JP2002134894A - Solder bump forming apparatus and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder bump forming apparatus and solder bump forming method which can form effectively stable solder bumps. SOLUTION: The solder bumps are formed by printing solder paste on an electrode of a substrate 16 by using off-contact printing, and solder-bonding solder component on the electrode by reflow. In the case of the off-contact printing, a mask plate 17a is used in which two sides 17e parallel with a printing direction out of four sides of the peripheral parts are free ends which are not restrained. A squeegee 21 is made to abut against an upper surface of the mask plate 17a and slid in the state that the squeegee is pressed against an upper surface of the substrate 16. The solder paste is printed on the substrate 16 via a pattern hole formed in the mask plate 17a. As a result, it is prevented that the squeegee 21 is lifted up in end portions of the substrate 16 by a tensile force of the mask plate 17a, so that the solder paste can be printed with stable printing precision.

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 apparatus and a solder bump forming method for forming solder bumps by printing solder paste on electrodes of a work.

[0002]

2. Description of the Related Art As a method of forming a solder bump, which is a protruding electrode of solder, on an electrode of a work such as an electronic component or a substrate,
There is known a method in which a solder component is supplied as a solder paste onto an electrode and soldered to the electrode. This method supplies a solder paste containing solder particles on an electrode by printing,
Next, the solder particles are melted by heating and joined to the electrodes to form solder bumps on the electrodes.
Screen printing is widely used as a method of supplying a solder paste on an electrode. For fine-pitch patterns such as solder bumps, contact printing is used in which printing is performed with the work in close contact with the lower surface of the mask plate. Here, in order to form the solder bumps efficiently, it is desirable to perform the screen printing for printing the solder paste as fast as possible.

[0003]

However, in screen printing, it takes time to remove the printing plate after printing, and it is difficult to print the solder paste on the electrodes at high speed and stably. For this reason, the conventional method of forming a solder bump using a solder paste has a problem that it is difficult to efficiently and stably form a bump.

Accordingly, an object of the present invention is to provide a solder bump forming apparatus and a solder bump forming method capable of efficiently forming a stable quality solder bump.

[0005]

According to a first aspect of the present invention, there is provided an apparatus for forming a solder bump, comprising: printing a solder paste on an electrode of a work; and heating and melting a solid solder component in the solder paste to form the solder bump on the electrode. An apparatus for forming a solder bump to be formed, comprising: a work holding unit that holds a work; and a printing unit that prints a solder paste on the held work by off-contact printing. A mask plate having a pattern hole corresponding to a printing portion and two free edges of two sides parallel to the printing direction among the four sides of the peripheral portion being free ends is not restricted. A squeegee pressed against the upper surface of the work, and the squeegee is slid in the printing direction along the upper surface of the mask plate to form the work through the pattern hole. And a squeegee moving means for printing solder paste on poles.

According to a second aspect of the present invention, there is provided a method of forming a solder bump.
A solder bump forming method in which a solder paste is printed on an electrode of a work and then a solid solder component in the solder paste is heated and melted to form a solder bump on the electrode. In a printing step of printing a solder paste by off-contact printing, a pattern hole corresponding to a print portion of a work is provided, and two sides parallel to the printing direction among four sides of a peripheral portion are free ends which are not restricted. A squeegee is brought into contact with the upper surface of the plate, the mask plate is pressed against the upper surface of the work, and the squeegee is slid in the printing direction along the upper surface of the mask plate, so that the squeegee is soldered to the work electrode through the pattern hole. Print the paste.

According to the present invention, in a printing step of printing a solder paste on a work by off-contact printing, two sides parallel to the printing direction among the four sides of the peripheral portion are free ends which are not restricted. A squeegee is brought into contact with the upper surface of the plate and pressed against the upper surface of the work, and the squeegee is slid to print solder paste on the electrodes of the work through the pattern holes provided in the mask plate, thereby forming an end of the mask plate. It is possible to prevent the squeegee from being lifted up in the portion and print the solder paste efficiently and with stable printing accuracy.

[0008]

FIG. 1 is a front view of a solder bump forming apparatus according to a first embodiment of the present invention, and FIG. 2 is a printing section of the solder bump forming apparatus according to the first embodiment of the present invention. 3 and FIG. 4 are process explanatory diagrams of a solder paste printing method according to the first embodiment of the present invention, and FIG. 5 is process explanatory diagrams of a solder bump forming method according to the first embodiment of the present invention. is there.

First, the structure of a solder bump forming apparatus will be described with reference to FIG. In FIG. 1, a printing unit 2 is provided on a base 1.
And a reflow unit 3. The printing unit 2 will be described. A moving table including an X table 5 and a Y table 6 is provided on the base 1, and a base plate 7 is mounted on the Y table 6. An elevating guide section combining a rod 9 and a guide 8 is erected on the base plate 7, and an elevating plate 11 is connected to the upper end of the rod 9.

The elevating plate 11 is raised and lowered by an elevating mechanism 10 arranged on the base plate 7, and a substrate holding part 12 for holding a substrate 16 as a work is mounted on the elevating plate 11. Also, column members 13 are provided upright at both ends of the base plate 7, and the upper end of the column members 13 supports a substrate transport unit 14A having a conveyor mechanism. Upstream side of substrate transport section 14A (left side in FIG. 1)
Is provided with a carry-in unit 15 having a similar conveyor mechanism, and a substrate 16 supplied from a loader (not shown) is carried into the printing unit 2 by the carry-in unit 15. By driving the X table 5, the substrate transport unit 14A moves in the direction of arrow a, whereby the substrate transport unit 14A is connected to the loading unit 15. The substrate 1 transported from the upstream side on the loading unit 15
6 moves onto the substrate transfer section 14A in this state.

A screen printing mechanism having a screen mask 17 is provided above the substrate transport section 14A. Above the screen mask 17, a moving table 18 for horizontally moving the print head 19 is provided. The print head 19 includes a pair of squeegees 21 that move up and down by a cylinder 20. When the substrate 16 is positioned below the mask plate 17a of the screen mask 17 and the elevating mechanism 10 is driven, the substrate 16 held by the substrate holding unit 12 rises to a predetermined height and is held at that position.

Then, a solder paste in which a solid solder component such as solder particles is mixed in a flux is supplied onto the mask plate 17a, and the squeegee 21 is lowered onto the mask plate 17a. As a result, the squeegee 21 comes into contact with the upper surface of the mask plate 17a, deflects the mask plate 17a downward and presses the upper surface of the substrate 16. By driving the moving table 18 in this state, the squeegee 21 slides on the mask plate 17a. As a result, the mask plate 17a is
The solder paste is printed on the substrate 16 through the pattern holes 17d (see FIGS. 3 (b) and 3 (c)).

That is, the screen printing mechanism shown in the present embodiment prints the solder paste on the substrate 16 which is the work held by the substrate holding unit 12 by off-contact printing without bringing the mask plate 17a into close contact. . The moving table 18 serves as squeegee moving means for moving the squeegee 21.

Referring now to FIG. 2, the structure of the screen mask 17 will be described. As shown in FIG. 2, the screen mask 17 has a structure in which a mask plate 17a is held by a rectangular frame holder 17b via a tension film 17c.
The two sides 17e that are parallel to (direction) are free ends that are not restricted in both the vertical and horizontal directions. A rectangular frame A indicated by a chain line is
The drawing shows the formation range of the pattern holes 17d corresponding to the printing range where the solder paste is printed on the substrate 16, and in the formation range, a large number of circular pattern holes 17d are formed in a lattice shape.

Next, the reflow unit 3 will be described. FIG.
A heating chamber 3a is provided downstream of the printing unit 2 on the base 1, and a substrate transport unit 14B is disposed in the heating chamber 3a in the horizontal direction. By driving the X table 5 of the printing unit 2 to move the substrate transport unit 14A in the direction of arrow b, the substrate transport unit 14A is connected to the substrate transport unit 14B, and the substrate 16 on the substrate transport unit 14A is moved to the substrate transport unit. 14
It is possible to transfer onto B. A heater 23 and a fan 24 are provided above the substrate transfer section 14B in the heating chamber 3a.
Are arranged.

The substrate 16 delivered from the printing unit 2 is heated by the heater 23 while being transported on the substrate transport unit 14B. As a result, the printed solder paste is soldered to the electrodes 16a (see FIG. 3) of the substrate 16 to form solder bumps. The substrate 16 after the formation of the solder bumps
The wafer is transferred from the substrate transfer section 14B to the unloading section and unloaded to the downstream side.

This apparatus for forming solder bumps is configured as described above, and a method for forming solder bumps will be described below. First, screen printing performed in the printing unit 2 will be described with reference to FIG. Here, the substrate 16
The solder paste 22 is printed on the electrode 16a formed on the substrate. As shown in FIG. 1, the substrate holding portion 12 holding the substrate 16 is positioned at a predetermined position below the mask plate 17a to which the solder paste 22 has been supplied in advance.

The predetermined position is a position where the position of the electrode 16a matches the position of each pattern hole 17d of the mask plate 17a as shown in FIGS. 3 (b) and 3 (c). Then, the substrate holding unit 12 is raised, and the upper surface of the substrate 16 is positioned below the mounting level L of the mask plate 17a and separated by a predetermined height h (see a two-dot chain line in FIG. 1). When the squeegee 21 coupled to the lower end of the rod 20a of the cylinder 20 is lowered with respect to the mask plate 17a, the mask plate 17a bends downward, and the lower end of the squeegee 21 presses the mask plate 17a against the substrate 16. In this state, by moving the squeegee 21 in the printing direction, the solder paste 22 is scraped and filled into the pattern holes 17d of the mask plate 17a.

As shown in FIG. 3B, when the tip of the squeegee 21 moves on the pattern hole 17d, the solder paste 22a filled in the pattern hole 17d is formed.
Is printed on the electrode 16a. Thereafter, as shown in FIG. 3C, after the squeegee 21 has passed, the mask plate 17a is displaced in the direction of returning to the original mounting level L, so that the solder paste 22 in the pattern hole 17d is removed.
a while leaving a on the electrode 16a.
Only the substrate 16 is separated from the substrate 16.

FIG. 4A shows a cross section (a cross section in a direction perpendicular to the printing direction) of the printing unit 2 along the squeegee 21 in the off-contact printing process described above. FIG.
As shown in (a), the squeegee 21 fixed to the squeegee holder 21a is lowered by driving the cylinder 20, and abuts on the upper surface of the mask plate 17a.
Press At both ends of the squeegee holder 21a,
The side blade 21b has a lower end portion on the mask plate 17a.
Is attached in contact with the upper surface of the
This prevents the solder paste 22 (see FIG. 3) supplied on 7a from spilling from the side during the printing process.

The mask plate 17 in the present embodiment
a, the two sides 17e parallel to the printing direction are free ends without being restrained.
When pressed against the upper surface of 7a and bent downward, the mask plate 17a is evenly pressed by the squeegee 21 over the entire area of the substrate 16.

FIG. 4B shows a conventional mask plate 1.
The contact state between the mask plate 17'a and the substrate 16 when the same off-contact printing is performed using 7 'is shown for comparison with the present embodiment. FIG.
As shown in (b), the conventional mask plate 17'a
Means that the holder 1 has a peripheral portion on all four sides by a tension film.
7'b, the squeegee 2
In the state where the mask plate 17'a is bent downward in Step 1, the squeegee 21 is partially lifted around the end of the substrate 16 by the tension of the mask plate 17'a, and the There is a gap between them.

When the solder paste is printed by moving the squeegee in this state, the amount of the solder paste printed on the substrate 16 is larger in the range where the mask plate 17'a is lifted than in other ranges. It was too large to maintain stable print quality. In order to prevent this, conventionally, the screen mask 17 in the longitudinal direction of the squeegee 21 is used.
Was wide enough. On the other hand, in the present embodiment, the phenomenon that the squeegee 21 is lifted by the tension of the mask plate 17a does not occur as shown in FIG. Solder printing can be performed. Furthermore, the screen mask 1 in the longitudinal direction of the squeegee 21
Since the width of 7 can be reduced, the size of the device can be reduced.
In addition, off-contact printing does not require time for blanking, so printing can be performed on a single board in a short time, and printing efficiency can be improved while ensuring print quality. And

Screen printing is performed in this manner,
As shown in FIG. 5A, the solder paste 2 is formed on the electrode 16a.
The substrate 16 on which 2a is printed is transferred from the printing section 2 to the reflow section 3
Move to. Therefore, as shown in FIG.
As a result, the solder component in the solder paste 22a is melted. Thereafter, the molten solder is soldered to the electrode 16a and solidified, so that a solder bump 22b is formed on the electrode 16a as shown in FIG. 5C. In the process of forming the solder bumps, the solder paste is uniformly printed on each electrode 16a of the substrate 16, so that the formed solder bumps 22b have a uniform size without variation.

(Embodiment 2) FIG. 6 is a front view of a solder bump forming apparatus according to Embodiment 2 of the present invention, and FIG. 7 is a process explanatory view of a solder bump forming method according to Embodiment 2 of the present invention.
In the first embodiment, the example in which the substrate 16 on which the solder paste is printed is sent to the reflow step as it is, but in the second embodiment, a larger solder ball is mounted on the substrate 16 on which the solder paste is printed. A solder bump having a size is formed.

In FIG. 6, a ball mounting section 4 is provided between the printing section 2 and the reflow section 3 on the base 1.
The ball mounting section 4 is provided with a support 25 for supporting the base plate 7 on the base 1. Base plate 7
The parts mounted thereon (members indicated by reference numerals 7 to 13) support the substrate holding unit 12 in the same configuration as the printing unit 2 so as to be able to move up and down, and support the substrate transport unit 14C. By driving the X table 5 of the printing unit 2 to move the substrate transport unit 14A in the direction of arrow b, the substrate transport unit 14A is connected to the substrate transport unit 14C, and the substrate 16 on the substrate transport unit 14A is moved to the substrate transport unit. It is possible to transfer to 14C.

A ball mounting mechanism is provided above the substrate transport section 14C. The ball mounting mechanism includes an X-axis table 27 provided on two Y-axis tables 26, and a Z-axis table 28 is connected to the X-axis table 27. A lifting block 29 is mounted on the Z-axis table 28, and a transfer head 30 for transferring solder balls is mounted on a lower end of the lifting block 29.

The substrate 16 is held at a predetermined height by positioning the substrate 16 on the substrate transport section 14C and raising the substrate holding section 12 by the elevating mechanism 10. A solder ball is sucked and picked up from a ball supply unit (not shown), and the ball mounting unit 4 is held in a state where the solder ball is sucked and held.
The transfer head 30 having moved to above is lowered onto the substrate 16,
By releasing the suction state, the solder balls are transferred onto the substrate 16.

Next, a method of forming solder bumps will be described. As shown in FIG. 7A, each electrode 16a of the substrate 16
The solder paste 22a is printed on the upper part. As shown in FIG. 7B, the transfer head 30 holding and holding the solder ball 31 is positioned and lowered with respect to the substrate 16, and the suction of the solder ball 31 is released. As shown in c), the solder ball 31 is mounted on the solder paste 22a printed on the electrode 16a.

Thereafter, the substrate 1 on which the solder balls 31 are mounted
6 is sent to the reflow section 3 and heated. As a result, the solder component and the solder ball 31 in the solder paste 22a are melted and soldered to the electrode 16a to form the solder bump 31a.
Is formed. In the second embodiment, a larger amount of solder is supplied on the electrode 16a by the amount of the solder ball 31 than in the first embodiment, so that a larger-sized solder bump 31a is formed.

[0031]

According to the present invention, in the printing step of printing a solder paste on a work by off-contact printing, two sides parallel to the printing direction among the four sides of the peripheral portion are free ends which are not restricted. Since the squeegee is brought into contact with the upper surface of the mask plate and pressed against the upper surface of the work, the squeegee is slid to print the solder paste on the electrodes of the work through the pattern holes provided in the mask plate. It is possible to prevent the squeegee from lifting at the end of the mask plate, and to print the solder paste efficiently and with stable printing accuracy.

[Brief description of the drawings]

FIG. 1 is a front view of a solder bump forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a screen mask of a printing unit of the solder bump forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a process explanatory view of the solder paste printing method according to the first embodiment of the present invention;

FIG. 4 is a process explanatory view of the solder paste printing method according to the first embodiment of the present invention;

FIG. 5 is a process explanatory view of the solder bump forming method according to the first embodiment of the present invention;

FIG. 6 is a front view of a solder bump forming apparatus according to a second embodiment of the present invention.

FIG. 7 is a process explanatory view of the solder bump forming method according to the second embodiment of the present invention;

[Explanation of symbols]

 Reference Signs List 16 substrate 17 screen mask 17a mask plate 17d pattern hole 21 squeegee 22, 22a solder paste 22b, 31a solder bump

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) B41F 15/36 B41F 15/36 Z H01L 21/60 B23K 101: 42 // B23K 101: 42 H01L 21/92 604E F-term (reference) 2C035 AA06 FA27 FC05 FC08 FC10 FD02 FD05 FD42 FD52 FE04 FF01 5E319 AA03 AC01 AC16 AC17 BB05 CC33 CD04 CD29 GG03 GG15

Claims (2)

[Claims] A solder bump forming apparatus for printing a solder paste on an electrode of a work and then heating and melting a solid solder component in the solder paste to form a solder bump on the electrode, the work holding the work. It has a holding part and a printing part for printing the solder paste on the held work by off-contact printing, and this printing part is provided with pattern holes corresponding to the printing part of the work, and has four sides of the peripheral part. A mask plate having two free ends that are not constrained parallel to the printing direction, a squeegee that contacts the upper surface of the mask plate and presses the mask plate against the upper surface of the work, and the squeegee is placed on the upper surface of the mask plate. Squeegee moving means for printing solder paste on the electrodes of the work through the pattern holes by sliding in the printing direction along The solder bump forming apparatus according to claim and. 2. A method of forming a solder bump on an electrode of a work by printing a solder paste on an electrode of the work and then heating and melting a solid solder component in the solder paste to form a solder bump on the electrode. In a printing step of printing a solder paste by off-contact printing on a worked work, a pattern hole corresponding to a printed portion of the work is provided, and two sides parallel to the printing direction among four sides of a peripheral edge are not restricted. A squeegee is brought into contact with the upper surface of the mask plate, and the mask plate is pressed against the upper surface of the work, and the squeegee is slid in the printing direction along the upper surface of the mask plate to pass through the pattern holes. A method for forming a solder bump, comprising printing a solder paste on an electrode of a work.