JPS61265843A - Support incorporating decoupling member for high-speed structural part, especially microwave frequency structural part - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to supports for high speed components.

The invention is applicable to all high speed devices, especially microwave frequency components, and bipolar or field effect transistors, most particularly those made on gallium arsenide substrates. Due to their high operating frequencies, such components require very complete decoupling to some of their electrodes, for example the source(s) of a field effect transistor (FIeT). The foregoing shows that the capacitance changes due to inductive effects (
The device needs to be placed as close as possible to the electrodes requiring decoupling to avoid this (which would cause the device to lose its high speed advantage).

However, at microwave frequencies, in order to avoid capacitive coupling between the various electrodes of the component (e.g. between drain and gate or between the two norths of a FIT), the gain is reduced such that such spurious capacitances are ，
It is also necessary that it fall very quickly as soon as the value of 3 bifurands is reached.

In practice, the supports used are either high dielectric constant supports where spurious or stray capacitances between the electrodes set high frequency operation limits, or else low dielectric constant supports are used. These low dielectric constant supports do not provide adequate decoupling and require capacitor components to be added to them, thereby requiring extra connections, thus complicating fabrication and reducing induction. creating a risk of causing an effect.

Preferred embodiments of the present invention avoid these drawbacks by providing a support surface that also provides excellent decoupling to some of the component's electrodes while avoiding capacitive coupling between the component's electrodes. This support has a mold constituted by a sintered block of stacks of ceramic sheets, each having a high dielectric constant. The support has a surface metallization (ms) forming connections to the terminals of the component.
-tallzation).

According to the invention, the support has a central band (said central band is made of a material with a low dielectric constant) which appears at the surface of the support and extends substantially over the area of the supported component. include. Outside said central band, around said central band and at a shallow depth below the surface of the support, there is an internal metallization formed by a conductive pattern originating from one of the sheets of the stack and connected to a ground connection. The blank, this internal metallization and one of the surface metallizations have surfaces facing each other and constitute decoupling capacitors for the terminals of the components connected to said surface metallization.

Naturally, the invention relates both to supports already provided with a surface metallization, ie ready to receive components, and to supports that have not yet received their surface metallization. It will be seen from the following that the surface metallization need not be applied during the fabrication of the support itself. in this way,
In some cases, the user can apply the surface metallization himself if he prefers, thereby providing the desired shape and configuration suitable for a given application.

In a first embodiment, the low dielectric constant material is a vitroaeramic, ie, a low melting point crystallized glass impregnated with a dielectric material. The vitroceramic is selected to be compatible with the dielectric ceramic under mechanical and thermal stress.

In a second embodiment, the low dielectric constant material is a magnesia titanate based ceramic. This cell has a sinterability close to that of a high relative permittivity dielectric, and is compatible under thermal stress and mechanical stress even after sintering.

Furthermore, and advantageously, the high dielectric constant ceramic is, for example, a ceramic based on barium titanate doped with praseodymium and neodymium oxides.

The invention also relates to a method for manufacturing such a support. The method involves stacking sheets of raw ceramic, at least one of the sheets having a conductive pattern thereon, and at least the last sheet of the stack being a dead ceramic of a suitable thickness to form a dielectric. (dealiceramic
) 1. Compact and dry the stack, make a hole, which is a blind hole or can pass through the stack at right angles, in the central band position in such a way as to form a depression, and press the ceramic. Fire for a first hour, fill the recess with a low dielectric constant material (glass or ceramic), fire the filler, and adjust the rectification).

Polish and Cut into unit parts It consists of things.

Advantageously, the first firing step is replaced by a single co-firing step during the second firing step to fire both the ceramic and the filler. This variant is particularly advantageous when the low dielectric constant material is a ceramic.

Other features and advantages of the invention will become apparent upon reading the following detailed description given with reference to the accompanying drawings.

FIG. 1 is a plan view showing connections 21-2 disposed on the surface of a conventional substrate 10. Components for connection thereto are shown in dashed lines.

Here and in the following description, the components used as examples are field effect transistors, but this example should not be construed as limiting. The two electrodes 21 and ρ are thus electrodes for connection to the source of the transistor, one electrode wing and 24Fi are electrodes for connection to the gate and drain, respectively.

If the support 10 is made of a ceramic with a high dielectric constant, and if the internal electrodes are provided inside the support connected to earth (not shown), then depending on the operating frequency from about 10 pF to By suitably plating the internal electrodes in such a way that they have a capacitance of 60 pF, it is possible to provide good decoupling for both sources, ie the two electrodes 21 and B.

In contrast, it is impossible to avoid the appearance of stray capacitances (indicated by 40) between the various electrodes. This stray capacitance is inherent to the high dielectric constant of the materials used and, once its value exceeds 2.3 pF, it significantly reduces the performance of the component when mounted on a support.

To alleviate this drawback, the present invention provides a support 1 shown in cross-section and plan view in FIGS. 2 and 3, respectively.
I suggest 00. The support is constituted by a sintered block 120 of high dielectric constant ceramic. In between is an exposed central band 110 extending over substantially the same area between the locations occupied by the components to which it is to be applied. This central band is made from a low dielectric constant material.

Here and in the following description, the term "low dielectric constant" is used to indicate a dielectric constant of less than 100;
And the term "high dielectric constant" is used to indicate a dielectric constant greater than 1000.

In order to decouple the surface electrodes 21 and 22 (corresponding to the electrodes connected to the source of the transistor), electrodes 131 and 132 are provided at a shallow depth e below the surface of the substrate in the high dielectric constant region. These internal electrodes 131 and 132 are placed opposite the surface electrodes 21 and B so that each source is connected to a decoupling capacitor (the third
(as shown in the figure).

Electrodes 131 and 132 are also connected to ground by one or more connections 141 142 in the form of metallization external to the support.

The internal electrodes 131 and 132 may be constituted by a conductive t-pattern carried by one of the sheets in a stack of sintered blocks, for example.

- In the specific example, the dimensions of the support are as follows;
Height h = 1.2 haze; Diameter of central band (1 = Q, 9■; Depth of central band p = 0.4 wl; Thickness of dielectric layer constituting capacitance e = 5Qμm; Electrode and central band Guard space a=0.3-0 between internal electrodes 131 and 132
The width and length of are selected as a function of the desired decoupling capacitance. The size and shape of surface electrodes 21-U are selected to minimize stray capacitance and inductance.

The support with this property is specifically 0,3×O,3tt
It is suitable for microwave components in the form of m chips.

The high dielectric constant ceramic is preferably selected as a barium titanate based ceramic doped with praseodymium and neodymium oxides.

The following composition having a specific inductivity of 2700 at l KH2 is particularly suitable in the present case.

0.897'rio2+ 0,875BaO+ 0.0
21 Nb2O5 + 0.017Pr02 + 0.01
20aO+ 0.006Nd203 (proportions given in moles) and alumina and silica additives The low dielectric constant materials used in the preferred embodiment are and troceramics, i.e. crystallized materials having a low melting point and impregnated with an inductive material. It's glass. Suitable materials in this application include, for example, 40 to 65% by weight of lead borosilicate, 5 to 65% by weight of bismuth oxide,
25% by weight, and titanium oxide or cadmium oxide 3
~30! Consisting of ii%.

Such materials have melting points and coefficients of expansion that are close to those of high dielectric constant ceramics, thereby ensuring complete compatibility with high dielectric constant ceramics.

From the standpoint of electrical protection, such Toro ceramics are
It has a dielectric constant of approximately 2.4 at Hz [, thus avoiding the appearance of stray capacitances between the various electrodes of the component.

In another embodiment, the low dielectric constant material is a magnesia titanate based ceramic.

The following compositions are particularly suitable.

TiO2+ 0.83 MgO+〇, 14 BaO+
0.16 ZnO+ 0-05Zr02 + 0.04
0ak (proportions given in moles) and traces of silica and alumina. This ceramic has a dielectric constant of 6 at 1 KHz. Additionally, the ceramic is compatible with the high dielectric constant ceramic used for the remainder of the support in terms of firing degree and shrinkage upon firing.

A method of manufacturing a support according to the invention will now be described.

First, a stack of unit sheets of raw ceramic, each having a thickness of about (μm) when raw, is made.

In particular, D of sheets such as 200 in FIG.
An initial stack of sheets is made and then metallization 211 is added to the sheets which constitutes an internal plate of one reduced combined capacitance (see sheet 210 in FIG. 5). And finally, one or more sheets of 200 identical dead ceramics are added to yield a thickness suitable for constructing a decoupling capacitance shield. In Figures 4 and 5, the slope line indicates the future center zone position and! (Along this line the support will be cut and split into individual supports).

In the second step, the stack of raw ceramic sheets is compressed, compressed, and dried in a conventional manner.

After this step, a hole is made in it. The holes can be blind holes or holes that can be passed through the stack at right angles, at the location of the central strip of the individual supports, thereby forming depressions in each support. In Figure 6,
These recesses are shown at 300 and the conductor butter/211 is shown in dashed lines as it is now buried inside the ceramic.

Thereafter, a first ceramic firing operation is performed on the ceramic composition at a high temperature, for example 1267r.

The subsequent step consists of filling the recess 300 with vitreous ceramic or otherwise ceramic.

Both materials have as low a dielectric constant as possible and have a coefficient of expansion that is commensurate with that of the high dielectric constant ceramic.

A second firing operation of the filler is then carried out at a low temperature (approximately 7500 ℃).

The block is then adjusted to make it perfectly planar and to prevent the induction in future decoupling capacitors! Adjust body thickness θ. After this step, a polishing operation is performed.

Finally, the unit supports are separated into individual parts, for example by sawing.

Next, external metallization is deposited onto each individual support, for example by wetting the ends of the blocks in a conductive fen. It is then dried and cured.

In an advantageous variant of the method, which is particularly suitable for embodiments in which the low dielectric constant material is a ceramic, the first firing step is omitted and replaced by a single co-firing step in said second firing step. be done.

Therefore, the two ceramics are selected to have the same shrinkage and the same firing temperature to enable co-firing.

Additionally, as described above, the depressions forming the central band are created by drilling holes prior to firing. However, other techniques (e.g., sand blasting, laser drilling) that could produce depressions of various shapes other than those shown (e.g., frustum-shaped depressions due to sand erosion) could be used. Ta.

Furthermore, if it is desired to make a support already provided with surface contact metallizations for the connection of the components to the electrodes, these surface metallizations can be carried out by vacuum evaporation or cathodic sputtering and with appropriate masking. It can be made collectively by later chemical etching. This can be done between the polishing and cutting steps of the method.

7-10 relate to alternative embodiments of the external metallization forming the ground connection. Instead of metallizing one or more of the side faces of the block, it is advantageous to connect it to the internal electrode 211 via a hole 400 through the bottom of one component. These holes can pass through the component at right angles or can be blind holes drilled from the bottom. The holes can be made at the same time as the recesses 300 and then metallized.

The supports can be cut into unit supports through metallization or plating through holes as shown in FIG.

This provides support as shown in FIGS. 8 and 9. In this case, a semi-cylindrical notch 4 in its side surface
A ground connection is made via 10:Th and 420. These cutouts are preferably metallized by metallization continuing over the underside of the support via suitable over-two tabs 411 or 421 to form the subsequent ground connection (FIGS. 9 and 10). ).

In a variant, the holes are blind holes (FIG. 11), thereby allowing the surface electrodes 21 and η to reach the sides of the unit support.

[Brief explanation of drawings]

Fig. 1 is a line plan view showing the arrangement of connection electrodes to components on a normal support, and Fig. 2 is a cross section taken along the line ■-■ in Fig. 3 through the support according to the present invention. Figure 3 is a plan view taken along the line ■-■ of Figure 2 of the same support, Figures 4 to 6 are diagrams showing the stages of forming a stack of ceramic sheets and the stage of forming holes in the stack. , FIG. 7 shows a modification of FIG. 6 in which the support includes a connection socket in the form of a mated through hole, and FIGS. 8 and 9 each show a top view of a component corresponding to the modification of FIG. and perspective view from below, No. 10
The figure shows a second view through the component parts corresponding to the modification of FIG. 7.
FIG. 11 is a sectional view similar to FIG. 10 for another variant embodiment. 21-24...Surface metallization, I...Component part, ioo...Support, 110...Central band, 1
31, 132...internal metallization, 141
, 142... Ground connection, 200, 210... Ceramic sheet, 211... Conductive pattern 7.300
, 400--Hole, 410, 420--Metted through hole, 411, 421--Overlap.

Claims (1)

Claims: 1. A high dielectric constant ceramic sheet suitable for receiving surface metallizations (21-24) constituting the connection to the terminals of the component supported by the support. A support (100) for a high-speed component (30), in particular a microwave frequency component, in the form of a sintered block constituted by a stack, the support appearing on the surface of the support and , a central band (110) extending over substantially the same area as the supported component (30), said central band being formed of a material having a low dielectric constant; and a support. is provided with at least one inner layer (131, 132) of metallization outside and peripherally to the central zone at a shallow depth (e) below the surface of the support;
Said metallization is carried by one of the sheets of the stack and is formed by a conductive pattern connected to a ground connection (141, 142), the internal metallization (131, 132) being Opposing at least a portion of the surface metallization (21, 22), a decoupling capacitor for connection to at least one of the terminals of the component carried by the support is configured with the surface metallization. A support, characterized by: 2. The ground connection is by means of a metallization (141, 142) connected over the entire height of one of the side faces of the block and electrically connected to the conductive pattern by a portion appearing in said side face. A support according to claim 1, which is formed by: 3. The ground connection is formed by a plated through hole (410, 420) or can be a blind hole or can be passed through the support and is formed by a portion of the hole through the conductive pattern. A support according to scope 1. 4. Support according to claim 3, wherein the metallization (410, 420) extends to overlap (411, 412) the bottom surface of the substrate. 5. The support according to claim 1, wherein the low dielectric constant material is a vitroceramic. 6. Support according to claim 1, wherein the low dielectric constant material is a ceramic based on magnesia titanate. 7. The support according to claim 1, wherein the high dielectric constant ceramic is a ceramic based on barium titanate. 8. constituted by a stack of high dielectric constant ceramic sheets suitable for receiving surface metallizations (21-24) constituting the connection to the terminals of the component supported by the support; A support (100) for a high-speed component (30), in particular a microwave frequency component, in the form of a sintered block, the support appearing on the surface of the support and supporting the supported component (30). ), the central band is formed of a material having a low dielectric constant, and the support is outside of and to the central band. Peripherally, a shallow depth below the surface of the support (
e) at least one metallization inner layer (1
31, 132), said metallization being carried by one of the sheets of the stack and having a ground connection (14).
1, 142) and the internal metallization (131, 132) is formed by a conductive pattern connected to the surface metallization (21, 142).
22), with a surface metallization comprising a decoupling capacitor for connection to at least one of the terminals of a component carried by the support, at least one having a conductive pattern (211) thereon;
stacking raw ceramic sheets (200, 210) containing three sheets (210) (at least the last sheet of the stack is a dead ceramic sheet of suitable thickness to constitute a dielectric) and compressing the stack; and drying, forming a hole (300) which is a blind hole or can be passed through the stack at the location of the central band to constitute the recess, and performing a first firing operation to fire the ceramic, forming the recess into a low A method for manufacturing a support, characterized in that it is filled with a dielectric constant material (glass or ceramic), a second firing operation is performed in which the filler is fired, conditioning, polishing and cutting into unit support members. . 9. The first firing step is omitted, and the second firing step is
9. A method as claimed in claim 8, substituted by a single co-firing step in which both the ceramic and the filler are fired. 10. The method is to remove holes (40
9. A method as claimed in claim 8 for manufacturing a support as claimed in claim 3, comprising the step of forming 0) and metallizing said holes. 11. The method of claim 10, wherein the support is cut into unit support members through metallized holes.