JP5383348B2 - Electrical wiring board and optical module - Google Patents

Description

  The present invention relates to an electric wiring board having a through electrode and an optical module including the electric wiring board.

  In recent years, with the improvement of information processing capability of computers, in an integrated circuit (IC) such as a semiconductor large scale integrated circuit element (LSI, VLSI) used as a microprocessor, the degree of integration of transistors has been increased. The operating speed of the IC has reached the GHz level at the clock frequency. Along with this, there has been a demand for higher density and finer electrical wiring for electrically connecting electrical elements.

  As a technique for providing high-density electrical wiring, for example, as shown in Patent Document 1, providing a through electrode is disclosed.

JP 2000-340906 A

  However, in the technique disclosed in Patent Document 1, when heat is applied from the outside during use or the like, the through electrode is peeled from the dielectric layer due to the stress generated by the difference in thermal expansion between the wiring material and the dielectric layer. There was a case.

  An object of the present invention is to provide an electric wiring board and an optical module in which peeling of through electrodes is reduced.

An electrical wiring board according to an embodiment of the present invention includes a first dielectric layer, a second dielectric layer provided on the first dielectric layer, the first dielectric layer, and the A through electrode provided in a stacking direction of the first dielectric layer and the second dielectric layer so as to be in contact with the second dielectric layer, wherein the first dielectric layer and the first dielectric layer to be provided with a through electrode having a protruding portion that enters between the second dielectric layer,
The protrusion has an inclined surface that is inclined with respect to the interface between the first dielectric layer and the second dielectric layer .

  The thermal expansion coefficient of the first dielectric layer is preferably different from the thermal expansion coefficient of the second dielectric layer.

  The second dielectric layer is a core for transmitting light, and the first dielectric layer is a lower clad having a refractive index smaller than the refractive index of the core, and the periphery of the core It is preferable to further include an upper clad provided so as to be covered with the clad and having a refractive index smaller than that of the core.

  It is preferable that the through electrode further includes a second protrusion that enters between the core and the upper clad.

  An electrical wiring board according to an embodiment of the present invention includes the electrical wiring board, and a photoelectric conversion element that is optically coupled to the core portion and electrically connected to the through electrode.

  According to the present embodiment, the through electrode has a protruding portion positioned between the first dielectric layer and the second dielectric layer, so that the protruding portion fixes the through electrode to the dielectric layer. Thus, peeling of the through electrode from the dielectric layer can be suppressed. Furthermore, when the first dielectric layer and the second dielectric layer have different coefficients of thermal expansion, even if different thermal expansion changes occur in the first dielectric layer and the second dielectric layer due to heat, Since the protrusion is inserted between the one dielectric layer and the second dielectric layer, peeling of the through electrode from the dielectric layer can be sufficiently suppressed.

It is sectional drawing of the electrical wiring board of embodiment of this invention. It is a top view of the electrical wiring board of FIG. It is the elements on larger scale of the electrical wiring board of FIG. It is sectional drawing which shows the specific example of electrical wiring boards other than FIG. It is sectional drawing which shows the preparation process of the electrical wiring board of FIG. 4 (A). (A) shows the cross-sectional view of the optical module of embodiment of this invention, (B) shows sectional drawing which cut | disconnected B-B 'of (A).

  DESCRIPTION OF EMBODIMENTS Hereinafter, an electric wiring board according to an embodiment of the present invention will be described in detail with reference to the drawings. However, those drawings are only examples of the embodiments, and the present invention is not limited to them.

  FIG. 1 shows an opto-electric hybrid board that transmits light and electricity as an example of an electric wiring board according to an embodiment of the present invention. The opto-electric hybrid board in FIG. 1 includes a core 5 as a second dielectric layer, a lower cladding 4b as a first dielectric layer, a through electrode 2, an upper cladding 4a, a substrate 1 and an electrode 3.

  The through electrode 2 is provided on the electrode 3 in order to electrically connect the electrode 3 provided on the substrate 1 and the outside. The through electrode 2 is provided in the stacking direction of the lower clad 4 b and the core 5.

  The sectional view of the opto-electric hybrid board in FIG. 1 is obtained by cutting A-A ′ in the top view of the opto-electric hybrid board shown in FIG. 2. As shown in FIG. 2, when the through electrode 2 is viewed from the top, the center portion has a hollow shape. However, the through electrode 2 is not limited to this, and for example, the center is filled with a conductive paste or the like. Any configuration is acceptable.

  The through electrode 2 has a protruding portion 2a. The protrusion 2 a is provided so as to enter between the lower clad 4 b and the core 5. The protruding portion 2 a is provided between the lower clad 4 b and the core 5, so that the through electrode 2 can be fixed. Thereby, for example, an effect of suppressing peeling of the through electrode from the dielectric layer due to heat from the outside can be obtained.

  1 and 2 show an opto-electric hybrid board using a first dielectric layer and a second dielectric layer as a lower clad and a core, respectively, an electrical wiring according to an embodiment of the present invention. The substrate is not limited to this. For example, even when the first dielectric layer and the second dielectric layer are respectively build-up layers in the build-up substrate, the above-described effects can be obtained.

  In addition to the above-described effects, the following effects can be obtained when the electrical wiring board according to an embodiment of the present invention is the above-described opto-electric hybrid board.

  When light is transmitted from a photoelectric conversion element such as a light emitting element to the core, not all light can be transmitted to the core, and some light is introduced into the cladding. In this case, the light introduced into the cladding is emitted from the optical waveguide together with the light transmitted through the core, and it may be difficult to transmit an accurate optical signal. In addition, the light introduced into the clad may enter the core and be mixed into the optical signal in the core to inhibit the accurate transmission of the optical signal.

  However, by providing the protruding portion 2a between the core 5 and the lower clad 4b, it is possible to prevent the light transmitted by the clad from traveling and to suppress noise light caused by stray light in the clad of the optical waveguide. Further, by having the protruding portion 2a between the core 5 and the lower clad 4b, it is possible to shield the progress of light entering the core from the clad.

  Since the entrance of light from the clad 4b to the core 5 can be sufficiently shielded, the protrusion 2a may have inclined surfaces (2a1 and 2a2) that are inclined with respect to the interface X between the clad 4b and the core 5. preferable. The inclined surface includes an inclined surface 2a1 in contact with the core 5 and an inclined surface 2a2 in contact with the clad 4b.

  The inclination angle of the inclined surface 2a1 with respect to the interface X is preferably 0 to 90 °, and preferably 0 to 45 ° because peeling of the through electrode 2 is unlikely to occur and leakage of light from the core 5 to the outside can be sufficiently suppressed. Further preferred. In addition, the inclination angle of the inclined surface 2a2 with respect to the interface X is preferably 0 to 90 ° because leakage of light from the clad to the core can be sufficiently suppressed. In addition, these inclination | tilt angles mean the acute angle which the extended line (dotted line part of FIG. 3) of the interface X and the inclined surface make. FIG. 3 is a partially enlarged view of FIG.

  The angle formed between the inclined surface 2a1 and the inclined surface 2a2 is preferably 0 to 135 °. By being within the range of this angle, the penetration electrode 2 is hardly peeled off, and noise light propagating through the cladding can be sufficiently suppressed.

  As described above, the protruding portion 2a is not limited to that shown in FIGS. 1 and 3, and the protruding portions 2 a may be provided on both sides of the through electrode 2 as shown in FIG. 4A, for example. . Further, as shown in FIG. 4 (B), a second protrusion 2b may be further provided between the upper clad 4a and the core 5, and as shown in FIG. The protruding portion 2a and the second protruding portion may be provided on both sides of the electrode 2. The example of FIG. 4C is most preferable from the viewpoint of the effect of suppressing the peeling of the through electrode 2 and the effect of suppressing the leakage of light from the clad to the core.

  Each configuration will be described below.

(First dielectric layer and second dielectric layer)
Examples of the first dielectric layer and the second dielectric layer include an epoxy resin, an acrylic resin, and a polyimide resin. When the first dielectric layer and the second dielectric layer are a clad and a core, a photosensitive epoxy resin, acrylic resin, polyimide resin, or other resin that can be used for direct exposure, or a refractive index such as polysilane Examples include resins that can be used for the change method. In the direct exposure method, after the formation of the lower clad 4b, the core material is applied and the core 5 is formed by mask exposure, and the upper clad 4a is further applied and formed on the upper surface and side surfaces thereof to form an optical waveguide. It is a manufacturing method. In addition, the refractive index changing method is a method for performing UV irradiation on a portion other than the core portion by utilizing the characteristics of a polysilane polymer material or the like whose refractive index is lowered by UV (ultraviolet) irradiation. This is a method for producing an optical waveguide by lowering the refractive index of the optical waveguide.

  The core 5 and the upper cladding 4a and the lower cladding 4b are manufactured by a general optical waveguide manufacturing method. The cross-sectional size of the core is, for example, 35 to 100 μm square.

  The core has a higher refractive index than that of the cladding (preferably a relative refractive index difference of 1 to 3% with respect to the refractive index of the cladding) and can confine an optical signal.

(Penetration electrode)
The through electrode is formed by a plating method, a metal film deposition method, a conductive resin injection method, or the like. Especially, since the formation of the above-mentioned protrusion part 2a is easy, the plating method is preferable. When the smear that occurs during via hole processing is desmeared, the protruding portion 2a penetrates the boundary between the first dielectric layer and the second dielectric layer, so that the first dielectric layer A recess is formed between the second dielectric layer, and by plating from above, a metal enters the recess and a protrusion 2a is formed. The shape of the protrusion 2a can be selectively formed by adjusting the composition and flow rate of the roughening solution.

  An example of a method for manufacturing the electrical wiring board in FIG. 4A will be described below with reference to FIG. In FIG. 5A, an optical waveguide composed of a lower clad 4 b, a core 5, and an upper clad 4 a is formed on the electrode 3 of the substrate 1. Via holes 6 as shown in FIG. 5B are formed on the optical waveguide by processing using an excimer laser or a drill. The shape of the via hole 6 may be any of a substantially cylindrical shape, a substantially trapezoidal column, and a substantially inverted trapezoidal column.

  Next, the smear generated at the time of processing the via hole 6 is removed by performing a desmear treatment by a chromic acid method, a concentrated sulfuric acid method, an alkaline permanganate method, a plasma method, or the like. When the desmear process using 40-80 g / L permanganate is performed, the inner wall of the via hole 6 is also roughened at the same time, and the difference in etching rate between the lower clad 4b of the optical waveguide and the core 5 is shown in FIG. A recess 7 is formed in the via hole 6 as shown in c).

  Next, by adsorbing Pd on the surface and inner wall of the via hole 6 with a palladium-tin complex compound solution, electroless plating using a mixed solution of HCHO, NaOH, Rochelle salt, polyethylene glycol, etc. is performed. Copper plating 8 having a thickness of 0.3 to 3.0 μm as shown in FIG. 5D is formed on the upper surface of the optical waveguide and the inner wall of the via hole 6.

  Next, a resist layer 9 is formed on the upper surface of the optical waveguide by a lamination method or the like, and the resist layer 9 is patterned to form an opening on the upper surface of the via (FIG. 5E). Next, by subjecting the plating layer to electrolysis in a copper sulfate, sulfuric acid, chloride ion, or metallic copper solution, a copper plating having a thickness of about 0.1 to 10.0 μm is formed on the inner wall of the via hole 6 and the resist opening. Thereafter, the resist is removed, and unnecessary portions of electroless copper are removed by etching with plasma or the like, whereby the through electrode shown in FIG. 4A is formed.

  FIG. 6 shows an optical module in which a photoelectric conversion element is mounted by metal bumps or solder on the through electrode of the opto-electric hybrid board in FIG. In addition, although the light emitting element (surface emitting laser: VCSEL) 10 is illustrated as a photoelectric conversion element of FIG. 6, as a photoelectric conversion element, it is not limited to this, Light receiving elements, such as PD, can also be used.

  As shown in FIG. 6A, the light signal (arrow in the figure) emitted from the light emitting element 10 is converted in the traveling direction of light by the optical path conversion surface 12 so as to enter the core 5. The optical path conversion surface 12 changes the optical path direction of light by 90 degrees by an inclined surface inclined by 45 degrees with respect to the optical axis direction.

  The optical path conversion surface 12 has a high reflectivity with respect to light guided through the core 5 such as gold (Au), silver (Ag), platinum (Pt), aluminum (Al), copper (Cu), and the like. It is preferable that the film is formed on the surface.

  In the production of the optical path conversion surface 12, first, a groove structure having an inclined surface is produced for the core 5 by stamping, etching, dicing, laser processing, or the like. Then, a film having a high reflectance is formed on the inclined surface, and the optical path conversion surface 12 is manufactured by filling the groove structure with a high refractive index body having a higher refractive index than that of the lower cladding 4b and the upper cladding 4a. can do.

  An electrical connection portion 11 such as a solder ball is provided between the electrode 10 a of the light emitting element 10 and the through electrode 2. As the electrical connection portion 11, any conductive member suitable for high-speed signal transmission can be used. For example, a metal member such as gold, silver, or copper, and the form thereof is not limited to a ball, and may be a columnar shape or a bump shape.

  FIG. 6B shows a cross-sectional view of the optical module obtained by cutting the optical module shown in FIG. 6A along B-B ′.

  In FIG. 6B, one core 5 shows a structure sandwiched between two penetration electrodes 2. Usually, the light from the light emitting element 10 is reflected by the optical path conversion surface 12 and enters the core 5. At this time, part of the reflected light from the mirror may enter the cladding and become stray light. However, as shown in FIG. 6B, the presence of the protruding portion 2a can block entry into the cladding and reduce stray light.

  Since the left and right sides of the core 5 are sandwiched between the through electrodes 2, light incident at an angle larger than the numerical aperture (NA) of the optical waveguide is blocked, and crosstalk between adjacent cores is suppressed.

  The positional relationship between the core 5 and the through electrode 2 is not limited to the optical module shown in FIG. For example, a plurality of cores 5 arranged on the lower clad 4 b may be sandwiched between the two through electrodes 2.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

1: Substrate 2: Through electrode 2a: Protruding portion 3: Electrode 4: Cladding portion 4a: Upper cladding 4b: Lower cladding 5: Core 6: Via hole 7: Recessed portion 8: Copper plating 9: Resist 10: Light emitting element 10a: Light emitting element Electrode part 11: electrical connection part 12: optical path conversion surface

Claims (5)

A first dielectric layer;
A second dielectric layer provided on the first dielectric layer;
A through electrode provided in a stacking direction of the first dielectric layer and the second dielectric layer so as to be in contact with the first dielectric layer and the second dielectric layer, anda through electrode having a protruding portion that enters between the a first dielectric layer a second dielectric layer,
The protrusion, the electric wiring board to have a tilted inclined surface with respect to the interface between the first dielectric layer and the second dielectric layer.   The electrical wiring board according to claim 1, wherein a thermal expansion coefficient of the first dielectric layer is different from a thermal expansion coefficient of the second dielectric layer. The second dielectric layer is a core for transmitting light;
The first dielectric layer is a lower cladding having a refractive index smaller than that of the core;
The electric wiring board according to claim 1, further comprising an upper clad provided so as to cover the periphery of the core together with the lower clad and having a refractive index smaller than that of the core.   The electric wiring board according to claim 3, wherein the through electrode further has a second protrusion that enters between the core and the upper clad. The electrical wiring board according to claim 3 or 4 ,
A photoelectric conversion element optically coupled to the core and electrically connected to the through electrode;
An optical module comprising:

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