JPH11274199A - Bump electrode forming method and device method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the pull-out ability of conductive paste, by filling the through hole of a stencil mask which is brought into contact with an electronic part with conductive paste and rotating the electronic part and the stencil mask so that conductive particles in conductive paste move by centrifugal force to the electrode forming face side of the electric part. SOLUTION: Cream solder 3 as conductive paste is filled with a through hole 2a, in a state where a stencil mask 2 is positioned so that the through hole 2a of the stencil mask 2 comes above the conductive pad 1a of a wafer 1, and the mask is brought into contact with the wafer 1. Then, the wafer 1 and the stencil mask 2 are rotated in the direction of an arrow A and centrifugal force by which solder particles 3a being conductive particles in cream solder 3, with which the through hole 2a is filled moves to the conductive pad 1a-side of the wafer 1. Thus, the pull-out ability of conductive paste at the time of detaching the stencil mask 2 from the wafer 1 can be improved.

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.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to form a good bump electrode by exposing a conductive paste when separating a stencil mask from an electronic component. An object of the present invention is to provide a method and an apparatus for forming a bump electrode.

[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 a conductive paste is filled into a through-hole of a stencil mask that has been brought into contact with the electronic component, and then filled in the through-hole. The electronic component and the stencil mask are rotated so that the conductive particles in the conductive paste move to the electrode forming surface side of the electronic component by centrifugal force. In the bump electrode forming method according to the first aspect, the conductive paste is filled in the through-hole of the stencil mask that has been brought into contact with the electronic component, and then the electronic component and the stencil mask are rotated to fill the through-hole. The conductive particles in the conductive paste are moved to the electrode forming surface side of the electronic component by centrifugal force to increase the density of the conductive particles in the conductive paste in a portion in contact with the electrode forming surface. As a result, the adhesion (tacking force) between the electrode forming surface of the electronic component and the conductive paste increases, and the adhesion (shear stress) between the inner wall of the through hole of the stencil mask and the conductive paste decreases. . Therefore, when the stencil mask is separated from the electronic component, a good bump electrode can be formed without a part of the conductive paste in the through-hole being in close contact with the stencil mask and being dragged. Note that the rotation of the electronic component and the stencil mask for applying the centrifugal force may be performed during a plate separating operation for separating the stencil mask from the electronic component, or may be performed before the plate separating operation.

According to a second aspect of the present invention, a bump paste 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 stencil mask filled with a conductive paste in the through hole, holding means for holding an electronic component in contact with the stencil mask, and a conductive material in the conductive paste filled in the through hole. Rotating means for rotating the electronic component and the stencil mask held by the holding means to such an extent that the conductive particles move to the electrode forming surface side of the electronic component by centrifugal force. . In the bump electrode forming apparatus according to the second aspect, after the conductive paste is filled into the through-holes of the stencil mask in contact with the electronic component, the electronic component and the stencil mask held by the holding means are rotated at a predetermined rotation speed. By doing so, the conductive particles in the conductive paste filled in the through holes are moved by centrifugal force to the electrode forming surface side of the electronic component, and the conductive particles in the conductive paste in a portion in contact with the electrode forming surface are removed. Increase the density of the particles. As a result, the adhesion (tacking force) between the electrode forming surface of the electronic component and the conductive paste increases, and the adhesion (shear stress) between the inner wall of the through hole of the stencil mask and the conductive paste decreases. . Therefore, when the stencil mask is separated from the electronic component, a good bump electrode can be formed without a part of the conductive paste in the through-hole being in close contact with the stencil mask and being dragged.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment in which the present invention is applied to a bump electrode forming method for collectively 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. Will be described. FIG. 1 is an explanatory diagram of the bump electrode forming method according to the present embodiment. In this method, the stencil mask 2 is positioned so that the through-hole 2a of the stencil mask 2 is located on the conductive pad 1a of the wafer 1, and the stencil mask 2 is brought into contact with the wafer 1.
The solder paste 3 as a conductive paste is filled in the through holes 2a. Thereafter, by rotating the wafer 1 and the stencil mask 2 in the direction of arrow A in the figure, the through holes 2a
The conductive pads 1a of the wafer 1 correspond to the solder particles 3a, which are conductive particles in the cream solder 3 filled in the solder.
Apply centrifugal force to move to the side. Due to this rotation, the solder particles 3 in the portion in contact with the conductive pad 1a
Increase the density of a. As a result, the adhesion (tacking force) between the conductive pad 1a of the wafer 1 and the cream solder 3 is increased, and the through-hole 2a of the stencil mask 2 is formed.
The adhesion force (shear stress) between the inner wall of the solder and the cream solder 3 is weakened. Therefore, when the stencil mask 2 is separated from the wafer 1, a part of the cream solder 3 in the through-hole 2a does not stick to the stencil mask 2 and is dragged, so that good bump electrodes can be formed at once.

FIG. 2 is a schematic configuration diagram of a bump electrode forming apparatus according to the present embodiment. This bump electrode forming apparatus
A plurality (10 in this embodiment)
(Set) U1 to U10 for forming bump electrodes. Each unit includes a main shaft 10, a pulley 11 attached to an end of the main shaft 10, a set of arm members 12 having one end fixed to the main shaft, and a rotatably mounted other end of the arm member. One set of table holder 1
3, a table 14 and the like fixed to one end of the table holder 13 in the vertical direction.

The pulley 11 of the main shaft 11 is a drive pulley 1 attached to a rotation 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 table 14 and the 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).

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.

Further, it is preferable that the door of the airtight housing 100 has a double door structure in order to maintain the predetermined atmosphere.

In the bump electrode forming apparatus having the above structure, 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 a 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, 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, and the conductive portion of the cream solder in the portion in contact with the electrode forming surface is contacted. Increase the density of the particles. Thereby, the adhesive force (tacking force) between the electrode forming surface of the wafer 1 and the cream solder is increased, and the adhesive force (shear stress) between the inner wall of the through hole 2a of the stencil mask 2 and the cream solder.
Becomes weaker.

Next, as shown in a 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. 2, when the stencil mask 2 is separated from the wafer 1,
Bump electrodes are collectively formed on each of the semiconductor elements.

As described above, according to the present embodiment, when the stencil mask 2 is separated from the wafer 1, a part of the cream solder in the through-hole 2a does not stick to the stencil mask 2 and is dragged. Good bump electrodes can be collectively formed on the electrode formation surface.

In addition, a plurality of wafers are placed in the hermetic housing 10.
0, and rotating the plurality of wafers 1 and the stencil mask 2 or separating the stencil mask 2 over a long period of time while preventing the oxidation and drying of the cream solder, thereby making the electrode forming surface of the wafer 1 Since the plate separating operation can be performed in a state in which the adhesive force (tacking force) with the cream solder is strengthened, 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 each unit so that the airflow generated by the rotation of the unit does not reach the adjacent unit. 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 other conductive paste limited to this cream solder is filled. It is.

In the above embodiment, the case where bump electrodes are collectively formed on the wafer 1 on which a plurality of semiconductor elements 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.

[0024]

According to the first and second aspects of the present invention, when the stencil mask is separated from the electronic component, a part of the conductive paste in the through-hole does not adhere to the stencil mask and is not dragged. There is an effect that a good bump electrode can be formed on the electrode forming surface of the component.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a bump electrode forming method according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a bump electrode forming apparatus according to an embodiment of the present invention.

[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 (2)

[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. After filling the through-hole of the stencil mask contacted with the electronic component with the conductive paste, the conductive particles in the conductive paste filled in the through-hole are on the electrode forming surface side of the electronic component. A method of forming a bump electrode, comprising rotating the electronic component and the stencil mask so as to move by centrifugal force. 2. 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 having a through hole for forming a bump electrode. A stencil mask in which the conductive paste is filled in the through-hole and holding means for holding an electronic component in contact with the stencil mask; and the conductive particles in the conductive paste filled in the through-hole are charged with the electron. To the extent that it moves to the electrode forming side of the part by centrifugal force,
A rotating means for rotating the electronic component and the stencil mask held by the holding means;