JP4780933B2 - Optical semiconductor device - Google Patents

Description

  The present invention relates to an optical semiconductor device including a light receiving element or a semiconductor element having a light receiving portion.

  An optical semiconductor device including an optical semiconductor element such as a photodiode, a line sensor, or an image sensor has, for example, a configuration in which the optical semiconductor element is mounted inside a concave insulating base. The optical semiconductor element is bonded to the insulating substrate via a bonding material. Then, for example, a flat cover is joined to the upper surface of the insulating base via a joining material.

As a bonding material for bonding the optical semiconductor element and the insulating base, for example, an epoxy resin or a polyimide resin mixed with a metal such as silver or aluminum or a filler of an inorganic material such as silica is used. Here, as a conventional method of applying the bonding material, for example, when the optical semiconductor element is rectangular like a line sensor, the bonding material is linearly formed at a portion corresponding to the optical semiconductor element of the insulating base. A method of applying, or a method of applying a bonding material in a dotted manner to a portion of the insulating substrate corresponding to the optical semiconductor element has been used. Then, the optical semiconductor element is aligned and mounted on the bonding material, and the bonding material is spread over the entire bonding surface between the optical semiconductor element and the insulating base so as to press the optical semiconductor element against the bonding material. The optical semiconductor element and the insulating base were joined. Note that a part of the bonding material protruded from a region corresponding to the optical semiconductor element of the insulating base, and the protruding part was an inclined surface or a gently curved meniscus shape.
JP 2001-298032 A JP-A-5-291313

  However, in the conventional optical semiconductor device, particularly when the optical semiconductor element is rectangular like a line sensor, the bonding material for bonding the optical semiconductor element and the insulating base is the short side of the optical semiconductor element. As a result, the optical semiconductor element may be displaced. As described above, the cause of the phenomenon in which the bonding material is peeled off from the short side of the optical semiconductor element was examined, and the following two causes were considered. The first cause is that stress such as thermal stress due to the difference in thermal expansion between the optical semiconductor element and the insulating base is concentrated on the short side of the optical semiconductor element. The second cause is that the portion of the bonding material that protrudes from the region of the insulating base corresponding to the optical semiconductor element is an inclined surface or a gently curved meniscus, and is concentrated on the short side of the optical semiconductor element. It was difficult to absorb or disperse the stress.

  For the purpose of improving the bonding strength on the short side of the optical semiconductor element, a method of thickly applying the bonding material on the short side of the optical semiconductor element in the region corresponding to the optical semiconductor element of the insulating base is also conceivable. However, in this method, there is a possibility that the optical semiconductor element is mounted with an inclination. In particular, in recent years, optical semiconductor elements such as photodiodes, line sensors, and image sensors have been formed very finely in response to demands for finer images and higher accuracy of light detection. It has come to have a big influence.

  Accordingly, the present invention has been completed in view of the above problems, and its object is to improve the bonding strength on the short side of an optical semiconductor element when a rectangular optical semiconductor element is mounted. Accordingly, it is an object of the present invention to provide a highly reliable optical semiconductor device that meets the recent demands for finer images and higher accuracy of light detection.

An optical semiconductor device according to the present invention includes an insulating base having an optical semiconductor mounting portion formed on an upper surface, a wiring conductor formed from the upper surface to a side surface or a lower surface of the insulating base, and a bonding material interposed between the mounting portions. A rectangular optical semiconductor element that is mounted and bonded, and an electrode is electrically connected to the wiring conductor, and a space for accommodating the optical semiconductor element is formed on the upper surface of the insulating base. And a lid made of at least a part made of a translucent member, and the bonding material covers the side surface on the short side of the optical semiconductor element and covers the side surface. The surface of the part which is carrying out is formed in the uneven | corrugated shape which wavy in the waveform .

  In the optical semiconductor device of the present invention, preferably, the bonding material has a longitudinal cross-sectional shape of the surface of the portion covering the side surface on the short side of the optical semiconductor element, outward from the side surface. The concave portion and the convex portion have a shape formed continuously.

  The optical semiconductor device of the present invention is preferably characterized in that the bonding material covers from the lower end to the center in the height direction of the side surface on the short side of the optical semiconductor element. Is.

  In the optical semiconductor device of the present invention, preferably, the bonding material has an outer edge portion thinner than a portion in contact with the side surface of the optical semiconductor element.

The optical semiconductor device according to the present invention is preferably characterized in that the bonding material gradually becomes thinner at the outer edge portion as the outer edge is approached.

  The optical semiconductor device of the present invention is preferably characterized in that the bonding material covers a side surface on the long side of the optical semiconductor element.

According to the optical semiconductor device of the present invention, the bonding material covers the side surface on the short side of the optical semiconductor element, and the surface of the portion covering the side surface is formed in an uneven shape wavy. The bonding strength on the short side of the optical semiconductor element can be improved, and stress that tends to concentrate on the bonding material on the short side of the optical semiconductor element can be effectively absorbed and dispersed. That is, since the bonding material covers the side surface on the short side of the optical semiconductor element, the bonding strength can be improved, and the surface of the portion covering the side surface is formed in an uneven shape wavy. As a result, stress can be absorbed and dispersed along the uneven surface. As a result, peeling of the rectangular optical semiconductor element from the short side can be suppressed, and an optical semiconductor device with high reliability can be provided.

  Further, according to the optical semiconductor device of the present invention, preferably, the longitudinal cross-sectional shape of the surface of the bonding material covering the side surface on the short side of the optical semiconductor element has a concave portion and an outward surface from the side surface. Since the convex portions are continuously formed, the stress applied to the bonding material on the short side of the optical semiconductor element can be effectively dispersed by the concave portions and the convex portions. That is, in the concave portion, the stress is dispersed toward the upper side of the inclined surface, and in the convex portion located further outside, the stress is concentrated toward the upper side of the inclined surface. Therefore, as a whole of the bonding material covering the side surfaces, it is possible to suppress the stress from being concentrated at a place where stress is dispersed and peeling is likely to occur. Further, since the convex portion where stress is concentrated is formed with the concave portion interposed between the optical semiconductor element and the optical semiconductor element, peeling at the joint surface with the optical semiconductor element can be suppressed.

  Further, according to the optical semiconductor device of the present invention, preferably, the bonding material covers from the lower end to the center in the height direction of the side surface on the short side of the optical semiconductor element. The bonding strength on the short side can be further improved.

  Further, according to the optical semiconductor device of the present invention, preferably, the outer edge portion is thinner than the portion of the bonding material that contacts the side surface of the optical semiconductor element, so that stress concentration on the outer edge portion can be further suppressed. It becomes possible to suppress peeling from the outer edge of the bonding material.

Further, according to the optical semiconductor device of the present invention, preferably, the bonding material, the thickness of the outer edges, by which is gradually thinner along with towards the outer edge, stress is concentrated on the outer edge portion of the bonding material This can be further suppressed, and peeling from the outer edge can be suppressed.

  Moreover, according to the optical semiconductor device of the present invention, preferably, the bonding material covers the side surface on the long side of the optical semiconductor element, so that the bonding material is also formed on the long side of the optical semiconductor element. Stress generated inside can be dispersed, and peeling from the outer edge of the bonding material can be further suppressed.

  The optical semiconductor device of the present invention will be described below in detail with reference to the drawings. 1A is a cross-sectional view showing an example of an embodiment of an optical semiconductor device of the present invention, and FIG. 1B is indicated by X in the optical semiconductor device shown in FIG. It is an enlarged view of a location. The optical semiconductor device of the present invention includes an optical semiconductor element 101, an insulating base 102 on which the optical semiconductor element is mounted, a bonding material 103 that joins the optical semiconductor element 101 and the insulating base 102, and a light formed on the insulating base 102. A wiring conductor 104 electrically connected to the semiconductor element 101 and a lid 105 attached to the insulating base 102 are provided.

  The optical semiconductor element 101 has a rectangular appearance in plan view. The optical semiconductor element 101 is, for example, a light receiving element such as a PD (Photodiode Device), a line sensor, an image sensor, a CCD (Charge Coupled Device), or a semiconductor element having a light receiving portion such as an EPROM (Erasable and Programmable ROM). is there. The optical semiconductor element 101 has a light receiving portion on the upper surface. In addition, the optical semiconductor element 101 is provided with electrodes 106 for power supply and signal around the light receiving portion on the upper surface.

  The insulating base 102 has a mounting portion on which the optical semiconductor element 101 is mounted on the upper surface. In the example shown in FIG. 1, the insulating base 102 has a concave shape having a mounting portion inside. The insulating base 102 is made of, for example, ceramics such as alumina sintered body (alumina ceramics), aluminum nitride ceramics, silicon carbide ceramics, silicon nitride ceramics, glass ceramics, or resin. Here, a manufacturing method of the insulating substrate 102 in the case where the insulating substrate 102 is made of an alumina sintered body and the bottom plate portion and the side wall portion are formed by integral firing will be described. First, raw material powders such as alumina and silica are formed into a sheet shape together with an organic solvent and an upper surface resin binder to produce a plurality of ceramic green sheets. A part of the ceramic green sheets is punched to produce a frame-shaped ceramic green sheet. Thereafter, the ceramic green sheets are laminated so that the frame-shaped ceramic green sheet is positioned in the upper layer, and fired at a temperature of about 1300 ° C. to 1600 ° C. according to the composition of the raw material powder. Thus, the insulating base 102 is formed. The insulating substrate 102 may be formed by bonding a frame-like alumina sintered body to the outer peripheral portion of the upper surface of the plate-like alumina sintered body.

  The bonding material 103 is used for bonding the optical semiconductor element 101 to the upper surface of the insulating base 102. The bonding material 103 is provided so as to cover the side surface on the short side of the optical semiconductor element 101. The bonding material 103 extends from between the bottom surface of the optical semiconductor element 101 and the insulating base 102 onto the insulating base 102 on the side surface side of the optical semiconductor element 101. The surface of the portion (side surface covering portion 103a) that covers the side surface on the short side of the optical semiconductor element 101 of the bonding material 103 is formed in an uneven shape. When the side surface covering portion 103a is viewed in a longitudinal section, the unevenness is wavy. That is, in the bonding material 103, the longitudinal cross-sectional shape of the surface of the side surface covering portion 103a is preferably a shape in which concave portions and convex portions are continuously formed from the side surface toward the outside.

  Here, a method of forming the bonding material 103 will be described. First, when the optical semiconductor element 101 is mounted on the upper surface of the insulating base 102, the upper surface of the insulating base 102 is elongated in accordance with the shape of the optical semiconductor element 101 and longer than the optical semiconductor element 101 in the long side direction. The bonding material 103 is applied to the substrate. Then, after mounting the optical semiconductor element 101 on the applied bonding material 103, an external force is applied to the bonding material 103 from the outer side of the short side of the optical semiconductor element 101 toward the optical semiconductor element 101, The surface of 103 is bent into a waveform. As another method for forming the bonding material 103, there is a method in which a corrugated jig is pressed against the surface of the bonding material 103 to shape the surface of the bonding material 103 into a wave shape.

  In addition, as shown in FIG.1 (b), the thickness of the joining material 103 becomes thin in the longitudinal cross-section of the side surface covering part 103a from the short side surface to the outer edge (first part). Then, the thickness increases as it goes to the outer edge (second part), and further the thickness decreases as it goes to the outer edge (third part). preferable. By taking such a shape, the stress can be effectively dispersed. That is, the stress can be dispersed upward by the second portion whose thickness increases toward the outer edge.

  Further, when the optical semiconductor element 101 is bonded to the insulating base 102, the part corresponding to the outer peripheral portion of the optical semiconductor element 101 is thicker than the part corresponding to the short side of the optical semiconductor element 101 in the insulating base 102. Alternatively, the bonding material 103 may be applied to the upper surface of the insulating substrate 102. In this case, when the optical semiconductor element 101 is mounted on the bonding material 103, the second portion can be formed by the surface tension of the bonding material 103, and productivity can be improved. That is, when the optical semiconductor element 101 is mounted on the bonding material 103, the bonding material 103 moves downward due to the weight applied by the optical semiconductor element 101. Furthermore, since the bonding material 103 on the outer side is provided thick, the second portion can be easily formed.

  As described above, in the optical semiconductor device of the present invention, since the side surface on the short side of the optical semiconductor element 101 is covered with the bonding material 103, the bonding between the optical semiconductor element 101 and the insulating base 102 is made stronger. It can be. In the optical semiconductor device of the present invention, the surface of the portion (side surface covering portion 103a) that covers the short side surface of the optical semiconductor element 101 of the bonding material 103 is formed in a concavo-convex shape (the surface undulates). Therefore, the stress generated in the bonding material 103 can be dispersed along the surface irregularities (corrugated surface). As described above, according to the optical semiconductor device of the present invention, in a rectangular optical semiconductor element 101 such as a line sensor, it is possible to suppress peeling or the like that occurs due to stress concentration on the short side. Then, external light can be normally received by the optical semiconductor element 101, and normal electrical signals can be transmitted to other external devices and elements.

  Moreover, it is preferable that the bonding material 103 covers the side surface on the short side of the optical semiconductor element 101 from the lower end to the center in the height direction. With such a configuration, the optical semiconductor element 101 can be more reliably bonded. Moreover, it is preferable that the thickness of the outer edge portion of the bonding material 103 is thinner than the thickness of the portion in contact with the side surface of the optical semiconductor element 101. With such a configuration, it is possible to suppress the stress generated in the bonding material 103 from being concentrated on the outer edge portion of the bonding material 103, and to prevent the bonding material 103 from being peeled off from the outer edge portion due to internal stress. Furthermore, it is preferable that the bonding material 103 has a thickness that decreases toward the outer edge at the outer edge. With such a configuration, it is possible to further suppress the concentration of stress on the outer edge portion of the bonding material 103, and to further prevent peeling from the outer edge. Further, the bonding material 103 may be formed so as to cover the side surface on the long side of the optical semiconductor element 101. And the surface of the coating | coated part of the side surface of a long side may be formed in uneven | corrugated shape. That is, the surface of the covering portion on the side surface on the long side may be formed into a corrugated shape. With this configuration, the bonding between the semiconductor element 101 and the insulating base 102 can be made stronger.

  The wiring conductor 104 is formed from the upper surface to the lower surface of the insulating base 102, and is electrically connected to the electrode of the optical semiconductor element 101 via the bonding wire 107. The wiring conductor 104 may be formed from the upper surface to the side surface of the insulating base 102. The wiring conductor 104 is made of a metal material such as tungsten, molybdenum, manganese, copper, silver, palladium, platinum, or gold, and is provided on a predetermined portion of the insulating base 102 in the form of a metallized layer, a plating layer, a vapor deposition layer, a metal foil layer, or the like. It is formed. If the wiring conductor 104 is made of, for example, a tungsten metallized layer, a metal paste obtained by kneading tungsten powder together with an organic solvent and a resin binder is printed on a ceramic green sheet serving as the insulating base 102 by a screen printing method or the like. It is formed by. Note that the lead conductors made of Fe—Ni—Co alloy, copper, copper alloy, or the like may be attached to the portion of the wiring conductor 104 led to the lower surface or side surface of the insulating base 102 by brazing or the like. Further, a plating layer such as gold plating or tin plating may be deposited on the exposed surface of the wiring conductor 104.

  The bonding wire 107 preferably has a length of 0.3 mm to 3.0 mm. If the length of the bonding wire 107 is less than 0.3 mm, it is difficult to form a sufficient loop because the bonding wire 107 is too short, and the electrode 106 of the optical semiconductor element 101 and the wiring conductor 104 can be reliably connected. It becomes difficult. Also, if the length of the bonding wire 107 exceeds 3.0 mm, the bonding wire 107 tends to be too long and the loop tends to become unnecessarily high, which may cause unnecessary inductance and deteriorate the transmission characteristics of the high frequency signal. is there.

  The lid 105 is attached to the insulating base 102 via a bonding material 108 so as to form a space in which the optical semiconductor element 101 is accommodated. The lid 105 is entirely or partially made of a light transmissive member. In the optical semiconductor device shown in FIG. 1, the lid 105 is formed by forming a translucent material such as glass, quartz, sapphire, or transparent resin into a plate shape. Although not shown, when the insulating base 102 has a flat plate shape, a concave lid may be used. In this case, a part of the concave lid is made of a translucent member. Further, an optical film for blocking ultraviolet rays may be formed on at least one of the upper surface and the lower surface of the lid 105.

  The bonding material 108 is made of, for example, a resin adhesive such as an acrylic resin, an epoxy resin, a phenol resin, or a cresol resin. The adhesive 7 may be mixed with dark pigments or dyes such as black, brown, dark brown, dark green, and dark blue for the purpose of blocking extraneous external light. Further, the bonding material 108 may be made of an inorganic material such as glass, or a filler powder made of an inorganic material added to a resin adhesive.

  Further, when the bonding material 108 is made of a transparent resin adhesive, it is preferable that the refractive index of the bonding material 108 be equal to the refractive index of the transparent lid 105. In this case, reflection or scattering of light at the interface between the bonding material 108 and the lid 105 can be suppressed, and excess reflected light or scattered light can be prevented from entering the optical semiconductor element 101. Become. Further, when the bonding material 108 is made of a transparent resin adhesive, it is preferable that the volume of bubbles contained therein is 30% by volume or less. When the volume of the bubbles exceeds 30% by volume, the bonding force of the bonding material 108 decreases, and extra reflected light or scattered light may enter the optical semiconductor element 101 due to the bubbles. In order to reduce the ratio of bubbles contained in the bonding material 108, there are a method of handling the bonding material 108 in a decompression chamber or a vacuum apparatus, a method of vacuum degassing bubbles previously included in the bonding material 108, and the like.

  Further, a light-shielding resin film may be attached to the outer peripheral portion of the lid 105. With such a configuration, it is possible to prevent extraneous external light from entering the semiconductor element 101.

(A) is sectional drawing which shows an example of embodiment of the optical semiconductor device of this invention, (b) is an enlarged view of X location of the optical semiconductor device shown to (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Optical semiconductor element 102 ... Insulating base | substrate 103 ... Bonding material 104 ... Wiring conductor 105 ... Cover 106 ... Electrode 107 ... Bonding wire 108 ... Bonding material

Claims (6)

An insulating base having an optical semiconductor element mounting portion formed on the upper surface, a wiring conductor formed from the upper surface to the side surface or the lower surface of the insulating base, and being mounted by being bonded to the mounting portion via a bonding material A rectangular optical semiconductor element having an electrode electrically connected to the wiring conductor, and at least a part attached to form a space for accommodating the optical semiconductor element on the upper surface of the insulating base Includes a lid made of a translucent member, and the bonding material covers the side surface on the short side of the optical semiconductor element, and the surface of the portion covering the side surface is corrugated. An optical semiconductor device, wherein the optical semiconductor device is formed in an uneven shape.   In the bonding material, the longitudinal cross-sectional shape of the surface of the portion covering the side surface on the short side of the optical semiconductor element is formed such that a concave portion and a convex portion are continuously formed from the side surface toward the outside. 2. The optical semiconductor device according to claim 1, wherein the optical semiconductor device has a shape.   3. The optical semiconductor device according to claim 1, wherein the bonding material covers from the lower end to the center in the height direction of the side surface on the short side of the optical semiconductor element.   4. The optical semiconductor device according to claim 1, wherein an outer edge portion of the bonding material is thinner than a portion in contact with the side surface of the optical semiconductor element. The optical semiconductor device according to claim 4, wherein the bonding material has a thickness that gradually decreases with increasing thickness toward the outer edge.   The optical semiconductor device according to claim 1, wherein the bonding material covers a side surface on a long side of the optical semiconductor element.

Images