JP2010161120A - Bump forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bump forming method for reducing thermal influence to an electronic component and efficiently removing a residue object from a mask member. <P>SOLUTION: The method comprises a filling process (a) for filling recesses 6 formed on a surface of the mask member 2 making a laser beam L pass through with a conductive paste P in a non-cured state, a superposing process (b) for superposing the mask member 2 and the electronic component 1 to superpose the conductive paste P filled in the recesses 6 and electrode 4 of the electronic component 1, a forming process (c) for melting and curing the conductive paste P and forming bumps 5 in the electrodes 4 by irradiating the laser beam L from the rear side of the mask member 2 and heating and cooling the conductive paste P in the recesses 6, and a removing process (e) for irradiating the mask member 2 with the laser beam L and removing the residue object of the conductive paste P stuck to the mask member 2. Thermal influence to the electronic component is reduced and the residue object can efficiently be removed from the mask member. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bump forming method, and more particularly, to a bump forming method in which a recess formed on a surface of a mask member is filled with an uncured conductive paste, and the conductive paste is melt-cured to form a bump on the electrode. .

Conventionally, a filling step of filling a concave portion formed on the surface of a mask member with an uncured conductive paste, and the conductive paste and the electronic component filled in the concave portion by overlapping the mask member and the electronic component. There is known a bump forming method including a polymerization step of polymerizing an electrode and a forming step of forming a bump on the electrode by melting and curing the conductive paste by heating and cooling the conductive paste.
As such a bump forming method, there is known a method in which the mask member is made of silicon and the mask member and the electronic component that are overlaid are heated in the forming process (Patent Document 1).
As another bump forming method, a through-hole is formed in the mask member, a transparent support member is polymerized on the back surface of the mask member, and the through-hole is filled with a conductive paste in the filling step. A method of heating a conductive paste in a short time by irradiating a laser beam from a support member side to a position of a through-hole filled with the conductive paste is known (Patent Document 2).
Further, in the bump forming methods of Patent Document 1 and Patent Document 2, residues such as flux contained in the conductive paste adhere to the mask member after the bump is formed, so that the mask member is cleaned after each bump formation. In other words, cleaning using a solvent or ultrasonic cleaning is performed (see column 0023 of Patent Document 1 and column 0020 of Patent Document 2).

Japanese Patent No. 3698223 Japanese Patent No. 3385872

However, in the case of the bump forming method of Patent Document 1, since the entire electronic component is heated, there is a problem that the bump cannot be formed on the electronic component having low heat resistance. In the case of the bump forming method of Patent Document 2, the residue is removed. When removing, the mask member and the support member must be separated, and there is a problem that handling is complicated.
Further, in the bump forming methods of Patent Documents 1 and 2, since cleaning is performed using a liquid, equipment for cleaning and drying is required, and an electronic component manufacturing apparatus is increased in size and requires a long cleaning time. There is also a problem.
In view of such a problem, the present invention provides a bump forming method capable of reducing the thermal influence on an electronic component and efficiently removing a residue from the mask member.

That is, the bump forming method according to the present invention fills the recess by filling the recess formed on the surface of the mask member with an uncured conductive paste and the mask member and the electronic component overlapped. And a forming step of forming a bump on the electrode by melt-curing the conductive paste by heating and cooling the conductive paste. In the forming method,
The mask member is a transparent material that transmits laser light,
In the forming step, the conductive paste in the recess is heated by irradiating a laser beam from the back side of the mask member,
After the forming step, a removing step of removing a residue of the conductive paste attached to the mask member by irradiating the mask member from which the electronic component has been removed with laser light is performed.

According to the present invention, when the mask member is made of a transparent material and the recess is formed on the surface of the mask member, the conductive paste filled in the recess can be obtained by irradiating the laser beam from the back side of the mask member. It is possible to form bumps by heating.
For this reason, bumps can be formed even on electronic components with low heat resistance, the handling of the mask member is simple, and the residue adhering to the mask member is removed by laser light. Therefore, it is possible to efficiently remove the residue.

Side view showing electronic parts and mask member The figure which showed the process of the bump formation method concerning 1st Example. The figure which showed the process of the bump formation method concerning 2nd Example.

The illustrated embodiment will be described below. FIG. 1 shows an electronic component 1 on which bumps are formed by the bump forming method according to this embodiment, and a mask member 2 used in the bump forming method.
The electronic component 1 includes an insulating or semiconductor substrate 3 made of resin, silicon, or the like, and conductive electrodes 4 made of a plurality of metals provided on the substrate 3 in a predetermined arrangement. A conductive bump 5 made of solder is formed on one electrode 4 by a bump forming method shown in FIG.
The bump 5 is formed in a quadrangular pyramid shape with a base of about 50 μm and a height of about 70 μm, and by forming the bump 5 in a quadrangular pyramid shape, electrical bonding when the electronic component 1 is bonded to another electronic component is ensured. It is supposed to be.
The mask member 2 is made of glass that transmits laser light, and a plurality of recesses 6 are formed on the upper surface in the drawing in accordance with the arrangement position of the electrodes 4. The concave portion 6 is formed so that the base of the quadrangular pyramid opens on the surface of the mask member 2.
A DLC film 7 (diamond film) having a predetermined thickness (about 0.1 to 0.5 μm) is formed on the surface of the mask member 2 and the inner surface of the recess 6. The DLC film 7 has a water repellency and is a material that easily absorbs laser light and has high thermal conductivity.

FIG. 2 is a process diagram of the bump forming method according to the present embodiment. In this bump formation method, an electronic component 1 manufacturing apparatus (not shown) is used, and this manufacturing apparatus includes a vacuum chamber (not shown) and a heating chamber (not shown). It comes to be carried in and out.
First, FIG. 2A shows a filling process of filling the recess 6 of the mask member 2 with the conductive paste P. This filling process is performed in the vacuum chamber, and the mask member 2 has the recess 6 upward. It is supported in the vacuum chamber in the state of facing.
The conductive paste P is composed of particulate lead-free solder and a solvent containing flux, and is supplied to the surface of the mask member 2 in an uncured paste state in this filling step. .
The vacuum chamber was formed on the surface of the mask member 2 by sliding the squeegee 8 along the surface of the mask member 2 from one end to the other end of the surface of the mask member 2 in a vacuum state. The recess 6 is filled with a conductive paste P.
At this time, since the vacuum chamber is in a vacuum state, air is prevented from entering when the conductive paste P is filled in the concave portion 6, and the formation failure of the bump 5 is prevented. .

FIG. 2B shows a polymerization process in which the mask member 2 and the electronic component 1 are polymerized.
When the conductive paste P is filled in the concave portion 6 of the mask member 2 by the filling step, the electronic component 1 is transported into the vacuum chamber with the electrode 4 facing downward, and the conductive material filled in the concave portion 6 is filled. The paste P and the electrode 4 of the electronic component 1 are aligned so as to overlap and placed on the upper surface of the mask member 2.
As a result, the conductive paste P adheres to the electrode 4 of the electronic component 1, but the conductive paste P is in an uncured state, and the bumps 5 are not formed on the electrode 4.
The polymerization step may be performed in the vacuum chamber or in the heating chamber.

FIG. 2C shows a forming process for forming the bump 5 on the electronic component 1.
When the electronic component 1 and the mask member 2 are transported to the heating chamber in a polymerized state, the laser beam L is transmitted from the mask member 2 side through the mask member 2 and irradiated onto the DLC film 7 by a laser irradiation means (not shown). .
As a result, the laser beam L is absorbed by the DLC film 7 formed on the surface of the mask member 2 and the inner surface of the recess 6, the DLC film 7 is heated, and the conductivity filled in the recess 6 through the DLC film 7 is obtained. The paste P is heated.
When the conductive paste P is heated to the melting temperature of the solder (about 220 ° C.), the particulate solder in the conductive paste P melts and is attracted to each other by surface tension, and adheres to the electrode 4. The flux is pushed outward.
At this time, the irradiation range of the laser beam L is set so as to include all of the recesses 6 corresponding to the electrodes 4 formed on at least one electronic component 1, and thereby, in all the recesses 6 within the irradiation range. The conductive paste P can be heated all at once.
On the other hand, the irradiation range of the laser beam L includes the surface portion of the mask member 2 where the recess 6 is not formed, but in order to prevent the laser beam L from being directly irradiated onto the substrate 3 by the DLC film 7, The influence of heat on the electronic component 1 is reduced.
In this way, when the laser beam L is applied to the DLC film 7 and the conductive paste P in the recess 6 is heated and the solder is melted, the laser irradiation unit stops the irradiation of the laser beam L.
Then, when the conductive paste P filled in the recess 6 is cooled and falls below the solidification temperature (about 217 ° C.) of the solder, the solder is cured and firmly joined to the electrode 4, thereby forming a quadrangular pyramid on the electrode 4. A bump 5 is formed.

FIG. 2 (d) shows a separation process for separating the mask member 2 and the electronic component 1.
If the temperature of the conductive paste P is lower than the solidification temperature of the solder in the forming step, the solder of the conductive paste P is cured and the bumps 5 are formed, while the flux is not cured.
If the electronic component 1 and the mask member 2 are separated from each other in this state, the flux is not hardened. Therefore, the bump 5 is easily detached from the concave portion 6 of the mask member 2, and the electronic component 1 and the mask member 2 are removed. And can leave.
Thereafter, the flux is cured by further lowering the temperature of the conductive paste P, but the flux adhering to the recess 6 of the mask member 2 is also cured.
Then, the electronic component 1 detached from the mask member 2 in the separation process is transported to the subsequent process.

FIG. 2E shows a removal process for removing the flux adhering to the DLC film 7 from the mask member 2.
Between the vacuum chamber (not shown) and the heating chamber, a second laser irradiation unit (not shown) having a linear irradiation range extending in the direction orthogonal to the transfer direction is provided on the transfer path of the mask member 2. ing.
When the electronic component 1 and the mask member 2 are separated from each other by the separation process, the mask member 2 is transferred from the heating chamber to the vacuum chamber. At that time, the laser beam L is irradiated from the surface side of the mask member 2 by the second laser irradiation means.
As a result, the flux adhering to the inner surfaces of all the recesses 6 is heated and evaporated by the laser beam L, and the residue of the conductive paste P is removed from the mask member 2.
Then, after the mask member 2 is transported to and supported by the vacuum chamber, bump formation is performed on the next electronic component 1.

According to the above embodiment, the laser beam L is transmitted through the mask member 2 from the back surface side of the mask member 2 and irradiated in the forming step, so that the laser beam L is conductive in the recess 6 formed on the surface of the mask member 2. The conductive paste P can be heated, and the thermal influence on the electronic component 1 can be reduced.
Further, by irradiating the mask member 2 with the laser beam L in the removing step, the flux as the residue adhering to the concave portion 6 can be removed in a short time. The residue from the member 2 can be efficiently removed. In addition, since a liquid cleaning device is not necessary, the electronic device 1 manufacturing apparatus can be downsized.
Furthermore, the conductive paste P can be heated through the DLC film 7 by forming the DLC film 7 on the surface of the mask member 2 and the inner surface of the recess 6 and irradiating the DLC film 7 with the laser light L. . Further, the DLC film 7 can prevent the laser light L from being directly irradiated onto the substrate 3.
Then, by setting the irradiation range of the laser light L so that all the concave portions 6 are included, a plurality of bumps 5 can be simultaneously formed in a short time, and the bumps 5 can be efficiently formed. It is possible.

FIG. 3 is a process chart of a bump forming method according to a second embodiment of the present invention.
The conductive paste P used in this embodiment contains Cu and Ni, and it is necessary to heat the conductive paste P to about 700 ° C. in order to form the bumps 5 in the above formation process.
For this reason, in this embodiment, the DLC film 7 having a heat resistant temperature of about 500 ° C. cannot be used. In this embodiment, the DLC film 7 as in the first embodiment is formed on the surface of the mask member 2. It has never been.
In this embodiment, the steps shown in FIGS. 3A, 3B, 3D, and 3E are the same filling steps as those in the first embodiment except that the DLC film 7 is not formed. The detailed description is omitted because it is a polymerization step and a separation step.

In the formation process of the present embodiment shown in FIG. 3C, the laser irradiation means (not shown) irradiates the laser beam L from the back surface side of the mask member 2 as in the first embodiment. Is set to the size of the opening of each recess 6.
Then, the laser light irradiation means switches the irradiation position of the laser light L by the scanning means (not shown) in the order of arrangement of the concave portions 6, and sequentially irradiates the conductive paste P in each concave portion 6 with the laser light L. The light L is not directly irradiated.
When the laser beam L is irradiated, the conductive paste P in the recess 6 is heated to the above 700 ° C., so that Cu and Ni in the conductive paste P are attracted while melting.
And by stopping the irradiation of the laser beam L and cooling the conductive paste P, the bumps 5 are formed on the electrode 4, and the separation step shown in FIG. 3D is performed before the flux is hardened, The electronic component 1 and the mask member 2 are separated.

According to the second embodiment, even the conductive paste P containing Cu or Ni having a high melting point can be formed on the bump 5, and the electronic component 1 is heated by laser light L irradiation. It is possible to prevent being affected.
Further, similarly to the first embodiment, the flux adhering to the mask member 2 can be removed by the irradiation of the laser beam L, and the flux can be removed efficiently. It is possible to reduce the size.

  In the removing step in the first embodiment, the laser light irradiation range may be set to include a plurality of recesses 6 as in the forming step. In this case, the laser irradiation means used in the formation process can be used in the removal process.

DESCRIPTION OF SYMBOLS 1 Electronic component 2 Mask member 4 Electrode 5 Bump 6 Recess 7 DLC film P Conductive paste L Laser beam

Claims (4)

A filling step of filling a concave portion formed on the surface of the mask member with an uncured conductive paste, a conductive paste filled in the concave portion by overlapping the mask member and the electronic component, and an electrode of the electronic component; In a bump forming method comprising: a polymerization step of polymerizing, and a formation step of forming a bump on the electrode by melting and curing the conductive paste by heating and cooling the conductive paste,
The mask member is a transparent material that transmits laser light,
In the forming step, the conductive paste in the recess is heated by irradiating a laser beam from the back side of the mask member,
A bump forming method comprising performing a removing step of irradiating the mask member from which the electronic component has been removed with laser light after the forming step to remove a residue of the conductive paste adhering to the mask member. Forming a DLC film on the surface of the mask member and the inner surface of the recess,
In the forming step, when the DLC film is irradiated with laser light from the back side of the mask member, the DLC film is heated to heat the conductive paste in the recess,
2. The bump forming method according to claim 1, wherein, in the removing step, the DLC film is irradiated with laser light from the surface side of the mask member to remove the residue attached to the DLC film.   3. The bump forming method according to claim 1, wherein in the forming step, an irradiation range of the laser beam is set so that the plurality of recesses are irradiated with the laser beam. 4.   3. The method according to claim 1, wherein, in the forming step, the laser light irradiation range is set so that one concave portion is irradiated with the laser light, and the irradiation position of the laser light is scanned. A bump forming method according to claim 1.

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