JP2001094189A - Ceramic package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic package, which enables high-density packaging also in a transmission of a 50 Ω system, a 25 Ω system or the like, can transmit high-frequency power at low cost, and moreover without discontinuity of its characteristic impedance and moreover, enables efficient heat dissipation. SOLUTION: A ceramic package, which has a metal member 6 having a step, a wiring board 7 mounted on the member 6, and microstrip lines 4 which are penetrated a ceramic film to connect with signal conductors 3, is constituted. Even though components of different thicknesses are mounted on the member 6, the steps of the components are properly adjusted to make even the heights of the upper surfaces of the components, the length of the wire at connecting of the components with each other with a gold wire is made shortest, to prevent the inductance of the package from being increased and the member 6 is formed as a ground conductor, whereby high-frequency power is transmitted without discontinuity of the characteristic impedance of the package and heat, which is generated from the components mounted on the member 6, can be efficiently made to radiate through the member 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic package which is inexpensive, is suitable for high-density mounting, and can transmit high-frequency power without discontinuity in characteristic impedance.

[0002]

2. Description of the Related Art FIG. 4 schematically shows a conventional ceramic package for high frequency transmission.

In FIG. 4, 1 is a lead (conductor for connection to an external circuit), 2 is a ground conductor, 3 is a signal line, 4 is a microstrip line, and 5 is a conductor pad.

[0004] The microstrip line 4 penetrates the ceramic and is connected to the signal line 3, and the portion penetrating the ceramic also constitutes a strip line. On the outer surface of the package, a coplanar line composed of the signal line 3 and the ground conductors 2 arranged on both sides thereof is formed.
Therefore, each transmission line can be designed and manufactured so that the characteristic impedance becomes 50Ω or 25Ω, and high-frequency power can be transmitted using the same.

[0005]

However, when an optical element such as a semiconductor laser is mounted on a ceramic package,
Since the resistance value is about 3 to 10Ω, 4
Unless a chip resistor of about 0 to 47 Ω is placed, impedance matching as a 50 Ω system cannot be achieved. However, even a small chip resistor is about 1 mm square, so it is not suitable for high-density mounting. In particular, when making a multi-channel module using a tape fiber, the elements are often arranged at intervals of 250 μm because the fiber interval is 250 μm, but if chip resistance is used at that time, the chip resistance will be Since they cannot be arranged at such intervals, they must be installed in another place and the long distance between the element and the chip resistor must be connected with a gold wire or the like, causing an increase in inductance and narrowing the transmission band. Was.

Further, for example, when the lead pitch of a ceramic package is 1.27 mm and the characteristic impedance is 25
In the case of Ω, the width of the signal line on the outer surface of the package is set to 1.
It was 24 mm, and the gap with the ground conductor had to be 30 μm, and it was difficult to realize a conductor configuration having such a narrow gap.

Further, when a semiconductor laser or a semiconductor optical amplifier is mounted, there is a problem that heat generated by the element cannot be efficiently dissipated.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a ceramic package which can be mounted at a high density even in a 50Ω system or a 25Ω system, can transmit high frequency power at low cost without discontinuity of characteristic impedance, and can efficiently radiate heat. .

[0009]

In order to achieve the above-mentioned object, according to the present invention, as described in claim 1,
A ceramic package having a metal member exposed on a bottom surface portion, wherein the metal member has a step.

In the present invention, a wiring board having a coplanar line having a via hole is mounted on the metal member. Configure the package.

Further, in the present invention, the wiring board provided with the microstrip conductor is mounted on the metal member as described in claim 3. Constitute.

Further, in the present invention, as described in claim 4, a thin film resistor is formed in a part of the transmission line on the wiring board. Configure the package.

Further, in the present invention, a coplanar line with a ground conductor having the metal member as an additional ground conductor is provided on an outer surface thereof. Or the ceramic package described in 4 is constituted. Here, "coplanar line with ground conductor" means a coplanar line to which a ground conductor is added with a dielectric layer interposed therebetween.

Further, in the present invention, as described in claim 6, a microstrip line having the metal member as a ground conductor is provided on an outer surface thereof. Of the ceramic package. Here, the “ground conductor” means a ground conductor that is a component of the microstrip line.

As described above, the ceramic package according to the present invention is characterized in that a metal member having a step is exposed at the bottom of the package. By arranging the steps appropriately, even if parts having different thicknesses are arranged on the metal member, the heights of the upper surfaces of the parts can be made uniform, and the length of the wires can be minimized when connecting with gold wires. And an increase in inductance can be prevented.

Further, a high-frequency line having an arbitrary characteristic impedance can be realized by placing a wiring board on which a coplanar line or a microstrip conductor is formed on the metal member. That is, by appropriately designing the dielectric constant of the material used as the substrate of the wiring board, the thickness, and the width and interval of the conductor pattern, the metal member as a ground conductor,
A coplanar line or microstrip line with a ground conductor having an arbitrary characteristic impedance can be realized. In particular,
In a coplanar line with a ground conductor, a via hole is provided in a conductor pattern portion sandwiching a signal line, and the ground potential is stabilized by being electrically coupled to a metal member.
A line with excellent high-frequency characteristics can be realized.

Further, by performing pitch conversion using a wiring board, optical elements can be mounted at a high density at intervals of 250 μm. In this case, if necessary, a thin film resistor is formed on a part of the transmission line to realize good impedance matching.

Further, since the above-mentioned metal also acts as a ground conductor for a signal line disposed on the outer surface of the ceramic package, a coplanar line with a ground conductor having the signal line as a component can be designed on the outer surface. A microstrip line can be designed, an arbitrary characteristic impedance can be realized, and high-frequency power can be transmitted without discontinuity of the characteristic impedance.

Further, by using the bulk metal member, the heat generated by the device can be efficiently dissipated to the bottom surface of the package, and the device can be operated with stable characteristics.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention.
Shown in FIG. 1A is a bird's-eye view showing an overall image of a ceramic package according to the present invention, and FIG. 1B is a sectional view thereof.

In FIG. 1, 1 is a lead, 2 is a ground conductor, 3 is a signal line, 4 is a microstrip line, and 5 is a conductor pad.

Reference numeral 6 denotes a metal member made of CuW having an L-shaped cross section, which has a step in height as shown in the figure. A device or the like is mounted on a surface below the step of the metal member 6, and a wiring board 7 formed by patterning a metal on a ceramic substrate is mounted on a surface above the step.
In FIG. 1B, the cross sections of the ceramic, the ground conductor 2 and the metal member 6 are indicated by oblique lines.

As an example of the wiring pattern on the wiring board 7,
FIG. 2 shows a pattern for converting the pitch of signal lines at 500 μm intervals. A via hole 15 is provided in the conductor pattern portion 14 sandwiching the signal line 13, and the conductor pattern portion 14 is made of a metal member (6 in FIG. 1) through the via hole 15.
Is electrically coupled to the signal line 13 and the conductor pattern portion 14.
Form a coplanar line with a ground conductor using the metal member 6 as an additional ground conductor. In this case, if a 300 μm thick ceramic plate is used as the wiring board, the characteristic impedance is 50Ω. Also, signal line 1
3 is provided with a thin film resistor 16.

In FIG. 1, the microstrip line 4
Are connected to the signal line 3 through the ceramic, and also form a strip line at the portion penetrating the ceramic. Further, on the outer surface of the package, a coplanar line with a ground conductor is formed by the signal line 3, the ground conductors 2 arranged on both sides thereof, and the metal member 6.
Therefore, it is possible to design and manufacture each transmission line to have a specific characteristic impedance and use it to transmit high-frequency power without discontinuity of the characteristic impedance.

Note that even if a microstrip conductor is used instead of the coplanar line on the wiring board 7, the microstrip conductor and the metal member 6 as a ground conductor are used.
Is formed, and the same effect as described above appears.

Similarly, even when the signal line 3 is a microstrip conductor not accompanied by the ground conductor 2, the signal line 3 and the metal member 6 constitute a microstrip line, and the same effect as described above appears. .

The conductor pads 5 formed on the ceramic package are wired in the direction of the bottom surface by via holes formed in the ceramic, are pitch-converted near the bottom surface, and are connected to the corresponding leads 1.

Such a ceramic package is manufactured by preparing a ceramic package having a hole in the bottom surface by a usual method, and fitting and fixing an L-shaped metal member from below.

In the above embodiment, Cu was used as the metal member.
Although W is used, metal such as copper, aluminum, gold, and Kovar may be used, and the cross-sectional shape may be not only L-shaped but also convex or concave.

(Embodiment 2) FIG. 3 shows a second embodiment of the present invention. FIG. 3A is a bird's-eye view showing an overall image of a module using the ceramic package according to the present invention, and FIG. 3B is a sectional view thereof. In FIG. 3B, the cross sections of the ceramic, the ground conductor, and the metal member are shown by oblique lines.

In FIG. 3, a Peltier element 12 is mounted at the center of a ceramic package, and a silicon substrate 10 having a V-shaped groove and a chip thermistor 9 for temperature detection are mounted thereon. A semiconductor laser 11 is mounted on a portion of the silicon substrate 10 where the wiring conductor is formed,
The optical fiber 8 is mounted on the portion where the V-groove is formed. The current injection into the semiconductor laser 11 is realized by connecting the wiring conductor formed on the silicon substrate 10 and the wiring conductor formed on the wiring board 7 with gold wires. The wiring board 7 forms a coplanar line with a ground conductor using the L-shaped metal member 6 as an additional ground conductor, and a resistor is mounted in the middle of the coplanar line. Gold wires are also connected between the wiring board 7 and the microstrip line 4 on the ceramic package and between the chip thermistor 9 and the conductor pad 5 on the ceramic package. On the other hand, the Peltier element 12 and the conductor pad 5 on the ceramic package are connected by soldering the lead of the Peltier element.

In the above-described wiring using gold wires, if the heights of the surfaces connected by the gold wires are made uniform as shown in FIG. And an increase in inductance can be prevented.

When the semiconductor laser module manufactured as described above was operated at a temperature set to 25 ° C. by a Peltier device and a thermistor, when the current injection amount to the semiconductor laser was 29 mA, the optical output from the optical fiber was 1
mW was obtained stably. In addition, an error-free operation was confirmed for a pseudo random pattern signal of 2.5 Gbps.

In the above embodiment, the V
Although a silicon substrate with a groove is placed, a substrate made of ceramic or the like may be used, or a substrate without a substrate may be used. In addition, although a semiconductor laser is mounted, a semiconductor element such as a semiconductor optical amplifier or an electronic device may be used.

As in the case of the first embodiment, the same effects as described above can be obtained by using a microstrip line instead of the coplanar line. Further, the step of the metal member may be formed not only in the height direction but also in a general direction, for example, a horizontal direction.

[0037]

The ceramic package according to the present invention has a metal member having a step exposed on the bottom surface, and by appropriately adjusting the step, a Peltier element, a semiconductor optical component, a semiconductor electronic component, a wiring board, etc. When mounted with different thickness, the whole surface can be adjusted to the same height, the length of the wire can be minimized when connecting with gold wire, and the inductance will not increase Can be.

In addition, a metal member is used as a ground conductor, and a wiring board mounted thereon is a coplanar line or microstrip line with a ground conductor, and a coplanar line or microstrip line with a ground conductor is formed on the outer surface of the ceramic package. Therefore, high-frequency power can be supplied with good impedance matching.

Further, by using the ceramic package according to the present invention and manufacturing a module in which a semiconductor element is built in the ceramic package, the heat generated by the element can be efficiently dissipated and the element can operate stably. It has the effect of becoming.

[Brief description of the drawings]

FIGS. 1A and 1B are conceptual views showing a ceramic package according to a first embodiment of the present invention, wherein FIG. 1A is a bird's-eye view and FIG.

FIG. 2 is a conceptual diagram illustrating an example of a pattern of a wiring board.

3A and 3B are conceptual diagrams showing a ceramic package according to a second embodiment of the present invention, wherein FIG. 3A is a bird's-eye view and FIG. 3B is a sectional view.

FIG. 4 is a conceptual diagram showing a conventional ceramic package for high frequency transmission.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lead, 2 ... Grounding conductor, 3 ... Signal line, 4 ... Microstrip line, 5 ... Conductor pad, 6 ... Metal member, 7 ...
Wiring board, 8: Optical fiber, 9: Chip thermistor, 10
... V-grooved silicon substrate, 11 ... Semiconductor laser, 12 ... Peltier element, 13 ... Signal line, 14 ... Conductor pattern part, 1
5: Via hole, 16: Thin film resistor.

Continued on the front page (72) Inventor Makoto Nakamura 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term (reference) in Nippon Telegraph and Telephone Corporation 5F073 BA01 FA01 FA06 FA13 FA23 FA25 FA27 FA30

Claims (6)

[Claims] 1. A ceramic package having a metal member exposed at a bottom portion, wherein the metal member has a step. 2. The ceramic package according to claim 1, wherein a wiring board having a coplanar line having a via hole is mounted on said metal member. 3. The ceramic package according to claim 1, wherein a wiring board having a microstrip conductor is mounted on said metal member. 4. The ceramic package according to claim 2, wherein a thin film resistor is formed on a part of the transmission line on the wiring board. 5. The ceramic package according to claim 1, wherein a coplanar line with a ground conductor having said metal member as an additional ground conductor is provided on an outer surface. 6. The ceramic package according to claim 1, further comprising a microstrip line having said metal member as a ground conductor on an outer surface.