JPH0364956A - High speed signal processing circuit module - Google Patents

Abstract

PURPOSE:To eliminate signal cross talk, oscillations, or the like so as to improve a high speed signal processing circuit of this design in high speed characteristics by a method wherein a high speed signal line is sandwiched between earth layers to be formed into a triplate strip line structure and made small enough in lead inductance. CONSTITUTION:First boards 20 formed of an Si based material whose front and rear side are plated with Au and ceramics of low dielectric constant are laminated in multilayer, high speed signal lines 29 are sandwiched between earth layers 27 and 28 to be formed into a triplate strip line structure, a second board 25, which is provided with LSI inserting holes, bonding pads, and signal external terminals and whose front and rear side are plated with gold, and a third board 35, which is formed of an Si base material whose front and rear side are plated with Au and provided with LSI inserting holes, are joined together in this sequence. LSI chips 41 are mounted on the first board 20 through the holes provided to the second and the third board, 25 and 35, and then the holes of the third board 35 are hermetically sealed up with lid members 43.

Description

[Detailed Description of the Invention] Overview Regarding high-speed signal processing circuit modules, by using the base material itself as a package, there is no signal crosstalk, oscillation, etc., the signal line glue inductance is sufficiently small, and the module has excellent high-speed characteristics. Aiming to provide a high-speed signal processing circuit module, this module is formed by laminating a first substrate with Au plating on the back side of a Si-based substrate and a low dielectric constant ceramic in multiple layers, and connects a high-speed signal line to a ground layer. A second substrate is sandwiched between two substrates to form a tri-plate stripline configuration, and has a hole for LSI insertion, bonding pads, and signal terminals to the outside, and is plated with gold on both the front and back sides, and a Si substrate on both front and back sides. A third substrate with a hole for LSI insertion is bonded in this order, and the LSI chip is attached to the second substrate with Au plating.
The third substrate is mounted on the first substrate through a hole formed in the third substrate, and then the hole in the third substrate is hermetically sealed with a lid member.

INDUSTRIAL APPLICATION FIELD The present invention relates to a high-speed signal processing circuit module used in optical repeaters and the like.

In recent years, extremely wide-band single-mode optical fibers have come to be used as transmission lines, and the scope of application of high-speed transmission systems is being greatly expanded.

In today's optical communications, 1.6 Gb/s systems are used in trunk systems, and it is expected that the speed will further increase in the future. LSIs that are essential for various circuits in systems are available for several Gb/s, and optimization of high-speed signal processing circuit modules is being sought to bring out the full performance of such LSIs. There is.

Conventional technology Optical/electrical converters and electrical/optical converters used in optical communication devices are conventionally fabricated on substrates with a low dielectric constant, such as ceramic substrates, in order to prevent signal crosstalk, oscillation, etc., and reliably convert high-speed signals. A signal path is formed using a strip line, and after mounting the LSI chip on the board, the circuit board is inserted into the metal package. War, Iada, and 2 Tsuyu were airtightly sealed to maintain electromagnetic shielding characteristics, a sufficiently small size, a high-speed signal processing circuit with excellent high-speed characteristics, and heat dissipation characteristics.
It is to provide modules.

Problems to be Solved by the Invention However, although the high-speed signal processing circuit module with the above-mentioned configuration was capable of signal processing of 2 to 3 Gb/s or less, it was only possible to process signals at 1OGb/s, which is the most advanced field of optical communication technology.
In the signal processing of S, signal leakage occurs at the strip line section, signal reflection at the junction section, etc., and high-speed characteristics are not sufficient. Therefore, it is conceivable to make the board structure multi-layered and to configure the circuit module with a tri-plate stripline configuration, but in a structure that uses a metal package, which is an extension of the conventional technology, both the shielding structure and the grounding structure become complicated, and the module Prices are expected to rise significantly.

The present invention has been made in view of these points, and its purpose is to provide a means for solving the problem of signal crosstalk by using the base material itself as a package. It is formed by laminating a first substrate plated with Au and a low dielectric constant ceramic in multiple layers, and a high-speed signal line is sandwiched between a ground layer to form a triplate strip line configuration, and holes for LSI insertion, bonding pads, and A second board that has a signal terminal to the outside and is gold-plated on both the front and back sides, and a third board that has a Si base material that is Au-plated on both the front and back sides and has a hole for LSI insertion are formed in this order. Join. After the LSI chip is mounted on the first substrate through the holes formed in the second and third substrates, the hole in the third substrate is hermetically sealed with a lid member.

Function: In the high-speed signal processing circuit module of the present invention, the high-speed signal line is sandwiched between the ground layers to form a triplate strip line configuration, and the signal line inductance can be made sufficiently small, so that signal crosstalk, It is possible to provide a circuit module that is free from oscillation and has excellent high-speed characteristics. Furthermore, unlike the conventional configuration using a metal package, the base material itself serves as a package, making it possible to achieve significant economicalization of the circuit module.

Furthermore, since the heat generated by the LSI is dissipated directly into the Si base material, the heat dissipation performance is very high, and since the LSI is mounted on the first substrate made of the same material, Si, the difference in coefficient of thermal expansion There is no stress generation in the LSI chip and joints, and it is expected that the reliability of the joints will be improved.

Example Embodiments of the present invention will be described in detail below based on the drawings.

First, number 31! 1, a schematic block diagram of an optical repeater suitable for applying the present invention is shown. The optical repeater is composed of an ○/E module 1 and an E/○ module 2, which converts the optical signal from the input optical fiber 3 into an electrical signal, amplifies and regenerates it, and then converts it further into an optical signal and sends it to the output side. It is designed to be sent to an optical fiber 9.

The O/E module 1 is composed of an avalanche photodiode (hereinafter referred to as APD) 4 that converts an optical signal into an electrical signal and a high-speed signal processing circuit module 5. The high-speed signal processing circuit module 5 includes an equalization amplifier circuit 6 that shapes and amplifies a distorted received waveform, a timing extraction circuit 7 that reproduces a clock signal from the received pulse code sequence, and a timing extraction circuit 7 that reproduces a clock signal from the received pulse code sequence. It includes an identification/reproduction circuit 8 that identifies the presence or absence of a pulse after equalization amplification and outputs a pulse waveform.

The E/○ module 2 includes a semiconductor laser (LD) 10,
It includes an LD drive circuit 11 that drives this semiconductor laser. The output of the identification and reproducing circuit 8 is input to the LD drive circuit 11, which drives the LDIO, converts the electrical signal into an optical signal, and sends it to the output side optical fiber 9.

Optical repeaters having the above-mentioned functions are inserted into a transmission path at predetermined intervals to achieve long-distance, high-speed transmission of optical signals, and it is expected that the transmission speed will become even faster in the future. Therefore, in response to such an increase in speed, the high-speed signal processing circuit module 5 is also required to be increased in speed.

Hereinafter, a high-speed signal processing circuit module according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2 and FIGS. 4 to 6. First, referring to Figure 4, the first
A perspective view of substrate 20 is shown. In order to efficiently dissipate the heat of the LSI pair chip (hereinafter referred to as LSI chip) to be mounted, and to avoid bonding defects due to the difference in thermal expansion coefficient between the LSI chip and the substrate, the first A substrate made of Si was used as the substrate 20. In FIG. 4, 21 is a Si base material,
First, if the back side of the LSI chip is used as a power source (for example, -5V), it is necessary to insulate it from the ground, so first, the part where the LSI chip is mounted is heated by thermally oxidizing Si or is coated with a SiO2 film. A 5 in 2 insulating film 22 is formed by evaporating or the like. This insulating film 2
Insulating film 22 may be formed on the entire surface of Si base material 21, and then unnecessary portions may be removed by etching, or the insulating film 22 may be formed only on desired portions using a mask. In this embodiment, three insulating films 22 are provided corresponding to the LSI chip for the equalization amplifier circuit, the LSI chip for the timing extraction circuit, and the LSI chip for the identification reproducing circuit.

Next, NiCr+Au or Ta+NiCr+Au is formed on both the front and back surfaces of the Si base material 21 by vapor deposition or sputtering, and further Au plating is applied to form the conductive layer 23. Furthermore, the conductive layer on the outer periphery of the insulating film 22 is removed by etching to form a conductive LSI chip mounting part 24, so that the conductive layer 23 and the LSI chip mounting part 24 are insulated. If the back side of the LSI chip is used as a ground, there is no need to insulate the LSI mounting part, and the S
The conductive layer 23 may be formed on the entire surface of the i-base material 21.

Referring now to FIG. 5, a perspective view of a second substrate for high speed signal transmission is shown. As the wiring material for the high-speed signal line, four layers of low dielectric constant glass ceramic (dielectric constant ε=4) with a thermal expansion coefficient of 4×10-'/l are used.

The thermal expansion coefficient of this low dielectric constant glass ceramic is approximately equal to that of an LSI chip formed from Si.

While forming a Cu earth layer 27 between the first layer 26 and the second layer 262 of the low dielectric constant glass ceramic base material,
Third layer 263 and fourth layer 26. A ground layer 28 is also formed between them. and a second layer 2 of low dielectric constant glass ceramic.
A plurality of high-speed signal lines 29 are formed on the surface of 62, and the high-speed signal line 29 is sandwiched between a pair of ground layers 27 and 28 to form a triplate strip line configuration. An input terminal 32 and an output terminal 33 are connected to the high-speed signal line 29.

The second board 25 is provided with three holes 30 for inserting LSI chips, and the stepped portion of each hole 30 is connected with bonding wires to a high-speed signal line 29, a power supply line (not shown), a ground line, etc. A bonding pad 31 is formed. Further, both the front and back surfaces of the second substrate 250 are plated with Au to perform conductive treatment.

Referring now to FIG. 6, a perspective view of the third substrate 35 bonded onto the second substrate 25 is shown.

36 is a Si base material, on both the front and back sides of which N i Cr + A V or T a + N is applied like the first substrate 20.
A conductive layer 37 is formed by depositing or sputtering i Cr+Au and further plating with Au.

Three holes 38 are further formed in the third substrate 35 at positions corresponding to the holes 30 in the second substrate 25.

The high-speed signal processing circuit module of this embodiment has a first circuit configured as described above. The substrate 20, the second substrate 25, and the third substrate 35 are bonded together as follows. That is, the first
As shown in the figure, the second substrate 25 is bonded to the first substrate 20 by brazing with an AuSn brazing material. Further, a third substrate 35 is soldered onto the second substrate 25 using the same <AuSn brazing material.

In FIG. 1, 39.40 indicates a bonding layer formed by brazing. Other brazing materials used for joining include Au
Au eutectic alloys such as Si can be used. After the first substrate 20, second substrate 25, and third substrate 35 are bonded in this way, the holes 3 formed in the second substrate 25 and the third substrate 35 are
0.38, the LSI chip 41 is bonded onto the LSI mounting portion 24 of the first substrate 20 using an AuSn brazing material. In this case, the back surface of the LSI chip 41 is previously metallized with Au.

After mounting the LSI chip 41 in this way, a second
A bonding wire 42 is connected to the pad portion 31 on the substrate 25.
Connect by bonding. Next, a lid member 43 made of Kovar is soldered using an AuSn brazing material so as to close the hole 30 of the third substrate 35, and the LSI chip 41 is hermetically sealed. In FIG. 1, 44 indicates a bonding layer. The lid member 43 may be joined by soldering instead of brazing. FIG. 2 shows a perspective view of this embodiment configured in this manner. Note that the lid member 4
3 is shown by an imaginary line.

Effects of the Invention As described in detail above, the present invention has a tri-plate strip line structure in which a high-speed signal line is sandwiched between ground layers, and the bonding wire can be formed sufficiently short, so that there is no signal crosstalk, oscillation, etc. This has the effect of providing a circuit module with sufficiently small inductance and excellent high-speed characteristics.

In addition, the heat generated by the LSI chip is handled by S, which has relatively good heat transfer and conductivity.
Since the heat dissipates directly to the first substrate formed from the
Since the LSI chip is mounted on the first substrate formed from the above, there is no stress generated in the LSI chip and the bonding portion due to differences in thermal expansion coefficients, and bonding reliability can be improved. Furthermore, unlike the conventional module structure using a metal package, the circuit module can be made significantly more economical by giving the board itself the role of the package.

[Brief explanation of drawings]

Fig. 1 is a sectional view of an embodiment of the present invention, Fig. 2 is a perspective view of an embodiment, Fig. 3 is a schematic block diagram of an optical repeater suitable for applying the present invention, and Fig. 4 is a perspective view of the first board. FIG. 5 is a perspective view of the second board, and FIG. 6 is a perspective view of the third board. 0... First substrate, 2... Insulating film, 5... Second substrate, 9... High speed signal line 6... Si base material, 3... Lid member. 1... Si base material, 4... LSI mounting part, 7.28... Earth layer, 5... Third board, 1... LSI chip, 20: #1 base 22: Kikyuu Fiber 25: 2nd millet silver 35: 3rd mill 41: LSI nap 43: Kawabe jJ 20 $1 unit j & inspection eye Fig. 4

Claims (4)

[Claims] (1) Au plating (23
), and a low dielectric constant ceramic is laminated in multiple layers, and a high-speed signal line (29) is sandwiched between ground layers (27, 28) to form a tri-plate strip line configuration. Along with the LSI insertion hole (30) and bonding pad (
31) and external signal terminals (32, 33), a second substrate (25) with gold plating on both the front and back sides, and a Si base material (36) with Au plating (37) on both the front and back sides. The third board (3) has a hole (38) for LSI insertion.
5) in this order, and the LSI chip (41) is attached to the second and third substrates (25,
35) through the holes (30, 38) formed in the first
A high-speed signal processing circuit module, characterized in that, after being mounted on the substrate (20), the hole (38) of the third substrate (35) is hermetically sealed with a lid member (43). (2) LSI mounting part (24) of the first board (20)
After forming an insulating film (22) on the surface, gold plating (23) is applied.
2. The high-speed signal processing circuit module according to claim 1, wherein the Au on the outer periphery of the LSI mounting portion (24) is removed by etching. (3) Before applying Au plating to both the front and back surfaces of the first and third substrates (20, 35), a NiCr layer and an Au layer or a Ta layer, a NiCr layer and an Au layer are formed on the Si base material (21, 36).
3. The high-speed signal processing circuit module according to claim 1, wherein a layer is formed. (4) The low dielectric constant ceramic is a glass ceramic, and the first, second and third substrates (20, 25, 35
2. The high-speed signal processing circuit module according to claim 1, wherein the bonding in ) is brazing with an Au eutectic alloy.