CN100544141C - High-speed optoelectronic device packaging structure using microwave photonic crystal coplanar waveguide - Google Patents

Abstract

The present invention relates to the opto-electronic device manufacturing process technology field, is the use of co-planar waveguide in the high speed photoelectronic device with microwave photon structure.Use a kind of heat sink coplane microwave microstrip circuit, detection circuit backlight and temperature detection circuit made in the above, and at heat sink back side plating conductor ground level.Use the co-planar waveguide of back side ground connection on heat sink, the Terminal Design of co-planar waveguide center conductor is circular, and the ground level that the center conductor both sides are arranged extends and surrounds the circular central conductor in terminal, has formed the coplane ground level of an integral body.Co-planar waveguide of the present invention has that thermal conductivity is good, mechanical strength is high and the characteristics of low cost of manufacture.

Description

High-speed optoelectronic device packaging structure using microwave photonic crystal coplanar waveguide

technical field

The invention relates to the technical field of optoelectronic device manufacturing technology, more specifically to a high-speed optoelectronic device packaging structure using a microwave photonic crystal coplanar waveguide.

Background technique

With the increasing development of optoelectronic devices and integration technology, more and more optoelectronic devices with high performance, low cost, small form factor and low power consumption are used in optical transmission systems. When an optoelectronic device is put into system application, the structural design of its coupling package has a decisive impact on the high-frequency characteristics, reliability and service life of the device.

Encapsulate the assembled and electrically interconnected optoelectronic device chips and related functional devices and circuits into a special package, and realize optical connection with the outside through the optical system in the package. This process is called optoelectronic device packaging. craft. The post-packaging of optoelectronic devices is a very important process. It is not only related to the stability and reliability of the device, but also different shell structures and packaging forms will affect the performance parameters of the device.

With the development of technology, the packaging structure is tending towards miniaturization and multi-functional modularization. Due to the large internal space of the butterfly package, semiconductor refrigerators and thermistors are usually installed, and some microwave microstrip circuits can be placed. Through semiconductor refrigerators and thermistors, combined with external control circuits, it is possible to ensure that semiconductor chips (such as lasers, detectors, modulators, etc.) work at a constant operating temperature. The microwave microstrip circuit plays an obvious role in reducing the impact of packaging on the high-frequency response characteristics of semiconductor optoelectronic devices. In the structural design of high-speed optoelectronic devices, microstrip lines are commonly used high-speed signal transmission lines. However, the loss of the microstrip line is an important factor affecting the final high-frequency performance of the device. Excessive loss will reduce the amplitude of high-frequency signals, and ultimately affect the high-frequency response characteristics of the device. At the same time, the frequency dependence of the loss causes distortions in the signal transmitted in the microstrip.

There are two possible reasons for the loss of the microstrip line at higher frequencies. One is that the performance of the conductor material and the dielectric itself deteriorates when the frequency is higher, and the loss tangent increases with the increase of frequency; the other is radiation loss. and surface wave transmission. When the frequency exceeds 10 GHz, these two losses become very significant, especially for materials with relatively large relative permittivity such as Al ₂ O ₃ and AlN. In addition, radiation and surface waves can cause parasitic coupling between microstrip lines and other circuits, degrading electromagnetic compatibility (EMC) performance. Generally, there are two ways to suppress electromagnetic radiation. 1) Materials with high dielectric constant can be selected to keep the electromagnetic field confined in the medium as much as possible. But the dielectric loss caused by this design is also very large. 2) Setting the ground plane on both sides of the microstrip line can greatly reduce the radiation of electromagnetic waves. This structure is a coplanar waveguide (CPW). Usually, the dielectric substrate of this waveguide is covered with a conductor to form a coplanar waveguide with the back grounded ( CB-CPW). Compared with traditional CPW, backside grounding has low characteristic impedance and heat sink characteristics and can improve the mechanical strength of the substrate. However, such a microstrip line creates a parallel-plate leakage mode between the top and bottom ground planes, and it exists over the entire frequency range. This structure will form a resonant absorption peak at a specific frequency point of the transmission parameter _S21 . As the frequency increases, this phenomenon will become more and more serious, and at the same time, the generation of surface waves will be enhanced. It partially leaks the energy transmitted along the center conductor of the microstrip to the ground.

As the frequency of current optoelectronic devices is getting higher and higher, for example, the highest bandwidth of semiconductor lasers has exceeded 20 GHz, and the bandwidth of photodetectors and semiconductor modulators has exceeded 40 GHz. In order to improve the overall performance and reduce the cost of optoelectronic devices, today's high-speed optoelectronic device packaging urgently needs to be different from traditional design methods and new manufacturing processes and technologies.

Contents of the invention

In order to solve the problem of the energy leakage of the back-grounded coplanar waveguide due to the existence of parallel plate modes, the purpose of the present invention is to provide a new transmission line structure, that is, the back-grounded coplanar waveguide, which has a compact periodic photonic crystal structure It is etched on the top ground plane, and the photonic crystal has a stop band effect in a certain frequency range, which can effectively suppress the generation of parallel plate modes, prevent energy from leaking to the ground plane, and thus reduce the signal frequency in a certain frequency range. transmission loss. The electromagnetic characteristics of this periodic structure can be expressed by lumped circuit units (capacitors or inductors). Through the coupling effect of periodically arranged inductors and capacitors, a stop band will be generated, whose center frequency is determined by the period of the photonic crystal. The width and depth of the band are determined by the structure size of the periodic unit, and the band edge at the cutoff frequency is very steep. When the width of the stop band is designed larger, the behavior of this two-dimensional periodic photonic crystal has the function of a low-pass filter. When the high-frequency signal is transmitted from the coplanar microstrip, due to the stop band effect of the photonic crystal, the parallel plate mode between the ground planes is suppressed, so that the transmitted energy will not leak to the ground plane through the parallel plate mode.

The technical solution adopted by the present invention to solve the technical problem is: in the high-speed optoelectronic device package (such as the butterfly package exemplified in the present invention), the coplanar waveguide with the back grounded is used to transmit high-frequency signals. The characteristics of this waveguide are: 1) The coplanar waveguide with the back grounded is made on the whole heat sink; 2) The dielectric material of the coplanar waveguide and the heat sink is AlN, and the conductor ground plane is laid on the back of the heat sink; 3) The dielectric material Above, the terminal of the waveguide center conductor is designed to be circular, and the ground plane arranged on both sides of the center conductor extends at the terminal and surrounds the circular center conductor, forming an overall coplanar ground plane; 4) Etching on the ground plane at the top of the waveguide There is a periodic microwave photonic crystal unit structure.

The present invention proposes a high-speed optoelectronic device packaging structure using microwave photonic crystal coplanar waveguide. The packaging structure includes:

a heat sink; a coplanar microwave microstrip circuit fabricated on the front of the heat sink; and a conductor ground plane plated on the back of the heat sink to form a coplanar waveguide with the back grounded;

It also includes a backlight detection circuit and a temperature detection circuit fabricated on the front of the heat sink;

The terminal of the central conductor of the coplanar microwave microstrip circuit is designed to be circular, and the ground plane arranged on both sides of the central conductor extends at the terminal and surrounds the circular central conductor, forming an overall coplanar ground plane; Periodic microwave photonic crystal structural units are etched on the ground plane arranged on both sides of the conductor to form a two-dimensional periodic metal microwave photonic crystal ground plane;

The packaging structure also includes a semiconductor chip, the anode of the semiconductor chip is in contact with the circular center conductor through a rectangular conductor block, and the cathode of the semiconductor chip is soldered to the ground plane on both sides of the center conductor through gold wire.

The beneficial effects of the present invention are: 1) the use of the coplanar waveguide whose back is grounded can effectively reduce the outward electromagnetic radiation of high-frequency signals; 2) the semiconductor chip is placed on the circular center conductor of the coplanar waveguide through a rectangular conductor block, The other pole of the chip is connected to the coplanar ground plane through a gold wire. This design can reduce the number of gold wires used, thus weakening the influence of gold wire inductance on the frequency response of the device. 3) Since the central conductor and the chip on it are surrounded by the ground plane etched with microwave photonic crystals, this design can suppress the parallel plate leakage mode generated on the coplanar transmission line with the back grounded. At the same time, the transmission loss can be reduced and the integrity of the signal can be guaranteed by suppressing the leakage mode. 4) This coplanar waveguide has the characteristics of good thermal conductivity, high mechanical strength and low manufacturing cost, and it is easy to achieve 50Ω characteristic impedance through reasonable size design.

Description of drawings

In order to further illustrate the technical content of the present invention, the present invention will be further described below in conjunction with accompanying drawing and embodiment, wherein:

Figure 1 is a detailed view of one of the two-dimensional photonic crystal structural units

Fig. 2 is a top view of a coplanar waveguide with a ground plane etched two-dimensional periodic photonic crystal structure.

Fig. 3 is a front view and a cross-sectional view along A-A direction of a heat sink in a butterfly package device.

Figure 4 is a diagram of the internal structure of a high-speed optoelectronic device packaged in a butterfly shape.

Detailed ways

The manufacturing process of the back-grounded coplanar waveguide with photonic crystal structure is completely the same as that of the traditional back-grounded coplanar waveguide. Please refer to attached picture.

In the embodiments shown in FIG. 1 , FIG. 2 , FIG. 3 , and FIG. 4 , the material of the heat sink 11 is selected to be AlN. Using electroless plating technology, the temperature detection circuit 1 and the backlight detection circuit 3 made of Cu are plated on the top surface of the heat sink, and the center conductor 9 and the ground plane 8 of the coplanar microwave microstrip circuit 4 are plated; Block conductor ground plane 5. Then, the photonic crystal unit is selected according to the electromagnetic field mode that needs to be cut off, just like one of the structural shapes shown in FIG. 1 . The periodic photonic crystal structure 8 is etched on the top ground plane of the coplanar waveguide through exposure, development and etching processes. Applying the heat sink 11 with the coplanar transmission line structure 4 to the optoelectronic device in the butterfly package, all the microstrip circuits are connected to the pins 13 of the butterfly shell 16 through gold wires 14 . The semiconductor chip 2 is placed on the circular center conductor of the coplanar waveguide through a rectangular conductor block, and is connected to the ground plane 8 through the gold wire 14 . At the same time, a matching resistor 7 is set on the coplanar microstrip circuit 4 to match the input impedance, and an inductor 12 is placed in the DC path to function as an AC isolation. The entire heat sink is placed on a semiconductor refrigerator 15 to keep the internal temperature of the device constant.

Claims (1)

1, a kind of high speed photoelectronic device encapsulation structure of applying microwave photonic crystal co-planar waveguide, this encapsulating structure comprises:

Heat sink; Be produced on the coplane microwave microstrip circuit in this heat sink front; And plating is at the conductor ground level at this heat sink back side, thereby forms the co-planar waveguide of back side ground connection;

Also comprise the detection circuit backlight and the temperature detection circuit that are produced on this heat sink front;

It is characterized in that,

The Terminal Design of the center conductor of described coplane microwave microstrip circuit is circular, and the ground level of arranging in the center conductor both sides extends and encirclement circular central conductor in terminal, has formed the coplane ground level of an integral body; By etching periodicity microwave photon construction unit on the ground level of arranging in the center conductor both sides, form two-dimensional and periodic metallic microwave photonic crystal ground level;

This encapsulating structure also comprises the semiconductor chip, and the positive pole of described semiconductor chip contacts with the circular central conductor by a rectangular conductor piece, and the negative pole of semiconductor chip is welded on the ground level of center conductor both sides by spun gold.

Images