JPH10173005A - Method for mounting flip chip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid deviation of a bump connection part and breakage of wires until perfect sticking to a mounting board by keeping the mounting board temps. lower than the under-fill work temp. all the time until a heated under-fill resin hardens after the under-fill work ends. SOLUTION: After formation of bump connection parts 3, a printed board 1 and entire chip 5 are always kept at specified temp. An under-fill resin 6 is injected in the gap between the chip 5 and printed board 1 at fixed temp. through a small syringe, utilizing the capillary effect. Thus the resin 6 fills up and spreads the bump connection parts 3 at the lower side of the chip due to the surface tension. After injection of the under-fill resin 6, the chip 5 and printed board 1 are kept at a higher temp. than the injecting temp. of this resin 6. The resin 6 is then heated at its hardening temp. to perfectly harden it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flip chip using an underfill resin as a filler between a mounting board and a chip when mounting a chip such as an LSI on a mounting board such as a printed board via bumps. Regarding implementation method.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view of a flip chip mounting method, in which 1 is a printed board, 2 is a printed wiring, 3 is a bump connection, 4 is a pad, 5 is a chip, 7 is a bump, and 8 is a board. It is a bump.

Conventionally, flip-chip mounting using an underfill resin is performed by mounting an IC or LS on a mounting substrate such as a printed circuit board 1 as shown in a flip-chip mounting method shown in FIG.
A gold bump 7 formed by gold wire bonding on a pad 4 made of aluminum or the like formed on an I chip 5 and a board bump 8 made of solder or the like formed on a printed wiring 2 such as copper on a printed board 1 And 200 to 250
After connecting and mounting while heating to about ° C, the printed board 1 and the chip 5 are once cooled to room temperature, and then heated again to inject the underfill resin 6 between the printed board 1 and the chip 5 using a syringe or the like. I was doing underfilling work.

[0004]

However, a large integrated LS
In the case of the chip 5 of I, one piece of the chip becomes 15 mm or more, and the size of the bumps arranged on the periphery of the chip 5 is reduced to about 90 μm. As shown in FIG. The chip 5 and the printed board 1 have a coefficient of thermal expansion of 4 ppm / ° C.
When the size of the chip 5 becomes large, for example, 15 mm square, the conventional flip chip mounting temperature profile shown in FIG.
The printed circuit board 1 shrinks due to natural cooling to room temperature after chip mounting or injection of the underfill resin, and the connection between the chip 5 and the printed circuit board 1 has a temperature difference of 200 ° C.
0 μm, the bump connection 3 shown in FIG.
However, as shown in FIG. 5B, a bump having a diameter of 90 μm may be disconnected due to the material and thickness of a printed circuit board or the like.

[0005]

FIG. 2 shows a temperature profile of flip chip mounting according to the present invention. As a means for solving the problem of the present invention, as shown in FIG. 2, as an example, a time from a flip chip mounting in which a chip such as an LSI is heated and connected to a mounting board such as a printed board by bumps, to a time when an underfilling operation is started, During the underfill operation, in which the underfill resin is injected between the printed circuit board and the chip, the mounting substrate is always kept at a temperature equal to or higher than the underfill operation temperature during the time from when the underfill operation is completed to when the underfill resin is heated and cured. To manage.

[0006] Thus, from the flip chip mounting to the hardening of the underfill resin, the change in temperature is always small, and the change in the temperature of the mounting substrate such as the chip and the printed board is small, so that the change in thermal expansion is small. Thus, stress applied to the bumps can be reduced.

Therefore, no displacement of the bump connection portion occurs and no disconnection occurs until the underfill resin is completely cured and the chip and the mounting board such as a printed board are completely fixed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of one embodiment of the present invention, and is a schematic cross-sectional view of flip-chip mounting, and FIG. 2 is a temperature profile of flip-chip mounting of the present invention.

In the figure, 1 is a printed board, 2 is a printed wiring, 3 is a bump connection, 4 is a pad, 5 is a chip, and 6 is an underfill resin. FIG. 1 shows a printed circuit board 1 of an LSI chip 5 as an embodiment of the present invention.
A method of mounting a flip chip on a semiconductor device will be described.

The chip 5 is a large-scale integrated circuit chip of 15 mm square, and a large number of aluminum pads 4 are provided on the periphery of the surface of the chip, as shown in FIG. Is formed. Both the size of the pad and the interval between the pads are 100 μm. A gold bump 7 is formed thereon by ball bonding of a gold wire, and after bonding, the money is cut, so that the shape is an onion-shaped bump 7 as shown in FIG. 3C.

On the other hand, a plurality of chips 5 are mounted on the printed circuit board 1. When paying attention to one of the chips 5, the solder wiring is provided on the printed wiring 2 at a position corresponding to the bump 7 of the mounted chip 5. A substrate bump 8 made of solder or the like having a diameter of 100 μm is formed.

As shown in FIG. 3D, the connection of the LSI chip 5 to the printed circuit board 1 is performed by flipping the chip 5 upside down and aligning the bumps 7 on the chip 5 with the substrate bumps 8. The chip 5 is pressed while being heated to 230 ° C. and bonded as shown in FIG. 3 (e) or FIG. 1 (a). At this time, the gap between the chip 5 and the printed board 1, that is, the height of the bump connection portion 3 is at most about 100 μm.

After the bump connection portion 3 is formed, the temperature is conventionally 25 ° C. while the temperature reaches 90 ° C. for injecting the underfill resin 6.
In the present invention, the entire temperature of the printed circuit board 1 and the entire chip 5 is set to be constantly maintained at 120 ° C.

Then, the underfill resin 6 is heated at 90 ° C. using a small syringe (syringe) by utilizing the capillary phenomenon.
When the resin is injected into the gap of 100 μm between the chip 5 and the printed circuit board 1 at the temperature shown in FIG. 1B, as shown in FIG. Fill 3 and spread.

After the injection of the underfill resin 6, the chip 5 and the printed circuit board 1 are cooled down to 120 ° C., which is higher than the injection temperature of the underfill resin 6 of 90 ° C. Keep the temperature, then set the curing temperature of the underfill resin 6 at 150 ° C for 1-2
Heating is carried out for a time to completely solidify the underfill resin 6.

As a result, the substrate bumps 8 on the printed board 1 and the bumps 7 on the chip 5 are
Even if there is a difference in thermal expansion, the bump connection portion 3 is solidified by the underfill resin 6 without displacement, and thereafter, even at room temperature, is not disconnected due to displacement.

[0017]

As described above, a chip such as an LSI and a mounting substrate such as a printed circuit board can minimize the temperature difference from flip chip bonding to curing of the underfill resin, and as a result, a flip chip mounting portion can be formed. Since the thermal stress can be reduced to a minimum, the chip and the mounting substrate can be completely connected via the bumps without causing the mutual displacement between the chip and the mounting substrate.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of flip-chip mounting according to the present invention.

FIG. 2 shows a flip chip mounting temperature profile of the present invention.

FIG. 3 Flip chip mounting method

FIG. 4 shows a conventional example of a flip chip mounting temperature profile.

FIG. 5 is a sectional view of a conventional flip-chip mounting connection part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed board 2 Printed wiring 3 Bump connection part 4 Pad 5 Chip 6 Underfill resin 7 Bump 8 Board bump

Claims (1)

[Claims] 1. A flip-chip mounting method using an underfill resin as a filling hardening material between a chip and a mounting substrate, wherein the chip is heated and connected to the mounting substrate via bumps on the chip. Heating and injecting an underfill resin between the substrate and the mounting substrate, and keeping the chip and the mounting substrate at a temperature exceeding the injection temperature of the underfill resin until the underfill resin is cured. Flip chip mounting method.