JP2000243981A - Optical module - Google Patents

Abstract

(57) [Problem] To provide an optical module having a configuration capable of increasing the size of an electronic circuit. SOLUTION: An internal lead pin 8 is provided on a lead frame 2.
And pad connecting portion 8a connected to external lead pin 10
And 10a, and an electrode pad is provided on the lower surface of the wiring board 20. By electrically connecting the pad connection portions 8a and 10a and the electrode pads using a conductive connection material, the area for wire wiring can be eliminated, and the size of the wiring board 20 can be increased. In addition, by arranging the auxiliary member 30 having the same material and shape as the wiring board 20 on the lower surface side of the lead frame 2, it is possible to reduce stress caused by a difference in thermal expansion coefficient between the wiring board 20 and the sealing resin after sealing. In addition, distortion and cracking of the resin can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module having an optical element which is a light receiving element or a light emitting element.

[0002]

2. Description of the Related Art A receiving module which includes a light receiving element and converts an optical signal transmitted by an optical fiber into an electric signal and outputs the electric signal, or a light emitting element which converts an electric signal into an optical signal and sends it to the optical fiber. Optical modules such as transmission modules are used in optical communication systems such as optical data links and optical LANs. As such a conventional optical module, for example, Japanese Utility Model Laid-Open No. 2-126107,
No. -278212.

An optical module is composed of an optical element which is a light receiving element or a light emitting element, and an electronic circuit connected to the optical element. In a conventional optical module, circuit components and wiring patterns constituting an electronic circuit are formed on an island portion (substrate portion) of a substrate or a lead frame functioning as a substrate. They are connected by wire bonding. The electronic module is configured by integrally molding the electronic circuit and the substrate and each component such as a metal package including the optical element with an insulating molding resin.

[0004]

However, in the above-mentioned optical module, since the connection between the electronic circuit on the wiring board and the lead frame is performed by wire bonding, the area for the wires to be wired is formed on the board. It is necessary to provide around. For this reason, the area of the wiring board for forming an electronic circuit cannot be increased.

On the other hand, an optical element mounting section and an electronic circuit mounting section are provided on a lead frame, and an optical element and an electronic circuit are mounted on each mounting section, and the optical element mounting section and the electronic circuit mounting section are mounted. There are optical modules separately molded with transparent resin (Proceedings of 48th Elec
tronic Components & Technology Conference (1998),
p.1199.). According to such a structure, the optical element and the electronic circuit are mounted collectively on the same lead frame.

In the structure described above, the lead frame is formed by a method such as etching a plate material or punching with a press machine, thereby forming a wiring pattern of an electronic circuit. However, in the wiring using the lead frame formed from one sheet material in this manner, cross wiring in which two or more wirings cross cannot be performed, and the degree of freedom of the configuration of the electronic circuit is limited. On the other hand, it is conceivable to realize wire crossing by performing wire bonding on a portion that requires crossing, but at this time, impedance mismatch occurs and circuit characteristics of the electronic circuit deteriorate.

When a wiring pattern is formed by a lead frame, external lead pins are also formed at the same time, so that the thickness of the lead frame (0.2 to 0.25) is required.
It is difficult to form a wiring pattern with a wiring pitch of about (mm) or less due to conditions such as the strength and ease of handling of the lead frame. Therefore, it cannot respond to an increase in the scale of an electronic circuit.

The present invention has been made in view of the above problems, and has as its object to provide an optical module having a configuration capable of increasing the size of an electronic circuit.

[0009]

In order to achieve the above object, an optical module according to the present invention comprises an optical signal having a predetermined wavelength and an electric signal corresponding to the optical signal, the signal being used for converting the other signal into the other signal. An optical module comprising: an optical element for converting the electronic circuit; an electronic circuit for processing the electric signal; and a lead frame having lead pins connected to the electronic circuit, wherein at least a part of the electronic circuit is formed. A wiring board fixed to one surface side of the lead frame, wherein the electronic circuit on the wiring board and the lead frame are provided with an electrode pad provided on the wiring board and a pad provided on the lead frame. The connection portion is electrically connected by being directly connected, and the wiring board and the pad connection portion of the lead frame are electrically connected. The electronic circuit sealing portion is formed by sealing the electronic circuit sealing portion on the one side of the lead frame on the side opposite to the lead frame of the wiring board. The difference between the thickness from the surface and the thickness of the sealing resin on the other surface side of the lead frame,
The thickness is smaller than the thickness of the wiring board.

In the above-described optical module, an electronic circuit is configured using not only circuit components and a wiring pattern of a lead frame but also a wiring board mounted on the lead frame. Thereby, the degree of freedom of the configuration of the electronic circuit can be increased, for example, it is possible to form the cross wiring in the substrate. Further, the wiring pitch can be made sufficiently small, and it is possible to cope with an increase in the size of an electronic circuit.

Further, a pad connection portion is provided on the lead frame so as to face an electrode pad of the wiring substrate without using wire bonding for electrical connection between the electronic circuit on the wiring substrate and the lead frame. Then, the electrode pad and the pad connection portion are fixedly and electrically connected using a conductive connection material or the like. At this time, it is not necessary to provide a region for wiring wires around the wiring board, and wiring pads of the lead frame are not required. Therefore, the wiring board can be enlarged and the electronic circuit can have a larger area.

In the case of such a configuration, a wiring board and
Since the coefficient of thermal expansion is significantly different from that of the resin forming the electronic circuit sealing portion by sealing the wiring board, there is a problem that the resin is broken after the sealing. In particular, when the sealing resin of the electronic circuit sealing portion is a transparent resin, since the amount of the filler added to the transparent resin is small, for example, the thermal expansion coefficient of a transparent epoxy resin is smaller than that of a normal epoxy resin. About 6.2 to 10.2 × 10 ⁻⁵ / ° C., which is at least twice as large. On the other hand, alumina (A
The thermal expansion coefficient of a ceramic substrate such as l ₂ O ₃ ) is, for example, 5.
It is about 5 × 10 ⁻⁶ / ° C., and there is a difference of 10 times or more between the two. Further, the difference between the ordinary epoxy resin and the transparent epoxy resin is slightly smaller than that of the transparent epoxy resin, but has the same problem.

In particular, when the wiring board is mounted on the lead frame, if the upper and lower sides of the lead frame are made of the same thickness of sealing resin from the respective surfaces of the lead frame, the sealing resin on the surface on which the wiring board is mounted is provided. The thickness of the sealing resin becomes smaller by the thickness of the wiring board than the thickness of the sealing resin on the other surface side. At this time, due to the asymmetry of the structure in the sealing portion, the balance of the stress generated in each resin portion is broken, thereby generating a portion where excessive stress is concentrated in the sealing resin, and distortion and cracks are generated in the sealing resin. Will occur.

On the other hand, in the optical module described above, the shape of the sealing portion, the arrangement of the wiring substrate in the sealing resin,
The difference between the thickness of the sealing resin excluding the wiring board on the upper side of the lead frame and the thickness of the sealing resin on the lower side of the lead frame is made smaller than the thickness of the wiring board by additional installation of other members. I do. As a result, generation of excessive stress and concentration of the stress are alleviated, and distortion and cracking of the sealing resin can be prevented, thereby realizing a highly reliable resin mold package. In addition, the thickness of the resin mold package can be reduced. As described above, an electronic module having a configuration in which the electronic circuit is enlarged and the stability and durability of the product are maintained is realized.

The above thickness conditions for the sealing resin on both the upper and lower sides of the lead frame need not always be applied to the entire electronic circuit sealing portion. For example, in the sealing resin of the electronic circuit sealing portion, the upper and lower sides of the wiring substrate that causes structural asymmetry in the sealing portion (portions facing the wiring substrate)
By applying the above-described thickness condition to the sealing resin portion including the above, it is possible to prevent the sealing resin from being distorted or cracked.

Further, the lead frame further has an optical element mounting portion on which the optical element is mounted, and the optical element and the optical element mounting portion are made of a transparent resin that transmits light of the predetermined wavelength. It is preferable that the optical element sealing portion is formed separately from the electronic circuit sealing portion.

When the optical element is mounted on a sub-assembly independent of the lead frame, the number of parts increases,
The manufacturing process becomes complicated. Also, the manufacturing cost increases.
On the other hand, by mounting the optical element on the lead frame as described above, the number of components can be reduced and the manufacturing cost can be reduced.

The difference in the thickness of the sealing resin between the upper and lower sides of the lead frame may be smaller than the thickness of the wiring board. There is a configuration in which an auxiliary member having a shape is provided. At this time, the thickness of the sealing resin below the lead frame is the thickness from the lower surface of the auxiliary member (the surface opposite to the lead frame).

As described above, by disposing the auxiliary member on the other surface side corresponding to the wiring substrate provided on one surface side of the lead frame, the difference in the thickness of the sealing resin can be reduced. It can be reduced to less than the thickness. As the auxiliary member, for example, has substantially the same shape and thickness as the wiring board,
It is preferable to use a member made of a material having the same or similar thermal expansion coefficient and Young's modulus as the wiring board in order to balance the stress.

Further, there is a configuration in which the pad connection portion is formed in a shape offset to the other surface. At this time, the position of the wiring substrate in the sealing portion is shifted to the other surface side (center side of the sealing portion) as compared with the case where the wiring substrate is directly mounted on the lead frame, so that the difference in the thickness of the sealing resin is reduced. Thus, the generation of stress is reduced. Note that the offset shape is specifically a shape obtained by subjecting a lead frame to a bending process so that a pad connection portion is dropped on the other surface side with respect to another portion of the lead frame. There is.

The thickness of the sealing resin on the one surface side of the lead frame from the one surface is the thickness of the sealing resin on the other surface side of the lead frame from the other surface. There are configurations larger than that. In this case, the difference in thickness of the sealing resin can be reduced without disposing the auxiliary member or changing the position of the wiring board.

For electrical connection between the electrode pad and the pad connection portion, a conductive connection material can be used. It is preferable to use a conductive resin for the conductive connection material. Examples of the conductive resin include a resin containing Ag (silver) as a filler. Alternatively, it is preferable to use solder as the conductive connection material. As the solder, for example, Sn
There is a (tin) / Pb (lead) type.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the optical module according to the present invention will be described below in detail with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Also, the dimensional ratios in the drawings do not always match those described.

Here, for convenience in description, the vertical direction in the lead frame and the wiring board is defined. In each of the optical modules described below, a wiring board is mounted on one surface of a lead frame, and when viewed from the lead frame, the direction of this one surface is an upward direction, and the direction of the other surface is a downward direction. . According to this definition,
Regarding the lead frame, the surface on the side on which the wiring board is mounted is referred to as an upper surface, and the opposite surface is referred to as a lower surface. Further, regarding the wiring board, the surface on the side opposite to the lead frame on which the circuit components are mounted is defined as the upper surface, and the surface on the lead frame side is defined as the lower surface.

FIG. 1 shows a first embodiment of the optical module according to the present invention.
It is a perspective view showing the appearance composition of an embodiment. In the optical module according to the present embodiment, the optical element and the like have an optical element sealing portion 1.
6, and an electronic circuit and the like are individually resin-sealed in an electronic circuit sealing portion 18, respectively. The optical element sealing portion 16 and the electronic circuit sealing portion 18 are connected by the internal lead pins 8.

The optical module is of a DIP (dual in-line package) type, and external lead pins 10 protrude from both sides of the electronic circuit sealing portion 18.

Hereinafter, the structure of the optical module according to the embodiment shown in FIG. 1 and the manufacturing process thereof will be described with reference to FIGS.

This optical module uses a metal lead frame 2 having the structure shown in FIG. An optical element mounting portion 4 for mounting the optical element 14 is provided on the lead frame 2.
And two internal lead pins 8 for connecting the optical element mounting section 4 and the electronic circuit, and seventeen fourteen external lead pins 10 located on both sides of a wiring board described later. Further, pad connection portions 8 are provided at the portions of the internal lead pins 8 and the external lead pins 10 on the wiring board side, respectively.
a and 10a are provided.

The lead frame 2 is, for example, 0.25
A metal (for example, copper) thin plate having a thickness of about mm is etched or punched out by a press machine, and the whole is integrally formed. Each part such as the above-mentioned optical element mounting part 4 is integrally supported by the frame part 2a of the lead frame 2 and formed. At a predetermined position of the lead frame 2, a plurality of fitting holes 2b for positioning a resin molding die described later are provided.

The submount member 1 is mounted on the optical element mounting portion 4.
The optical element 14 in the form of a semiconductor chip (bare chip) is fixed via the second element 2. Note that, when the optical module is a receiving module, a parallel-type capacitor (die cap) or the like is used as the submount member 12, and the optical element 14 is used as the optical element 14. A light receiving element such as an InGaAs-PIN photodiode having sensitivity to an optical signal in a 1.3 μm wavelength band is used. When the optical module is a transmitting module, the sub-mount member 12 is a member for heat radiation and is formed of diamond or aluminum nitride material. As the optical element 14, an optical signal in a 1.3 μm wavelength band is transmitted. A light emitting element such as a surface emitting type InGaAsP light emitting diode or a surface emitting type InGaAs laser diode for emitting light is used.

A wiring board 20 is mounted on the upper surface side of the pad connection portions 8a and 10a. This wiring board 20
A circuit component such as the IC 22 is mounted thereon, and a wiring pattern (schematically shown in FIG. 2) is formed thereon to form an electronic circuit for processing an electric signal. In the lower part of the wiring board 20, the electrode pads 20a are provided at positions corresponding to the pad connection portions 8a and 10a, respectively.
(See the cross-sectional view shown in FIG. 4). Also,
The pad connecting portions 8a and 10a and the electrode pad 20a
Is electrically connected using a conductive connecting material.

A board-shaped auxiliary member 30 made of the same material as the wiring board 20 and having substantially the same shape is fixed to the lower surfaces of the pad connection portions 8a and 10a. It is not necessary to use a conductive connecting material for fixing the auxiliary member 30, and a normal adhesive having no conductivity may be used.

As described above, after connecting the optical element 14, the wiring board 20 on which the electronic circuit is formed, and the lead pins 8 and 10 to configure each part of the optical module, the lead frame 2 is fitted into the fitting hole 2b. The resin molding die having a predetermined shape is positioned and mounted. Then, a transparent resin is injected into the mold for an optical signal of a predetermined wavelength (for example, 1.3 μm), and the optical element 14 and the electronic circuit are separated from each other and sealed by a transfer molding process (FIG. 3
See). As a result, the optical element mounting part 4 and the optical element sealing part 16 for integrally sealing the submount member 12 and the optical element 14 mounted thereon, and the pad connection parts 8a and 10a
Then, the electronic circuit sealing portion 18 for integrally sealing the wiring board 20 and the auxiliary member 30 mounted thereon is molded. Note that the optical element sealing portion 16 in which the optical element 14 is sealed may be molded with a transparent resin, and the electronic circuit sealing portion 18 may be molded with an opaque resin.

The optical element sealing section 16 includes a substantially rectangular parallelepiped base 16a for sealing the optical element mounting section 4, the submount member 12, and the optical element 14, and a truncated cone-shaped base integrally formed on the base 16a. A portion 16b and an aspheric lens 16c integrally molded on the top of the base portion 16b.
c and the optical principal surface (light receiving surface or light emitting surface) of the optical element 14
Have the same optical axis.

The base 16b is concentric with the aspheric lens 16c and the optical axis of the optical element 14, and has a tapered side surface having a predetermined inclination angle and a predetermined height so as to become gradually thinner toward the top. It is a truncated cone.

Optical element sealing section 16 and electronic circuit sealing section 18
After molding, an unnecessary part of the lead frame 2 is cut and removed to form an intermediate part shown in FIG. Further, by bending the internal lead pin 8 into a hook shape, the condensing aspheric lens 16 c is connected to the electronic circuit sealing portion 18.
By performing a predetermined bending process to bend the external lead pins 10 toward the opposite side to the opposite side, the DIP (dual in-line package) type optical module shown in FIG. 1 is obtained.

In the optical module of this embodiment, the wiring pattern of the electronic circuit is not formed only by the wire bonding with the lead frame, and the wiring board 20 is mounted on the pad connecting portions 8a and 10a of the lead frame 2. By forming a wiring pattern on the wiring board 20, for example, it is possible to easily realize cross wiring as schematically shown by reference numeral 24 in FIG. Such a cross wiring does not have the problem of impedance mismatch as in the case of a cross wiring formed by performing wire bonding on a wiring pattern formed by a lead frame, and can obtain good circuit characteristics. In addition, since the wiring pitch can be reduced as compared with the wiring pattern using a lead frame, it is possible to increase the efficiency of wiring and to cope with an increase in the scale of an electronic circuit.

The pad connection portion 8 of the lead frame 2
An electrode pad 20a is provided at a position on the lower surface side of the wiring board 20 facing each of the electrodes a and 10a. Then, the pad connecting portions 8a and 10a and the electrode pads 20a are fixed as shown in FIG. 4 by die bonding via a conductive connecting material, and the electronic circuit on the wiring board 20 and the lead frame 2 are electrically connected. Connection.

The pad connecting portions 8a and 10a are connected to the internal lead pins 8 and the external lead pins 10, respectively, so that necessary wiring can be performed without performing wire bonding. At this time, it is not necessary to provide a region for wiring wires between the wiring board 20 and the lead pins 8 and 10 and a wiring pad on the wiring board 20 and the lead frame 2. Therefore, it is possible to increase the size of the wiring board 20 and increase the area of the electronic circuit.

Note that a conductive resin can be used as the conductive connection material. As the conductive resin,
There is a resin containing a conductive filler (conductive filler) made of Ag (silver) or the like. Alternatively, Sn (tin) /
Pb (lead) -based solder or the like can be used.
Further, the support of the wiring board 20 by the lead frame 2 is performed only by fixing to the above-described pad connection portions 8a and 10a, or
The supporting portion of the wiring board 20 may be formed on the substrate.

Here, the wiring board 20 and the sealing resin forming the electronic circuit sealing portion 18 have significantly different coefficients of thermal expansion. In particular, when the sealing resin of the electronic circuit sealing portion 18 is a transparent resin, since the amount of the filler added to the transparent resin is small, for example, the thermal expansion coefficient of a transparent epoxy resin is lower than that of a normal epoxy resin. 6.2-times more than twice as large
It is about 17.2 × 10 ⁻⁵ / ° C. On the other hand, the wiring board 20
The coefficient of thermal expansion of a ceramic substrate such as alumina (Al ₂ O ₃ ), which is often used as, for example, is about 5.5 × 10 ⁻⁶ / ° C., and there is a difference of 10 times or more between them.
Further, even when the sealing resin is a normal epoxy resin, the difference is slightly smaller than that of the transparent epoxy resin, but there is a similar problem.

The resin encapsulation is performed by a transfer molding process using a thermosetting resin, and the resin injected into the mold is cured by heating and holding at a molding temperature for a certain period of time. A part is formed. The heating temperature at this time is set to, for example, about 140 to 160 ° C. in the case of a transparent resin, and the sealing resin of the wiring board 20 and the electronic circuit sealing portion 18 is returned while the sealing resin returns to room temperature after the heat molding. Due to the difference in thermal expansion coefficient described above, a large stress is generated in the sealing resin, which causes distortion and cracks in the electronic circuit sealing portion 18. In particular, such stress
When the structure in the sealing portion 18 becomes asymmetric, such as when the wiring board 20 is mounted on one surface side of the lead frame 2, the generated stress increases, and excessive stress is generated in the sealing portion 18. Will result in a concentrated area.

In order to solve such a problem, in the optical module according to the present invention, the thickness of the sealing resin (hereinafter, referred to as the upper sealing resin) on the upper surface side of the lead frame from the upper surface of the wiring board and the lead frame The electronic circuit sealing portion is formed such that a difference from a thickness of a sealing resin (hereinafter, referred to as a lower sealing resin) on a lower surface side is smaller than a thickness of the wiring board. As a result, it is possible to equalize the stresses generated on the upper and lower sides of the lead frame and the wiring board, to avoid the occurrence of excessive stress and stress concentration, and to prevent the sealing resin from being distorted or cracked.

In the above embodiment, the wiring board 20 mounted on the upper surface side of the lead frame 2 is formed on the lower surface side of the lead frame 2 with the same material and substantially the same shape as the wiring board 20. Is provided. As a result, as shown in FIG. 4 by a cross-sectional view taken along the line II of the optical module of FIG.
0 and the upper sealing resin 18a, and the auxiliary member 3 on the lower side.
0 and the lower sealing resin 18b are arranged in a substantially vertically symmetrical configuration.

At this time, the thickness of the lower sealing resin 18b is
Similarly to the upper sealing resin 18a, the thickness from the lower surface of the auxiliary member 30 is obtained, and the thicknesses of the upper and lower sealing resins 18a and 18b are substantially equal. Therefore, the stress is applied to the sealing resin 18.
Thus, it is possible to prevent the electronic circuit sealing portion 18 from being distorted or cracked due to stress concentration. With the above configuration, an electronic module having a large-scale electronic circuit and maintaining the stability and durability as a product is realized.

Regarding the stress generated in such a configuration, the thickness of the lead frame 2 is set to 0.25 m.
m, the thickness of the wiring board 20 and the thickness of the auxiliary member 30 are 0.38 mm, respectively, and the upper sealing resin 18a and the lower sealing resin 1
When the thickness of each of the lead frames 8b from the lead frame 2 was calculated to be 1 mm, the reduction ratio of the stress was about 26%.
% Was shown to be greatly reduced. Also, the bending stress applied to the substrate itself is similarly reduced.

As a material of the wiring board 20 and the auxiliary member 30, for example, there is a ceramic material such as alumina. In this case, a wiring pattern can be formed by a normal thick film printing technique. Alternatively, there is a resin material such as glass epoxy. In this case, stress generation can be reduced by setting the coefficient of thermal expansion of the substrate to a value close to that of the sealing resin. The material of the auxiliary member 30 does not necessarily need to be the same as that of the wiring board 20, and may have a coefficient of thermal expansion close to that of the wiring board 20,
Any other material having a Young's modulus may be used.

As the sealing resin used for the electronic circuit sealing portion 18, an opaque resin may be used separately from the optical element sealing portion 16. In the case of an opaque resin, the amount of a filler such as silica is larger than that of a transparent resin, and therefore, the coefficient of thermal expansion thereof is lower than that of a wiring substrate such as a ceramic substrate.
, And the occurrence of stress can be further suppressed.

Since circuit components such as the IC 22 are mounted on the upper surface of the wiring board 20, taking the effects into consideration,
The thickness of the upper sealing resin 18a may be set slightly larger than the lower sealing resin 18b.

Further, in the present embodiment, the optical element mounting section 4 on which the optical element 14 is mounted on the lead frame 2 is provided. Thereby, the number of components of the optical module can be reduced, and the manufacturing cost can be reduced. Also,
Since the optical element mounting section 4 and the pad connection sections 8a and 10a functioning as electronic circuit mounting sections are formed separately, the degree of freedom in designing electronic circuits is increased, and the demand for advanced optical communication is met. Complicated and large-scale electronic circuits can be implemented.

The optical element sealing portion 16 and the electronic circuit sealing portion 18 are separately and independently molded, and are electrically and mechanically connected by the internal lead pins 8.
Accordingly, when the present invention is applied to a communication device such as an optical transceiver or the like, the electronic circuit sealing unit 18 due to the enlargement of the electronic circuit is used.
The mounting position of the optical element sealing portion 16 can be adjusted independently without increasing the size of the device and without being affected by the mounting position of the electronic circuit sealing portion 18. Therefore, it is possible to easily adjust the optical axis and the distance between the optical fiber and the axis in the communication device.

Further, since the converging aspherical lens 16c is integrally molded with the optical element sealing portion 16, the number of parts is reduced, and the optical axis and the distance between the axes between the optical element 14 and the aspherical lens 16c are adjusted. Becomes unnecessary. Further, since it is not necessary to adopt a structure in which the condensing lens and the optical element are connected by a connector made of metal or the like, cost reduction can be realized.

Since the optical module has no movable parts, the optical module has an excellent structure such as high mechanical strength and optical precision always maintained in an optimum state.

In this embodiment, all the circuit components and wiring patterns are formed on the wiring board 20 in the present embodiment. A wiring pattern may be used. Also in this case, by providing pad connection portions in the wiring pattern of the lead frame 2 and installing electrode pads on the wiring board 20 corresponding to the pad connection portions, electrical connection can be performed without performing wire bonding. Can be. At this time, the circuit component may be mounted on either the wiring pattern on the wiring board 20 or the wiring pattern on the lead frame 2, or may be mounted on the wiring board 20 and the lead frame 2, respectively. Further, a plurality of substrates can be used.

The optical module according to the present invention is not limited to the above embodiment, and various modifications are possible.

FIG. 5 is a sectional view showing a second embodiment of the optical module. This figure corresponds to the cross-sectional view taken along the line II shown in FIG. 4 for the first embodiment. In the present embodiment, the auxiliary member 30 is not used to reduce the difference in the thickness of the sealing resin, and the pad connection portions 8a and 10a are formed in a shape offset to the lower surface side as viewed from the lead frame 2. , Upper and lower sealing resins 18a, 18
The difference in thickness of b is reduced.

More specifically, the pad connecting portions 8a and 10a, which are the ends of the lead pins 8 and 10 on the wiring board 20 side, are bent and dropped from the lead frame 2 downward. I have. At this time, since the position of the wiring board 20 that has been displaced upward in the electronic circuit sealing portion 18 moves to the center side of the sealing portion 18, the difference in thickness between the upper and lower sealing resins 18a and 18b is increased. Is reduced, and the occurrence of stress is suppressed.

For the optical module having the structure shown in FIG. 5, when the stress was calculated under the same conditions as the thickness shown in FIG. 4, the reduction ratio of the stress was also large, about 29%. Met.

FIG. 6 is a sectional view showing a third embodiment of the optical module. In the present embodiment, the wiring board 2
0 is directly mounted on the upper surface side of the pad connection portions 8a and 10a of the lead frame 2,
Of the upper sealing resin 18a from the upper surface of the
Is larger than the thickness of the lower sealing resin 18b from the lower surface of the lead frame 2. This compensates for the thickness of the sealing resin with respect to the upper sealing resin 18a, reduces the difference in thickness between the upper and lower sealing resins 18a, 18b, and suppresses stress generation.

The thickness condition for reducing the difference between the thickness of the sealing resin 18a and the thickness of the sealing resin 18b with respect to the upper sealing resin 18a and the lower sealing resin 18b is not necessarily limited to the sealing for forming the electronic circuit sealing portion 18. It is not necessary to apply to the entire resin. For example, as shown in the following modified examples (FIGS. 7 and 8), of the sealing resin of the electronic circuit sealing portion 18, which faces the wiring board 20, a structure asymmetry is generated in the sealing portion 18. Stress generation can also be suppressed by a configuration in which the above-described thickness condition is applied to the resin portion including the portion.

FIG. 7 is a sectional view showing a fourth embodiment which is a modification of the third embodiment shown in FIG. In the present embodiment, instead of increasing the overall thickness of the upper sealing resin 18a as shown in FIG. 6, a convex portion having an increased thickness is provided on the upper sealing resin 18a including the upper portion of the wiring board 20. A portion 18c is formed.

FIG. 8 is a sectional view showing a fifth embodiment which is another modification of the third embodiment shown in FIG. In the present embodiment, a concave portion 18d having a reduced thickness is formed in a portion of the lower sealing resin 18b including a lower portion of the wiring board 20. According to these fourth and fifth embodiments, as in the third embodiment, the upper and lower sealing resins 18 are formed.
The difference in thickness between a and 18b is reduced, and the occurrence of stress is suppressed.

In addition to the first to fifth embodiments,
Various configurations can reduce the difference in thickness between the upper and lower sealing resins. In each of the embodiments described above, the DIP type optical module is described. However, the optical module according to the present invention can be similarly applied to a SIP (single in-line package) type optical module.

[0064]

The optical module according to the present invention has the following effects as described in detail above. That is,
An electronic circuit for processing an electric signal is formed on a wiring board capable of cross wiring, and the electrode pads of the wiring board and the pad connection portions of the lead frame are directly electrically connected without using wire bonding. Connecting. As a result, the board size is increased and the wiring pitch is reduced,
The electronic circuit can have a large area and a large scale.

In this case, stress is generated due to a difference in the coefficient of thermal expansion between the wiring board and the sealing resin of the electronic circuit sealing portion, and the sealing resin is distorted or cracked. On the other hand, the difference between the thickness of the sealing resin on the upper surface of the lead frame from the upper surface of the wiring board and the thickness of the sealing resin on the lower surface of the lead frame is smaller than the thickness of the wiring substrate. Constitute.
At this time, an optical module having a configuration in which stress generation is reduced and distortion and cracking of the sealing resin are avoided, and thus the electronic circuit is enlarged and the stability and durability of the product are maintained. Is achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an external configuration of an optical module according to a first embodiment.

FIG. 2 is a perspective view showing a configuration of a lead frame and a wiring board used in the optical module shown in FIG.

FIG. 3 is a perspective view showing a configuration of an intermediate component of the optical module shown in FIG.

FIG. 4 is a sectional view of the optical module shown in FIG.

FIG. 5 is a cross-sectional view illustrating a second embodiment of the optical module.

FIG. 6 is a cross-sectional view illustrating a third embodiment of the optical module.

FIG. 7 is a cross-sectional view illustrating a fourth embodiment of the optical module.

FIG. 8 is a cross-sectional view showing a fifth embodiment of the optical module.

[Explanation of symbols]

Reference numeral 2: lead frame, 2a: frame portion, 2b: fitting hole, 4: optical element mounting portion, 8: internal lead pin, 8a: pad connection portion, 10: external lead pin, 10a: pad connection portion, 12: submount member , 14 ... optical element, 16 ...
Optical element sealing portion, 16a: base portion, 16b: base portion, 16c ...
Aspherical lens, 18: electronic circuit sealing portion, 18a: upper sealing resin, 18b: lower sealing resin, 18c: convex portion, 18d
... recess, 20 ... wiring board, 20a ... electrode pad, 22 ...
IC, 24: cross wiring, 30: auxiliary member.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasuki Mikamura 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa F-term in Yokohama Works, Sumitomo Electric Industries, Ltd. 5F041 AA40 AA47 DA20 DA43 DA55 5F088 BA11 BA15 JA02 JA03 JA06 KA10

Claims (7)

[Claims] An optical element for converting one of the signals into an optical signal having a predetermined wavelength and an electric signal corresponding thereto, and an electronic circuit for processing the electric signal;
A lead frame having lead pins respectively connected to the electronic circuit, wherein a wiring board on which at least a part of the electronic circuit is formed is fixed to one surface side of the lead frame, The electronic circuit on the wiring board, and the lead frame are electrically connected to each other by directly connecting the electrode pads provided on the wiring board, and the pad connection portion provided on the lead frame, The circuit board and the pad connection portion of the lead frame are sealed with a resin to form an electronic circuit sealing portion. The electronic circuit sealing portion seals the one surface side of the lead frame. The thickness of the sealing resin from the surface of the wiring board opposite to the lead frame, and the thickness of the sealing resin on the other surface of the lead frame. An optical module, wherein a difference from the optical module is smaller than a thickness of the wiring board. 2. The lead frame further includes an optical element mounting part on which the optical element is mounted, wherein the optical element and the optical element mounting part are formed of a transparent resin that transmits light of the predetermined wavelength. 2. The optical module according to claim 1, wherein the optical element sealing portion is formed separately from the electronic circuit sealing portion. 3. The optical module according to claim 1, wherein a substrate-shaped auxiliary member is provided on the other surface side of the lead frame in the electronic circuit sealing portion. 4. The optical module according to claim 1, wherein the pad connection portion is formed in a shape offset to the other surface. 5. The thickness of the sealing resin on the one surface side of the lead frame from the one surface is the thickness of the sealing resin on the other surface side of the lead frame from the other surface. The optical module according to claim 1, wherein the optical module is larger than the optical module. 6. The optical module according to claim 1, wherein the electrode pad and the pad connection are electrically connected by a conductive resin. 7. The optical module according to claim 1, wherein said electrode pad and said pad connection portion are electrically connected by solder.