JP7037773B2 - Signal transmission board and its manufacturing method - Google Patents

Description

The present disclosure relates to a signal transmission substrate and a method for manufacturing the same.

Conventionally, various techniques related to an interposer that relays a motherboard having a different terminal pitch and an IC chip have been proposed. For example, Patent Document 1 discloses an interposer including a through electrode that penetrates a glass substrate from the first surface to the second surface. According to the interposer, the signal layer on the first surface is electrically connected to the signal layer on the first surface via the signal layer on the first surface, the signal layer on the second surface, and the through electrode that electrically connects both signal layers. A signal can be transmitted between the connected IC chip and the motherboard electrically connected to the signal layer on the second surface.

Japanese Unexamined Patent Publication No. 2014-139963

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 method of 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 the stress acting on the substrate from the first surface side and the stress on the first surface side and the second surface. 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. Further, it is difficult to balance the stress on the first surface side and the stress on the second surface side, so that there is a possibility that the substrate may be warped.

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

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

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

The threshold value may be 15%.

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

With at least one third insulating layer located between the first surface and the first signal layer and at least one on the first ground layer.
Further comprising at least one fourth insulating layer located between the second surface and the second signal layer and on at least one of the second ground layers.
The sum of the product of the thickness direction dimension and elastic modulus of the first insulating layer and the product of the thickness direction dimension and elastic modulus of the third insulating layer, and the thickness direction dimension and elasticity of the second insulating layer. The difference between the product of the rate and the product of the thickness direction dimension of the fourth insulating layer and the elastic modulus is the product of the thickness direction dimension of the second insulating layer and the elastic modulus and the fourth insulation. It may have a ratio less than or equal to the threshold value with respect to the sum of the dimension in the thickness direction of the layer and the product of the elastic modulus.

A through electrode that 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 may be further provided.

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 be further provided.

Further, 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 mounted on the wiring board on the second surface side, and an integrated circuit may be mounted on the first surface.

In another aspect of the present disclosure,
A step of preparing a substrate having a first surface and a second surface opposite to the first surface, and
The step of forming the first signal layer on the first surface and
The step of forming the first insulating layer on the first signal layer and
The step of forming the first ground layer on the first insulating layer and
A step of forming a second signal layer on the second surface, which is electrically connected to the first signal layer and has a larger width direction crossing the signal transmission direction than the first signal layer.
A step of forming a second insulating layer on the second signal layer, which intersects the first surface with a larger dimension in the thickness direction and a smaller elastic modulus than the first insulating layer.
Provided is a method for manufacturing a signal transmission board, comprising a step of forming a second ground layer on the second insulating layer.

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

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

It is sectional drawing which shows the signal transmission board by this embodiment. FIG. 2 is a sectional view taken along line II-II of FIG. 1 showing a signal transmission board according to the present embodiment. FIG. 3 is a sectional view taken along line III-III of FIG. 1 showing a signal transmission board according to the present embodiment. It is sectional drawing which shows the manufacturing method of the signal transmission board by this embodiment. FIG. 5 is a cross-sectional view showing a method of manufacturing a signal transmission board according to the present embodiment following FIG. FIG. 5 is a cross-sectional view showing a method of manufacturing a signal transmission board according to the present embodiment following FIG. FIG. 6 is a cross-sectional view showing a method of manufacturing a signal transmission board according to the present embodiment following FIG. FIG. 7 is a cross-sectional view showing a method of manufacturing a signal transmission board according to the present embodiment following FIG. 7. FIG. 8 is a cross-sectional view showing a method of manufacturing a signal transmission board according to the present embodiment following FIG. FIG. 9 is a cross-sectional view showing a method of manufacturing a signal transmission board according to the present embodiment following FIG. It is sectional drawing which shows the manufacturing method of the signal transmission board by this embodiment which follows | FIG. FIG. 11 is a cross-sectional view showing a method of manufacturing a signal transmission board according to the present embodiment following FIG. It is a figure which shows the correspondence relationship between the temperature, the stress of the 1st insulating layer corresponding to the temperature, and the parameter which correlates with the stress in the experimental example of the signal transmission substrate by this embodiment. It is a figure which shows the correspondence relationship between the temperature, the stress of the 2nd insulating layer corresponding to the temperature, and the parameter which correlates with the stress in the experimental example of the signal transmission substrate by this embodiment. FIG. 3 is a perspective view of an indenter that can be used for measuring 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 substrate according to the present embodiment. It is sectional drawing which shows the measurement example of the indentation elastic modulus of the 1st insulating layer and the 2nd insulating layer in the experimental example of the signal transmission substrate by this embodiment. It is a graph which shows the measurement example of the indentation elastic modulus of the 1st insulating layer and the 2nd insulating layer in the experimental example of the signal transmission substrate by this embodiment. It is sectional drawing of the signal layer side on the 1st surface which shows the signal transmission board by 1st modification of this Embodiment. It is sectional drawing of the signal layer side on the 2nd surface which shows the signal transmission board by 1st modification of this embodiment. It is sectional drawing of the signal layer side on the 1st surface which shows the signal transmission board by the 2nd modification of this embodiment. It is sectional drawing of the signal layer side on the 2nd surface which shows the signal transmission board by the 2nd modification of this embodiment. It is sectional drawing which shows the signal transmission board by the 3rd modification of this embodiment. It is a figure which shows the example of the product which mounts a signal transmission board.

Hereinafter, the configuration of the signal transmission board and the manufacturing method thereof according to the embodiment of the present disclosure will be described in detail with reference to the drawings. It should be noted that the embodiments shown below are examples of the embodiments of the present disclosure, and the present disclosure is not construed as being limited to these embodiments. Further, in the present specification, terms such as "board", "base material", "sheet" and "film" are not distinguished from each other based only on the difference in names. For example, "base material" and "base material" are concepts including members that can be called sheets or films. Furthermore, the terms used herein, such as "parallel" and "orthogonal", and the values of length and angle, which specify the shape and geometric conditions and their degrees, are bound by a strict meaning. Instead, the interpretation shall be made to include the range in which similar functions can be expected. Further, in the drawings referred to in the present embodiment, the same parts or parts having similar functions may be designated by the same reference numerals or similar reference numerals, and the repeated description thereof may be omitted. Further, the dimensional ratio of the drawing may differ from the actual ratio for convenience of explanation, or a part of the configuration may be omitted from the drawing.

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

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

(Board 12)
The substrate 12 includes a first surface 13 and a second surface 14 located on the opposite side of the first surface 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. In FIG. 1, only one through hole 20 is typically shown. The signal transmission board 10 can be mounted on a motherboard (not shown) on the second surface 14 side, and an IC chip, that is, an integrated circuit (not shown) can be mounted on the first surface 13.

The substrate 12 contains an inorganic material having a certain insulating property. For example, the substrate 12 includes 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 diriconia oxide (ZrO ₂ ) substrate, and the like. 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 in the substrate 12 include non-alkali glass.
Non-alkali glass is glass that does not contain alkaline components such as sodium and potassium. The non-alkali glass contains, for example, boric acid instead of the alkaline component. The non-alkali 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 in which the 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. is doing. However, the shape of the through hole 20 is not particularly limited. For example, the side wall 21 of the through hole 20 may extend along the thickness direction D3. Further, a part of the side wall 21 may be curved.

(Through Silicon Via 22)
The through electrode 22 is a member located 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 that there is a space inside the through hole 20 in which 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 the first surface first organic layer 34 and the second surface first organic layer 42, which will be described later, located inside the through electrode 22.

As long as the through electrode 22 has conductivity, the configuration of the through electrode 22 is not particularly limited. For example, the through silicon via 22 may be composed of a single layer having conductivity, or may include a plurality of layers having conductivity. Further, the through electrode 22 may include a seed layer and a plating layer arranged in order from the side wall 21 side to the center side of the through hole 20. In this case, an intermediate layer may be provided between the side wall 21 of the through hole 20 and the seed layer. As the material constituting the intermediate layer, for example, titanium, titanium nitride, molybdenum, molybdenum nitride, tantalum, tantalum nitride or the like, or a laminated material thereof can be used. The intermediate layer is formed by a physical film forming method such as a vapor deposition method or a sputtering method. The intermediate layer plays a role of enhancing the adhesion of the seed layer and the plating layer to the side wall 21, for example. Further, the intermediate layer may play a role of suppressing the diffusion of the metal element contained in the seed layer or the plating layer into the inside of the substrate 12 through the side wall 21 of the through hole 20.

(1st wiring structure part 30)
Next, the first wiring structure portion 30 will be described. The first wiring structure portion 30 has a layer such as a conductive layer or an insulating layer provided on the first surface 13 side so as to form an electric 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. It has a first surface second organic layer 36, which is an example of the first insulating layer, and a first surface third conductive layer 35.

The first wiring structure portion 30 has a strip line that sandwiches the front and back of the signal line with a ground surface via an insulating layer. Hereinafter, the strip line included in the first wiring structure portion 30 is also referred to as a 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 which is an example of the first signal layer, a ground layer 311 and a ground layer 351 which is an example of the first ground layer. Has.

[First surface, first conductive layer 31]
The first surface first conductive layer 31 is a layer having conductivity 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. The seed layer 221 is located on the first surface 13 of the substrate 12. The plating layer 222 is located on the seed layer 221.

The seed layer 221 is a conductive layer that serves as a base for growing the plating layer 222 by precipitating metal ions in the plating solution during the electrolytic plating step of forming the plating layer 222 by the electrolytic plating treatment. be. As the material of 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 the plating treatment. The plating layer 222 contains copper. The plating layer 222 may contain an alloy of copper and a metal other than copper, for example, gold, silver, platinum, rhodium, tin, aluminum, nickel, chromium, or copper and a metal other than copper. May be laminated.

[Grand layer 311]
The ground layer 311 is a layer located on the first surface 13 and electrically connected to a reference potential such as a ground potential and electrically isolated from the through electrode 22 to control the characteristic impedance of the signal layer 331. be. The ground layer 311 is located on the first surface 13 so as to be adjacent to the signal layer 331 at an interval of the lower D32 in FIG. 1 in the thickness direction D3 orthogonal to or intersecting the first surface 13. In the examples of FIGS. 1 and 2, the ground layer 311 faces the signal layer 331 so as to sandwich the first surface first organic layer 34 in between. The ground layer 311 has a total area larger than that of the signal layer 331. In order to control the characteristic impedance of the signal layer 331 to a desired value, the ground layer 311 has a predetermined distance d3 in the thickness direction D3 from the signal layer 331.

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

The first organic layer 34 has a dimension, that is, a thickness 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 the balance of stress due to the insulating layer. It may have h3. Further, the first organic layer 34 on the first surface may have an elastic modulus in consideration of both the impedance matching and the stress balance. As an example, the first surface first organic layer 34 may have a thickness h3 of 10 μm and a indentation modulus of 3.70 GPa at 25 ° C., that is, room temperature.

The first organic layer 34 on the first surface may contain 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 first organic layer 34 on the first surface, polyimide, epoxy resin, or the like can be used. By constructing the first surface first organic layer 34 using an organic material having a small dielectric loss tangent, it is possible to prevent a part of the electric signal that should pass through the signal layer 331 from passing through the first surface first organic layer 34. can do. As a result, the band of the signal transmission board 10 can be expanded to the high frequency side.

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

[First surface, second conductive layer 33]
The first surface second conductive layer 33 is located on the first surface 13 so as to be adjacent to the first surface first conductive layer 31 at intervals in the upward direction D31 of FIG. 1 in the thickness direction D3. It 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. The 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.

Similar to the through silicon via 22 and the first surface first conductive layer 31, the first surface second conductive layer 33 may include a seed layer and a plating layer sequentially laminated on the first surface first organic layer 34. good. The material constituting the first surface second conductive layer 33 is the same as the material constituting 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, and is a layer electrically connected to the through electrode 22 to transmit an electric signal such as a high frequency signal. .. Examples of the high frequency signal include an electric signal of 0.1 GHz or higher. The signal layer 331 extends along the first surface 13 in the stretching direction D1 of FIG. 1, which is an example of the signal transmission direction, that is, in 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 at one end in the stretching direction D1 via a part of the first surface first conductive layer 31.

The thickness of the signal layer 331 is preferably 5 μm or more. By setting the thickness of the signal layer 331 to 5 μm or more, the conductor resistance loss of the signal layer 331 can be reduced, so that the signal transmission loss can be suppressed. The thickness of the signal layer 331 is more preferably 20 μm or less. By setting the thickness of the signal layer 331 to 20 μm or less, the interfacial stress between the signal layer 331 and the first organic layer 34 can be suppressed, so that the 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 of the width direction D2 orthogonal to the stretching direction D1 indicated by the reference numeral W1 in FIG. 2, that is, the wiring width W1 is small according to the terminal pitch of the IC chip. 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 a layer that is located on the first surface first organic layer 34 or on the first surface second conductive layer 33, contains an organic material, and has an insulating property.

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 stress balance due to the insulating layer. .. As an example, the first surface second organic layer 36 may have a thickness h1 of 10 μm and a indentation modulus of 3.70 GPa at 25 ° C. As described above, one of the conditions is that the first surface second organic layer 36 has a thickness h1 and an elastic modulus in consideration of both impedance matching and stress balance, and both impedance matching and stress balance are maintained. Can be secured. By ensuring both impedance matching and stress balance, it is possible to achieve both improvement in signal transmission efficiency and suppression of warpage of the substrate 12.

Similar to the first surface first organic layer 34, the first surface second organic layer 36 contains an organic material having a dielectric loss tangent of 0.003 or less, preferably 0.002 or less, more preferably 0.001 or less. But it may be. As the organic material of the first surface second organic layer 36, polyimide, epoxy resin or the like can be used. By constructing the first surface second organic layer 36 using an organic material having a small dielectric loss tangent, it is possible to prevent a part of the electric 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 expanded to the high frequency side.

Similarly to the first surface first organic layer 34, the first surface second organic layer 36 may be formed by, for example, an exposure treatment and a development treatment using a photosensitive film containing an organic material, or may be formed. , A liquid containing an organic material may be applied by spin coating and dried.

[First surface, third conductive layer 35]
The first surface third conductive layer 35 is positioned on the first surface 13 so as to be adjacent to the first surface second conductive layer 33, that is, the signal layer 331 at intervals in the upward direction D31 of FIG. It is a layer to have. 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 part of the first surface third conductive layer 35 other than the ground layer 351 constitutes a terminal portion 352 to which the IC chip is electrically connected, and the terminal portion 352 is a through electrode 22 via the signal layer 331. 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 laminated in order, similarly to the through electrode 22 and the first surface first conductive layer 31. The material constituting the first surface third conductive layer 35 is the same as the material constituting 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, and has the characteristic impedance of the signal layer 331 which is electrically connected to a reference potential such as a ground potential and electrically isolated from the through electrode 22. It is a layer to control. The ground layer 351 has a total area larger than that of the signal layer 331. The ground layer 351 faces the signal layer 331 in the thickness direction D3 so as to sandwich the first surface second organic layer 36 in between. In order to control the characteristic impedance of the signal layer 331 to a desired value, the ground layer 351 has a predetermined distance d1 in the thickness direction D3 between the ground layer 351 and the signal layer 331.

(Second wiring structure part 40)
Next, the second wiring structure unit 40 will be described. The second wiring structure portion 40 has a layer such as a conductive layer or an insulating layer provided on the second surface 14 side so as to form an electric circuit on the second surface 14 side of the substrate 12. 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. It has a second surface second organic layer 44, which is an example of the 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 that sandwiches the front and back of the signal line with the ground surface via the insulating layer. Hereinafter, the strip line included in the second wiring structure portion 40 is also referred to as a 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 electrode 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 the second signal layer, a ground layer 411, and a ground layer 451 which is an example of the second ground layer. Has.

[Second surface, first conductive layer 41]
The second surface first conductive layer 41 is a layer having conductivity 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, similarly to the first surface first conductive layer 31. The seed layer 221 is located on the second surface 14 of the substrate 12. The plating layer 222 is located on the seed layer 221.

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

[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 an insulating property.

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

Similar to the first surface first organic layer 34, the second surface first organic layer 42 contains an organic material having a dielectric loss tangent of 0.003 or less, preferably 0.002 or less, more preferably 0.001 or less. But it may be. As the organic material of the second surface first organic layer 42, polyimide, epoxy resin or the like can be used. By constructing the second surface first organic layer 42 using an organic material having a small dielectric loss tangent, it is possible to prevent a part of the electric signal that should pass through the signal layer 431 from passing through the second surface first organic layer 42. can do. As a result, the band of the signal transmission board 10 can be expanded to the high frequency side.

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

[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 at intervals in the downward direction D32 of FIG. 1 in the thickness direction D3. It 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. The 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 plating layer sequentially laminated on the second surface first organic layer 42, similarly to the through electrode 22 and the first surface first conductive layer 31. good. The material constituting the second surface second conductive layer 43 is the same as the material constituting 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. It is a layer that transmits an electric signal such as a high frequency signal together with the layer 331. The signal layer 431 extends in the stretching direction D1 of FIG. 1 along the first surface 13. In the example of FIG. 1, the signal layer 431 is electrically connected to the through electrode 22 at one end in the stretching direction D1.

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

In FIG. 3, the dimension of the signal layer 431 in the width direction D2 indicated by the reference numeral W2, that is, the wiring width W2 is the wiring width W2 in consideration of impedance matching of the transmission line between the first surface 13 side and the second surface 14 side. It has become. 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 with the signal layer 331, the ratio S2 / d2 of 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 with respect to the ratio S1 / d1 of the distance d1 between S1 and the signal layer 331 and the ground layer 351. For example, they may match. Further, the ratio S2 / d4 of 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 of the area S1 of the signal layer 331 and the distance d3 between the signal layer 331 and the ground layer 311. It may have a predetermined proportional relationship with / d3, and may match, for example. As described above, one of the conditions is that the signal layer 431 has a magnitude relationship of the wiring widths W2 and W1 in consideration of impedance matching with the signal layer 331, and both impedance matching and stress balance are ensured. be able to. As a result, it is possible to achieve both improvement in signal transmission efficiency and suppression of warpage of the substrate 12.

[Second surface, second organic layer 44]
The second surface second organic layer 44 is a layer that is located on the second surface first organic layer 42 or the second surface second conductive layer 43, contains an organic material, and has an insulating property.

Similar to 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 has the first surface 13 side and the second surface 14 It has a thickness h2 and an elastic modulus in consideration of both impedance matching of the transmission line with the side and stress balance.

Specifically, the second surface second organic layer 44 has a larger thickness and a lower elastic modulus than the first surface second organic layer 36. A small elastic modulus can also mean that the rigidity is small, that is, it is soft.

Here, in the present embodiment, in consideration of the electrical connection with the IC chip having a narrow terminal pitch, the wiring width W1 of the signal layer 331 on the first surface 13 side on which the IC chip is mounted is mounted on the motherboard. It is smaller than the wiring width W2 of the signal layer 431 on the second surface 14 side. Then, 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 having a large wiring width W2 is proportional to the distance d2 between the signal layer 431 and the ground layer 451. The thickness h2 of the first surface second organic layer 36 is 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 and the ground layer 351 having a small wiring width W1. Further, 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 thickness is increased. The elastic modulus of the large second surface second organic layer 44 is made smaller than the elastic modulus of the small thickness first surface second organic layer 36. In this way, the first surface second organic layer 36 and the second surface second organic layer 44 have a magnitude relationship of thickness and elastic modulus in consideration of both impedance matching and stress balance, so that impedance matching can be achieved. Both stress balance can be ensured. As a result, it is possible to achieve both improvement in signal transmission efficiency and suppression of warpage of the substrate 12.

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

In the second surface second organic layer 44, the difference in the product of the coefficient of thermal expansion, the thickness, and the elastic modulus with respect to the first surface second organic layer 36 may be equal to or less than the threshold value. Specifically, the difference between the product of the coefficient of thermal expansion of the first surface second organic layer 36 and the thickness and the elastic modulus and the product of the coefficient of thermal expansion of the second surface second organic layer 44 and the thickness and the elastic modulus 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 may be equal to or less than the threshold value. The threshold value may be 15%. The product of the coefficient of thermal expansion of the organic layers 36 and 44, the thickness and the elastic modulus is more precisely proportional to the stress of the organic layers 36 and 44 as compared with the product of the thickness and the elastic modulus. Therefore, the difference between the product of the coefficient of thermal expansion, which is precisely proportional to the stress, and the thickness and elastic modulus between the first surface second organic layer 36 and the second surface second organic layer 44 is set to be equal to or less than the threshold value. Both impedance matching and stress balance can be secured more effectively. As a result, it is possible to more effectively achieve both improvement in signal transmission efficiency and suppression of warpage 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 difference between 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 be less than or equal to the threshold value.
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 product of the thickness h2 of the organic layer 44 and the elastic modulus and the sum of 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 less than or equal to the threshold value 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 value 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. Further, 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 product of the second surface second organic layer 44. The stress balance is further balanced by having a difference equal to or less than the threshold value with respect to the product of the thickness h2 of the above and the elastic modulus and the product of the thickness h4 of the second surface first organic layer 42 and the elastic modulus. It can be secured effectively. As a result, it is possible to more effectively achieve both improvement in signal transmission efficiency and suppression of warpage of the substrate 12. As described above, the configuration in which the sum of the products of the thickness and the elastic modulus of the organic layer on the first surface 13 side and the second surface 14 side has a difference equal to or less than the threshold value is an additional organic layer on the ground layer 351. The same may be applied when 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 contains 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 constructing the second surface second organic layer 44 using an organic material having a small dielectric loss tangent, it is possible to prevent a part of the electric 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 expanded to the high frequency side.

Similarly to the first surface first organic layer 34, the second surface second organic layer 44 may be formed by, for example, an exposure treatment and a development treatment using a photosensitive film containing an organic material, or may be formed. , A liquid containing an organic material may be applied by spin coating and dried.

[Second surface, third conductive layer 45]
The second surface third conductive layer 45 is positioned on the first surface 13 so as to be adjacent to the second surface second conductive layer 43, that is, the signal layer 431, at intervals in the downward direction D32 of FIG. It is a layer to have. 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 a part of the second surface third conductive layer 45. A part 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 connects to the through electrode 22 via the signal layer 431. It is 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 laminated in order, similarly to the through electrode 22 and the first surface first conductive layer 31. The material constituting the second surface third conductive layer 45 is the same as the material constituting 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, and has the characteristic impedance of the signal layer 431 that is electrically connected to a reference potential such as a ground potential and electrically isolated from the through electrode 22. It is a layer to control. The ground layer 451 has a total area larger than that of the signal layer 431. The ground layer 451 faces the signal layer 431 so as to sandwich the second surface second organic layer 44 in between. 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 in the thickness direction D3 from the signal layer 431.

Manufacturing Method of Signal Transmission Board 10 Hereinafter, an example of the manufacturing method of the signal transmission board 10 will be described with reference to FIGS. 4 to 17.

(Step of forming through hole 20)
FIG. 4 is a cross-sectional view showing a method of manufacturing the signal transmission substrate 10 according to the present 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, an opening is provided in the resist layer at a position corresponding to the through hole 20. Next, by processing the substrate 12 at the opening of the resist layer, a through hole 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 digging reactive ion etching method, a wet etching method, or the like can be used.

The through hole 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 the laser for laser processing, an excimer laser, an Nd: YAG laser, a femtosecond laser, or the like can be used. When the Nd: YAG laser is adopted, a fundamental wave having a wavelength of 1064 nm, a second harmonic having a wavelength of 532 nm, a third harmonic having a wavelength of 355 nm, and the like can be used.

Further, laser irradiation and wet etching can be appropriately combined. Specifically, first, the altered layer is formed in the region of the substrate 12 where the through hole 20 should be formed by laser irradiation. Subsequently, the substrate 12 is immersed in hydrogen fluoride or the like to etch the altered layer. As a result, the through hole 20 can be formed in the substrate 12. In addition, a through hole 20 may be formed in the substrate 12 by a blast treatment of spraying an abrasive on the substrate 12.

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 as shown in FIG. 4 is formed. can do.

(Steps for Forming Through Silicon Via 22, First Surface First Conductive Layer 31 and Second Surface First Conductive Layer 41)
FIG. 5 is a cross-sectional view showing a method of manufacturing the signal transmission substrate 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 side wall 21 of the substrate 12 by a sputtering method, a vapor deposition method, an electroless plating method, or the like.

FIG. 6 is a cross-sectional view showing a method of manufacturing the signal transmission substrate 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 a method of manufacturing the signal transmission substrate 10 according to the present embodiment following FIG. After forming the resist layer 37, as shown in FIG. 7, the plating layer 222 is formed on the seed layer 221 not covered by the resist layer 37 by electrolytic plating using the resist layer 37 as a mask.

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

FIG. 9 is a cross-sectional view showing a method of manufacturing the signal transmission substrate 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 on which the resist layer 37 was formed is removed by wet etching. As a result, the through silicon via 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. The step of annealing the plating layer 222 may be carried out.

(Step of forming the first organic layer 34 on the first surface and the first organic layer 42 on the second surface)
FIG. 10 is a cross-sectional view showing a method of manufacturing the signal transmission substrate 10 according to the present embodiment following FIG. After forming the through silicon via 22, the first surface first conductive layer 31 and the second surface first conductive layer 41, as shown in FIG. 10, on the first surface 13 or on the first surface first conductive layer 31. The 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 treatment and development treatment using a photosensitive film containing an organic material, or may contain an organic material. It may be formed by applying a liquid to be applied by spin coating and drying it. 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 the elastic modulus of the first surface first organic layer. It may be smaller than the elastic modulus of 34.

(Step of forming the first surface second conductive layer 33 and the second surface second conductive layer 43)
FIG. 11 is a cross-sectional view showing a method of manufacturing the signal transmission substrate 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. 11, the first surface second including the signal layer 331 on the first surface first organic layer 34. The conductive layer 33 is formed. Further, as shown in FIG. 11, a second surface second conductive layer 43 including a 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 subjected to 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 formed larger than the wiring width W1 of the signal layer 331 shown in FIG.

(Step of forming the first surface second organic layer 36 and the second surface second organic layer 44)
FIG. 12 is a cross-sectional view showing a method of manufacturing the signal transmission substrate 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. 12, on the first surface first organic layer 34 or the first surface second conductive layer 33, a second surface is formed. The first surface second organic layer 36 is formed. Further, as shown in FIG. 12, the 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 treatment and development treatment using a photosensitive film containing an organic material, or may contain an organic material. It may be formed by applying a liquid to be applied by spin coating and drying it.

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 elastic modulus of the first surface second organic layer. Make it smaller than the elastic modulus of 36. 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 with respect to 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. By forming the second surface third conductive layer 45 on the organic layer 44, the signal transmission substrate 10 shown in FIG. 1 can be obtained.

(Experimental example)
Next, an experimental example of the signal transmission board 10 according to the present embodiment will be described. FIG. 13 is a diagram showing the correspondence between the temperature, the stress of the first insulating layer corresponding to the temperature, and the stress-correlated parameter in the experimental example of the signal transmission substrate 10 according to the present embodiment. FIG. 14 is a diagram showing the correspondence between the temperature, the stress of the second insulating layer corresponding to the temperature, and the stress-correlated parameter in the 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 the numerical value calculated by exponentiation with the numerical value immediately after "E" as the base of 10. It is a numerical value. For example, “6.01E + ⁰⁵ ” in FIG. 13 is 6.01 × 105.

In the experimental example, as a sample simulating the signal transmission substrate 10 of FIG. 1, the first insulating layer is provided on the first surface 13 of the substrate 12, and the second insulating layer is provided on the second surface 14 of the substrate 12. A sample was prepared and the balance of stress between the first insulating layer and the second insulating layer was evaluated for this sample. As shown in FIG. 13, the material of the first insulating layer was PN, which is a photosensitive polyimide coating agent manufactured by Toray Industries, Inc., and the thickness was 10 μm. As shown in FIG. 14, the material of the second insulating layer was LPA, which is a photosensitive polyimide adhesive sheet manufactured by Toray Industries, Inc., and the thickness was 19 μm.

As shown in FIGS. 13 and 14, the cure temperature, that is, the thermosetting temperature of the first insulating layer and the second insulating layer is both 200 ° C.

As shown in FIGS. 13 and 14, the difference in product between the indentation elastic modulus and the thickness of the first insulating layer and the second insulating layer was 15% or less at a temperature equal to or lower than the cure temperature. For example, at room temperature of 25 ° C., the product of the indentation elastic modulus of the first insulating layer and the thickness is 37, whereas the product of the indentation elastic modulus of the second insulating layer and the thickness is 39.9. rice field. Therefore, at 25 ° C., the difference in product between 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 of the second insulating layer and the thickness of 39.9 and multiplying by 100, the percentage of the difference 2.9 is 7.27%, which is 15% or less. I want it.

Further, as shown in FIGS. 13 and 14, the first insulating layer and the second insulating layer have a cure temperature of 200 ° C., which is an example of the first temperature, and a room temperature of 25 ° C., which is an example of the second temperature after curing. In the temperature section up to, the ratio of the difference between the thermal expansion coefficient α, the temperature change ΔT with respect to the cure temperature, the elastic modulus E, and the product α × ΔT × E × h is {(4.08E + 05-3). It was 6.25% by .84E + 05) /3.84+E05} × 100. The denominator of the ratio is the product of the coefficient of thermal expansion α of the second insulating layer, the temperature change ΔT, the elastic modulus E, and the thickness h. Further, α × ΔT × E is a stress acting on the first and second insulating layers in response to a temperature change from the cure temperature, that is, stress. The stress at cure temperature is zero. The ratio of 6.25% obtained from FIGS. 13 and 14 is a sufficiently low value when the threshold value of the ratio is 15%.

According to the experimental example, the stress on the first surface 13 side and the stress on the second surface 14 side are set by reducing the difference in product between the elastic modulus and the thickness between the first insulating layer and the second insulating layer to 15% or less. It can be seen that the difference from the stress of can be sufficiently suppressed. That is, according to the experimental example, it can be seen that warpage of the substrate 12 can be effectively suppressed during the cooling period after the curing step.

FIG. 15 is a perspective view of an indenter I that can be used for measuring 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 substrate 10 according to the present 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 the experimental example of the signal transmission substrate 10 according to the present 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 the experimental example of the signal transmission board 10 according to the present embodiment. In FIG. 17, the horizontal axis indicates the pushing depth of the indenter I, and the vertical axis indicates the load applied to the first and second insulating layers by the indenter I. Hereinafter, the first insulating layer and the second insulating layer are also simply referred to as an insulating layer.

The indentation modulus shown in FIGS. 13 and 14 can be measured by a nanoindentation test using the Berkovich-type indenter I shown in FIG. The indenter I shown in FIG. 15 has an apex angle of 115 ° on the pyramidal surface. As shown in FIG. 16, in the nanoindentation test, the indenter I mounted on the transducer is pushed into the insulating layer placed on the stage while applying a load by the transducer. As shown in FIG. 17, the load applied from the indenter I to the insulating layer increases by following a quadratic load-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 under load due to the pressing load of the indenter I. This deformation is due to both elastic deformation and plastic deformation. As shown in FIGS. 16 and 17, when the pressing is completed, the pressing depth of the indenter I becomes the maximum value h _max , and the load also becomes the maximum value P _max . After the indenter I has been pushed in, the indenter I is moved in the direction opposite to the pushing direction. As a result, as shown in FIG. 17, the load applied from the indenter I to the insulating layer is reduced by following a quadratic load unloading curve B steeper than the load load curve A. Further, as shown in FIG. 16, the surface of the insulating layer is deformed from the surface under load to the surface after unloading due to the elastic recovery accompanying the unloading of the indenter I. The surface after unloading exhibits deformation marks recessed from the initial surface due to the influence of plastic deformation under load. In FIGS. 16 and 17, the depth of the surface after unloading is h _f .

In the above nanoindentation test, the indentation elastic modulus _EIT of the insulating layer can be obtained by the following equation.
E _IT = {1- (VS) ² } / [(1 / _Er )- _{ 1- (Vi) ² } / E _{i ]} (1)
However, in the formula (1), VS is the _Poisson 's ratio of the insulating layer. Vi is the Poisson's ratio of the indenter _I. E _i is the elastic modulus of the indenter I. _Er is the reduced elastic modulus of the indentation contact.

The reduced elastic modulus _Er of the indentation contact in the equation (1) can be obtained by the following equation.
_Er = π 1/ ² /2CA _p ^1/2 (2)
However, in the formula (2), C is the slope dP / dh of the tangent line of the load unloading curve B at the maximum value P _max of the load shown in FIG. _Ap is the projected area where the indenter I and the insulating layer are in contact with each other.

_Ap in the formula (2) can be obtained by the following formula.
_Ap = 23.96 × {h _max -ε (h _max -h _C )} (3)
However, in the mathematical formula (3), h _max is the maximum value of the pushing depth described above. ε is a correction coefficient due to the geometric shape of the indenter I, which is 0.75 in the case of the diamond Vickers indenter. h _C is the intersection of the tangent line of the load unloading curve B at the maximum value P _max of the above-mentioned load and the horizontal axis of FIG.

Hereinafter, the action brought about by this embodiment will be described.

In the signal transmission substrate 10 of the present 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. Further, the second surface second organic layer 44 has a large thickness and a small elastic modulus with respect to 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 taken into consideration, 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. In the case of, the stress on the second surface 14 side by the second surface second organic layer 44 is larger than the stress on the first surface 13 side by the first surface second organic layer 36, and the stress is large. There is a risk that the substrate 12 will 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 the elastic modulus of the first surface second organic layer 36 having a small thickness, so that the first surface 13 is formed. Both impedance matching and stress balance can be ensured between the side and the second surface 14 side. As a result, it is possible to achieve both improvement in signal transmission efficiency and suppression of warpage of the substrate 12.

Further, in the present embodiment, improvement of signal transmission efficiency and suppression of warpage of the substrate 12 can be realized in a strip line having excellent noise characteristics as compared with a coplanar line.

(First modification)
Next, a first modification 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 substrate 10 according to the first modification of the present embodiment. FIG. 18 is positionally corresponding 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 substrate 10 according to the first modification of the present embodiment. FIG. 19 corresponds positionally to the cross-sectional view of FIG.

In FIGS. 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 in which the second surface second conductive layer 43 forms a strip line on the second surface 14 side between the second surface first conductive layer 41 and the second surface third conductive layer 45 has been described.

On the other hand, in the first modification, the first surface second conductive layer 33 constitutes the coplanar line on the first surface 13 side, and the second surface second conductive layer 43 forms the coplanar line on the second surface 14 side. Make up the track.

Specifically, as shown in FIG. 18, the first surface second conductive layer 33 has a signal layer 331 and, as an example of a third ground layer, a ground adjacent to the signal layer 331 at intervals in the width direction D2. It has a layer 332 and. Further, as shown in FIG. 19, the second surface second conductive layer 43 includes a signal layer 431 and, as an example of the fourth ground layer, a ground layer 432 adjacent to the signal layer 431 at intervals in the width direction D2. Has.

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 the second surface second. 2 The organic layer 44 has a larger thickness and a smaller elastic modulus than the first surface and the second organic layer 36, so that both impedance matching and stress balance between the first surface 13 side and the second surface 14 side can be achieved. Can be secured. As a result, it is possible to achieve both improvement in signal transmission efficiency and suppression of warpage of the substrate 12.

(Second modification)
Next, a second modification having a differential transmission line for transmitting one data by 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 substrate 10 according to the second modification of the present embodiment. FIG. 20 is positionally corresponding 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 substrate 10 according to the second modification of the present embodiment. FIG. 21 is positionally corresponding to the cross-sectional view of FIG.

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

Specifically, as shown in FIG. 20, the first surface second conductive layer 33 has a reference to two signal layers 331a and 331b and signal layers 331a and 331b arranged at intervals in the width direction D2. It has a ground layer 332 arranged at intervals on the outer side in the width direction D2. The two signal layers 331a and 331b divide and transmit one electric signal. As shown in FIG. 21, the second surface second conductive layer 43 has two signal layers 431a and 431b arranged at intervals in the width direction D2 and a width direction D2 with respect to the signal layers 431a and 431b. It has a ground layer 432 arranged at intervals on the outside. Each of the two signal layers 431a and 431b is electrically connected to each of the two signal layers 331a and 331b via a through electrode 22. The two signal layers 431a and 431b transmit the same electric signal as the electric signal transmitted by each of the two signal layers 331a and 331b.

According to the second modification, by having a differential transmission line, a signal waveform can be formed with a small voltage. 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, a high-frequency electric signal can be appropriately transmitted as compared with the single-ended method. Further, 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 the wiring width of the signal layers 331a and 331b on the first surface 13. It is larger than W1 and the second surface second organic layer 44 has a thickness larger than that of the first surface second organic layer 36 and a smaller elastic modulus, so that it is between the first surface 13 side and the second surface 14 side. In, both impedance matching and stress balance can be ensured. As a result, it is possible to achieve both improvement in signal transmission efficiency and suppression of warpage of the substrate 12.

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

As shown in FIG. 22, in the third modification, a part of the signal layer 311 together with the dielectric 32 located on the signal layer 311 and the first surface second conductive layer 33 located on the dielectric 32. , MIM (Metal-Insulator-Metal) structure capacitor 15 is configured. The 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 a transmission line other than the above-mentioned various transmission lines. For example, the signal transmission board 10 may be applied to a microstrip line.

It is possible to make various changes to the above-described embodiment. Hereinafter, modification examples will be described 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 will be used for the portions that can be configured in the same manner as in the above-described embodiment. Duplicate explanations will be omitted. Further, when it is clear that the action and effect obtained in the above-described embodiment can be obtained in the modified example, the description thereof may be omitted.

An example of a product on which a through-electrode substrate is mounted FIG. 23 is a diagram showing an example of a product on which the signal transmission board 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 mounted on a notebook personal computer 110, a tablet terminal 120, a mobile phone 130, a smartphone 140, a digital video camera 150, a digital camera 160, a digital clock 170, a server 180, and the like.

10 Signal transmission board 12 Board 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 (11)

A substrate having a first surface and a second surface opposite to the first surface,
The first signal layer located on the first surface and
The first ground layer located on the first signal layer and
With at least one third insulating layer located between the first surface and the first signal layer and at least one on the first ground layer.
A second signal layer located on the second surface, electrically connected to the first signal layer, and having a larger width direction crossing the signal transmission direction than the first signal layer.
The second ground layer located on the second signal layer and
It is located between the second surface and the second signal layer and at least one of the second ground layers, and has a larger dimension in the thickness direction intersecting the first surface than the third insulating layer and has a modulus of elasticity. A signal transmission substrate comprising at least one small fourth insulating layer. The difference between the product of the thickness direction dimension and the elastic modulus of the third insulating layer and the product of the thickness direction dimension and the elastic modulus of the fourth insulating layer is the thickness direction dimension of the fourth insulating layer. The signal transmission substrate according to claim 1, which has a ratio equal to or less than a threshold value with respect to the product with the elastic modulus. The signal transmission board according to claim 2, wherein the threshold value is 15%. A first insulating layer located between the first signal layer and the first ground layer,
A second insulating layer, which is located between the second signal layer and the second ground layer and has a larger dimension in the thickness direction and a smaller elastic modulus intersecting the first surface than the first insulating layer, is further provided. , The signal transmission board according to claim 2 or 3. The sum of the product of the thickness direction dimension and elastic modulus of the first insulating layer and the product of the thickness direction dimension and elastic modulus of the third insulating layer, and the thickness direction dimension and elasticity of the second insulating layer. The difference between the product of the rate and the product of the thickness direction dimension of the fourth insulating layer and the elastic modulus is the product of the thickness direction dimension of the second insulating layer and the elastic modulus and the fourth insulation. The signal transmission substrate according to claim 4, which has a ratio equal to or less than a threshold value with respect to the sum of the dimension in the thickness direction of the layer and the product of the elastic modulus. One of claims 1 to 4, further comprising a through electrode that 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. The signal transmission board described in. A third ground layer located on the first surface and adjacent to the first signal layer in the width direction,
The signal transmission substrate according to any one of claims 1 to 6, further comprising a fourth ground layer located on the second surface and adjacent to the second signal layer in the width direction. One of claims 1 to 7, further comprising 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. The signal transmission board according to one item. The signal transmission substrate according to any one of claims 1 to 8, wherein the substrate contains glass. The signal transmission board according to any one of claims 1 to 9, which can be mounted on a wiring board on the second surface side and can mount an integrated circuit on the first surface. A step of preparing a substrate having a first surface and a second surface opposite to the first surface, and
The step of forming the first signal layer on the first surface and
The step of forming the first ground layer on the first signal layer and
A step of forming at least one third insulating layer between the first surface and the first signal layer and at least one of the first ground layers.
A step of forming a second signal layer on the second surface, which is electrically connected to the first signal layer and has a larger width direction crossing the signal transmission direction than the first signal layer.
The step of forming the second ground layer on the second signal layer and
At least one of the space between the second surface and the second signal layer and on at least one of the second ground layers has a larger dimension in the thickness direction intersecting the first surface than the third insulating layer and a smaller elastic modulus. A method for manufacturing a signal transmission substrate, comprising a step of forming a fourth insulating layer.

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