JP2002289732A - Method for flattening bump and method for manufacturing mounting substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for flattening bumps by which the life of a press plate is increased and flattening can be stably performed for the long term, and to provide a method for manufacturing a mounting substrate using this flattening method. SOLUTION: In the flattening method where the height of all bumps 3 is equalized by pressing a plurality of bumps 3 formed at terminals 2 of the surface of an interposer 1, the flattening is carried out by relatively moving a pressing part of the press plate 4 to press the bumps 3 for each interposer 1 so that the bumps 3 come in contact with the pressing surface within a prescribed range dispersedly. In manufacturing the mounting substrate, a plurality of bumps 3 are formed at the terminals 2 of the surface of the interposer 1, and by using the flattening method, a plurality of bumps 3 are pressed and thus the height of all the bumps 3 is equalized, and then the bumps 3 are aligned with bumps 6 formed on a lower surface of a semiconductor chip 5 and heated, so that the bumps 3, 6 are connected each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for bump flattening and a method for manufacturing a mounting substrate.

[0002]

2. Description of the Related Art With the recent miniaturization and high performance of electronic equipment, terminals are provided on the lower surface of a semiconductor chip and the upper surface of a substrate as an ultra-high-density mounting method.
2. Description of the Related Art A direct connection method of connecting (soldering) a semiconductor chip directly on a substrate is widely used.

FIG. 6 shows a typical example of such a system. A semiconductor chip 32 is mounted on an upper surface of a substrate 30 via an interposer 31 serving as a second substrate. The interposer 31 functions as a cushioning material for reducing a difference in thermal expansion coefficient between the semiconductor chip 32 (silicon chip) and the substrate 30 (glass epoxy).

On the lower surface of the semiconductor chip 32, a large number of terminals 33 are formed in a lattice as shown in FIG. On the other hand, corresponding to the semiconductor chip 32, the interposer 31
A large number of terminals are also formed in a grid on the upper surface of the substrate. The terminals on the upper surface of the interposer 31 are electrically connected to the terminals 35 on the lower surface, and the terminals 35 on the lower surface are connected to the substrate 30. In order to connect with the terminals 33 of the semiconductor chip 32, the terminals of the interposer 31 are provided with solder bumps 34 (small projections). In addition, the terminals 33 of the chip 32 are often provided with solder (bumps). Then, by positioning and heating both terminals of the chip 32 and the interposer 31, the bumps are connected to each other.

[0005] However, the terminals 33 on the lower surface of the semiconductor chip 32 and the corresponding terminals on the upper surface of the interposer 31 used in the ultra-high-density mounting method are extremely fine, with an interval between terminals of about 0.1 to 0.4 mm. Therefore, even a slight variation in the amount of solder is likely to cause mounting defects and the like. Therefore, bumps on the interposer are crushed by a press plate and flattened in order to suppress variations in the amount of solder and reduce mounting defects. This operation is called fluttering (or coining).

However, the interposer is conveyed to a certain position under the press plate, and the bump is pressed at a certain position on the press plate. Therefore, when a large number of interposers are subjected to the fluttering process, the interposer is set at a certain position on the press plate. It is liable to occur, to attach a solder piece to the portion, or to be damaged. If left unchecked, the flattening itself will be adversely affected, and the mounting quality may be degraded. For this reason, it is necessary to replace or repair the press plate relatively early, which has been a major factor in cost increase.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method of bump bump flattening, in which the life of a press plate is prolonged and fluttering can be performed stably for a long period of time, and a method of manufacturing a mounting board using the flattening method. The purpose is to provide.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the press plate and the substrate (such as an interposer) have been moved relative to each other so that the press plate has the same shape. Since the bumps do not hit the place, adverse effects such as settling, scratching, and adhesion of solder pieces on the press plate are reduced, and as a result, the life of the press plate is prolonged, and stable fluttering can be performed for a long period of time. This led to the completion of the present invention. That is, in the bump flattening method according to the present invention, when the plurality of bumps formed on the terminals on the substrate surface are pressed and the heights of all the bumps are made uniform, the bumps are dispersed on the press surface within a predetermined range. In this case, the pressing portion of the press plate that presses the bump is relatively moved for each substrate to perform fluttering.

In the present invention, it is particularly preferable that the relative movement is controlled based on a random number table. As a result, the bumps evenly hit the press surface within a predetermined range, and the life of the press plate can be prolonged.
Instead of the control using the random number table, the bump and the press surface may be relatively moved at a constant interval for each substrate. The relative movement range is determined by the interval between bumps, and one side or diameter per bump is 0.1 to 0.4.
It is preferably in the range of a square or a circle of mm.

The method for manufacturing a mounting board according to the present invention comprises the steps of forming bumps on terminals on the surface of the substrate, and flattening the plurality of bumps formed on the terminals on the surface of the substrate to make the heights of all the bumps uniform. And a wiring step of aligning the flattened bumps with the bumps formed on the lower surface of the semiconductor chip and heating the wires to connect the bumps. The flattening step includes the steps of: Is performed by moving the pressing portion of the press plate for pressing the bumps relative to each substrate so that the bumps are distributed.

As described above, since the bumps are dispersed and hit on the press surface for each substrate, the life of the press plate is prolonged, and the flattening can be stably performed over a long period of time. You. Further, the cost can be reduced by extending the life of the press plate.

In particular, in the manufacturing method of the present invention, after the flattening step and before the wiring step, the inspection step of measuring the diameter or area of the upper surface of the flattened bump and inspecting the amount of solder constituting the bump is performed. It is preferred to include.
In general, the amount of solder adhering to a terminal is not constant, and there is a possibility that a mounting failure or a connection failure may occur when the amount of solder is small or large. Whether the amount of solder is appropriate or not is usually determined by observing the solder height before fluttering, but it is not easy to inspect a fine solder height. In the inspection step in the present invention, it has been found that there is a correlation between the solder height before fluttering and the diameter or area of the upper surface of the bump after fluttering, and by simply measuring the diameter or area, it is easy to perform the inspection. It is possible to determine whether the amount of solder is excessive or insufficient.
It is also possible to inspect all the fluttered bumps.

[0013]

1A to 1E show an outline of a method for manufacturing a mounting board according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes the above-described interposer (substrate), and a terminal 2 (Ni / Au
(Plated Cu terminals, etc.) are formed in a grid at intervals of about 0.1 to 0.4 mm.

To manufacture a mounting substrate, first, solder is pre-coated on the terminals 2 on the interposer 1 to form bumps 3 (FIGS. 1A and 1B). Subsequently, the plurality of bumps 3 were pressed by a press plate 4 to perform flattening to equalize the heights of all the bumps 3 (FIG. 1C), and the flattened bumps 3 were formed on the lower surface of the semiconductor chip 5. The bump 6 is aligned and heated (FIG. 1 (d)), and connected to complete the mounting (FIG. 1 (e)). The connection portion is indicated by reference numeral 12.

In order to pre-coat solder on the terminals 2 arranged at a fine interval of about 0.1 to 0.4 mm, it is necessary to prevent the adjacent bumps 3 from coming into contact with each other. Instead of the method or the like, a method of chemically depositing solder on the terminal 2 is preferably adopted. In this method, as shown in FIG. 2, a mixed solution 8 of lead organic acid and tin is applied by a doctor blade 7 to the surface of the interposer 1 on which the terminals 2 are formed. At this time, tin is added in excess of the stoichiometric amount with the organic acid lead.
By heating after the application, due to the difference in ionization tendency between tin and lead (Sn> Pb), the following reaction formula (1):
According to (2), metallic lead precipitates and reacts with an excessive amount of tin to form a solder (lead / tin alloy).

Embedded image (In the formula, R represents a residue of an organic acid.) This solder is selectively deposited on the terminal 2 due to a difference in affinity between the resist surface on the surface of the interposer 1 and the terminal 2, and the solder deposit 9 is formed. Then, the bump 3 is obtained by cleaning the surface of the interposer 1 and removing the residual liquid.

In the bumps 3 formed in this manner, since the amount of solder is not constant for each terminal 2, the height of each bump 3 also differs. For this reason, it is necessary to flatten the bumps 3 to make the heights uniform. FIG. 3 shows a fluttering process for this purpose, in which the interposer 1 placed on the tray 11 is transported onto the gantry 10, and the press plate 4 is lowered from above, and the solder bumps 3 formed on the upper surface of the interposer 1 are formed. Is crushed to make the bumps 3 uniform in height. The press surface of the press plate 4 may be heated as needed.

In this embodiment, the bumps 3 are formed on the press plate 4.
As shown in FIG. 4, the pedestal 10 is moved to disperse the position where one bump 3 hits the press plate 4 within the range A in order to disperse the position where the bump hits. The movement of the gantry 10 can be performed by, for example, a combination of a slide means for horizontally moving the gantry 10 in the x direction and a slide means (not shown) for horizontally moving the gantry 10 in the y direction. The bump 3 can be moved to the position.

The moving range A is determined by the distance c between the bumps 3 and 3. For example, if the distance c is 0.25 mm, the moving range A is a circle having a diameter of 0.25 mm. Further, the movement range A is not limited to a circle, but may be a square having a side of 0.25 mm. In any case, it is necessary that the adjacent ranges A, A do not overlap each other, and if there is an overlapped portion, the set-up on the press plate 4 and the attachment of the solder pieces are more than those of the other non-overlapping portions. Also easily occur. The interval c between the bumps 3 is generally 0.1
Therefore, the moving range A is preferably a rectangular or circular range having a side or a diameter of 0.1 to 0.4 mm.

The slide means pushes and pulls the gantry 10 by, for example, engaging the tip of a male screw screwed and inserted into a fixed female screw with one end surface of the gantry 10 and rotating the male screw by a driving means such as a motor. And can be finely moved freely. Such a sliding mechanism is employed in a micrometer or the like, and is well known in the related art.

The driving means is controlled by control means. The control means is programmed with a random number table, and the gantry 10 is moved in the x direction and the y direction based on the random number table. Thereby, when the bumps 3 of a large number of interposers 1 are flattened by one press plate 4, the gantry 10 moves so that the press position of the bumps 3 changes for each press plate 4, and the bumps 3 are placed on the press plate 4. Since the contact is even within the range A, settling of the press surface, adhesion of solder pieces and generation of scratches are reduced, the life of the press plate 4 is prolonged, and the manufacturing cost of the mounting board can be reduced.

The same effect can be obtained by moving the press plate 4 without moving the gantry 10. Interposer 1 that is flattened by one press
Is not limited to one, and a plurality of interposers 1 may be fluttered simultaneously. In this case, the plurality of interposers 1 may be stacked side by side on one tray, or the plurality of interposers 1 may be divided and connected by post-processing.

After the flattening, the bump 3 is subjected to an inspection process.
To check whether the amount of solder on each bump 3 is appropriate or not.
Is preferred. Whether the amount of solder on bump 3 is appropriate or not
Normally, as shown in FIG.₁, H_Two, H_Three
Is measured and judged from this height, but less than 1 mm
It is difficult to measure the height of each bump 3
This is even more the case when a complete inspection of the pump 3 is required. There
The height is set to a constant value h by fluttering.₀Ba aligned
The bump 3 is observed from above, and the diameter d of each bump 3 is determined.₁, D _Two, D
_ThreeIs measured. Diameter d of bump 3 after fluttering₁, D
_Two, D_ThreeAnd the height h of the bump 3 before fluttering₁,
h_Two, H_ThreeHas a correlation with
If you create a dose line, the bump 3 after fluttering
The original height of the bump 3 can be easily known from the diameter.
You. As a result, whether the amount of solder of each bump 3 is appropriate or not is determined.
Can be easily determined. When inspecting all bumps 3
Is taken using an imaging device such as a CCD camera
The diameter d is obtained by image processing from the image₁, D_Two, D
_ThreeAnd automatically calculate the amount of solder
It is preferable to determine suitability. The diameter d of each bump 3
₁, D_Two, D_ThreeIn place of image processing, the area of each bump 3
The same effect can be obtained by any measurement.

After completing the inspection process, the semiconductor chip 5 is placed on the interposer 1, and the bumps 6 of the semiconductor chip 5 are aligned and connected so as to match the bumps 3 of the interposer 1, and are connected as shown in FIG. As shown in FIG.
Get. The connected interposer 1 is connected to the substrate 30 as shown in FIG.

Note that, without using the interposer 1, a flattened bump is provided on the substrate 30 of FIG.
The semiconductor chip 5 can be directly mounted on the substrate 30. Further, instead of the random number table in this embodiment, the same effect can be obtained by relatively moving the bump and the press surface at a constant interval for each substrate such as the interposer 1.

[0025]

According to the fluttering method of the present invention,
Dispersion of the bumps on the press surface prolongs the life of the press plate, and has an effect that fluttering can be stably performed over a long period of time. According to the method for manufacturing a mounting board according to the present invention, in the fluttering step, the life of the press plate is increased, and the fluttering can be stably performed over a long period of time.
This has the effect of reducing mounting defects, improving productivity, and reducing manufacturing costs.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method for manufacturing a mounting board according to the present invention.

FIG. 2 is an explanatory view showing a method of forming a bump.

FIG. 3 is an explanatory view showing a bump flattening method according to the present invention.

FIG. 4 is an explanatory diagram showing a range in which a bump pressing position according to the present invention moves.

FIG. 5 is a conceptual diagram for explaining an inspection process according to the present invention.

FIG. 6 is an explanatory diagram showing an ultra-high-density mounting method using an interposer.

FIG. 7 is an explanatory diagram showing a mounting surface of a semiconductor chip.

[Explanation of symbols]

 1 interposer 2 terminal 4 bump 5 semiconductor chip

Continued on the front page (72) Inventor Hiroshi Tanaka 671 Mizuashi, Noguchi-cho, Kakogawa-shi, Hyogo F-term (reference) in Harima Chemicals Co., Ltd. 5F044 KK17 KK19

Claims (7)

[Claims] 1. A flattening method for pressing a plurality of bumps formed on terminals on the surface of a substrate to equalize the heights of all bumps, wherein the bumps are dispersed and hit on a press surface within a predetermined range. A flattening method for bumps, characterized in that a pressing portion of a press plate for pressing bumps is relatively moved for each substrate and flattening is performed. 2. The method according to claim 1, wherein the relative movement is controlled based on a random number table. 3. The method according to claim 1, wherein the bump and the press surface relatively move at a constant interval for each substrate. 4. The method according to claim 1, wherein said substrate is an interposer.
4. The fluttering method according to any one of items 1 to 3. 5. The flattening method according to claim 1, wherein the relative movement range is a rectangular or circular range having a side or a diameter of 0.1 to 0.4 mm per bump. . 6. A step of forming a bump on a terminal on the substrate surface, and pressing a plurality of bumps formed on the terminal on the substrate surface,
Manufacturing of a mounting substrate including a flattening process for equalizing the height of all bumps, and a wiring process for aligning and heating the flattened bumps with bumps formed on the lower surface of the semiconductor chip to connect the bumps together. The method, wherein the flattening step is performed by relatively moving a pressing portion of a press plate that presses a bump for each substrate so that the bumps are dispersed and hit on a pressing surface within a predetermined range. Method of manufacturing a mounting board. 7. The manufacturing method according to claim 6, further comprising an inspection step of measuring a diameter or an area of an upper surface of the flattened bump and inspecting an amount of solder constituting the bump after the flattening step and before a connection step. Method.