JP2018148141A - Signal transmission board and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal transmission board capable of improving transmission efficiency of signal while restraining warpage of a substrate, and to provide a manufacturing method thereof.SOLUTION: A signal transmission board includes a substrate 12 having a first face 13 and a second face 14 opposite to the first face 13, a first signal layer 331 located on the first face 13, a first insulation layer 36 located on the first signal layer 331, a first ground layer 351 located on the first insulation layer 36, a second signal layer 431 located on the second face 14, connected electrically with the first signal layer 331, and having a larger dimension than the first signal layer 331 in the width direction crossing the signal transmission direction, a second insulation layer 44 located above the second signal layer 431, and having a larger dimension than the first insulation layer 36 in the thickness direction crossing the first face 13 and a smaller degree of elasticity, and a second ground layer 451 located above the second insulation layer 44.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, various techniques related to an interposer for relaying a mother board and an IC chip having different terminal pitches have been proposed. For example, Patent Document 1 discloses an interposer including a through electrode that penetrates 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 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. Signals can be transmitted between the connected IC chip and the motherboard electrically connected to the signal layer on the second surface.

JP 2014-139963 A

  In order to efficiently transmit a signal between the mother board 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 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 on the first surface acting on the substrate from the first surface due to the stress acting on the insulating layer on the first surface and the second surface It is difficult to balance the stress on the substrate from the second surface side by the stress acting on the upper insulating layer. 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 warps.

  The present disclosure has been made in view of the above points, and an object thereof is to provide a signal transmission board that can achieve both improvement in signal transmission efficiency and suppression of warpage of the board, and a method for manufacturing the same. To 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 the first surface;
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 larger dimension in the width direction intersecting 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 intersecting the first surface than the first insulating layer and having a small elastic modulus;
There is provided a signal transmission board comprising a second ground layer located on the second insulating layer.

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

  The threshold may be 15%.

  The difference between the product of the coefficient of thermal expansion of the first insulating layer and the dimension in the thickness direction and the modulus of elasticity and the product of the coefficient of thermal expansion of the second insulating layer and the dimension in the thickness direction and the modulus of elasticity are the second You may have a ratio below a threshold value with respect to the product of the thermal expansion coefficient of a insulating layer, the dimension of a thickness direction, and an elasticity modulus.

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;
And at least one fourth insulating layer located between the second surface and the second signal layer and at least one on the second ground layer,
The sum of the product of the dimension in the thickness direction of the first insulating layer and the elastic modulus, the product of the dimension in the thickness direction of the third insulating layer and the elastic modulus, and the dimension in the thickness direction of the second insulating layer and elasticity. The difference between the product of the modulus and the sum of the product of the dimension in the thickness direction of the fourth insulation layer and the modulus of elasticity is the product of the product of the dimension in the thickness direction of the second insulation layer and the modulus of elasticity and the fourth insulation. You may have a ratio below a threshold with respect to the sum of the product of the dimension of the thickness direction of a layer, and an elasticity modulus.

  You may further provide the penetration electrode which penetrated the said board | substrate from the said 1st surface to the said 2nd surface, and was electrically connected to the said 1st signal layer and the said 2nd 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.

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

In another aspect of the disclosure,
Preparing a substrate having a first surface and a second surface opposite to the first surface;
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 electrically connected to the first signal layer and having 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 than the first insulating layer and having a low elastic modulus;
Forming a second ground layer on the second insulating layer. A method for manufacturing a signal transmission board is provided.

Forming the first insulating layer includes thermally curing the first insulating layer at a first temperature;
Forming the second insulating layer includes thermosetting the second insulating layer at the first temperature when thermosetting the first insulating layer;
At least in the temperature section from the first temperature to the second temperature after thermosetting, 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 modulus. The difference between the thermal expansion coefficient of the second insulating layer, the temperature change with respect to the first temperature, the product of the dimension in the thickness direction and the elastic modulus 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 thickness, 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.

It is sectional drawing which shows the signal transmission board | substrate by this embodiment. It is II-II sectional drawing of FIG. 1 which shows the signal transmission board | substrate by this embodiment. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1 illustrating the signal transmission board according to the present embodiment. It is sectional drawing which shows the manufacturing method of the signal transmission board | substrate by this embodiment. FIG. 5 is a cross-sectional view showing the method for manufacturing the signal transmission board according to the present embodiment following FIG. 4. FIG. 6 is a cross-sectional view illustrating the method of manufacturing the signal transmission board according to the present embodiment following FIG. 5. FIG. 7 is a cross-sectional view showing the method for manufacturing the signal transmission board according to the present embodiment following FIG. 6. FIG. 8 is a cross-sectional view illustrating the method of manufacturing the signal transmission board according to the present embodiment following FIG. 7. FIG. 9 is a cross-sectional view illustrating the method for manufacturing the signal transmission board according to the present embodiment following FIG. 8. FIG. 10 is a cross-sectional view showing the method for manufacturing the signal transmission board according to the present embodiment following FIG. 9; It is sectional drawing which shows the manufacturing method of the signal transmission board | substrate by this embodiment following FIG. FIG. 12 is a cross-sectional view showing the method of manufacturing the signal transmission board according to the present embodiment following FIG. 11. In the experimental example of the signal transmission board according to the present embodiment, it is a diagram showing a correspondence relationship between the temperature, the stress of the first insulating layer according to the temperature, and the parameter correlated with the stress. In the experimental example of the signal transmission board according to the present embodiment, it is a diagram showing a correspondence relationship between the temperature, the stress of the second insulating layer according to the temperature, and the parameter correlated with the stress. In the experimental example of the signal transmission board according to the present embodiment, it is a perspective view of an indenter that can be used for measurement of indentation elastic modulus correlated with stress of the first insulating layer and the second insulating layer. It is sectional drawing which shows the measurement example of the indentation elastic modulus of a 1st insulating layer and a 2nd insulating layer in the experiment example of the signal transmission board | substrate by this embodiment. It is a graph which shows the example of a measurement of the indentation elastic modulus of a 1st insulating layer and a 2nd insulating layer in the experiment example of the signal transmission board by this embodiment. It is sectional drawing by the side of the signal layer on the 1st surface which shows the signal transmission board | substrate by the 1st modification of this embodiment. It is sectional drawing by the side of the signal layer on the 2nd surface which shows the signal transmission board | substrate by the 1st modification of this embodiment. It is sectional drawing by the side of the signal layer on the 1st surface which shows the signal transmission board | substrate by the 2nd modification of this embodiment. It is sectional drawing by the side of the signal layer on the 2nd surface which shows the signal transmission board | substrate by the 2nd modification of this embodiment. It is sectional drawing which shows the signal transmission board | substrate by the 3rd modification of this embodiment. It is a figure which shows the example of the product in which a signal transmission board | substrate is mounted.

  Hereinafter, a configuration of a signal transmission board and a manufacturing method thereof according to an embodiment of the present disclosure will be described in detail with reference to the drawings. The following embodiments are examples of embodiments of the present disclosure, and the present disclosure is not construed as being limited to these embodiments. Further, in this specification, terms such as “substrate”, “base material”, “sheet”, and “film” are not distinguished from each other only based on the difference in names. For example, “substrate” and “base material” are concepts including members that can be called sheets and films. Furthermore, as used in this specification, the shape and geometric conditions and the degree thereof are specified. For example, terms such as “parallel” and “orthogonal”, length and angle values, and the like are bound to a strict meaning. Therefore, it should be interpreted including the extent to which similar functions can be expected. In the drawings referred to in this embodiment, the same portions or portions having similar functions are denoted by the same reference symbols or similar reference symbols, and repeated description thereof may be omitted. In addition, the dimensional ratio in the drawing may be different 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 an interposer board that transmits a high-frequency signal, for example. FIG. 1 is a cross-sectional view showing a signal transmission board 10 according to the present embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1 showing the signal transmission board 10 according to the present embodiment. 3 is a cross-sectional view taken along the line III-III of FIG. 1 showing the signal transmission board 10 according to the present 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 unit 30, and a second wiring structure unit 40. Hereinafter, each component of the signal transmission board 10 will be described.

(Substrate 12)
The substrate 12 includes a first surface 13 and a second surface 14 located on the opposite side of the first surface 13. The substrate 12 is provided with a plurality of through holes 20 that penetrate from the first surface 13 to the second surface 14. In FIG. 1, only one through hole 20 is representatively illustrated. 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.

The substrate 12 includes an inorganic material having a certain insulating property. For example, the substrate 12 is a glass substrate, quartz substrate, sapphire substrate, resin substrate, silicon substrate, silicon carbide substrate, alumina (Al ₂ O ₃ ) substrate, aluminum nitride (AlN) substrate, zirconium oxide (ZrO ₂ ) substrate, etc. Alternatively, these substrates are stacked. 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 non-alkali glass. The alkali-free glass is a glass that does not contain an alkali component such as sodium or potassium. The alkali-free glass includes, for example, boric acid instead of an alkali component. The alkali-free glass includes an alkaline earth metal oxide such as calcium oxide or 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 in the thickness direction D3 of the substrate 12. 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. A part of the side wall 21 may be curved.

(Penetration electrode 22)
The through electrode 22 is a member that is located inside the through hole 20 and has conductivity. In the present embodiment, the thickness of the through electrode 22 is smaller than the width of the through hole 20, and therefore there is a space where the through electrode 22 does not exist inside the through hole 20. 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, 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 electrode 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 sidewall 21 of the through hole 20 and the seed layer. As a material constituting the intermediate layer, for example, titanium, titanium nitride, molybdenum, molybdenum nitride, tantalum, tantalum nitride, or the like, or a laminate of these can be used. The intermediate layer is formed by, for example, a physical film formation method such as an evaporation method or a sputtering method. An intermediate | middle layer plays the role of improving the adhesiveness of the seed layer and plating layer with respect to the side wall 21, for example. Further, the intermediate layer may play a role of suppressing diffusion of the metal element contained in the seed layer or the plating layer into the substrate 12 through the side wall 21 of the through hole 20.

(First wiring structure 30)
Next, the first wiring structure unit 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 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 unit 30 includes a first surface first conductive layer 31, a first surface first organic layer 34 that is an example of a third insulating layer, and a first surface second conductive layer 33. And a first surface second organic layer 36 that is an example of a first insulating layer, and a first surface third conductive layer 35.

  The first wiring structure unit 30 has a strip line that sandwiches the front and back of the signal line with a ground plane through an insulating layer. Hereinafter, the strip line included in the first wiring structure unit 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 that is an example of a first signal layer, a ground layer 311, and a ground layer 351 that is an example of a 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 constituted by a part of the first surface first conductive layer 31.

  As shown in FIG. 1, the first surface first conductive layer 31 includes 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 foundation for growing the plating layer 222 by depositing metal ions in the plating solution during the electroplating step of forming the plating layer 222 by electrolytic plating. is there. As a 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 sequentially laminated, 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 copper and a metal other than copper, for example, an alloy of gold, silver, platinum, rhodium, tin, aluminum, nickel, and chromium, or a metal other than copper and 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 and is electrically connected to a reference potential such as a ground potential and electrically insulated from the through electrode 22. is there. The ground layer 311 is located on the first surface 13 so as to be adjacent to the signal layer 331 with a space in the lower direction D32 of FIG. In the example 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 therebetween. The ground layer 311 has a larger total area than 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 between the ground layer 311 and the signal layer 331.

[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 and includes an organic material and has an insulating property.

  The first surface first organic layer 34 has a dimension in the thickness direction D3 in consideration of both impedance matching of the transmission path between the first surface 13 side and the second surface 14 side and stress balance by the insulating layer, that is, thickness. h3 may be included. Further, the first surface first organic layer 34 may have an elastic modulus considering both the impedance matching and the stress balance. As an example, the first organic layer 34 on the first surface may have a thickness h3 of 10 μm, and may have an indentation elastic modulus of 3.70 GPa at 25 ° C., that is, room temperature.

  The first surface first organic layer 34 may include 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 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 prevent a 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 | substrate 10 can be expanded to the high frequency side.

  The first surface first organic layer 34 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 is applied by spin coating. And 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 with an interval in the upper direction D31 of FIG. 1 in the thickness direction D3. It is a layer which has. 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 constituted by 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 plating layer sequentially stacked on the first-surface first organic layer 34, similarly to the through electrode 22 and the first-surface first conductive layer 31. 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 a layer that is located on the first surface first organic layer 34, which is an example on the first surface 13, and that is electrically connected to the through electrode 22 and transmits an electrical signal such as a high-frequency signal. . Examples of the high frequency signal include an electrical signal of 0.1 GHz or more. The signal layer 331 extends along the first surface 13 in the extending direction D1 in FIG. 1, which is an example of the signal transmission direction, that is, in the direction perpendicular to the paper surface in FIG. In the example of FIG. 1, the signal layer 331 is electrically connected to the through electrode 22 through a part 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. 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 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 with the first organic layer 34 on the first surface can be suppressed, so that peeling of the signal layer 331 can be suppressed.

  An IC chip having a terminal pitch smaller than that of the mother board is electrically connected to the first surface 13 side. For this reason, the signal layer 331 on the first surface 13 side is such that the dimension in the width direction D2 orthogonal to the extending direction D1 indicated by the symbol W1 in FIG. 2, that is, the wiring width W1, is small in accordance with 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 the first surface second conductive layer 33, includes 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 impedance matching of the transmission path 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 may have an indentation elastic modulus of 3.70 GPa at 25 ° C. Thus, on condition that the first surface second organic layer 36 has a thickness h1 and an elastic modulus considering both impedance matching and stress balance, both impedance matching and stress balance are achieved. 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 includes 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 you can. As an organic material of 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 prevent a 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. Thereby, the band of the signal transmission board | substrate 10 can be expanded further to the high frequency side more suitably.

  As with the first surface first organic layer 34, the first surface second organic layer 36 may be formed by, for example, exposure processing and development processing using a photosensitive film containing an organic material, or Alternatively, 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 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 an interval in the upward direction D 31 of FIG. It is a layer having. 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 constituted by 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 connected to the through electrode 22 via the signal layer 331. Is electrically connected.

  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 sequentially stacked, like 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 is electrically connected to a reference potential such as a ground potential and has a characteristic impedance of the signal layer 331 electrically insulated from the through electrode 22. The layer to control. The ground layer 351 has a larger total area than 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 therebetween. 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 unit 40 includes layers such as a conductive layer and 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 unit 40 includes a second surface first conductive layer 41, a second surface first organic layer 42 that is an example of a fourth insulating layer, and a second surface second conductive layer 43. And a second surface second organic layer 44 that is an example of a second insulating layer, and a second surface third conductive layer 45.

  Similar to the first wiring structure unit 30, the second wiring structure unit 40 has a strip line that sandwiches the front and back of the signal line with the ground surface through an insulating layer. Hereinafter, the strip line included in the second wiring structure unit 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 through 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 that is an example of a second signal layer, a ground layer 411, and a ground layer 451 that 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 constituted by a part of the second surface first conductive layer 41.

  As shown in FIG. 1, the second surface first conductive layer 41 includes a seed layer 221 and a plating layer 222, as with 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 and is electrically connected to a reference potential such as a ground potential and electrically insulated from the through electrode 22. is there. The ground layer 411 has a larger total area than 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 with an interval in the upper direction D31 of FIG. 1 in the thickness direction D3. In the example 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 therebetween. 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 between the ground layer 411 and the signal layer 431.

[Second surface first organic layer 42]
The 2nd surface 1st organic layer 42 is a layer which is located on the 2nd surface 14 or the 2nd surface 1st conductive layer 41, contains an organic material, and has insulation.

  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 path between the first surface 13 side and the second surface 14 side. Also good. For example, the second surface first organic layer 42 may have a larger thickness and a smaller elastic modulus than the first surface first organic layer 34. In other words, the difference between the product of 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 has a thickness h4 of 19 μm and may have an indentation elastic modulus of 2.10 GPa at 25 ° C.

  Similar to the first surface first organic layer 34, the second surface first organic layer 42 includes 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 you can. 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 having a small dielectric loss tangent, it is possible to prevent a 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 | substrate 10 can be expanded 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 is applied by spin coating. And may be formed by drying.

[Second surface second conductive layer 43]
The second surface second conductive layer 43 is located on the second surface 14 so as to be adjacent to the second surface first conductive layer 41 with an interval in the lower direction D32 of FIG. 1 in the thickness direction D3. It is a layer which has. 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 constituted by 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 stacked 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 positioned 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 through the through electrode 22, It is a layer that transmits an electrical signal such as a high-frequency signal together with the layer 331. The signal layer 431 extends along the first surface 13 in the extending 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. 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 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 with the second surface first organic layer 42 can be suppressed, so that the peeling of the signal layer 431 can be suppressed.

  The dimension of the signal layer 431 in the width direction D2 indicated by the reference sign W2 in FIG. 3, that is, the wiring width W2, is a wiring width W2 in consideration of impedance matching of the transmission path 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 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. The ratio S1 / d1 of the distance d1 between S1, the signal layer 331, and the ground layer 351 may have a predetermined proportional relationship, for example, may coincide with each other. 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. As described above, both of the impedance matching and the stress balance are ensured on the condition that the signal layer 431 has a relationship between the wiring widths W2 and W1 in consideration of impedance matching with the signal layer 331. be able to. Thereby, the improvement of the transmission efficiency of a signal and suppression of the curvature of the board | substrate 12 can be made to make compatible.

[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, includes 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 includes the first surface 13 side and the second surface 14. The thickness h2 and the elastic modulus in consideration of both the impedance matching of the transmission line and the balance of stress between the two sides.

  Specifically, the second surface second organic layer 44 is thicker and has a smaller elastic modulus than the first surface second organic layer 36. When the elastic modulus is small, it can be said that the rigidity is small, that is, soft.

  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 first surface 13 side on which the IC chip is mounted is mounted on the motherboard. It is made 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 is proportional to the distance d2 between the signal layer 431 having a large wiring width W2 and the ground layer 451. The thickness h2 of the first surface is larger than the thickness h1 of the first organic layer 36 on the first surface, 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 first surface second organic layer 36 having a small thickness. As described above, the first surface second organic layer 36 and the second surface second organic layer 44 have impedance and thickness matching in consideration of both impedance matching and stress balance. Both stress balance can be ensured. Thereby, the improvement of the transmission efficiency of a signal and suppression of the curvature of the board | substrate 12 can be made to make compatible.

The difference between the thickness and the elastic modulus of the second surface second organic layer 44 relative to the first surface second organic layer 36 may be a threshold value or less. Specifically, the difference between the product of the thickness of the first surface second organic layer 36 and the elastic modulus and the product of the thickness of the second surface second organic layer 44 and the elastic modulus is the second surface second organic layer. You may have a ratio below a threshold with respect to the product of 44 thickness and an elasticity modulus. The threshold may be 15%.
As an example, the second organic layer 44 on the second surface has a thickness h4 of 19 μm and may have an indentation elastic modulus of 2.10 GPa at 25 ° C. The product of the thickness and the elastic modulus of the organic layers 36 and 44 is proportional to the stress acting on the organic layers 36 and 44. Therefore, the impedance matching and the balance of stress are reduced by setting the difference between the product of the thickness and the elastic modulus proportional to the stress 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. Both can be secured more effectively. Thereby, improvement in signal transmission efficiency and suppression of warpage of the substrate 12 can be more effectively achieved.

  The second surface second organic layer 44 may have a difference in product of a thermal expansion coefficient, a thickness, and an elastic modulus equal to or less than a threshold with respect to the first surface second organic layer 36. 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 second surface second organic layer 44 may have a ratio equal to or lower than a threshold with respect to the product of the thermal expansion coefficient, the thickness, and the elastic modulus. The threshold may be 15%. The product of the thermal expansion coefficient, the thickness and the elastic modulus of the organic layers 36 and 44 is more precisely proportional to the stress of the organic layers 36 and 44 than the product of the thickness and the elastic modulus. Therefore, by setting the difference 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, the product of the thermal expansion coefficient, thickness, and elastic modulus, which are precisely proportional to the stress, Both impedance matching and stress balance can be more effectively ensured. Thereby, the improvement of the transmission efficiency of a signal and suppression of the curvature of the board | substrate 12 can be made still more effective.

  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 a threshold value. Specifically, the sum of the product of the thickness h1 of the first surface second organic layer 36 and the elastic modulus, 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. You may have a ratio below a threshold with respect to the sum of the product of an elasticity modulus, and the product of the thickness h4 of the 2nd surface 1st organic layer 42, and an elasticity modulus. The threshold may be 15%. The stress acting on each of the organic layers 34 and 36 on the first surface 13 is involved in the stress on the first surface 13 side. Further, the stress acting on each of 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 stress balance is further improved by having a difference equal to or less than a threshold with respect to the sum of the product of the thickness h2 and the elastic modulus of the first surface and the product of the thickness h4 of the second surface first organic layer 42 and the elastic modulus. It can be secured effectively. Thereby, the improvement of the transmission efficiency of a signal and suppression of the curvature of the board | substrate 12 can be made still more effective. 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 smaller than the threshold value is an additional organic layer on the ground layer 351, that is, The same applies to the case where the third insulating layer is provided and the additional organic layer, that is, the fourth insulating layer is provided over the ground layer 451.

  Similar to the first surface first organic layer 34, the second surface second organic layer 44 includes 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 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 having a small dielectric loss tangent, it is possible to prevent a 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. Thereby, the band of the signal transmission board | substrate 10 can be expanded further to the high frequency side more suitably.

  As with the first surface first organic layer 34, the second surface second organic layer 44 may be formed by, for example, exposure processing and development processing using a photosensitive film containing an organic material, or Alternatively, 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 located on the first surface 13 so as to be adjacent to the second surface second conductive layer 43, that is, the signal layer 431, with an interval in the downward direction D 32 of FIG. It is a layer having. 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 constituted by a 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 that is 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 sequentially stacked, like 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 organic layer 44 on the second surface, and has a characteristic impedance of the signal layer 431 electrically connected to a reference potential such as a ground potential and electrically insulated from the through electrode 22. The layer to control. The ground layer 451 has a larger total area than the signal layer 431. The ground layer 451 is opposed to the signal layer 431 so as to sandwich the second organic layer 44 on the second surface. 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 between the ground layer 431 and the signal layer 431.

The following method for producing a signal transmission substrate 10, one example of a manufacturing method of a signal transmission substrate 10 will be described with reference to FIGS. 4 through 17.

(Formation process of through-hole 20)
FIG. 4 is a cross-sectional view illustrating the method for manufacturing the signal transmission board 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. Thereafter, an opening is provided at a position corresponding to the through hole 20 in the resist layer. Next, by processing the substrate 12 in the opening of the resist layer, the 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 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 a laser for laser processing, an excimer laser, an Nd: YAG laser, a femtosecond laser, or the like can be used. When an Nd: YAG laser is employed, 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, or the like can be used.

  Further, laser irradiation and wet etching can be appropriately combined. Specifically, first, a deteriorated layer is formed in a region of the substrate 12 where the through hole 20 is to be formed by laser irradiation. Subsequently, the altered layer is etched by immersing the substrate 12 in hydrogen fluoride or the like. Thereby, the through hole 20 can be formed in the substrate 12. In addition, the through holes 20 may be formed in the substrate 12 by a blasting process in which an abrasive is sprayed onto the substrate 12.

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

(Formation process of the penetration electrode 22, the 1st surface 1st conductive layer 31, and the 2nd surface 1st conductive layer 41)
FIG. 5 is a cross-sectional view illustrating the method for manufacturing the signal transmission board 10 according to the present embodiment subsequent to FIG. 4. After the through hole 20 is formed, 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 sputtering, vapor deposition, electroless plating, or the like.

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

  FIG. 7 is a cross-sectional view illustrating the method of manufacturing the signal transmission board 10 according to the present embodiment subsequent to 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 electrolytic plating using the resist layer 37 as a mask.

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

  FIG. 9 is a cross-sectional view illustrating 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 is 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.

(Formation process of the 1st surface 1st organic layer 34 and the 2nd surface 1st organic layer 42)
FIG. 10 is a cross-sectional view illustrating the method of manufacturing the signal transmission board 10 according to the present embodiment following FIG. After forming the penetration electrode 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 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 by, for example, exposure processing and development processing using a photosensitive film containing an organic material, or contain an organic material. The liquid to be formed may be applied by spin coating and dried. 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 first surface first organic layer. The elastic modulus may be smaller than 34.

(Formation process of the 1st surface 2nd conductive layer 33 and the 2nd surface 2nd conductive layer 43)
FIG. 11 is a cross-sectional view illustrating 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. 11, the first surface second including the signal layer 331 on the first surface first organic layer 34. 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. Similar to the first surface first conductive layer 31 and the second surface first conductive layer 41, 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. The seed layer 221 and the plating layer 222 may be formed by patterning. 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.

(Formation process of the 1st surface 2nd organic layer 36 and the 2nd surface 2nd organic layer 44)
FIG. 12 is a cross-sectional view illustrating the method for manufacturing the signal transmission board 10 according to the present embodiment subsequent to FIG. 11. After the first surface second conductive layer 33 and the second surface second conductive layer 43 are formed, the first surface first organic layer 34 or the first surface second conductive layer 33 is formed on the first surface second conductive layer 33 as shown in FIG. The one-surface second organic layer 36 is formed. In addition, 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 by, for example, exposure processing and development processing using a photosensitive film containing an organic material, or contain an organic material. The liquid to be formed may be applied by spin coating and dried.

  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 first surface second organic layer. The elastic modulus is smaller than 36. For example, the second surface second organic layer 44 is formed such that the difference between 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 a 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 is 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 illustrating a correspondence relationship between the temperature, the stress of the first insulating layer corresponding to the temperature, and the parameter correlated with the stress in the experimental example of the signal transmission board 10 according to the present embodiment. FIG. 14 is a diagram illustrating a correspondence relationship between the temperature, the stress of the second insulating layer corresponding to the temperature, and the parameter correlated with the stress in the experimental example of the signal transmission board 10 according to the present embodiment. In FIG. 13 and FIG. 14, the numerical value including “E” is obtained by multiplying the numerical value immediately before “E” by the numerical value obtained by the 冪 operation with 10 as the base and the numerical value immediately after “E” as the power index. It is a numerical value. For example, “6.01E + 05” in FIG. 13 is 6.01 × 10 ⁵ .

  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 second insulating layer was made of 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 curing temperature of the first insulating layer and the second insulating layer, that is, the temperature of thermosetting, 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 a 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. It was. Accordingly, at 25 ° C., the product difference 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 39.9 of the indentation elastic modulus and thickness of the second insulating layer and multiplying by 100, the percentage of the difference 2.9 is 7.27%, which is 15% or less. I want.

  As shown in FIGS. 13 and 14, the first insulating layer and the second insulating layer have a curing 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. The ratio of the difference of the product α × ΔT × E × h of the thermal expansion coefficient α, the temperature change ΔT with respect to the cure temperature, the elastic modulus E, and the thickness h is {(4.08E + 05-3). .84E + 05) /3.84+E05} × 100, resulting in 6.25%. The ratio denominator 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. 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, a stress. The stress at the cure temperature is zero. The ratio of 6.25% obtained from FIGS. 13 and 14 is a sufficiently low value when the ratio threshold is set to 15%.

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

  FIG. 15 is a perspective view of an indenter I that can be used for measurement of the indentation elastic modulus correlated with the stress 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. 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 board 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 represents the indentation depth of the indenter I, and the vertical axis represents 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 elastic modulus shown in FIGS. 13 and 14 can be measured by a nanoindentation test using a Barkovic 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, the indenter I attached to the transducer is pushed into the insulating layer placed on the 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 along a quadratic load curve A as the indentation depth h increases. Further, as shown in FIG. 16, the surface of the insulating layer is deformed from the initial surface to the surface at the time of load application by the indentation 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 pushing is completed, the pushing depth of the indenter I becomes the maximum value h _max and the load also becomes 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 unloading curve B that is steeper than the load loading curve A. Further, as shown in FIG. 16, due to elastic recovery accompanying unloading of the indenter I, the surface of the insulating layer is deformed from the surface at the time of loading to the surface after unloading. In addition, the surface after unloading exhibits a deformation trace that is recessed from the initial surface due to the influence of plastic deformation during loading. 16 and 17, the depth of the surface after unloading is h _f.

In the 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)
However, in Equation (1), V _S is the Poisson's ratio of the insulating layer. V _i is the Poisson's ratio of the indenter I. E _i is the elastic modulus of the indenter I. _Er is the decreasing elastic modulus of the indentation contact.

The decreasing elastic modulus _Er of the pushing contact in the equation (1) can be obtained by the following equation.
E _r = π ^1/2 / 2 CA _p ^1/2 (2)
In Equation (2), C is the slope dP / dh of the tangent line of the load unloading curve B at the maximum load value P _max shown in FIG. A _p is the projected area of the indenter I and the insulating layer are in contact.

_{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 Formula (3), h _max is the maximum value of the indentation depth described above. ε is a correction coefficient according to the geometric shape of the indenter I, and is 0.75 in the case of the diamond Vickers indenter. h _C is the intersection of the horizontal axis of the load unloading curve B tangent and 17 at the maximum value P _max of the load previously described.

  Hereinafter, the operation brought about by the present embodiment will be described.

  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. The second surface second organic layer 44 has a large thickness with respect to the first surface second organic layer 36 and a small elastic modulus.

  If only 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. In this case, the stress on the second surface 14 side due to the second surface second organic layer 44 is larger than the stress on the first surface 13 side due to the first surface second organic layer 36, and the second surface 14 where the stress is large. There is a possibility that the substrate 12 warps toward the side. On the other hand, in the present embodiment, the first surface 13 is formed by making the elastic modulus of the second surface second organic layer 44 having a large thickness smaller than the elastic modulus of the first surface second organic layer 36 having a small thickness. Both impedance matching and stress balance can be ensured between the side and the second surface 14 side. Thereby, the improvement of the transmission efficiency of a signal and suppression of the curvature of the board | substrate 12 can be made to make compatible.

  Further, in the present embodiment, improvement in signal transmission efficiency and suppression of warping 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 on 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 in position to the cross-sectional view of FIG. FIG. 19 is a 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 in position to the cross-sectional view of FIG.

  1 to 17, the first surface second conductive layer 33 forms 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. The example in which the two-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 a coplanar line on the first surface 13 side, and the second surface second conductive layer 43 is a coplanar on the second surface 14 side. Configure the track.

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

  According to the first modification, also 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 Since the two organic layers 44 have a larger 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. Can be secured. Thereby, the improvement of the transmission efficiency of a signal and suppression of the curvature of the board | substrate 12 can be made to make compatible.

(Second modification)
Next, a second modification example having a differential transmission line for transmitting one data with two signal lines will be described. FIG. 20 is a cross-sectional view on 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 in position to the cross-sectional view of FIG. FIG. 21 is a cross-sectional view on 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 in position to the cross-sectional view of FIG.

  So far, the example of the signal transmission board 10 provided with a single-ended coplanar line or strip line that transmits one data with 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 two signal layers 331 a and 331 b arranged at intervals in the width direction D2 and the signal layers 331 a and 331 b. And a ground layer 332 arranged at an interval outward 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 includes two signal layers 431a and 431b that are spaced apart in the width direction D2, and a width direction D2 with respect to the signal layers 431a and 431b. And a ground layer 432 that is spaced outward. Each of the two signal layers 431 a and 431 b is electrically connected to each of the two signal layers 331 a and 331 b via the through electrode 22. The two signal layers 431a and 431b transmit the same electrical signal as the electrical signal transmitted in each of the two signal layers 331a and 331b.

  According to the second modification, a signal waveform can be formed with a small voltage by having a differential transmission line. 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, it is possible to appropriately transmit a high-frequency electric signal as compared with the single-ended method. Further, according to the second modification, the wiring width W2 of the signal layers 431a and 431b on the second surface 14 is also the wiring width of the signal layers 331a and 331b on the first surface 13 in the differential transmission line. It is larger than W1, and the second surface second organic layer 44 has a larger thickness and smaller elastic modulus than the first surface second organic layer 36, so that it is between the first surface 13 side and the second surface 14 side. Thus, both impedance matching and stress balance can be ensured. Thereby, the improvement of the transmission efficiency of a signal and suppression of the curvature of the board | substrate 12 can be made to make compatible.

(Third Modification)
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 layers 311 includes the dielectric 32 positioned on the signal layer 311 and the first surface second conductive layer 33 positioned on the dielectric 32. , A capacitor 15 having an MIM (Metal-Insulator-Metal) structure is formed. The dielectric 32 contains, for example, 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 a microstrip line.

  Note that various modifications can be made to the above-described embodiment. Hereinafter, modified 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 parts in the above embodiment are used for the parts that can be configured in the same manner as in the above embodiment. A duplicate description is omitted. In addition, when it is clear that the operational effects obtained in the above-described embodiment can be obtained in the modified example, the description thereof may be omitted.

FIG. 23 is a diagram illustrating 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.

DESCRIPTION OF SYMBOLS 10 Signal transmission board | substrate 12 Board | substrate 331 Signal layer 34 1st surface 1st organic layer 351 Ground layer 431 Signal layer 44 2nd surface 2nd organic layer 451 Ground layer

Claims (12)

A substrate having a first surface and a second surface opposite the first surface;
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 larger dimension in the width direction intersecting 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 intersecting the first surface than the first insulating layer and having a small elastic modulus;
And a second ground layer located on the second insulating layer.   The difference between the product of the dimension in the thickness direction of the first insulating layer and the elastic modulus and the product of the dimension in the thickness direction of the second insulating layer and the elastic modulus is the dimension in the thickness direction of the second insulating layer. The signal transmission board according to claim 1 which has a ratio below a threshold to a product with elastic modulus.   The signal transmission board according to claim 2, wherein the threshold value is 15%.   The difference between the product of the coefficient of thermal expansion of the first insulating layer and the dimension in the thickness direction and the modulus of elasticity and the product of the coefficient of thermal expansion of the second insulating layer and the dimension in the thickness direction and the modulus of elasticity are the second The signal transmission board according to claim 2 or 3 which has a ratio below a threshold to a product of a coefficient of thermal expansion of an insulating layer, a size of a thickness direction, and an elastic modulus. 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;
And at least one fourth insulating layer located between the second surface and the second signal layer and at least one on the second ground layer,
The sum of the product of the dimension in the thickness direction of the first insulating layer and the elastic modulus, the product of the dimension in the thickness direction of the third insulating layer and the elastic modulus, and the dimension in the thickness direction of the second insulating layer and elasticity. The difference between the product of the modulus and the sum of the product of the dimension in the thickness direction of the fourth insulation layer and the modulus of elasticity is the product of the product of the dimension in the thickness direction of the second insulation layer and the modulus of elasticity and the fourth insulation. 5. The signal transmission board according to claim 1, wherein the signal transmission board has a ratio equal to or less than a threshold with respect to a sum of a product of a dimension in a thickness direction of the layer and an elastic modulus.   5. The semiconductor device according to claim 1, 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. A signal transmission board according to claim 1. A third ground layer located on the first surface and adjacent to the first signal layer in the width direction;
The signal transmission board 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.   8. The capacitor according to claim 1, 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. 9. The signal transmission board according to one item.   The signal transmission board according to any one of claims 1 to 8, wherein the board contains glass.   The signal transmission board according to claim 1, wherein the signal transmission board can be mounted on a wiring board on the second surface side, and an integrated circuit can be mounted on the first surface. Preparing a substrate having a first surface and a second surface opposite to the first surface;
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 electrically connected to the first signal layer and having 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 than the first insulating layer and having a low elastic modulus;
Forming a second ground layer on the second insulating layer. A method for manufacturing a signal transmission board. Forming the first insulating layer includes thermally curing the first insulating layer at a first temperature;
Forming the second insulating layer includes thermosetting the second insulating layer at the first temperature when thermosetting the first insulating layer;
At least in the temperature section from the first temperature to the second temperature after thermosetting, 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 modulus. The difference between the thermal expansion coefficient of the second insulating layer, the temperature change with respect to the first temperature, the product of the dimension in the thickness direction and the elastic modulus is the thermal expansion coefficient of the second insulating layer and the first temperature. The method of manufacturing a signal transmission board according to claim 11, wherein the ratio of the temperature change to the product of the thickness direction dimension and the elastic modulus has a ratio equal to or less than a threshold value.