JPS5925378B2 - How to mount electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electronic components, and particularly to a method for high-density packaging of semiconductor devices.

Conventionally, semiconductor devices have been assembled by using wire bonding to connect electrodes on a semiconductor element (hereinafter referred to as pads) and external electrodes, or by connecting directly to external leads without using wire bonding.

The method using wire bonding does not allow for high-density assembly because bonding equipment is used (one wire at a time).

On the other hand, as a method that does not use wire bonding, the flip-chip method is the closest to the present invention.

In this method, a metal bump is formed directly on the surface of the electrode on the semiconductor element side, and the metal bump is connected to an external electrode via the bump. That is, as shown in FIG. 1, in the flip-chip method, metal bumps 2 are formed in advance on the pad surface of a semiconductor element 1, and a heat-resistant insulating film (on which external electrodes 3 are formed) facing the metal bumps 2 is formed. 4 (hereinafter referred to as a film carrier) are superimposed and the metal bumps 2
In this method, the external electrode 3 is connected to the external electrode 3 by pressure bonding.

Note that 5 is used as an external lead (conductor wiring on the film carrier 4, and 6 is an insulating film. However, the drawback of the conventional flip-chip method is that various metals are vapor-deposited and plated directly on the semiconductor element. Since the bumps are formed through processes such as etching, the manufacturing process for semiconductor devices becomes complicated, and almost completed semiconductor devices are often damaged.

Further, since bumps are usually formed on semiconductor devices by batch processing, if a failure occurs in the bump formation process, almost all of the completed semiconductor devices will be defective. Also, conventionally 1
It was necessary to provide a certain amount of space between each semiconductor chip, making it impossible to perform high-density packaging. Furthermore, a method shown in FIG. 2 is known as a method for solving the above-mentioned drawbacks.

That is, the conductor wiring 12 is placed on the glass substrate 11 in advance.
A low melting point glass layer 15 is further formed on the conductor wiring at a portion corresponding to the electrode pad 14 on the semiconductor element 13.

(FIG. 2a) Next, the pad 14 of the semiconductor element 13 and the conductor wiring are aligned and brought into close contact with each other via this low melting point metal layer 15 (FIG. 2b).

Thereafter, from the glass substrate 11 side, a light beam A focused by a lens or the like is sequentially irradiated to raise the temperature of the portion of the conductor wiring 12 facing the pad 14, thereby locally heating the low melting point metal layer 15 by 15°. The conductor wiring 22 and the pad 25 are then melted as shown in FIG. 2c.

However, with this method, when heating by laser irradiation, it is necessary to fix the position so that it does not misalign.On the other hand, in order to improve the wettability of the low melting point metal and the conductor wiring The pad surface must be covered with oxidation-resistant metal such as gold plating.Furthermore,
In order to prevent the low melting point metal from oxidizing during laser irradiation, it was necessary to use an inert gas atmosphere or to perform the process in vacuum. In view of the above-mentioned drawbacks, an object of the present invention is to easily perform wireless bonding without performing any special processing on electronic components such as semiconductor elements and electrodes of external conductor wiring, and to enable high-density mounting. An object of the present invention is to provide a method for mounting electronic components characterized by the following.

Next, one embodiment of the present invention will be described with reference to FIG.

In FIGS. 3 to 5, the same parts as in FIG. 2 are denoted by the same numbers. In FIGS. A conductive thin film is formed on a transparent substrate such as Pyrex glass (trademark of Corning Co., Ltd.) or sapphire (for example, copper of 1 to 2 μm
The conductor wiring 12 is formed using photolithography, which is a common IC manufacturing technique (FIG. 3a).

Next, a paste (connection layer) 25 (for example, solder paste with a thickness of about 50 to 100 μm) made of a mixture of an adhesive organic substance and a fine metal powder is applied to the entire surface, and the connection layer is Pad 1 of semiconductor element 13 via layer 25
4 and the conductive wiring 12 are aligned and pasted using the adhesiveness of the connection layer (FIG. 3b).

After that, from the glass substrate 12 side, light rays A (for example, if the substrate is glass, YA
If the substrate is made of Si, a G laser is used to irradiate a CO2 laser (focused slightly larger than the pad area) to raise the temperature of the portion of the conductor wiring 12 facing the pad 14, and locally melt the connection layer 25. Further, metal powder 25I is melted and precipitated to connect the conductor wiring 12 and the corresponding pad 14.

At this time, the gap between the conductor wiring and the pad is filled (
Figure 3c). At this time, the metal included in the connection must have a melting point lower than that of the metal of the conductor wiring 12 and pad 14. For example, if the conductor wiring and pad surfaces are made of copper and a paste containing solder powder mixed in flux is used as the connection layer, the conductor wiring and pad surfaces can be connected by heating locally to 200 to 300°C using a laser beam. By depositing solder between the pads, we were able to obtain continuity. In addition, since the above method locally heats only the pad, there is no misalignment of the chip during bonding. In other words, the adhesiveness of the flux was sufficient for temporarily fixing the chip. Finally, the unmelted portion 2 of the connection layer 25
51 is removed by washing with an organic solvent or the like, and the connection between the semiconductor element and the conductor wiring is completed (FIG. 3d).

At this time, in order to easily clean and remove the connection layer, it is sufficient to provide a through hole 26 or groove 27 (as shown in FIG. 4) in a portion of the transparent substrate where there is no conductor wiring. In addition, when a solder paste is used as the connection layer 25 in the embodiment of the present invention, it can temporarily fix the semiconductor element, prevent oxidation of the electrode pad part or conductor wiring part during laser heating, and improve the wettability of eluted metal. It is convenient to wear them at the same time.

In addition, metals with very high reflectivity such as A
When using t etc., between the substrate glass and the conductor wiring,
By providing a light absorption layer, the energy of light can be used effectively.

By using the above method, wireless bonding can be performed without special processing on the semiconductor element side or the substrate side on which conductor wiring is formed, resulting in a very high yield and a very low manufacturing cost for semiconductors. Devices can be assembled.

In addition, since local heating is performed only on the opposing surfaces to connect the semiconductor element and the conductor wiring, the position of the chip will not shift during heating even if it is temporarily fixed due to the viscosity of the connection layer, making it possible to mount multiple semiconductor elements at the same time. In this case, there is ultimately no need to worry about creating gaps between semiconductor elements, and furthermore, multilayer conductor wiring can be formed on the glass substrate, so the fifth
As shown in the figure, it is possible to implement extremely high-density packaging of a large number of semiconductor elements at intervals of, for example, several tens of microns, and it is also possible to form multilayer conductor wiring on a transparent substrate to achieve even higher density. can do. Furthermore, although this embodiment shows an example in which the connection layer 25 is formed on the conductor wiring 12, it is clear that the same effect can be obtained even when the connection layer 25 is formed only on the pad 14.

Although the present invention is a very useful method for assembling semiconductor devices, particularly for high-density packaging, it can also be applied to electronic components other than semiconductor devices.

Therefore, the present invention greatly contributes to easy and high-density mounting of electronic components.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional film carrier and a semiconductor element on which metal bumps are formed, FIGS. 2 a-c are process cross-sectional views of the bumpless wireless bonding method of the present invention, and
Figures a to d are cross-sectional views showing the steps of a wireless bonding method according to another embodiment of the present invention, and Fig. 4 is a cross-sectional view showing the assembly of a semiconductor device using another transparent substrate according to the method of the present invention. 11... Glass substrate, 12... Conductor wiring, 13...
- Semiconductor substrate, 14... Pad, 15... Low melting point metal layer, 25... Solder paste.

Claims (1)

[Claims] 1. Conductor wiring formed on a transparent substrate and connection pads formed on an electronic component are temporarily aligned through a paste-like connection layer made of a mixture of an organic substance and fine metal powder. Glue and
Furthermore, the connection layer is irradiated with concentrated light to locally raise the temperature, locally melting the metal fine powder in the connection layer, and then washing and removing the unmelted portion of the connection layer. A method for mounting electronic components, characterized by electrically connecting conductor wiring and pads. 2. The electronic component mounting method according to claim 1, wherein the metal fine powder in the connection layer is made of a low melting point alloy such as solder. 3. The electronic component mounting method according to claim 1, wherein the connection layer is applied only to a corresponding portion of at least one of the conductor wiring or the connection pad.