JP2007294743A - Optical module and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module that prevents displacement of a photoelectric transducer with respect to a lens or an optical fiber without reducing a light amount of outgoing or incident light of the photoelectric transducer. <P>SOLUTION: The optical module is composed of a package 2 having an opening whose upper part is opened, a sealing member 4 which has a light transmitting opening 18 for inputting/outputting an optical signal while covering the opening of the package 2, and a light transmitting member 19 that becomes a path for the optical signal while sealing the light transmitting opening 18. A circuit substrate 3 with a circuit pattern 10 formed on its rear face is stored in the package 2. The photoelectric transducers 11, 12 are mounted onto the circuit pattern 10 on the rear face of the circuit substrate 3. A taper-shaped optical-path hole 14 with its diameter increased from the rear-face side to the surface side of the substrate is formed in the circuit substrate 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical module used for optical interconnection and a method for manufacturing the same.

  In recent years, optical interconnection, which is a technique for transmitting signals within a system apparatus and between apparatuses at high speed, has been spreading. In other words, the optical interconnection is a technology in which an optical component is handled as if it were an electrical component and surface-mounted on a motherboard or a circuit board of a device such as a personal computer, a vehicle, or an optical transceiver.

  As a conventional optical module used for optical interconnection, there is an optical module 81 as shown in FIG.

  In this optical module 81, a circuit pattern is formed in a ceramic package 82 having a cavity opened at the top, and a transparent substrate 83 is accommodated in the ceramic package 82, and a semiconductor laser (LD) is provided on the back surface of the transparent substrate 83. A plurality of 84 are mounted, and the upper part of the ceramic package 82 is covered with a metal lid 86 with a glass 85 serving as an optical path and hermetically sealed. In the optical module 81, the optical signal from the LD 84 is output through the glass 85, collected by the lens 87, and transmitted to the outside.

  The prior art document information related to the invention of this application includes the following.

JP 2005-292739 A

  However, the conventional optical module 81 uses a transparent substrate 83 as a circuit board on which the LD 84 is mounted. For this reason, a part of the emitted light of the LD 84 is reflected by the back surface and the front surface of the transparent substrate 83, and there is a problem that the light amount of the emitted light is reduced by about 8%.

  When a resin substrate is used as the transparent substrate 83, the LD 84 is displaced with respect to the lens that collects the emitted light and the optical fiber that is optically coupled to the lens due to the temperature expansion of the resin and the swelling due to moisture. There is also a problem.

  Accordingly, an object of the present invention is to provide an optical module in which the amount of light incident / incident light of a photoelectric conversion element is not reduced and the photoelectric conversion element is not displaced with respect to a lens or an optical fiber, and a method for manufacturing the same.

  The present invention has been devised in order to achieve the above object, and the invention of claim 1 is for covering a package having an opening having an upper opening, and for inputting / outputting an optical signal while covering the opening of the package. A circuit pattern is formed on the back surface of the package in an optical module comprising a sealing member having a light transmitting opening and a light transmitting member that seals the light transmitting opening and serves as an optical signal path. The circuit board is housed, and a photoelectric conversion element is mounted on the circuit pattern on the back surface of the circuit board, and a tapered light passage hole whose diameter increases from the back surface side to the front surface side is formed on the circuit board. This is an optical module.

  The invention according to claim 2 is the optical module according to claim 1, wherein the circuit board is an opaque substrate such as a ceramic substrate, a Si substrate, or a glass epoxy substrate.

  The invention according to claim 3 is the optical module according to claim 1, wherein the circuit board is a glass substrate.

  The invention according to claim 4 is the optical module according to any one of claims 1 to 3, wherein the light passage hole has an opening angle of 20 ° or more.

  According to a fifth aspect of the present invention, when the photoelectric conversion element is a light emitting element, the light passage hole has a diameter on the back side of the substrate equal to or larger than the light emission diameter, and when the photoelectric conversion element is a light receiving element, the diameter on the back side of the substrate. The optical module according to any one of claims 1 to 4, wherein the optical module is not less than a light receiving diameter.

  The invention according to claim 6 is the optical module according to any one of claims 1 to 5, wherein the circuit board has a thickness of 0.5 mm or more.

  According to a seventh aspect of the present invention, a terrace for mounting the circuit board is provided in the package, a package side electrode is formed on the terrace, and a substrate side electrode is provided on the back surface of the circuit board corresponding to the package side electrode. The optical module according to any one of claims 1 to 6, wherein the circuit board is housed in the package by forming and joining both electrodes.

  According to an eighth aspect of the present invention, a bonding frame is formed on an upper edge surface that is one step higher than the package side electrode of the package, the circuit board is accommodated in the package, and then the light transmission corresponding to the bonding frame. 8. The optical module according to claim 7, wherein the metal sealing member provided with a member is provided, the sealing member and the joining frame are joined, and the sealing member is joined to the package and hermetically sealed. .

  The invention according to claim 9 is the optical module according to claim 8, wherein the sealing member is electrically connected to the circuit pattern of the package through the joining frame.

  The invention according to claim 10 is the optical module according to any one of claims 1 to 9, wherein a metal film is formed on a surface of the circuit board other than the light passage hole.

  The invention according to claim 11 is the optical module according to claim 10, wherein the metal film is electrically connected to the circuit pattern of the package through a through hole formed in the circuit board.

  The invention according to claim 12 is the optical module according to any one of claims 1 to 11, wherein the photoelectric conversion element is a surface emitting laser array and / or a photodiode array.

  According to a thirteenth aspect of the present invention, the substrate-side electrode is formed around the photoelectric conversion element and the control semiconductor chip that controls each photoelectric conversion element of the circuit board, and the photoelectric conversion element and the control semiconductor chip are controlled. It is an optical module in any one of Claims 1-12 conducted.

  According to a fourteenth aspect of the present invention, the substrate-side electrode is electrically connected to the package-side electrode using solder bumps or Au bumps, and the circuit board is bonded to the package. It is an optical module of description.

  According to a fifteenth aspect of the present invention, in the sealing member, a light transmitting opening is formed at a central portion, and the light transmitting member is attached to the light transmitting opening with a sealing material. It is an optical module as described in above.

  The invention of claim 16 is characterized in that the sealing member and the joining frame are joined by electric welding or laser welding to join the sealing member to the package and hermetically seal. It is an optical module.

  According to a seventeenth aspect of the present invention, there is provided a package having an opening having an upper opening, a sealing member that covers the opening of the package and has a light transmission opening for inputting and outputting an optical signal, and the light transmission In a method for manufacturing an optical module comprising a light transmitting member that seals an opening and serves as a path for an optical signal, a circuit pattern is formed on the back surface of a circuit board housed in the package, and the circuit pattern is subjected to photoelectric conversion. Tapered light that has a conversion element and irradiates the circuit board with a femtosecond laser or a UV-YAG laser, digs up the circuit board while scanning, and increases in diameter from the back side of the board to the front side. It is a manufacturing method of the optical module which forms a passage hole.

  According to the present invention, an optical signal can be input / output without reducing the amount of incident / incident light from the photoelectric conversion element.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 is a perspective view of an optical module showing a preferred embodiment of the present invention, FIG. 2 is a sectional view taken along line 2A-2A, FIG. 3 is an exploded perspective view thereof, and FIG. 4 is an exploded perspective view of FIG. FIG. 2 is a perspective view of the circuit board.

  As shown in FIGS. 1 to 4, an optical module (hermetic sealed parallel optical module) 1 according to this embodiment is surface-mounted on a motherboard or a circuit board of a device such as a personal computer, a vehicle, or an optical transceiver. The area is about 1 cm × 1 cm.

  This optical module 1 has an opening (cavity, cavity, dent, room) with an open top, a ceramic package 2 having a concave longitudinal section, a circuit board 3 accommodated in the ceramic package 2, and a ceramic package And a cap 4 as a sealing member having a window (light transmission opening) 18 for inputting / outputting an optical signal and a light transmission member that seals the window 18 and serves as a path for the optical signal And the glass window 19 as a main component.

The ceramic package 2 was used as the package when the inside of the package was hermetically sealed as described later, and the hermetic sealing level was 10 ⁻⁹ Pa · m ³ / s [He] or less in the He leak test. Because it is necessary to keep.

  A package-side circuit pattern 5 is formed in the ceramic package 2. A part of the circuit pattern 5 is formed by connecting the upper edge surface and the bottom surface of the ceramic package 2. On the bottom surface of the ceramic package 2, a plurality of solder balls 6 for mounting the optical module 1 on the motherboard or circuit board of the device are arranged in a grid. That is, the ceramic package 2 constitutes a BGA.

  The ceramic package 2 is provided with a terrace 7 for mounting a circuit board 3 that is one step higher than the bottom surface. On the terrace 7, a plurality of terrace-side electrodes 8 are formed side by side as package-side electrodes that are electrically connected to the circuit pattern 5. The terrace upper electrode 8 is formed in a lump by, for example, photoetching a Cu foil. On the upper edge surface that is one step higher than the terrace upper electrode 8 of the ceramic package 2, a joining frame 9 that is electrically connected to the circuit pattern 5 and serves as a tray for the cap 4 is formed of a metal such as Au / Ni.

  A substrate side circuit pattern 10 is formed on the back surface of the circuit substrate 3. The substrate-side circuit pattern 10 of the circuit board 3 includes a surface emitting laser array (VCSEL array) 11 in which four LDs are arranged in an array with a narrow pitch (for example, 250 μm) as photoelectric conversion elements (light emitting elements) for light emission. Then, as a photoelectric conversion element (light receiving element) for receiving light, the PD array 12 in which four photodiodes (PD) are arranged in an array at a narrow pitch (for example, 250 μm), the VCSEL array 11 and the PD array 12 are controlled. As a control semiconductor chip, a control IC 13 and electrical components such as resistors and capacitors are mounted.

  The VCSEL array 11 is flip-chip mounted on the back surface of the circuit board 3 using solder bumps or Au bumps. In other words, the VCSEL array 11 is mounted so that the light emitting region of each LD faces the circuit board 3. Similarly, the PD array 12 is also flip-chip mounted on the back surface of the circuit board 3 using solder bumps or Au bumps. That is, the PD array 12 is mounted such that the light receiving area of each PD faces the circuit board 3.

  The control IC 13 is a driver (LD drive circuit IC) as a drive circuit that drives each LD of the VCSEL array 11, and a preamplifier (PD drive circuit IC) as an amplification circuit that amplifies an electric signal from each PD of the PD array 12. Etc.

  As shown in FIGS. 1, 2, 4, and 5, the circuit board 3 has a plurality of tapered light passage holes 14 having a diameter increasing from the back surface side to the front surface side (four in the figure). A total of eight light passage holes 14 for four LDs and four light passage holes 14 for four PDs).

  As shown in FIG. 5, the light passage hole 14 has an opening angle θp of 20 ° because the beam divergence angle of each LD of the VCSEL array 11 and the beam divergence angle θd of incident light of each PD of the PD array are 20 to 30 °. That's it.

  Considering that the mounting accuracy is usually ± 10 μm in the case of an LD, the light passage hole 14 has a diameter φd on the back surface side of the substrate of 20 to 30 μm which is equal to or larger than the light emission diameter φt of the LD = 10 μm. In the present embodiment, φd of the light passage hole 14 located on the VCSEL array 11 is set to 30 μm.

  Further, in the case of the PD, the optical passage hole 14 has a mounting accuracy of ± 10 μm, and the diameter φd on the back side of the substrate is generally considered in consideration of the fact that the PD has a light receiving diameter φr = 80 μm. Is 90 to 110 μm where the light receiving diameter φr of PD is 80 μm or more. In the present embodiment, φd of the light passage hole 14 located on the PD array 12 is set to 100 μm.

  The thickness d of the circuit board 3 is preferably 0.5 mm or more. This is because if the thickness d of the circuit board 3 is less than 0.5 mm, the circuit board 3 warps, and each LD of the VCSEL array 11 or each PD of the PD array 12 collects the incident / incident light. This is because the position is shifted with respect to the optical fiber optically coupled to the lens.

  In the present embodiment, since the thickness d of the circuit board 3 is 0.5 mm and the opening angle θp is 30 °, the diameter φu on the substrate surface side of the light passage hole 14 is 0.26 mm. Further, the distance x between the light emitting region of each LD of the VCSEL array 11 and the light receiving region of each PD of the PD array and the back surface of the circuit board 3 was set to 0.05 mm.

  As the circuit board 3, an opaque substrate such as a ceramic substrate, a Si substrate, or a glass epoxy substrate is used.

  As shown in FIGS. 1 to 4, a plurality of lower surface electrodes 15 are formed as substrate-side electrodes around the VCSEL array 11, the PD array 12, and the control IC 13 of the circuit board 3. These lower surface electrodes 15 are electrically connected to the VCSEL array 11, the PD array 12, and the control IC 13. The lower surface electrode 15 is formed in a lump by, for example, photoetching a Cu foil.

  A metal film 16 is formed of a metal such as Cu on the surface other than the light passage hole 14 of the circuit board 3. The metal film 16 is formed by plating, for example. The metal film 16 forms a through hole 17 in the circuit board 3, and through this through hole 17, a solid GND layer (entire GND layer) constituting a part of the circuit pattern 5 in the ceramic package 2, or a device It is electrically connected to GND of the motherboard and circuit board.

  The cap 4 is formed in a frame shape with a metal such as Cu corresponding to the joining frame 9. The cap 4 is electrically connected to the circuit pattern 5 of the ceramic package 2 via the joining frame 9. An opening 18 is formed at the center of the cap 4, and a glass window 19 is attached to the opening 18 with a sealing material s. As the sealing material s, low melting point glass is used.

  In assembling the optical module 1, first, each optical component and each electrical component are flip-chip mounted on the circuit board 3.

  Then, in an atmosphere of an inert gas such as He or nitrogen, the upper terrace electrode 8 and the lower electrode 15 are soldered and electrically connected using solder bumps or Au bumps to the ceramic package 2 and the circuit board 3. Join. Thereby, the circuit board 3 is accommodated in the ceramic package 2. At the same time, the cap 4 is joined to the joining frame 9 and hermetically sealed, and the cap 4 is joined to the ceramic package 2.

The joining frame 9 and the cap 4 are joined by electric welding such as resistance welding or laser welding. The reason why electric welding or laser welding is used for joining the joining frame 9 and the cap 4 is to keep the hermetic sealing level at 10 ⁻⁹ Pa · m ³ / s [He] or less in the He leak test.

  Here, adhesives and synthetic resins cannot be used because they are non-hermetic seals. In particular, since the synthetic resin swells, the VCSEL array 11 and the PD array 12 are exposed to the outside air and moisture, which is not suitable.

  Finally, when a plurality of solder balls 6 are arranged in a grid on the back surface of the ceramic package 2 to form a BGA, the optical module 1 is assembled.

  Further, the optical module 1 has eight lenses for condensing the emitted light of each LD of the VCSEL array 11 or the incident light of each PD of the PD array 12 on the surface of the circuit board 3 on the light passage hole 14. The integrated lens block provided is mounted. An MT optical connector to which eight optical fibers are connected is connected to the lens block.

  Next, a method for manufacturing the optical module 1 will be described. Here, since it can manufacture by a conventional method except for the optical path hole 14, only the formation method of the optical path hole 14 is demonstrated.

  As shown in FIG. 6, the surface of the circuit board 3 is irradiated with a femtosecond laser or a UV (ultraviolet ray) -YAG laser L, and the circuit board 3 is dug while being spirally scanned (that is, by trepanning). The light passage hole 14 is formed.

  More specifically, as shown in FIG. 7, first, a femtosecond laser, which is one of pulse lasers, or a UV-YAG laser is scanned left and right within a circle 71 having a diameter φu on the substrate surface side. The light passage hole 14 is formed by gradually reducing the circle in the range in which the laser is scanned as the depth increases, such as circles 72 and 73. That is, the laser is scanned so that the hole diameter decreases as the hole depth increases from the substrate surface side. As a result, an inverted frustoconical light passage hole 14 is formed.

  Here, the femtosecond laser emits seed light (green laser) on titanium sapphire and regenerates and reproduces titanium sapphire. Wavelength λ = 780 to 800 nm, pulse width is 50 fs or more, output is 1 to 2 W, frequency is 1 kHz (continuous charge time). If the pulse width of the femtosecond laser is 150 fs or less, the processing is completed before the laser light is converted into thermal energy. This is called ablation. In other words, when a femtosecond laser is used, there is an advantage that heat does not occur and the periphery of the light passage hole 14 does not rise.

  The UV-YAG laser excites and emits a YAG crystal, transmits the wavelength crystal, and converts the wavelength to the short wavelength side. There are various wavelengths of λ / 4, λ / 3, and λ / 2 (λ = 1064 nm), and the shorter the wavelength, the stronger. The pulse width is 20 ns, the output is 1 to 50 W, and the frequency (continuous charge time) is 30 kHz.

  The operation of the first embodiment will be described.

  In the optical module 1, four electrical signals from the motherboard and circuit board of the device are transmitted in the order of the circuit pattern 5 of the ceramic package 2, the control IC 13, and the VCSEL array 11, and are converted into optical signals by the VCSEL array 11, respectively. From the VCSEL array 11, four optical signals having different wavelengths are output upward through the circuit board 3 and the optical passage hole 14.

  On the other hand, in the optical module 1, four optical signals having different wavelengths input from above the circuit board 3 through the optical passage hole 14 and the circuit board 3 are converted into electrical signals by the PD array 12. One electrical signal is transmitted in the order of the control IC 13, the circuit pattern 5 of the ceramic package 2, the motherboard of the device, and the circuit board.

  Since the optical module 1 has the optical passage hole 14 formed in the circuit board 3, an optical signal can be input / output through the glass window 19 even if the VCSEL array 11 and the PD array 12 are mounted on the back surface of the circuit board 3.

  In particular, when an opaque substrate is used as the circuit board 3, the light passage hole 14 prevents light from being reflected from the front and back surfaces of the circuit board 3, and thus the amount of incident / incident light from the VCSEL array 11 and the PD array 12. Optical signals can be input / output without reducing

  Since the light passage hole 14 is tapered, the light passage hole 14 can be formed on any substrate as long as the circuit board 3 has a thickness of 0.5 mm or more for the purpose of preventing warpage.

  Further, since a ceramic substrate, Si substrate, glass epoxy substrate, or the like is used for the circuit board 3, there is very little influence of temperature expansion and swelling due to moisture as in the case of using a resin substrate. The optical fiber is optically coupled to the optical fiber.

  According to the manufacturing method according to the present embodiment, since the optical passage hole 14 is formed by a femtosecond laser or a UV-YAG laser, the three-dimensional optical passage hole 14 can be easily and accurately manufactured on the circuit board 3. In addition, since a spot-like small hole of about 10 μm, such as the deepest part of the light passage hole 14, can be formed, it is possible to secure a mounting spot for the VCSEL array 11 and the PD array 12 on the back surface of the circuit board 3.

  In the optical module 1, the metal cap 4 is electrically connected to the circuit pattern 5 of the ceramic package 2 through the joint frame 9, so that the cap 4 can serve as an electromagnetic shielding plate to prevent electromagnetic waves from entering and exiting. Strong against EMI (electromagnetic interference).

  Further, the optical module 1 has a metal film 16 formed on the surface other than the optical passage hole 14 of the circuit board 3, and the metal film 16 is connected to the GND of the motherboard of the device, the circuit board, and the GND layer of the ceramic package 2. Conducted. For this reason, the metal film 16 can serve as an electromagnetic shielding plate to prevent electromagnetic waves from entering and exiting, and is strong against EMI.

In the optical module 1, since the cap 4 and the joining frame 9 are electrically welded or laser welded to join the cap 4 to the ceramic package 2 and hermetically sealed, there is no gap between the cap 4 and the joining frame 9, The level of hermetic sealing can be maintained at 10 ⁻⁹ Pa · m ³ / s [He] or less in the He leak test.

  In the above embodiment, an example in which an opaque substrate is used as the circuit board 3 has been described. However, a glass substrate may be used as the circuit board 3. By forming the light passage hole 14 in the glass substrate, light is not reflected on the front surface and the back surface of the glass substrate. In this case as well, without reducing the amount of light incident / incident on the VCSEL array 11 or PD array 12. Can input and output optical signals.

It is a perspective view of the optical module which shows suitable embodiment of this invention. FIG. 2 is a cross-sectional view of the optical module shown in FIG. 1 taken along line 2A-2A. It is a disassembled perspective view of the optical module shown in FIG. FIG. 3 is an exploded perspective view of the optical module shown in FIG. 2 as viewed from above and a perspective view of a circuit board. It is an expanded sectional view of a light passage hole. It is a figure explaining the manufacturing method of the optical module (light passage hole) shown in FIG. It is a figure explaining the manufacturing method of the optical module (light passage hole) shown in FIG. It is sectional drawing of the conventional optical module.

Explanation of symbols

1 Optical Module 2 Ceramic Package 5 Package Side Circuit Pattern 10 Substrate Side Circuit Pattern 11 VCSEL Array (Photoelectric Conversion Element)
12 PD array (photoelectric conversion element)
14 Light passage hole 18 Window (light transmission opening)
19 Glass window (light transmissive member)

Claims (17)

  A package having an opening having an upper opening; a sealing member that covers the opening of the package and has a light transmission opening for inputting and outputting an optical signal; and sealing the light transmission opening. In an optical module composed of a light transmitting member serving as an optical signal path, a circuit board having a circuit pattern formed on the back surface is housed in the package, and a photoelectric conversion element is mounted on the circuit pattern on the back surface of the circuit board. An optical module having a tapered optical passage hole having a diameter increasing from the back surface side to the front surface side of the circuit board.   2. The optical module according to claim 1, wherein the circuit board is an opaque substrate such as a ceramic substrate, a Si substrate, or a glass epoxy substrate.   The optical module according to claim 1, wherein the circuit board is a glass substrate.   The optical module according to claim 1, wherein the optical passage hole has an opening angle of 20 ° or more.   When the photoelectric conversion element is a light emitting element, the light passage hole has a diameter on the back side of the substrate equal to or larger than the light emission diameter, and when the photoelectric conversion element is a light receiving element, the diameter on the back side of the substrate is equal to or larger than the light receiving diameter. Item 5. The optical module according to any one of Items 1 to 4.   The optical module according to claim 1, wherein the circuit board has a thickness of 0.5 mm or more.   The package is provided with a terrace on which the circuit board is placed, a package side electrode is formed on the terrace, and a substrate side electrode is formed on the back surface of the circuit board corresponding to the package side electrode. The optical module according to claim 1, wherein the circuit board is housed in the package by bonding.   A bonding frame is formed on an upper edge surface that is one step higher than the package side electrode of the package, and the circuit board is accommodated in the package, and then a metal made of the metal having the light transmitting member corresponding to the bonding frame The optical module according to claim 7, wherein the sealing member is provided, the sealing member and the joining frame are joined, and the sealing member is joined to the package and hermetically sealed.   The optical module according to claim 8, wherein the sealing member is electrically connected to the circuit pattern of the package through the bonding frame.   The optical module according to claim 1, wherein a metal film is formed on a surface other than the optical passage hole of the circuit board.   The optical module according to claim 10, wherein the metal film is electrically connected to the circuit pattern of the package through a through hole formed in the circuit board.   The optical module according to claim 1, wherein the photoelectric conversion element is a surface emitting laser array and / or a photodiode array.   The substrate-side electrode is formed around the photoelectric conversion element of the circuit board and a control semiconductor chip that controls each photoelectric conversion element, and is electrically connected to the photoelectric conversion element and the control semiconductor chip. The optical module in any one of -12.   The optical module according to claim 1, wherein the substrate-side electrode is electrically connected to the package-side electrode using a solder bump or an Au bump, and the circuit board is bonded to the package.   The optical module according to any one of claims 1 to 14, wherein the sealing member has a light transmission opening formed in a central portion, and the light transmission member is attached to the light transmission opening with a sealing material.   The optical module according to claim 8, wherein the sealing member and the joining frame are joined by electric welding or laser welding to join the sealing member to the package and hermetically seal. A package having an opening having an upper opening; a sealing member that covers the opening of the package and has a light transmission opening for inputting and outputting an optical signal; and sealing the light transmission opening. In a method of manufacturing an optical module comprising a light transmitting member serving as an optical signal path, a circuit pattern is formed on the back surface of a circuit board housed in the package, and a photoelectric conversion element is mounted on the circuit pattern, and The circuit board is irradiated with a femtosecond laser or a UV-YAG laser, and the circuit board is dug while scanning to form a tapered light passage hole whose diameter increases from the back surface side to the front surface side. A method for manufacturing an optical module.

Images