JPH0730092A - Optical element module - Google Patents

Abstract

PURPOSE:To facilitate the regulation of the junction interval between a two-dimensional optical element array and a semiconductor circuit board to prolong the life of solder bumps by a method wherein spacers are provided at a plurality of places in the diagonal direction of at least a substrate electrode on the periphery of each electrode on the board between the array and the board. CONSTITUTION:An optical element module 101 is provided with a twodimensional optical element array 102 consisting of InGaAs surface emitting laser diodes, a semiconductor circuit board 103 consisting of a GaAs IC and an optical component 106 consisting of a package 104, a cap 105 and a distributed index microlens array. Spacers 110 for regulating the junction interval between the array 102 and the board 103 are formed at a plurality of places in the diagonal direction of at least the substrate electrode on the periphery of each electrode 108 on the board 103. By regulating the junction interval using the spacers 110, the connection of a flip chip of unadjusted height with the module 101 can be made and at the same time, the generation of the defective connection can be prevented. Moreover, the thermal fatigue of solder bumps can be relaxed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a module having a two-dimensional array of optical elements mounted thereon, and more particularly to an optical element module for connecting electrodes of a two-dimensional array and adjusting an electrode interval.

[0002]

2. Description of the Related Art For example, an optical element module described in JP-A-3-141308 is known. The optical element and the substrate electrode are flip-chip connected by solder bumps.
Flux is used to remove the oxide film on the surface of the solder bump. As a result, the self-alignment action based on the surface tension of the solder bumps works to correct the positional deviation between the electrodes of the optical element and the substrate.

Further, as a conventional flip-chip connection method, a method announced at the 1992 IEICE Autumn Meeting C-164 is known. In this method, a transparent substrate is used, and the optical element electrode pattern is directly observed from the surface opposite to the optical element mounting surface for alignment. Furthermore, by applying the automatic low-frequency scrubbing method, flux-free flip-chip bonding is performed.

[0004]

In recent years, optical interconnection has been used to connect between housings of large computers or between wiring boards. In order to improve the transmission throughput and packaging density of the optical element module, the number of optical elements mounted on the module is increasing year by year. In the future, it is expected that two-dimensional arrays of optical elements will be used. Flip-chip connection is suitable for connecting the electrodes of the two-dimensional array.

At present, the size of electrodes and solder bumps of ordinary semiconductor elements is 100 μm to 300 μm in diameter and 100 μm in thickness.
Although it is m to 300 μm, it is presumed that it will be further miniaturized in the future in order to achieve high speed, that is, low capacitance and low inductance. Specifically, the diameter is 10 μm to 50 μm,
It is considered that the thickness is about several μm to 30 μm. To further increase the speed, it is necessary to shorten the wire wiring length in the module. In order to realize this, it is considered effective to wirelessly directly connect the optical element to the semiconductor circuit board by flip-chip connection.

The conventional optical element module does not consider the alignment of such fine electrodes and solder bumps. As is generally known, the activator contained in the flux deteriorates the characteristics of the optical device. Although it is desirable not to use flux, an oxide film remains on the solder bumps, which makes it difficult for the surface tension to work. In addition, since a solder bump having a large size is ball-shaped, surface tension works. However, the fine solder bumps described above are disc-shaped, and the surface tension does not work so much. Therefore, the self-alignment action does not occur and the positional deviation is not corrected. The optical element and the electrode of the substrate are directly connected at the position where the optical element is mounted on the substrate by the flip chip connecting device.

In the conventional flip-chip connection method, the flip-chip connection without flux is realized with an accuracy of ± 2 μm. However, there has been insufficient consideration regarding flip-chip connection of an optical element directly to a semiconductor circuit board. In general, a semiconductor circuit board is not transparent to visible light, so that it is impossible to directly observe the optical element electrode pattern from the surface opposite to the optical element mounting surface for alignment and flip-chip connection. That is, since the connection between the electrodes cannot be directly confirmed, a connection failure such as a contact failure (open) between the electrode and the solder bump or a contact (short circuit) between the adjacent solder bumps occurs due to a variation in the distance between the electrodes.

From the above, in the conventional optical element module,
There is a problem that it is difficult to adjust the distance between the solder bump electrode and the optical element electrode of the semiconductor circuit board, and flip-chip connection cannot be performed.

Further, in the conventional optical element module, the thermal fatigue of the solder bump caused by the difference in thermal expansion between the semiconductor circuit board and the optical element has not been sufficiently taken into consideration. Generally, between the semiconductor circuit board and the optical element is 1.5 to 2.5 × 10 ⁻⁶ /
A difference in coefficient of thermal expansion of about ℃ occurs. That is, shear strain occurs in the solder bumps connecting the semiconductor circuit board and the optical element due to changes in the temperature environment. The shear strain corresponding to the change in the temperature environment causes metal fatigue to the solder bumps, and in some cases the solder bumps are cut off, which causes a defect of the optical element module. Further, the degree of metal fatigue of the solder bump is related to the height of the solder bump, and the higher the fatigue, the less the metal fatigue. Therefore, it is necessary to control the height of the solder bump in order to improve the reliability of thermal fatigue of the solder bump.

As described above, the conventional optical element module has a problem that the solder bumps are low and the life is short.

An object of the present invention is to provide an optical element module in which the semiconductor circuit substrate and the electrodes of the optical element can be easily flip-chip connected to each other and the thermal fatigue of the solder bumps can be reduced.

[0012]

In order to achieve the above-mentioned object, the present invention comprises a two-dimensional array of optical elements and a substrate connected to the two-dimensional array, and the electrodes of the two-dimensional array and the substrate. Spacers for adjusting the bonding interval with the electrodes are provided at a plurality of positions at least in the diagonal direction of the substrate electrodes around each electrode of the substrate.

Further, with the electrode height of the substrate being H, the spacer is made of an insulator having a height of 0.5 to 0.9H.

Further, the spacer has a shape covering the periphery of each electrode of the substrate.

[0015]

According to the above means, by providing the spacer between the electrode of the optical element two-dimensional array and the electrode of the substrate, it is possible to adjust the bonding interval only by pressing the optical element.
Flip chip connection without height adjustment is possible. The spacer is processed accurately. In addition, the spacers arranged diagonally around each electrode of the substrate can also adjust the electrode intervals at both ends of the substrate to the same height. Therefore, the fatigue life of the solder bump can be extended correspondingly to the height of the spacer.

Further, by forming the spacer with an insulator having a height of 0.5 to 0.9H, the solder bump on the substrate electrode and the electrode of the optical element are [1- (0.5 to 0.9)]. Since there is a connection margin of H, contact failure can be eliminated. In addition, it is possible to suppress lateral spread of the solder due to excessive crushing of the solder bumps. Therefore, contact between adjacent solder bumps can also be prevented. Further, even if the adjacent solder bumps contact the spacers, it is possible to prevent conduction between the solder bumps.

Further, since the spacer has a shape covering the periphery of each electrode of the substrate, it is possible to prevent the adjacent solder bumps from directly contacting each other.

[0018]

1 is a sectional view of an optical element module according to a first embodiment of the present invention. In FIG. 1, the optical element module 101 includes a two-dimensional optical element array 102, a semiconductor circuit board 103, a package 104, and a cap 105.
And an optical component 106. Two-dimensional optical element array 1
The electrode 107 of No. 02 and the electrode 108 of the semiconductor circuit substrate 103 are connected by the solder bump 109. The distance between the two-dimensional optical element array 102 and the semiconductor circuit board 103 is
It is held by the spacer 110. Two-dimensional optical element array 102 and optical component 10 fixed to cap 105
6 is optically coupled.

Each optical element of the two-dimensional optical element array 102 is composed of an InGaAs type surface emitting laser diode or an InGaAs type pin type photodiode having an oscillation wavelength of about 1 μm. The array spacing is 250 μm. An electrode 107 is formed on the surface of the two-dimensional optical element array 102. The electrode 107 is patterned after vapor deposition of Au / Ni / Ti.

The semiconductor circuit board 103 is composed of a GaAs-based or Si-based IC. On the semiconductor circuit board 103,
A material having a thermal expansion coefficient close to that of the two-dimensional optical element array 102 was selected. On the surface of the semiconductor circuit board 103, Au / Ni /
After depositing Ti, dry etching is performed and patterning is performed to form the electrode 108. The diameter of the electrode 108 is 50 μm. Semiconductor circuit board 10
On the back side of 3 for soldering to the package 104,
A vapor deposition film made of Au / Ni / Ti is formed.

The material of the solder bump 109 is Pb-5% Sn.
Consists of. By selectively depositing by a metal mask or photolithography, the semiconductor circuit board 10
3 was formed on the electrode 108. The solder bump 109 has a diameter of 50 μm and a height of 35 μm.

The package 104 includes a base 112, frames 113 and 114, and terminals 115. Base 11
2 is a high thermal conductivity Cu-W alloy, frames 113 and 114
Consists of alumina ceramics. The terminals 115 are connected to the semiconductor circuit board 103 by wiring members 118 made of a film carrier or wires. Base 11
2 and the surfaces of the frames 113 and 114 were plated with Au / Ni.

The cap 105 is made of Kovar alloy having a thermal expansion coefficient substantially equal to that of the package 104. An optical component 106 is sealed and fixed to the cap 105.

The optical component 106 comprises a gradient index microlens array. Microlenses having a diameter of 200 μm are arranged at an array interval of 250 μm.

The spacer 110 is made of photosensitive glass. A plurality of through holes having a diameter of 80 μm are formed at a pitch of 250 μm by photolithography. The height of the spacer 110 is 25 μm.

The mounting process of the optical element module 101 of the first embodiment will be described with reference to FIG.

First, each electrode 10 of the semiconductor circuit board 103
8 Spacers 110 are mounted so as to cover the periphery. After the alignment, the solder bumps 109 are melted and the electrodes 107 of the two-dimensional optical element array 102 and the electrodes 108 of the semiconductor circuit substrate 103 are flip-chip connected.

Next, the semiconductor circuit substrate 103 to which the two-dimensional optical element array 102 is connected is set to Pb-60% Sn solder 11
It is fixed to the package 104 by 7. The semiconductor circuit board 103 and the terminal 115 are connected by the wiring material 118.

Finally, after the two-dimensional optical element array 102 and the optical component 106 are aligned, the cap 105 to which the optical component 106 is fixed is welded to the package 104.

According to the first embodiment, the spacer 110 for adjusting the bonding distance between the two-dimensional optical element array 102 and the semiconductor circuit substrate 103 is provided around the electrodes 108 of the semiconductor circuit substrate 103 as shown in FIG. At least in a diagonal direction of the semiconductor circuit substrate 103 electrode 108.

By providing a spacer 110 between the two-dimensional optical element array 102 and the semiconductor circuit substrate 103 and adjusting the bonding interval, flip chip connection can be performed without adjusting the height. The spacer is processed accurately.

Further, each electrode 10 of the semiconductor circuit substrate 103
It is also possible to adjust the electrode intervals at both ends of the semiconductor circuit board 103 to be the same height by the spacers arranged in the diagonal direction around the periphery. Therefore, the fatigue life of the solder bump can be extended correspondingly to the height of the spacer.

As shown in FIG. 2, the height of the solder bump 109 is H (here, 35 μm), and the spacer 110 is made of an insulator having a height of 0.5 to 0.9 H (here, 25 μm). , The solder bumps 109 on the substrate electrodes 108 and the optical element electrodes 107 are [1- (0.5 to 0.9)].
There is a connection margin of H (here, 10 μm), and contact failure can be eliminated. Further, it is possible to suppress the lateral spread of the solder due to the excessive crush of the solder bump 109. Therefore, contact between the adjacent solder bumps 109 can be prevented. Further, the adjacent solder bumps 109 are separated from each other by the spacer 11
It is possible to prevent conduction between the solder bumps 109 even if the solder bumps 109 come into contact with zero.

Further, since the spacer 110 has a shape covering the periphery of each electrode 108 of the semiconductor circuit substrate 103, it is possible to prevent the adjacent solder bumps 109 from directly contacting each other.

According to the first embodiment, the semiconductor circuit board 10
3 electrode 108 and 2D optical element array 102 electrode 10
7 (the height of solder bump 109) with 7 without adjustment
It can be controlled to μm, flip chip connection can be easily performed, and thermal fatigue of solder bumps can be reduced.

The effect of the present invention is that the spacers to be arranged between the semiconductor circuit board and the two-dimensional array are provided at least at a plurality of positions in the diagonal direction around each electrode of the semiconductor circuit board, and the height of the solder bump 109 is increased. As H, the spacer 11
0 is formed of an insulator having a height of 0.5 to 0.9H, the spacer 110 is formed in a shape covering the periphery of each electrode 108 of the semiconductor circuit substrate 103, and a combination thereof is exerted.

For example, in the first embodiment, the spacers 110 are arranged at two diagonal positions, but they may be arranged around all electrodes. Depending on the purpose, it is possible to use a spacer composed of an insulator having a height of 0.5 to 0.9H. The shape of the through hole of the spacer may be a cylindrical shape, a quadrangular prism shape, a triangular prism shape, or the like depending on the purpose.

FIG. 3 is a sectional view of the optical element module of the second embodiment according to the present invention. In FIG. 3, the optical element module 301 includes a two-dimensional optical element array 102, a semiconductor circuit board 103, a package 104, and a cap 10.
5, an optical component 302, and a fiber array 304. The electrodes 107 of the two-dimensional optical element array 102 and the electrodes 108 of the semiconductor circuit board 103 are connected by solder bumps 109. The space between the two-dimensional optical element array 102 and the semiconductor circuit board 103 is maintained by the spacer 110. The two-dimensional array 102 and the fiber array 3042 fixed to the cap 105 are optically coupled.

The individual optical elements of the two-dimensional optical element array 102 are surface emitting laser diodes or photodiodes. The array spacing is 250 μm. Electrodes 107 are formed on the front surface of the two-dimensional optical element array 102, and alignment marks 111 are formed on the back surface. The alignment mark 111 has a line width of 2 μm and a line length of 5 μm.

The semiconductor circuit board 103 is composed of an LSI.
An electrode 108 is formed on the surface of the semiconductor circuit board 103. The diameter of the electrode 108 is 20 μm. The solder bumps 109 formed on the electrodes 108 of the semiconductor circuit board 103 have a diameter of 20 μm and a height of 20 μm. The semiconductor circuit board 103 has Pb-60% in the package 104.
It is fixed with Sn solder 117.

The package 104 comprises a base 112, frames 113 and 114, and terminals 115. Terminal 115
Are connected to the semiconductor circuit board 103 by wiring members 118. The optical component 302 and the guide 303 are sealed and fixed to the cap 105.

The optical component 302 is made of photosensitive glass. Diameter of 1 at 250 μm pitch by photolithography
A plurality of 30 μm pinholes are formed. The fiber array 304 is inserted into this pinhole. On the surface facing the two-dimensional optical element array 102,
The alignment mark 116 is formed. Alignment mark 1
The line width of 16 is 2 μm, and the line length is 5 μm.

The fiber array 304 has an outer diameter of 125 μm.
It consists of a single mode optical fiber. A tip lens 305 having a radius of 30 μm is formed on the tip by etching and electric discharge machining. Fiber array 304
Are fixed to the guide 303 by low melting point glass.

The guide 303 is made of zirconia ceramics. By precision machining, pin holes having a diameter of 126 μm and an array interval of 250 μm are formed with an accuracy of ± 1 μm. The guide 303 is fixed to the cap 105 with a high melting point solder material and seals the package 104.

The spacer 110 is made of a photosensitive insulator. 15 μm of photosensitive insulator on the semiconductor circuit board 103
250 μm by photolithography after coating
A plurality of through holes having a diameter of 30 μm are formed at a pitch.

The optical element module 301 of the second embodiment is
It was assembled by the following mounting process. After forming the spacer 110 on the semiconductor circuit board 103, the electrodes 107 of the two-dimensional optical element array 102 and the electrodes 108 of the semiconductor circuit board 103 are flip-chip connected by the solder bumps 109. The semiconductor circuit substrate 103 to which the two-dimensional optical element array 102 is connected is fixed to the package 104. The semiconductor circuit board 103 and the terminal 115 are connected by the wiring material 118. After the alignment mark 111 formed on the two-dimensional optical element array 102 and the alignment mark 116 formed on the optical component 302 are aligned, the cap 105 to which the optical component 302 is fixed is welded to the package 104. Finally, the fiber array 304 fixed to the guide 303 is inserted into the pinhole of the optical component 302, and the fiber array 304 is driven while driving the two-dimensional optical element array 102.
The optical axis is aligned and the guide 303 is fixed to the cap 105.

According to the second embodiment, the spacer 110 is made of a photosensitive insulator so that the distance between the two-dimensional optical element array 102 and the electrodes 107 and 108 of the semiconductor circuit substrate 103 can be controlled within ± 2 μm without adjustment. Therefore, flip chip connection can be easily performed, and reliability of thermal fatigue of solder bumps can be improved.

Further, by merely inserting the fiber array 304 fixed to the guide 303 into the pinhole provided in the optical component 302, the alignment of the two-dimensional optical element array 102 and the fiber array 304 is performed with an accuracy of ± 5 μm. .
As a result, the two-dimensional optical element array 102 and the fiber array 304 are roughly optically coupled. Therefore, by driving the two-dimensional optical element array 102, the optical axes of the two-dimensional optical element array 102 and the fiber array 304 can be accurately aligned with an accuracy of ± 3 μm while measuring the amount of combined light.

[0049]

According to the present invention, since the spacer is provided between the two-dimensional optical element array and the semiconductor circuit board, it is easy to adjust the bonding interval. In addition, the fatigue life of the solder bump can be extended.

Setting the height of the spacers to 0.5 to 0.9H is effective in eliminating electrode connection failure.

Covering the periphery of each electrode of the semiconductor circuit board with the shape of the spacer is effective in eliminating electrode connection failure.

[Brief description of drawings]

FIG. 1 is a sectional view of an optical element module showing a first embodiment according to the present invention.

FIG. 2 is an explanatory diagram of the assembly of the optical element and the substrate according to the first embodiment of the present invention.

FIG. 3 is a sectional view of an optical element module showing a second embodiment according to the present invention.

[Explanation of symbols]

101 ... Optical element module, 102 ... Two-dimensional optical element array, 103 ... Semiconductor circuit board, 104 ... Package, 1
05 ... Cap, 106 ... Optical component, 107, 108 ... Electrode, 109 ... Solder bump, 110 ... Spacer, 111,
116 ... Alignment mark, 112 ... Base, 113, 11
4 ... Frame, 115 ... Terminal, 117 ... Pb-60% S
n solder, 118 ... Wiring material.

Claims (3)

[Claims] 1. A two-dimensional array of optical elements and a substrate connected to the two-dimensional array, wherein a spacer for adjusting a bonding interval between an electrode of the two-dimensional array and an electrode of the substrate is provided on the substrate. 2. An optical element module having at least a plurality of locations around each electrode in a diagonal direction of the substrate electrode. 2. The optical element module according to claim 1, wherein the electrode height of the substrate is H, and the spacer is made of an insulator having a height of 0.5 to 0.9H. 3. The optical element module according to claim 1, wherein the spacer has a shape that covers the periphery of each electrode of the substrate.