JPH0322330A - Fluorescent character display tube - Google Patents

Abstract

PURPOSE:To reduce the package size of a fluorescent character display tube by providing a thick conductor at the tip of a thin wiring conductor, and fixing an IC ball bump to the thick conductor. CONSTITUTION:A thick conductor 10 is provided at the tip of a thin wiring conductor 2a, an IC chip 12 with an IC metal ball bump 11 is fixed on its surface, i.e., the IC chip 12 is fixed on a substrate by the flip chip method, thus connection strength is excellent, reliability is high, and a fluorescent character display tube is normally operated at a high lighting ambient temperature for on-vehicle use with severe vibration. A chip fitting section can be made smaller than the conventional one, the whole fluorescent character display tube is made small, and the mounting density can be increased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fluorescent display tube, and in particular, the glass substrate of the fluorescent display tube is provided to extend from the envelope, and the extended portion is provided with a tube for driving the fluorescent display tube. A device equipped with an IC chip, commonly known as "Chip on Glass" J (hereinafter referred to as CO)
It is called G. ) Concerning the structure of a fluorescent display tube.

[Prior art 1] In recent years, fluorescent display tubes have been used not only in audio products and home appliances but also in car instruments and panels, and are called in-vehicle fluorescent display tubes. Since the mounting location of this in-vehicle fluorescent display tube is limited, a fluorescent display tube is provided in which the driving circuit of the fluorescent display tube is housed in an IC chip, and this IC chip is integrally arranged in the fluorescent display tube. . And I
A device in which a C chip is placed inside the vacuum envelope of a fluorescent display tube is called a chip-in-glass (C-I-G), and a device in which an IC chip is placed outside the vacuum envelope is called a C- It is called 0-G. C-0-G type fluorescent display tubes are C・■・
Compared to the G type, the IC chip can be placed after the sealing process of the fluorescent display tube, so there is no need to pass the IC chip through the high temperature of 400 to 500°C during sealing, and the IC chip is It has the advantage that it can be replaced if it is damaged.

In addition, because fluorescent display tubes for automobiles are installed near the engine, the environmental temperature is high and there is vibration, so the I
A strong connection between the C chip and the wiring conductor was also required.

However, the conventional C-0-G fluorescent display tube has a structure as shown in the cutaway plan view of the main part in Fig. 6 and the cross-sectional view taken along the line A-A in Fig. 6. It is known from No. 163079. In this conventional example, 21 is a glass substrate, and has a structure in which an anode substrate 21A of a fluorescent display tube and an IC chip mounting substrate 21B are integrated. The anode substrate 2l
A wiring conductor 22 made of an At thin film is placed on the anode substrate 21A.
It was extended to the chip mounting board 21B. This structure is a fluorescent display tube in which an insulating layer 23, an anode conductor 24, and a phosphor layer 25 are laminated on the wiring conductor 22.

The anode conductor 24 is formed into anode segments by a phosphor layer 25, and a plurality of these anode segments are arranged to form an anode display section 26 that displays patterns such as numbers.

A mesh-like control electrode 27 and a filament-like cathode 28 are arranged above the anode display section 26 . Further, the anode display section 26, the control electrode 27, and the cathode 28
A box-shaped container part 29 covers the anode substrate 21 so as to cover the electrodes such as
The envelope was formed by being hermetically sealed with a sealant made of frit glass disposed around the periphery.

The wiring conductor 22 was provided extending to the chip mounting board 21B outside the envelope, and a bonding pad portion 30 made of Ag paste containing no glass powder was provided at the tip thereof. Further, the IC chip 31 was adhesively fixed to the IC mounting board 1B using an epoxy adhesive 32. Then, wire bonding was performed between the Al electrode on the IC chip and the pad portion 30 using an Au wire 33, for example, by a thermosonic method. Furthermore, a protective film 34 was coated over the IC chip with silicone or epoxy plastic.

[Problem to be solved by the invention] However, C-0 by conventional wire bonding
．． The fluorescent display tube with zero structure had the following problems.

(1) The wire bonding method for bonding IC chips uses a wire placement space around the IC chip and a capillary of the bonding machine to bond between the IC on the board and the bonding pad using a bonding machine. As shown in the plan view of Figure 6, the board was extended in the direction of the long side of the rectangular envelope to form a wide extension, and in this extension IC
The chip was installed. Therefore, the entire fluorescent display tube becomes large, which poses a problem in increasing the packaging density.

(2) When a fluorescent display tube is turned on, the anode generates heat and the glass substrate is heated. This heat is also transmitted to the organic adhesive that fixes the IC chip and the resin film that protects it. Since both the adhesive material and the protective film are made of composite resin, the adhesive strength becomes weak over a long period of time, and the wire bonding may peel off, resulting in a lack of reliability.

(3) Al wiring in fluorescent display tubes is generally 50 pm
In the case of the C-0-G type, which has a particularly high wiring density, it is 30 pmllig. Furthermore, the bonding pad made of Ag paste had an li of 200 to 300 pm since it was a thick film applied by screen printing. Therefore, an Ag bonding pad part will be laminated at 200 to 300 pm on top of the 30 pm Al wiring, but since A1, which is the material of the Al wiring, is a metal that oxidizes very easily, the A1 wiring is There is also a problem in that the surface of Al is oxidized between the time when the Ag bonding pad portion is formed and good electrical continuity cannot be obtained between A1 and Ag.

(4) Furthermore, the area where the Al thin film wiring and the Ag thick film overlap is
There was also a problem in that when a temperature of 0°C was applied, A1 diffused into Ag, causing a phenomenon in which the Al connection part was disconnected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fluorescent display tube having a C-0-G structure that solves the above-mentioned problems.

[Means for Solving the Problem] In order to achieve the above-mentioned object, the structure of the present invention is such that the glass substrate of the fluorescent display tube is extended from the envelope, and an IC is installed in the extended portion.
In a fluorescent display tube equipped with a fluorescent display tube drive section using a chip, the fluorescent display tube drive section includes a wiring conductor made of a conductive thin film extending to an extended portion of the glass substrate, and a wiring conductor connected to the wiring conductor. It is characterized by having a thick film conductor made of conductive paste disposed thereon, and an IC chip fixed on the thick film conductor by metal ball bumps.

The present invention is also characterized in that the wiring conductor is formed of an Al thin film.

Further, the thick film conductor is characterized in that it contains only Ag or a conductive material containing Ag as a main component mixed with Pt or Pd and a glass solder.

Further, it is characterized in that the thick film conductor is laminated on the top surface of the tip of the wiring conductor in a dot shape.

Further, the thick film conductor has a thick film wiring portion connected to the tip of the thin film wiring conductor, and a metal ball/bump disposed on the IC chip is fixed to the tip of the thick film wiring portion. do.

Further, a thin film connecting portion wider than the thin film wiring conductor is arranged at the tip of the thin film wiring conductor, and a thick film conductor connected to the thin film connecting portion has a thick film connecting portion having a width smaller than the thin film connecting portion. It is characterized by

Furthermore, the present invention provides a fluorescent display tube in which a glass substrate of the fluorescent display tube is extended from an envelope, and a fluorescent display tube driving section using an IC chip is disposed in the extended portion, wherein the fluorescent display tube driving section is A thin film wiring conductor made of an Al thin film extending from the inside of the envelope to an extended portion of the glass substrate, a thick film wiring conductor made of a conductive paste arranged to be connected to the thin film wiring conductor, and the thick film wiring. An IC in which an insulating layer is laminated on a thick film conductor other than the tip of the conductor and the thin film wiring conductor, and a solder ball bump is fixed on the thick film wiring conductor.
It is characterized by having a chip.

[Function] The present invention has a structure in which a thick film conductor is provided at the tip of a thin film wiring conductor, and an IC chip having an IC metal ball bump is fixed to the surface of the thick film conductor. Since it is fixed by fusion such as soldering, it has superior connection strength and reliability compared to conventional wire bonding methods, and works normally even in automotive applications where the lighting environment is high and has strong vibrations. .

In addition, a wide thin film connection part was provided at the tip of the Al thin film wiring conductor, and a thick film connection part slightly narrower than the thin film connection part was also provided at the base of the Ag thick film conductor correspondingly, so that heating Even if some Al diffuses into Ag during the process, there will be no disconnection because there is a large amount of Al remaining.

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

FIG. 1 is a plan view of a first embodiment of the fluorescent display tube of the present invention, FIG. 2 is a sectional view of the same embodiment, and FIG. 3 is a
FIG. 3 is an enlarged sectional view of a main part of the same embodiment. FIG. 4 is a sectional view of the main part of the second embodiment of the fluorescent display tube of the present invention, and FIG.
The figure is a plan view showing the connecting part between the A1 thin film wiring conductor and the thick film wiring conductor of the second embodiment, FIG. 6 is a partially cutaway plan view of the conventional example, and FIG. 7 is a plan view of the conventional example. FIG. 3 is an example cross-sectional view.

[Example 1] In FIGS. 11 to 3, 1 is a glass substrate. A conductive thin film was deposited on the entire surface of the glass substrate 1 by sputtering, and a wiring conductor 2a and an anode conductor were formed by photolithography. Practice pattern 2b. In this embodiment, a case where the conductive thin film is an Al thin film will be explained. The anode conductor 2b
An insulating layer 3 is laminated and formed on the glass substrate except for. Then, a phosphor layer 4 is deposited on the anode conductor 2b.

A mesh-like control electrode 5 and a filament-like cathode 6 are arranged above the phosphor layer 4 . A box-shaped container portion 9 consisting of a side plate 7 and a front plate 8 is sealed onto the glass substrate 1 so as to cover these electrodes, thereby constructing a fluorescent display tube.

The glass substrate 1 is provided extending to the short side of the container portion 9, and a wiring conductor 2a is extended from the above-mentioned fluorescent display tube to this extended portion, and a metal ball of an IC chip, which will be described later, is connected to the glass substrate 1.
It is patterned to correspond to the bumps. The width of this wiring conductor 2A is 100 pm or more, and a dot-shaped thick film conductor 10 is formed at the tip thereof. The thick film conductor 10 is A
A conductive powder containing g as a main component and a small amount of Pd mixed with a low melting point glass solder is made into a paste using a vehicle, and a conductive paste is formed on the tip of the wiring conductor 2a by a screen printing method. The conductive powder is the above-mentioned A
In addition to g-Pd, only Ag or Ag-Pt is also possible. Further, an insulating layer 3 for protection is provided on the wiring conductor 2a.
is formed by screen printing method. The thick films such as the insulating layer 3 and the thick film conductor 10 are deposited by screen printing and then burned in a furnace in an oxidizing atmosphere to evaporate the vehicle and fix them onto the substrate.

Next, the IC chip 1 on which the metal ball bump 11 is arranged
2 is heat-fixed onto the thick film conductor 10. The material of the metal pole bump 11 is Au, Ag, Ni, Cu.
, solder, etc., but in this example, since the substrate is a glass substrate, it cannot be heated to a very high temperature, so solder balls and bumps 11 using solder metal are provided.
Adopted C chip. Therefore, the IC chip can be reliably fused to the thick film conductor 10 by heating to 180 to 280°C.

Further, a composite resin serving as a protective film 13 is molded around the IC chip to complete the fluorescent display tube.

[Example 21 Example 1 is applied to a fluorescent display tube in which the thin film wiring conductor in the extension part has a certain width, but Example 2 is applied to a fluorescent display tube in which the thin film wiring conductor has a thickness of 50 pm or less. It is. Since the grooves of the fluorescent display tube in the envelope are the same as in the first embodiment, their explanation will be omitted, and only the IC chip mounting portion will be explained. The A1 thin film wiring conductor 2a extending from the inside of the envelope has a line width of 50 pm or less, so that the wiring packaging density can be increased.

At the tip of the Al thin film wiring conductor 2a, as shown in FIG. 5, a rectangular thin film connection part 14 having a width of approximately 150 to 200 pm is provided as an Al thin film and continuous to the Al thin film wiring conductor. ing. On the upper surface of this Al thin film connection part 14, a thick film connection part 15 which is narrower in width and shorter in length than the Al thin film connection part 14 is stacked and arranged at a predetermined distance from the connection part of the thin film wiring 2a. A thick film wiring conductor 16 is disposed continuously to the thick film connection portion 15, and a solder ball/bump 11 of the IC chip 12 is fixed to the tip of the thick film wiring conductor 16. The thick film connection portion 15 and the thick film wiring conductor 16 were coated with the same conductive paste as in Example 1 by screen printing, and then heated at 400 to 500°C.
A conductive layer is formed on the surface by firing.

Further, the insulating layer 3 laminated on the thin film wiring conductor, the thin film connecting portion, the thick film connecting portion, and the thick film wiring conductor is composed of two layers to further strengthen protection. Further, the second insulating layer is placed outside of the first layer so that overcoat resin, which will be described later, can easily flow under the IC chip.

In this example, the connection part between the A1 thin film and the Ag thick film is the wiring conductor 2.
Since it is in contact with a surface wider than a,
Even when heated during the manufacturing process of a fluorescent display tube, some amount of Al will diffuse into Ag, but since Al has a larger area, there will be no disconnection, and conduction can be ensured.

Furthermore, since the Ag thick film is applied by screen printing, the accuracy is not very high, but since the area of the Ag thick film connection is smaller than that of the Al thin film connection, even if there is some printing misalignment, the two will contact each other. It turns out.

Furthermore, by arranging the connecting portion between the Al thin film and the Ag thick film in the envelope of the fluorescent display tube, it is possible to improve the reliability of the conductive I.

Next, the solder balls and bumps of the IC chip placed on the thick film wiring conductor are heated to melt the solder and are fused to the Ag on the surface of the thick film wiring conductor.

Finally, a coating resin is overcoated around the IC chip as a protective film 13.

[Effect J] As explained above, the present invention provides C. O. In the fluorescent display tube of the G structure, a thick film conductor is provided at the end of the thin film wiring conductor, and the solder balls and bumps of the IC are fixed to the thick film conductor, so that the following effects are obtained.

(1) Since the mounting area of the IC chip is smaller than that of the conventional wire bonding method, the chip mounting part can be made smaller than the conventional method, which has the effect of making it possible to reduce the package size of the fluorescent display tube.

(2) A thin film connection section is provided at the end of the Al thin film wiring, and Ag
Since it was connected to a thick film conductor, there was no disconnection due to Al diffusion, and good electrical continuity was obtained between the Al thin film wiring and the Ag thick film conductor.

(3) Since the IC chip is fused to the Ag thick film conductor using solder poles and bumps, the connection mechanism is resistant to heat and vibration, and has the effect of providing a fluorescent display tube with excellent electrical reliability.

(4) Since wide connecting portions are provided at both the contact portions between the Al thin film and the Ag thick film, there is an effect that poor conductivity due to misalignment of the printing position of the Ag thick film paste is eliminated.

[Brief explanation of drawings]

FIG. 1 is a plan view of a fluorescent display tube of the present invention, FIG. 2 is a cross-sectional view of the first embodiment of the present invention, and FIG. 3 is an enlarged cross-sectional view of essential parts of the first embodiment of the present invention. , FIG. 4 is a sectional view of the second embodiment of the present invention, FIG. 5 is a plan view of the main part of the second embodiment of the present invention, and FIG. 6 is a diagram of a conventional COG structure fluorescent display tube. The partially cutaway plan view, FIG. 7, is a cross-sectional view taken along the line A--A in FIG. 6. 1...Glass substrate 3...Insulating layer 10...Thick film conductor 12...IC chip 15...・Thick film connection part 2a...Thin film wiring conductor 4...Phosphor layer 1 work...Metal ball/bump (solder ball/bump) 14...Thin film connection part 16... Thick film wiring conductor

Claims (9)

[Claims] (1) In a fluorescent display tube in which a glass substrate of the fluorescent display tube is extended from a container part and a fluorescent display tube driving section using an IC chip is disposed in the extended portion, the fluorescent display tube driving section is an extension of the glass substrate. A wiring conductor made of a conductive thin film extending over a portion, a thick film conductor made of a conductive paste connected to the wiring conductor, and an IC chip fixed on the thick film conductor with metal balls and bumps. A fluorescent display tube comprising: (2) The fluorescent display tube according to claim 1, wherein the wiring conductor is formed of an Al thin film. (3) The fluorescent display tube according to claim 1, wherein the thick film conductor contains only Ag or a conductive material containing Ag as a main component mixed with Pt or Pd and a glass solder. (4) The fluorescent display tube according to claim 1, wherein the thick film conductor has a dot shape laminated on the upper surface of the tip end of the wiring conductor. (5) The thick film conductor has a thick film wiring portion connected to the tip of the thin film wiring conductor, and a metal ball/bump disposed on an IC chip is fixed to the tip of the thick film wiring portion. 1
The fluorescent display tube described. (6) A thin film connecting portion wider than the thin film wiring conductor is provided at the tip of the thin film wiring conductor, and a thick film conductor connected to the thin film connecting portion has a thick film connecting portion having a width smaller than the thin film connecting portion. 6. The fluorescent display tube according to claim 1, 2, 3, or 5. (7) In a fluorescent display tube in which a glass substrate of the fluorescent display tube is extended from an envelope, and a fluorescent display tube drive section using an IC chip is disposed in the extended portion, the fluorescent display tube drive section is connected to the glass substrate. A thin film wiring conductor made of an Al thin film extending from the inside of the envelope to the extension part, and a thick film wiring conductor made of a conductive paste arranged to be connected to the thin film wiring conductor.
It has an insulating layer laminated on the thick film wiring conductor other than the tip portion of the thick film wiring conductor and the thin film wiring conductor, and an IC chip having solder balls and bumps fixed on the thick film wiring conductor. A fluorescent display tube featuring (8) The fluorescent display tube according to claim 7, wherein the thick film wiring conductor contains only Ag or a conductive material containing Ag as a main component mixed with Pt or Pd and a low melting point glass solder. (9) A thin film connection portion in which the tip of the Al thin film wiring conductor is formed wider than the wiring, and a thick film connection formed in the base of the thick film wiring conductor to be wider than the thick film wiring and narrower than the thin film connection portion. 9. The fluorescent display tube according to claim 7 or 8, wherein the fluorescent display tube has a laminated structure.