JP4742771B2 - Method for manufacturing photoelectric composite substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a photoelectric composite substrate having both an optical circuit and an electric circuit. Specifically, the present invention relates to a method for manufacturing a photoelectric composite substrate capable of easily and accurately mounting a photoelectric conversion element on a photoelectric composite substrate.

  In recent years, with the rapid widening of communication infrastructure and the dramatic improvement in information processing capability of computers and the like, there is an increasing need for information processing circuits having very high-speed information transmission paths. Under such circumstances, transmission by optical signal is considered as one means to break the limit of transmission speed of electric signal, and photoelectric composite substrate in which optical circuit is mixed with circuit substrate such as printed circuit board Has been developed. In the photoelectric composite substrate, an optical coupler such as a light deflection unit and a grating unit is formed, and an electrode pad (hereinafter referred to as an electrode pad) for mounting the photoelectric conversion device formed on the substrate with a photoelectric conversion device such as a laser diode or a photodiode. (Also referred to as a photoelectric conversion element mounting electrode pad), signal exchange is realized between the optical circuit and the electric circuit via the coupler.

  Usually, the electrode pad for mounting a photoelectric conversion element is formed by a method similar to the method of forming an electrode pad for mounting an electronic component on a printed wiring board.

  Specifically, after an electric circuit and a mounting land are formed on the substrate surface using a normal photoresist method, the photomask is aligned based on a reference point provided on the substrate, and the mask formed on the photomask An electrode pad for mounting a photoelectric conversion element is formed by forming a solder resist layer such as an ultraviolet curable resin film on the peripheral edge of the mounting land with a pattern.

  However, the photomask is aligned based on the reference point provided on the substrate, the electrode pad for mounting the photoelectric conversion element is formed using the photoresist method, and the optical waveguide is formed when mounting the photoelectric conversion element. The center of the light receiving and emitting part of the mounted photoelectric conversion element shifts due to the shrinkage of the resin caused by the heating process during the heating, the shrinkage of the resin substrate itself, or the misalignment during photomask alignment, so that light efficiently enters the optical waveguide layer. It was difficult to mount the photoelectric conversion element at a position where the light was emitted with high accuracy.

  As a technique for solving the above-described problem and mounting a photoelectric conversion element with high accuracy, Japanese Patent Application Laid-Open No. H10-228688 discloses that a mask pattern is aligned based on a positional relationship between an alignment mark on a substrate and a light deflection unit. A method of forming a circuit by forming a solder resist layer is disclosed.

However, since the circuit is also formed by a photomask by the above method, a shift of the photomask itself occurs, and it is difficult to form a photoelectric conversion element mounting electrode pad with high accuracy. When light emitted from the photoelectric conversion element is incident on the light deflection unit, or when light emitted from the light deflection unit is emitted to the photoelectric conversion element, an optical axis shift of about several tens of μm occurs, and the optical circuit and the electric circuit are There was a problem of causing excessive leakage loss in the signal exchange.
JP 2005-17394 A

  The present invention has been made to remedy the above problems, and eliminates the problem caused by the positional deviation of the electrode pad for mounting a photoelectric conversion element that occurs when a solder resist layer is formed using a photomask. Provided is a method for manufacturing a photoelectric composite substrate, in which the conversion element and the optical axis of the light deflection unit on the photoelectric composite substrate can be aligned with high accuracy and high-efficiency optical circuit-electric circuit coupling can be realized by passive alignment. It is for the purpose.

  In order to achieve the above object, a method for manufacturing a photoelectric composite substrate according to claim 1 of the present invention includes an optical waveguide layer having an optical waveguide provided with an optical light deflecting section, and has solder bumps on the substrate surface. A method for manufacturing a photoelectric composite substrate on which a photoelectric conversion device mounting electrode pad for mounting a photoelectric conversion device is formed, the step of covering a mounting land previously formed on the substrate surface with a solder resist, on the light deflection unit A step of setting a reference point on the photoelectric conversion element from the reference point on the solder resist so that the center of the light receiving and emitting part of the photoelectric conversion element overlaps the light deflection part when the photoelectric conversion element is mounted A step of specifying the coordinates of the center of the mounting electrode pad, opening a part of the solder resist on the basis of the specified coordinate, exposing the mounting land, and forming the electrode pad for mounting the photoelectric conversion element Characterized in that it comprises the step of.

  Moreover, the manufacturing method of the photoelectric composite substrate concerning Claim 2 of this invention is the manufacturing method of the photoelectric composite substrate of Claim 1, When the said photoelectric conversion element is mounted, the center of the light receiving / emitting part of a photoelectric conversion element The step of identifying the coordinates of the center of the electrode pad for mounting the photoelectric conversion element from the reference point on the solder resist so as to overlap the light deflection section is the center of the light receiving and emitting section of the mounted photoelectric conversion element The coordinate of the center of the solder bump forming electrode pad included in the photoelectric conversion element is specified, and the manufacturing method of the photoelectric composite substrate is performed using the specified coordinate.

  A method for manufacturing a photoelectric composite substrate according to claim 3 of the present invention is the method for manufacturing a photoelectric composite substrate according to claim 1 or 2, wherein a part of the solder resist is formed with reference to the specified coordinates. The step of forming the electrode pad for mounting the photoelectric conversion element by opening and exposing the mounting land is performed by laser processing.

  By using the method for manufacturing a photoelectric composite substrate according to claim 1, the photoelectric conversion element and the optical axis of the optical deflection portion of the photoelectric composite substrate can be aligned with high accuracy, and therefore, a highly efficient optical circuit-electric circuit. A photoelectric composite substrate capable of easily realizing inter-bonding is obtained.

  In addition, by using the method for manufacturing a photoelectric composite substrate according to claim 2, the photoelectric conversion element is formed on the basis of accurate coordinates based on the arrangement of the light receiving and emitting portions of the photoelectric conversion element and the solder bump forming electrode pads of the photoelectric conversion element. Since it can be mounted, a photoelectric composite substrate in which the photoelectric conversion element and the optical axis of the light deflection portion of the photoelectric composite substrate are aligned with high accuracy can be easily obtained.

  Further, by using the method for manufacturing a photoelectric composite substrate according to claim 3, the photoelectric conversion element mounting electrode pad can be formed without applying mechanical stress to the substrate. A photoelectric composite substrate capable of aligning the optical axis with high accuracy is obtained.

  The photoelectric composite substrate manufacturing method of the present invention includes an electrode pad for mounting a photoelectric conversion element for mounting a photoelectric conversion element having an optical waveguide layer having an optical waveguide having an optical deflection portion and having a solder bump on the substrate surface. Is a method of manufacturing a photoelectric composite substrate in which a mounting land previously formed on a substrate surface is covered with a solder resist, a step of setting a reference point on the light deflection unit, and the photoelectric conversion element is mounted. Specifying the coordinates of the center of the electrode pad for mounting the photoelectric conversion element from the reference point on the solder resist so that the center of the light receiving and emitting part of the photoelectric conversion element overlaps the light deflection unit, A step of opening a part of the solder resist on the basis of the coordinates and exposing a mounting land to form an electrode pad for mounting a photoelectric conversion element.

  An example of an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic cross-sectional view of an example of a photoelectric composite substrate according to the present invention having a photoelectric conversion element mounted on the surface thereof.

  In FIG. 1, 1 is an optical waveguide layer, 2 is an electric circuit layer, 3 is an optical waveguide, 4 is an optical deflection unit, 5 is a photoelectric conversion element, 6 is a solder bump, 7 is a mounting land, 8 is a solder resist, and 9a and 9b are An electric circuit, 10 is a photoelectric composite substrate, 11 is an electrode pad for mounting a photoelectric conversion element, 5a is a light emitting / receiving section of the photoelectric conversion element 5, and 5b and 5c are solder bumps provided in the photoelectric conversion element 5. Electrode pads (hereinafter also referred to as solder bump forming electrode pads).

  The light emitting / receiving section is a portion that becomes a light input / output path of the photoelectric conversion element, and the solder bump forming electrode pad means an electrode pad for forming a solder bump provided in the photoelectric conversion element.

  A photoelectric conversion element 5 is mounted on the surface of the photoelectric composite substrate 10 as shown in FIG. 1. The photoelectric conversion element 5 converts electric and optical signals, and the optical waveguide 3 provided on the photoelectric composite substrate 10. Alternatively, signal transmission is performed by the electric circuit 9a or the like.

  Input / output of optical signals to / from the optical waveguide layer 1 is performed through the light receiving / emitting unit 5 a of the photoelectric conversion element 5 mounted on the surface of the photoelectric composite substrate 10. Examples of the photoelectric conversion element 5 include light emitting elements such as laser diodes and LEDs, and light receiving elements such as photodiodes and phototransistors.

  As a method for manufacturing a photoelectric composite substrate according to the present invention, for example, JP-A-2004-341454 and JP-A-2004-163914 except for a portion described later for forming a photoelectric conversion element mounting electrode pad. Conventionally known methods for manufacturing a photoelectric composite substrate as described in the above can be used.

  An example of the manufacturing method will be described below with reference to FIGS.

  First, the process of forming the optical waveguide layer 1 will be described (FIGS. 2A to 2F).

  For the formation of the optical waveguide layer 1, a method for forming an optical waveguide layer that has been conventionally used in a method for manufacturing a photoelectric composite substrate is used without any particular limitation, and specific examples include the following methods. .

  That is, after forming the first transparent material layer 12 on the metal foil 101 (FIG. 2A), varnish for forming the second transparent material layer 13 is applied to form the optical waveguide 3. (FIG. 2 (B)). Then, after the varnish is heated and dried, only the portion where the optical waveguide 3 is to be formed is exposed and cured by the photomask 111 having a slit for forming the optical waveguide 3, whereby the optical waveguide 3 is formed ( FIG. 2 (C), (D)).

  As the metal foil 101, a copper foil, an aluminum foil, a nickel foil or the like having a thickness of about 9 to 70 μm is used.

  The metal foil 101 is preferably provided with a reference mark serving as a positioning reference when aligning each photomask described later.

  When the first transparent material layer 12 is formed on the metal foil 101, the metal foil 101 is a metal plate, a resin plate, or a ceramic on the surface opposite to the surface on which the first transparent material layer 12 is formed. It is preferable to fix to a rigid support such as a plate with an adhesive or the like in order to improve handling.

  As a method for forming the first transparent material layer 12 on the metal foil 101, a method of applying a transparent material varnish or the like on the metal foil 101 and curing it is used.

As the transparent material used for forming the first transparent material layer 12, various transparent materials are used regardless of inorganic or organic. For example, inorganic materials such as SiO ₂ and Al ₂ O ₃ , and (meth) acrylic materials are used. Transparent resin materials such as resin, polycarbonate resin, epoxy resin, and polyimide resin are used.

  As a method for applying the transparent material varnish onto the metal foil 101, a spin coating method, a roll transfer method, a spray method, or the like is used. A roll transfer method or a spin coating method can be used to form a uniform film thickness. It is preferable from the viewpoint that it can be applied.

  Next, a second transparent material layer 13 is formed on the formed first transparent material layer 12 (FIG. 2B).

  The second transparent material layer 13 forms a second transparent material component having a refractive index after curing different from that of the first transparent material layer 12 on the surface of the first transparent material layer 12.

  As a component for forming the second transparent material layer 13, various transparent materials similar to the various transparent materials used for forming the first transparent material layer 12 are used, but the refractive index after curing as described above. However, it is necessary to use a material having a refractive index different from that of the first transparent material layer 12. The optical waveguide layer must be transparent at the frequency of light to be transmitted, and usually two transparent materials, a material with a high refractive index (high refractive index material) and a material with a low refractive index (low refractive index material). Made of material. When light is incident on a waveguide made of a high refractive index material, only those satisfying the total reflection condition at the interface with the low refractive index material are reflected 100%, and the light is confined only to the waveguide made of the high refractive index material. . Therefore, light can be propagated in a desired direction by forming a waveguide using such materials having different refractive indexes.

  The second transparent material layer 13 is formed by forming the first transparent material layer 12 with, for example, a varnish-like photocurable resin for forming the transparent material layer 13 on the surface of the first transparent material layer 12. It is formed by applying the same method as above, followed by heating and drying.

  Next, the optical waveguide 3 is formed by selectively exposing and curing the second transparent material layer 13 using a photomask 111 in which slits are formed only in a portion where the optical waveguide 3 is to be formed. (FIGS. 2C and 2D).

  In addition, on the 2nd transparent resin layer 13, in order to protect the transparent resin layer 13, it is preferable to affix a transparent protective sheet, for example, a PET sheet etc. as needed. Since the protective sheet is transparent, it can be exposed by contacting a photomask on the protective sheet. Such a protective sheet is peeled off after exposure.

  The photomask 111 is placed in alignment by aligning with a reference mark provided on the photomask 111 using a reference mark or the like provided on the metal foil 101 in advance as a reference.

  Then, only the selectively exposed portion of the photocurable resin is cured to form the optical waveguide 3.

  Next, the light deflection section 4 is formed in the optical waveguide 3 (FIG. 2E).

  The light deflecting unit 4 changes the traveling direction of the light emitted from the photoelectric conversion element 5 so that the light propagates through the optical waveguide 3, or changes the traveling direction of the light traveling straight while being refracted in the optical waveguide 3. The photoelectric conversion element 5 as a light receiving element has a function of changing the direction of light so as to be received. The light deflection unit 4 is generally formed with an inclination of 45 °, and 90 ° reflection is used.

  The method for forming the light deflection unit 4 is not particularly limited. For example, various methods such as a method of cutting into a V shape by a dicing blade, a method of ablation processing using ultraviolet laser light, or a method of transferring using a mold are used. A method is mentioned.

  In addition, it is preferable that a metal thin film is formed on the surface of the light deflection unit 4 in order to increase reflection efficiency.

  As a method for forming the metal thin film, for example, a paste containing metal particles such as silver paste is applied to the surface of the light deflection unit 4 by a printing method, or selectively applied to the surface of the light deflection unit 4 by metal vapor deposition or sputtering. Examples include a method of depositing a metal. As the metal forming the metal particles, a highly reflective metal such as silver, gold, or aluminum is used.

  Next, a portion (non-exposed portion) 131 not exposed by the photomask 111 of the second transparent material layer 13 is removed by solvent cleaning. The solvent used for the solvent cleaning is not particularly limited as long as it is a solvent that selectively dissolves only the non-exposed area.

  Then, an optical waveguide layer 1 is formed by further forming a transparent material layer similar to the first transparent material layer 12 on the formed optical waveguide 3 (FIG. 2F).

  The method for forming the transparent material layer at this time can be the same as the method for forming the first transparent material layer 12.

  Then, the formed optical waveguide layer 1 is laminated with the electric circuit board 16 via the adhesive layer 15 (FIG. 2G).

  The adhesive layer 15 is provided on the surface opposite to the surface of the optical waveguide layer 1 on which the metal foil 101 is stretched.

  As the adhesive layer 15, for example, a method of providing a prepreg as used in the manufacture of a printed wiring board by sandwiching it between the optical waveguide layer 1 and the electric circuit board 16 and bonding them by a lamination molding process, Examples thereof include a method in which a two-component epoxy adhesive, an acrylic adhesive, or the like is applied, and the optical waveguide layer 1 and the electric circuit board 16 are bonded to each other and cured by pressurization and heating.

  And the optical waveguide layer 1 and the electric circuit board | substrate 16 are bonded together through the contact bonding layer 15 in this way (FIG.2 (H)).

  In addition, it is preferable from the point which densifies the photoelectric composite board | substrate obtained by the manufacturing method of this invention that the electric circuit board | substrate 16 has at least one or more electric circuits formed in the surface or inner layer.

  As shown in FIG. 2H, the metal foil 101 is exposed on the surface of the substrate where the optical waveguide layer 1 is bonded to the electric circuit substrate 16 in this manner.

  Next, by etching the metal foil 101 using a known photoresist method for forming an electric circuit, the electric circuit 9a and the mounting land 7 are formed at desired positions (FIGS. 3A and 3B). B)).

  That is, a photosensitive resist is applied to the surface of the metal foil 101, exposed through a photomask 112 having a light-transmitting portion for forming a desired pattern, developed, and then etched to etch the electric circuit 9a. And the mounting land 7 can be formed (FIG. 3B).

  As shown in FIG. 4, the photomask 112 has solder bump forming electrode pads 5 b that the photoelectric conversion elements 5 have a positional relationship between the center points of the openings 31 and 32 for forming the mounting lands 7. It is preferable to design so as to match the positional relationship between the center points of 5c as much as possible.

  The size of the mounting land 7 is a range in which an interval at which insulation with the adjacent mounting land or electric circuit can be maintained is ensured because the portion where the photoelectric conversion element is finally mounted is accurately positioned by the opening. In order to increase the correction margin at the time of opening, the larger one is preferable. Specifically, for example, the interval for maintaining the insulating property is preferably an interval of 20 μm or more.

  Furthermore, as shown in FIG. 5, the size of the mounting land 7 adjacent to the light deflecting unit 4 on the substrate is the center point of the mounting land 7 and a reference point set on the light deflecting unit 4 to be described later. It is preferable that the mounting land 7 is formed to be as large as possible in a range in which the mounting land 7 does not overlap the deflecting portion 4 in the direction of the line segment connecting the two.

  Specifically, for example, as shown in FIG. 5, the centers 51 and 52 of the solder bump forming electrode pads 5b and 5c and the centers of the openings 31 and 32, and the light emitting and receiving unit 5a and the photomask 112 are placed on the substrate. When it is assumed that the reference point equivalent point 4a on the photomask that overlaps with the reference point of the light deflection unit 4 is accurately positioned, the contours of the solder bump forming electrode pads 5b and 5c and the light emitting / receiving unit 5a It is preferable that the mounting land be formed as large as possible with the vicinity of the midpoint of the line segments c1 and c2 connecting the points on the contour closest to the contour of the contour.

  One or a plurality of mounting lands 7 are formed according to the number of solder bumps formed on the photoelectric conversion element 5.

  When the center of the mounting land 7 to be formed and the center of the electrode pads 51 and 52 for forming the solder bumps of the photoelectric conversion element 5 are overlapped with each other, the photomask 112 overlaps the center of the light receiving and emitting unit 11 and the light deflecting unit 4. It is preferable that the central portion is formed so as to overlap.

  For example, it is preferable that alignment is performed by means such as aligning the reference mark 112 formed in advance on the photomask 112 formed as described above with the reference mark provided in advance on the metal foil 101 or the like.

  The mounting land 7 thus formed is then covered with a solder resist forming layer 21 (FIG. 3C).

  Examples of the resin used for forming the solder resist forming layer 21 include various curable resins including a photo-curable epoxy resin conventionally used as a solder resist resin in the field of printed wiring boards and the like. Examples thereof include curable resins such as trade name DSR-2200KP 19 which is a two-component photocurable resin manufactured by Tamura Kaken Co., Ltd. and trade name SR9000W of Hitachi Chemical Co., Ltd.

  The solder resist 8 can be formed by a known method such as a printing method or a photographic method using a photomask 113 formed so as to expose only a portion of the solder resist forming layer 21 where the solder resist 8 is to be formed. .

  The photomask 113 is also preferably aligned by means such as aligning a reference mark provided in advance on the metal foil 101 with a reference mark provided in advance on the photomask 113.

Then, the solder resist 8 is formed by removing unexposed portions of the solder resist forming layer 21 that have not been exposed by washing with an alkaline developer such as an aqueous Na ₂ Co ₃ solution (FIG. 3). (D)).

  The thickness of the solder resist 8 formed in this way is preferably about 10 to 40 μm, more preferably about 10 to 20 μm. If the film thickness is too thin, there is a tendency that voids such as pinholes are likely to occur in the solder resist 8, and if it is too thick, the processing depth required for opening described later becomes too deep, There is a tendency for errors to occur easily when opening.

  Next, the process of forming the photoelectric conversion element mounting electrode pad will be described.

  In the manufacturing method of the present invention, a reference point is set on the light deflection unit, and the positional relationship between the center of the light emitting / receiving unit of the photoelectric conversion element specified in advance based on the reference point and the electrode pad for solder bump formation is shown. The position of the electrode pad for mounting the photoelectric conversion element on the substrate and the electrode pad for forming the solder bump of the photoelectric conversion element to be mounted is accurately determined by opening the solder resist and forming the electrode pad for mounting the photoelectric conversion element based on the coordinate information. The photoelectric conversion element can be mounted with high accuracy. As a result, since the optical axis of light reception / emission of the photoelectric conversion element can be accurately input / output to / from the optical deflection unit, highly efficient coupling between the optical circuit and the electric circuit can be realized.

  Based on the positional relationship between the center of the light receiving / emitting part of the photoelectric conversion element 5 and the solder bump forming electrode pad 5, the coordinates of the center of the electrode pad for mounting the photoelectric conversion element from the reference point on the light deflection part on the solder resist 8 are obtained. The process to specify is demonstrated.

  6A is a schematic plan view showing the arrangement of the light emitting / receiving portion 5a and the solder bump forming electrode pads 5b and 5c of the photoelectric conversion element 5 mounted on the photoelectric composite substrate 10, and FIG. A schematic plan view showing the arrangement of the mounting lands 7, the optical waveguide 3, and the optical deflection section 4 is shown. In addition, in order to simplify description, illustration of the formed electric circuit etc. is abbreviate | omitted in FIG.

First, as shown in FIG. 6A, for example, in the photoelectric conversion element 5, two-dimensional coordinates (x _n) are set at the center point of each solder bump forming electrode pad when the center 53 of the light emitting / receiving portion 5a is the origin. , Y _n ). Here, n is the number of solder bump forming electrode pads used for mounting the photoelectric conversion element 5, and when the solder bumps are formed on the solder bump forming electrode pads and used for mounting, n coordinates are given. . FIG. 6A shows a case where n = 2.

Note that the coordinates are preferably three-dimensional coordinates (x _n , y _n , z _n ) when higher-precision mounting is required.

  The above-mentioned coordinates are preferably given by actual measurement using a tool microscope or a three-dimensional dimension measuring instrument equipped with an optical microscope or a CCD camera and a table stage that can set and measure at least a two-dimensional coordinate system. When the dimensional accuracy of the photoelectric conversion element 5 is high, it may be derived from the design value of the photoelectric conversion element 5.

  Next, a reference point is set on the light deflection unit 4 of the photoelectric composite substrate 10.

  Since the optical deflection unit 4 can be observed from the side of the substrate on which the photoelectric conversion element 5 is mounted (hereinafter also referred to as the upper side), the reference point is set from the upper side of the substrate by the tool microscope, the three-dimensional dimension measuring instrument, or the like. .

  Normally, the light deflection section 4 is formed with an inclination of about 45 degrees, so that when the optical waveguide 3 is square, the observed shape is square as shown in FIG. Accordingly, the reference point can be set by specifying the center of gravity or vertex, the intersection of diagonal lines, the midpoint of the side, or a virtual point calculated from geometric optical calculation. If it is a point which can be specified, it will not specifically limit.

  Then, coordinates indicating the positional relationship between the center point of the light emitting / receiving unit of the photoelectric conversion element from the reference point set on the light deflection unit of the photoelectric composite substrate and the center point of each of the electrode pads for forming the solder bumps are solder resists. Identify above.

  This process will be described more specifically.

  In FIG. 6B, as an example, the light deflection unit 4 formed on the photoelectric composite substrate 10 is observed, and an intersection of square diagonal lines on the light deflection unit 4 is set as a reference point 151.

  First, the coordinates of the center point of each solder bump forming electrode pad from the reference point 151 are specified.

  The coordinates are specified by the center of the light receiving and emitting part of the photoelectric conversion element 5 and the reference point 151 on the photoelectric composite substrate 10, and each solder bump forming electrode pad on the photoelectric conversion element 5 and each solder bump forming electrode. The mounting land covered with the solder resist formed so as to correspond to the pad is specified so as to overlap.

  Then, by opening the vicinity of the coordinates with the specified coordinates as a reference, a photoelectric conversion element mounting electrode pad is formed with high accuracy on the photoelectric composite substrate (FIG. 3E).

  The opening can be performed by a conventionally known NC control device provided with an observation device such as a CCD camera and a coordinate storage device, and a mechanism capable of controlling the coordinate system and processing to a specified position with high accuracy.

  In general, the processing position accuracy is preferably a processing accuracy of 10 μm or less from the viewpoint of the amount of positional deviation that can be permitted in order to efficiently input and output light.

  Examples of the opening means include a method of evaporating the solder resist using a laser, or a method of mechanically cutting the solder resist layer. In the case of opening using a laser, it is more preferable because the processing accuracy is higher and mechanical stress is not applied to the substrate.

As a laser used in the method of evaporating the solder resist layer using the laser, an ultraviolet laser typified by an excimer laser of KrF or ArF, an infrared laser typified by an Nd-YAG or CO ₂ laser, or the like can be used. .

  As a method for mechanically cutting the solder resist layer, there is a method using drilling. At this time, it is preferable to flatten the tip to match the pad diameter. In order not to damage the metal foil, it is preferable to control the cutting depth to 1 μm or less.

  The size of the diameter of the opening hole formed in this way cannot be specified because the optimum dimension is determined by the size of the electrode pad for forming a solder bump, but is usually not the same as the diameter of the electrode pad for forming a solder bump. In other words, it is preferably formed to have an area of about ± 5%. If the difference in size is large, the solder shape after reflow becomes distorted, and the positional relationship between the center points between the two pads tends to be shifted.

  Thus, by forming the photoelectric conversion element mounting electrode pad using the point on the light deflection unit 4 as a coordinate reference, a photoelectric composite substrate on which the photoelectric conversion element can be mounted with high accuracy is obtained. In such a photoelectric composite substrate, the electrode pads for mounting the photoelectric conversion elements are formed with high precision. Therefore, the solder bumps are formed on the electrode pads for forming the solder bumps of the photoelectric conversion elements 5, and the solder bumps are mounted on the predetermined photoelectric conversion elements. The photoelectric conversion element 5 can be accurately mounted at a position where the photoelectric conversion efficiency is high by placing it in accordance with the electrode pad for use and using it in a reflow solder bath (FIG. 3 (F)).

  Therefore, the device obtained by mounting the photoelectric conversion element on the photoelectric composite substrate obtained by the manufacturing method of the present invention is a device with small optical loss.

  Even during mass production, since a highly accurate mounting pad can be formed in advance, high precision mounting can be achieved with an easy manufacturing process in that a process such as active alignment is not required.

  The present invention will be described in more detail with reference to examples. In addition, this invention is not limited at all by the Example.

  In this embodiment, a surface emitting laser diode (VCSEL) is used as the photoelectric conversion element.

  The VCSEL used was a flip-chip type VCSEL (ULM850-05-TT-U0101U / ULM Photonics). The emission current was 3.2 mA when the applied current value for obtaining an output of 1 mW at 850 nm was measured. The light emitting part diameter was 10 μmφ.

  As electrode pads for forming VCSEL solder bumps, circular electrode pads 61 and 62 (D50 Pad) of 50 μmφ arranged as shown in FIG. 7 were used.

  Further, in FIG. 7, the μm display of the circular electrode pad 61 when one side of the contour of the VCSEL is set as the reference of the X axis and the coordinates are set on the VCSEL with the center point of the light emitting unit 63 as the origin (0, 0). The coordinates of the circular electrode pad 62 are (72.5, 72.5) based on (72.5, -72.5), and the center of the electrode pads 61, 62 from the center of the light emitting part 63 The distance to the point was 102.5 μm. The coordinates and distance were measured with MEASURING MICROSCOPE: MM-40 manufactured by Nikon Corporation.

Example 1
First, a substrate provided with an optical waveguide layer as described below was produced by the method described in JP-A-2004-341454.

(raw materials)
Transparent material A used in the following is 100 parts by mass of product name “BPAF-DGE” manufactured by Tohto Kasei Co., Ltd., 66 parts by mass of product name “B650” manufactured by Dainippon Ink Industries, Ltd., manufactured by San Apro Co., Ltd. Is a thermosetting epoxy resin consisting of 2 parts by mass of the trade name “SA-102”. When the transparent material A is cured by heating at 100 ° C. for 1 hour and further at 150 ° C. for 1 hour, the refractive index is 1.51.

Moreover, as a varnish of transparent material B, Daicel Chemical Industries Co., Ltd. trade name “EHPE-3150” 100 parts by mass, methyl ethyl ketone 70 parts by mass, toluene 30 parts by mass, Rhodia Japan Co., Ltd. trade name “Lordsil Photoinitiator” 2074 "is a varnish obtained by mixing 2 parts by mass. The transparent material B varnish is dried to remove the solvent, cured by irradiation with a high-pressure mercury lamp with a power of 10 J / cm ² , and then cured at 150 ° C. for 1 hour, the refractive index of the cured resin is 1. .53.

  Furthermore, as a varnish of adhesive C, Toto Kasei Co., Ltd. brand name "YDB500" 90 mass parts, Toto Kasei Co., Ltd. brand name "YDCN-1211" 10 mass parts, Dicyandiamide 3 mass parts, Shikoku Kasei ( The varnish which consists of 0.1 mass part of brand name "2E4MZ" manufactured by Co., Ltd., 30 mass parts of methyl ethyl ketone, and 8 mass parts of dimethylformamide was used.

(Manufacture of substrates)
Using a 35 μm thick copper foil (trade name “MPGT” manufactured by Furukawa Electric Co., Ltd.) as a metal layer, transparent material A is applied to the metal layer by a roll transfer method to a coating thickness of 50 μm, followed by 100 hours at 100 ° C. A transparent material layer was formed by heating at 150 ° C. for 1 hour to cure.

  Next, a transparent material B varnish is applied on the transparent material layer to a thickness of 80 μm and dried by heating to form a photosensitive transparent material layer having a thickness of 40 μm, and a transparent PET film having a thickness of 25 μm is formed thereon. The cover film was pressed with a roll and pasted to obtain a laminate. Then, the laminate was cut into 60 mm square.

Next, 20 linear optical slits with a width of 40 μm and a length of 60 mm are arranged in parallel at intervals of 250 μm on the surface with reference marks (cross shape having a line width of 100 μm and a size of 500 μm square) formed in advance on the metal layer. After the photomask formed in this manner is aligned with the laminate, the cover film and the photomask are brought into contact with each other, and exposed to a 10 J / cm ² high-pressure mercury lamp through the photomask to select a photosensitive transparent material layer. Was cured to form an optical waveguide.

  Next, a light deflection portion was formed by processing a V-groove using a rotating blade with a 90 ° apex angle of the cutting blade with reference to the reference mark of the metal layer.

  Specifically, a disco # 5000 blade (model number “B1E863SD5000L100MT38”) was used as the rotating blade.

  Then, with respect to a position 5 mm from one end portion of the 20 exposed portions, a rotating blade is brought into contact with the laminate at a processing speed of 0.03 mm / s from the surface of the cover film at a rotational speed of 30000 rpm, and a depth of 80 μm. With the cutting depth maintained, the rotating blade was scanned at a speed of 0.1 mm / s so that all 20 exposed portions crossed at right angles. This was similarly carried out at a position of 5 mm from the opposite end of the exposed portion. As a result, V grooves were formed at both ends of 20 exposed portions of 5 mm. The surface roughness (rms) of the formed V-groove was 60 nm.

  Then, a silver paste in which silver particles having a particle size of 10 nm or less are dispersed is dropped on the surface of the obtained light deflecting portion, and heated at 120 ° C. for 1 hour to remove the solvent, whereby a metal thin film is formed on the inclined surface of the V groove. The deflection part formed was formed.

  Next, the cover film was peeled off and developed with an aqueous cleaning agent (trade name Clean Through manufactured by Kao Co., Ltd.) instead of toluene and Freon to remove the non-exposed area, washed with water and dried.

  Further, the transparent material A was further applied to the substrate on the transparent material layer forming side with a thickness of 50 μm, followed by heat curing at 100 ° C. for 1 hour and then at 150 ° C. for 1 hour to form a transparent material layer.

  Next, a varnish of adhesive C was applied to the formed transparent material layer to a thickness of 40 μm and dried at 150 ° C. to obtain an adhesive layer.

  Then, an FR-5 type printed wiring board provided with an electric circuit was placed on the surface of the adhesive layer and vacuum-pressed at 170 ° C. to bond them together.

  Next, after forming a 100 μmφ conformal mask hole and a reference guide at a location where a via hole is to be formed in the metal layer, an excimer laser is irradiated to form a via hole having an opening diameter of 100 μmφ, and then a surface formed by permanganate desmear. After performing the treatment and the soft etching process using a peroxidized water system, an electrically conductive part was formed in the via hole by panel plating to produce a photoelectric composite substrate having a copper foil stretched on the surface.

  Next, the mounting land and the electric circuit were formed by patterning the copper foil on the surface of the obtained photoelectric composite substrate by the following method.

  First, a photosensitive resist material was applied to the copper foil surface, and a photomask was aligned and placed. And the resist material was hardened by irradiating an ultraviolet-ray through the said photomask. The uncured portion was developed and removed, and an etching resist was formed on the copper foil.

  Next, the substrate was passed through an etching solution to dissolve unnecessary copper foil portions, and finally the etching resist was removed to form a mounting land and an electric circuit.

  For alignment of the photomask, a reference mark already formed on the metal layer was used.

  The mounting land was formed only on the side on which the VCSEL was mounted (incident side light deflection unit).

  Since the diameter of the VCSEL circular electrode pad is 50 μmφ, the diameter of the light emitting part is 10 μmφ, and the distance between the centers is 102.5 μm, the line segment at the closest point between the two contours is 72.5 μm. It was. The mounting land was formed so that the middle line of the line segment and the outline of the mounting land overlapped. The mounting land formed at this time was formed in a rectangular shape having a side of 122.5 μm (50 μm + 72.5 μm). At this time, the allowable amount of deviation allowed at the time of opening is 36.25 μm.

Next, a solder resist layer was formed on the formed mounting land by the following method. 800 g of liquid resist material DSR-2200KP 19 and 200 g of curing agent CA-2200KP 11 were mixed and stirred for about 30 minutes, and applied to the substrate by screen printing. This was pre-baked at 75 ° C. for 25 minutes, and then irradiated with ultraviolet rays at an energy density of 400 mJ / cm ₂ through a photomask designed to cover the mounting land. Thereafter, a 1.0 mass% Na ₂ CO ₃ aqueous solution was sprayed at 30 ° C. with a spray pressure of 0.2 MPa to wash away unexposed portions, and then cured at 150 ° C. for 30 minutes. Its thickness was 20 μm.

  Then, a KrF excimer laser (manufactured by Lumonics) was used, and a biaxial table stage (AX2020P4Y manufactured by THK) was used as a processing sample stage, and connected to a programmable NC controller. The mechanical positioning accuracy is ± 1 μm.

  In addition, the processing position can be seen with a camera by using a 5x objective lens, a lens barrel (Chuo Seiki TV-IE), and a 2/3 size CCD.

  Using the apparatus, the optical deflection portion of the obtained photoelectric composite substrate is observed, the center of the virtual diagonal line is set as the origin (0, 0), and the base of the substrate is selected as the X axis. A coordinate system was set.

  Next, the coordinates (−72.5, 72.5) and (72.5, 72.5) of the circular electrode pads 62 and 63 of the VCSEL measured in advance are input to the NC control program, and the circular electrode An electrode pad for mounting a device for photoelectric conversion was formed by opening a pattern exposure using a stainless steel mask with a 1 mmφ punch at the center point of the coordinates of the pads 62 and 63 using a KrF excimer laser. The two coordinate systems are matched by the NC control program.

  The irradiation energy density of the KrF excimer laser was 10 mJ per pulse, the frequency was 100 Hz, and the number of irradiation pulses was 20 pulses. The diameter after processing was 102 μmφ on the resist surface and 98 μmφ on the back surface (copper foil surface).

  An attempt was made to mount a VCSEL on the completed photoelectric composite substrate. Solder bumps were formed on the circular electrode pads 62 and 63 of the VCSEL, placed on the photoelectric conversion element mounting electrode pads, and subjected to a reflow process. The reflow conditions were a standard profile with a peak temperature of 230 ° C. and 210 ° C. or more and 40 seconds.

  Then, a direct current of 3.2 mA was passed through the VCSEL to emit light at an output of 1 mW, light was received by a fiber having a core diameter of 100 μmφ and a nominal NA of 0.26 on the opposite optical deflection portion, and the received light power was measured by a power meter.

  As a result of the measurement, it was found that the received light power was 0.34 mW and suffered a loss of 4.5 dB. Since the loss of the waveguide is 0.15 dB per 10 mm, the loss at the optical deflection unit is calculated to be 3.6 dB excluding 0.9 dB, which is 60 mm, and as a result, the loss per optical deflection unit Was found to be 1.8 dB. Considering that the reflection loss at the interface with the air layer is included, it can be said that good optical-electrical coupling is realized.

  Further, 10 photoelectric composite substrates obtained in the same manner as above and 10 photoelectric composite substrates formed only by the conventional photomask method were prepared, and the VCSEL was mounted on each.

  And the loss per one light deflection | deviation part was evaluated with respect to each photoelectric composite board | substrate.

  As a result, in the photoelectric composite substrate formed only by the photomask method, the loss per one light deflection unit is in the range of 2.5 to 10.0 dB, and the average is 6.3 dB. In the photoelectric composite substrate obtained in the example, the loss per one light deflection unit was 1.3 to 2.5 dB, and the average was 1.8 dB. Therefore, it can be seen that when the photoelectric conversion element is mounted on the photoelectric composite substrate obtained by the photoelectric composite substrate manufacturing method of the present invention, both the average value and the variation are greatly improved.

(Example 2)
In the same manner as in Example 1, the solder resist was formed.

  Then, the light deflection unit was visually recognized from above with a camera, and the point where the center point was moved in the 3.3 μm X axis direction with respect to the coordinates of the photoelectric composite substrate was set as a reference point.

The value of 3.3 μm is that when the refractive index (n ₁ ) of the core of the waveguide layer is 1.53, the refractive index (n ₀ ) of the clad is 1.51, and the light deflection unit is projected onto the substrate surface. The emission angle of a square VCSEL with a side of 40 μm is 18 ° (1 / e2 full angle value), the shape of the deflection unit projected onto the substrate surface is a square with a side of 40 μm, and the refractive index of the waveguide is the core. Since the claddings are 1.53 and 1.51, respectively, a more optimal reference point is calculated using geometric optical calculation.

  Ten photoelectric composite substrates obtained in the same manner as in Example 1 were prepared, and the VCSELs were mounted on each of the photoelectric composite substrates, and the loss per light deflection unit was evaluated for each photoelectric composite substrate.

  As a result, the loss per light deflecting portion in the photoelectric composite substrate obtained in this example was 1.1 to 2.5 dB, and the average was 1.6 dB.

(Example 3)
In the same manner as in Example 1, the solder resist was formed.
Next, the VCSEL was caused to emit light at 1 mW, and light was incident on the incident-side deflection unit at a height of 60 μm from the mounting land on the substrate surface. And the light which propagated in the waveguide and was radiate | emitted from the deflection | deviation part by the side of an emission was received with the multimode fiber of core diameter 100micrometerphi and NA0.26, and the light reception power at that time was observed with the power meter. In this state, the VCSEL was scanned in the surface direction, and the position where the light receiving power was maximized was confirmed.

  Next, the state was observed from the upper part of the substrate with a CCD camera, and a deflection-like point that maximized the received light power was set as a reference point. The position corresponding to the center point of the light-emitting surface was determined on the basis of the outer shape from the front side by recording the layout of the back surface of the VCSEL in advance.

  Next, the VCSEL was removed, the deflection part was observed with a CCD camera, and an opening was made using a KrF excimer laser in the same manner as in Example 1 based on the set reference point.

  Ten photoelectric composite substrates obtained in the same manner as in Example 1 were prepared, and the VCSELs were mounted on each of the photoelectric composite substrates, and the loss per light deflection unit was evaluated for each photoelectric composite substrate.

  As a result, the loss per light deflection unit in the photoelectric composite substrate obtained in this example was 1.0 to 2.0 dB, and the average was 1.4 dB.

  Thus, when a photoelectric conversion element was mounted on the photoelectric composite substrate obtained by using the method for manufacturing a photoelectric composite substrate of the present invention, an electrode pad for mounting the photoelectric conversion element was formed only by a conventional photomask method. Since it can be formed with higher accuracy than in the case, the photoelectric conversion element and the optical axis of the optical deflection portion of the photoelectric composite substrate can be aligned with high accuracy, and therefore, a highly efficient optical circuit-electricity A photoelectric composite substrate capable of easily realizing inter-circuit coupling is obtained.

The cross-sectional schematic diagram which shows an example of the photoelectric composite board | substrate which concerns on this invention. The cross-sectional schematic diagram which shows the process of the manufacturing method of the photoelectric composite substrate of this invention. The cross-sectional schematic diagram which shows the process of the manufacturing method of a photoelectric composite substrate following the process of FIG. The plane schematic diagram which shows arrangement | positioning of the photomask for forming a mounting land, and the electrode pad part of the photoelectric conversion element mounted. FIG. 3 is a schematic plan view showing a part of a photomask for forming a mounting land. 6A is a schematic plan view showing the arrangement of solder bump forming electrode pads of the photoelectric conversion element mounted on the photoelectric composite substrate, and FIG. 6B is a mounting land, an optical waveguide layer, and an optical deflection unit of the photoelectric composite substrate. The schematic plan view which showed arrangement | positioning. The plane schematic diagram which shows arrangement | positioning of the electrode pad for solder pump formation of VCSEL used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical waveguide layer 2 Electrical circuit layer 3 Optical waveguide 4 Optical deflection part 4a Equivalent point of reference point on photomask 5 Photoelectric conversion element 5a Light emitting / receiving part 5b, 5c Solder bump forming electrode pad 6 Solder bump 7 Mounting land 8 Solder resist 9a, 9b Electric circuit 10 Photoelectric composite substrate 11 Pad for mounting photoelectric conversion element 12 First transparent material layer 13 Second transparent material layer 14 Metal thin film 15 Adhesive layer 16 Electric circuit board 17, 18 Electric circuit 21 Solder resist forming layer 31, 32 Photomask opening 33 Reference mark 53 Center of light receiving and emitting part 61 Circular electrode pad 62 Circular electrode pad 63 Light emitting part 101 Metal foil 111 Photomask for forming optical waveguide 112 Mounting land and electric circuit are formed Photomask for 113 Photo for forming solder resist Mask 131 Non-exposed portion 151 Reference point C1, C2 Middle line

Claims (3)

A method for manufacturing a photoelectric composite substrate comprising an optical waveguide layer having an optical waveguide provided with an optical deflecting portion, and an electrode pad for mounting a photoelectric conversion device for mounting a photoelectric conversion device having a solder bump on the substrate surface. There,
When the center point of the opening for forming the mounting land matches the center point of the solder bump forming electrode pad of the corresponding photoelectric conversion element, the outline of the solder bump forming electrode pad and the photoelectric conversion element Forming a mounting land on the substrate surface using a photomask in which the outline of the opening is located near the midpoint of the line connecting the points on the outline closest to the outline of the light emitting and receiving part
A step of covering a mounting land previously formed on the substrate surface with a solder resist,
Setting a reference point on the light deflection unit;
Coordinates of the center of the electrode pad for mounting the photoelectric conversion element from the reference point on the solder resist so that the center of the light receiving and emitting part of the photoelectric conversion element overlaps the light deflection unit when the photoelectric conversion element is mounted Identifying the process,
A method for manufacturing a photoelectric composite substrate, comprising: forming a part of the solder resist with reference to the identified coordinates, exposing a mounting land to form an electrode pad for mounting a photoelectric conversion element. In the manufacturing method of the photoelectric composite substrate of Claim 1,
Coordinates of the center of the electrode pad for mounting the photoelectric conversion element from the reference point on the solder resist so that the center of the light receiving and emitting part of the photoelectric conversion element overlaps the light deflection unit when the photoelectric conversion element is mounted Identifying the coordinates of the center of the electrode pad for forming a solder bump of the photoelectric conversion element from the center of the light receiving and emitting part of the mounted photoelectric conversion element, and using the specified coordinates A method for producing a photoelectric composite substrate. In the manufacturing method of the photoelectric composite substrate of Claim 1 or Claim 2,
A process for forming a photoelectric conversion element mounting electrode pad by opening a part of the solder resist on the basis of the specified coordinates and exposing a mounting land to produce a photoelectric conversion substrate, comprising: Method.

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