JP2001237256A - Work mounting method and work mounting body - Google Patents

Abstract

(57) [Problem] To provide a work mounting method and a work mounting body capable of preventing generation of air bubbles in an underfill resin. SOLUTION: A substrate 1 on which a flip chip 11 is mounted with bumps interposed is housed in a casing 34 of a plasma processing apparatus 30, and a pressure of 200 is applied in the casing 34.
A plasma discharge gas is supplied in the range of [pa] to 800 [pa] to generate plasma discharge. The active material due to the plasma discharge generated under the above pressure conditions efficiently enters the gap between the substrate 1 and the flip chip 11, and the resist of the substrate 1 and the surface of the protective film of the flip chip 11 are satisfactorily formed by the action of the active material. Modifies to improve wettability. Thereby, when filling the gap with the underfill resin, the underfill resin adheres well to the modified surface, and good resin filling can be performed without generating bubbles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work mounting method for mounting a work such as a flip chip on a substrate or the like with a bump interposed therebetween, and a work mounting body.

[0002]

2. Description of the Related Art As a method of mounting a work such as a flip chip on a work such as a substrate, it is known to join electrodes of the work with bumps.

FIG. 6 is a sectional view of a conventional mounted package. In the figure, reference numeral 1 denotes a substrate serving as a first work, on which an electrode 2 is formed. The surface of the substrate 1 other than the electrodes 2 is coated with a resist 3. Reference numeral 11 denotes a flip chip as a second work, on which an electrode 12 is formed on a lower surface, and a protective film 13 is formed on a lower surface other than the electrode 12.

[0004] A bump 14 is provided on the electrode 12 of the flip chip 11. Bump 1 of flip chip 11
Reference numeral 4 is bonded to the electrode 2 by performing a heat treatment in a heating furnace. After mounting the flip chip 11 on the substrate 1,
An underfill resin 4 is filled between the substrate 1 and the flip chip 11. The underfill resin 4 is filled to firmly fix the flip chip 11 on the substrate 1.

Normally, the underfill resin 4 is applied on the substrate 1 with a dispenser or the like. The applied underfill resin 4 enters a narrow space between the substrate 1 and the flip chip 11 by capillary force and is filled. Thereafter, the underfill resin 4 is cured by a heat treatment or the like. FIG.
In the figure, the underfill resin 4 indicated by a dashed line indicates a state immediately after being applied to the substrate 1 by a dispenser, and the underfill resin 4 indicated by a solid line indicates a state after entering the substrate 1 and the flip chip 11. I have.

[0006]

However, the conventional method has a problem that air bubbles 5 are easily generated in the underfill resin 4 which has entered between the substrate 1 and the flip chip 11. Since the bubbles 5 lower the fixing force of the flip chip 11 and oxidize the electrodes 2 and 12, it is desirable that the generation of the bubbles 5 be eliminated. Although the cause of the generation of the bubble 5 is not necessarily clear, it is considered that the cause is caused by the quality of the wettability of the underfill resin 4 to the surface of the work such as the substrate 1 and the flip chip 11. Such bubbles are widely generated not only in the flip chip 11 but also in a mounting structure in which works are mounted with the bumps 14 interposed therebetween.

Accordingly, an object of the present invention is to provide a work mounting method and a work mounting body which can prevent generation of air bubbles in the underfill resin.

[0008]

According to a first aspect of the present invention, there is provided a method for mounting a work, comprising: mounting a second work on a first work via a bump; and mounting a second work on the first work.
Exposing the workpiece in a plasma atmosphere at a pressure of 200 Pa to 800 Pa, then injecting an underfill resin between the first and second works, and Curing the resin.

According to a second aspect of the present invention, there is provided a package for a work, wherein the step of mounting the second work on the first work via bumps and the step of mounting the first work on which the second work is mounted are performed under pressure. A step of exposing to a plasma atmosphere of 200 [Pa] to 800 [Pa], a step of injecting an underfill resin between the first work and the second work, and a step of curing the underfill resin. It was manufactured by the method including.

In the above configuration, before the underfill resin enters between the first work and the second work, the underfill resin is exposed to a plasma atmosphere having a pressure of 200 [Pa] to 800 [Pa]. The active substance such as oxygen radicals generated thereby efficiently enters between the first work and the second work and comes into contact with the surface, thereby modifying the physical or chemical properties of the surface. After that, the underfill resin is filled between the first work and the second work by entering the work.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a plasma processing apparatus according to an embodiment of the present invention, FIGS. 2, 3 and 4 are explanatory views of a mounting method according to an embodiment of the present invention, and FIG. 4 is a graph showing the relationship between the plasma processing pressure and the protective film surface contact angle in the plasma processing of the embodiment.

First, referring to FIG.
The structure of 0 will be described. Reference numeral 31 denotes a base plate in which an electrode part 32 is provided. The electrode section 32 is connected to a high-voltage high-frequency power supply 33. On the base plate 31, a casing 34 is installed so as to be freely opened and closed. The casing 34 is connected to a ground 35. Gas for plasma generation is supplied to the inside of the casing 34 from gas supply means (not shown) through a pipe 36. The gas supply means has a pressure adjusting function so that a gas for generating plasma at a desired pressure can be supplied into the casing. The gas in the casing 34 is sucked in vacuum through the pipe 37. 38 is a vacuum suction pump.

The substrate 1 on which the flip chip 11 is mounted is housed on the electrode part 32. FIG. 2 shows the substrate 1. The description of the same elements as those shown in FIG. 6 will be omitted by retaining the same reference numerals. What is important in the present invention is that the second work (flip chip 11) is mounted on the first work (substrate 1) and housed in the casing 34 to perform plasma processing.

Next, the plasma processing will be described. FIG.
The substrate 1 on which the flip chip 11 is mounted is placed on the electrode part 32 and stored in the casing 34 as shown in FIG. Next, the pump 38 is driven to vacuum-evacuate the inside of the casing 34, and a gas for plasma generation is supplied into the casing 34 through the pipe 36. Here, oxygen gas is used as the plasma generation gas, and the pressure of the supplied plasma generation gas is set in the range of 200 [Pa] to 800 [Pa].

Next, a power supply 33 is inputted to apply a high-frequency voltage to the electrode section 32. Then, most of the gas in the casing 34 is ionized, and part of the gas becomes an active substance having a high activity called a radical. In this plasma atmosphere,
The plasma processing is performed by exposing the substrate 1 on which the flip chip 11 is mounted for about 20 seconds. That is, ions and active substances enter between the substrate 1 and the flip chip 11,
It contacts the surface of the substrate 1 or the flip chip 11 to modify the physical and chemical properties of the resist 3 and the protective film 13 coated on the surface. This reforming effect is larger for radicals having a higher activity than ions. Examples of the gas radicalized by the plasma include oxygen and argon. According to the experimental results, the effect of reforming oxygen was good.

Oxygen is converted into oxygen ions e ⁻ and oxygen radicals O ^{* as} an active substance when converted into plasma. The oxygen ions and oxygen radicals enter the gap between the substrate 1 and the flip chip 11 (this gap is generally several tens of microns and extremely narrow as described above), and the upper surface of the substrate 1 and the flip chip 11 The surface has sufficient contact with the lower surface to effectively modify the physical and chemical properties of the surface.

When the plasma processing is completed as described above, the casing 34 is opened and the substrate 1 is taken out.
Next, as shown in FIG. 3, an underfill resin 4 is applied on the substrate 1 by a dispenser or the like. Then, the underfill resin 4 is connected to the substrate 1 and the flip chip 1 by capillary force.
1, the underfill resin 4 is filled during this time. FIG. 4 shows a state in which entry and filling have been completed. Since the surfaces of the substrate 1 and the flip chip 11 have been modified by the plasma treatment, no bubbles are generated. Next, if the underfill resin 4 is cured by heat treatment or the like, the flip chip 11 is firmly fixed to the substrate 1 and the package 10 (work mounted body) is completed. Since the package 10 has few air bubbles contained in the underfill resin 4, the bonding strength of the flip chip 11 is secured and the package 10 is excellent in reliability.

Here, the correlation between the plasma processing pressure in the plasma processing, that is, the pressure of the plasma generating gas (oxygen gas) supplied into the casing 34, and the reforming effect will be described with reference to FIG. FIG. 5 shows the change in the contact angle of the water droplet on the surface of the polyimide protective film when the pressure of the plasma generating gas, that is, the plasma processing pressure is changed. The smaller the contact angle of the water droplet, the better the surface wettability. It is shown that. That is, when the plasma processing condition that can obtain a smaller water droplet contact angle is applied, the effect of modifying the surfaces of the resist 3 and the protective film 13 by the plasma processing is greater.

As can be seen from FIG. 5, particularly good wettability is obtained when the plasma processing pressure is in the range of 200 [Pa] to 800 [Pa]. The reason why the wettability after the plasma processing depends on the plasma processing pressure can be inferred as follows. That is, when the plasma processing pressure is lower than the above range, the density of oxygen radicals and ions generated by the plasma discharge itself is low, so that the amount of the active substance that enters the gap to be processed is small. The modification effect on the surface of the film 13 is low. At a plasma processing pressure higher than the above range, the density of oxygen radicals and ions generated by the plasma discharge is high, but when these densities are higher than a certain level, particles such as oxygen radicals and ions are caught in the gap to be processed. There is a high probability of losing activity by colliding with each other before reaching.

That is, whether the plasma processing pressure is too low or too high, the probability that the active substance generated by the plasma discharge enters the gap is small. In other words, there is a specific plasma processing pressure range suitable for allowing the active substance to efficiently enter the narrow gap. By performing the plasma processing within this plasma processing pressure range, a good surface modification effect can be obtained.
As shown in (2), the range of 200 [Pa] to 800 [Pa] is a specific plasma processing pressure range for obtaining the above-mentioned good surface modification effect.

[0021]

As described above, according to the present invention, the surface of a work is modified by a plasma treatment performed by supplying a plasma generating gas having a pressure in the range of 200 [Pa] to 800 [Pa]. Thereby, it is possible to eliminate the generation of air bubbles in the underfill resin entering between the works by modifying the work surface with high processing efficiency, and to remove the first work from the second work.
Can be firmly mounted on any work. In addition, since the surface of the first work and the surface of the second work can be simultaneously reformed with the second work mounted on the first work, the reforming work can be performed with extremely high workability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a mounting method according to an embodiment of the present invention;

FIG. 3 is an explanatory diagram of a mounting method according to an embodiment of the present invention;

FIG. 4 is an explanatory diagram of a mounting method according to an embodiment of the present invention;

FIG. 5 is a graph showing the relationship between the plasma processing pressure and the protective film surface contact angle in the plasma processing according to one embodiment of the present invention.

FIG. 6 is a cross-sectional view of a conventional mounted package.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2, 12 Electrode 4 Underfill resin 10 Package (work mounting body) 11 Flip chip 14 Bump 30 Plasma processing device 34 Casing

Claims (2)

[Claims] A step of mounting a second work on the first work via bumps; and a step of mounting the second work on the first work.
Exposing the workpiece in a plasma atmosphere at a pressure of 200 Pa to 800 Pa, then injecting an underfill resin between the first and second works, and And a step of curing the resin. 2. A step of mounting a second work on the first work via bumps, and a step of mounting the second work on the first work.
Exposing the workpiece in a plasma atmosphere at a pressure of 200 Pa to 800 Pa, then injecting an underfill resin between the first and second works, and And a step of curing the resin.