JPH11330299A - Bare chip mounting board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bare chip mounting board which is highly reliable in electrical connection, even when heated. SOLUTION: A bare chip mounting board consists of an IC chip 2 and a mounting board 4, which are electrically connected through an anisotropic conductive film 1. The bare chip mounting board is provided with at least one through-hole 5, which communicates with the external from a region surrounded by a wiring pattern 3 on the mounting board 4. Even if a micro-void exists between the IC chip 2 and the mounting board 4, since the expanded air in the heated condition goes out through the through-hole 5, a high heat resistant connection reliability can be obtained even during high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bare chip mounting board, and more particularly, to a bare chip mounting board for electrically connecting an IC chip and a mounting board via an anisotropic conductive film.

[0002]

2. Description of the Related Art With the recent increase in the number of functions and reduction in size and weight of electronic devices, in the field of semiconductors, patterns of wiring circuits have been highly integrated, and fine patterns with a large number of pins and a narrow pitch have been adopted. It has become.

In order to cope with such a fine circuit pattern, a plurality of conductor patterns formed on a substrate and I
C. Anisotropic conductive films have begun to be used for connection to LSIs.

As the anisotropic conductive film, a film having a structure in which conductive fine particles are dispersed in an adhesive film is known. However, the anisotropic conductive film having this structure has a problem in that the conductive fine particles are mixed into the adhesive film by dispersion, so that the reliability of the electrical connection at a narrow pitch is lacking.

To cope with the narrow pitch, Japanese Patent Application No. 9-117244 discloses an anisotropic conductive film in which a conductive path made of a conductive material is provided so as to penetrate the insulating film in the thickness direction. And a method for producing the same have been proposed.

A typical method for electrically connecting an IC chip to a mounting board using the anisotropic conductive film manufactured by this method is, for example, one having a structure as shown in a sectional view in FIG. Is mentioned. By mounting the element with the anisotropic conductive film 1 interposed therebetween, a large number of electrodes on the minute bare chip 2 and the wiring pattern 3 on the external substrate 4 are formed.
And can be connected. In this way, the problem that the reliability of the electrical connection at the narrow pitch is lacking has been solved.

However, the bare chip mounting substrate manufactured by this method has microvoids between the anisotropic conductive film 1 and the mounting substrate 4, and is connected by expansion of air in the voids during heating in an environmental test. The reliability of the device decreases. Therefore, it is necessary to develop a bare chip mounting board with high electrical connection reliability even during heating.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a bare chip mounting substrate having high reliability of electrical connection even during heating.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have provided at least one through hole communicating from a portion surrounded by a wiring pattern on a mounting board to the outside. This proved that the reliability of the electrical connection was high even during heating. That is, the present invention is as follows. I electrically connected through an anisotropic conductive film
What is claimed is: 1. A bare chip mounting board comprising a C chip and a mounting board, wherein at least one through hole is provided to communicate from a portion surrounded by a wiring pattern on the mounting board to the outside. 3. The bare chip mounting board according to claim 1, wherein the through-hole is a through-hole passing through the thickness direction of the board. The anisotropic conductive film is disposed in a film substrate made of an insulating material in a state where at least one conductive path made of a conductive material is insulated from each other and penetrates the film substrate in a thickness direction. The bare chip mounting substrate according to or, wherein each of the conduction paths has both ends exposed on the front and back surfaces of the film substrate.

[0010]

According to the present invention, at least one through-hole is provided which leads from the portion surrounded by the wiring pattern on the mounting board to the outside even if air expands in the microvoid during heating. Since the air expanded through the through holes escapes to the outside, the reliability of the electrical connection can be maintained high.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 is a schematic diagram showing an example of a bare chip mounting board according to the present invention. In the embodiment shown in FIG. 1, the IC chip 2 and the mounting substrate 4 having the wiring pattern 3 are electrically connected by the anisotropic conductive film 1. The mounting board 4
There is a hole 5 through which air expanded in the microvoid is released by heating.

In this specification, a bare chip refers to a bare (naked) IC chip that is not packaged.

Anisotropic conductive film 1 used in the present invention
The type is not particularly limited as long as it has anisotropic conductivity, and has a structure in which conductive fine particles are dispersed in an adhesive film, or is made of a conductive material so as to penetrate in the thickness direction of the insulating film. One having a structure provided with a conduction path is exemplified. The preferred anisotropic conductive film 1 has a structure in which a conductive path made of a conductive material is provided so as to penetrate in the thickness direction of the insulating film. When such an anisotropic conductive film is used, the electrical connection at a narrow pitch is highly reliable.

Examples of the insulating adhesive material constituting the anisotropic conductive film substrate used for the bare chip mounting substrate of the present invention include materials that can be used as the film substrate of the anisotropic conductive film, and known materials are used. do it. Since the anisotropic conductive film 1 used for the bare chip mounting board of the present invention is used for bonding the printed board and the IC chip, it is necessary to use an adhesive material. Further, in order to exhibit anisotropic conductivity, the insulating adhesive material needs to have sufficient insulating properties. Examples of the material having adhesiveness include known adhesive materials such as thermosetting resins and thermoplastic resins. Specifically, phenol-based, biphenyl-based epoxy resin, acrylic resin,
Thermosetting resins such as polycarbodiimide resin and polyurethane resin, phenoxy resin, nylon 6, nylon 6,
And polyamide resins such as PET and PBT, polyimide resins such as polyamideimide resins, and thermoplastic resins such as fluororesins and polyetherimide resins, which are appropriately selected according to the purpose.
These resins may be used alone or in combination of two or more. Glass transition point is preferably 150 ° C. or higher and 230 ° C.
The following adhesive materials are used. If the glass transition point is 150 ° C. or higher, the bonding reliability between the semiconductor element and the circuit board can be further improved. If the glass transition point is 230 ° C. or lower, workability is excellent.

The shape of the anisotropic conductive film 1 is not particularly limited as long as electrical connection can be made between the IC chip 2 and the mounting board 4, and may not be the same shape as the IC chip 2. For example, a shape in which a central portion is cut may be used.

The conductive path is provided so as to penetrate at least in the thickness direction of the film and to expose both ends on the front and back surfaces of the film substrate. The material of the conduction path is not particularly limited as long as it has conductivity, and examples thereof include metal materials such as copper, gold, aluminum, and nickel, and these metal materials and polyimide resin, epoxy resin, acrylic resin, and fluorine resin. , A conductive polymer material such as polyacene, and the like. The conductive material is appropriately selected depending on the application, but a metal material is preferable in terms of electrical characteristics, and copper and gold are particularly preferable in terms of conductivity.

The method of manufacturing an anisotropic conductive film having a structure in which a conductive path made of a conductive material is provided so as to penetrate in the thickness direction of the insulating film is not particularly limited. For example, a through hole is formed in an adhesive film. A method of filling a metal hole by plating or forming a coating layer on a thin metal wire using an insulating material, winding this in a core material in a roll shape, heating and / or
Alternatively, the coating layers are fused together and / or
Alternatively, there is a method in which a blade is inserted in the axial direction of the roll-shaped material by pressing and pressing.

The type of the mounting substrate 4 used in the present invention is not particularly limited, and for example, a glass epoxy substrate, a ceramic substrate, a flexible substrate made of a polyimide resin or the like can be used.

The wiring pattern 3 is printed on the mounting board 4. The wiring pattern 3 is formed of a conductor such as copper. The wiring pattern 3 is generally formed so as to surround the outer edge of the mounting portion 6 of the IC chip 2 as shown in the front view of FIG.

In the present invention, the through-hole 5 provided in the portion of the mounting substrate 4 surrounded by the wiring pattern 3 includes:
If the air that has expanded in the microvoids escapes, the air that passes through the wiring pattern 3 in the width direction, the air that passes through the thickness direction of the substrate 4, Reaching either end of the
Any of those that penetrate the wiring pattern 3 and reach the upper surface of the mounting substrate 4 may be used. A preferable through hole is a through hole penetrating in the thickness direction of the substrate for ease of production.

The through-hole is preferably provided so as to avoid the wiring pattern 3, and is further preferably provided at a position separated from the wiring pattern 3 by 1 mm or more. This is because, if the wiring pattern 3 or the through hole is provided less than 1 mm from the wiring pattern 3, the wiring may be damaged or corroded.

The method of providing the through-hole is not particularly limited, and may be a known method, for example, a mechanical processing method such as punching or drilling, a dry etching method using laser, plasma or the like. In particular, when a through hole is provided in the substrate, it is preferable to use a mechanical processing method such as punching or drilling from the viewpoint of cost. The shape of the through-hole is not particularly limited, and may be any shape such as a circle, a polygon such as a square or a rhombus.

The diameter of the through hole (hole diameter) is usually about 50 to 1000 μm, preferably 100 to 30 μm, in terms of the diameter of the opening.
It is about 0 μm. If the diameter of the through-hole is smaller than 50 μm, there is a possibility that the air expanded in the microvoid between the bare chip and the mounting board may not be able to escape.If the diameter of the through-hole is larger than 1000 μm, moisture or There is a possibility that foreign matter may enter, which is not preferable.

The number of through holes may be one or more depending on the size of the IC chip and the like, and can be appropriately determined in consideration of the strength of the substrate 4 and the wiring pattern 3.

[0025]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

Example 1 A mounting in which a wiring pattern of copper wires (gold plating) is formed at a pitch of 100 μm on a glass epoxy substrate (FR-4), and one through hole having a diameter of 200 μm is provided at the center of the IC chip mounting portion. An IC chip was mounted on a substrate using a bare chip using an anisotropic conductive film. IC chip is 10mm
A size of × 10 mm was used. The anisotropic conductive film is an imide-based insulating film (polycarbodiimide resin) in which copper is used as a conductive material for a conductive layer, and a gold (Au) layer is provided on the outermost surface of copper. Is I
The same 10mm × 10mm size as the C chip and the thickness is 7
The thing of 0 μm was used. The connection between the IC chip and the mounting board is performed using a flip chip bonder at a set temperature of 2
The test was performed at 70 ° C. under a pressure of 30 kg / cm for 60 seconds. The obtained bare chip mounting board has a pattern connection probability of 100%.
Showed a good connection state with a connection resistance value of 20 mΩ or less. This bare chip mounting board was subjected to a pressure cooker test (hereinafter referred to as “PCT”) (121 ° C., 100% R
(H, 2 atm). After standing for 100 hours in an atmosphere, the connection reliability was evaluated. As a result, an initial good connection state having a connection resistance value of 20 mΩ or less was maintained at a pattern connection probability of 100%.

Example 2 An anisotropic conductive film having a size of 10 mm × 10 m
A bare chip mounting board was obtained in the same manner as in Example 1 except that a square-shaped one having an m size and having a 3 mm × 3 mm opening in the center of the film was used. The obtained bare chip mounting board had a pattern connection probability of 100% and exhibited a good connection state with a connection resistance value of 20 mΩ or less. This bare chip mounting board is mounted on a PCT (121 ° C, 100% R
(H, 2 atm). After standing for 100 hours in an atmosphere, the connection reliability was evaluated. As a result, an initial good connection state having a connection resistance value of 20 mΩ or less was maintained at a pattern connection probability of 100%.

Example 3 A mounting in which a wiring pattern of copper wires (gold plating) is formed at a pitch of 350 μm on a glass epoxy substrate (FR-4), and one through hole having a diameter of 300 μm is provided at the center of the IC chip mounting portion. An IC chip was mounted on a substrate using a bare chip using an anisotropic conductive film. IC chip is 10mm
A size of × 10 mm was used. The anisotropic conductive film is formed by adding metal particles (nickel particles, average particle diameter 5μ) to an epoxy resin material (bisphenol epoxy resin).
m) is dispersed, and the size is the same as the IC chip.
One having a size of 0 mm × 10 mm and a thickness of 150 μm was used. The connection between the IC chip and the mounting board is performed using a flip chip bonder at a set temperature of 200 ° C and a pressure of 3
The test was performed at 0 kg / cm for 60 seconds. The obtained bare chip mounting board had a pattern connection probability of 100% and exhibited a good connection state with a connection resistance value of 20 mΩ or less. This bare chip mounting board is mounted on a PCT (121 ° C., 100% RH, 2 at
m) After standing for 72 hours in an atmosphere and evaluating the connection reliability, the connection resistance value was 20 with a pattern connection probability of 100%.
The initial good connection state of mΩ or less was maintained.

Comparative Example 1 A bare chip mounting board was obtained in the same manner as in Example 1 except that no through-hole was provided in the IC mounting portion of the glass epoxy resin substrate. The obtained bare chip mounting board had a pattern connection probability of 100% and exhibited a good connection state with a connection resistance value of 20 mΩ or less. This bare chip mounting board is PCT
(121 ° C., 100% RH, 2 atm)
It was left for 0 hours, and the connection reliability was evaluated. As a result, the connection resistance value was 20 mΩ or less with a pattern connection probability of 95%, and a connection failure of 5% occurred.

Comparative Example 2 A bare chip mounting substrate was obtained in the same manner as in Example 2 except that no through-hole was formed in the IC mounting portion of the glass epoxy resin substrate. The obtained bare chip mounting board had a pattern connection probability of 100% and exhibited a good connection state with a connection resistance value of 20 mΩ or less. This bare chip mounting board is PCT
(121 ° C., 100% RH, 2 atm)
It was left for 0 hours, and the connection reliability was evaluated. As a result, the connection resistance value was 20 mΩ or less at a pattern connection probability of 90%, and a connection failure of 10% occurred.

Comparative Example 3 A bare chip mounting substrate was obtained in the same manner as in Example 3 except that no through-hole was formed in the IC mounting portion of the glass epoxy resin substrate. The obtained bare chip mounting board had a pattern connection probability of 100% and exhibited a good connection state with a connection resistance value of 20 mΩ or less. This bare chip mounting board is PCT
(121 ° C., 100% RH, 2 atm)
After leaving it for a time and evaluating the connection reliability, the connection resistance value was 20 mΩ or less with a pattern connection probability of 95%.
5% connection failure occurred.

In the example, the connection reliability was good, but in the comparative examples, connection failure occurred in all cases.

[0033]

According to the bare chip mounting board of the present invention, at least one through-hole is provided which extends from the portion surrounded by the wiring pattern on the mounting board to the outside, so that the micro chip is provided between the IC chip and the mounting board. Even if voids exist,
Since the air expanded in the heated state can escape to the outside from the through-hole, high heat-resistant connection reliability can be obtained even at a high temperature.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a bare chip mounting board according to the present invention.

FIG. 2 is a schematic view showing a cross section of an example of a conventional bare chip mounting board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anisotropic conductive film 2 IC chip 3 Wiring pattern 4 Mounting board 5 Through hole 6 IC chip mounting part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fumiki Asai 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (3)

[Claims] 1. A bare chip mounting board comprising an IC chip and a mounting board which are electrically connected via an anisotropic conductive film, wherein the bare chip mounting board communicates with a portion surrounded by a wiring pattern on the mounting board to the outside. A bare chip mounting board, wherein at least one through hole is provided. 2. The bare chip mounting board according to claim 1, wherein said through hole is a through hole penetrating in a thickness direction of said board. 3. The anisotropic conductive film has a structure in which at least one conductive path made of a conductive material is insulated from each other in a film substrate made of an insulating material and penetrates the film substrate in a thickness direction. The bare chip mounting board according to claim 1, wherein both end portions of each conductive path are exposed on the front and back surfaces of the film substrate.