JPH0734448B2 - Semiconductor device mounting method - Google Patents

Description

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

2. Description of the Related Art Conventionally, a method of mounting a semiconductor device on a circuit board is a method of inserting a semiconductor device in a dual in-line package molded with plastic into a circuit board and soldering it, or forming a semiconductor device in advance. There is a TAB method, etc., in which semiconductor devices are collectively bonded to a flexible circuit board using the gold bumps that have been placed. In order to mount at higher density, solder bumps 106 are previously formed on the aluminum electrodes 102 of the semiconductor device 101 having the protective film 103 as shown in FIG. 4, and the semiconductor device 101 is shown in FIG. As described above, the copper bumps 112 are placed face down so that the solder bumps 106 are aligned with the copper electrodes 112 formed on the substrate 111 having the resist film 113, and the solder bumps are heated and pressured above the melting point of the solder.
There is also a flip chip bonding method in which 106 is melted and soldered to the copper wiring film 112.

Problems to be Solved by the Invention However, in the conventional flip-chip bonding method, when solder bumps are formed, two layers of chromium and copper are subjected to an underlying treatment by vacuum deposition and photolinography, and then electrolytic plating and vacuum deposition are performed. Since the solder bumps are formed by the above method and the heat treatment, there are problems that the bump forming process is complicated and the cost is high, and it is necessary to apply flux to the substrate during soldering.

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the present invention provides a step of forming a solderable metal film on an electrode of a semiconductor device and a method of soldering on an electrode of a circuit board. And a step of forming a metal film, and solder fine particles are dispersed between the circuit board and the semiconductor device when the electrodes of the semiconductor device are arranged face down with respect to the electrodes of the circuit board. The step of sandwiching the thermoplastic resin film, and the circuit board and the semiconductor device are thermocompression-bonded to each other at a temperature which is 3 to 20 degrees lower than the melting point of the solder fine particles, and the electrodes of the circuit board and the semiconductor device. The method of mounting a semiconductor device includes a step of metal-bonding with an electrode.

Action Next, the action of the components of the present invention will be described.

The electrode of the semiconductor device is usually an aluminum thin film, but in the present invention, a solderable metal film is formed on the aluminum electrode of the semiconductor device to facilitate metal bonding with the solder fine particles. Examples of solderable metal films include:
There are copper, nickel, gold, tin, etc. In order to improve the adhesion of the solderable metal film to aluminum, chromium, titanium or the like may be attached to the base. Further, the electrodes of the circuit board are formed with solderable metal films for the same reason, but they are not necessarily the same metal film as the electrodes of the semiconductor device.

The solder fine particles bond the electrodes of the semiconductor device and the electrodes of the circuit board to enable a strong bonding force and reliable electrical connection. The thermoplastic resin film is a medium for uniformly dispersing the solder fine particles and facilitating the handling of the solder fine particles. If it can be temporarily fixed to the semiconductor device or the circuit board with weak heating and pressure and is not corrosive, Well, it does not require a particularly strong adhesive force, but thermocompression bonding is not conveniently performed unless it softens even at a temperature 20 degrees lower than the melting point of the solder fine particles.

In the present invention, thermocompression bonding has an action of bringing the metal film provided on the electrode of the semiconductor device into pressure contact with the solder fine particles and an action of bringing the metal film provided on the circuit board into contact with the solder fine particles. At that time, the temperature of the solder fine particles is only 3 to 20 degrees lower than the melting point, so that the solder fine particles are not melted, but since pressure is applied, the solder fine particles are strongly pressed against the metal film and are deformed while being deformed. It is considered that metal diffusion can be ensured without the need for flux application because partial diffusion occurs in the. If the temperature at the time of pressure bonding exceeds the temperature which is lower than the melting point of the solder fine particles by 3 degrees, the contact pressure between the metal film and the solder fine particles is insufficient and the bonding cannot be performed without the flux.

If the temperature is lower than the melting point of the solder fine particles by 20 ° C., partial diffusion of the solder fine particles and the metal film does not occur.

Embodiment Next, an embodiment of the present invention will be described with reference to FIGS.

First, the aluminum electrode 2 of the semiconductor device 1 on which the protective film 3 is formed
Of 500 Å of chromium formed by sputtering, and 15 μ of film formed by sputtering and electroplating
The copper layer 8 which is a metal film which can be soldered to the chromium layer 7 by etching copper of m using the photolithography technique
Is formed.

On the other hand, on the glass substrate 11 which is a circuit board, chromium with a film thickness of 500Å formed by the sputtering method and copper with a film thickness of 2000Å formed by the sputtering method can be soldered to the chromium layer 14 by etching using the photolithography technique. A copper wiring film 12 which is a metal film is formed in advance.

Next, the semiconductor device 1 and the glass substrate 11 are aligned with each other, and the melting point by the differential scanning calorimetry is 170 ° C. between them.
Film-shaped thermoplastic resin 4 containing the solder fine particles 5
Is narrowed, and thermocompression bonding is performed from the back surface of the semiconductor device 1. For the temperature and time of the pressing tool at that time, insert a fine thermocouple into the joining surface in advance and measure the temperature rise of the joining surface with respect to the pressing time for each temperature of the pressing tool. Ask for.
That is, the tool temperature and the pressurizing time were determined so that the temperature of the joint surface was 3 to 20 degrees Celsius lower than the melting point of the solder fine particles. As an example, good results were obtained by pressing at a tool temperature of 270 ° C for 15 seconds. The temperature of the joint surface at this time was 160 ° C.

FIG. 6 shows the relationship between the joining surface temperature and the joining strength when the pressing time is 10 seconds. Bonding strength is chip size 4mm
Solder fine particles showing the shearing force required to peel off a semiconductor device of × 4 mm, pad size 100 μm, pad number 12 places / chip as the load per pad, have a melting point (peak) by differential scanning calorimetry of 170 ° C. Then, particles having a particle diameter of 2 to 7 μm were used, and as a result, a bonding strength of 60 g / pad or more was obtained at 150 ° C. to 167 ° C., and practical strength was reached.
Particularly desirable is 160 ° C to 167 ° C. Junction surface temperature is 15
If the temperature is lower than 0 ° C, the solder fine particles are less likely to be crushed, so that the bonding strength becomes insufficient. Further, when the bonding surface temperature is 163 ° C. or higher, the solder fine particles are easily crushed by a slight pressure, and particularly when the temperature is higher than the melting point, the solder fine particles become liquid and no pressing force is applied. The surface oxide film of the film 12 is broken, and the solder fine particles are less likely to be partially diffused in these copper coatings, so that the bonding strength is reduced.

EFFECTS OF THE INVENTION As described above, according to the present invention, solderable metal films are formed on both electrodes of a semiconductor device and electrodes of a circuit board, and solder fine particles are prepared by dispersing these in a thermoplastic resin film. Since they are pressure-bonded without melting, both electrodes can be bonded through the solder fine particles without using flux, which has great industrial utility value.

[Brief description of drawings]

FIG. 1 is a sectional view showing a mounted state of a semiconductor device in an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the same joint portion, and FIG. 3 is a thermoplastic resin in which solder fine particles are dispersed in an embodiment of the present invention. FIG. 4 is a perspective view of the film, FIG. 4 is a cross-sectional view of a semiconductor device of a conventional example, FIG. 5 is a cross-sectional view showing a mounted state of the semiconductor device, and FIG. 6 is a graph showing a bonding surface temperature and a bonding strength in an embodiment of the present invention. It is a relationship diagram which shows a relationship. 1,101 ... Semiconductor device, 5 ... solder fine particles, 8 ... copper layer, 11 ... glass substrate, 12,112 ... copper wiring film.

Claims (1)

[Claims] 1. A step of forming a solderable metal film on an electrode of a semiconductor device, a step of forming a solderable metal film on an electrode of a circuit board, and the semiconductor device on the electrode of the circuit board. A step of sandwiching a thermoplastic resin film in which solder fine particles are dispersed between the circuit board and the semiconductor device when the electrodes are arranged so as to face each other face down, the circuit board and the semiconductor device, A method for mounting a semiconductor device, comprising the steps of thermocompression bonding so that the temperature is lower than the melting point of the solder fine particles by 3 to 20 degrees, and the electrodes of the circuit board and the electrodes of the semiconductor device are metal-bonded.