 331 on the first surface 13 side, the dimension in the width direction D2 perpendicular to the extending direction D1 indicated by reference sign W1 in FIG. desirable. As an example, the wiring width W1 of the signal layer 331 may be 300 μm or less.

[First surface second organic layer 36]
The first surface second organic layer 36 is located on the first surface first organic layer 34 or the first surface second conductive layer 33, and is a layer containing an organic material and having insulating properties.

The first surface second organic layer 36 has a thickness h1 and an elastic modulus in consideration of both the impedance matching of the transmission line between the first surface 13 side and the second surface 14 side and the balance of stress due to the insulating layer. . As an example, the first surface second organic layer 36 may have a thickness h1 of 10 μm and an indentation elastic modulus of 3.70 GPa at 25°C. Thus, one of the conditions is that the first surface second organic layer 36 has a thickness h1 and an elastic modulus that take both impedance matching and stress balance into consideration. can be secured. By ensuring both impedance matching and stress balance, both improvement in signal transmission efficiency and suppression of warping of the substrate 12 can be achieved.

Similar to first surface first organic layer 34, first surface second organic layer 36 comprises an organic material having a dielectric loss tangent of 0.003 or less, preferably 0.002 or less, more preferably 0.001 or less. It's okay. As the organic material for the first surface second organic layer 36, polyimide, epoxy resin, or the like can be used. By configuring the first surface second organic layer 36 using an organic material having a small dielectric loss tangent, it is possible to suppress part of the electrical signal that should pass through the signal layer 331 from passing through the first surface second organic layer 36. can do. As a result, the band of the signal transmission board 10 can be more preferably widened to the high frequency side.

As with the first surface first organic layer 34, the first surface second organic layer 36 may be formed, for example, by exposure processing and development processing using a photosensitive film containing an organic material, or , may be formed by applying a liquid containing an organic material by spin coating and drying.

[First surface third conductive layer 35]
The first surface third conductive layer 35 is located on the first surface 13 so as to be adjacent to the first surface second conductive layer 33, that is, the signal layer 331 with a gap in the upward direction D31 in FIG. It is a layer with In the example of FIG. 1, the first surface third conductive layer 35 is located on the first surface second organic layer 36 .

The ground layer 351 in the strip line on the first surface 13 side is composed of a part of the first surface third conductive layer 35 . A portion of the first surface third conductive layer 35 other than the ground layer 351 constitutes a terminal portion 352 to which an IC chip is electrically connected. is electrically connected to

The thickness of the first surface third conductive layer 35 may be the same as or different from the thickness of the first surface first conductive layer 31 .

The first-surface third conductive layer 35 may include a seed layer and a plating layer that are laminated in order, similar to the through electrodes 22 and the first-surface first conductive layer 31 . The material forming the first surface third conductive layer 35 is the same as the material forming the through electrode 22 and the first surface first conductive layer 31 .

[Ground layer 351]
The ground layer 351 is located on the first surface second organic layer 36, is electrically connected to a reference potential such as a ground potential, and is electrically insulated from the through electrodes 22. The ground layer 351 reduces the characteristic impedance of the signal layer 331. This is the controlling layer. Ground layer 351 has a larger total area than signal layer 331 . The ground layer 351 faces the signal layer 331 in the thickness direction D3 with the first surface second organic layer 36 interposed therebetween. In order to control the characteristic impedance of the signal layer 331 to a desired value, the ground layer 351 and the signal layer 331 have a predetermined distance d1 in the thickness direction D3.

(Second wiring structure portion 40)
Next, the second wiring structure portion 40 will be described. The second wiring structure portion 40 has layers such as a conductive layer and an insulating layer provided on the second surface 14 side of the substrate 12 so as to form an electrical circuit on the second surface 14 side. In the example of FIG. 1, the second wiring structure portion 40 includes a second surface first conductive layer 41, a second surface first organic layer 42 which is an example of a fourth insulating layer, and a second surface second conductive layer 43. , a second surface second organic layer 44 which is an example of a second insulating layer, and a second surface third conductive layer 45 .

Similar to the first wiring structure portion 30, the second wiring structure portion 40 has a strip line sandwiching the front and back of the signal line with the ground plane via an insulating layer. Hereinafter, the strip line included in the second wiring structure portion 40 is also referred to as the strip line on the second surface 14 side. The strip line on the second surface 14 side is electrically connected to the strip line on the first surface 13 side via the through electrodes 22 . As shown in FIGS. 1 and 3, the strip line on the second surface 14 side includes a signal layer 431, which is an example of a second signal layer, a ground layer 411, and a ground layer 451, which is an example of a second ground layer. have

[Second surface first conductive layer 41]
The second surface first conductive layer 41 is a conductive layer located on the second surface 14 of the substrate 12 . The ground layer 411 in the strip line on the second surface 14 side is composed of a part of the second surface first conductive layer 41 .

As shown in FIG. 1 , the second surface first conductive layer 41 has a seed layer 221 and a plating layer 222 like the first surface first conductive layer 31 . A seed layer 221 is located on the second surface 14 of the substrate 12 . A plating layer 222 is located on the seed layer 221 .

[Ground layer 411]
The ground layer 411 is a layer that controls the characteristic impedance of the signal layer 431, which is located on the second surface 14, is electrically connected to a reference potential such as a ground potential, and is electrically insulated from the through electrode 22. be. Ground layer 411 has a larger total area than signal layer 431 . The ground layer 411 is positioned on the second surface 14 so as to be adjacent to the signal layer 431 with a space therebetween in the thickness direction D3 in the upper direction D31 in FIG. 1 and 3, the ground layer 411 faces the signal layer 431 with the second surface first organic layer 42 interposed therebetween. In order to control the characteristic impedance of the signal layer 431 to a desired value, the ground layer 411 and the signal layer 431 have a predetermined distance d4 in the thickness direction D3.

[Second surface first organic layer 42]
The second surface first organic layer 42 is a layer that is located on the second surface 14 or the second surface first conductive layer 41, contains an organic material, and has insulating properties.

The second surface first organic layer 42 has a thickness h4 and an elastic modulus that take into consideration both impedance matching and stress balance of the transmission line between the first surface 13 side and the second surface 14 side. good too. For example, the second surface first organic layer 42 may be thicker and have a lower elastic modulus than the first surface first organic layer 34 . In other words, the difference in the product of the thickness and the elastic modulus between the first surface first organic layer 34 and the second surface first organic layer 42 is suppressed to be equal to or less than the threshold value. As an example, the second surface first organic layer 42 may have a thickness h4 of 19 μm and an indentation elastic modulus of 2.10 GPa at 25°C.

Similar to first surface first organic layer 34, second surface first organic layer 42 comprises an organic material having a dielectric loss tangent of 0.003 or less, preferably 0.002 or less, more preferably 0.001 or less. It's okay. As the organic material of the second surface first organic layer 42, polyimide, epoxy resin, or the like can be used. By configuring the second surface first organic layer 42 using an organic material with a small dielectric loss tangent, it is possible to suppress part of the electrical signal that should pass through the signal layer 431 from passing through the second surface first organic layer 42. can do. Thereby, the band of the signal transmission board 10 can be widened to the high frequency side.

The second surface first organic layer 42 may be formed by, for example, exposure processing and development processing using a photosensitive film containing an organic material, or a liquid containing an organic material may be applied by spin coating. and dried.

[Second surface second conductive layer 43]
The second surface second conductive layer 43 is positioned on the second surface 14 so as to be adjacent to the second surface first conductive layer 41 with a gap therebetween in the downward direction D32 of FIG. 1 in the thickness direction D3. is a layer having In the example of FIG. 1, the second surface second conductive layer 43 is located on the second surface first organic layer 42 . A signal layer 431 in the strip line on the second surface 14 side is composed of a part of the second surface second conductive layer 43 .

The thickness of the second surface second conductive layer 43 may be the same as or different from the thickness of the second surface first conductive layer 41 .

The second surface second conductive layer 43 may include a seed layer and a plated layer that are laminated in order on the second surface first organic layer 42 in the same manner as the through electrodes 22 and the first surface first conductive layer 31. good. The material forming the second surface second conductive layer 43 is the same as the material forming the through electrode 22 and the first surface first conductive layer 31 .

[Signal layer 431]
The signal layer 431 is located on the second surface first organic layer 42, which is an example on the second surface 14, and is electrically connected to the signal layer 331 on the first surface 13 via the through electrode 22 to provide a signal. Together with the layer 331, it is a layer that transmits electrical signals such as high-frequency signals. The signal layer 431 extends along the first surface 13 in the extension direction D1 of FIG. In the example of FIG. 1, the signal layer 431 is electrically connected to the through electrode 22 at one end in the extending direction D1.

The thickness of the signal layer 431 is preferably 5 μm or more. Since the conductor resistance loss of the signal layer 431 can be reduced by setting the thickness of the signal layer 431 to 5 μm or more, the signal transmission loss can be suppressed. More preferably, the thickness of the signal layer 431 is 20 μm or less. By setting the thickness of the signal layer 431 to 20 μm or less, interfacial stress between the signal layer 431 and the second surface first organic layer 42 can be suppressed, so peeling of the signal layer 431 can be suppressed.

The dimension of the signal layer 431 in the width direction D2 indicated by symbol W2 in FIG. It's becoming Specifically, the wiring width W2 of the signal layer 431 is larger than the wiring width W1 of the signal layer 331 on the first surface 13 . For example, in order to match the capacitance component of the characteristic impedance between the signal layer 331 and the signal layer 331, the ratio S2/d2 between the area S2 of the signal layer 431 and the distance d2 between the signal layer 431 and the ground layer 451 is the area of the signal layer 331. It may have a predetermined proportional relationship to the ratio S1/d1 between S1 and the distance d1 between the signal layer 331 and the ground layer 351, for example, may match. The ratio S2/d4 between the area S2 of the signal layer 431 and the distance d4 between the signal layer 431 and the ground layer 411 is the ratio S1 between the area S1 of the signal layer 331 and the distance d3 between the signal layer 331 and the ground layer 311. /d3 may have a predetermined proportional relationship, for example, may coincide. Thus, one of the conditions is that the signal layer 431 has a size relationship between the wiring widths W2 and W1 in consideration of impedance matching between the signal layer 431 and the signal layer 331, thereby ensuring both impedance matching and stress balance. be able to. As a result, both the improvement in signal transmission efficiency and the suppression of warping of the substrate 12 can be achieved.

[Second surface second organic layer 44]
The second surface second organic layer 44 is located on the second surface first organic layer 42 or the second surface second conductive layer 43, and is a layer containing an organic material and having insulating properties.

As with the first surface first organic layer 34 , the first surface second organic layer 36 and the second surface first organic layer 42 , the second surface second organic layer 44 is formed between the first surface 13 side and the second surface 14 side. It has a thickness h2 and an elastic modulus in consideration of both the impedance matching of the transmission line between the sides and the stress balance.

Specifically, the second surface second organic layer 44 has a larger thickness and a smaller elastic modulus than the first surface second organic layer 36 . A low modulus of elasticity can also mean a low stiffness, ie, a softness.

Here, in this embodiment, in consideration of electrical connection with an IC chip having a narrow terminal pitch, the wiring width W1 of the signal layer 331 on the side of the first surface 13 on which the IC chip is mounted is set to the width W1 of the signal layer 331 mounted on the mother board. It is made smaller than the wiring width W2 of the signal layer 431 on the second surface 14 side. In order to match the impedance between the signal layers 331 and 431 having different wiring widths W1 and W2, the second surface second organic layer 44 is proportional to the distance d2 between the signal layer 431 having a large wiring width W2 and the ground layer 451. is made larger than the thickness h1 of the first surface second organic layer 36 which is proportional to the distance d1 between the signal layer 331 having a small wiring width W1 and the ground layer 351 . Furthermore, in order to balance the stress on the second surface 14 side due to the second surface second organic layer 44 having a large thickness and the stress on the first surface 13 side due to the first surface second organic layer 36 having a small thickness, The elastic modulus of the second surface second organic layer 44 having a large thickness is made smaller than the elastic modulus of the first surface second organic layer 36 having a small thickness. In this way, the first surface second organic layer 36 and the second surface second organic layer 44 have a thickness and elastic modulus magnitude relationship in consideration of both impedance matching and stress balance. It is possible to ensure both stress balance and stress balance. As a result, both the improvement in signal transmission efficiency and the suppression of warping of the substrate 12 can be achieved.

The second surface second organic layer 44 may have a difference in the product of the thickness and the elastic modulus of the first surface second organic layer 36 that is equal to or less than a threshold value. Specifically, the difference between the product of the thickness and the elastic modulus of the first surface second organic layer 36 and the product of the thickness and the elastic modulus of the second surface second organic layer 44 is the second surface second organic layer It may have a sub-threshold ratio to the product of 44 thickness and elastic modulus. The threshold may be 15%. As an example, the second surface second organic layer 44 may have a thickness h4 of 19 μm and an indentation elastic modulus of 2.10 GPa at 25°C. The product of the thickness and modulus of the organic layers 36,44 is proportional to the stress acting on the organic layers 36,44. Therefore, by setting the difference between the product of the thickness proportional to the stress and the elastic modulus between the first surface second organic layer 36 and the second surface second organic layer 44 to be equal to or less than the threshold value, impedance matching and stress balance can be achieved. and can be more effectively secured. As a result, it is possible to achieve both improvement in signal transmission efficiency and suppression of warping of the substrate 12 more effectively.

The second surface second organic layer 44 may have a difference in the product of the coefficient of thermal expansion, the thickness, and the elastic modulus of the first surface second organic layer 36 that is equal to or less than a threshold value. Specifically, the difference between the product of the thermal expansion coefficient, thickness and elastic modulus of the first surface second organic layer 36 and the product of the thermal expansion coefficient, thickness and elastic modulus of the second surface second organic layer 44 is , the ratio of the coefficient of thermal expansion of the second surface second organic layer 44 to the product of the thickness and the elastic modulus of the second surface may be equal to or less than a threshold. The threshold may be 15%. The product of the coefficient of thermal expansion, thickness and modulus of the organic layers 36, 44 is more precisely proportional to the stress in the organic layers 36, 44 than the product of thickness and modulus. Therefore, by setting the difference in the product of the thermal expansion coefficient, the thickness, and the elastic modulus, which is precisely proportional to the stress, between the first surface second organic layer 36 and the second surface second organic layer 44 to a threshold value or less, Both impedance matching and stress balance can be more effectively ensured. As a result, it is possible to more effectively achieve both improvement in signal transmission efficiency and suppression of warping of the substrate 12 .

The sum of the product of the thickness h1 of the first surface second organic layer 36 and the elastic modulus and the product of the thickness h3 of the first surface first organic layer 34 and the elastic modulus is the thickness of the second surface second organic layer 44 The sum of the product of h2 and the elastic modulus and the product of the thickness h4 of the second surface first organic layer 42 and the elastic modulus may have a difference equal to or less than the threshold. Specifically, the sum of the product of the thickness h1 of the first surface second organic layer 36 and the elastic modulus and the product of the thickness h3 of the first surface first organic layer 34 and the elastic modulus, and the second surface second The difference between the sum of the product of the thickness h2 of the organic layer 44 and the elastic modulus and the product of the thickness h4 of the second surface first organic layer 42 and the elastic modulus is the thickness h2 of the second surface second organic layer 44 It may have a ratio equal to or less than a threshold with respect to the sum of the product of the elastic modulus and the product of the thickness h4 of the second surface first organic layer 42 and the elastic modulus. The threshold may be 15%. The stress on the first surface 13 side involves the stress acting on each of all the organic layers 34 and 36 on the first surface 13 . Moreover, the stress acting on all the organic layers 42 and 44 on the second surface 14 is involved in the stress on the second surface 14 side. Therefore, the sum of the product of the thickness h1 of the first surface second organic layer 36 and the elastic modulus and the product of the thickness h3 of the first surface first organic layer 34 and the elastic modulus is the second surface second organic layer 44 The sum of the product of the thickness h2 and the elastic modulus of the second surface first organic layer 42 and the product of the thickness h4 of the second surface first organic layer 42 and the elastic modulus has a difference equal to or less than the threshold value, thereby further balancing the stress. can be effectively secured. As a result, it is possible to more effectively achieve both improvement in signal transmission efficiency and suppression of warping of the substrate 12 . In this way, the configuration in which the sum of the products of the thickness and the elastic modulus of the organic layers on the first surface 13 side and the second surface 14 side has a difference equal to or less than the threshold is an additional organic layer on the ground layer 351 , i.e. The same applies to the case where a third insulating layer is provided and an additional organic layer, that is, a fourth insulating layer is provided on the ground layer 451 .

Similar to the first surface first organic layer 34, the second surface second organic layer 44 comprises an organic material having a dielectric loss tangent of 0.003 or less, preferably 0.002 or less, more preferably 0.001 or less. . As the organic material of the second surface second organic layer 44, polyimide, epoxy resin, or the like can be used. By configuring the second surface second organic layer 44 using an organic material with a small dielectric loss tangent, it is possible to suppress part of the electrical signal that should pass through the signal layer 431 from passing through the second surface second organic layer 44. can do. As a result, the band of the signal transmission board 10 can be more preferably widened to the high frequency side.

As with the first surface first organic layer 34, the second surface second organic layer 44 may be formed, for example, by exposure processing and development processing using a photosensitive film containing an organic material, or , may be formed by applying a liquid containing an organic material by spin coating and drying.

[Second surface third conductive layer 45]
The second surface third conductive layer 45 is located on the first surface 13 so as to be adjacent to the second surface second conductive layer 43, ie, the signal layer 431, spaced apart in the downward direction D32 in FIG. It is a layer with In the example of FIG. 1, the second surface third conductive layer 45 is located on the second surface second organic layer 44 . The ground layer 4511 in the strip line on the second surface 14 side is composed of part of the second surface third conductive layer 45 . A portion of the second surface third conductive layer 45 other than the ground layer 451 constitutes a terminal portion 452 electrically connected to the motherboard, and the terminal portion 452 is connected to the through electrode 22 via the signal layer 431. electrically connected.

The thickness of the second surface third conductive layer 45 may be the same as or different from the thickness of the second surface first conductive layer 41 .

The second-surface third conductive layer 45 may include a seed layer and a plating layer that are laminated in order, similar to the through electrodes 22 and the first-surface first conductive layer 31 . The material forming the second surface third conductive layer 45 is the same as the material forming the through electrode 22 and the first surface first conductive layer 31 .

[Ground layer 451]
The ground layer 451 is located on the second surface second organic layer 44 , is electrically connected to a reference potential such as a ground potential, and is electrically insulated from the penetrating electrode 22 . This is the controlling layer. Ground layer 451 has a larger total area than signal layer 431 . The ground layer 451 faces the signal layer 431 with the second surface second organic layer 44 interposed therebetween. In order to control the characteristic impedance of the signal layer 431 to a desired value that matches the characteristic impedance of the signal layer 331, the ground layer 451 has a predetermined distance d2 with respect to the signal layer 431 in the thickness direction D3.

Method for Manufacturing Signal Transmission Board 10 An example of a method for manufacturing the signal transmission board 10 will be described below with reference to FIGS.

(Step of forming through hole 20)
FIG. 4 is a cross-sectional view showing a method of manufacturing the signal transmission board 10 according to this embodiment. First, the substrate 12 is prepared. Next, a resist layer is provided on at least one of the first surface 13 and the second surface 14 . After that, openings are provided in the resist layer at positions corresponding to the through holes 20 . Next, by processing the substrate 12 in the openings of the resist layer, through holes 20 can be formed in the substrate 12 as shown in FIG. As a method for processing the substrate 12, a dry etching method such as a reactive ion etching method or a deep reactive ion etching method, a wet etching method, or the like can be used.

The through holes 20 may be formed in the substrate 12 by irradiating the substrate 12 with a laser. In this case, the resist layer may not be provided. As a laser for laser processing, an excimer laser, Nd:YAG laser, femtosecond laser, or the like can be used. When an Nd:YAG laser is employed, a fundamental wave with a wavelength of 1064 nm, a second harmonic with a wavelength of 532 nm, a third harmonic with a wavelength of 355 nm, or the like can be used.

Alternatively, laser irradiation and wet etching can be combined as appropriate. Specifically, first, an altered layer is formed in a region of the substrate 12 where the through hole 20 is to be formed by laser irradiation. Subsequently, the substrate 12 is immersed in hydrogen fluoride or the like to etch the altered layer. Through holes 20 can thus be formed in the substrate 12 . Alternatively, the through holes 20 may be formed in the substrate 12 by blasting the substrate 12 with an abrasive.

By processing the substrate 12 from both the first surface 13 side and the second surface 14 side, a through hole 20 having a shape whose width decreases toward the central portion in the thickness direction of the substrate 12 shown in FIG. 4 is formed. can do.

(Process of Forming Penetrating Electrode 22, First Surface First Conductive Layer 31, and Second Surface First Conductive Layer 41)
5A to 5D are cross-sectional views showing the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After forming the through hole 20, the through electrode 22 is formed on the side wall 21 of the through hole 20, as shown in FIG. Specifically, the seed layer 221 is formed on the first surface 13, the second surface 14, and the sidewalls 21 of the substrate 12 by sputtering, vapor deposition, electroless plating, or the like.

FIG. 6 is a cross-sectional view showing the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After forming the seed layer 221, a resist layer 37 is partially formed on the seed layer 221 as shown in FIG.

FIG. 7 is a cross-sectional view showing the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After forming the resist layer 37, as shown in FIG. 7, a plating layer 222 is formed on the seed layer 221 not covered with the resist layer 37 by electroplating using the resist layer 37 as a mask.

FIG. 8 is a cross-sectional view showing the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After forming the plating layer 222, the resist layer 37 is removed as shown in FIG.

9A to 9D are cross-sectional views showing the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After removing the resist layer 37, as shown in FIG. 9, the portion of the seed layer 221 where the resist layer 37 was formed is removed by wet etching. Thereby, the through electrode 22, the first surface first conductive layer 31 including the ground layer 311, and the second surface first conductive layer 41 including the ground layer 411 can be formed. Note that a step of annealing the plating layer 222 may be performed.

(Step of Forming First Surface First Organic Layer 34 and Second Surface First Organic Layer 42)
10A and 10B are cross-sectional views showing the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After forming the penetrating electrode 22, the first surface first conductive layer 31 and the second surface first conductive layer 41, as shown in FIG. A first surface first organic layer 34 is formed. Further, as shown in FIG. 10 , the second surface first organic layer 42 is formed on the second surface 14 or the ground layer 411 . The first surface first organic layer 34 and the second surface first organic layer 42 may be formed, for example, by exposure processing and development processing using a photosensitive film containing an organic material, or may be formed by using a photosensitive film containing an organic material. It may also be formed by applying a liquid to the layer by spin coating and drying the layer. At this time, the thickness h4 of the second surface first organic layer 42 is made larger than the thickness h3 of the first surface first organic layer 34, and the elastic modulus of the second surface first organic layer 42 is set to It may be less than the modulus of elasticity of 34.

(Step of Forming First Surface Second Conductive Layer 33 and Second Surface Second Conductive Layer 43)
11A to 11D are cross-sectional views showing the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After forming the first surface first organic layer 34 and the second surface first organic layer 42, as shown in FIG. A conductive layer 33 is formed. Further, as shown in FIG. 11, the second surface second conductive layer 43 including the signal layer 431 is formed on the second surface first organic layer 42 . The first-surface second conductive layer 33 and the second-surface second conductive layer 43 are formed by photolithography using the resist layer 37 as a mask, similarly to the first-surface first conductive layer 31 and the second-surface first conductive layer 41. It may be formed by patterning the seed layer 221 and the plating layer 222 . At this time, the wiring width W2 of the signal layer 431 shown in FIG. 3 is made larger than the wiring width W1 of the signal layer 331 shown in FIG.

(Step of Forming First Surface Second Organic Layer 36 and Second Surface Second Organic Layer 44)
12A and 12B are cross-sectional views showing the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After forming the first surface second conductive layer 33 and the second surface second conductive layer 43, as shown in FIG. A second organic layer 36 is formed on one surface. Further, as shown in FIG. 12, a second surface second organic layer 44 is formed on the second surface first organic layer 42 or the second surface second conductive layer 43 . The first surface second organic layer 36 and the second surface second organic layer 44 may be formed, for example, by exposure processing and development processing using a photosensitive film containing an organic material, or may be formed by using a photosensitive film containing an organic material. It may also be formed by applying a liquid to the layer by spin coating and drying the layer.

At this time, the thickness h2 of the second surface second organic layer 44 is made larger than the thickness h1 of the first surface second organic layer 36, and the elastic modulus of the second surface second organic layer 44 is set to The modulus of elasticity of 36 or less. For example, the second surface second organic layer 44 is formed so that the difference in the product of the thickness and the elastic modulus from the first surface second organic layer 36 is equal to or less than the threshold value.

After forming the first surface second organic layer 36 and the second surface second organic layer 44, the first surface third conductive layer 35 is formed on the first surface second organic layer 36, and the second surface second organic layer 36 is formed. By forming the second surface third conductive layer 45 on the organic layer 44, the signal transmission substrate 10 shown in FIG. 1 is obtained.

(Experimental example)
Next, an experimental example of the signal transmission board 10 according to this embodiment will be described. FIG. 13 is a diagram showing a correspondence relationship between temperature, the stress of the first insulating layer according to the temperature, and parameters correlated with the stress in an experimental example of the signal transmission substrate 10 according to the present embodiment. FIG. 14 is a diagram showing a correspondence relationship between temperature, stress of the second insulating layer according to the temperature, and a parameter correlated with the stress in an experimental example of the signal transmission substrate 10 according to the present embodiment. In FIGS. 13 and 14, the numerical value including "E" is obtained by multiplying the numerical value immediately before "E" by a numerical value obtained by exponentiation with 10 as the base and the numerical value immediately after "E" as the exponent. Numeric value. For example, "6.01E+05" in FIG. 13 is 6.01×10 ⁵ .

In the experimental example, a sample simulating the signal transmission substrate 10 of FIG. A sample was prepared, and the stress balance between the first insulating layer and the second insulating layer was evaluated for this sample. As shown in FIG. 13, the first insulating layer was made of PN, a photosensitive polyimide coating agent manufactured by Toray Industries, Inc., and had a thickness of 10 μm. As shown in FIG. 14, the second insulating layer was made of LPA, a photosensitive polyimide adhesive sheet manufactured by Toray Industries, Inc., and had a thickness of 19 μm.

As shown in FIGS. 13 and 14, the cure temperature, ie, thermosetting temperature, of the first insulating layer and the second insulating layer are both 200.degree.

As shown in FIGS. 13 and 14, the difference in the product of the indentation elastic modulus and thickness between the first insulating layer and the second insulating layer was 15% or less at temperatures below the curing temperature. For example, at room temperature of 25° C., the product of the indentation elastic modulus and the thickness of the first insulating layer is 37, whereas the product of the indentation elastic modulus and the thickness of the second insulating layer is 39.9. rice field. Therefore, at 25° C., the difference in the product of the indentation elastic modulus and the thickness between the first insulating layer and the second insulating layer is 2.9. By dividing this difference 2.9 by the product of the indentation elastic modulus and thickness of the second insulating layer 39.9 and multiplying by 100, the percentage of the difference 2.9 is 7.27%, which is 15% or less. sought.

Further, as shown in FIGS. 13 and 14, the first insulating layer and the second insulating layer are heated from the curing temperature of 200° C., which is an example of the first temperature, to the room temperature of 25° C., which is an example of the second temperature after curing. , the ratio of the difference of the product α×ΔT×E×h of the coefficient of thermal expansion α, the temperature change ΔT with respect to the curing temperature, the elastic modulus E, and the thickness h is {(4.08E+05−3 .84E+05)/3.84+E05}×100 gives 6.25%. The denominator of the ratio is the product of the thermal expansion coefficient α, the temperature change ΔT, the elastic modulus E, and the thickness h of the second insulating layer. Also, α×ΔT×E is the stress acting on the first and second insulating layers according to the temperature change from the curing temperature. The stress at the cure temperature is zero. The ratio of 6.25% obtained from FIGS. 13 and 14 is a sufficiently low figure when the ratio threshold is set at 15%.

According to an experimental example, by setting the difference in the product of the elastic modulus and the thickness between the first insulating layer and the second insulating layer to 15% or less, the stress on the first surface 13 side and the stress on the second surface 14 side can be reduced. It can be seen that the difference from the stress of can be sufficiently suppressed. In other words, according to the experimental example, it can be seen that warping of the substrate 12 during the cooling period after the curing process can be effectively suppressed.

FIG. 15 is a perspective view of an indenter I that can be used to measure the indentation elastic modulus that correlates with the stress of the first insulating layer and the second insulating layer in an experimental example of the signal transmission board 10 according to this embodiment. FIG. 16 is a cross-sectional view showing a measurement example of the indentation elastic modulus of the first insulating layer and the second insulating layer in an experimental example of the signal transmission board 10 according to this embodiment. FIG. 17 is a graph showing a measurement example of the indentation elastic modulus of the first insulating layer and the second insulating layer in an experimental example of the signal transmission board 10 according to this embodiment. In FIG. 17, the horizontal axis indicates the indentation depth of the indenter I, and the vertical axis indicates the load applied by the indenter I to the first and second insulating layers. Hereinafter, the first insulating layer and the second insulating layer are also simply referred to as insulating layers.

The indentation modulus shown in FIGS. 13 and 14 can be measured by a nanoindentation test using a Berkovich-type indenter I shown in FIG. In the indenter I shown in FIG. 15, the apex angle of the pyramid surface is 115°. As shown in FIG. 16, in the nanoindentation test, an indenter I attached to a transducer is pushed into an insulating layer placed on a stage while applying a load with the transducer. As shown in FIG. 17, the load applied from the indenter I to the insulating layer increases following a quadratic load curve A as the indentation depth h of the indenter I increases. Further, as shown in FIG. 16, the surface of the insulating layer is deformed from the initial surface to the surface when the load is applied due to the load of the pressing of the indenter I. As shown in FIG. This deformation is due to both elastic and plastic deformation. As shown in FIGS. 16 and 17, when the indentation is completed, the indentation depth of the indenter I reaches the maximum value h _max and the load also reaches the maximum value P _max . After the pressing of the indenter I is completed, the indenter I is moved in the direction opposite to the pressing direction. As a result, as shown in FIG. 17, the load applied from the indenter I to the insulating layer decreases along a quadratic load-unload curve B steeper than the load-load curve A. As shown in FIG. Further, as shown in FIG. 16, the surface of the insulating layer is deformed from the surface when the load is applied to the surface after the load is removed due to the elastic recovery accompanying the unloading of the indenter I. In addition, the surface after unloading presents deformation traces that are more concave than the initial surface due to the influence of plastic deformation during load application. In Figures 16 and 17, the surface depth after unloading is _hf .

In the above nanoindentation test, the indentation elastic modulus _EIT of the insulating layer can be obtained by the following equation.
E _IT ={1−(V _S ) ² }/[(1/E _r )−{1−(V _i ) ² }/E _i ] (1) where V _S is insulation Poisson's ratio of the layer. V _i is the Poisson's ratio of the indenter I; E _i is the elastic modulus of the indenter I; E _r is the reduced elastic modulus of the push contact.

The reduced elastic modulus E _r of the push contact in Equation (1) can be obtained from the following equation.
E _r =π ^1/2 /2CA _p ^1/2 (2) where C is the _slope dP/ is dh. A _p is the projected area of contact between the indenter I and the insulating layer.

A _p in Equation (2) can be obtained by the following equation.
A _p =23.96×{h _max −ε(h _max −h _C )} (3) However, in Equation (3), h _max is the previously described maximum indentation depth. ε is a correction factor due to the geometry of the indenter I, which is 0.75 for a diamond Vickers indenter. _hC is the intersection of the tangent line of the load-unloading curve B at the maximum load value _Pmax described above and the horizontal axis of FIG.

The effects brought about by this embodiment will be described below.

In the signal transmission board 10 of this embodiment, the width dimension W2 of the signal layer 431 on the second surface 14 is larger than the width dimension W1 of the signal layer 331 on the first surface 13 . In addition, the second surface second organic layer 44 has a larger thickness and a smaller elastic modulus than the first surface second organic layer 36 .

If only the impedance matching between the first surface 13 side and the second surface 14 side is considered, the thickness of the second surface second organic layer 44 is simply made larger than the thickness of the first surface second organic layer 36. , the stress on the second surface 14 side due to the second surface second organic layer 44 is greater than the stress on the first surface 13 side due to the first surface second organic layer 36, and the stress on the second surface 14 is large. There is a possibility that the substrate 12 may warp toward the side. On the other hand, in the present embodiment, the elastic modulus of the second surface second organic layer 44 having a large thickness is made smaller than that of the first surface second organic layer 36 having a small thickness, so that the first surface 13 Both impedance matching and stress balance can be ensured between the side and the second surface 14 side. As a result, both the improvement in signal transmission efficiency and the suppression of warping of the substrate 12 can be achieved.

Further, in the present embodiment, improvement in signal transmission efficiency and suppression of warpage of the substrate 12 can be realized in the strip line, which has superior noise characteristics compared to the coplanar line.

(First modification)
Next, a first modified example in which the first-surface second conductive layer 33 and the second-surface second conductive layer 43 form a coplanar line will be described. FIG. 18 is a cross-sectional view of the signal layer 331 side on the first surface 13 showing the signal transmission board 10 according to the first modification of the present embodiment. FIG. 18 corresponds positionally to the cross-sectional view of FIG. FIG. 19 is a cross-sectional view of the signal layer 431 side on the second surface 14 showing the signal transmission board 10 according to the first modification of the present embodiment. FIG. 19 corresponds positionally to the cross-sectional view of FIG.

1 to 17, the first surface second conductive layer 33 constitutes a strip line on the first surface 13 side between the first surface first conductive layer 31 and the first surface third conductive layer 35, An example has been described in which the second surface second conductive layer 43 constitutes the strip line on the second surface 14 side between the second surface first conductive layer 41 and the second surface third conductive layer 45 .

On the other hand, in the first modified example, the first surface second conductive layer 33 forms a coplanar line on the first surface 13 side, and the second surface second conductive layer 43 forms a coplanar line on the second surface 14 side. configure the line.

Specifically, as shown in FIG. 18, the first surface second conductive layer 33 includes a signal layer 331 and, as an example of a third ground layer, a ground adjacent to the signal layer 331 with a gap in the width direction D2. and layer 332 . As shown in FIG. 19, the second surface second conductive layer 43 includes a signal layer 431 and a ground layer 432, which is an example of a fourth ground layer, adjacent to the signal layer 431 with an interval in the width direction D2. have

According to the first modification, even in the coplanar line, the wiring width W2 of the signal layer 431 on the second surface 14 is larger than the wiring width W1 of the signal layer 331 on the first surface 13, and Since the two organic layers 44 have a greater thickness and a smaller elastic modulus than the first surface second organic layer 36, both impedance matching and stress balance between the first surface 13 side and the second surface 14 side are achieved. can be ensured. Accordingly, it is possible to achieve both improvement in signal transmission efficiency and suppression of warping of the substrate 12 .

(Second modification)
Next, a second modification having a differential transmission line that transmits one data using two signal lines will be described. FIG. 20 is a cross-sectional view of the signal layer 331 side on the first surface 13 showing the signal transmission board 10 according to the second modification of the present embodiment. FIG. 20 corresponds positionally to the cross-sectional view of FIG. FIG. 21 is a cross-sectional view of the signal layer 431 side on the second surface 14 showing the signal transmission board 10 according to the second modification of the present embodiment. FIG. 21 corresponds positionally to the cross-sectional view of FIG.

So far, an example of the signal transmission board 10 having a single-ended coplanar line or strip line for transmitting one data through one signal line has been described. On the other hand, the signal transmission board 10 of the second modification has differential transmission lines.

Specifically, as shown in FIG. 20, the first-surface second conductive layer 33 includes two signal layers 331a and 331b spaced apart in the width direction D2, and two signal layers 331a and 331b. and a ground layer 332 spaced outward in the width direction D2. The two signal layers 331a and 331b divide and transmit one electrical signal. As shown in FIG. 21, the second surface second conductive layer 43 includes two signal layers 431a and 431b spaced apart in the width direction D2 and two signal layers 431a and 431b in the width direction D2. and an outwardly spaced ground layer 432 . The two signal layers 431a and 431b are electrically connected to the two signal layers 331a and 331b via the through electrodes 22, respectively. The two signal layers 431a and 431b transmit the same electrical signals as the electrical signals transmitted by the two signal layers 331a and 331b respectively.

According to the second modification, a signal waveform can be formed with a small voltage by having differential transmission lines. Since the signal waveform can be formed with a small voltage, the rise time of the signal can be shortened. Since the rise time of the signal can be shortened, high-frequency electrical signals can be transmitted appropriately compared to the single-ended method. According to the second modification, even in the differential transmission line, the wiring width W2 of the signal layers 431a and 431b on the second surface 14 is equal to the wiring width of the signal layers 331a and 331b on the first surface 13. W1, and the second surface second organic layer 44 has a larger thickness and a smaller elastic modulus than the first surface second organic layer 36, so that , both impedance matching and stress balance can be ensured. Accordingly, it is possible to achieve both improvement in signal transmission efficiency and suppression of warping of the substrate 12 .

(Third modification)
Next, a third modified example having a capacitor will be described. FIG. 22 is a cross-sectional view showing a signal transmission board 10 according to a third modified example of this embodiment.

As shown in FIG. 22 , in the third modification, a portion of the signal layer 311 is composed of the dielectric 32 located on the signal layer 311 and the first surface second conductive layer 33 located on the dielectric 32 . , constitute a capacitor 15 of MIM (Metal-Insulator-Metal) structure. Dielectric 32 contains, for example, a silicon nitride such as SiN.

The signal transmission board 10 of the present disclosure can also be applied to transmission lines other than the various transmission lines described above. For example, the signal transmission board 10 may be applied to microstrip lines.

Various modifications can be made to the above-described embodiment. Modifications will be described below with reference to the drawings as necessary. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding portions in the above-described embodiment are used for the parts that can be configured in the same manner as in the above-described embodiment, Duplicate explanations are omitted. Further, when it is clear that the effects obtained in the above-described embodiment can also be obtained in the modified example, the explanation thereof may be omitted.

Examples of Products Mounted with Conducting Electrode Substrate FIG. 23 is a diagram showing an example of a product on which the signal transmission substrate 10 according to the embodiment of the present disclosure can be mounted. The signal transmission board 10 according to the embodiment of the present disclosure can be used in various products. For example, it is installed in a notebook personal computer 110, a tablet terminal 120, a mobile phone 130, a smart phone 140, a digital video camera 150, a digital camera 160, a digital clock 170, a server 180, and the like.

10 signal transmission substrate 12 substrate 331 signal layer 34 first surface first organic layer 351 ground layer 431 signal layer 44 second surface second organic layer 451 ground layer

Claims (15)

a first signal layer;
a first insulating layer located on the first signal layer;
a first ground layer located on the first insulating layer;
located on the side opposite to the first insulating layer and the first ground layer with respect to the first signal layer, electrically connected to the first signal layer, and crossing the first signal layer in the signal transmission direction a second signal layer having a large dimension in the width direction;
a second insulating layer positioned on the second signal layer and having a larger dimension in a thickness direction intersecting the signal transmission direction and the width direction and a smaller elastic modulus than the first insulating layer;
and a second ground layer located on the second insulating layer. a first signal layer;
a first ground layer located on the first signal layer;
at least one third insulating layer positioned on at least one side of the first signal layer opposite to the first ground layer and on the first ground layer;
positioned away from the third insulating layer on the side opposite to the first ground layer with respect to the first signal layer, electrically connected to the first signal layer, and in a signal transmission direction from the first signal layer; a second signal layer having a large dimension in the width direction intersecting the
a second ground layer located on the second signal layer;
A thickness located on at least one of the side opposite to the second ground layer and on the second ground layer with respect to the second signal layer and crossing the signal transmission direction and the width direction more than the third insulating layer and at least one fourth insulating layer having a large directional dimension and a small elastic modulus. The difference between the product of the dimension in the thickness direction and the elastic modulus of the first insulating layer and the product of the dimension in the thickness direction and the elastic modulus of the second insulating layer is the dimension in the thickness direction of the second insulating layer. 2. The signal transmission line of claim 1, having a ratio of the product with the modulus of elasticity that is less than or equal to a threshold. 4. The signal transmission line according to claim 3, wherein said threshold is 15%. The difference between the product of the coefficient of thermal expansion, the dimension in the thickness direction, and the elastic modulus of the first insulating layer and the product of the coefficient of thermal expansion, the dimension in the thickness direction, and the elastic modulus of the second insulating layer is the second 5. The signal transmission line according to claim 3, wherein the ratio of the product of the coefficient of thermal expansion, the dimension in the thickness direction, and the modulus of elasticity of the insulating layer is equal to or less than a threshold. at least one third insulating layer positioned on at least one side of the first signal layer opposite to the first ground layer and on the first ground layer;
at least one fourth insulating layer positioned on at least one side of the second signal layer opposite to the second ground layer and on the second ground layer;
The sum of the product of the dimension in the thickness direction and the elastic modulus of the first insulating layer and the product of the dimension in the thickness direction and the elastic modulus of the third insulating layer, and the dimension in the thickness direction and the elasticity of the second insulating layer The difference between the product of the modulus and the sum of the product of the dimension in the thickness direction of the fourth insulating layer and the elastic modulus is the product of the dimension in the thickness direction of the second insulating layer and the elastic modulus and the fourth insulating layer. 6. The signal transmission line according to any one of claims 1, 3 to 5, having a ratio equal to or less than a threshold to the sum of the product of the dimension in the thickness direction of the layer and the elastic modulus. The difference between the product of the dimension in the thickness direction and the elastic modulus of the third insulating layer and the product of the dimension in the thickness direction and the elastic modulus of the fourth insulating layer is the dimension in the thickness direction of the fourth insulating layer. 3. The signal transmission line of claim 2, having a ratio of the product with the modulus of elasticity that is less than or equal to a threshold. 8. The signal transmission line according to claim 7, wherein said threshold is 15%. 9. The signal transmission line according to claim 1, further comprising through electrodes electrically connected to said first signal layer and said second signal layer. a third ground layer adjacent to the first signal layer in the width direction;
10. The signal transmission line according to claim 1, further comprising a fourth ground layer adjacent to said second signal layer in said width direction. 11. The signal transmission line according to any one of claims 1 to 10, further comprising a capacitor electrically connected to said first signal layer or electrically connected to said second signal layer. 12. The signal transmission line according to claim 1, wherein said second signal layer side can be mounted on a wiring board, and said first signal layer side can be mounted with an integrated circuit. forming a first signal layer;
forming a first insulating layer on the first signal layer;
forming a first ground layer on the first insulating layer;
A first ground layer is electrically connected to the first signal layer on the side opposite to the first ground layer with respect to the first signal layer, and has a larger dimension in the width direction intersecting the signal transmission direction than the first signal layer. forming two signal layers;
forming, on the second signal layer, a second insulating layer having a larger dimension in a thickness direction intersecting the signal transmission direction and the width direction and a smaller elastic modulus than the first insulating layer;
and forming a second ground layer on the second insulating layer. forming the first insulating layer includes thermally curing the first insulating layer at a first temperature;
The step of forming the second insulating layer includes thermally curing the second insulating layer at the first temperature when thermally curing the first insulating layer,
The product of the coefficient of thermal expansion of the first insulating layer, the temperature change with respect to the first temperature, the dimension in the thickness direction, and the modulus of elasticity, at least in the temperature range from the first temperature to the second temperature after thermosetting. , the difference between the coefficient of thermal expansion of the second insulating layer and the temperature change with respect to the first temperature and the product of the dimension in the thickness direction and the elastic modulus is the coefficient of thermal expansion of the second insulating layer and the first temperature 14. The method of manufacturing a signal transmission line according to claim 13, wherein a ratio of a product of a temperature change with respect to the thickness direction, the dimension in the thickness direction, and the elastic modulus is equal to or less than a threshold. forming a first signal layer;
forming a first ground layer on the first signal layer;
forming at least one third insulating layer on at least one side of the first signal layer opposite to the first ground layer and on the first ground layer;
A first ground layer is electrically connected to the first signal layer on the side opposite to the first ground layer with respect to the first signal layer, and has a larger dimension in the width direction intersecting the signal transmission direction than the first signal layer. forming two signal layers separate from the third insulating layer;
forming a second ground layer on the second signal layer;
A dimension in a thickness direction intersecting the signal transmission direction and the width direction from the third insulating layer on at least one of the side opposite to the second ground layer and on the second ground layer with respect to the second signal layer and forming at least one fourth insulating layer having a large elastic modulus and a small elastic modulus.

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