JPH0567058B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention has a simple structure, high reliability, can be made thin, and is inexpensive. The present invention relates to a method for connecting a semiconductor device that can connect a semiconductor device to a semiconductor device.

(Prior art and its problems) In recent years, flat displays such as dot matrix LCDs and dot matrix PDPs have been
It has been commercialized as a display for TVs and personal computers, but as the amount of information to be displayed has increased, the number of displays has increased to 80 digits x 25 digits (640 x 400 dots).
Traditionally used as a display
Large-sized devices with display capabilities comparable to CRTs have been commercialized. For such large displays, we use a so-called zebra-type material, which is made by alternately laminating conductive silicone rubber and insulating silicone rubber, which are silicone rubber mixed with and dispersed with carbon black, and equipped with an IC to drive the display. There is a method of connecting printed wiring boards that have been made smaller, but since reducing the connection pitch causes problems with alignment and connection resistance, it is impossible to reduce the size beyond a certain level.
Furthermore, since such connectors must be held in a compressed state, if the display device becomes larger, the entire holding mechanism must be large and robust, which is disadvantageous in that it cannot be expected to be lighter or thinner. .

In contrast, by using an anisotropic conductive heat connector in which conductive components such as metal powder, graphite powder, carbon fiber, etc. are blended and dispersed in a low-melting thermoplastic resin, the zebra Although some attempts have been made to overcome the disadvantages of type connectors, connections using these types of
℃), the adhesion strength is extremely reduced, and to compensate for these weaknesses, it is necessary to add a mechanism to compress and hold the connected parts. It is necessary to use conductive components with a diameter of several tens of micrometers, and since these components are randomly mixed, the insulation between adjacent electrodes may be impaired in minute pitches. This has the disadvantage of causing defects due to lateral conduction, and the connection pitch is said to be limited to 0.2mm.

Regarding this connection, as shown in FIG.
A TAB method is also known in which a copper foil 14 is attached to a long polyimide film 13 and etched to form a conductive wire for connection to a wiring board. This has high positioning accuracy because the conductor wires are aligned with the IC chip and wiring board all at once.
In addition to having the advantage of shortening the work time required for connection, this conductor 7 also reduces the stress caused by the difference in thermal expansion coefficient between the IC chip and the wiring board to which it is connected.
However, on the other hand, it is necessary to provide protruding electrodes (bumps) on the bonding pad of the IC chip in advance by plating, or to etch the part of the conductor that connects to the IC chip. Therefore, a convex portion must be formed,
It is inevitable that costs will increase, such as by lowering the product yield of IC chips. Furthermore, when bonding the outer leads of TAB-IC to a glass substrate, the ITO film pattern on the glass substrate must be
It is necessary to make it bondable by plating with metal such as Cr, Ni, Au, etc., which is not satisfactory in terms of cost.

Note that the above method requires space for the package, conductors, etc. in addition to the IC chip.
Since it was not possible to make electronic equipment small and lightweight, the IC chip 1 was developed as shown in Figure 4.
A flip-chip method has been proposed in which bumps 15 made of solder alloy are provided on bonding pads 12 of 1 and electrically connected to electrodes 17 on a wiring board 16 so that the mounting area is approximately equal to the size of an IC chip. However, with this method, as the number of solder bumps increases, their characteristics and shapes vary, and the bonding strength also becomes uneven depending on the flatness of the wiring board. There is a disadvantage that the stress caused by the difference in thermal expansion coefficient between the board and the IC chip may destroy the solder bumps, making it difficult to say that the connection is electrically reliable. In order to achieve this, the above-mentioned plating process is required, and it is difficult to achieve both size reduction and cost reduction.

Furthermore, as a method for directly mounting an IC chip on a glass substrate, for example, holes are made in a plastic film such as polyimide film to match the bonding pads of the IC chip, and the holes are filled with a conductive elastomer containing carbon black. The conductive rubber connector we made was connected to a glass substrate.
A method has been proposed in which the chips are placed between the IC chips, aligned, and then fixed with a spring-loaded presser metal fitting. Because of the disadvantage that the mold etc. are very expensive, a satisfactory method of directly mounting IC chips on a glass substrate has not yet been established.

Therefore, the present inventors proposed a semiconductor device in which the bonding pads of an IC chip and the electrodes of a wiring board are connected via elastic conductive protrusions (rubber bumps) (Japanese Patent Application No. 61-299639). According to this method, the connection between the IC chip and the wiring board is easy and the working time is shortened, and a thinner structure is achieved with high reliability.
In this case, the rubber pads are formed by applying a conductive ink containing a conductive rubber composition that exhibits rubber elasticity after curing to the surface of the IC chip, and then forming an opening similar to the arrangement of the bonding pad on the surface of the IC chip. A mask plate made of a metal plate, such as a nickel plate or a stainless steel plate, is aligned and overlapped with the bonding pad, and then the openings of this mask plate are spot-heated with a xenon lamp, halogen lamp, etc., or the openings are The conductive ink layer facing this opening is cured by spot irradiation with ultraviolet light from a mercury lamp, and then the mask plate is removed and the uncured conductive ink layer is exposed to the area not in contact with the bonding pad. Either use a solvent to remove the conductive ink, or screen print the conductive ink described above on the opening of the mask plate aligned and stacked on the surface of the IC chip, remove the mask plate, and cure or dry the conductive ink. Since it is produced by this method, it has the disadvantage of being industrially quite difficult. In other words, for the screen plate used for this, the printed rubber bumps require a high degree of positional accuracy of about ±5 μm, and the height must be 20 to 50 μm, so we used nickel or stainless steel plates. It is said that it is preferable to use a screen plate that has been patterned by drilling holes at predetermined positions using the etching method, but it is difficult to align the screen plate with high precision with respect to the IC chip using this method. I understand. In other words, since this screen plate uses a metal plate like the one described above, it is not possible to align the bonding pads of the IC chip to be printed by looking through them, and furthermore, in order to perform screen printing, is the substrate to be printed
At least 1 unit between the IC chip and the screen version
It is necessary to provide a clearance of about mm, but even if the alignment is completed with the clearance, the squeegee will print while stretching the screen plate by the amount equivalent to this clearance with a certain printing pressure. However, it is not possible to reproduce the stretched state of the screen plate, and the alignment is insufficient, so it must be said that it is difficult to obtain high-quality printed matter of about ±5 μm as described above using this method. I don't get it.

(Structure of the Invention) The present invention relates to an improvement in a method for connecting an IC chip bonding pad and a wiring board using this elastic conductive protrusion. An ink layer is printed, and it is brought into contact with an input/output terminal of a semiconductor integrated circuit chip or an electrode of a wiring board and heated, and the conductive ink layer is used as an elastic conductive protrusion to be applied to an input/output terminal of a semiconductor integrated circuit or an electrode of a wiring board. After being transferred onto the electrodes of the wiring board, the easily peelable film is peeled off, and then the electrodes of the wiring board or the input/output terminals of the semiconductor integrated circuit are brought into contact with the film and heated.

That is, the present inventors solved the above-mentioned disadvantages in the method of connecting input/output terminals of a semiconductor integrated circuit chip and electrodes of a wiring board using elastic conductive protrusions (hereinafter referred to as rubber bumps). As a result of various studies on methods, we found that openings similar to the bonding pads of IC chips or electrodes on wiring boards were created on easily peelable films such as polyethylene resin and polypropylene resin using a chemical etching method. After injecting a conductive ink that exhibits a rubber-like elastic body when cured into the opening of the metal plate, a conductive ink layer is provided at the same position as the bodying pad or electrode of the easily peelable film. When this is brought into contact with an IC chip or wiring board and hot pressed from the back side, this conductive ink layer hardens and becomes a rubber bump, and this is transferred onto the IC chip or wiring board, so that an easily peelable film is formed. When the IC chip and wiring board are peeled off and then brought into contact with each other and heated, this rubber bump melts and is bonded and integrated with the IC chip or wiring board, so that the IC chip and wiring board are completely electrically connected via this rubber bump. The present invention was completed by conducting research on the composition of the easily peelable film and conductive ink to be used in this process.

This will be explained below based on the attached drawings. FIG. 1a is a longitudinal cross-sectional view showing the connection between an IC chip and a wiring board in which rubber bumps are formed on the IC chip by the method of the present invention, and FIG. 1 is a longitudinal cross-sectional view showing the connection between an IC chip and a wiring board in which rubber bumps are formed on the wiring board by the method of the present invention. In the IC chip 1 shown in FIG. 1a, a rubber bump 3 is bonded and integrated with a bonding pad 2 existing on the surface thereof by the method described above.
This is in contact with the electrodes of the wiring board 4, and these are sealed with a sealing resin 6 to form a semiconductor device. In FIG. This is brought into contact with the bonding pad 2 of the IC chip 1.

The method for installing the rubber bumps 3 on the easily peelable film is, for example, as shown in FIG. A metal plate made of nickel, stainless steel, etc. is provided with openings made by chemical etching at the same positions as the bonding pads or electrodes on the wiring board, and conductive ink is injected into the openings to coat the film. After providing a conductive ink layer on the surface, hot pressing may be performed.

The semiconductor integrated circuit chip used in the method of the present invention is provided with conventionally known bonding pads.
It may be an IC chip, and this wiring board may also be a known one, such as a flip-chip method, a TAB
Glass substrates such as LCDs, which cannot be connected using conventional chip-on-board methods, may be used, but copper-clad epoxy resin laminates, copper-clad polyimide resin laminates, copper-clad polyimide A conventionally used wiring board such as a resin film may be used.

Furthermore, the conductive ink forming the rubber bumps used in the method of the present invention forms an elastic conductive rubber layer and is required to be adhesively integrated with the IC chip or wiring board when heated. , ethene-vinyl acetate copolymer resin (EVA),
Thermoplastic resins such as ethylene-ethyl acrylate copolymer resin (EEA), ionomer resin, styrene-butadiene copolymer resin, vinyl acetate resin, acrylic resin, polyester resin, vinyl chloride resin, flexible epoxy in B-stage state These include resins, thermoplastic resins such as silicone rubber, synthetic rubbers, etc. These include metal powders such as gold, silver, copper, and nickel, or powders of their alloys, carbon-based conductive powders such as ketschen black, graphite, etc. Alternatively, it may be made of glass beads whose surface is plated with gold or nickel, etc., to which 10 to 60% by volume is added as a conductivity imparting agent, and in addition, known organic peroxides, Addition of curing agents such as acid anhydrides and amines, primer compositions for adhering these rubber components to plastics, metals, glass, etc., ultraviolet sensitizers, photoinitiators, anti-aging agents, antioxidants, etc. It is preferable that the

Further, for this easily peelable resin film, in addition to polyethylene resin, polypropylene resin, polyurethane resin, epoxy resin, and Teflon resin, polyarylate resin and polyimide resin may be used as those having particularly little dimensional change.

As described above, the method of the present invention involves contacting an IC chip or a wiring board with an easily peelable film provided with a conductive ink layer at positions corresponding to the bonding pads or electrodes of the IC chip, and curing the film. After making the rubber bumps, the easily peelable film is peeled off, and then the film is bonded and integrated with the IC chip or wiring board. Not only can alignment be done easily, but this method also eliminates the need for clearance unlike screen printing.
It is possible to align with the bonding pad of the IC chip with high precision, and if you use something like a screen plate that is glued under tension to the metal holding frame 10, it is possible to use a rubber-like conductive pad when forming bumps. Dimensional changes in this easily peelable film due to heat stress applied when curing the resin or transferring the conductive rubber bumps to an IC chip can be minimized. Further, since such an easily peelable film can suppress dimensional changes to a low level, it can be used repeatedly many times, which undoubtedly contributes to cost reduction.

Note that the semiconductor device obtained in this way is
Because it is packageless, the area it occupies is equal to the size of the IC chip, so electronic components using this method can be made smaller.・Although it was not possible to perform screening, this method provides the convenience of easily conducting inspection screening because it is possible to easily establish continuity with an external circuit by applying appropriate pressure. In addition, since the conductive rubber bumps have rubber elasticity, even if the thermal expansion coefficients of the IC chip and the glass substrate do not match, the bumps absorb the stress and the conductive paths are not destroyed. High reliability is obtained,
Furthermore, even if the glass substrate has poor flatness,
This can also be followed by rubber elasticity,
Furthermore, this connection method has the advantage that it has an extremely simple configuration and can be manufactured at low cost.

Next, examples of the present invention will be given, and parts in the examples indicate parts by weight.

Example: Polyimide film Kapton V with a thickness of 50 μm
Type 200V [trade name manufactured by Toray DuPont Co., Ltd.] is tension-bonded to the aluminum frame for the screen plate at 10 kg/cm ² , and then chemically etched holes similar to the bonding pads for IC chips on the nickel plate are made on this surface. A screen plate with holes made by the method was prepared, and 60 parts of styrene-ethylene-butadiene-styrene copolymer resin Kraton-G1657 (trade name, manufactured by Ciel Chemical Co., Ltd.) and tempelphenol as a tackifier were added. Polymer resin - YS Polyster T115 [trade name manufactured by Yasushi Oil Industries Co., Ltd.] 40 parts, amine-ketone resin as an anti-aging agent - Nokrac AW-N [trade name manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.] 2 parts After dissolving in an appropriate amount of toluene, make nickel powder of less than 350 mesh
700 copies, carbon black/button black
Add 10 parts of EC (trade name manufactured by Lion Akzo Co., Ltd.), mix in a crusher, knead with three rolls, inject the obtained conductive ink, and print a conductive ink layer on the polyimide film. After that, heat it at 120℃ for 30
The conductive ink layer was cured into a rubber bump by heating for 20 minutes.

Next, when the rubber bump layer of this polyimide film was bonded to the IC chip, the rubber bump layer was bonded to the bonding pad of the IC chip, so after peeling off the polyimide film, a glass substrate was placed on top of this and the electrode section on the glass substrate. When the rubber bump layer was bonded to the rubber bump layer and a hot plate heated to 150℃ was pressed against it, the rubber bump melted and was integrated into the bonding pad of the IC chip. When a mixture of Araldite AY101 [trade name manufactured by Nippon Ciba Geigy Co., Ltd.] and curing agent HY950 [trade name manufactured by the same company] was dropped and sealed,
A semiconductor device was obtained in which the conductive adhesion was made stronger by the rubber bump layer described above.

[Brief explanation of the drawing]

FIGS. 1a and 1b are longitudinal cross-sectional views of a semiconductor device obtained by the method of the present invention, and FIG. 3 and 4 are longitudinal cross-sectional views of a method of mounting an IC chip using a conventionally known method. 1 , 11 ...IC chip, 2,12...Bonding pad, 3...Rubber bump, 4,6...
Wiring board, 5, 17... Electrode, 6... Sealing resin, 7... Easily peelable film, 8... Metal holding frame, 13... Polyimide film, 14... Copper foil, 15... Solder Alloy bump.

Claims (1)

[Claims] 1. A conductive ink layer is printed on an easily peelable film, and this is brought into contact with input/output terminals of a semiconductor integrated circuit chip or electrodes of a wiring board and heated to form an elastic conductive protrusion. The film is transferred onto the input/output terminals of a semiconductor integrated circuit or the electrodes of a wiring board, the easily peelable film is peeled off, and then the electrodes of the wiring board or the input/output terminals of the semiconductor integrated circuit are brought into contact with the film and heated. A method for connecting semiconductor devices.