JPS5847853B2 - density - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing corrosion of electronic components using aluminum conductors, in which a chemical-resistant protective film, such as a photoresist, is used as a mask to partially form a corrosion-resistant film to protect the aluminum conductor of electronic components. This invention relates to a method of imparting corrosion protection to.

FIG. 1 shows an example of a resin molded integrated circuit.

FIG. 1a shows a state in which the IC chip is wire-bonded to external lead wires.

In FIG. 1, 1 is a substrate, 2 is a chip such as a semiconductor element or a mixed integrated circuit element, 3 is an aluminum conductor, 4 is a lead wire, and 5 is a lead conductor.

A longitudinal cross-sectional view of the same is shown in FIG. 2, and a resin-molded state is shown in FIG. 3.

7 is a resin mold. The use of aluminum conductors in integrated circuits is widespread.

Since this aluminum conductor cannot be used in an exposed state, the lead conductor and aluminum conductor are connected by bonding with a lead wire and then resin molded.

However, depending on the device, cracks may occur between the lead conductor and the resin, and moisture will be transmitted in the order of IJ lead conductor -> lead wire -> aluminum conductor, corroding the aluminum conductor.

To prevent this, it is necessary to form an anticorrosion coating on the surface of the aluminum conductor.

As an example, if only a resin mold is combined for 200 hours or more at a relative humidity of 90°C and 80°C, the yield will be considerably reduced although the desired properties will be exhibited.

The purpose of the present invention is to provide a method for improving the corrosion resistance of aluminum conductors of electronic components that have been incompletely packaged with resin or the like, and of electronic components that omit packaging and are used with the aluminum conductors exposed. There is something to do.

The present invention is characterized in that, in a method for forming a moisture-resistant protective film on the surface of an aluminum conductor other than the bonding part of an electronic component, after forming a chemical-resistant film on the bonding part of the aluminum conductor, chromic acid, A method for forming an anti-corrosion coating on an electronic component conductor, which is characterized in that it is treated with a mixed aqueous solution containing phosphoric acid and a fluorine compound (hereinafter referred to as the treatment liquid of the present invention).

Electronic components to which the present invention can be applied include resistors, capacitors, other passive elements, active elements such as thin film integrated circuits, monolithic integrated circuits, and hybrid integrated circuits, etc., with electrodes made of aluminum, or lead conductors drawn out from the electrodes. is connected to an aluminum conductor, or the lead conductor leading to the outside is made of aluminum.

At least up to the aluminum conductor connected to the lead wire of the above element is treated with a mixed aqueous solution containing chromic acid, phosphoric acid, and a fluorine compound to form a coating (hereinafter, this coating will be referred to as the coating of the present invention).

Preferably, the coating of the present invention is formed on all of the aluminum except the bonding portion.

At this time, since the coating of the present invention is applied to the entire surface of the aluminum, it is necessary to expose the bonding portion.

In the present invention, a coating resistant to the treatment solution of the present invention is used as a means for exposing a portion of the aluminum.

One example is a photoresist film.

Alternatively, a chemical-resistant metal film may be formed by mask vapor deposition.
In that case, the metal only needs to be resistant to the treatment solution of the present invention.

Such metals include, for example, NiCrAu, Cr-C
Alloy film or laminated film such as u, Fe, Cr, Ti, Ta
etc. membrane.

In the case of this metal, since the film of the present invention is not formed on the surface thereof, bonding can be performed by further mask-depositing a metal film having good wettability with solder on the surface.

The treatment solution of the present invention is preferably used to form a smooth and dense film.

When used in electronic components, it is preferable to use a non-alkaline liquid mixture in order to reduce the surface charge density and prevent the formation of channels.

According to the present invention, since the coating of the present invention is formed on aluminum, the corrosion resistance of the aluminum conductor can be improved.

Furthermore, since the bonding portion can be removed, there is no problem in connecting lead wires or conducting wires.

Examples are shown below.

Example 1 Prior to carrying out the process for selectively forming the corrosion-resistant film of the present invention using a photoresist pattern, the composition of the treatment solution of the present invention was first investigated.

FIG. 4 shows the results when F/Cro3=0.10 and the amount of phosphoric acid was varied.

The processing temperature is 27°C. Here, the mark ◯ indicates that a film exhibiting an interference color was formed, and the mark x indicates that green powdery crystals were removed.

These results show that the amount of phosphoric acid is not significantly affected by the formation of the film of the present invention, and that the amount of chromic acid is preferably 3 to 8 g.The minimum amount of phosphoric acid is 109/l, and the maximum amount of phosphoric acid is 30 g. It was found to be 0 g/13.

Therefore, the amount of phosphoric acid was set to 10 to 300 g/l, the amount of chromic acid was set to 6 g, and the solution was treated for 1 to 5 minutes at 20 to 50 °C with the F/Cro3 value varied from 0.03 to 0.60. The formation state of the film of the present invention was investigated.

The obtained results are shown in FIG. 5, where the ◯ mark indicates the liquid composition that produced a glossy film, and the x mark indicates that a green powder was produced.

Next, these samples were heated at 80°C and 90°C.
When the state of the sample was examined after being left for 1,000 hours under (relative humidity) conditions, it was confirmed that the sample in the shaded area in FIG. 5 did not corrode under these conditions.

Therefore, it has become clear that liquid compositions within the shaded range can be used for treatment with the treatment liquid of the present invention.

Therefore, as shown in FIG. 6, is it possible to form a photoresist pattern in advance on the part to be bonded and then locally treat only the other parts with the treatment solution of the present invention? I considered whether.

In FIG. 6, 11 is a substrate, 12 is an aluminum conductor, and 13 is a photoresist.

As a result, if a photoresist pattern heat-treated in the range of 50 to 200°C is used as a mask, the processing solution of the present invention will not penetrate under it, and the processing solution of the present invention will selectively cover only the other parts. It has become clear that it can be processed by

Therefore, when we ultrasonically bonded 50 μΦ thin wires of copper, gold, and aluminum to such untreated conductor connection parts that had been partially treated with the treatment solution of the present invention,
We confirmed that these thin wires could be connected without any problems.

It has also been found that instead of ultrasonic bonding, a method of forming an aluminum vapor deposition pattern on the bonding butt portion (connection portion) can also be used.

Next, when the resistance values of the connected portions of these samples were measured, it was confirmed that all the samples had a resistance of 50 mβ or less, and could be used without any abnormality in terms of resistance values.

In the above-mentioned embodiment, it is necessary to form a protective coating on only the aluminum of the bonding butt portion by the method used so far to prevent corrosion.

However, as shown in FIG. 7a, a photoresist 23 is formed on the surface of the aluminum conductor 22 formed on the substrate 21, and as shown in FIG. After forming, remove the photoresist 23 as shown in C, apply a corrosion-resistant coating 25 of gold, platinum, etc. as shown in d, and then form the wire lead 26 as shown in e. This is effective in preventing corrosion of Al in the bonding pad portion due to transmitted moisture.

Note that if Au is directly connected to AA, Au and Al will alloy and deteriorate, so in such a case, Al-C
It is effective to use a general method of interposing a film that prevents alloying, such as r-Au or Al-NiCr-Au.

Although not shown in the figure, after being treated with the treatment liquid of the present invention, CVD
An insulating protective film such as Sio2 is formed on the entire surface using a sputtering method, and then the insulating film only on the bonding pad is removed by etching, and the aluminum is covered with a corrosion-resistant metal as mentioned above to improve the reliability of the device. Methods to improve this are also effective.

Incidentally, although the film of the present invention has poor wettability with respect to solder, this can be reversely used as a solder resist.

Conventionally, silicon dioxide films have been used as solder resists, but when formed by sputtering etc., the temperature of the substrate to be processed rises to about 300°C, is exposed for a long time, and is subject to treatments such as etching. This can cause the conductor to peel off or increase the resistance of the conductor.

On the other hand, the film of the present invention can be formed at room temperature, and if it is partially covered with photoresist and treated with the treatment solution of the present invention, the photoresist film can be removed at a low temperature. The conductor does not deteriorate, and when the metal is used as a resist for chromate treatment, the metal becomes a bonding pad.

As described above, when attempting to partially solder an aluminum conductor, the solder resist film can be removed without deteriorating the element or conductor.

Moreover, when a silicon dioxide film is used as a solder resist, it can only be formed on a flat surface, but when it is treated with the treatment solution of the present invention, it can be formed on the entire surface because it is a dipping process, so it is suitable as a solder resist for parts such as terminals. .

[Brief explanation of the drawing]

Figure 1 is a plan view and cross-sectional view showing the connection part of the IC, Figure 2 is a
The figure is a longitudinal sectional view of Fig. 1, Fig. 3 is a longitudinal sectional view of the resin molded state of Fig. 2, Fig. 4 is a diagram showing the mixing ratio of the treatment liquid composition of the present invention, and Fig. 5 is a longitudinal sectional view of Fig. 6 is a plan view showing a method of carrying out the present invention, and FIG. 7 is a sectional view showing a modification and application example of the present invention. Explanation of symbols, 21... Board, 22...
Aluminum conductor, 23...photoresist,
24... Coating formed by treatment with a mixed aqueous solution containing chromic acid, phosphoric acid, and fluorine compound, 25...
...Corrosion-resistant metal coating, 27...Lead wire.

Claims (1)

[Claims] 1. In a method of forming a corrosion-resistant protective film on the surface of an aluminum conductor of an electronic component except for a bonding part, after forming a chemical-resistant film on the bonding part, chromic acid, phosphoric acid, fluorine-containing compound, etc. 1. A method for preventing corrosion of electronic component conductors, characterized by treating with a mixed aqueous solution containing a substance. 2. A method for preventing corrosion of an electronic component conductor according to claim 1, wherein the chemical-resistant coating is a metal that is not treated with the mixed aqueous solution containing the chromic acid, phosphoric acid, and fluorine compound.