Photodetector integrated circuit and manufacturing method thereof

Abstract

A photodetector integrated circuit includes a silicon bond pad, a light source die, and a photodiode. Conductive epoxy resin is formed on the silicon bonding pad through non-contact dispensing. The conductive epoxy resin is used for fixing the light source crystal grain on the silicon bonding pad. The light source crystal grain is used for emitting light towards a coding medium so as to generate modulated reflected light and transmit the modulated reflected light to the photodiode.

Description

Technical Field

[0001] This invention relates to a photodetector integrated circuit, and more particularly to a photodetector integrated circuit having silicon bonding pads on its surface as a substrate for configuring light source chips, and a method for manufacturing the same. Background Technology

[0002] Optical inspection devices typically include light-emitting diode (LED) chips and photodetector integrated circuits, respectively mounted on a leadframe or printed circuit board. Traditionally, conductive adhesive is first transferred to the surface of the leadframe or printed circuit board using a stamping tool, and then the LED chip and photodetector integrated circuit are bonded to the leadframe or printed circuit board.

[0003] However, the imprinting tool comes into direct contact with the imprinting surface when transferring the conductive adhesive, which may cause damage if the imprinting surface is made of a fragile material. Furthermore, the low fillet thickness of the conductive adhesive transferred during the imprinting process may result in insufficient coverage of the LED chip, leading to lower shear strength.

[0004] The information disclosed in the background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the relevant information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a photodetector integrated circuit and its fabrication method that directly places the light source die on the silicon bond pad of the photodetector integrated circuit to reduce the overall size of the package.

[0006] This invention provides a method for fabricating a photodetector integrated circuit by bonding a light source die to a silicon bonding pad of a photodetector integrated circuit using non-contact dispensing to avoid damaging the silicon bonding pad.

[0007] This invention provides a photodetector integrated circuit comprising a silicon bonding pad, a light source die, and a conductive epoxy resin. The silicon bonding pad is located on the surface of the photodetector integrated circuit. The conductive epoxy resin is used to fix and electrically connect the light source die to the silicon bonding pad.

[0008] The present invention also provides a method for fabricating a photodetector integrated circuit. The surface of the photodetector integrated circuit includes a silicon bonding pad. The fabrication method includes: applying non-contact adhesive to the silicon bonding pad to form a conductive epoxy resin region; disposing a light source die in the conductive epoxy resin region; forming a first bonding wire to bond the first bonding pad on the surface of the photodetector integrated circuit to the light source die; and forming a second bonding wire to bond the second bonding pad on the surface of the photodetector integrated circuit to the silicon bonding pad.

[0009] The present invention also provides a method for fabricating a photodetector integrated circuit. The surface of the photodetector integrated circuit includes a silicon bonding pad. The fabrication method includes: forming a second bonding wire to bond the second bonding pad on the surface of the photodetector integrated circuit to the silicon bonding pad; using non-contact dispensing on the silicon bonding pad to form a conductive epoxy resin region covering the solder joint between the second bonding wire and the silicon bonding pad; disposing a light source die in the conductive epoxy resin region; and forming a first bonding wire to bond the first bonding pad on the surface of the photodetector integrated circuit to the light source die.

[0010] To make the above and other objects, features and advantages of the present invention more apparent, a detailed description will be provided below with reference to the accompanying drawings. Furthermore, in the description of the present invention, the same components are denoted by the same reference numerals, which will be stated herein as well. Attached Figure Description

[0011] Figure 1 This is a top view of the photodetector integrated circuit according to an embodiment of the present invention;

[0012] Figure 2A This is a schematic diagram of the method for fabricating a photodetector integrated circuit according to the first embodiment of the present invention, in which columnar bumps are arranged on a silicon bonding pad;

[0013] Figure 2B This is a schematic diagram of forming conductive epoxy resin on a silicon bonding pad in the fabrication method of the photodetector integrated circuit according to the first embodiment of the present invention.

[0014] Figure 2C This is a schematic diagram of bonding a light source die to a conductive epoxy resin on a silicon bonding pad in the fabrication method of a photodetector integrated circuit according to the first embodiment of the present invention.

[0015] Figure 2D This is a schematic diagram of forming bonding leads connecting silicon bonding pads in the fabrication method of the photodetector integrated circuit according to the first embodiment of the present invention;

[0016] Figure 3AThis is a schematic diagram of the fabrication method of the photodetector integrated circuit according to the second embodiment of the present invention, in which columnar bumps and bonding leads are arranged on the silicon bonding pad;

[0017] Figure 3B This is a schematic diagram of forming conductive epoxy resin on a silicon bonding pad in the fabrication method of a photodetector integrated circuit according to the second embodiment of the present invention.

[0018] Figure 3C This is a schematic diagram illustrating the bonding of a light source die to a conductive epoxy resin on a silicon bonding pad in the fabrication method of a photodetector integrated circuit according to the second embodiment of the present invention; and

[0019] Figure 3D This is a schematic diagram of forming another bonding lead in the fabrication method of the photodetector integrated circuit according to the second embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures

[0021] 100 Photodetector Integrated Circuit

[0022] 101A Silicon Bonding Pad

[0023] 102 Light Source Grains

[0024] 103A First Bonding Lead

[0025] 103B Second Bonding Lead

[0026] 104 First photodiode

[0027] 105 Second photodiode

[0028] 109 Bonding Wire

[0029] 80 Conductive epoxy resin Detailed Implementation

[0030] One object of the present invention is to provide a photodetector integrated circuit and a method thereof for bonding a light source die to a silicon bonding pad of a photodetector integrated circuit using non-contact dispensing, which can reduce the package size, avoid damage to the silicon bonding pad during the manufacturing process, and improve the shear strength.

[0031] Please refer to Figure 1This is a top view of the photodetector integrated circuit 100 according to an embodiment of the present invention. The photodetector integrated circuit 100 according to an embodiment of the present invention is, for example, suitable for an absolute optical encoder. An absolute optical encoder includes an encoding medium comprising position slits (AB slits) and index slits and is disposed opposite the photodetector integrated circuit 100. An example of an encoding medium having position slits and index slits can be found, for example, in U.S. Patent Application No. US16 / 583,972, filed September 26, 2019, entitled "Optical Encoder with Partially Blocked Photodiode," the entire contents of which are incorporated herein by reference.

[0032] like Figure 1 As shown, the surface of the photodetector integrated circuit 100 includes a pad area (e.g., having multiple pads around it) and a circuit area (e.g., having multiple components in its center), which are connected to each other by multiple bonding wires 109. The surface of the photodetector integrated circuit 100 also includes a silicon bonding pad 101A, a light source die 102, a first bonding lead 103A, a second bonding lead 103B, a first photodiode 104, a second photodiode 105, and conductive epoxy resin 80, wherein the conductive epoxy resin 80 is, for example, silver epoxy resin, but is not limited thereto.

[0033] Silicon bonding pad 101A is disposed on the surface of the photodetector integrated circuit 100 and located between the first photodiode 104 and the second photodiode 105. In one embodiment, the first photodiode 104 is, for example, an incremental photodiode for receiving modulated light from a position slit in the encoding medium. In another embodiment, the second photodiode 105 is, for example, an absolute photodiode for receiving modulated light from an index slit in the encoding medium. Figure 1 In the diagram, the first photodiode 104 and the second photodiode 105 are shown as rectangular regions extending in the horizontal direction, for example, each photodiode contains multiple photodiodes arranged side by side along the horizontal direction. A silicon bonding pad 101A is located on the surface of the photodetector integrated circuit 100 between the first photodiode 104 and the second photodiode 105 in the vertical direction.

[0034] The light source die 102 is, for example, a light-emitting diode die (LED die) or a laser diode die, used to emit identifiable light to illuminate an coded medium (e.g., an coded disk, not shown). The light source die 102 is placed and bonded to the surface of the silicon bonding pad 101A, for example, by a pick-and-place mechanism. The operation of the pick-and-place mechanism is known and not the primary objective of this invention, and therefore will not be described in detail here.

[0035] Conductive epoxy resin 80 is formed on silicon bonding pad 101A using a non-contact dispensing technique to fix and electrically connect the light source chip 102 to the silicon bonding pad 101A. The non-contact dispensing technique is, for example, jetting dispensing. Figure 2B and Figure 3B The dispensing device 90 is used, but is not limited to. Since the silicon bonding pad 101A is more fragile than traditional printed circuit boards and lead frames, this invention uses non-contact dispensing to form the conductive epoxy resin 80, avoiding direct contact that could damage the surface of the silicon bonding pad 101A during the formation of the conductive epoxy resin 80. Furthermore, the amount of adhesive dispensed using non-contact dispensing is easily and precisely controlled to form the desired epoxy resin area and thickness on the surface of the silicon bonding pad 101A, completely covering the four corners of the light source die 102, thereby improving the shear strength of the light source die 102 bonded to the silicon bonding pad 101A.

[0036] Furthermore, since the surface of the silicon bonding pad 101A may experience reduced conductivity due to oxidation, the present invention can also form at least one stud bump on the surface of the silicon bonding pad 101A and within the coverage area of ​​the conductive epoxy resin 80 to electrically contact the conductive epoxy resin 80 before disposing the conductive epoxy resin 80 on the surface of the silicon bonding pad 101A. Since the oxide layer on the silicon bonding pad 101A can be penetrated when forming the stud bump using a wire bonder (e.g., ultrasonic energy), forming the stud bump can improve the electrical connection between the light source die 102 and the silicon bonding pad 101A.

[0037] It must be noted that, although this invention Figures 2A to 2D as well as Figures 3A to 3D Two columnar bumps 106A and 106B are shown next to the light source die 102; they are for illustrative purposes only and not intended to limit the invention. The number of the at least one columnar bump is not limited to two. The material of the at least one columnar bump may be, for example, gold, copper, aluminum, or a combination thereof.

[0038] Furthermore, the upper surface of the photodetector integrated circuit 100 also includes a first bonding pad 101B and a second bonding lead 101C. The first bonding pad 101B and the second bonding lead 101C are, for example, silicon bonding pads but are not directly connected to the silicon bonding pad 101A. Figure 2A and Figure 3A As shown. The first bonding pad 101B and the second bonding lead 101C are electrically coupled to other components of the photodetector integrated circuit 100 via trace 108, such as to the processor of the photodetector integrated circuit 100. This processor (not shown) is used, for example, to control the emission of light from the light source chip 102 and to process the detection signals from the first photodiode 104 and the second photodiode 105. The processor is, for example, an application-specific integrated circuit (ASIC), a programmable logic array (FPGA), a microprocessor (MCU), or a digital signal processor (DSP), but is not limited thereto.

[0039] The photodetector integrated circuit 100 further includes a first bonding lead 103A connecting a first bonding pad 101B on the surface of the photodetector integrated circuit 100 to a light source die 102. The photodetector integrated circuit 100 also includes a second bonding lead 103B connecting a second bonding pad 101C on the surface of the photodetector integrated circuit 100 to a silicon bonding pad 101A. The first bonding lead 103A and the second bonding lead 103B are formed, for example, using a wire bonding machine. The method of forming bonding leads using a wire bonding machine is known and will not be described in detail here.

[0040] In one embodiment, by controlling the amount of adhesive dispensed from the dispensing machine, the coverage area of ​​the conductive epoxy resin 80 can be kept within a predetermined range and have a certain height. For example, see... Figure 2D The solder joint between the second bonding lead 103B and the silicon bonding pad 101A is located outside the coverage area of ​​the conductive epoxy resin 80 on the silicon bonding pad 101A.

[0041] In another embodiment, to enhance the electrical connection between the light source die 102 and the second bonding lead 103B (e.g., in an embodiment without pillar bumps), the solder joint between the second bonding lead 103B and the silicon bonding pad 101A is located within the coverage area of ​​the conductive epoxy resin 80 on the silicon bonding pad 101A, for example, referring to... Figure 3D As shown.

[0042] For example, refer to Figures 2A to 2D As shown, it is the photodetector integrated circuit 100 of the first embodiment of the present invention (for example, shown in...). Figure 1 A schematic diagram illustrating each step of the production method of ). Figures 2A to 2D Only the components directly related to this invention are shown, and some components are omitted.

[0043] First, at least one columnar bump (e.g., shown as 106A and 106B, but not limited to two) is formed (e.g., using a wire bonding machine) on the silicone bonding pad 101A in the area where the conductive epoxy resin 80 is to be formed, for example, referring to Figure 2A .

[0044] Next, non-contact dispensing is used on the silicone bonding pad 101A to form a conductive epoxy resin 80. For example... Figure 2B The dispensing machine 90 is used to form a conductive epoxy resin 80. The conductive epoxy resin 80 covers the columnar bumps 106A and 106B for electrical contact. As described above, at least one columnar bump can be used to penetrate the oxide layer on the surface of the silicon bonding pad 101A.

[0045] Next, the light source chip 102 is disposed (e.g., using a pick-and-place mechanism) in the region of the conductive epoxy resin 80, for example, referring to... Figure 2C By controlling the amount of adhesive dispensed via non-contact dispensing, conductive epoxy resin 80 can completely coat the four corners of the light source crystal 102.

[0046] Reference Figure 2D Finally, a first bonding lead 103A is formed (e.g., using a wire bonding machine) to bond the first bonding pad 101B on the surface of the photodetector integrated circuit 100 to the bonding pad on the light source die 102, and a second bonding lead 103B is formed (e.g., using a wire bonding machine) to bond the second bonding pad 101C on the surface of the photodetector integrated circuit 100 to the silicon bonding pad 101A. The formation order of the first bonding lead 103A and the second bonding lead 103B is not specifically limited. This completes the process of directly mounting the light source die 102 onto the photodetector integrated circuit 100.

[0047] In the first embodiment, the solder joint between the second bonding lead 103B and the silicon bonding pad 101A is located outside the coverage area of ​​the conductive epoxy resin 80 on the silicon bonding pad 101A. Furthermore, the first embodiment does not require the formation of columnar bumps if the oxide layer on the surface of the silicon bonding pad 101A is not a concern.

[0048] For example, refer to Figures 3A to 3D As shown, it is the photodetector integrated circuit 100 of the second embodiment of the present invention (for example, shown in...). Figure 1 A diagram illustrating each step of the production process. Figures 3A to 3D Only the components directly related to this invention are shown, and some components are omitted.

[0049] First, at least one columnar bump (e.g., shown as 106A and 106B, but not limited to two) is formed (e.g., using a wire bonding machine) on the silicone bonding pad 101A in the area where the conductive epoxy resin 80 is to be formed, for example, referring to Figure 3A Furthermore, before or after forming the columnar bumps, a second bonding lead 103B is formed (e.g., using a wire bonding machine) to bond a second bonding pad 101C to a silicon bonding pad 101A on the surface of the photodetector integrated circuit 100.

[0050] Next, non-contact dispensing is used on the silicon bonding pad 101A to form an area of ​​conductive epoxy resin 80 covering the solder joint between the second bonding lead 103B and the silicon bonding pad 101A, thereby improving the electrical connection between the light source die 102 and the second bonding lead 103B. For example, Figure 3B The dispensing machine 90 is used to form conductive epoxy resin 80. Similarly, the areas of conductive epoxy resin 80 are covered with columnar bumps 106A and 106B for electrical contact with them.

[0051] Next, the light source chip 102 is disposed (e.g., using a pick-and-place mechanism) in the region of the conductive epoxy resin 80, for example, referring to... Figure 3C .

[0052] Reference Figure 3D Finally, (e.g., using a wire bonding machine) a first bonding lead 103A is formed to bond the first bonding pad 101B on the surface of the photodetector integrated circuit 100 to the bonding pad on the light source die 102. This completes the process of directly mounting the light source die 102 onto the photodetector integrated circuit 100.

[0053] The main difference between the second embodiment and the first embodiment lies in the coverage area of ​​the conductive epoxy resin 80 and the time taken to form the second bonding lead 103B.

[0054] It should be noted that although the silicon bonding pad 101A is shown as rectangular in the drawings, the present invention is not limited thereto. The silicon bonding pad 101A can be other shapes, and there are no specific limitations, as long as it can accommodate the light source die 102.

[0055] It should be noted that the photodetector integrated circuit 100 of this embodiment of the invention is not limited to using wire bonding technology to connect to external circuits (i.e., via 109), and other technologies, such as flip-chip bonding or tape-and-reel automatic bonding (TAB), may also be used.

[0056] In this invention, the dispensing machine 90 can be a commercially available product, and there are no specific restrictions.

[0057] In summary, in known photodetector devices, the light-emitting diode (LED) chip and the photodetector integrated circuit are respectively mounted on a lead frame or printed circuit board, resulting in a relatively large overall encapsulated structure. Furthermore, since silicon bonding pads are more fragile than lead frames or printed circuit boards, known imprinting processes are not suitable for transferring conductive adhesive onto the silicon bonding pads. Therefore, this invention provides a photodetector integrated circuit that uses non-contact dispensing to directly bond the light source chip to the silicon bonding pad of the photodetector (see reference). Figure 1 ) and its production method (refer to Figures 2A to 2D and Figures 3A to 3DIt has the advantages of reducing package volume, avoiding damage to the silicon bonding pad, and improving shear strength.

[0058] While the present invention has been disclosed through the foregoing examples, it is not intended to limit the invention. Anyone skilled in the art to which this invention pertains can make various modifications and alterations without departing from the spirit and scope of the invention. Therefore, the scope of protection of this invention shall be determined by the appended claims.

Claims

1. A photodetector integrated circuit, comprising: a silicon bonding pad on a surface of the photodetector integrated circuit; a light source die; and a conductive epoxy for securing and electrically connecting the light source die to the silicon bonding pad. The photodetector integrated circuit further comprises a first photodiode and a second photodiode on the surface.

2. The photodetector integrated circuit of claim 1, wherein, The silicon bonding pad is between the first photodiode and the second photodiode on the surface of the photodetector integrated circuit.

3. The photodetector integrated circuit of claim 2, wherein, 4. The photodetector integrated circuit of claim 1, further comprising at least one stud bump formed on the surface of the photodetector integrated circuit and electrically contacting the conductive epoxy. The at least one stud bump is made of gold, copper, aluminum, or a combination thereof.

5. The photodetector integrated circuit of claim 4, wherein, 6. The photodetector integrated circuit of claim 1, further comprising: a first bonding wire connecting a first bonding pad of the surface of the photodetector integrated circuit to the light source die; and a second bonding wire connecting a second bonding pad of the surface of the photodetector integrated circuit to the silicon bonding pad. The solder joint of the second bonding wire to the silicon bonding pad is outside a coverage area of the conductive epoxy on the silicon bonding pad.

7. The photodetector integrated circuit of claim 6, wherein, The solder joint of the second bonding wire to the silicon bonding pad is inside the coverage area of the conductive epoxy on the silicon bonding pad.

8. The photodetector integrated circuit of claim 6, wherein, 9. A method for fabricating a photodetector integrated circuit having a surface with a silicon bonding pad, the method comprising: forming a conductive epoxy area on the silicon bonding pad using non-contact dispensing; disposing a light source die on the conductive epoxy area; forming a first bonding wire connecting a first bonding pad of the surface of the photodetector integrated circuit to the light source die; and forming a second bonding wire connecting a second bonding pad of the surface of the photodetector integrated circuit to the silicon bonding pad. Before forming the conductive epoxy area, the method further comprises:

10. The production method according to claim 9, wherein forming at least one stud bump on the silicon bonding pad within the conductive epoxy area. The at least one stud bump is made of gold, copper, aluminum, or a combination thereof.

11. The production method according to claim 10, wherein The photodetector integrated circuit further comprises a first photodiode and a second photodiode on the surface.

12. The production method according to claim 9, wherein The silicon bonding pad is between the first photodiode and the second photodiode on the surface of the photodetector integrated circuit.

13. The production method according to claim 12, wherein The solder joint of the second bonding wire to the silicon bonding pad is outside the conductive epoxy area on the silicon bonding pad.

14. The production method according to claim 9, wherein 15. A method for fabricating a photodetector integrated circuit having a surface with a silicon bonding pad, the method comprising: forming a second bonding wire connecting a second bonding pad of the surface of the photodetector integrated circuit to the silicon bonding pad; forming a conductive epoxy area covering a solder joint of the second bonding wire to the silicon bonding pad on the silicon bonding pad using non-contact dispensing; ​ a light source die is disposed on the conductive epoxy region; and a first bonding wire is formed to bond a first bonding pad of the surface of the photodetector integrated circuit and the light source die.

16. The method of claim 15, before forming the conductive epoxy region, the method further comprises: forming at least one stud bump on the silicon bonding pad within the conductive epoxy region.

17. The method of manufacturing according to claim 16, wherein, The material of the at least one stud bump is gold, copper, aluminum, or a combination thereof.

18. The method of manufacturing according to claim 15, wherein, The photodetector integrated circuit further comprises a first photodiode and a second photodiode on the surface.

19. The method of manufacturing according to claim 18, wherein, The silicon bonding pad is between the first photodiode and the second photodiode on the surface of the photodetector integrated circuit.

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