Image pickup module

An image pickup module includes: an image pickup chip including a main surface on which a light-receiving portion of an image pickup device and a plurality of electrodes connected to the light-receiving portion are formed; and a wiring board including flying leads bonded to the respective plurality of electrodes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup module including: an image pickup chip on which a light-receiving portion of a solid-state image pickup device is formed; and a wiring board.

2. Description of the Related Art

Japanese Patent Application Laid-Open Publication No. 2011-1192808 discloses an image pickup module110in which a prism150is disposed at a light-receiving portion121of a solid-state image pickup device, through a transparent member140. In addition, a bump123, which is connected with the light-receiving portion121through an internal wiring124and a connecting electrode122, is bonded to a bonding electrode131of a wiring board130, thereby reducing the size of the image pickup module.

The end surface130L of the wiring board130and the end surface120L of the image pickup chip120overlap each other. Therefore, at the time of bonding, the positions of the bump123and the bonding electrode131which are located on the rear surface of the wiring board130cannot be directly and visually checked.

Note that the above-described publication recites that a wiring board having a flying lead is positively excluded.

SUMMARY OF THE INVENTION

An image pickup module according to an embodiment of the present invention includes: an image pickup chip including a main surface on which a light-receiving portion of an image pickup device and a plurality of electrodes connected to the light-receiving portion are formed; and a wiring board including flying leads bonded to the respective plurality of electrodes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

As shown inFIGS. 2 and 3, an image pickup module10according to the present embodiment includes an image pickup chip20to which a wiring board30and a prism50are bonded. On a main surface20SA of the image pickup20, a light-receiving portion21of a solid-state image pickup device and a plurality of electrodes22connected to the light-receiving portion21through an internal wiring24are formed. The plurality of electrodes22are bonded respectively to flying leads31of the wiring board30through bumps23. Note that, in the image pickup module10, an end surface20L on a rear end side of the image pickup20and an end surface30L on a distal end side of the wiring board30overlap each other.

Each of the flying leads31is made of a conducting body protruded from the end surface30L of the wiring board30by a predetermined amount, and formed by removing an insulation layer covering the internal wiring of the wiring board30. That is, the end surface30L is the end surface of the insulation layer of the wiring board30. The flying leads31are sealed by a sealing resin35together with the end surface30L of the wiring board30.

The prism50is an optical component that changes a direction of incident light such that incident light L entered from the direction parallel to the main surface20SA of the image pickup chip20is incident on the light-receiving portion21. The prism50is bonded to the upper surface of the light-receiving portion21through a transparent adhesion layer40.

Next, a manufacturing method of the image pickup module10will be described.

An image pickup substrate is manufactured by a plurality of light-receiving portions21and a plurality of electrodes22connected to the respective light-receiving portions21being formed on the main surface20SA of a silicon wafer by a known semiconductor process. Then, the image pickup substrate is cut, and thereby a plurality of image pickup chips20are created.

A material for the adhesion layer40that bonds the prism50to the light-receiving portions21of the image pickup chip is selected from a transparent resin, for example, an UV curable resin or a thermo-curing resin such as a silicone resin, an epoxy resin, an acrylic resin, or the like.

Electric bonding between the electrodes22of the image pickup chip20and the flying leads31of the wiring board30is performed by applying energy to the distal end portions of the flying leads31directly from upside of the distal end portions of the flying leads while performing positioning between the electrodes and the flying leads.

The image pickup module10is extremely small so as to be able to be disposed at the distal end portion of the endoscope having a thin diameter. The prism50has an incident surface of 1.0 mm square, and the wiring board30has a length of 1.5 mm in the major axis direction, a length of 1.0 mm in the minor axis direction, and the thickness of 0.2 mm, for example. In addition, the electrodes22each having 50 μm square are arranged in a line so as to have a space of 50 μm between the electrodes, and each of the flying leads31has a width of 50 μm, a thickness of 20 μm, and a length of 200 μm, for example.

Therefore, accurate positioning is essential. In the image pickup module10, the width of each of the flying leads31is substantially equal to or smaller than the size (width) of each of the electrodes22. Accordingly, the bonding positions on the main surface20SA can be confirmed while visually checking the bonding positions from upside of the main surface. That is, the bonding positions can be adjusted while viewing the video image obtained by a digital microscope, for example. Then, energy is applied in the state where the positions of the electrodes22are aligned with the positions of the flying leads31, which enables the electrodes and the flying leads to be surely bonded at predetermined positions.

Therefore, the image pickup module10has a high reliability for the bonding portions and a high yield percentage. In addition, since the bonding is performed by applying energy, the reliability of the bonding portions is higher than the bonding using a conductive resin and the like.

For example, in the case of thermal bonding, when a heating tool is heated to a temperature between 100 to 400 degrees Celsius, the heating tool is pressed against the distal end portions of the flying leads31. The flying leads31may be bonded one by one or a plurality of flying leads31may be bonded simultaneously, depending on the specs of the heating tool. In any case, heat is locally applied only to the distal end portions of the flying leads31, which prevents damage from occurring at the light-receiving portion21as a semiconductor circuit.

In addition, when the bonding surfaces of the flying lead31and the surfaces of the bumps23are made of gold (Au), ultrasonic bonding is also possible. In the ultrasound bonding, heating is hardly required, which prevents damage from occurring specifically at the light-receiving portion21.

After the flying leads31are bonded, a sealing resin35as a sealing portion that covers and seals the flying leads31is disposed. The sealing resin35contributes to the protection of the flying leads31made of metal conducting body and improvement of the connection strength between the image pickup chip20and the wiring board30.

A thermo-curing epoxy resin, for example, is used as the sealing resin35. That is, a liquid resin in the uncured state is disposed so as to cover the flying leads31using a dispensing method, for example, and thereafter thermo-curing treatment is performed at the temperature between 80 to 120 degrees Celsius, for example. The curing temperature is set to a temperature equal to or higher than the temperature required for the resin to be sufficiently cured and lower than the temperature at which damage occurs at the light-receiving portion21.

Since the thermo-curing temperature of the sealing resin35is low, there is no possibility that damage occurs at the light-receiving portion21. Note that the curing method may be selected from any one of the thermo-curing method, the UV curing method, the combination of the UV curing method and the thermo-curing method, the combination of the UV curing method and a moisture curing method, a room temperature curing method, or the like, depending on the type of resin, as long as a desired property is satisfied.

The image pickup module10for endoscope is inserted into a disposing hole of a distal end member of the endoscope and fixed with adhesive. The space between the image pickup module10and the disposing hole is sealed with a sealing resin. The adhesive and the sealing resin preferably include a filler with high heat conductivity. For example, silica, metal powder, alumina, aluminum nitride or the like is used as the filler, and silicone resin, acrylic resin, or the like is used as the sealing resin.

The endoscope1, which includes the image pickup module10having high reliability for the bonding portion between the image pickup chip20and the wiring board30, has high reliability.

Second Embodiment

Next, description will be made on an image pickup module10A according to the second embodiment. The image pickup module10A is similar to the image pickup module10. Therefore, the same constituent elements are attached with the same reference numerals and description thereof will be omitted.

As shown inFIG. 4, an electronic component32is surface-mounted on a wiring board30of the image pickup module10A. A sealing resin35is formed by performing curing treatment on a liquid resin disposed between the prism50and the electronic component32.

The electronic component32is disposed near the light-receiving portion21for primary treatment of an image pickup signal from the light-receiving portion21, for example.

When the viscosity of the liquid resin is high, a hollow portion is likely to be created on the lower surface sides of the flying leads31. On the other hand, when the viscosity of the liquid resin is low, the liquid resin is likely to flow out, and the thickness of the sealing resin35on the upper portions of the flying leads is likely to be reduced.

Therefore, when the shape of the electronic component32in a planar view is substantially rectangular, it is preferable to arrange the electronic component32such that the major axis direction of the electronic component32is parallel to the end surface30L of the wiring board30. The side surface of the electronic component32becomes a wall, thereby preventing the liquid resin from flowing out. That is, the liquid resin remains between the prism50and the electronic component32. As a result, it is easy to form the sealing resin35with sufficient thickness also on the upper portions of the flying leads31. That is, arranging the electronic component32at a predetermined position enables an additional function other than signal processing to be applied to the electronic component32.

A chip type capacitor, for example, can be preferably used as the electronic component32. It is preferable for the electronic component32to have a width (major axis dimension) substantially equal to the width of the sealing resin35(arrangement width of the plurality of electrodes22). When an electronic component having a small width is used, a plurality of electronic components are continuously disposed, to thereby be capable of preventing the liquid resin from flowing out.

The image pickup module10A has the same effects as those of the image pickup module10. In addition, the image pickup module10A is capable of surely sealing the flying leads31with the sealing resin35, which provides high reliability for the bonding portions.

Third Embodiment

Next, description will be made on an image pickup module10B according to the third embodiment. The image pickup module10B is similar to the image pickup module10and the like. Therefore, the same constituent elements are attached with the same reference numerals and description thereof will be omitted.

As shown inFIG. 5, the image pickup module10B is configured such that an end surface20L of the image pickup chip20and an end surface30L of the wiring board30do not overlap each other. With the image pickup module10B, when a liquid resin is applied, the liquid resin is spread also to the rear surface sides of the flying leads31from the gap between the end surface20L and the end surface30L which do not overlap each other. Such a configuration is not likely to create a hollow portion on the rear surface sides of the flying leads31.

The image pickup module1OB has the same effects as those of the image pickup module10and the like. In addition, it is easy for the image pickup module10B to seal the flying leads more surely with the sealing resin35. Furthermore, the strength of the flying leads31can be increased with the sealing resin35.

Fourth Embodiment

Next, description will be made on an image pickup module10C according to the fourth embodiment. The image pickup module10C is similar to the image pickup module10and the like. Therefore, the same constituent elements are attached with the same reference numerals and description thereof will be omitted.

As shown inFIG. 6, the image pickup module10C is configured such that an end surface20L of an image pickup chip20and an end surface30L of the wiring board30do not overlap each other, and flying leads31are bent.

The image pickup module10C has the same effects as those of the image pickup module10and the like. Furthermore, the image pickup module10C not only has high bonding strength but also has high degree of freedom of design. Therefore, the image pickup module10C can be configured in various ways.

Fifth Embodiment

Next, description will be made on an image pickup module10D according to the fifth embodiment. The image pickup module10D is similar to the image pickup module10and the like. Therefore, the same constituent elements are attached with the same reference numerals and description thereof will be omitted.

As shown inFIG. 7, the image pickup module10D is configured such that the electrodes22D1and22D2whose distances from the end surface20L are different are formed on the main surface, and a wiring board30D includes flying leads31D1,31D2which have different lengths.

That is, the flying lead31D1having a length L1is connected with the electrode22D1whose distance from the end surface20L is longer, and the flying lead31D2having a length L2is connected with the electrode22D2whose distance from the end surface20L is shorter. The electrodes22D1,22D2and the flying leads31D1,31D2are arranged alternately.

The image pickup module10D has the same effects as those of the image pickup module10and the like. Furthermore, the space between the bonding portions is large, which enables easy manufacturing.

The present invention is not limited to the above-described embodiments and various changes and modifications are possible in a range without changing the gist of the present invention.