JPH02285652A - Semiconductor bonding device - Google Patents

Abstract

PURPOSE:To enable the bonded part between an electrode pad on a semiconductor chip and leads of a circuit substrate to be evenly ultrasonic-oscillated as well as both bonding pressure and heating temperature to be reduced sufficiently by a method wherein a bonding device is provided with a specimen stage ultrasonic oscillating the semiconductor chip in the thickness direction as well as a tape type fabric closely adhering to the specimen stage. CONSTITUTION:A bonding device collectively bonding electrode pads 12 of a semiconductor chip 13 to leads 22 of circuit substrates 21 is provided with a specimen stage 10 and tape-like fabric 11 closely adhering to the specimen stage 10. For example, as for the said tape-like fabric 11, a fabric comprising carbon fiber, polyimide base fiber, glass fiber etc. in high thermal resistance durable for repeated application in applicable temperature zone as well as high elastic limit of the fabrics themselves is applicable. A bonding tool 14 is arranged above the specimen stage 10 opposing to the semiconductor chip 13. The bonding tool 14 is fixed to a tool holder 15 reciprocated in the vertical direction by a reciprocating mechanism 16 such as a plunger, etc., while the bonding tool 14 is provided with a heater 18.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is particularly applicable to bonding surfaces of electrode pads and leads in a bonding device for collectively bonding electrode pads of a semiconductor depth and leads of a circuit board. This invention relates to a bonding device that applies vibration.

(Prior Art) FIG. 2 shows a conventional method for collectively bonding a semiconductor chip and leads of a circuit board. In the figure, 31 is a sample stage, on which a semiconductor chip 32 with an electrode pad 36 is placed, a copper foil lead 33b having a gold bump 37 at the tip, and formed on a circuit board (polyimide tape) 33a.
After aligning the electrode pads 36 on the semiconductor chip 32 with the electrode pads 36 on the semiconductor chip 32, the heated bonding tool 34 is pressed down.

Further, the sample stage 31 may be preheated by the heater 35 when necessary to protect the semiconductor chip 32 and the circuit board 33a from thermal shock and reduce variations in bonding strength.

” The conventional method described above requires high bonding pressure and heating temperature (
This has disadvantages such as thermal shock to the semiconductor chip and shortening the life of the bonding tool.

For this reason, a device for vibrating a sample stage parallel to the semiconductor chip surface is disclosed in the published patent publication (Sho 61-255031);
35 (PI3)), the tip of the lead sandwiched between the tip of the bonding tool and the electrode pad of the semiconductor chip was free and moved irregularly due to the vibration of the sample stage.
Since vibration cannot be uniformly applied to the joint between the electrode band and the lead, good bonding cannot be achieved.

In order to eliminate the above-mentioned drawbacks, the above-mentioned published patent publication (1986-
No. 244,635) discloses a device that prevents misalignment of the leads due to vibration components parallel to the semiconductor chip surface by providing a groove corresponding to the shape of the lead at the tip of a bonding tool and sandwiching the lead in the groove. ing.

However, this method has the disadvantage that the bonding tool is expensive and that the attached metal powder clogs the grooves, impeding stable bonding.

Further, in the device disclosed in the above-mentioned Japanese Patent Publication No. 63-244635, the semiconductor chip is placed directly on the sample stage, and it is difficult for the lower surface of the semiconductor chip and the upper surface of the sample stage to be in complete contact with each other. This is thought to be due to the combination of brittle silicon and hard metal, which makes it difficult for microscopic plastic flow to occur at the contact surface. For this reason, there is a drawback that the semiconductor chip is likely to shift when vibration is applied, resulting in poor positional accuracy.

(Means for Solving the Problems) The gist of the present invention is to apply vibration in the thickness direction of a semiconductor chip via a tape-like fabric on a sample stage that vibrates ultrasonically in the axial direction.

That is, the present invention provides a bonding device for collectively bonding the electrode pads of a semiconductor chip and the leads of a circuit board, which includes a sample stage that vibrates ultrasonically in the thickness direction of the semiconductor chip, a tape-like fabric that is in close contact with the sample stage, and a sample stage that vibrates ultrasonically in the thickness direction of the semiconductor chip. It is intended to provide

(Function) The lower surface of the semiconductor chip and the upper surface of the sample stage are clearly shown in FIG. 1 in which the bonding tool 15 is vibrated parallel to the surface of the chip 13 by the vibration mechanism 17 consisting of an ultrasonic vibrator. However, when changing the product type or repolishing the end face of the tool, it is troublesome to attach and detach the bonding tool 15 from the vibration mechanism 17.

Although the two patent publications mentioned above do not specify the direction of vibration in the claims, both apply vibrations parallel to the surface of the semiconductor chip, judging from the contents of the specifications. That is, the above-mentioned Jikai (Sho 61-25503
1), a leaf spring 36 is shown between the upper plate 34 and the lower plate 35, and a leaf spring 36 is shown between the upper plate 34 and the lower plate 35.
635), the direction of vibration of the vibration mechanism 17 is clearly indicated by an arrow. The reason that both of the above two methods use vibration parallel to the contact surface between the lead and the bump or the bump and the electrode band is probably because they follow the known practice of ultrasonic wire bonding.

Next, in addition to the above two examples, the micro gap between the semiconductor chip 7 and the sample stage, which is caused by the known conventional method that is not completely flat, is caused by the fiber bundle of the tape-like fabric caused by the pressing force of the bonding tool. Due to their mutual proximity, they are filled by the tape-like fabric. Here, the fiber bundles that come into contact with each other under pressure transmit vibrations through the contact points, causing the entire surface of the semiconductor chip to vibrate in the thickness direction.

Furthermore, uneven contact between the electrode pads and the leads due to the uneven height of the electrode pads on the semiconductor chip is improved by bringing the fiber bundles of the tape-like fabric closer to each other. Therefore, under the action of ultrasonic vibration, plastic flow occurs at all contact points of the lead pressed against the electrode band by the electrode pad on the semiconductor chip and the bonding tool, and the softened pad and lead form a mutual diffusion.

In the present invention, since the direction of ultrasonic vibration is the same as the thickness direction of the chip, that is, the direction of the pressing force, vibration transmission is reliable, and each lead having a different direction is parallel to the known chip surface. Compared to the case of adding vibration, ζ, Li 1
There is little variation in the vibration effect for each ′. In addition, ultrasonic vibrations having a small amplitude on the order of micrometers and a high repetition rate can supply effective vibration energy to the deformation process of the bumps, which occurs during bonding and does not exceed about 50 micrometers at most. Since the bonded part under the ultrasonic sound field is easily deformed, the bonding pressure and heating temperature can be lowered as a result.

Furthermore, since the entire surface of the semiconductor dip is securely fixed to the sample stage by the tape-like fabric, sideways sliding due to vibration is less likely to occur.

In addition, the vibration applied to the reed is a component that is less likely to cause lateral shear (), so even if the reed tip is partially free, the reed is less likely to cause lateral shear.

(Example) FIG. 1 shows a schematic diagram of an apparatus for implementing the present invention, using a fabric made of glass fiber or the like. For attachment to the sample stage 10, stretching by mechanical means is sufficient, and there is no need for stretching and gluing since vibrations are transmitted under pressure. Therefore, replacement is also easy.

Next, F-a and 17b are a pair of piezoelectric elements, which are held between the back block 1 and the sample stage 10 by a center bolt 2 with a constant tightening force.

This part constitutes a known bolted Langevin type vibrator. A pair of piezoelectric elements 17a and 17b are ultrasonic type l+
! Connected to 3.

The sample stage 10, the piezoelectric elements 17a and 17b1, the back block 1, and the center bolt 2 form a half-wavelength longitudinal vibration system, and in order to attach it to the fixed base 5, 4 is connected to the node of the longitudinal vibration system. This is a flange provided.

Next, a bonding process using the above device will be explained.

First, the semiconductor chip 13 is placed on the tape-shaped fabric 11 and preheated if necessary. It is just a schematic configuration diagram. In the figure, reference numeral 10 denotes a sample stand attached to a fixed stand 5 indicated by hatching, and a semiconductor chip 13 with electrode pads 12 formed on two sides is inserted through a tape-like fabric 11 that is in close contact with the sample stand.
rides.

A bonding tool 14 is placed above the sample stage 10 and placed on the semiconductor chip 13 . This bonding tool 14 is attached to a tool boulder 15 that moves forward and backward in the vertical direction by a forward and backward movement mechanism 16 such as a plunger. Further, the honding tool 14 is provided with a heater 18,
The tool tip 19 is heated.

Further, a lead 22 supported by a tape carrier 21 is arranged between the bonding tool 14 and the semiconductor chip 13, and a gold bump 23 is attached to the lower surface of the tip of the lead 22.

The tape-shaped fabric 11 is selected not only to have heat resistance that can withstand repeated use within the operating temperature range, but also to have a high elastic limit of the fibers themselves. For example, carbon fibers, polyimide fibers, and fibers are usually not preheated. Further, the tip 19 of the bonding tool 14 is heated by the heater 18.

Next, the leads 22 on the tape carrier 21 are aligned with the bumps 12 of the semiconductor chip 13'', and the bonding tool 14 is lowered by the advancing/retracting mechanism 16, and the leads 22 are pressed against the bumps 12 with a predetermined pressing force.

In this state, the sample stage 10 is ultrasonically vibrated in the axial direction to bond the bumps 23 and pads 12 together. The frequency of ultrasonic waves is 30 kllz to 60 kllz to make the vibration source small.
It is desirable to use kllz, and its amplitude is sufficient on the order of microns. Therefore, due to the uniform vibration load effect of the woven tape, there is almost no mechanical adverse effect on the semiconductor chip that existed in the past.

Note that the present invention is not limited to the embodiments described above. For example, the vibration imparting means is not limited to a bolted Langevin type piezoelectric vibrator, but may be a magnetostrictive type, and is not limited to a half-wave length, but may be an integral multiple thereof. Furthermore, the bumps may be provided on the electrode pad side instead of on the lead side. Various modifications can be made without departing from the gist of the claimed invention.

(Effects of the Invention) As described in detail above, as a result of the present invention, ultrasonic vibration can be uniformly applied to the joint between the electrode pad on the semiconductor chip and the lead of the circuit board. Therefore, bonding pressure and heating temperature can be kept sufficiently low, improving bonding reliability, shortening equipment start-up time, making it easier to change products, extending the life of bonding tools, and increasing the number of bins and high density. Bonding that can withstand mounting can be realized.

The improvements in bonding reliability mentioned above include improving the bonding strength of each lead and reducing variations, reducing misalignment between leads and pads, and reducing mechanical damage and thermal shock caused by local concentration of vibrations on the semiconductor chip. Or it can be resolved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a bonding device according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a conventionally known bonding device that does not use vibration. Semiconductor chip, 13, Sample stage, 10, Electrode pad, 12, Tape-shaped fabric, 11, Circuit board lead, 22

Claims (2)

[Claims] (1) In a bonding device for collectively bonding electrode pads of a semiconductor chip and leads of a circuit board, a sample stage that vibrates ultrasonically in the thickness direction of the semiconductor chip, and a tape-like fabric that closely adheres to the sample stage are used. A semiconductor bonding device characterized by: (2) The semiconductor bonding apparatus according to claim 1, wherein a bolted Langevin type vibrator with a length equivalent to a half wavelength is used as a sample stage that vibrates ultrasonically.