JPH09293739A - Die bonding method and die bonding shower needle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die bonding method which can yield a highly reliable product, generating no void under a chip, and to provide the design standard of the shower needle to be used in the above-mentioned die bonding method. SOLUTION: A plurality of discharge holes are provided on the circumferential part of a die pad, at least a discharge hole 1 is provided in the center part, and two discharge holes 2 and 3 are provided adjacent to the center discharge hole. The above mentioned three places of the discharge holes are arranged in such a manner that the vertical angle of the triangular discharge holes formed by linking the three places make a right angle or an obtuse angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die-bonding method for adhering an IC chip or the like to a die pad, and more particularly to a method for applying an adhesive agent to the die pad, and more particularly to disposing a needle for ejecting an adhesive agent used for the application.

[0002]

2. Description of the Related Art Conventionally, when an IC chip or the like is die-bonded to a die pad of a lead frame with silver paste, a needle for ejecting paste is widely used to apply the silver paste to the die pad. Further, when the chip size is large and exceeds about 3.5 mm square, a needle composite body called a shower needle equipped with a plurality of ejection needles is often used.

FIGS. 4 (a) and 4 (b) show examples of the needle arrangement of conventionally used shower needles. In the same drawing, the arrangement of the needles is shown as the arrangement of the discharge points 9 (shown in the cross section of the needle) of the silver paste discharged onto the die pad 4.

The needles may be arranged in a matrix shape as shown in FIG. 1A or a honeycomb shape in which the central portion is filled as shown in FIG. In addition, it is possible to make a variety of discharge shapes with a single needle without using a shower needle, but since a large discharge time is required and work efficiency decreases, it is hardly used when the chip size is large. .

[0005]

In the case of the needle arrangement as described above, I changes with a slight fluctuation of the discharged silver paste.
A cavity may be formed under the C chip. FIG. 5 is an X-ray photograph of a die-bonded IC chip coated with a silver paste on a die island of a lead frame using a conventional shower needle. The portion shown in FIG. 8 is a hollow portion formed under the IC chip.

In a product having such a cavity, the IC chip may be broken when it is mounted on a circuit board or the like. FIG. 8 is a schematic view of a chip crack caused by a cavity under the chip.

From the reliability test of the product device, it has been confirmed that the destruction of the IC chip in such a case occurs under the following conditions.

That is, when the product is manufactured with the cavity as described above, when it is mounted on a printed board by soldering, for example, it is exposed to high heat of about 260 ° C. Air usually contains water, and particularly when the IC chips are absorbing moisture, the water contained therein increases the water vapor pressure due to the high heat. Therefore, in the worst case, a crack as shown in FIG. 8 is generated and the IC chip is destroyed.

Further, the cavity as described above is shown in FIG.
As shown in FIGS. 7A and 7A, it has been found that this is likely to occur when the silver paste is discharged onto each vertex of a square or an equilateral triangle. This is because when a silver paste is discharged onto a die pad, an IC chip is placed on it, and pressure is applied, the paste is pressed and pushed out to the periphery of the die pad, but when the above-mentioned arrangement of the discharge location includes air. This is because the cavity is likely to be left in the center. 6 (b) and 7 (b)
Shows an example of the degree of wetting of the paste by such a discharge paste.

The present invention is intended to solve the above problems and provide a die-bonding method and a design standard of a shower needle used for the die-bonding method capable of obtaining a highly reliable product without forming a cavity under a chip. .

[0011]

In order to solve the above problems, the die bonding method of the present invention is a die bonding method for an IC chip or the like, which is performed by discharging an adhesive such as silver paste onto a plurality of locations on a die pad using a needle. In the method, a plurality of ejection points are provided in the peripheral portion of the die pad, and at least one ejection point, ejection point 1, is provided in the central portion, and the ejection point 1 and a peripheral portion adjacent to the ejection point and adjacent to each other are provided. Regarding the positional relationship between the three discharge points, the discharge points 2 and 3, the vertex angle θ at the discharge point 1 of the triangle formed by connecting the three points is arranged to be a right angle or an obtuse angle. It was done like this.

Further, the shower needle of the present invention has the needle arranged on the discharge surface thereof as follows, corresponding to the die bonding method. That is, a plurality of needles are provided on the discharge surface / peripheral part, at least one needle and a needle 1 are provided in the central part, and two needles, needles 2 and 3 in the peripheral part, which are adjacent to and adjacent to each other, are provided. With respect to the positional relationship with, the vertical angle θ of the triangular needle 1 formed by connecting the positions of these three needles was arranged to be a right angle or an obtuse angle.

In the above shower needle, the inner diameter of the central needle is larger than that of the peripheral needle.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are conceptual diagrams for explaining the effect of the location of the adhesive ejection location in the die bonding method of the present invention, and FIG. 3 shows an example of the location of the ejection location. In FIGS. 1 (a) and 2 (a), 1 is the discharge points 1, 2 and 3 provided in the center, and 2 is the discharge points 2 and 3 that are adjacent to the discharge point 1 and along the periphery of the die pad. Show.

A side of the triangle connecting the three points 1, 2, and 3 connecting the points 2 and 3 is indicated by A, and an angle of the vertical angle (vertical angle at the discharge point 1) is indicated by θ. In the present invention, the value of the angle θ is set to be a right angle or an obtuse angle as illustrated.

When the silver paste is discharged onto the above-mentioned location on the die pad, the IC chip is placed on the silver paste, and pressure is applied, the flow of the silver paste is as follows. That is, the ejected silver paste is extruded from each ejection portion toward the periphery by pressure and spreads on the die pad, but finally the portion of the relatively wide side A is wetted, and at the same time, the air is expelled from that portion. As a result, the wetness of the paste is as shown in FIGS. 1 (b) and 2 (b), and the air sealing as shown in FIGS. 6 (b) and 7 (b) is performed. It never happens.

As can be easily imagined, the larger the angle θ, the better the ejection of air from the side A. Further, by making the discharge amount of the discharge portion of the central portion 1 larger than that of the discharge portions 2 and 3 of the peripheral portion, the spread of the paste from the chip central portion becomes better,
The effect of the above arrangement is further enhanced.

The embodiment shown in FIGS. 3A to 3C shows an example in which the discharge amount in the central portion is larger than that in the peripheral portion as described above. Discharge of the arrangement as described above, the arrangement of the needle of the shower needle to be used,
This can be easily realized by providing the arrangement corresponding to the above-mentioned ejection point.

Further, making the discharge amount in the central portion larger than the discharge amount in the peripheral portion as described above can be easily realized by making the inner diameter of the needle in the central portion larger than the inner diameter of the needle in the peripheral portion.

Since the wetting and spreading of the adhesive largely depends on the viscosity of the adhesive as well as the discharge amount, it is important to set the conditions for the implementation. An example is shown below.

For example, chip size 5 × 5 mm, thickness 2
A 60 μm IC chip is coated with silver paste (finished thickness 24
In the case of die-bonding with (μm), the silver paste is discharged using a shower needle with five needles arranged at the position shown in FIG. The inner diameter of each of the five needles is as follows: center needle: 20G (0.52mm), peripheral needle: 2
1G (0.49mm), silver paste has a viscosity of 250
0 cB (centiboise) is used. In this case, the discharge pressure of the paste dispenser is 0.3-1kg / cm2
And

By discharging the silver paste with the above settings, it is possible to perform a good die bond without forming a cavity under the chip.

[0023]

As described above, in the die-bonding method of the present invention, the locations of the ejection points of the adhesive are set in accordance with the above-mentioned three points with respect to the positional relationship between the ejection points of the peripheral portion and the central portion which are adjacent to each other on the die pad. Are arranged so that the apex angle θ at the discharge point 1 of the triangle formed by connecting the two is a right angle or an obtuse angle. Therefore, when the adhesive paste spreads on the die pad due to pressure, it is better to expel the air and It is possible to manufacture a highly reliable product that does not cause a cavity in the product.

Further, in the shower needle of the present invention, the arrangement of the needles provided on the discharge surface thereof is the same as the arrangement in the die bonding method, so that the die bonding method can be easily realized.

Further, by making the inner diameter of the above-mentioned shower needle / center needle larger than the inner diameter of the peripheral needle, a more effective shower needle can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram for explaining an adhesive discharging portion in a die bonding method of the present invention.

FIG. 2 is a conceptual diagram for explaining another example of an adhesive discharge location in the die bonding method of the present invention.

FIG. 3 is an example of an adhesive discharge location in the die bonding method of the present invention.

FIG. 4 is an example diagram of a needle arrangement of a conventional shower needle.

FIG. 5 is an X-ray photograph showing a cavity under an IC chip produced by a conventional die bonding method.

FIG. 6 is an explanatory diagram of cavity generation due to discharge of adhesive at a plurality of locations.

FIG. 7 is an explanatory diagram of another example of the generation of cavities due to discharge of adhesive at a plurality of locations.

FIG. 8 is a schematic view of a chip crack generated due to a cavity under the chip.

[Explanation of symbols]

 1: Discharge point 1 2: Discharge point 2 3: Discharge point 3 4: Die pad 5: Lead frame 6: IC chip 7: Adhesive 8: Cavity 9: Discharge point (conventional example) θ: Vertical angle.

Claims (3)

[Claims] 1. In a die-bonding method for an IC chip or the like, which is performed by discharging an adhesive such as a silver paste onto a plurality of locations on a die pad using a needle, the locations where the adhesive is discharged are arranged at a plurality of locations around the die pad. At least one discharge location and a discharge location 1 are provided in the central portion while providing a discharge location, and the discharge location 1 and two discharge locations, a discharge location 2 and a discharge location 2, 3 in the peripheral portion adjacent to the location and adjacent to each other. The die-bonding method is carried out by arranging so that the apex angle θ at the discharge point 1 of the triangle formed by connecting the three points is a right angle or an obtuse angle. . 2. A shower needle for die bonding comprising a plurality of needles, wherein the needles are arranged such that a plurality of needles are provided on a discharge surface / peripheral portion and at least one needle and a needle 1 are provided at a central portion, Regarding the positional relationship between the two needles in the peripheral portion adjacent to the needle and adjacent to each other, the needles 2 and 3,
A shower needle for die bonding, wherein the triangular needle 1 formed by connecting the positions of these three needles is arranged so that the apex angle θ is a right angle or an obtuse angle. 3. The shower needle for die bonding according to claim 2, wherein the inner diameter of the central needle and the needle 1 is larger than the inner diameter of the peripheral needle.