JP4590722B2 - Substrate manufacturing method for mounting optical components - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical component mounting substrate on which an optical component is mounted, a mounting substrate in which an optical component or the like is mounted on the optical component mounting substrate, and a printed circuit board in which the mounting substrate is bonded via conductive bumps.
[0002]
[Prior art]
In order to make a computer that can perform arithmetic processing faster, the clock frequency of the CPU tends to increase more and more, and now the one of the order of 1 GHz has appeared. As a result, there is a portion where high-frequency current flows in the copper electrical wiring on the printed circuit board in the computer, so that malfunctions may occur due to the generation of noise, and electromagnetic waves may be generated, adversely affecting the surroundings. It will also be.
[0003]
In order to solve such problems, a part of the electrical wiring made of copper on the printed circuit board is replaced with an optical fiber or an optical waveguide (hereinafter referred to as an optical wiring), and an optical signal is used instead of the electrical signal. ing. This is because the generation of noise and electromagnetic waves can be suppressed in the case of optical signals.
[0004]
Generally, like an IC or the like, a photoelectric element such as a laser diode (LD) or a photodiode (PD) is mounted on a substrate surface, and signal transmission is performed on the substrate surface by a waveguide. In such an optical circuit, when the number of electrical components such as ICs increases, it is necessary to cross the optical waveguide, and there is a problem that the optical axis alignment between the optical waveguide and the photoelectric element becomes increasingly difficult. .
[0005]
More specifically, along with the practical application of optical communication systems through the development of low-loss optical fibers, development of various optical communication components is desired. And establishment of the optical wiring technique which mounts these optical components in high density, especially an optical waveguide technique is desired. In general, optical waveguides are required to satisfy the following conditions: (1) small optical loss, (2) easy manufacture, and (3) control of refractive index difference between core and clad. So far, quartz-based optical waveguides have been mainly studied as low-loss optical waveguides. As demonstrated by optical fibers, quartz has extremely good light transmission, so that a loss of 0.1 dB / cm or less is achieved even when a waveguide is used, and even when the wavelength is 1.3 μm. However, quartz has poor flexibility and needs to be produced on a silicon substrate or the like. If it is mounted on a printed circuit board as it is, there is a problem that connection of electric parts is greatly restricted.
[0006]
On the other hand, in recent years, an optical waveguide using a polymer among the optical waveguides has attracted attention because it may be manufactured at a low cost by a simple process. As an example, plastic optical waveguides such as polymethyl methacrylate (PMMA), polystyrene (PS), and polycarbonate (PC) achieve sufficiently low optical loss in the wavelength region longer than the visible wavelength compared to quartz optical waveguides. Although there are drawbacks such as not being performed, formation at a low temperature is possible and processing is easy. In the manufacturing method, a clad made of a low refractive index polymer material and a core layer made of a high refractive index polymer material are sequentially formed on a base material such as a silicon substrate, and a dry etching process is performed using the photoresist pattern as a mask. After the polymer core layer having a substantially rectangular cross section is processed in this way, a clad layer is formed on the upper portion again with a low refractive index polymer material to form an optical waveguide having a total film thickness of 30 to 60 μm.
[0007]
After the above process, the optical waveguide is peeled off from a base material such as silicon using hydrofluoric acid or the like, and bonded to the electric wiring board using an adhesive to produce an optical component mounting substrate.
[0008]
However, once the polymer optical waveguide is peeled off from a silicon substrate or the like to form a film, shrinkage occurs due to a difference in thermal expansion coefficient, and sufficient bonding accuracy to the electric wiring board cannot be obtained. In some cases, the refractive index fluctuates with a problem such as a crack due to a shrinkage factor, causing optical loss of the optical waveguide, and has not yet been put into practical use. In addition, the accuracy in the vertical direction when pasting to the electric wiring board is strict, and the same ± 1 μm or less as that of the optical component mounting is required, and the pasting is accompanied with great difficulty.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the state of the related art, and enables high-density mounting of an electrical component or an optical component on an optical waveguide, and easily realizes optical axis alignment between the optical waveguide and the optical component. An object is to provide an optical component mounting substrate and a printed board that can be used.
[0010]
One embodiment of the present invention is a method for manufacturing an optical component mounting substrate having at least one optical component mounting portion on one surface and an optical wiring layer on the other surface, and the photosensitive glass substrate is irradiated with ultraviolet rays. A step of forming a via hole penetrating the photosensitive glass substrate by performing exposure and heat treatment and development treatment by acid treatment; and filling one surface of the photosensitive glass substrate with a resin to smooth the one surface of the photosensitive glass substrate A step of applying an optical wiring material to the one surface of the photosensitive glass substrate in which the via hole is filled with the resin, and an optical wiring having a core and a clad by patterning the optical wiring material Forming a layer, forming an optical path conversion mirror in the optical wiring layer for optically coupling the optical component and the core of the optical wiring layer, and the optical wiring Heating the photosensitive glass substrate formed with a thermal decomposition of the resin filled in the via hole, forming a through hole in the optical wiring layer at a position corresponding to the via hole, and plating A conductor is deposited in the via hole and in the through-hole, and is formed on the other surface facing the one surface of the photosensitive glass substrate and on the one surface of the photosensitive glass substrate. By sufficiently growing the plating so as to protrude from any of the surfaces of the optical wiring layer, a pad connected to an optical component is formed on the other surface of the photosensitive glass substrate, and the optical wiring layer And a step of forming bumps on the surface of the optical component mounting substrate.
The photosensitive glass substrate preferably contains at least one material selected from the group consisting of Au and CeO2.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing an optical component mounting board and a mounting board according to the present invention. The optical component mounting substrate 10 of the present invention has at least an optical wiring layer composed of an optical component mounting portion on one surface of the glass substrate 1 and a core and a clad on the other surface, and is electrically connected to the optical component mounting portion. A via hole penetrating the substrate is provided. Further, an optical component 14 and an electrical component 15 are mounted thereon to form a mounting board. The mounting board (optical component mounting board 10) is connected to the printed board 20 shown on the lower side in the figure.
[0012]
More specifically, the optical component mounting substrate 10 uses the glass substrate 1 as a base material. At least an optical wiring layer composed of a core and a clad is formed on one surface of the glass substrate and an optical component mounting portion (pad, electrical wiring, etc.) on the other surface. Further, the glass substrate 1 is provided with a through hole 2. The inside of each hole 2 is filled with a conductor provided by plating, and a bump corresponding to the position of the electrode 21 of the printed wiring 20 is provided below. Thereby, the optical component, the electrical component, and the electrode on the printed wiring board 20 side can be electrically connected.
[0013]
By adopting this configuration, the process of peeling the optical waveguide to form a film is unnecessary, and the positional accuracy with respect to the electric wiring board is also improved. Further, when an optical component mounting portion is adopted on one surface of the opaque substrate and an optical wiring layer is formed on the other surface, an opening for allowing laser light to pass through the substrate between the optical component mounting portion and the optical wiring layer mirror is provided. Although it is necessary, in the case of the optical component mounting substrate of the present invention, it is not always necessary to provide an opening unless the glass substrate absorbs laser light.
[0014]
Next, a manufacturing method of the optical component mounting substrate 10 shown in FIG. 1 will be described. 2 to 10 are process diagrams showing the manufacturing process of the optical component mounting board 10. The optical component mounting (electrical wiring layer) forming surface in the explanation is a surface, and the bump and optical wiring layer forming surface is b surface.
[0015]
The glass substrate 1 is preferably a photosensitive glass plate having a chemical workability of Li ₂ O—Al ₂ O ₃ —SiO ₂ (Au, CeO ₂ ) system. Further, the a and b surfaces of the glass substrate 1 have excellent smoothness. The glass substrate was irradiated with 100 mJ / cm ^{2 of} a Hg—Xe lamp through a photomask having a hole shape (see FIG. 2) and developed. When the components Au and CeO ₂ in the photosensitive glass are exposed by ultraviolet irradiation, nuclei composed of particles of the photosensitive metal Au and CeO ₂ are formed in the exposed portion to form a latent image (not shown). it can.
[0016]
Thereafter, the glass on which the latent image has been formed by exposure is heat-treated at 550 ° C. to 620 ° C., thereby precipitating crystals that easily elute into the acid. By this heat treatment, lithium metasilicate crystals are precipitated with the photosensitive metal particles present in the exposed portion (latent image) as nuclei. The crystals thus obtained have a property of being easily dissolved in an acid, and thus were subjected to an acid treatment with dilute hydrofluoric acid and a development treatment (see FIG. 3).
[0017]
As a result of the above process, a via hole 2 is formed in the photosensitive glass substrate 1. The via hole is a hole that penetrates the photosensitive glass substrate 1 and is formed so as to coincide with the position of the electrode on the printed circuit board 20 side to be connected.
[0018]
The surface b of the photosensitive glass substrate 1 on which the via hole 2 is formed is filled with the via hole 2 with light or thermosetting resin 3 to make the surface b of the glass substrate 1 smooth, and then an optical wiring layer material ( The lower clad 4 and the core 5 are sequentially applied with polyimide, for example (see FIG. 4).
[0019]
Next, a photoresist 6 is applied to the upper portion of the optical waveguide material (see FIG. 5), exposed with a waveguide pattern mask, the photoresist 6 is developed, and the exposed portion is removed. Then, the core is patterned so that the cross section becomes rectangular by reactive ion etching, and then the photoresist 5 is removed.
[0020]
The core is formed to have at least one of a straight line, a curved line, an S-shaped curve, a parallel line, and the like.
[0021]
Further, a mirror 7 on which an Al film or the like is deposited is formed at a predetermined portion of the core wiring pattern, and an upper clad 8 is applied again to form an optical wiring layer 9 (see FIGS. 6 and 7). Before applying the upper clad, the mirror is processed to approximately 45 ° with respect to the core pattern by a laser or the like, and an Al film is selectively deposited. At this time, an alignment mark for mounting an optical component is formed at an arbitrary position on the lower clat with an Al film.
[0022]
Thereafter, a heat treatment process of the optical wiring layer is performed at about 350.degree. The resin filled in the via hole 2 is thermally decomposed and removed here (see FIG. 8). When the decomposition component of the resin remains in the hole, the organic residue can be removed with dichromic acid, permanganic acid or the like.
[0023]
The optical wiring layer is additionally processed in a blind via shape by laser irradiation or the like so as to match the position of the via hole 2 of the photosensitive glass substrate 1, and the via hole 2 is also formed on the optical wiring layer side. Then, the conductor is deposited in the via hole 2 by plating, and the plating is sufficiently grown so as to protrude from the surface of the glass substrate to form bumps 11 and pads 12 (see FIG. 9).
[0024]
When plating is performed, a low-viscosity adhesive layer is selectively applied only to the inner wall surface of the via hole 2, and a plating process is performed on the adhesive layer, so that the photosensitive glass interface and the plated metal film are removed. Adhesiveness can be further improved.
[0025]
An optical element (LD, PD), LSI chip, and the like on the optical component mounting substrate 10 manufactured as described above are relied on the alignment mark formed in the lower clad simultaneously with the mirror process so that the optical axis is not shifted. A mounting board is created by mounting on the board. Since the photosensitive glass substrate 1 has a smooth surface, the distance in the height direction from the alignment mark can be accurately grasped, so that the optical component is installed on the end face of the optical component mounting substrate 10 so that the optical axis is not shifted. Is also possible. Thereafter, the optical component mounting board 10 itself is connected to the printed board to complete the first example of FIG.
[0026]
Optical components such as PD / LD and electrical components such as LSI are connected to the wiring pattern on the optical component mounting board via lead wires or bumps. On the other hand, electrodes 21 for electrical connection with the bumps 11 of the optical component mounting substrate 10 are provided on the upper surface of the printed circuit board 20 and are connected to each other. As a result, optical components such as PD and LD and electrical components such as LSI and the printed circuit board 20 are electrically connected.
[0027]
Further, a part of the electrical signal from the printed circuit board 20 is converted into an optical signal by the LD, and the optical signal is incident on the waveguide. Then, the optical signal is reflected by the mirror and transmitted through the optical waveguide, reflected again by the mirror, converted into an electric signal by the PD, and signal processing is performed by an LSI or the like. Thus, electrical connection and optical connection can be realized with high reliability. A plurality of such optical component mounting boards may be mounted on a printed circuit board to enhance the optical communication device and the optical information device.
[0028]
FIG. 10 is a diagram showing a second example of the optical component mounting board and the printed board on which the mounting board of the present invention is mounted. This is an example where the optical component mounting portion is the electrical wiring layer 13 and has a multilayer structure.
[0029]
In the optical component mounting substrate 10 shown in this example, the via hole 2 of the photosensitive glass substrate 1 is filled with a conductive substance, and an electric wiring composed of a wiring electrode of the optical wiring layer and a metal material and an insulating material on the upper layer. The wiring electrode of the layer 13 is connected to the via hole 2 in correspondence with the electric wiring density of the electrode of the optical component or the electric component. Here, the electrical wiring layer 13 can be formed using a known additive method or subtract method.
[0030]
On the other hand, the position of the bump 11 from the via hole 2 formed on the surface of the glass substrate b is a position to be matched with the electrode 21 of the printed circuit board 20.
[0031]
The optical component mounting substrate 10 thus manufactured is used to mount optical elements (LD, PD), LSI (bare) chips, and the like on the top, and the optical component mounting substrate is connected to the printed circuit board. In this way, a part of the electrical signal from the printed circuit board 20 is converted into an optical signal by the LD, and the optical signal reflected by the mirror is transmitted through the optical waveguide. The optically transmitted signal is again converted by a mirror by 90 °, converted to an electric signal by a PD, and processed by an LSI or the like. Thus, electrical connection and optical connection can be realized with high reliability.
[0032]
Incidentally, in the optical waveguide, quartz, polycarbonate, polymethyl methacrylate, or a polymeric material composed of polystyrene, or _{SiO 2 - Ge 2, ZrF 4} - BaF 2 - GdF 3 - AlF 3, As- S, As- Even if it is configured by using either a glass system made of Ge-Se or the like, or a crystal system made of CsBr, KRS-5, or the like, the result is as shown in FIG.
[0033]
【The invention's effect】
The optical component mounting substrate of the present invention forms an optical wiring layer wired directly on a glass substrate. Therefore, the optical axis alignment between the optical component and the optical wiring layer is highly accurate. Further, since the optical wiring layer (waveguide film) is not peeled off, there is no change in various physical properties such as refractive index due to shrinkage. Furthermore, if the optical component mounting portion is an electrical wiring layer, it is possible to provide a mounting substrate that corresponds to the electrical wiring density of the optical component mounted on the optical component mounting portion and the electrodes of the electrical component, and via holes and conductive bumps can be provided. It can be connected to a printed circuit board with low wiring density via
[0034]
As described above, the connection characteristics and reliability of the optical waveguide as the transmission line are remarkably excellent, and the inexpensive and practical optical component mounting board and mounting board as well as the printed board with a high degree of freedom in wiring design. Can be provided.
[0035]
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an optical component mounting board, a mounting board, and a printed board according to the present invention.
FIG. 2 is an explanatory view showing a manufacturing process of an optical component mounting board.
FIG. 3 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 4 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 5 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 6 is an explanatory view showing a manufacturing process of an optical component mounting board.
FIG. 7 is a tilt view showing a manufacturing process of the optical component mounting board.
FIG. 8 is an explanatory diagram showing a manufacturing process of an optical component mounting board.
FIG. 9 is an explanatory diagram showing an optical component mounting board.
FIG. 10 is an explanatory view showing an optical component mounting board, a mounting board, and a printed board according to the present invention.
[Explanation of symbols]
1 ... Glass substrate 2 ... Hole (via hole)
DESCRIPTION OF SYMBOLS 3 ... Light or thermosetting resin 4 ... Lower clad 5 ... Core 6 ... Photoresist 7 ... Mirror 8 ... Upper clad 9 ... Optical wiring layer 10 ... Light Component mounting substrate 11 ... Bump 12 ... Pat 13 ... Electrical wiring layer 14 ... Optical component 15 ... Electrical component 20 ... Printed circuit board 21 ... Electrode

Claims (2)

An optical component mounting substrate manufacturing method comprising an optical component mounting portion on one surface of an photosensitive glass substrate and an optical wiring layer on the other surface, wherein the photosensitive glass substrate is exposed by ultraviolet irradiation, heat treatment and acid treatment A step of forming a via hole penetrating the photosensitive glass substrate by performing a development process, a step of filling one surface of the photosensitive glass substrate with a resin by filling the via hole with a resin, and the via hole. A step of applying an optical wiring material to the one surface of the photosensitive glass substrate filled with the resin, a step of patterning the optical wiring material to form an optical wiring layer having a core and a cladding, Forming an optical path conversion mirror in the optical wiring layer for optically coupling a component and the core of the optical wiring layer; and the photosensitive having the optical wiring layer formed thereon. Heating the glass substrate and thermally decomposing the resin filled in the via hole; forming a through hole in the optical wiring layer at a position corresponding to the via hole; and plating in the via hole and the through hole A conductor is deposited in the hole, and the other surface of the photosensitive glass substrate facing the one surface, and the surface of the optical wiring layer formed on the one surface of the photosensitive glass substrate, By sufficiently growing the plating so as to protrude from either, a pad connected to the optical component is formed on the other surface of the photosensitive glass substrate, and a bump is formed on the surface of the optical wiring layer. And a step of forming the optical component mounting substrate manufacturing method. The method for manufacturing a substrate for mounting an optical component according to claim 1, wherein the photosensitive glass substrate includes at least one material selected from the group consisting of Au and CeO 2.

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