JPH01179425A - Mounting process of semiconductor chip - Google Patents

Abstract

PURPOSE:To augment the alignment precision enabling the high density mounting process to be performed by a method wherein the semiconductor chip side pad is formed with the shape and space thereof specified smaller than those of the substrate side pad while the central positions of those pads are shifted from each other. CONSTITUTION:The shape and space of a semiconductor chip 11 side pad 12 are formed smaller than those of a substrate 13 side pad 14. The central positions of the pads 12 and 14 are shifted from each other. Reflow is effected in the state wherein the central line 16 of the pad 12 of chip 11 abuts against the other central line 17 of the pad 14 of substrate 13 making a fine shift of d in the long direction of respective pads 12, 14. At this time, the reflow in respective bumps stops on the central positions but when the pads 12, 14 are arranged at the position slightly distant from adjacent bumps making a shift in the opposite directions, two forces repel each other. Through these procedures, the alignment precision can be augmented enabling the high density amounting process to be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for mounting semiconductor chips such as ICs.

(Prior Art) Conventionally, when connecting a semiconductor chip, such as an IC, to a substrate, there are two methods: one using a package (DIP, chip carrier, pin grid, etc.), the other using wire bonding, tape carrier, and flip bonding performed on paired chips. There is chip bonding.

Hereinafter, flip chip bonding will be explained here.

FIG. 4 is a sectional view showing a state in which a semiconductor chip is mounted by such flip-chip bonding.

In the figure, 1 is a semiconductor (S+) chip, 2a and 2b are pads of one example of this chip, 3 is a substrate, 4a and 4b are pads on the substrate 3 side, and 5a and 5b are molten solder bumps.

In this way, the conventional flip chip
bonding bands (mainly AI gold metal 2a, 2b)
A thick layer of ^U is attached to the Cr-Cu metal, and further,
Solder is formed on the hemisphere, so-called solder bumps.

On the other hand, similarly, solder bumps are formed on a part of the conductor wiring on the side of the substrate to which the chip is to be attached so that the center of the bump coincides with the position opposite to the solder bump of the chip.

Then, when the solder bumps of the chip are brought into contact with the solder bumps on the substrate side and heated and melted (reflowed), they are melted together to form molten solder bumps 5a and 5b, thereby establishing a connection. Furthermore, in reflow, the precision of positioning has further improved, and a so-called self-alignment effect has been achieved.

In this way, as shown in FIG. 4, the semiconductor chip is mounted.

(Problems to be Solved by the Invention) However, the self-alignment effect in the conventional semiconductor chip mounting described above is such that the bump positions are already determined on the figure so that the centers of both the chip and the substrate coincide. The positioning accuracy remains at the average positioning accuracy of screen printing, especially when the substrate side is formed of thick film wiring. In addition, if a fluctuation occurs during the flow, the accuracy may further deteriorate.

On the other hand, when looking at future technological developments, the pitch of the band will be 60.
When miniaturizing to ~100 μm, the current self-line accuracy of about ±50 μm is insufficient.

The present invention eliminates the above problems and utilizes the effect of Selfa Line to improve positioning accuracy without changing the conventional thick film printing method. The purpose is to provide an implementation method.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a semiconductor chip mounting method using the flip-chip method, in which the shape area of the pads on the semiconductor chip side is replaced by the shape area of the pads on the substrate side. The semiconductor chip is formed smaller, and the pads on the semiconductor chip side and the pads on the substrate side are mounted with their center positions shifted from each other.

(Function) According to the present invention, in the semiconductor chip mounting method using the flip-chip method, the solder bump pattern of Frisopti 71 is compared with the solder bump pattern of the board.
Form small and 5 to 20 μm from the center of the bump on the board.
Create a slight misalignment. The bumps on the substrate side are formed larger than the bumps on the flip chip side, and are sufficiently large in the longitudinal direction. When butting the flip chip and the board, align them along the center line in the direction that causes misalignment.

After that, when reflow is performed, the band on the chip side and the pad on the substrate side move in a direction to align their centers with each other due to the surface tension of the melted solder. However, since a slight deviation of 5 to 20 μm is set here, the mutual centers cannot match. The force due to this amount of deviation can direct the chip in a certain direction. Therefore, the chip can be fixed in any direction by creating a mutual arrangement of pads that produces forces in two directions.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing the arrangement of pads of the semiconductor chip of the present invention, and FIG. 2 is a partially cutaway sectional view showing the mounting state of the semiconductor chip of the present invention.

As shown in FIG. 2, the center line 16 of the pad 12 of the chip 11 and the center i17 of the pad 14 of the substrate 13 are butted against each other with a slight deviation Δd in the longitudinal direction of each pad.
When reflow is performed, bumps 15a are formed as shown in FIG.
, 15b are formed. In this case, the reflow state of each bump stops at the center, but if a pad is arranged at a certain distance from the adjacent bump so that the amount of deviation is in the opposite direction, the two forces will repel each other. Furthermore, when formed in the direction of attraction, they can stop at a balanced position and form a bump.

FIG. 3 is a diagram showing an example of fixing a chip in an arbitrary direction by applying a desired force to a chip on which a large number of pads are formed. The centers of the pads 218 to 21p are located at the pads (
Due to the positional deviation from the center of the chip 21 (not shown), each pad of the chip 21 is pulled in the direction of the arrow, and their combined force is generated in the lateral direction (rightward direction) of the chip 21, and at the position moved in the lateral direction. Fixed. In FIG. 3(b), the centers of the many bands 22a to 22p provided on the chip 22 are misaligned with the centers of the pads (not shown) on the substrate, and each pad of the chip 22 is moved in the direction of the arrow. As a result, each pad is centered centripetally at the center of the chip 22, and the chip 22 is balanced and fixed without movement. Figure 3 (C)
, a large number of pads 23 provided on the chip 23
The centers of a to 23p are misaligned with the centers of pads (not shown) on the substrate, so each pad of the chip 23 is pulled in the direction of the arrow, and each pad is pulled in a direction radial from the center of the chip 23. As a result, the chip 23 is balanced and fixed without movement. In Figure 3(d),
The centers of the many pads 24a to 24p provided on the chip 24 are misaligned with the centers of pads (not shown) on the substrate, so each pad on the chip 24 is pulled in the direction of the arrow.
Each group of pads 24a to 24d, pads 24e to 24h, pads 24i to 24i1, pads 24m to 24p are pulled in different directions as shown by arrows,
Due to the resultant force, the chip 24 is fixed at the position moved in the rotational direction.

In the above embodiment, the shape of the pad is rectangular, but the same effect can be obtained by using a circular or oval shape, for example.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, the shape of the pad on the substrate side can be made larger than the shape of the pad on the chip side, which contributes to miniaturization of the pattern formed on the substrate side. strict requirements can be avoided. After all, even though the pad area on the substrate side is several times larger, the alignment accuracy is exactly the same as the self-alignment effect.

In addition, during manufacturing, patterns can be formed by screen printing, and even when using normal photolithography technology, photosensitive materials with a resolution of 10 to 30 μm such as dry film can be used, reducing costs. be able to.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the arrangement of pads of a semiconductor chip of the present invention, FIG. 2 is a partially cutaway cross-sectional view showing the mounting state of the semiconductor chip of the present invention, and FIG. FIG. 4 is a partially cutaway cross-sectional view showing a state in which a conventional semiconductor chip is mounted. 11, 21.22.23.24=...chip, 12.2
1a to 2ip. 22a-22p, 23a-231), 24a-24p・
... Band of chip, 13... Board, 14... Pad of board, 15a, 15b... Bump. Patent applicant Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] In a semiconductor chip mounting method using a flip-chip method, (a) the shape area of a pad on the semiconductor chip side is formed to be smaller than the shape area of a pad on the substrate side, and (b) the shape area of the pad on the semiconductor chip side is A method for mounting a semiconductor chip, characterized in that the center positions of pads on a substrate are shifted from each other.