JPH0982719A - Method of flux transfer to electrode, manufacture of bump, and manufacturing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To definitely transfer flux only to an electrode by dipping the tip portion of a projection from a transfer substrate in a flux bath, sticking the flux to the tip portion, thereafter positioning the tip portion of the projection to the electrode, and transferring the flux to the electrode of the transfer target. SOLUTION: A flux transfer substrate 11 is lowered and only the tip portion of a projection 12 of the transfer substrate 11 is dipped in flux 22. The substrate 11 is lowered toward an electrode 32, and flux 23 stuck to it transferred to an electrode pad 23. Each eutectic solder ball 51 is aligned with the position of each electrode pad 32 on which the flux was transferred. Balls 51 are pressed by an array substrate 41. The substrate 31 is conveyed to a furnace, solder balls 51 are heated and melted being heated to above the melting point of the solder balls 51, thereafter, the flux is washed and a solder bump 52 is formed. By doing this, the sticking of flux to the array substrate and the dropping of fine metal balls from the array substrate can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transferring a flux onto an electrode, a method for producing a fine bump made of a low melting point alloy or a metal, and an apparatus for producing these.

[0002]

2. Description of the Related Art With the widespread use of portable information devices, portable video cameras and the like, there is a demand for small semiconductor packages. The number of electrodes tends to increase as the performance of LSIs increases.
As a method for realizing such a small size and multi-terminal mounting, there is a flip chip in which a chip is directly mounted on a substrate electrode having a narrow pitch. In addition, BGA (ball grid array) and CSP (chip size package) have been developed in which the terminals are arranged from the peripheral arrangement to the surface arrangement and the number of terminals is increased without extremely narrowing the pitch.

In any of the above cases, it is necessary to form a connection terminal (bump) made of a low melting point alloy such as solder or a metal on an electrode such as a substrate. A method of forming bumps using balls made of a low melting point alloy such as solder or metal is an effective bump forming method. When forming bumps from balls, it is necessary to transfer the flux to the electrodes and temporarily fix the balls to ensure sufficient bonding with the electrodes, and then heat and melt the balls at a temperature above their melting point to bond them to the electrodes. There is.

However, if the flux is transferred to a portion other than the electrode, there is a problem that the balls may flow down from the electrode during heating and melting. This can be avoided by transferring the flux only to the electrode part. That is, US Pat. No. 5,284,287 discloses the following method. Solder having a diameter of 500 to 700 μm is held by the array substrate, the array substrate is moved to a flux bath filled with flux while holding the balls, the array substrate is pushed down, and a part of the balls held there is placed in the flux. Dip and apply flux to it. Next, the balls to which the flux is attached are pressed from the array substrate to the substrate electrodes to be temporarily fixed. Therefore, the flux is supplied only to the electrodes on which the balls are temporarily fixed.
Even if this temporarily fixed ball is heated and melted, the ball does not flow down from the electrode.

[0005]

The method of transferring the flux only to the electrodes described above becomes difficult when the diameter of the ball is less than 500 μm. That is, as the balls become smaller, the distance between the array substrate holding the balls and the tip of the balls dipped in the flux becomes shorter, and there is a problem that the flux adheres to the array substrate when the balls are dipped in the flux bath. When the balls are held next time, the adhesion of the flux to the array substrate may cause the adhesion of the balls to that portion, which causes a decrease in the reliability of bump formation on the electrodes. Further, if the ball diameter becomes smaller, it becomes difficult to attach the flux to only a part of the ball with good controllability. That is, if too much flux is attached to the balls, the balls will fall from the array substrate into the flux bath due to the adhesive force.

The present invention is a method of forming a bump on an electrode of a substrate or the like with a ball having a diameter of less than 500 μm, a method of reliably transferring a flux only to an electrode portion, a method of manufacturing a bump using the same, and realizing them. A manufacturing apparatus for

[0007]

In order to solve the above-mentioned problems, according to the present invention, the protrusion tip portion of a transfer substrate having a protrusion corresponding to an electrode is dipped in a flux bath to attach the flux to the tip portion. After that, a method of aligning the tip of the protrusion with the electrode and then transferring the flux to the electrode to be transferred is provided. Further, the present invention transfers the flux to the electrode by the above method, and then holds the fine metal balls made of a low melting point alloy or metal collectively on the array substrate corresponding to the electrode, and then on the array substrate. After aligning the held fine metal balls with the flux-transferred electrodes, press the fine metal balls against the flux-transferred electrodes to temporarily temporarily fix them. Provided is a method for manufacturing a fine metal bump made of a low melting point alloy or metal on an electrode, which is characterized by heating and melting at the above temperature to bond solder to the electrode.

Further, according to the present invention, a transfer substrate having protrusions, a mechanism for adhering flux to the protrusion tips of the transfer substrate, a mechanism for aligning the protrusion tips with the electrodes, and the attachment are made. Provided is a flux transfer device for transferring an electrode of a semiconductor chip, a film carrier, or a substrate, which comprises a mechanism for transferring flux to the electrode. Further, a flux transfer device to the electrode, a mechanism for collectively holding the fine metal balls made of a low melting point alloy or metal on the array substrate corresponding to the electrodes, and the fine metal balls held on the array substrate. An apparatus for manufacturing fine metal bumps, comprising: a mechanism for aligning the electrodes, and a mechanism for pressing the fine metal balls against the electrodes to temporarily temporarily fix them.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a transfer substrate having protrusions corresponding to substrate electrodes is used. The tip of the protrusion of the transfer substrate is dipped in a flux bath, the flux is attached to the tip of the protrusion, the tip is aligned with the electrode, and then the flux is transferred to the electrode to be transferred. The present invention is intended for balls having a diameter of less than 500 μm, but can be effectively applied to balls having a diameter larger than that (for example, 760 μm).

Although various structures can be considered as the structure of the projection, it is necessary to attach a sufficient amount of flux to the tip of the projection to cover the electrode. Therefore, it is desirable that the cross-sectional area near the tip of the protrusion is the same as that of the electrode pad. Further, in order to easily immerse only the tip in the flux bath, its height needs to be 200 μm or more, preferably 500 μm or more, as shown in FIG. The shape of the tip of the protrusion of the transfer substrate may be flat or may have a curvature.

Any material can be used as the material of the flux transfer substrate as long as it can form a protrusion structure, and it can be made of ceramics such as glass, metal such as stainless steel, or plastic. The target on which the electrode for transferring the flux is formed is a semiconductor chip, a film carrier, a substrate, or the like. Here, the substrate may be a printed circuit board made of glass epoxy, glass, ceramics or the like, or a flexible board made of polyimide or the like. As the material for the fine bumps, solders of various compositions and melting points of 400 ° C
The following so-called low melting point alloys or metals can be used.

The flux transfer apparatus according to the present invention is basically constructed by the following mechanism in order to realize the above transfer method. 1. A transfer substrate having protrusions for transferring flux at positions corresponding to the electrodes. 2. A mechanism to immerse only the tip of the protrusion on the transfer substrate in the flux bath. 3. A mechanism that recognizes the position of the tip of the protrusion on the transfer substrate and the position of the electrode by image processing, and matches the positions of both. 4. A mechanism that transfers the flux to the electrode by moving the transfer substrate with the flux attached to the tip of the protrusion to the position of the electrode.

Here, as shown in FIG. 2A, a parallelizing mechanism made of an elastic body 62 may be added to the transfer head 61 which holds the transfer substrate 11 having the projections 12. In this case, even if the parallelism of the object such as the substrate to which the flux is applied is poor, the parallelism with respect to the object 63 can be obtained by the transfer head 61 as shown in FIG. Can be applied. Here, the elastic body may be a spring or a polymer material such as rubber.

If the flux is applied many times, the flux may adhere to the tip portions of the protrusions 12 on the transfer substrate 11. In such a case, a bath made of a solvent that dissolves the flux may be provided, and the tip portion of the transfer substrate may be immersed therein to remove the adhered flux. At this time, if ultrasonic waves are applied to the solvent, the removal efficiency increases.

The semiconductor manufacturing apparatus according to the present invention is basically configured with the following mechanism to realize the above bump manufacturing method. 1. A transfer device that transfers the above flux only to the electrodes. 2. A mechanism to collectively hold the fine metal balls from the mounting container at a position corresponding to the electrodes on the array substrate by suction, electrostatic force, magnetic force, or the like. 3. A mechanism that recognizes the positions of the fine metal balls and electrodes held on the array substrate by image processing, and matches them. 4. The semiconductor chip, film carrier, or substrate electrode set on the support is used to temporarily fix the metal balls held by the array substrate to the electrodes on which the flux has been transferred. mechanism.

Here, the transfer device for moving the transfer substrate up and down may be attached to a mechanism for moving the array substrate up and down and temporarily fixing it, or may be an independent device. When both are operated independently, the throughput of the device is improved and the productivity is increased. Further, when the balls are transferred to the electrodes, the array substrate may be moved to the position of the electrodes, or a semiconductor chip having an electrode or the like may be moved to the position of the array substrate. In addition to the above-mentioned mechanism, a semiconductor chip, a film carrier, or a substrate carrying-in mechanism may be additionally provided. Further, the image recognition and the like of the transfer device and the bump manufacturing device can be shared. Further, if a semiconductor chip, a film carrier, a substrate heating mechanism, or the like installed on the support table is additionally provided, the melting of the fine metal balls can be performed on the present manufacturing apparatus without being conveyed to a furnace or the like.

When the fine metal balls to be handled become small, extra balls other than the balls to be transferred due to static electricity may adhere to the array substrate or the balls held by the array substrate. This tendency tends to appear when the ball diameter is 300 μm or less,
In particular, it becomes remarkable when the diameter is 150 μm or less. In such a case, extra balls are avoided by adding an extra ball removing mechanism by ultrasonic vibration to the array head that holds the array substrate of the present semiconductor manufacturing apparatus, as disclosed in JP-A-7-226425. can do.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flux transfer method to only an electrode portion according to the present invention and a fine bump manufacturing method using the same will be described in detail with reference to the drawings. (A) of FIG.
(J) shows a flux transfer method only to the electrode portion according to the present invention and a solder bump manufacturing method using the flux transfer method. 350 electrodes are formed on a printed circuit board made of glass epoxy to be transferred. One electrode pad consists of a square of 50 μm square. The 350 electrode pads are formed at intervals of 100 μm pitch. Eutectic solder ball (Sn 60wt%, Pb 40wt%, melting point 188
The bumps are manufactured by using C. and a diameter of 45 μm). To transfer the flux only to the electrode part, a flux transfer substrate having a protrusion at the same position as the substrate electrode is used. In this embodiment, this flux transfer substrate is made of glass. The protrusion structure has a cross-sectional diameter of 50 μm and a height of 500.
It has a cylindrical shape of μm.

The method of transferring flux to the electrodes and the method of manufacturing fine ball bumps on the electrodes will be described below in the order shown in the figure. (A) The flux transfer substrate 11 is moved onto the flux bath 21 filled with the flux 22. (B) Flux The transfer substrate 11 is lowered toward the flux 22, and only the tips of the protrusions 12 of the transfer substrate 11 are immersed in the flux 22. (C) The transfer substrate 11 is pulled up, and the flux 23 is attached only to the tips of the protrusions 12. (D) The transfer substrate 11 is moved to a position above the electrode portion 32 of the substrate 31, and the tip end portion of the protrusion 12 and the electrode pad 32 are aligned. (E) The transfer substrate 11 is lowered toward the electrode 32, and the flux 23 is brought into contact with the electrode pad 32. (F) The flux 23 attached to the tip is attached to the electrode pad 32.
And the transfer substrate 11 is retracted. (G) After the eutectic solder balls 51 are collectively sucked and held by the array substrate 41 having the holes 42 smaller than the ball diameter corresponding to the electrodes, the balls 51 and the electrode pads 32 on which the flux 24 is transferred. Adjust the position. (H) The array substrate 41 is lowered toward the printed circuit board 31, and the array substrate 41 presses the balls 51. (I) The balls 51 are temporarily temporarily fixed to the electrodes on which the flux 24 has been transferred, and the array substrate 41 is retracted. (J) The substrate 31 in which the balls 51 are temporarily fixed to the electrodes 32 is conveyed to a furnace and is heated and melted at 200 ° C. which is higher than the melting point of the solder balls 51, and then the flux is washed to obtain a fine bond sufficiently bonded to the substrate electrode portion. The solder bumps 52 can be formed.

[0020]

As described above, according to the present invention,
It is possible to prevent the adhesion of the flux to the array substrate and the detachment of the fine metal balls from the array substrate when manufacturing the fine bumps by bonding the fine metal balls of less than 500 μm to the electrodes using the flux. Fine bumps can be manufactured by using fine metal balls made of a low melting point alloy or a metal on the electrodes to which the flux is reliably transferred. A semiconductor chip, a film carrier, to which such fine bumps are connected,
Alternatively, if a substrate is used, an electronic component having an extremely small area can be mounted with high productivity.

[Brief description of drawings]

FIG. 1 is a step of transferring a flux of the present invention ((a) to
FIG. 3F is a diagram schematically showing (f)) and bump manufacturing steps ((g) to (j)).

FIG. 2 is a diagram showing a parallelization mechanism by an elastic body of a transfer head that holds a protrusion-shaped transfer substrate of the present invention.

[Explanation of symbols]

 11 Flux Transfer Substrate 12 Protrusion Structure 21 Flux Bath 22 Flux 23 Flux Attached to Protrusion 24 Flux Transferred to Electrode 31 Printed Circuit Board 32 Electrode Pad 41 Array Substrate 42 Adsorption Hole 51 Low Melting Point Metal or Alloy Ball 52 Low Melting Point Metal or Alloy Bump 61 Transfer head 62 Elastic body 63 Flux application target

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/92 604H

Claims (4)

[Claims] 1. A method for transferring a flux to an electrode of a semiconductor chip, a film carrier, or a substrate by a transfer device, wherein a transfer substrate constituting the transfer device has a protrusion corresponding to the electrode, The tip of the protrusion of the substrate is immersed in a flux bath to attach the flux to the tip, and then the protrusion of the transfer substrate and the electrode are aligned, and then the attached flux is applied to the electrode. A method for transferring a flux to an electrode, which comprises transferring the flux to an electrode. 2. The method according to claim 1, wherein the flux is transferred to an electrode of a semiconductor chip, a film carrier, or a substrate, and then fine metal balls made of a low melting point alloy or metal are collectively held on the array substrate. After that, the fine metal balls held on the array substrate and the electrodes on which the flux has been transferred are aligned, and then the fine metal balls held on the array substrate are pressed against the electrodes on which the flux has been transferred. Temporarily fixing all at once, and then heating and melting the temporarily fixed fine metal balls at a temperature equal to or higher than the melting point to join the solder to the electrodes. Fine metal made of a low melting point alloy or metal on the electrodes. Bump manufacturing method. 3. A transfer substrate having protrusions, a mechanism for adhering flux to the protrusion tips of the transfer substrate, a mechanism for aligning the protrusion tips with the electrodes, and the attached flux for the electrodes. And a mechanism for transferring the flux to a semiconductor chip, a film carrier, or a flux transfer device to a substrate electrode. 4. An apparatus for transferring flux to an electrode according to claim 3, a mechanism for collectively holding fine metal balls made of a low melting point alloy or metal on the array substrate corresponding to the electrodes, and the array substrate. An apparatus for manufacturing fine metal bumps, comprising: a mechanism for aligning the held fine metal balls with the electrodes, and a mechanism for pressing the fine metal balls against the electrodes to temporarily temporarily fix them.