JPH0837206A - Method of manufacturing semiconductor device - Google Patents

Abstract

PURPOSE:To enhance reliability in bump connection by reducing variation of the size of bumps in a mounting method of a flip-chip method. CONSTITUTION:A conductive adhesive sheet 1 having B stage characteristics is punched in a solid in a solid state of a low temperature to form a small piece, which is placed on terminals 7 of a heated circuit board 6 and softened and connected to the terminal 7 by generated adhesion to form a bump 8. Next, the electrode pads of a semiconductor chip 11 are positioned on the bumps 8 and placed to heat at 120 to 200 deg.C so that they are connected to each other from a liquefied state to a thermset state, whereby the sizes of the bumps are made uniform to prevent short-circuit between terminals and connection failure between the bumps and electrode pads.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing method, and more particularly to a semiconductor chip mounting method.

[0002]

2. Description of the Related Art A flip chip method using bumps is one of the methods for mounting semiconductor chips.

FIG. 4 shows a first method of manufacturing a conventional semiconductor device.
3 is a schematic cross-sectional view for explaining an example of FIG.

As shown in FIG. 4, solder bumps 15 are formed on the pad electrodes 12 formed on the semiconductor chip 11 by plating or vapor deposition, and the solder bumps 15 are aligned with the terminals 7 formed on the circuit board 6. Then, the semiconductor chip 11 is mounted and the solder bumps 15 are reflowed to be bonded to the terminals 7. A polyimide film 16 is provided on the surfaces of the semiconductor chip 11 and the circuit board 6 for protection.

FIG. 5 shows a second method of manufacturing a conventional semiconductor device.
3 is a schematic cross-sectional view for explaining an example of FIG.

As shown in FIG. 5, the structure is the same as that of the first example except that the Cu balls 17 are put in the solder bumps 15. The solder bumps 15 are reflowed and bonded to the terminals 7. At this time, there is an advantage that the distance between the semiconductor chip 11 and the circuit board 6 can be set by using the Cu balls 17 as spacers.

[0007]

In this conventional method for manufacturing a semiconductor device, since the solder bumps are formed by plating, vapor deposition, sputtering, etc., variations in the plating conditions and the size or film thickness of the opening of the mask. 6A and 6B, due to the influence of variations in the size of the solder bumps, excess solder of the solder bumps 15 flows out as shown in FIG. 6, and the distance between the bumps is particularly small in devices that have been miniaturized recently. Therefore, there has been a problem that short-circuiting between terminals occurs, or bump heights become uneven, causing a connection failure with some electrode pads.

An object of the present invention is to provide a method of manufacturing a semiconductor device in which the size of bumps is kept constant to prevent the occurrence of short circuits between terminals and defective connections.

[0009]

According to a first method for manufacturing a semiconductor device of the present invention, a conductive adhesive sheet having a conductive resin having B-stage characteristics formed in a sheet shape is selectively cut in a solid state at a low temperature. And forming a small piece, a step of forming the bump by bonding the small piece onto a terminal of the circuit board heated to a temperature at which the small piece is softened and exhibits adhesiveness, and an electrode of a semiconductor chip on the bump. The step of aligning and placing pads, heating and curing the bumps, and electrically connecting the terminals of the circuit board and the electrode pads of the semiconductor chip via the bumps is included.

A second method of manufacturing a semiconductor device according to the present invention is
A step of selectively cutting a laminated metal sheet having a solder film or a metal film formed on both sides of a metal sheet to form a small piece; and a step of placing the small piece on a terminal of a circuit board and reflowing to form a bump And the electrode pads of the semiconductor chip are aligned and placed on the bumps, the bumps are heated and reflowed to be joined, and the terminals of the circuit board and the electrode pads of the semiconductor chip are electrically connected via the bumps. And a step of connecting.

[0011]

Next, the present invention will be described with reference to the drawings.

FIGS. 1A to 1D are schematic sectional views showing the steps in order to explain the first embodiment of the present invention.

First, as shown in FIG. 1A, a conductive material formed into a sheet or tape having a thickness of 10 to 50 μm by mixing fine particles of metal such as Ag into a resin such as epoxy having a B-stage characteristic. A die 2 of a punching machine which holds the adhesive sheet 1 in a low temperature solid state and has a die 2 and a punch 3.
Attach it to and fix it.

Here, the B stage characteristic means a solid state at room temperature or lower, a tackiness at a temperature of 40 to 80 ° C. above room temperature, liquefaction at 100 to 200 ° C., and thermosetting with heating time. It is a characteristic.

Next, as shown in FIG. 1B, the punch 3
Is driven to punch a small piece 4 from the conductive pressure sensitive adhesive sheet 1 mounted on the die 2, and is mounted on the stage 5 for 40 to 5
The small piece 4 was aligned with the terminal 7 of the circuit board 6 heated to 0 ° C., and the small piece 4 was pressure-bonded to the terminal 7 with a small load (about 0.1 to 5 g), and the circuit board 6 was heated to produce tackiness. Small piece 4
Are bonded and fixed to the terminals 7 to form bumps 8.

Next, as shown in FIG. 1C, the ball bumps 13 formed on the pad electrodes 12 of the semiconductor chip 11 are formed.
Are aligned so as to face the bumps 8 formed on the circuit board 6.

Next, as shown in FIG. 1D, the ball bumps 13 of the semiconductor chip 11 are pressure-bonded to the bumps 8 softened by the heating of the stage 5 and then the bumps 8 to 120-2.
The ball bumps 13 and the bumps 8 are joined by heating to 00 ° C. and changing from liquefaction to thermosetting. In this way, by using the conductive resin, it is possible to prevent a short-circuit accident due to the flow-out of the bonding material because the flux for bonding the metal bumps is not required and the amount of the bonding material can be controlled. .

FIG. 2 is a schematic sectional view for explaining the second embodiment of the present invention.

As shown in FIG. 2, the tape-shaped conductive adhesive sheet 1 mounted by the cutting table 14 and the die 2 is sequentially cut in the solid state at low temperature by the punch 3a having the vacuum chuck function to form the small pieces 4. Punch 3 at the same time
It is adsorbed to a and held.

Thereafter, the punch 3a is transferred to the circuit board heated on the stage, and the small pieces 4 are pressure-bonded to the terminals of the circuit board to generate viscosity and adhere to form bumps as in the first embodiment. To do.

In the second embodiment, the electroconductive pressure-sensitive adhesive sheet 1 can be used without waste and the cost can be reduced as compared with the punching method.

3 (a) and 3 (b) are schematic sectional views showing the steps in order to explain the third embodiment of the present invention.

As shown in FIG. 3A, Au, Cu, A
10 to 10 μm in thickness of the metal sheet 9 having a thickness of 10 to 100 μm and the conductive resin films 10 having the B-stage characteristics on both sides.
A conductive adhesive sheet having a laminated structure formed to a thickness of 50 μm is punched with a punch 3 to form a small piece, which is mounted on a stage 5 and adhered to a terminal 7 of a circuit board 6 heated to 40 to 50 ° C. 8a is formed.

Next, as shown in FIG. 3B, the pad electrodes 12 of the semiconductor chip 11 and the bumps 8a are aligned and pressure-bonded, and the bumps 8a are heated to 120 to 200 ° C. to be hardened, and the pad electrode is then applied. 12 and the bump 8a are joined.

In this embodiment, the space between the semiconductor chip 11 and the circuit board 6 can be widened by interposing the metal sheet 9, and the heat generated by the difference in the coefficient of thermal expansion between the semiconductor chip 11 and the circuit board 6 can be increased. There is an advantage that durability against stress can be improved.

Incidentally, B described in the first to third embodiments
As the conductive material mixed in the conductive resin having the stage characteristics, in place of Ag, fine particles of Cu, Au, solder or the like, or at least one kind of metal particles plated on the surface of fine plastic particles are mixed. You may use it.

Further, Pb-Sn is formed on both surfaces of a metal sheet made of Au, Cu, Al, Ni or the like and having a thickness of 30 to 100 μm.
Alloy, Au-Sn alloy, Ag-Sn alloy, Au, Al,
A laminated metal sheet in which a metal film of In or the like is formed to have a thickness of 5 to 50 μm may be used. In this case, a small piece formed by punching or cutting from the laminated metal sheet is applied to the terminals of the circuit board to adhere the flux. To form a bump by the first reflow (wetback), and the electrode pad of the semiconductor chip and the bump on the circuit board are combined with each other through the flux applied on the bump to perform the second reflow. Bond the electrode pads and bumps.

Here, the combination of the material of the metal sheet and the material of the metal film formed on both surfaces of the metal sheet needs to take the barrier property between the metals into consideration. As a suitable example, Pb-
Sn alloy / Cu / Pb-Sn alloy, Pb-Sn alloy / N
The combination of i / Pb-Sn alloy, Au / Ni / Au, etc. can be mentioned.

A barrier metal film may be provided between the terminals of the circuit board and the bumps or between the electrode pads of the semiconductor chip and the bumps.

[0030]

As described above, according to the present invention, a conductive adhesive sheet made of a conductive resin having a B-stage characteristic is cut into small pieces and bonded to terminals of a circuit board to form bumps. It is possible to set the thickness and the amount thereof to be constant, and it is possible to prevent a short circuit between terminals due to the flow-out of the conductive adhesive and a connection failure due to uneven bump heights.

Further, in the case where a metal layer is provided as an intermediate layer of the bump, the metal layer serves as a core to set a constant gap between the semiconductor chip and the circuit board, and the gap can be increased by changing the thickness of the metal layer. The thickness can also be set arbitrarily, and the effect of thermal stress due to the difference in thermal expansion coefficient between the semiconductor chip and the circuit board can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the order of steps for explaining a first embodiment of the present invention.

FIG. 2 is a schematic sectional view for explaining a second embodiment of the present invention.

3A to 3D are schematic cross-sectional views showing the order of steps for explaining a third embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view for explaining a first example of a conventional method for manufacturing a semiconductor device.

FIG. 5 is a schematic cross-sectional view for explaining a second example of the conventional method for manufacturing a semiconductor device.

FIG. 6 is a schematic cross-sectional view for explaining a problem of a conventional semiconductor device.

[Explanation of symbols]

 1 Conductive Adhesive Sheet 2 Dice 3,3a Punch 4 Small Piece 5 Stage 6 Circuit Board 7 Terminals 8,8a Bump 9 Metal Sheet 10 Conductive Adhesive Film 11 Semiconductor Chip 12 Electrode Pad 13 Ball Bump 15 Solder Bump 16 Polyimide Film 17 Cu Ball

 ─────────────────────────────────────────────────── --Continued front page (72) Inventor Teruo Kusaka 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation

Claims (9)

[Claims] 1. A step of selectively cutting a conductive pressure-sensitive adhesive sheet having a conductive resin having B-stage characteristics formed in a sheet shape in a solid state at a low temperature to form a small piece, and the small piece being softened and having an adhesive property. And forming bumps by bonding the small pieces onto the terminals of the circuit board heated to a temperature of, and placing the electrode pads of the semiconductor chip on the bumps by aligning them and heating and curing the bumps. A method of manufacturing a semiconductor device, comprising a step of electrically connecting a terminal of the circuit board and an electrode pad of the semiconductor chip via the bump. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the conductive adhesive sheet has a laminated structure in which a conductive resin film having B-stage characteristics is formed on both surfaces of a metal sheet. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the metal sheet is made of any one of Au, Cu and Al. 4. A conductive resin having B-stage characteristics is A
2. At least one kind of fine particles obtained by plating the surface of metal fine particles or fine plastic particles made of g, Cu, Au or solder with any of the above metals.
A method for manufacturing a semiconductor device according to claim 2. 5. The method for manufacturing a semiconductor device according to claim 1, wherein the conductive adhesive sheet is cut in a solid state by a punching method or a cutting method to form a small piece. 6. A step of selectively cutting a laminated metal sheet having a solder film or a metal film formed on both sides of a metal sheet to form a small piece, and placing the small piece on a terminal of a circuit board for reflow. A step of forming a bump, and an electrode pad of a semiconductor chip is aligned and placed on the bump, the bump is heated and reflowed to be joined, and the terminal of the circuit board and the electrode pad of the semiconductor chip are connected via the bump. And a step of electrically connecting to each other. 7. The method of manufacturing a semiconductor device according to claim 6, wherein the metal sheet is made of any one of Au, Cu, Al and Ni. 8. The solder film or the metal film is a Pb-Sn alloy, A
7. The method of manufacturing a semiconductor device according to claim 6, comprising any one of u-Sn alloy, Ag-Sn alloy, Au, Al and In. 9. The method of manufacturing a semiconductor device according to claim 6, wherein the laminated metal sheet is separated by a punching method or a cutting method to form a small piece.