Patent Application
20160322531
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-094267, filed May 1, 2015, the entire contents of which are incorporated herein by reference.
Embodiments of the present invention relate to a semiconductor device and an optical coupling device.
An optical coupling device, which is also called a photo-coupler, includes a light emitting chip, a light receiving chip, a lead frame on which each of these chips is mounted, and a resin for covering them.
A portion of the lead frame protrudes outside the resin. Therefore, when adhesion between the resin and the lead frame is not high, moisture contacting the lead frame portion protruding from the resin may infiltrate into the resin due to a capillary phenomenon or the like, which may ultimately cause problems such as separation of the light emitting chip from the resin and failure of the device.
FIG.6 is a diagram showing an example in which end portions of the lead frames are provided on the same side.
In general, according to one embodiment, a semiconductor device includes a first chip (e.g., a light-emitting diode chip) in a first resin. A second resin covers the first resin. A first lead frame is in the first resin and has a first end portion extending through the second resin to the outside. A second end portion of the first lead frame terminates in the second resin—that is, the end is within the second resin and does not penetrate completely through the full thickness of the second resin. A second lead frame is also in the first resin, but spaced from the first lead frame. The second lead frame has a first end portion disposed in the first resin and a second end portion terminating in the second resin. The first chip is disposed on the first end portion of the second lead frame. A first bonding wire electrically connects the first chip to the first lead frame either directly or via the second lead frame.
Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following embodiments, the characteristic configuration and operation of a semiconductor device and an optical coupling device will be mainly described, and there are configurations and operations not explicitly described but that are readily apparent in view of the present disclosure or otherwise known to those of ordinary skill which are also included in the scope of the present disclosure.
The light emitting chip 3 may be a chip only including a light emitting element, or may include a packaged substrate on which a light emitting element is mounted with various circuit elements associated with operation and/or control of the light emitting element. The light receiving chip 4 is a semiconductor device including a light receiving element therein.
The light emitting chip 3 and the light receiving chip 4 are disposed such that they face each other in a vertical direction (e.g., up-down page direction in
Since the first resin portion 6 is transparent, even when the first resin portion 6 is present between the light emitting chip 3 and the light receiving chip 4, light from the light emitting chip 3 may be received by the light receiving chip 4 without significant loss. In this case, transparent means that there is a significant degree of transparency to an emission wavelength of the light emitting chip 3, but it is not required for the first resin portion 6 be entirely non-absorbing at the emission wavelength.
The second resin portion 7 is a substantially non-transparent material (for example, black (absorbing) resin or white (reflecting) resin), which shields light coming from outside of the optical coupling device 1 so as to prevent the light receiving chip 4 from receiving light from the outside. In this case, non-transparent means that there is no significant transmission of light at the emission wavelength of the light emitting chip 3.
Among the plurality of lead frames 5a-5g, the lead frames 5a-5c are provided to achieve conduction to the light emitting chip 3, and the lead frames 5d-5g are provided to achieve electrical connections to the light receiving chip 4. The lead frames 5a-5g are arranged apart from one another.
As shown in
A portion of the lead frame (first lead frame) 5b is arranged in the first resin portion 6. One end portion of lead frame 5b is arranged outside the second resin portion 7. Another end portion 5m of lead frame 5b is disposed in the second resin portion 7. More specifically, the lead frame 5b is in an L-shape, as depicted in
A portion of the lead frame (second lead frame) 5c is in the first resin portion 6, and one end portion 5n of lead frame 5c is disposed in the second resin portion 7. More specifically, the end portion 5n of the lead frame 5c protrudes outward from the first resin portion 6 on the end surface 2c side of the optical coupling device 1, and but terminates inside the second resin portion 7.
Thus, both of the end portion 5m of the lead frame 5b and the end portion 5n of the lead frame 5c are arranged on the end surface 2c side of the optical coupling device 1. The lead frame 5b and the lead frame 5c protrude from the first resin portion 6, and the protruding portions (5m and 5n) are covered with the second resin portion 7, thereby improving the adhesion between the first resin section 6 and the second resin portion 7.
The light emitting chip 3 is mounted on the lead frame 5c. The lead frame 5a is connected to an anode of the light emitting chip 3 by a bonding wire 8a. The lead frame 5b is connected to a cathode of the light emitting chip 3 by another bonding wire 8b. Although the lead frame 5b and the lead frame 5c are depicted as connected by the bonding wire 8b in
The light emitting chip 3 and a portion of the bonding wires 8a and 8b are covered with a third resin portion 9 comprising a transparent silicone material. Transparent in this case also means that there is transparency to the emission wavelength of the light emitting chip 3.
The reason that the light emitting chip 3 is covered with the third resin portion 9 is as follows. An LED that includes the light emitting chip 3 is often made of a compound semiconductor (e.g., GaN), and the compound semiconductor is typically more brittle than silicon and generally has more inherent crystal defects therein. For this reason, the light emitting chip 3 is more easily affected by environmental temperature and stress, and therefore, is more easily deteriorated when formed of compound semiconductor. Therefore, the light emitting chip 3 is covered with the third resin portion 9, so as to be less affected by temperature changes and stress variations. When the light emitting chip 3 is made of silicon material, inclusion of the third resin portion 9 may be unnecessary.
As shown in
The lead frames 5e and 5f extend from inside of the first resin portion 6 to the outside of the second resin portion 7. More specifically, end portions of the lead frames 5d, 5e and 5f protrude outward from the second resin portion 7 on the end surface 2b side of the optical coupling device 1.
For the lead frame (fourth lead frame) 5g a portion on which the light receiving chip for is disposed is inside the first resin portion 6 and one end portion 5p of the lead frame 5g protrudes outward from the first resin portion 6 on the end surface 2d side of the optical coupling device 1 and terminates inside the second resin portion 7.
Thus, both of the end portion 5q of the lead frame 5d and the end portion 5p of the lead frame 5g are arranged on the end surface 2d side of the optical coupling device 1. These end portions (5q and 5p) of lead frame 5d and the lead frame 5g protrude from the first resin portion 6 and are covered with the second resin portion 7, thereby improving the adhesion between the first resin section 6 and the second resin portion 7.
The light receiving chip 4 is mounted on the lead frame 5g. The lead frames 5d, 5e and 5f are connected to the light receiving chip 4 by different bonding wires 8c, 8d and 8e, respectively. The lead frames 5d and 5f are connected to, for example, a grounding terminal of the light receiving chip 4, and the lead frame 5e is connected to, for example, a power supply terminal of the light receiving chip 4.
Note that the number and arrangement of the lead frames provided in the optical coupling device 1 are not limited to those specifically depicted in the figures. In some embodiments, the optical coupling device 1 may be a surface mounted type, such as an SOP (Small Outline Package), or may be an insert-mounted type, such as a DIP (Dual Inline Package). A multi-channel configuration in which a plurality of light emitting chips 3 and the light receiving chips 4 are incorporated into one optical coupling device 1 may also be adopted.
As described above, a first feature of the present embodiment is that the lead frame 5b (connected to the cathode of the light emitting chip 3) and the lead frame 5c (on which the light emitting chip 3 is mounted) are arranged apart from each other, and the lead frame 5d (connected to the grounding terminal of the light receiving chip 4) and the lead frame 5e (on which the light receiving chip 4 is mounted) are arranged apart from each other. Further, a second feature of the present embodiment is that respective end portions 5m and 5n of the lead frames 5b and 5c for the light emitting chip 3, and the respective end portions 5q and 5p of the lead frames 5d and 5g for the light receiving chip 4 terminate in the second resin portion 7.
The lead frame 5b and the lead frame 5c may be formed by cutting of a single lead frame 5h, for example (see
As described above, the lead frame 5b and the lead frame 5c are arranged apart from each other, thus, moisture condensing on or otherwise contacting the lead frame 5b which protrudes outward from the outer surface of the optical coupling device 1 is unable to easily reach the light emitting chip 3 via a pathway created or provided by the lead frame 5b because the lead frame 5b is not directly connected to the light emitting chip 3. Similarly, the lead frame 5d and the lead frame 5g are arranged apart from each other, thus, moisture condensing on or otherwise contacting the lead frame 5d connected to the grounding terminal which protrudes outward from the outer surface of the optical coupling device 1 is unable to easily reach the light receiving chip 4 via a pathway created or provided by the lead frame 5d.
As shown in
Further, as shown in
As depicted in
Furthermore, as depicted in
In contrast, in the present embodiment, as depicted in
Since the lead frames 5c and 5g on which the light emitting chip 3 and the light receiving chip 4 are mounted, respectively, are contained in the first resin portion 6 and the second resin portion 7, when deformation is generated by the linear thermal expansion coefficient difference between the lead frames 5c and 5g and the first and second resin portions 6 and 7, due, for example, to a temperature difference between the temperature at the time of molding and room temperature, and the temperature and humidity difference in an environment that the product operates in after shipment, the deformation in the longitudinal direction will be larger than that in the shorter direction according to the outer shape of the first and second resin portions 6 and 7 themselves because interfaces between the first and second resin portions 6 and 7 and the lead frames 5c and 5g are continuous. Since the interfaces between the first and second resin portions 6 and 7 and the lead frames 5c and 5g are fixed, the light emitting chip 3 and the light receiving chip 4 are deformed in such that the chips are pressed against the lead frames 5c and 5g. Consequently, separation of both of chips 3 and 4 from the lead frames 5c and 5g is suppressed, thus, the reliability is improved. On the other hand, in the comparative example in
Similarly, in the present embodiment, as shown in
Before or after the steps S1 and S2 described above, light receiving chip 4 is mounted on the wide portion of the lead frame 5i, one end of which is in a U-shape (step S3). Next, the light receiving chip 4 and the two lead frames 5e and 5f are connected by the bonding wires 8d and 8e, respectively, and the wide portion of the lead frame 5i and the other end of the lead frame 5i are connected by the bonding wire 8c (step S4). The reason that the wide portion of the lead frame 5i and the other end of the lead frame 5i are connected by the bonding wire 8c is to achieve the electrical connection of the two lead frames 5 which will be formed by cutting the lead frame 5i.
Next, the light emitting chip 3 and the bonding wires 8a and 8b are covered with the third resin portion 9 (step S5). By covering with the third resin portion 9, the light emitting chip 3 will be less affected by temperature changes and stress variations, and the separation of the bonding wires 8a and 8b may also be prevented.
Next, the light emitting chip 3 and the light receiving chip 4 are vertically placed such that the chips face each other, and the chips are encased in (covered with) the first resin portion 6 (step S6). At this time, as shown in
Next, the portions (shown by broken lines in
Note that since the lead frame 5b and the lead frame 5c which are arranged apart from each other are connected by the bonding wire 8b, and similarly, the lead frame 5d and the lead frame 5g which are arranged apart from each other are connected by the bonding wire 8c, conductivity between these elements need not be impaired.
Next, as shown in
The lead frames 5b, 5c, 5d and 5g protruding from the first resin portion 6 are engaged with the second resin portion 7, rather than penetrating completely through the second resin portion 7, thus, adhesion between the first resin portion 6 and the second resin portion 7 is improved. In order to achieve good workability, the length of the protrusion into the second resin portion 7 is approximately between 50 μm and 150 μm; more specifically, the range from 50 μm to 100 μm is more desirable such that the thickness of the second resin portion 7 does not change significantly. The thickness of the second resin portion 7 is approximately between 0.150 μm and 300 μm, because such thickness provides the necessary light shielding property and resin cracking is significantly generated at end portions 5m, 5n, 5p, and 5q of the lead frames 5b, 5c, 5d and 5g. In practice, the thickness of the second resin portion 7 and the protrusion depth of the end portions 5m, 5n, 5p, and 5q can be set according to desired strength and reliability of the end-use device.
When the lead frames 5h and 5i are cut at the portions shown by broken lines to form the lead frames 5b and 5c and the lead frames 5d and 5g, heat generated in the light emitting chip 3 and the light receiving chip 4 is less likely to pass through the lead frames 5b and 5d to escape to the outside of the optical coupling device 1. Thus, it is desirable to otherwise promote the diffusion of heat from the interior of optical coupling device 1, such as by expanding the area of the lead frames 5b, 5c, 5d and 5g on which the light emitting chip 3 or the light receiving chip 4 is mounted.
Thus, in this present embodiment, since the lead frame 5b connected to the cathode of the light emitting chip 3, and the lead frame 5c on which the light emitting chip 3 is mounted are arranged apart from each other, and the lead frame 5d connected to the grounding terminal of the light receiving chip 4 and the lead frame 5g on which the light receiving chip 4 is mounted are arranged apart from each other, even when moisture adhering to the lead frames 5b and 5d at the outside of the second resin portion 7 intrudes into the first resin portion 6 through the lead frames 5b and 5d, it is possible to prevent the moisture from reaching the lead frames 5c and 5g on which the light emitting chip 3 and the light receiving chip 4 are mounted, respectively, and to prevent separation at the interface between the third resin portion 9 and the light emitting chip 3 (light receiving chip 4) due to the moisture from the outside.
In addition, the end portions of the lead frames 5c and 5g protruding from the first resin portion 6 are engaged with the second resin portion 7, thus, adhesion between the second resin portion 7 and the first resin portion 6 may be improved. That is, the end portions 5m, 5n, 5p and 5q of the protruding lead frames 5b, 5c, 5d and 5g are arranged between the first resin portion 6 and the second resin portion 7 on the two facing end surfaces 2c and 2d side of the optical coupling device 1, thus, the adhesion between the first resin portion 6 and the second resin portion 7 may be enhanced. In particular, when the end portions 5m and 5n are arranged on the two facing end surfaces 2c and 2d side of the optical coupling device 1, symmetry is increased, and the lead frames 5c and 5g on which the light emitting chip 3 and the light receiving chip 4 are mounted, respectively, may be placed substantially at the center of the optical coupling device 1, thus, the strength of the optical coupling device 1 is increased.
Although, in the first embodiment described above, the example is described that the respective one end portions of the lead frames 5d and 5g are provided on the end surface 2d opposite to the end surface 2c of the first resin portion 6 on which the respective one end portions of the lead frames 5b and 5c are provided, the respective one end portions of the lead frames 5b, 5c, 5d and 5g may be provided on the same end surface 2c side of the first resin portion 6.
When arranged as shown in
Although, in the first and second embodiments described above, the example applied to the optical coupling device 1 is described, the embodiments of the present disclosure may be widely applied to various semiconductor devices in which moisture adhering to a lead frame protruding outside the resin portion may intrude into the resin portion. Therefore, the semiconductor device to which the present embodiment may be applied does not necessarily have the light emitting chip 3 and the light receiving chip 4. According to the present embodiment, two separated lead frames (5b, 5c), (5d, 5g) are electrically conducted by the bonding wires 8b and 8c, and thus, it is possible to prevent moisture adhering to the lead frames protruding outside the resin portion from intruding around the various chips in the resin portion.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-094267 | May 2015 | JP | national |
