JPH07297238A - Flux transfer method - Google Patents

Abstract

PURPOSE:To obtain a flux transfer method for practical mass production, in relation to the transfer of fluxes to the pads whose patterns are formed at fine pitches on a board. CONSTITUTION:Transfer pin arrays 8, 9 for transferring fluxes to a plurality of pads are divided into two groups and are provided on a transfer unit 4. An aligning table 3 whereon the transfer unit 4 is mounted is moved, and thereby, the flux is stuck on the end parts of the transfer pins of the two groups independently of each other on a flux table 5, and thereafter, the transfer unit 4 is so moved that the fluxes are transferred to the pads.

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 for forming solder bumps onto a large number of pads patterned on a substrate to be processed.

The information processing apparatus has been increased in capacity because of the need to process a large amount of information quickly, and the semiconductor device, which is the main component of this apparatus, has been increased in capacity by reducing the size of a unit element. And VLSI have been put to practical use.

As a method of mounting an electronic circuit including these semiconductor devices, a large number of pads are provided on a ceramic multilayer circuit board, a plurality of flip chip type semiconductor devices are mounted on the pads, and vias (Via ), A circuit is connected to an electronic circuit formed in a pattern on the substrate, and the information processing apparatus is configured by using this as a replacement unit.

[0004]

2. Description of the Related Art Since the capacity of a semiconductor integrated circuit has been increased by miniaturizing a unit element rather than increasing the size of a board as described above, it is necessary to mount a semiconductor device on a multilayer circuit board. The size and pitch of the patterned pads are becoming smaller and smaller.

For example, until now, a pad of about 300 μm square has been used.
The pads are arranged in a matrix with a pitch of 450 μm, and each pad is connected to a multilayer circuit by a via.
Here, the pad differs depending on the constituent material of the conductor line that forms the multilayer circuit board, but when the conductor line is made of copper (Cu), the thickness of about 1000Å nickel (Ni) and gold (Au) are sputtered. A method of forming a pattern by performing selective etching using a photo-etching technique (photolithography) after stacking and forming by a method such as photolithography is adopted.

To mount the flip chip type integrated circuit on the pad thus formed,
First, flux is applied to a pad, solder bumps are formed on the pad, a semiconductor chip made of an integrated circuit is positioned, and heating and melting is performed using a tunnel furnace or the like to mount the semiconductor chip.

Here, in order to apply the flux to the pad formed on the substrate by patterning, conventionally, as shown in FIG. 3A, a predetermined number of transfer pins 1 of a predetermined size are arranged in a matrix form. The transfer pin row 2 arranged in the same figure is shown in FIG.
As shown in FIG. 5, the transfer pin row 2 is mounted on the transfer unit 4 on the positioning table 3. First, the positioning table 3 is moved to the position of the flux table 5 and then lowered, and applied with a squeegee to a constant thickness. Mark the existing flux with the transfer pin row 2 and transfer it to the transfer pin 1. Then,
As shown in FIG. 3C, after moving the positioning table 3 to the position of the substrate 6 to be processed, the transfer unit 4 is lowered and the flux is transferred onto the pad by the transfer pin row 2 to perform the application. It was

Since the transfer pin 1 needs to have a height of at least 400 μm, the transfer pin 1 shown in FIG.
As shown in (A), cutting is performed in the vertical and horizontal directions to form a matrix with a pitch of 450 μm.

However, as the semiconductor integrated circuits have become smaller and larger and the pitch of the pads has become narrower, it has become necessary to provide the pads at positions deviated from the matrix shape, but the pitch of the pads becomes 400 μm or less. If it becomes narrow, there is a problem that the transfer pin which applies flux to it cannot be formed depending on the cutting method.

[0010]

In a semiconductor integrated circuit, flip-chip type LSIs and VLSIs have been put into practical use due to the increase in capacity due to the miniaturization of unit elements. The pitch of solder bumps used in these Has become narrower, and it has become necessary to pattern pads at positions deviated from the matrix.

Therefore, in order to align and mount such an integrated circuit on a pad formed by patterning on a multilayer circuit board, flux is applied to the pad in advance,
Although it is necessary to improve the wettability, there is a problem that the pitch of the transfer pin row is narrow and it cannot be processed.

[0012]

SUMMARY OF THE INVENTION The above problem is that transfer pin rows for simultaneously transferring flux to a large number of pads patterned on a multilayer circuit board are installed in a transfer unit separately in two groups. This can be solved by configuring the flux transfer method, which is characterized in that the flux is attached to the tips of the transfer pins in each flux table and then moved to transfer the flux onto the pad.

[0013]

The present invention solves the problem by dividing the transfer pin array into two parts and cutting them with a sufficient margin.

The number of terminals of an integrated circuit which is currently used is enormous. For example, in the case of an LSI, 640 solder bumps having a diameter of 400 μm are arranged in a matrix at a pitch of 450 μm. Is VLSI → ULSI
As the capacity increases, the number of solder bumps increases, while the pitch decreases.

Since the pads formed on the multilayer wiring board are formed by the thin film forming technique and the photolithography technique (photolithography), it can be miniaturized, but the transfer pins that supply the flux to the pads. Since it requires mechanical strength, it needs to be made of metal.Since it requires a height of at least 400 μm or more, it is made by cutting and the tip is resin-coated with organic titanium. To improve the stampability.

Here, in the conventional cutting method, the transfer pin row in which the transfer pins are arranged in a matrix is formed by cutting in the horizontal direction and the vertical direction as described above, but the pitch is 400 If it is less than μm, cutting work becomes impossible.

Therefore, the present invention divides the copy pin row into two parts so that it can be cut. For example, an irregular pattern as shown in FIG. By dividing the pattern into regular patterns as shown in (1) and synthesizing the patterns, flux can be supplied even to fine pitch pads.

[0018]

[Example] As shown in FIG. 1, there is a pad of the first row in the horizontal direction at a pitch of 300 μm on a ceramic multilayer wiring board, and a pad of the second row at a pitch of 600 μm with an interval of 300 μm from this. There is a pad, and there is a pad of 300 μm from this, and there is a pad of the 3rd row in a staggered pattern of 600 μm, and then a pad of the 4th row with a gap of 300 μm from this and a pitch of 300 μm. Are formed.

It is impossible to make a transfer pin row by cutting the pad having such a fine shape as an integral body. Therefore, the transfer pin 1 having a height of 400 μm and a diameter of 200 μm can be easily obtained by disassembling it into a regular pattern as shown in FIGS. It was possible to make transfer pin rows 8 and 9 consisting of.

Then, as shown in FIG. 2, the transfer pin rows 8 and 9 are mounted on the transfer unit 4 on the positioning table 3 as in the prior art, and the sequential (Se
quential) Control is performed. That is, first, the positioning table 3 is moved to the position of the flux table 5 and then lowered, and the flux applied to a certain thickness with a squeegee is imprinted on the transfer pin row 8 and transferred to the transfer pin 1. Then, after the positioning table 3 is moved so that the transfer pin row 9 is right above the flux table 5, the flux is transferred to the transfer pin 1 of the transfer pin row 9 after the positioning table 3 is moved so that the transfer pin row 9 is right above the flux table 5. To do.

Next, the positioning table 3 is placed on the substrate 6 to be processed.
After moving to the position of, the transfer unit 4 is lowered,
The application is completed by transferring the flux onto the pad of the substrate 6 to be processed by the transfer pin row 8 and then transferring the flux onto the pad of the substrate 6 to be processed by the transfer pin row 9 by the same operation.

[0022]

By adopting such a method, it becomes possible to apply the flux even to a pad on which a pattern is irregularly formed with a fine pitch, and it is possible to maintain the same manufacturing efficiency as the conventional one. it can.

[Brief description of drawings]

FIG. 1 is a plan view of a transfer pin row showing a method for carrying out the present invention.

2A and 2B are sectional views showing a method for carrying out the present invention.
Is.

FIG. 3 is a plan view (A) of a conventional transfer pin row and cross-sectional views (B) and (C) showing an implementation method.

[Explanation of symbols]

 1 transfer pin 2,8,9 transfer pin row 3 positioning table 4 transfer unit 5 flux table 6 substrate to be processed

Claims (1)

[Claims] 1. A method of transferring flux onto a plurality of pads arranged and patterned on a substrate (6) to be processed, wherein transfer pin rows (8), ( 9) are installed in the transfer unit (4) separately in at least two groups, and the transfer table (3) mounted on the transfer unit (4) is moved so that transfer pins are separately transferred to the flux table (5). After attaching the flux to the tip of (1), next,
A method of transferring flux, which comprises transferring the flux onto a pad.