JPH09148489A - Ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit capable of raising high frequency property by reducing the mutual capacity between signal paths, and enabling crosstalk or reflection noise to be reduced even in the case of having transmitted high frequency signal to about 2GHz in clock frequency. SOLUTION: In a ceramic circuit board where a plurality of conductor electrodes 3 to connect with a circuit layer are made on the surface of itself having the circuit layer, isolation wiring 4 is made around each conductor electrode 3. Moreover, the isolation wiring 4 is any one of earth wiring, power wiring, and floating wiring. Furthermore, a short circuit line 5 is made, which electrically connects the conductor electrode 3 with the isolation wiring 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic circuit board, and more particularly to a ceramic circuit board capable of reducing mutual capacitance between signal lines to reduce crosstalk noise and reflection noise and improving high frequency characteristics.

[0002]

2. Description of the Related Art For ceramic substrates such as Al ₂ O ₃
Ceramic circuit boards in which a wiring layer for signal processing and a conductor electrode portion are integrally formed are widely used as components of various electronic devices. In particular, it is an electronic device that handles high-speed signals of 100 MHz clock or more and high-frequency signals of 300 MHz or more, and is faster as a control device for computers, mobile communication, game machines, image processing devices, machine tool control devices, and various industrial equipment. There is a demand for ceramic circuit boards and semiconductor packages that are compatible with the increasing demands for high performance.

In recent years, as the demand for high-density mounting of semiconductor components and ICs has increased, multi-layer ceramic circuit boards having a structure capable of increasing the circuit density per unit area of the board have been widely used. . This multilayer ceramic circuit board is generally manufactured by the following steps. That is, a ceramic raw material powder is formed into a thin sheet by a sheet forming method, a conductive through hole, a predetermined circuit pattern and a conductor electrode portion are screen-printed on the surface of the sheet-shaped formed body, and the obtained printed bodies are laminated in multiple stages. A method is employed in which a laminated body is formed by thermocompression bonding, the laminated body is sintered, and then the surface circuit layer and the conductor electrode portion are electroplated.

That is, as shown in FIG. 2, a plurality of circular conductor electrode portions (lands) 3 are independently formed on the surface of a ceramic substrate 1 having a circuit layer 2 such as signal wiring. Further, connecting portions such as pins, solder balls, and lands are formed on the conductor electrode portions, and P and P are respectively formed.
GA (pin grid array) type, BGA (ball grid array) type, and LGA (land grid array) type semiconductor packages are respectively formed.

In the above-mentioned conventional multilayer ceramic circuit board, in order to perform electroplating, a lead wire for exclusive use of plating is previously arranged in the inner layer. That is, when printing a circuit pattern at the stage of a sheet-shaped molded product, a lead wire for exclusive use of plating is also formed by printing at the same time. In order to electrically short-circuit the cross-sections of the lead wires with each other, a conductor is solidly printed on the side surfaces to form side surface electrodes, and then they are collectively fired. After firing, the short-circuited side surface electrode portion is energized to perform electroplating. Then, after the electroplating is completed, the short-circuiting side surface electrode portion is removed by grinding to complete the multilayer ceramic circuit board as the package body.

[0006]

However, in the structure of the above-mentioned conventional ceramic circuit board, the conductor electrode portion is the portion having the largest self capacitance and mutual capacitance among various signal wirings. That is, the mutual capacitance of the conductor electrode portion on the substrate surface has a large value obtained by adding the mutual capacitance caused by the ceramic substrate surface and the internal circuit wiring layer and the mutual capacitance formed in the electric field space near the electrodes.

Therefore, when trying to transmit a high frequency signal, there is a problem in that crosstalk is likely to occur between the conductor electrode portions and the operational reliability of the circuit is deteriorated. Therefore, high frequency signals and high speed signals are processed. There was a problem that became difficult. By the way, the upper limit frequency of the transmission signal in the ceramics circuit board having the conventional structure is limited by the limit of occurrence of crosstalk between the conductor electrode portions and between the signal lines, and is usually 5 GHz. When this value is converted into a clock frequency, it is a low value of about 1/5 of 1 GHz, and in any case, it was difficult to improve the high frequency characteristics.

On the other hand, in order to improve the high frequency characteristics,
For example, as shown in FIG. 2, by arranging a signal / ground (SIG / GND) twisted pair wire in the conductor electrode portion 3, a structure in which the electric field on the substrate surface is confined by two wires is also adopted. However, in the structure in which the SIG / GND twisted pair wiring is provided, there is a problem that the layout of the electrode portion and the wiring are complicated, and the degree of freedom in design is significantly reduced.

Further, in the ceramic circuit board for forming the lead-out line for plating, the steps of printing the side electrode for electrical short-circuiting, grinding the side electrode after electroplating, etc. are increased, and the manufacturing efficiency of the circuit board is lowered. In addition, there is a problem that there is much waste from the viewpoint of effective use of materials. In addition, since the lead wire for plating disposed on the board is electrically open at the tip and acts as a so-called open branch, the self capacity of the circuit board increases, the mutual capacitance increases, the mutual inductance increases,
Variation of characteristic impedance due to spatial position, weight increase,
There are various problems such as an increase in the amount of expensive tungsten paste used, and in any case, there is a problem that the manufacturing cost increases and it becomes difficult to process high frequency signals and high speed signals.

The present invention has been made to solve the above-mentioned problems, and crosstalk is reduced even when a high frequency signal having a clock frequency of up to about 2 GHz is transmitted by reducing the mutual capacitance between signal lines. An object of the present invention is to provide a ceramics circuit board that can reduce noise and reflection noise and can improve high frequency characteristics.

[0011]

In order to achieve the above object, a ceramic circuit board according to the present invention is a ceramic circuit board in which a plurality of conductor electrode portions connected to the circuit layer are formed on the surface of the ceramic substrate having a circuit layer. At
An isolation wiring is formed around each of the conductor electrode portions.

Further, the isolation wiring is any one of a ground wiring, a power supply wiring and a floating wiring. Further, it is preferable to form a short-circuit line that electrically connects the conductor electrode portion and the isolation wiring.

The type of ceramic substrate used in the above ceramic circuit substrate is not particularly limited, but in addition to oxide ceramics such as alumina (Al ₂ O ₃ ), it has high thermal conductivity and is for high output. It is also possible to use non-oxide ceramics such as aluminum nitride (AlN) or high-strength silicon nitride (Si ₃ N ₄ ) suitable as a substrate.

A ceramics circuit board having a multilayer wiring structure having a circuit layer, a plurality of conductor electrode portions and isolation wirings on the surface of the ceramics substrate is manufactured by the following sheet-shaped compact (green sheet) laminating method. That is, a raw material slurry prepared by dispersing a ceramic raw material powder such as AlN or Si ₃ N _{4 in} an organic binder or a solvent together with a sintering aid is formed into a thin sheet-like compact by a sheet forming method such as a doctor blade method. Then, the obtained sheet-shaped molded product is punched into a predetermined size, and a plurality of sheets are obtained after the conductive through holes are punched and the predetermined circuit wiring pattern, the conductor electrode portion and the isolation wiring are screen-printed. -Shaped compacts are stacked in multiple stages and heat-pressed or pressure-bonded, or a solvent or adhesive is applied and laminated to form a laminate (multilayer ceramics compact), and this laminate is sintered to produce. The method of doing can be adopted. In particular, aluminum nitride (A
In the case of using 1N), it has both its unique high thermal conductivity and high insulating property, and a ceramic circuit board having a multilayer wiring structure excellent in heat dissipation and insulation strength is obtained as a substrate for mounting a semiconductor element. To be

As described above, by forming the isolation wiring such as the ground wiring, the power supply wiring, and the floating wiring around the conductor electrode portion, the electrical isolation action is substantially provided between the adjacent conductor electrode portions. It is possible to demonstrate. The isolation wiring that surrounds the conductor electrode portion does not need to completely surround the conductor electrode portion spatially, and it suffices to form the isolation wiring in a necessary minimum range that substantially provides an isolation action.

By forming the isolation wiring around the conductor electrode portion, the mutual capacitance on the surface and inside of the ceramic substrate becomes anti-ground capacitance, and the mutual capacitance remaining between the conductor electrode portions is an extremely small value only in space capacitance. As a result, mutual interference of signals between the conductor electrode portions is reduced.

Further, as shown in FIG. 1, by forming a short-circuit wire 5 for electrically connecting the isolation wire 4 and the conductor electrode portion 3, the isolation wire 4 and the short-circuit wire 5 are electrically connected to each other. The ceramic circuit board can be used as a conductive wire for plating and does not require a lead wire for electroplating. That is, a short-circuit line that electrically connects the conductor electrode portion arranged on the surface of the ceramic substrate and the isolation wiring is formed in advance. The short-circuit line is printed at the same time when the circuit wiring pattern and the conductor electrode portion are screen-printed, and becomes a solidified state by the firing operation. Next, with respect to the substrate material on which the short-circuit line is formed, the short-circuit line and the isolation wiring are used as conductive lines, and on the wiring layer and the conductor electrode portion surface,
A plating layer having a thickness of about 0.1 to 5 μm and made of Ni, Au, or the like is formed by electroplating. After that, with respect to the substrate material having the plating layer of the predetermined thickness formed on the surface layer,
All short-circuit lines are removed by blasting or etching.

A semiconductor element is mounted on the ceramic circuit board to form a semiconductor package or a semiconductor package. In addition, a printed wiring board, a metal board, and another ceramics board are joined to the circuit board to obtain various mounts.

According to the ceramic circuit board having the above-mentioned structure, since the isolation wiring is formed around the conductor electrode portion, the mutual capacitance on the surface and inside of the ceramic substrate becomes a capacitance to ground, and between the conductor electrode portions. Since the remaining mutual capacity is an extremely small value with only space capacity,
As a result, mutual interference of signals between the conductor electrode portions is reduced. Therefore, even when a high frequency signal is transmitted, crosstalk is unlikely to occur and a ceramic circuit board having excellent operation reliability can be obtained.

Further, by forming a short-circuit line for electrically connecting the isolation wiring and the conductor electrode portion, electroplating can be performed by using the short-circuit line as a conduction line without disposing a lead wire exclusively for plating. Can be given. In addition, since no lead wire for exclusive use of plating is provided, there is little interference even when high-speed signals or high-frequency signals are processed,
A ceramic circuit board having excellent operation reliability can be obtained.

Further, since the arrangement structure of the SIG / GND twisted pair wires, etc., which has been indispensable for improving the high frequency characteristic in the past, is unnecessary, the layout of the electrode portion and the wiring pattern are simplified, and the wiring design of the circuit board is simplified. The degree of freedom can be greatly improved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings.

As a starting material, high purity aluminum nitride (Al) having a purity of 99.99% or more and 0.8 μm is used.
N) To the powder, 3 wt% of yttrium oxide Y ₂ O ₃ as a sintering aid and 0.5 wt% of polyoxyethylene alkyl ether phosphoric acid as a surfactant were added, and toluene was added. Wet mixing was carried out for 24 hours in a ball mill in a mixed solvent with ethanol. Further, 12% by weight of an acrylic resin as an organic binder was added and mixed by a ball mill to prepare a raw material slurry. The slurry was used to form a sheet by the doctor blade method to produce a large number of sheet-shaped formed bodies. The thickness of the sheet-shaped compact is 40
The outer diameter was 0 μm, and the outer diameter was 30 cm × 30 cm.

On the other hand, for tungsten (W) powder having an average particle size of 3 μm, 2 parts of AlN powder as a co-dough component are used.
A coating composition (conductor paste) was prepared by adding 0% by volume and further kneading and kneading well-known binders, solvents and the like.

Next, using the above-mentioned conductor paste, a signal wiring,
Predetermined circuit pattern including power supply wiring and ground wiring, 324
A short-circuit line was printed so that all the conductor electrode parts, isolation wiring, and conductor electrode parts were connected.

Here, the conductor electrode portion has a diameter of 0.70 mm.
Since they were circular and arranged at a pitch of 1.00 mm, the shortest distance between adjacent conductor electrode portions was set to 0.30 mm. And
As shown in Table 1, the narrowest line width between the narrowest electrodes is 0.
Isolation wiring having a thickness of 04 mm (Example 1) to 0.10 mm (Example 4) was formed. This isolation wiring was formed in such a shape that each conductor electrode portion was wrapped in a substantially rhombic shape. Therefore, the gap between each isolation wiring and the conductor electrode portion is 0.130 mm (Example 1) to 0.
It was set to 10 mm (Example 4). Further, the lead wire exclusively for plating, which was conventionally required, was not formed.

Next, a plurality of sheet-shaped compacts having various wiring patterns printed thereon are laminated and 100 kg / cm ² at a temperature of 70 ° C.
It was pressed for 30 minutes while applying the pressure force of (3) to form a laminate. Before the laminating operation, the conductor electrode portion was printed and formed in a shape that was raised by about 30 μm from the periphery when dried at 60 ° C. for 15 minutes.
The conductor electrode portion (land) on the surface was pressed into the ceramic sheet and the surface was completely smoothed.

Next, the laminated body was cut into a dimension value close to the intended package outer dimension. Further, each cut laminate was degreased for 2 hours at 700 ° C. in a nitrogen gas atmosphere. Further, each degreased laminate was fired in the same nitrogen gas atmosphere at a temperature of 1850 ° C. for 5 hours to give an outer dimension of 25.4.
An aluminum nitride multilayer circuit board having a size of 25.4 x 2 mm was prepared.

FIG. 1 is a perspective view partially showing a surface layer portion of the aluminum nitride multilayer circuit board. 324 conductor electrode portions (lands) 3 are formed on the surface of the AlN multilayer substrate as the ceramic substrate 1, and each conductor electrode portion 3 is surrounded by the isolation wiring 4 and a short-circuit line for short circuit. 5 is electrically connected. Among the above 324 conductor electrode parts 3, there were three floating electrodes that had no electrical connection with other circuits, but the floating wires connected to these floating wires were from the inner layer via via holes. It was exposed to the surface layer of the substrate, exposed, and connected to the ground electrode.

After that, one of the electrically conductive conductor electrodes is made a negative electrode, while platinum is made a positive electrode, and electroplating is carried out to obtain a thickness of 4 μm on the surface circuit layer and the conductor electrode. Ni plating layer was formed. Further, the substrate material on which the Ni plating layer and the isolation wiring are formed is heat-treated in a nitrogen gas atmosphere at a temperature of 700 ° C. for 5 minutes, and then a gold (Au) plating layer having a thickness of 1.5 μm or more is formed by an electroplating method. did. In this case, the usual method of contacting the contact with the conductor electrode was adopted as the energizing method.
The thickness of each plating layer was measured by the fluorescent X-ray method.

Next, the circuit board on which the plated layer was formed was subjected to a wet sandblasting device to remove the short-circuit wire for short circuit.

Next, a semiconductor element (chip) is bonded and mounted on the surface of the AlN circuit board through an Ag-containing conductive polyimide paste, and each terminal of the semiconductor element and a terminal of the circuit layer are wire-bonded to form a semiconductor. Packaged. Further, solder paste is printed on the surface of the 324 conductor electrode portions (lands) 2 on which the Ni / Au plated layer is formed,
Place a 0.70 mm diameter solder ball here and
Ball grid array (BG
A) Packaged.

On the other hand, as a comparative example, a BGA package using a ceramics circuit board having a conventional structure as shown in FIG. 2 is manufactured by the same process as in Examples 1 to 4 except that the isolation wiring is not formed. did.

In order to evaluate the quality of the high frequency characteristics of the BGA package using each of the ceramic circuit boards of the examples and comparative examples manufactured as described above, signals from low frequency to high frequency are transmitted to the input side. The signal frequency when the signal intensity was halved on the output side was measured as the 3 dB down point (S21 cutoff frequency) of the measured scattering matrix value S21.
The measurement results are shown in Table 1 below.

[0035]

[Table 1]

As is clear from the results shown in Table 1, in Examples 1 to 4 in which the isolation wiring was formed around the conductor electrode portion, compared with the comparative example of the conventional structure in which the isolation wiring was not formed. S21 cutoff frequency is 50
It has been found that the high-frequency characteristics are further improved by up to 90%.

In addition to the above-described first to fourth embodiments in which the isolation wiring is formed in a rhombus, the same results as in the above-described embodiment can be obtained in the case of forming a grid-shaped isolation wiring which intersects each other at right angles. Was given. Further, the isolation wirings do not necessarily have to be connected to each other, and similar effects can be obtained even in the case where the isolation wirings are not partially formed with the line width of zero. In this case, the narrowest gap is not restricted by the arrangement pitch of the conductor electrode portions, and an arbitrary value can be selected.
Therefore, by setting the narrowest gap large,
It is also possible to reduce short-circuit accidents due to solder ball joining during mounting.

[0038]

As described above, according to the ceramic circuit board of the present invention, since the isolation wiring is formed around the conductor electrode portion, the mutual capacitance on the surface and inside of the ceramic substrate is the anti-ground capacitance. Therefore, the mutual capacitance remaining between the conductor electrode portions has a very small value due to only the space capacitance, and as a result, mutual interference of signals between the conductor electrode portions becomes small. Therefore, even when transmitting a high frequency signal, crosstalk is less likely to occur,
A ceramic circuit board having excellent operation reliability can be obtained.

Further, by forming a short-circuit line for electrically connecting the isolation wiring and the conductor electrode portion, electroplating can be performed by using the short-circuit line as a conduction line without disposing a lead wire exclusively for plating. Can be given. In addition, since no lead wire for exclusive use of plating is provided, there is little interference even when high-speed signals or high-frequency signals are processed,
A ceramic circuit board having excellent operation reliability can be obtained.

Further, since the arrangement structure of the SIG / GND twisted pair wire, which has been indispensable for improving the high frequency characteristics, is not required, the layout of the electrode portion and the wiring pattern are simplified, and the wiring design of the circuit board can be simplified. The degree of freedom can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an embodiment of a ceramics circuit board according to the present invention.

FIG. 2 is a perspective view schematically showing the configuration of a conventional ceramics circuit board.

[Explanation of symbols]

 1 Ceramics Substrate (AlN Multilayer Substrate) 2 Circuit Layer (Signal Wiring Layer) 3 Conductor Electrode (Land) 4 Isolation Wiring 5 Shorting Wire

Claims (3)

[Claims] 1. A ceramic circuit board in which a plurality of conductor electrode portions connected to the circuit layer are formed on the surface of a ceramic substrate having a circuit layer, wherein isolation wiring is formed around each of the conductor electrode portions. Ceramic circuit board. 2. The ceramic circuit board according to claim 1, wherein the isolation wiring is any one of a ground wiring, a power supply wiring and a floating wiring. 3. The ceramic circuit board according to claim 1, wherein a short-circuit line for electrically connecting the conductor electrode portion and the isolation wiring is formed.