JP2002289957A - Package for housing optical semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve mounting reliability to the external circuit board of a relatively large thermal expansion coefficient and the mounting reliability to the package of an optical semiconductor element, to prevent position deviation of the optical semiconductor element housed inside the package and an optical fiber, and to prevent the degradation of the conversion efficiency of signals. SOLUTION: The package A for housing the optical semiconductor element is provided with a ceramic wiring board 1, provided with an optical semiconductor element loading part on an upper surface, a frame body 2 attached on the wiring board 1, so as to surround the loading part of the optical semiconductor element 4 and provided with an inlet part 9 for introducing optical signals, a lid member 3 attached to the upper surface of the frame body 2 for sealing the optical semiconductor element 4 and a connection terminal 13 for connecting the external circuit board B on the surface on the opposite side of the loading part of the optical semiconductor element 4 of the wiring board 1. The loading part of the optical semiconductor element 4 of the wiring board 1 is provided with a conductor layer 7 for attaching the optical semiconductor element 4, and the conductive layer 7 is attached and formed in a mesh shape or a stripe shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor element housing package for housing an optical semiconductor element therein.

[0002]

2. Description of the Related Art Conventionally, an optical semiconductor element housing package for housing an optical semiconductor element generally seals a concave metal container such as an Fe / Ni / Co alloy or a Cu / W alloy and an opening of the container. It consists of a metal lid for
A mounting portion for mounting and fixing the optical semiconductor element is provided at the center of the bottom of the metal container. In addition, on the side wall portion of the metal container, a wiring board provided with a wiring conductor layer on the surface of an insulating substrate made of ceramics such as alumina and an introduction portion for introducing an optical fiber are provided through the side wall portion. It has a structure in which a signal sent from an optical fiber is converted into an electric signal by an optical semiconductor element and transmitted to an external circuit through a wiring board.

[0003] Recently, as components become lighter and thinner, a form in which a package is mounted on a predetermined external circuit board is required. In response to this requirement, recently, a wiring conductor layer made of tungsten has been formed on the surface or inside of a ceramic insulating substrate made of alumina or the like using a conventionally known multilayer ceramic processing technique, and the optical semiconductor element mounting portion has been formed on the surface. There is also proposed a package in which a cavity is formed by mounting a frame so as to surround the mounting portion, and the cavity is sealed by a lid. In this package, lead terminals are attached to the side and bottom of the wiring board and mounted by soldering, or pin terminals are attached to the bottom and mounted on the external circuit board by vertically inserting pins into the external circuit board It has also been suggested.

[0004]

With the recent expansion of optical communication, it has been required to automate the mounting of the optical semiconductor element housing package on an external circuit board. In the case of the package used, the lead terminals are usually set to be long to reduce the generation of stress in the mounting of the package and the external circuit board. There is a problem that the transmission of the high-frequency signal fluctuates due to a shift due to a problem that the amount of solder cannot be made constant. Further, in the case where the pin terminal is used, there is a problem that the inserted pin protrudes from the external circuit board, thereby increasing the reflection loss of the high-frequency signal.

In order to solve these problems, it is conceivable to mount directly by soldering in a ball shape or the like instead of the lead terminal or the pin terminal. Generally, an optical semiconductor element has a thermal expansion coefficient of about 5 to 7 × 10 ⁻⁶ / ° C., while an external circuit board contains an organic resin as an insulating material and has a thermal expansion coefficient of 10 to 15 × 10 −10. ^It consists of a so-called printed wiring board of ^-6 / ° C. Therefore, when the package is formed of ceramics such as alumina, the alumina ceramics has a thermal expansion coefficient of 6 to 7 × 10 ⁻⁶ / ° C., which is close to that of the optical semiconductor element, so that the mounting reliability for the optical semiconductor element is high. However, since the thermal expansion difference between the external circuit board and the external circuit board is large, there is a problem in reliability of mounting on the external circuit board.

In order to solve this problem, if the package is formed of ceramics having a high thermal expansion, the reliability of mounting the package on an external circuit board is improved, but the difference in thermal expansion between the package and the optical semiconductor element is increased. The mounting reliability is reduced, and a stress is generated in the optical semiconductor device mounted on the package due to a difference in thermal expansion, and the stress causes a displacement between the optical semiconductor device and the optical semiconductor device. However, there is a problem in that the conversion efficiency of the signal is reduced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the mounting reliability of an external circuit board having a relatively large coefficient of thermal expansion and the mounting reliability of an optical semiconductor device in a package. It is an object of the present invention to provide a package for housing an optical semiconductor element in which a displacement with respect to a fiber is prevented and deterioration of signal conversion efficiency is prevented.

[0008]

Means for Solving the Problems As a result of repeated studies on the above problems, the present inventors attach the optical semiconductor element to the surface of the ceramic wiring board when mounting the optical semiconductor element in the package. A conductive layer is formed through the conductive layer, and the optical semiconductor element is mounted through the conductive layer. By processing the conductive layer into a mesh shape or a stripe shape, the thermal expansion of the ceramic wiring board is increased, and the external circuit board is formed. It is found that even when the thermal expansion of the optical semiconductor device is approximated, a highly reliable package for storing the optical semiconductor device without deteriorating the optical signal can be obtained without any influence on the mounting of the optical semiconductor device. Invented the invention.

That is, an optical semiconductor element housing package of the present invention comprises a ceramic wiring board having an optical semiconductor element mounting portion on an upper surface, an optical semiconductor element mounting portion surrounding the optical semiconductor element mounting portion, the optical semiconductor element mounting portion mounted on the wiring substrate, A frame provided with an introduction portion for introducing a signal, and a lid member attached to an upper surface of the frame and sealing the optical semiconductor element; and On the surface on the side opposite to the element mounting portion, having a connection terminal for connecting to an external circuit board, the optical semiconductor element mounting portion of the wiring board, for mounting an optical semiconductor element A conductor layer is provided, and the stress applied to the optical semiconductor element can be reduced by forming the conductor layer in a mesh shape or a stripe shape.

Further, according to the present invention, the wiring board includes:
It is composed of a wiring conductor layer and an insulating substrate. When the thermal expansion coefficient of the insulating substrate is at least 8 × 10 ⁻⁶ / ° C., it can be applied to an external circuit board such as a printed wiring board containing an organic resin of a package. Mounting reliability can be improved.

When the conductor layer is in the form of a mesh, one size of each gap of the mesh is set to 0.25 to 4 mm.
^In the case of a stripe shape, the width of the gap is preferably 0.5 to 2 mm in order to sufficiently exert the effects of the present invention.

Preferably, the mesh-shaped or stripe-shaped conductor layer and the wiring conductor layer are made of a low-resistance conductor material mainly composed of copper or silver in order to reduce transmission loss of a high-frequency signal.

[0013] The insulating substrate of the wiring substrate is set at 1000 ° C.
By using a low-temperature fired ceramic material that can be fired below, it can be fired simultaneously with the mesh-shaped or stripe-shaped conductor layer or the wiring conductor layer.
Further, according to the present invention, it is particularly effective when the connection terminal is made of solder.

According to the package for housing an optical semiconductor element of the present invention, as described above, the conductor layer provided on the portion of the wiring substrate on which the optical semiconductor element is mounted is formed in a mesh shape or a stripe shape, whereby the wiring is formed. Even when the difference in thermal expansion between the insulating substrate and the optical semiconductor element constituting the substrate is large, the stress caused by the difference in thermal expansion can be reduced by the mesh-shaped or stripe-shaped conductor layer. In addition to preventing deterioration during transmission of an optical signal to the optical semiconductor element, the insulating substrate can be matched to the thermal expansion of the external circuit board, and the reliability of mounting the package on the external circuit board can be improved. it can.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic plan view (a) for explaining an example of an optical semiconductor element housing package of the present invention,
(B) It is vv sectional drawing of (a). In FIG. 7A, the lid member is omitted for convenience of explanation. In the figure, 1 is a ceramic wiring board, 2 is a frame, and 3 is a lid member. A cavity is formed by the wiring board 1, the frame 2 and the lid member 3,
The optical semiconductor element 4 is accommodated in this cavity.

The wiring board 1 includes an insulating substrate 5 and a wiring conductor layer 6.
A mounting portion for mounting the optical semiconductor element 4 is formed substantially at the center of the upper surface of the wiring substrate 1 on the cavity side. A conductor layer 7 for bonding and fixing the optical semiconductor element 4 is formed on the mounting portion. For example, an optical semiconductor in which a photoelectric conversion element section 4b is formed on an optical semiconductor element substrate 4a made of silicon or the like. The element 4 is bonded and fixed to the conductor layer 7 with a solder material (not shown) such as gold-germanium.

The frame 2 is made of ceramics or metal. In order for the optical signal from the optical fiber 8 to reach the photoelectric conversion element 4b, the frame 2 has an introduction portion 9 for introducing the optical fiber 8. Are formed. For example, a through hole 10 that penetrates the frame 2 is formed in the introduction portion 9, and the optical fiber 8 is formed in the through hole 10.
Is fixed to the outer surface of the through hole 10 with a brazing material. A conductor layer (not shown) is previously formed on the attachment surface of the fixing member 11 of the frame 2, and a nickel plating layer or a gold plating layer is applied to the surface of the conductor layer, and the fixing member 11 is brazed. The fixing member 11 is firmly fixed to the frame body 2 with enhanced properties.

The optical fiber 8 is supported through the cylindrical fixing member 11, is introduced into the cavity through the through hole 10, and is arranged so that an optical signal can be transmitted and received between the optical semiconductor elements 4. Have been. In addition, the cylindrical fixing member 1
The optical fiber 1 and the optical fiber 8 are fixed by a solder material, resin sealing or the like.

On the upper surface of the frame 2, for example, Fe-N
A cover member 3 made of a metal material such as an i-Co alloy or an Fe-Ni alloy is joined by welding such as a seam welding method,
The inside of the cavity is hermetically sealed.

Further, connection terminals 13 are attached to the lower surface of the wiring board 1 via connection pads 12. In this example, a ball-shaped solder is attached as the connection terminal 13.

The package A is mounted on an external circuit board B. The external circuit board B includes an insulating base 14.
Pad 15 for mounting package A on the surface of
Are formed, and as shown in FIG.
Means that the connection pads 12 on the package A side are connected to the external circuit board B
Connection pad 15 and connection terminal 13 made of ball-shaped solder
The connection is fixed.

In the package A on which the optical semiconductor element 4 according to the present invention is mounted, it is very important to prevent the occurrence of a displacement between the optical fiber 8 and the photoelectric conversion element 4a in order to increase the signal conversion efficiency. . This displacement is determined by the reliability of the mounting on the conductor layer 7 on the insulating substrate 5 in the package A on which the optical semiconductor element 4 is directly mounted.

As will be described later, the thermal expansion coefficient of the insulating substrate 5 tends to increase in order to enhance the reliability of the secondary mounting of the package A on the external circuit board B, and therefore, the thermal expansion coefficient with the optical semiconductor element 4 increases. The mounting reliability due to the difference is reduced, distortion occurs in the mounting portion of the optical semiconductor element 4, and the signal conversion efficiency is deteriorated due to displacement of the optical semiconductor element 4 from the optical fiber.

Therefore, according to the present invention, the optical semiconductor element 4
It is important to form the conductor layer 7 formed on the mounting portion on which is mounted a mesh or stripe pattern. By making the pattern of the conductor layer 7 for attaching the optical semiconductor element 4 into a mesh shape or a stripe shape, the binding force of the conductor layer 7 of the optical semiconductor element 4 is reduced, and as a result, the distance between the insulating substrate 5 and the optical semiconductor element 4 is reduced. The stress caused by the difference in thermal expansion can be reduced from being applied to the optical semiconductor element 4, the thermal strain generated by a change in environmental temperature can be reduced, and the deterioration of the photoelectric conversion efficiency can be prevented. For example, even when left at a high temperature of 150 ° C. for 1000 hours, there is no influence of thermal strain.

When the conductor layer 7 has a mesh shape, in order to exhibit the above effects, as shown in FIG. 2, the gaps x present in the gaps between the conductors are each 0.25 mm ² or more. desirable. More specifically, if it is smaller than 0.25 mm ² , a sufficient effect of relieving stress cannot be exhibited, and optical coupling loss tends to increase.

On the other hand, the size of the gap x is 0.25 m
By setting m ² or more, the amount of displacement between the light emitting source and the optical fiber can be made 0.02 μm or less, and the optical coupling loss can be suppressed to 0.2 dB or less. In particular, by setting the size of the void portion to 1.0 mm ² or more,
Further, the displacement between the light emitting source and the optical fiber can be reduced to 0.01 μm or less, and the optical coupling loss can be suppressed to 0.1 dB or less.

Considering only the optical coupling loss surface, the larger the gap x is, the more advantageous it is. However, if the area of the conductor layer 7 is reduced, there is a possibility that the junction reliability of the optical semiconductor element is reduced. The gap x of the present invention is preferably 4 mm ² or less, particularly preferably 3 mm ² or less.

The conductor width between the gaps x is 0.2 to 1
If mm is appropriate, and if it is smaller than 0.2 mm, deficiencies are likely to occur from the viewpoint of connection reliability of the optical semiconductor element 4, and if it exceeds 1 mm, the effect of forming the gap a is small.

Further, according to the present invention, the conductor layer 7 for attaching the optical semiconductor element 4 can be formed in a stripe shape as shown in FIG. In the case of a stripe shape, the width of the gap y between the conductors is suitably 0.5 to 2 mm,
Further, it is desirable that the width of the conductor is 0.5 to 2 mm. When the width between the gaps is smaller than 0.5 mm, the optical coupling loss increases.

According to the present invention, the connection terminals 13 of the package for storing an optical semiconductor element are formed by solder such as ball solder as described above, and the connection pads 1 on the package A side are formed.
When the package 2 and the connection pads 15 on the external circuit board B are directly connected by soldering, the height between the connection pads between the package A and the external circuit board B is very low, and this is caused by the difference in thermal expansion between the two. The stress cannot be absorbed by the solder, and cracks or the like occur around the solder or the connection pad serving as the connection terminal, thereby increasing the connection resistance and impairing the mounting reliability.

Therefore, when the connection terminals 13 made of solder as described above are used, in order to increase the reliability of mounting the package A on the external circuit board B, the thermal expansion of the insulating base 14 constituting the external circuit board B is performed. It is desirable to approximate the coefficient and the coefficient of thermal expansion between the insulating substrate 5 in the package A for housing an optical semiconductor element.

Generally, the external circuit board B is an insulating substrate containing an organic resin such as a woven or non-woven fabric made of glass or the like impregnated with a thermosetting resin such as an epoxy resin, as called by the name of FR-4. A wiring circuit layer formed of metal foil is used. Such an external circuit board,
Usually, the coefficient of thermal expansion at 25 to 200 ° C. is 10 to 15
× 10 ^-6 / ° C.

Accordingly, the insulating substrate 5 in the package A for housing an optical semiconductor element of the present invention has a coefficient of thermal expansion at 25 to 200 ° C. of 8 × 10 ⁻⁶ / ° C. or more, particularly 10 × 10 ^−6.
/ ° C or higher. Further, the coefficient of thermal expansion of the insulating base 14 constituting the external circuit board B and the 25 to 2
It is desirable that the maximum thermal expansion coefficient difference at 00 ° C. is 2 × 10 ⁻⁶ / ° C. or less.

(Insulating Substrate) According to the package of the present invention, the ceramic insulating substrate 5 in the wiring board 1 is made of a conventionally known ceramic insulating substrate material, and is made of alumina, mullite, forsterite, aluminum nitride,
It can be formed of at least one selected from the group consisting of silicon nitride and glass ceramics.

In particular, among these, ceramics which can be fired at a low temperature of 1000 ° C. or less so as to be able to be fired simultaneously with the above-mentioned Cu and Ag are preferably used. In particular, glass ceramics generally have low dielectric loss, This is particularly useful for the package of the present invention in that the dielectric constant can be arbitrarily controlled from a low dielectric constant to a high dielectric constant, and the coefficient of thermal expansion can be arbitrarily controlled.

This glass ceramic has a glass component,
Alternatively, it is obtained by firing a mixture of a glass component and a filler component. In particular, in order to enhance the strength of the wiring board, the filler component is used in the form of glass: filler of 5:95 to 9: 9.
A composition obtained by calcining a composition mixed at a volume ratio of 5: 5 is suitably used.

As the glass component used, at least
Also SiO_TwoContaining, Al_TwoO_Three, B_TwoO _Three, ZnO, Pb
O, alkaline earth metal oxide, alkali metal oxide
By containing at least one kind and firing
Is also amorphous,
Light, mullite, anorthite, Sergien, spinet
Le, Garnite, Willemite, Dolomite, Petalai
At least one kind of crystals of
Crystallized glass is used.

The filler component includes calcium zirconate, strontium silicate, calcium titanate, strontium titanate, barium titanate, alumina, quartz, cristobalite, quartz glass, mullite, forsterite, zirconia, spinel, cordierite, anorthite. It is preferable to use crystallized glass that precipitates at least one kind of crystal of Celsian, garnite, willemite, dolomite, petalite or a substituted derivative thereof, from the viewpoint of exhibiting good electric characteristics and improving strength.

In particular, ceramics having a thermal expansion coefficient of 8 × 10 ⁻⁶ / ° C. or more include, for example, BaO-based glass having a low softening point and a high thermal expansion containing BaO at a ratio of 5 to 60% by weight, and others. For example, as described in the specification of Japanese Patent Application No. 8-3222038, glass components such as lithium silicate glass, PbO glass, and ZnO glass are used for SiO ₂ (quartz), enstatite, and the like. , Forsterite, MgO, ZrO ₂ , petalite, and the like, and various high-thermal-expansion ceramic filler components are mixed.

According to the present invention, when the frame 2 is formed of ceramics, if the frame 2 is formed of ceramics that can be fired at the same firing temperature as the wiring board 1, the wiring board 1 and the frame 2 are integrally fired. Can be

(Conductor Material) The conductor layer 7 for fixing the optical semiconductor element 4 and the wiring conductor layer 6 and the connection pads 12 in the wiring board 1 are made of a conventionally known conductor material such as W, Mo, It is formed of a conductor material mainly composed of at least one kind selected from the group consisting of Mn, Cu, and Ag. Alternatively, it can be formed of a conductive material mainly containing a low-resistance metal such as Ag or Ag. The conductor layer 7 and the connection pad 12 are made of a metal having excellent corrosion resistance and good wettability to a brazing material, specifically, a Ni layer having a thickness of 1.5 to 6 μm and a thickness of 0.2 to If a 5 μm Au layer is sequentially applied by a plating method, the oxidative corrosion of the wiring substrate 1 can be effectively prevented, and the optical semiconductor element 4 on the upper surface of the wiring substrate 1 is firmly adhered and fixed with a brazing material. Can be.

[0042]

EXAMPLES The following experiments were conducted to confirm the effects of the present invention. SiO ₂ as a wiring board: 43.9 wt% -BaO: 23.2 wt% -B ₂ O _3: 13.6 wt% -Al ₂ O _3: 7.0 wt% -CaO: 12.3 wt%
A composition prepared by mixing 40% by volume of quartz (SiO ₂ ) as a filler with 60% by volume of glass composed of
An insulating substrate is formed using a glass-ceramic having a thermal expansion coefficient of 11 × 10 ⁻⁶ / ° C. at a temperature of 25 to 200 ° C. manufactured by firing at 50 ° C., and a wiring conductor layer and an optical semiconductor element in the wiring substrate are formed. A conductor layer for mounting was formed by simultaneous firing with an insulating substrate using copper metallization. Further, a ball solder terminal made of eutectic solder was attached to the connection pad on the bottom surface of the wiring board. Then, the pattern of the conductor layer on which the optical semiconductor element was mounted was formed in a mesh shape or a stripe shape having a predetermined gap. Then, an optical semiconductor element having an optical semiconductor circuit formed on a silicon substrate was adhered to the conductive layer using eutectic solder.

Printed wiring in which connection pads made of copper foil are formed on the surface of an insulating substrate (coefficient of thermal expansion of 25 to 200 ° C. 14 × 10 ⁻⁶ / ° C.) in which this package is impregnated with epoxy resin in a glass woven fabric. The package was mounted on the surface of the substrate and surface-mounted using eutectic solder.

In the manufactured optical semiconductor device package, the displacement between the light emitting source and the optical fiber was measured, and
Optical coupling loss was measured. The package mounted on a printed circuit board was repeatedly applied with a thermal cycle of -40 to 85 ° C., so that the resistance value of the solder joint was 1.5 times the initial value.
Tables 1 and 2 show that the number of cycles until the number of
It was shown to.

[0045]

[Table 1]

[0046]

[Table 2]

As is clear from the results of Tables 1 and 2, when the conductor layer on which the optical semiconductor element is mounted is a solid pattern (Sample No. 1), the optical coupling loss is as large as 0.6 dB. The optical coupling loss could be reduced to 0.5 dB or less by forming the conductor layer in a mesh shape or a stripe shape.

In particular, when the conductor layer is in the form of a mesh, the gap between the light emitting source and the optical fiber is reduced to 0.02 μm or less by setting the gap of the mesh to 0.25 mm ² or more. It could be 2 dB or less. In particular, by setting the size of the gap to 1.0 mm ² or more, the amount of misalignment between the light emitting source and the optical fiber is reduced to 0.01 mm.
μm, and the optical coupling loss could be suppressed to 0.1 dB or less.

However, if the size of the gap is larger than 1 mm ² , the reliability in the heat cycle test tends to gradually decrease, and if it exceeds 4 mm ² , the heat cycle test results in less than 500 cycles. , It turned out that the environment to use was limited. In the case where the conductor layer was in a stripe shape, a remarkable effect was observed when the gap was 0.5 mm or more.

[0050]

As described above in detail, according to the package for housing an optical semiconductor device of the present invention, the optical semiconductor device and the electric signal can be smoothly transmitted from the optical fiber, so that the mounting reliability is improved, the cost is reduced, and the environment is reduced. Can contribute to stabilization of light characteristics with respect to

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an example of an optical semiconductor element housing package of the present invention.

FIG. 2 is a plan view for explaining a pattern of a mesh-shaped conductor layer.

FIG. 3 is a plan view for explaining a pattern of a stripe-shaped conductor layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic wiring board 2 Frame 3 Cover member 4 Optical semiconductor element 4a Optical semiconductor element substrate 4b Photoelectric conversion element 5 Insulating substrate 6 Wiring conductor layer 7 Conductor layer 8 Optical fiber 9 Introducing part 10 Through hole 11 Fixing member

Claims (7)

[Claims] 1. A ceramic wiring board having an optical semiconductor element mounting portion on an upper surface, and an introduction portion mounted on the wiring substrate so as to surround the optical semiconductor element mounting portion and for introducing an optical signal. A frame, a lid member attached to the upper surface of the frame, and sealing the optical semiconductor element,
And an optical semiconductor element storage package having a connection terminal for connecting to another circuit board on a surface of the wiring board opposite to the optical semiconductor element mounting portion, wherein The semiconductor element mounting portion is provided with a conductor layer for attaching the optical semiconductor element, and the conductor layer is formed in a mesh shape or a stripe shape. package. 2. The wiring board comprises a wiring conductor layer and an insulating substrate, wherein the insulating substrate has a thermal expansion coefficient of 8 ×.
2. The package for housing an optical semiconductor element according to claim 1, wherein the temperature is 10 ^-6 / ° C. or higher. 3. The package for housing an optical semiconductor element according to claim 1, wherein one size of each void portion of said mesh-shaped conductor layer is 0.25 to ⁴ mm ² . 4. The package for housing an optical semiconductor element according to claim 1, wherein the width of the gap in said striped conductor layer is 0.5 mm or more. 5. The package for housing an optical semiconductor element according to claim 1, wherein said mesh-shaped or stripe-shaped conductor layer and said wiring conductor layer are made of a conductor material mainly composed of copper or silver. . 6. The package for housing an optical semiconductor element according to claim 1, wherein said connection terminals are made of solder. 7. The package according to claim 1, wherein the insulating substrate of the wiring substrate is made of a low-temperature fired ceramic material fired at 1000 ° C. or lower.