JPH06111735A - Display apapratus provided with field emission type cathode and mounting method of emission type cathode - Google Patents

Abstract

PURPOSE:To mount a FEC against an anode as a light emitting display part installed in a vacuum container of a fluorescent display apparatus while positioning the FEC correctly. CONSTITUTION:A electric field-effect type cathode(FEC) having an emitter 7 is formed on a Si substrate 1. Bump 10, 9 are formed respectively a gate electrode layer 5 and an emitter electrode 8 of the FEC. An anode 15 is formed on a face plate 11. Whiel the FEC 2 being kept downward, the Si substrate 1 is mounted on the face plate 11. Positioning of the FEC and the anode 15 is carried out and the bumps 9, 10 are connected with a wiring conductor 12. A back plate is layered on the substrate 1 and the back plate and the face plate 11 are pressed to pinch and fix the Si substrate between them. In this condition, the back plate and the face plate 11 are sealed with a seal paste 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a field emission cathode on a substrate.

[0002]

2. Description of the Related Art A field emission type cathode can be used as an electron source of a display tube having an anode as a display portion such as a fluorescent display tube. In such a case, it is usual to mount the field emission cathode directly on the inner surface of the substrate forming the envelope of the display tube.

FIG. 2 shows a conventional fluorescent display tube in which a field emission cathode is mounted. As shown in the figure, according to the conventional method of mounting a field emission cathode, the cathode conductor 102 and the wiring conductor made of an Al thin film are directly formed on the inner surface of the glass substrate 101 which is a part of the envelope 100. ing. An insulating layer 103 and a gate electrode layer 104 are stacked on top of this, and holes 105 are formed in both layers by photoetching. Then, a cone-shaped emitter 106 is formed on the cathode conductor 102 in the hole 105 by vapor deposition.

In FIG. 2, the other glass substrate 1 facing the glass substrate 101 on which the field emission cathode is mounted.
On 07, an anode 108 having a phosphor layer is formed in a predetermined pattern. Each of the anodes 108 is partitioned by a screen 109, and faces each of the field emission cathodes formed in a predetermined pattern corresponding to the pattern of the anodes 108.

[0005]

According to the conventional method of directly mounting the field emission type cathode on the inner surface of the substrate constituting the envelope of the display tube, the pattern of the field emission type cathode and the pattern of the anode are formed. There was a problem that it was difficult to align the positions.

That is, the envelope 100 of the above-mentioned fluorescent display tube.
To form a glass substrate having a field emission cathode 1
01 and another glass substrate 107 having the anode 108 are faced to each other at a predetermined interval and heat-sealed with a sealing material. At this time, the properly aligned glass substrates 101 and 107 are pressed from both sides, but the directions of the forces cannot be completely the same. Therefore, even if the alignment is correctly performed, the cathode and the anode are not sealed after sealing. The pattern of may not match.

It is an object of the present invention to provide a display device in which a field emission cathode is mounted and a method for mounting the field emission cathode in which the cathode can be properly aligned with the anode arranged in the vacuum container. .

[0008]

A display device mounted with a field emission type cathode according to the present invention is provided with a face plate having a wiring conductor for bump connection and an anode electrode, and facing the anode electrode. A field emission cathode on the substrate, bumps formed on the gate electrode of the field emission cathode and terminal electrodes on the substrate, and a back plate for pressing and fixing the substrate to a face plate. Is characterized by. Further, a method for mounting a field emission type cathode according to the present invention comprises a step of forming a wiring conductor and an anode conductor on a face plate, and a field emission type cathode having bumps so as to face the anode electrode at a predetermined interval. Positioning on the face plate, pressing the field emission type cathode to the face plate by a back plate and fixing the back plate to the face plate to form a sealed mounting chamber for the field emission type cathode. And the process of doing.

[0009]

EXAMPLE This example relates to a method of mounting a field emission type cathode in a fluorescent display device. FIG. 1 is a cross-sectional view of a fluorescent display device 3 having a field emission cathode 2 (hereinafter abbreviated as FEC 2) formed on a Si substrate 1 acting as a cathode conductor. As shown in FIG.
An insulating layer 4 made of SiO ₂ and a gate electrode layer 5 made of Nb are laminated on the substrate 1. A hole 6 having a diameter of about 1 μm is formed in the insulating layer 4 and the gate electrode layer 5, and a cone-shaped emitter 7 made of Mo is formed in the hole 6. The height of the emitter 7 is the same as the height of the gate on the insulating layer from the Si substrate. A cathode conductor terminal 8 made of Mo is formed on a part of the Si substrate 1. The cathode conductor terminal 8 has a diameter of 100 μm on the insulating layer 4 in the step of forming the hole 6.
It is possible to form the same height as the height of the emitter 7 and the gate 5 from the Si substrate by simultaneously forming holes of a certain degree and further vaporizing Mo in the holes in the step of forming the emitter 7.

Bumps 9 and 10 having the same height are formed on the cathode conductor terminal 8 and the gate electrode layer 5, respectively. As will be described later, the bumps 9 and 10 determine the distance between the FEC 2 and the anode when the FEC 2 is mounted, and can be set to, for example, about 5 to 50 μm. further,
The bump 9 connects the cathode conductor terminal 8 and the wiring conductor 12 to each other, and the bump 10 connects the gate electrode 6 and the gate connection wiring conductor 18 to each other.

As a method of forming bumps, a method by plating, a stud bump method using the first side of wire bonding, a method of forming conductive particles on electrode pads, and the like can be considered. The plating method is a method of forming bumps on the electrode pads by using Au plating. This is the most proven method for forming bumps. As a forming method, a barrier metal is formed on the electrode pad and a resist is applied. Only the pad portion of this resist is opened and Au plating is performed. In this case, the resist thickness becomes the bump height. After the plating is completed, the resist and excess barrier metal are removed, and the bump formation is completed. The plating bump includes a method of directly forming on the electrode and a transfer bump method of forming on the glass substrate or the like and then transferring to the electrode. The height of the bump is determined by the resist coating thickness. Currently, when using a normal resist, 3
The height is about 20 to 40 μm using a thick film resist.

The stud bump method is a method of forming bumps using the first side of wire bonding.
As a forming method, 1st bonding is performed by ball bonding and a wire is cut after the bonding, or 2nd bonding is bonded to the upper surface of the lower portion of the bump. For stud bumps, the height regulation is determined by the wire diameter. In this case, the thinner the wire, the lower the bump, and the thicker the wire, the higher the bump. Currently, 30 ~
It is about 50 μm. If wedge bonding is used instead of ball bonding, the height of the bump can be increased to 1-2 μm.

According to the method of using the conductive particles for the bumps, the conductive particles are arranged on the electrode pad and the particles are used for connection. As a method of arranging conductive particles on bumps,
A method of selectively forming conductive particles on the electrode pad using a photoadhesive method is common. As another method, a method has been disclosed in which conductive particles are dispersed in a resist, the resist is applied and patterned to form only on the electrode.

Next, the wiring conductor 12 connected to the cathode conductor is formed on the inner surface of the face plate 11 made of glass or alumina.
And the wiring conductor 18 and the anode conductor 1 connected to the gate electrode layer 5
3 is formed by processing the conductive thin film by means of photolithography. A phosphor layer 14 is formed in a predetermined pattern on the anode conductor 13 to form an anode 15 as a light emitting display section.

Next, the Si substrate 1 is mounted on the face plate 11 with the FEC 2 facing the anode 15. At this time, the Si substrate 1 is placed face down on the face plate 11 while observing with a microscope so that the pattern of the emitter 7 on the Si substrate 1 and the pattern of the anode 15 on the face plate 11 can be correctly aligned. The bumps 9 and 10 are connected to the wiring conductors 12 and 18 at predetermined positions. In this step, a conductive paste may be transferred to the bumps 9 and 10 and the conductive paste may be hardened after mounting to securely and temporarily fix the FEC 2 and the Si substrate 1 on the face plate 11.

A back plate 16 facing the face plate 11 is prepared, and a sealing paste 17 having a low softening point glass as a main component for sealing is preliminarily formed on the inner peripheral portions of the face plate 11 and the back plate 16. Keep it. The back plate 16 is positioned with respect to the face plate 11 and placed on the Si substrate 1. Then, the Si substrate 1 is sandwiched between the back plate 16 and the face plate 11, and both plates 11, 1
6 is pressurized, and a sealing process is performed in that state to seal the FEC 2 in the mounting chamber 18.

Then, the inside of the mounting chamber 18 in which the FEC 2 and the anode 15 are housed is evacuated. As a method of applying a vacuum,
Three methods are conceivable: a method of providing an exhaust pipe on the back plate 16 to suck the inside of the mounting chamber, a method of sucking from an exhaust hole provided on the back plate 16 to seal with a lid, and a method of sealing in vacuum. .

According to the method or structure of the present embodiment, since the back plate 16 is constantly pressing the FEC 2, the bumps 9 and 10 provided on the FEC 2 are always strongly pressed against the wiring conductor 12 to ensure the reliability. , The electrical connection is very good.

Further, since the bumps 9 and 10 are pressed and slightly deformed, there is no variation in the height of the bumps 9 and 10, and the spacing between the FEC 2 and the anode 15 becomes uniform.

In the embodiment described above, the FEC2 is set to S
It was formed on the i substrate 1. In general, it is difficult to manufacture a large Si substrate that can be used as a substrate for a display device, but according to the present embodiment, a large number of small Si substrates each having an FEC formed thereon are used as anodes for face plates. A mounting method is possible in which the back plates 16 are accurately positioned and then fixed with one back plate 16. The FEC may be formed on a glass substrate.

[0021]

According to the display device or the FEC mounting method of the present invention, the FEC having the bumps is positioned on the face plate having the anode, and the FEC is pressed by the back plate to be fixed between the FEC and the face plate. is doing.
Therefore, according to the present invention, the following effects can be obtained.

(1) Since the distance between the FEC and the anode is determined by the height of the bump, it can be set uniformly and accurately.

(2) Since the FEC is sandwiched between two plates, the FEC does not come off during sealing, and there are few defects during mounting. In particular, FE formed on Si substrate
When C is mounted on a glass substrate, peeling should easily occur due to the difference in the thermal expansion coefficient between Si and glass, but the structure according to the present invention does not peel it.

(3) The bump has two functions, that is, a spacer for keeping the distance between the FEC and the anode, and an electrical connection. Therefore, it is not necessary to provide both the spacer and the electrical connection member.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a conventional technique.

[Explanation of symbols]

 2 field emission type cathode (FEC) 9,10 bump 11 face plate 12 wiring conductor 13 anode conductor 16 back plate 18 mounting chamber

Claims (6)

[Claims] 1. A face plate on which a wiring conductor for bump connection and an anode electrode are formed, a field emission cathode on a substrate provided facing the anode electrode, and a gate electrode of the field emission cathode. And a bump formed on a terminal electrode on the substrate, and a back plate for pressing and fixing the substrate to a face plate. 2. The display device having the field emission cathode according to claim 1, wherein the bumps have conductivity and have the same height. 3. A step of forming a wiring conductor and an anode electrode on a face plate, and a step of positioning a field emission cathode having bumps on the face plate so as to face the anode electrode at a predetermined interval. Pressing the field emission cathode against the face plate by a back plate and fixing the back plate to the face plate to form a sealed mounting chamber of the field emission cathode. How to implement. 4. The electric field according to claim 3, wherein the face plate and the back plate are made of glass substrates, and a sealing material containing low softening point glass as a main component is used to fix the back plate to the face plate. Emission type cathode mounting method. 5. The method for mounting a field emission cathode according to claim 3, wherein the mounting chamber is set to a vacuum atmosphere. 6. A step of positioning the field emission cathode on the face plate, wherein bumps formed on the field emission cathode are coated with a conductive adhesive and temporarily fixed to the face plate. The method for mounting a field emission cathode according to claim 3.