JP3395609B2 - Solder bump formation method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder bump forming method for forming a solder bump on an electrode of an electronic component or a substrate.

[0002]

2. Description of the Related Art As a mounting method for electronic parts, a method using solder bumps is known. In this method, solder bumps, which are protruding electrodes of solder, are previously formed on the electrodes of the electronic component or the substrate, and the solder bumps are soldered to the electrodes of the electronic component or the substrate. As a method of forming this solder bump, a method using a solder ball has been conventionally used. In this method, a solder ball is transferred onto an electrode of an electronic component or substrate on which a solder bump is to be formed, and the transferred solder ball is heated and melted by reflow to form a spherical solder bump on the electrode. It is a thing.

In this method, however, it is necessary to apply flux to either the solder ball or the electrode when the solder ball is transferred onto the electrode. This flux has a role of adhering the solder ball onto the electrode due to the viscosity of the flux during transfer, and a role of removing the oxide film on the soldering surface to improve the solderability.

[0004]

However, the flux generally has the property of corroding the electrodes of the substrate with the passage of time, and in the case of using the flux, in order to ensure reliability after soldering, after the reflow, Need cleaning. However, the cleaning process used for flux cleaning is complicated by the restriction of the use of conventional solvents such as CFCs, which requires more work and cost, and does not require cleaning after reflow. A method of forming solder bumps has been desired.

Further, as a problem caused by using the solder balls as a solder supplying means, there is a cost for forming solder bumps. There has been a problem that the cost of the solder balls increases significantly as the diameter of the solder balls decreases due to the downsizing of electronic components, and as a result, the cost required to form the solder bumps increases.

[0006] Therefore, an object of the present invention is to provide a solder bump forming method which can reduce the cost without requiring cleaning after reflow or using solder balls.

[0007]

According to a method of forming a solder bump of the present invention, a solder portion is formed on a base material without using a solder ball corresponding to an electrode position of an electronic component or a substrate on which the solder bump is formed. And a step of removing an oxide film on the surface of the solder portion by plasma etching, a step of aligning the solder portion of the base material with an electrode of an electronic component or a substrate, and the base material being an electronic component or a substrate. And pressing to heat to transfer the solder portion to the surface of the electrode to form a solder bump.

According to the present invention, the surface of the solder portion formed on the base material corresponding to the electrode position of the electronic component or the substrate is plasma-etched, and the solder portion is heated on the electrode of the electronic component or the substrate. By pressing and transferring, the solder bumps can be formed without using the solder balls and without the need to apply the flux.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. 1 (a), (b), (c),
(D), FIG. 2 (a), (b), (c), FIG. 3 (a),
(B), (c) is process explanatory drawing of the forming method of the solder bump of one embodiment of this invention. Each figure shows the solder bump forming method in the order of steps.

First, in FIG. 1A, a solder portion 2 is formed on a tape-shaped substrate 1. As the base material 1, a resin tape such as polyimide is used. As shown in FIG. 1B, the solder portion 2 is formed corresponding to the positions of the electrodes of the substrate and the electronic component on which the solder bumps are formed. Plating, vapor deposition, dispensing of molten solder, etc. can be used.

Next, the base material 1 on which the solder portion 2 is formed is carried into the vacuum chamber of the plasma etching apparatus, and plasma etching is performed under reduced pressure. As shown in FIG. 1 (c),
Ions and electrons generated by the plasma collide with the surface of the solder portion 2 (see arrow a) to remove the oxide film 2a generated on the surface of the solder portion 2. FIG. 1D shows a state in which the surface of the solder portion 2 has become a clean surface 2b due to plasma etching.

Next, an electronic component on which solder bumps are formed will be described. In FIG. 2A, the electrode 4 is formed on the upper surface of the electronic component 3. The electronic component 3 is sent to the plasma etching apparatus and subjected to the plasma etching treatment in the same manner as the base material 1 described above. Here, the oxide film 4a and the foreign matter on the surface of the electrode 4 are removed by collision of ions and electrons (see arrow b), and the surface of the electrode 4 becomes a clean surface 4b as shown in FIG. 2 (c). When the surface of the electrode 4 is covered with a material such as Au that does not generate an oxide film, plasma etching is not necessary for the electrode 4 and can be omitted.

Next, the front surface and the back surface of the base material 1 on which the solder portion 2 is formed are turned upside down, and the solder portion 2 faces downward. Thereafter, the base material 1 is transferred onto the electronic component 3 in this posture, and the solder portion 2 is aligned with the corresponding electrode 4. After that, as shown in FIG. 3A, the base material 1 is pressed against the electronic component 3 from above by the thermocompression bonding tool 5, and the base material 1 is heated by the heater incorporated in the thermocompression bonding tool 5. Thus, the solder portion 2 is transferred onto the electrode 4.

The heated and melted solder portion 2 is solder-bonded to the surface of the electrode 4. At this time, since the oxide film and the foreign matter are removed by the plasma etching on the bonding surface of the solder portion 2 and the electrode 4, the flux Good solder joining can be performed without the need for coating. The heating / pressing transfer step is preferably performed in a vacuum chamber or the like under a reduced pressure atmosphere.

After the solder portion 2 is melted in the heating process, as shown in FIG. 3A, the space between the lower surface of the base material 1 and the upper surface of the electronic component 3 is kept at a desired dimension h. The height of the thermocompression bonding tool 5 is controlled. After that, when heating is stopped after a predetermined time elapses, the solder portion 2 is cooled and solidified while maintaining the dimension h. Next, after raising the thermocompression bonding tool 5, the substrate 1
Is separated from the solidified solder portion 2. As a result, FIG.
As shown in (b), solder bumps 2'having a desired height h without variations are formed on the electrodes 4 of the electronic component 3.

The solder bumps 2'formed in this case
Has a flat top surface. When a spherical solder bump is required, it is possible to form the spherical solder bump 2 ″ as shown in FIG. 3C by sending the electronic component 3 to a reflow device and heating it. Is.

As described above, since a solder ball, which is expensive and difficult to handle during transfer, is not used as a solder supplying means for forming solder bumps, a flux is used to bond the supplied solder to the electrodes. Since it is not necessary to apply the above method, there is no need for cleaning after reflow, and a low-cost solder bump forming method can be realized.

The present invention is not limited to the above embodiment. For example, the present embodiment shows an example in which the solder portion 2 is formed on the tape-shaped base material 1. Instead, it may have a shape that is cut into a predetermined size and separated. Further, in the present embodiment, the electronic component 3
Although the example of forming the solder bumps 2'is shown above, the object on which the solder bumps are formed is not limited to this. For example, the solder bumps (pre-coated solder) are formed on the electrodes of the printed circuit board. Good.

[0019]

According to the present invention, the surface of the solder portion formed on the base material corresponding to the electrode position of the electronic component or the substrate on which the solder bump is formed is plasma-etched, and the solder portion is electronic component. Since the transfer is performed by heating and pressing onto the electrodes of the substrate or the substrate, the solder bumps can be formed without using the flux that was required in the conventional solder bump forming method. Therefore, the flux was used. The necessary post-reflow cleaning can be omitted. In addition, since high-priced solder balls are not used as a means for supplying solder to the electrodes, solder bumps can be formed at low cost, and by controlling the height of the thermocompression bonding tool during heating / pressing. Therefore, it is possible to form solder bumps having a desired height dimension without variations.

[Brief description of drawings]

1A is a process explanatory diagram of a solder bump forming method according to an embodiment of the present invention. FIG. 1B is a process explanatory diagram of a solder bump forming method according to an embodiment of the present invention. Process explanatory drawing of the solder bump formation method of one Embodiment (d) Process explanatory drawing of the solder bump formation method of one embodiment of this invention

FIG. 2A is a process explanatory diagram of a solder bump forming method according to an embodiment of the present invention. FIG. 2B is a process explanatory diagram of a solder bump forming method according to an embodiment of the present invention. Process explanatory drawing of the solder bump forming method of one embodiment

3A is a process explanatory diagram of a solder bump forming method according to an embodiment of the present invention. FIG. 3B is a process explanatory diagram of a solder bump forming method according to an embodiment of the present invention. Process explanatory drawing of the solder bump forming method of one embodiment

[Explanation of symbols]

1 base material 2 Solder part 2a oxide film 2'solder bump 3 electronic components 4 electrodes 5 Thermo compression tool

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/60 H05K 3/32 B23K 3/00

Claims (2)

(57) [Claims] 1. A step of forming a solder portion on a base material without using a solder ball corresponding to an electrode position of an electronic component or a substrate on which a solder bump is formed, and a surface of the solder portion. Removing the oxide film by plasma etching, aligning the solder portion of the base material with the electrodes of the electronic component or the substrate, heating the base material while pressing the electronic component or the substrate, and soldering the solder. Forming a solder bump by transferring the portion to the surface of the electrode. 2. After forming solder bumps by the transfer,
Spherical solder bumps by heating the electronic components
2. The structure according to claim 1, wherein
Solder bump formation method.