JP3721656B2 - Optical data link - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical data link used in the field of optical communications.
[0002]
[Prior art]
The light emitting / receiving elements of the conventional optical data link are connected to the drive circuit and the amplifier circuit via bonding wires.
[0003]
[Problems to be solved by the invention]
However, the bonding wire extending from the drive circuit to the light emitting element is an elongated conductor and functions as an inductance for high frequencies. Therefore, the time constant due to the bonding wire is increased, and high-speed switching of the light emitting element by the drive circuit is limited. In addition, when a current flowing in the bonding wire generates a magnetic field around the current and the current value changes abruptly, high-frequency noise or the like propagates to the adjacent bonding wire. In particular, when the light emitting element and the light receiving element are arranged in the same package, the high frequency noise generated by the bonding wire extending from the drive circuit of the light emitting element propagates to the bonding wire connecting the light receiving element and the amplifier circuit, and the optical data link. The performance of is limited.
[0004]
The present invention has been made to solve such problems, and provides an optical data link capable of reducing noise.
[0005]
[Means for Solving the Problems]
In the optical data link according to the present invention, the electrode on the light emitting surface side is electrically connected to the electrode provided on the surface opposite to the light emitting surface by a through hole, and the electrode is disposed on the surface opposite to the light emitting surface. a surface-emitting light-emitting element collected, a first flip chip drive circuit is formed for driving the light emitting element comprises a light emitting surface opposite to the surface of the light emitting element, the driving of the first flip-chip The light emitting element is bonded to the first flip chip so as to face the circuit formation surface . According to the present optical data link, since the light emitting element and the drive circuit are connected without using a bonding wire by using a flip chip, the light emitting element can be switched at a high speed and noise can be reduced. In particular, according to the present optical data link, it is possible to reduce noise caused by a current flowing between the light emitting element and the drive circuit.
[0006]
An optical data link according to the present invention includes a second flip chip in which a back-illuminated light receiving element having electrodes gathered on the side opposite to the light receiving surface and an amplifier circuit for amplifying a signal from the light receiving element are formed. The light receiving element is bonded to the second flip chip so that the surface opposite to the light receiving surface of the light receiving element faces the amplification circuit forming surface of the second flip chip. To do. According to this optical data link, by using a flip chip , a light emitting element, a light receiving element, a drive circuit (first flip chip) and an amplifier circuit (second flip chip) are arranged in a single package. However, noise due to the current flowing between the light emitting element and the drive circuit is not superimposed on the signal from the light receiving element, and the noise can be reduced. Further, when the light emitting element, the light receiving element, the drive circuit (first flip chip) and the amplifier circuit (second flip chip) are arranged in a single package, the handling thereof can be facilitated.
[0007]
The optical data link according to the present invention further includes a first condensing lens provided on the light emitting surface side of the light emitting element, and a second condensing lens provided on the light receiving surface side of the light receiving element. Also good.
Another optical data link according to the present invention includes a back-illuminated light receiving element in which electrodes are collected on the surface opposite to the light receiving surface, a flip chip on which an amplifier circuit for amplifying a signal from the light receiving element is formed, The light receiving element is bonded to the flip chip so that the surface opposite to the light receiving surface of the light receiving element faces the amplifier circuit forming surface of the flip chip. According to the present optical data link, since the light receiving element and the amplifier circuit are connected without using a bonding wire by using a flip chip, it is possible to reduce noise superimposed on a signal from the light receiving element. .
Note that the light emitting element is an element such as a light emitting diode or a laser diode. A flip chip is a semiconductor chip in which all terminals are gathered on one surface and formed in the form of a mountain-shaped contact made of solder or gold. The light receiving element is an element such as a PIN photodiode or an avalanche photodiode.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the optical data link according to the embodiment will be described. In addition, the same code | symbol is used for the same element and the overlapping description is abbreviate | omitted. The terms “upper” and “lower” are based on the top and bottom of the drawing.
[0009]
FIG. 1 is a three-dimensional exploded view of an optical data link. This optical data link includes a package main body 1 and a package substrate 3 that seals the open end 2 of the main body 1. The package body 1 and the substrate 2 are combined to form a package. Two openings 6 and 7 into which optical fibers (ferrules) 4 and 5 are inserted are provided on the surface of the package body 1 facing the opening end 2. When the optical fibers 4 and 5 are inserted into the package body 1 from the openings 6 and 7, respectively, the optical fibers 4 and 5 are held by sleeves 8 and 9 aligned in a direction through the openings 6 and 7, respectively. Is done. The light receiving device 10 and the light emitting device 110 are arranged on the sleeves 8 and 9 extending along the longitudinal direction substrate 3 side, respectively. The light receiving device 10 and the light emitting device 110 are fixed on the substrate 3.
[0010]
An optical signal introduced into the package body 1 from the optical fiber 4 is received by the light receiving device 10, and is connected to the substrate via bonding wires 11, 12 and 13 and metal wirings 14, 15 and 16 formed on the substrate 3. 3 is output from the lead pins 17, 18, and 19 that penetrate 3.
[0011]
Signals input to the present optical data link from the lead pins 20, 21 and 22 penetrating the substrate 3 are transmitted through the metal wirings 23, 24 and 25 and bonding wires 26, 27 and 28 formed on the substrate 3. 110 and output as an optical signal in the direction of the optical fiber 5.
[0012]
FIG. 2 is a cross-sectional view taken along the line AA of the component including the substrate 3, the light receiving device 10, and the light emitting device 110 of FIG. 1. The light receiving device 10 includes a flip chip 30 on which a light receiving element 29 is flip chip bonded. The flip chip 30 includes electrode pads 32 and 33 formed on the surface of the semiconductor substrate 31 and bumps 34 and 35 formed on the electrode pads 32 and 33. The bumps 34 and 35 are made of a compound containing gold or lead, particularly AuSn or AuPb. The flip chip 30 is a semiconductor chip on which these bumps 34 and 35 are formed, and is an integrated circuit (IC) chip on which an amplification circuit 36 for amplifying an electric signal from the light receiving element 29 is formed. The electrical signal output from the light receiving element 29 is input to the amplifier circuit 36 via the bumps 34 and 35, and optical data is transmitted via the electrode pads 37 and 38 formed on the surface of the flip chip 30 and the bonding wires 11 and 13. Output outside the link. The flip chip 30 is fixed to the package substrate 3 with an adhesive 39.
[0013]
The flip chip 30 and the light receiving element 29 are electrically connected via bumps 34, 35 and 40, 41 formed on the respective surfaces. Note that eutectic regions 42 and 43 formed at the time of bonding are interposed at the boundaries between the bumps 34 and 35 and 40 and 41. The light receiving element 29 is composed of a photodiode such as a PIN photodiode or an avalanche photodiode. On the surface of the light receiving element 29 opposite to the flip chip 30, that is, on the surface of the light receiving element 29 on the sleeve 8 side, an optical signal input from the optical fiber 4 to the optical data link is received via the adhesive 44. A spherical lens 45 for focusing on the light receiving surface is attached. The light receiving surface of the light receiving element 29 is preferably on the flip chip 30 side, but may be on the sleeve 8 side.
[0014]
A light emitting device 110 is fixed in a region adjacent to the light receiving device 10 on the substrate 3. The light emitting device 110 includes a flip chip 47 on which a light emitting element 46 is flip chip bonded. The flip chip 47 includes electrode pads 49 and 50 formed on the surface of the semiconductor substrate 48 and bumps 51 and 52 formed on the electrode pads 49 and 50. The bumps 51 and 52 are made of a compound containing gold or lead, particularly AuSn or AuPb. The flip chip 47 is a semiconductor chip on which these bumps 51 and 52 are formed, and an IC chip on which a drive circuit 53 for driving the light emitting element 46 is formed. Electrical signals input from the outside of the optical data link are input to the drive circuit 53 via the bonding wires 26 and 28 and electrode pads 54 and 55 formed on the surface of the flip chip 47, and the drive output from the drive circuit 53 is output. The signal is input to the light emitting element 46 through the bumps 51 and 52. The flip chip 47 is fixed to the package substrate 3 with an adhesive 56.
[0015]
The flip chip 47 and the light emitting element 46 are electrically connected via bumps 51, 52 and 57, 58 formed on the respective surfaces. Incidentally, eutectic regions 59 and 60 formed at the time of bonding are interposed at the boundaries between the bumps 51 and 52 and 57 and 58. The light emitting element 46 is composed of a light emitting diode or a surface emitting laser diode. The optical signal output from the light emitting element 26 is focused on the end face of the optical fiber 5 via the adhesive 59 on the surface of the light emitting element 46 opposite to the flip chip 47, that is, on the surface of the light emitting element 46 on the sleeve 9 side. A spherical lens 80 is attached.
[0016]
FIG. 3 is a cross-sectional view showing the structure of the light receiving element 29. The light receiving element 29 includes a semiconductor substrate 61 and electrodes 62 and 63 to which bumps 40 and 41 provided on the lower side of the semiconductor substrate 61 are fixed. A buried n-type semiconductor layer 64 is provided below the substrate 61 and is electrically connected to the n-type electrode 63. An i-type light absorption layer 66 is located between the p-type semiconductor layer 65 and the n-type semiconductor layer 64 electrically connected to the p-type electrode 62, and these form a PIN structure photodiode. . The light-receiving surface defined by the PIN structure of the light-receiving element 29 is closer to the bumps 40 and 41 than the ball lens 45 and constitutes a back-illuminated photodiode. Insulating films 67 and 68 are formed on the exposed surfaces of the p-type semiconductor layer 65 and the light absorption layer 66.
[0017]
FIG. 4 is a cross-sectional view showing the structure of the light emitting element 46. The light emitting element 46 includes a semiconductor substrate 68 and electrodes 69 and 70 provided on the lower surface of the substrate 68. Bumps 57 and 58 are fixed to the electrodes 69 and 70, respectively. The electrode 69 passes through a through hole penetrating the substrate 68 in the thickness direction, and is electrically connected to an electrode 71 formed on the surface of the substrate 68 on the lens 80 side. The electrode 71 is in contact with the clad layer 72 formed in the substrate 68, and an active layer 73 is formed between the clad layer 72 and the clad layer 73, and these have surface emission of a double hetero structure. A diode is formed. The side surfaces of these semiconductor layers 72 to 74 are surrounded by a current blocking layer or insulating layer 74. When a drive voltage is applied between the electrodes 70 and 71, a current is injected into the active layer 74 and light is emitted from the active layer 74. Note that an insulating film 75 is interposed between the electrodes 69 and 71 and the substrate 68.
[0018]
The current input to the drive circuit 53 is 80 mA when the light emitting element 46 is a light emitting diode, and 25 mA when the light emitting element 46 is a laser diode. In this optical data link, when the current of 50 mA is supplied to the drive circuit 53 and the light emitting element 46 is switched at 100 Mbps, the light receiving device 10 can be brought within 1 cm, so that the optical data link can be downsized. is there.
[0019]
As described above, the present optical data link includes the packages 1 and 3, the light receiving elements 29 disposed in the packages 1 and 3, and the signals from the light receiving elements 29 disposed in the packages 1 and 3. And a light emitting element 46 disposed in the packages 1 and 3, and a flip chip 47 on which the light emitting element 46 is bonded and a driving circuit 53 for driving the light emitting element 46 is formed. According to this optical data link, the light receiving element 29, the light emitting element 46, the amplifier circuit 36, and the flip chip 47 can be arranged in a single package 1 and 3, thereby facilitating the handling and flipping. By using the chip 47, noise caused by the current flowing between the light emitting element 46 and the drive circuit 53 is superimposed on the signal from the light receiving element 29 even if these are arranged in the single packages 1 and 3. The noise can be reduced.
[0020]
FIG. 5 is a three-dimensional exploded view of a light emitting device used for an optical data link. In the light emitting device, the package body 1A has a cylindrical shape, and the end surface of the package body 1A is fixed to the package substrate 3. That is, the light emitting device for the optical data link includes a light emitting element 46 and a flip chip 46 on which the light emitting element 46 is bonded and a drive circuit 53 for driving the light emitting element 46 is formed. According to the light emitting device for the optical data link, since the light emitting element 46 and the drive circuit 53 are connected without using a bonding wire by using the flip chip 47, the light emitting element 46 is switched at a high speed and noise is generated. It is possible to reduce. Furthermore, since the light emitting element 46 is attached by flip chip bonding, the current path from the drive circuit 53 can be increased and the high frequency characteristics can be improved.
[0021]
【The invention's effect】
According to the optical data link of the present invention, noise generated in the optical data link can be reduced by directly bonding the light emitting element to the flip chip on which the drive circuit is formed.
[Brief description of the drawings]
FIG. 1 is an exploded view of an optical data link.
FIG. 2 is a cross-sectional view of a component including a light receiving device, a light emitting device, and a substrate.
FIG. 3 is a cross-sectional view of a light receiving element.
FIG. 4 is a cross-sectional view of a light-emitting element.
FIG. 5 is an exploded view of the light emitting device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Package, 29 ... Light receiving element, 36 ... Amplifying circuit, 46 ... Light emitting element, 53 ... Drive circuit, 47 ... Flip chip 47

Claims (4)

In optical data link,
A surface-emitting light-emitting element in which an electrode on a light-emitting surface side is electrically connected to an electrode provided on a surface opposite to the light-emitting surface by a through hole, and the electrodes are collected on the surface opposite to the light-emitting surface When,
A first flip chip on which a driving circuit for driving the light emitting element is formed;
With
The light emitting element is bonded to the first flip chip such that a surface opposite to the light emitting surface of the light emitting element faces a drive circuit forming surface of the first flip chip;
An optical data link characterized by that. A back-illuminated type light receiving element in which electrodes are collected on the side opposite to the light receiving surface ;
A second flip chip on which an amplifier circuit for amplifying a signal from the light receiving element is formed ;
Further comprising
The light receiving element is bonded to the second flip chip such that a surface opposite to the light receiving surface of the light receiving element faces an amplification circuit forming surface of the second flip chip;
The optical data link according to claim 1 . A first condenser lens provided on the light emitting surface side of the light emitting element;
A second condenser lens provided on the light receiving surface side of the light receiving element;
The optical data link according to claim 2, further comprising: A back-illuminated type light receiving element in which electrodes are collected on the side opposite to the light receiving surface;
A flip chip on which an amplification circuit for amplifying a signal from the light receiving element is formed;
With
The light receiving element is bonded to the flip chip such that a surface opposite to the light receiving surface of the light receiving element is opposed to an amplifying circuit forming surface of the flip chip;
An optical data link characterized by that.

Images