JPH11274207A - Method and device for forming bump electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for forming a bump electrode, which has an excellent parting property of conductive paste and can form excellent bump electrodes all together, by separating a screen mask from a water spending a long time under the state wherein there are no drying and oxidation of cream solder. SOLUTION: This is the bump-electrode forming method, which forms a bump electrode on the electrode forming surface by printing cream solder on the electrode forming surface of a wafer 1 through a screen mask 2, wherein a through hole is formed. The mask 2 filled with inert gas is separated from the wafer 1 in the atmosphere filled with inert gas under the saturated vapor pressure. These are the characteristics. Furthermore, in the above described atmosphere, the cream solder can be filled in the through hole of the mask 2 in contact with the wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-shaped semiconductor element such as an IC or LSI, which is surface-mounted on a substrate, a package such as a BGA or CSP in which the semiconductor element is molded,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a bump electrode on an electronic component such as a connector or a substrate itself, and more particularly, to a bump electrode capable of forming a bump electrode with good adhesion to an electrode forming surface of the electronic component. The present invention relates to a forming method and an apparatus therefor.

[0002]

2. Description of the Related Art Along with recent downsizing and cost reduction of electronic equipment, chip-shaped semiconductor elements such as ICs and LSIs, BGAs and CSPs in which semiconductor elements are molded.
And electronic components such as connectors have been surface-mounted on substrates via bump electrodes. In particular, semiconductor devices such as ICs and LSIs have been tending to be surface-mounted as flip-chips on substrates via bump electrodes without packaging. In order to perform surface mounting of such an electronic component on a substrate, it is conceivable to form a bump electrode on the electronic component side.

As a method of forming a bump electrode on an electronic component surface-mounted on the substrate or on the substrate itself, a conductive paste filling member is inserted into a through hole of a stencil mask (print mask) mounted on the electrode forming surface of the electronic component. There has been proposed a method of forming an electrode by filling a conductive paste using a squeegee and separating the electronic component from the stencil mask.

[0004]

However, in the above-described electrode forming method using a stencil mask, after the conductive paste is filled in the through-holes, when the stencil mask is separated from the electronic component, the conductive material in the through-holes is removed. In some cases, a portion of the conductive paste was dragged in close contact with the stencil mask, and a good bump electrode could not be formed. Such a problem can occur not only when an electrode is formed on an electronic component surface-mounted on a substrate but also when an electrode is formed on the substrate itself.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a stencil mask in which through holes are filled with a conductive paste for a long time without drying or oxidizing the conductive paste. Bump electrode forming method and apparatus capable of forming a good bump electrode by exposing the stencil mask to the electronic component by separating the stencil mask from the electronic component by allowing the stencil mask to be separated from the electronic component It is to provide.

[0006]

In order to achieve the above object, the invention of claim 1 is to provide a stencil mask in which a through hole for forming a bump electrode is formed by applying a conductive paste to an electrode forming surface of an electronic component. A bump electrode forming method of forming a bump electrode on the electrode forming surface by printing, wherein the stencil mask filled with the conductive paste is filled with an inert gas and in an atmosphere of a saturated vapor pressure. It is characterized by being separated from electronic components. In the bump electrode forming method of the present invention, the stencil mask filled with the conductive paste is separated from the electronic component in an atmosphere filled with an inert gas and at a saturated vapor pressure. Even when the stencil mask is separated from the electronic component for a long time so that a part of the paste does not stick to the stencil mask and is not dragged, the conductive paste filled in the through holes does not oxidize or dry. .

According to a second aspect of the present invention, in the method of forming a bump electrode according to the first aspect, the conductive paste is filled into the through-holes of the stencil mask in contact with the electronic component in the atmosphere. Is what you do. This claim 2
In the bump electrode forming method, the conductive paste is filled in the through-hole of the stencil mask that has been brought into contact with the electronic component in the above atmosphere, so that the conductive paste used for filling the through-hole is oxidized and dried. In addition, it can be used for a long time to fill the through hole.

According to a third aspect of the present invention, a bump electrode is formed on the electrode forming surface by printing a conductive paste on the electrode forming surface of the electronic component through a stencil mask having a through hole for forming a bump electrode. A bump electrode forming apparatus, comprising a hermetic housing filled with an inert gas and capable of maintaining an atmosphere of a saturated vapor pressure, and holding means for holding an electronic component in contact with the stencil mask in the hermetic housing. And a separating means provided to separate the stencil mask from the electronic component. In the bump electrode forming apparatus according to the third aspect, the stencil mask filled with the conductive paste from the electronic component held by the holding means is sealed in the airtight housing filled with the inert gas and at the atmosphere of the saturated vapor pressure. Even when the stencil mask is separated from the electronic component for a long time so that a part of the conductive paste in the through-hole is not in close contact with the stencil mask and is not dragged, the through-holes are filled. The conductive paste does not oxidize or dry.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is applied to a method and an apparatus for forming bump electrodes made of a conductive paste on a wafer on which a large number of semiconductor elements (semiconductor chips) as electronic components are formed. An embodiment will be described.

FIG. 1 is a schematic configuration diagram of an apparatus capable of realizing the bump electrode forming method according to the present embodiment.
This bump electrode forming apparatus is provided inside the confidential housing 100,
A plurality (10 sets in this embodiment) of units U1 to U10 for forming bump electrodes are provided. Each unit includes a main shaft 10 and a pulley 1 attached to an end of the main shaft 10.
1. a set of arm members 12 having one end fixed to the main shaft; a set of table holders 13 rotatably attached to the other end of the arm members;
And a table 14 fixed to one end in the vertical direction.

The pulley 11 of the main shaft 11 is a drive pulley 1 attached to a rotary shaft 15a of a drive motor 15.
6 and a belt 17 so that the rotational driving force can be transmitted between both pulleys. Also, the main shaft 10 of each unit
Are connected by a bearing 18.

The above table 14 and table holder 1
Numeral 3 is also used as a holding means for holding the wafer 1 and the stencil mask 2, so that the wafer 1 and the stencil mask 2 can be held by a clamp mechanism (not shown). Above the table 14, there is provided a separating means constituted by a servo motor or a linear motor (not shown) for separating the stencil mask 2 from the wafer 1 on the table 14 for a desired time.

The inside of the hermetic housing 100 is maintained at a substantially constant temperature by a temperature controller (not shown). Further, the inside of the hermetic housing 100 is filled with an inert gas such as a nitrogen gas so that cream solder or the like used for forming bump electrodes is not oxidized. In addition, the airtight housing 10
0, a container 20 accommodating a liquid 19 such as alcohol is installed, and the vapor evaporated from the container 20 causes the inside of the hermetic housing 100 to have an atmosphere of a substantially saturated vapor pressure,
Thereby, drying of the cream solder can be prevented for a long time (for example, 1 hour or more). The liquid in the container 20 may be spontaneously evaporated, or may be heated and forcibly evaporated. Alternatively, a predetermined atmosphere may be obtained by discharging the liquid into the airtight housing 100 in the form of a mist from the spray nozzle. This airtight housing 100
In order to more accurately adjust the atmosphere inside the device, a vapor pressure sensor may be provided, and the heating and spraying of the liquid may be controlled based on the output of the sensor.

It is preferable that the door of the hermetic housing 100 has a double door structure in order to maintain the predetermined atmosphere.

In the bump electrode forming apparatus having the above configuration, FIG.
As shown in the unit U1, the wafer 1 is first set on the table 14, the stencil mask 2 is brought into contact with the electrode forming surface of the wafer 1, and cream solder is applied from above the stencil mask 2 using a squeegee 4. , The stencil mask 2
Is filled with cream solder.

Next, as shown in the unit U2 in FIG.
After filling the cream solder, the table holder 1
3 is rotated by 180 degrees around the axis 13a so that the stencil mask 2 is positioned on the main shaft 10 side. Then, the drive motor is turned on to rotate the main shaft 10, and the wafer 1 and the stencil mask 2 are moved to the arm member 12 and the table holder 13
And with the table 14. By this rotation, as shown in FIG. 2, the solder particles in the cream solder filled in the through holes 2a of the stencil mask 2 are moved to the electrode forming surface side of the wafer 1 by centrifugal force. Increase the density of conductive particles in cream solder.
As a result, the adhesive force (tacking force) between the electrode forming surface of the wafer 1 and the cream solder increases, and the adhesive force (shear stress) between the inner wall of the through hole 2a of the stencil mask 2 and the cream solder decreases.

Next, as shown in the unit U3 in FIG.
The table holder 13 is again rotated by 180 degrees around the axis 13a to return the wafer 1 and the stencil mask 2 to their original positions. Then, the wafer 1 and the stencil mask 2 are left in the hermetic housing 100 as necessary, and the adhesion (tacking force) between the electrode forming surface of the wafer 1 and the cream solder.
Strengthen.

Next, as shown in a unit U10 in FIG. 1, the stencil mask 2 is slowly separated from the wafer 1 by a separating means (not shown) over a long period of time, so that bump electrodes are collectively formed on each semiconductor element of the wafer 2. It is formed.

As described above, according to this embodiment, the through-hole 2 is formed without drying or oxidizing the cream solder.
Since the stencil mask 2 filled with the cream solder can be separated from the wafer 1 for a long time, the through-hole 2a
A portion of the cream solder in the stencil mask 2 is not in contact with the stencil mask 2 and is not dragged. Electrodes can be formed.

Further, a plurality of wafers can be stored in the hermetic housing 10.
0, and rotating the plurality of wafers 1 and the stencil mask 2 or separating the stencil mask over a long period of time while preventing the cream solder from oxidizing and drying. Since the plate separating operation can be performed in a state in which the adhesive force (tacking force) with the solder is increased, the productivity of the wafer 1 on which good bump electrodes are formed can be increased.

In the above embodiment, a partition wall may be provided between the units so that the air flow generated by the rotation of the units does not reach the adjacent units. Also,
In the above embodiment, the case where ten sets of units are provided has been described, but the present invention can be applied without being limited to the number of units.

In the above embodiment, the case where cream solder is filled as the conductive paste has been described. However, the present invention can be applied to the case where another conductive paste limited to this cream solder is filled. It is.

Further, in the above embodiment, the case where bump electrodes are collectively formed on the wafer 1 on which a plurality of semiconductor elements to be surface-mounted on a substrate are formed has been described. BGA,
The present invention can also be applied to a case where bump electrodes are formed on a CSP type package or connectors mounted on a surface of a substrate, and the same effect can be obtained.

When bump electrodes are formed on an electronic component such as a package or a connector, a plurality of electronic components are arranged so that the bump electrode formation surface is located on the same virtual plane.
The bump electrodes may be collectively formed on the bump electrode formation surfaces of the plurality of electronic components.

[0025]

According to the present invention, the stencil mask filled with the conductive paste in the through holes is separated from the electronic component for a long time without drying or oxidizing the conductive paste. Because it is possible to exfoliate the conductive paste when separating the stencil mask from the electronic component,
There is an effect that a good bump electrode can be formed.

In particular, according to the invention of claim 2, there is an effect that the conductive paste used for filling the through holes of the stencil mask can be used for a long time to fill the through holes without oxidizing and drying. is there.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a bump electrode forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a centrifugal force acting when the wafer and the stencil mask rotate in the same apparatus.

[Explanation of symbols]

 Reference Signs List 1 wafer 1a conductive pad 2 stencil mask 2a through hole 3 cream solder 3a solder particle 4 squeegee 10 main shaft 11 pulley 12 arm member 13 table holder 14 table 15 drive motor 16 drive pulley 17 belt 18 bearing 19 bearing liquid for maintaining saturated vapor pressure Reference Signs 20 container 100 hermetic housing U1 to U10 unit for forming bump electrode

Claims (3)

[Claims] A method of forming a bump electrode on a surface of an electronic component by printing a conductive paste through a stencil mask in which a through hole for forming a bump electrode is formed. A method of forming a bump electrode, wherein a stencil mask filled with the conductive paste is separated from the electronic component in an atmosphere filled with an inert gas and at a saturated vapor pressure. 2. The bump electrode forming method according to claim 1, wherein the conductive paste is filled in a through hole of the stencil mask in contact with the electronic component in the atmosphere. . 3. A bump electrode forming apparatus for forming a bump electrode on an electrode forming surface by printing a conductive paste on an electrode forming surface of an electronic component through a stencil mask in which a through hole for forming a bump electrode is formed. An airtight housing filled with an inert gas and capable of maintaining an atmosphere of saturated vapor pressure, holding means for holding electronic components in contact with the stencil mask in the airtight housing; An apparatus for forming a bump electrode, comprising a separating means provided to separate from the electronic component.