JP2000243865A - Conductive ball reinforcing resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide conductive ball reinforcing resin material where a specified amount of reinforcing resin can be uniformly and easily spread on a conductive ball arrangement surface of a semiconductor package using conductive balls as terminals for external connection, volatile component is not generated when thermal contact-bonding is performed and reinforcement of the conductive balls is possible in a short time. SOLUTION: Conductive ball reinforcing resin 5 composed of adhesive resin is spread on a single surface of an auxiliary sheet 6, apertures 7 in which conductive balls 2 are to be inserted are formed at positions of a semiconductor package 1 to be thermally contact-bonded which positions correspond to the conductive balls 2. The adhesive resin whose elastic modulus at a thermal contact-bonding temperature is at most 1×107 Pa is used as the reinforcing resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin sheet for reinforcing conductive balls in a semiconductor package having conductive balls as terminals for external connection.

[0002]

2. Description of the Related Art In recent years, with the demand for higher functionality and lighter, thinner and smaller electronic devices, high-density integration and high-density mounting of electronic components have been advanced. Semiconductor packages used in these electronic devices have become smaller and have more pins.

[0003] With the miniaturization of semiconductor packages,
In a conventional package using a lead frame, there is a limit to miniaturization. Therefore, recently, a BGA (Ball Gr.
id Array) and CSP (Chip Scale)
A new packaging method of area mounting type, such as "Package", has been proposed. In these semiconductor packages, solder balls and resin core conductive balls are used as external connection terminals. In such a semiconductor package, since the semiconductor chip occupies most of the inside of the package, the linear expansion coefficient is close to 4 ppm which is the linear expansion coefficient of silicon.

On the other hand, the substrate on which such a semiconductor package is mounted generally has a linear expansion coefficient of 10 to 20 ppm. Therefore, when the semiconductor package is mounted on the substrate and undergoes a temperature change, the difference in the coefficient of linear expansion results. It is known that a large strain stress is applied to the conductive ball, which is the connection portion, and cracks occur at the connection interface between the semiconductor package and the substrate of the conductive ball during repeated temperature changes, which eventually breaks. ing.

[0005] As a method of reducing such a problem,
A method to significantly improve the connection reliability of the semiconductor package when mounted on the board by applying resin near the interface between the conductive balls and the semiconductor package and reducing the strain stress when the temperature changes while mounted on the board. It has been known.
(Nikkei Micro Devices, February 1998 issue) However, in this reinforcing method, as shown in FIG.
Is applied directly to the periphery of the conductive ball 2 using a dispenser 3 or the like, adhered to the base of the conductive ball by the surface tension of the resin, and then dried. It is difficult to apply a certain amount of resin stably, and it takes a long time to dry, and the surface of the conductive ball is contaminated by volatile components generated during drying.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem of a method of reinforcing a conductive ball with a liquid reinforcing resin. It is an object of the present invention to provide a conductive ball reinforcing resin material which can easily and uniformly apply the reinforcing resin of the above, does not generate volatile components at the time of thermocompression bonding, and can shorten the conductive ball in a short time. is there.

[0007]

That is, the present invention relates to a conductive ball reinforcing resin which is used by heating and pressing on a conductive ball arrangement surface of a semiconductor package having conductive balls as external connection terminals. A conductive ball reinforcing resin made of an adhesive resin is applied to one side of the auxiliary sheet, and an opening for receiving the conductive ball is formed at a position corresponding to the conductive ball of the semiconductor package to be heated and pressed. The elastic modulus of the conductive ball reinforcing resin at the thermocompression bonding temperature is 1
It is a conductive ball reinforcing resin sheet of not more than × 10 ⁷ Pa. The reinforcing resin is formed in a sheet shape in advance, and the sheet is adhered to the conductive ball surface of the semiconductor package by heating and pressure bonding. Is achieved.

[0008] The conductive ball reinforcing resin sheet of the present invention comprises:
As shown in FIG. 2A, a resin having an adhesive property is applied to one surface of an auxiliary sheet 6 made of a resin film or a metal foil to form a film, and the conductive ball reinforcing resin layer 5 is formed and heated. This is obtained by forming an opening 7 for receiving the conductive ball 2 at a position corresponding to the conductive ball 2 of the semiconductor package 1 to be crimped. Then, as shown in FIG. 2B, the opening 7 formed in the sheet is aligned with the conductive balls 2 on the conductive ball arrangement surface of the semiconductor package 1, and a resin surface having an adhesive property (conductive The conductive ball reinforcing resin layer 5) is used by being thermocompression bonded to the semiconductor package 1.

At this time, the thermocompression bonding is performed at a temperature at which the adhesive resin melts and softens. By using an adhesive resin having an elastic modulus of 1 × 10 ⁷ Pa or less at this temperature, the resin softens and flows at the time of thermocompression bonding.
As shown in FIG. 2 (c), at the same time as seeping out into the opening 7 corresponding to the conductive ball 2, the conductive ball 2 spreads and adheres to the periphery of the base of the conductive ball 2 in the opening 7. If the elastic modulus is higher than 1 × 10 ⁷ Pa, the softening during heating and pressing is not sufficient, and the adhesive resin does not spread sufficiently around the conductive balls, so that sufficient adhesion cannot be achieved.

The openings previously formed in the conductive ball reinforcing resin sheet of the present invention may be formed so that one conductive ball enters one opening, and the opening into which a plurality of conductive balls enter. Department. As a method of forming the opening, a method of chemically etching can be used in addition to a method using a drill, a punch, an excimer laser or a UV laser.

As the auxiliary sheet, a resin film or a metal foil can be used. When a resin film is used, a resin film sheet such as polyimide, polyester, or polypropylene can be used.However, when a polyimide film is used, a conductive ball-reinforced resin sheet having excellent heat resistance and dimensional stability can be obtained. . When a metal foil is used, a copper foil, an aluminum foil, or the like can be used. If copper foil is used, it is possible to easily and accurately provide an opening at the position corresponding to the conductive ball of the copper foil by etching, and through this opening, the opening is formed in the adhesive resin by laser. Since it can be performed, it can be applied to a semiconductor package in which fine conductive balls are arranged, and is suitable as an auxiliary sheet of the conductive ball reinforcing resin sheet of the present invention.

As the conductive ball reinforcing resin, a resin having an adhesive property and having an elastic modulus of 1 × 10 ⁷ Pa or less at a heating and pressing temperature can be widely used. A mixture of a plastic silicone-modified polyimide and an epoxy resin, a one-part thermosetting epoxy resin, or the like is particularly preferably used.

[0013] The thermoplastic silicone-modified polyimide has a low water absorption and a low glass transition temperature, so that it can be thermocompression bonded to a semiconductor package at a low temperature. Becomes possible. The thermocompression bonding can be performed at a temperature higher than the glass transition temperature of the resin within a few seconds, and the productivity is excellent. Furthermore, by mixing epoxy resin with this thermoplastic silicone-modified polyimide, it is possible to improve moisture resistance reliability while maintaining low moisture absorption and excellent productivity, and it is suitable as a conductive ball reinforcing resin for semiconductor packages. It is something. In addition, one-part thermosetting epoxy resin has a property that the resin elastic modulus is greatly reduced at a low heat-pressing temperature, and can easily flow during heat-pressing and can be uniformly supplied around the conductive ball. There are features.

As a method of applying the adhesive reinforcing resin to the auxiliary sheet, a doctor blade, a bar coater, a comma coater, a die coater, a curtain coater, a spin coater, a spray coating, a transfer coating and the like can be used. The applied resin is dried by a hot air drier or a far-infrared drier to form a film.

[0015] The conductive ball reinforcing resin sheet of the present invention comprises:
After heat-pressing on the conductive ball array surface of the semiconductor package, the auxiliary sheet 6 may be used as a part of the semiconductor package as shown in FIG. 2C, or as shown in FIG. After the thermocompression bonding to the semiconductor package 1, the auxiliary sheet 6 can be peeled off, and only the adhesive reinforcing resin layer 5 can be adhered to the semiconductor package.

[0016]

Example 1 A 50 μm thick polyimide film (manufactured by Toray DuPont, Kapton) was coated on one surface with a glass transition temperature of 145 ° C. and an elastic modulus of 9 × 1 at 250 ° C.
0 ⁶ Pa silicone modified polyimide resin, thickness 20μ
m, a conductive ball-reinforced resin sheet was prepared. A CSP type semiconductor package having 208 solder balls having a diameter of 0.3 mm as external connection terminals is prepared, and a hole having a diameter of 0.4 mm is drilled into the conductive ball reinforcing resin sheet according to the position of the solder balls. The part was processed. The semiconductor package and the conductive ball reinforcing resin sheet are aligned with the solder ball and the opening, and the temperature is set to 250
Thermocompression bonding was performed at a temperature of 10 ° C. and a pressure of 10 kgf / cm ² for 5 seconds. The silicone-modified polyimide resin softened and flowed into the opening, spread and adhered to the root of the solder ball. The CSP type semiconductor package with the reinforcing resin sheet was mounted on the circuit of the FR-5 substrate while being positioned and connected by reflow processing. The substrate was subjected to a temperature cycle test at −25 ° C./125° C., and the terminal conduction of the semiconductor package was examined. As a result, the conduction was maintained after 2000 cycles.

Example 2 A glass transition temperature of 145 ° C. was applied to the roughened surface of a 35 μm-thick copper foil (manufactured by Nihon Denshi, rolled foil).
Thus, a conductive ball reinforcing resin sheet was prepared by applying a silicone-modified polyimide resin having an elastic modulus at 250 ° C. of 9 × 10 ⁶ Pa to a thickness of 20 μm. 0.3m diameter
Prepare a CSP type semiconductor package having 208 solder balls of m as external connection terminals, and adjust the position of the solder balls to the copper foil of the conductive ball reinforcing resin sheet.
An opening having a diameter of 0.4 mm was formed by etching, and through this opening, an opening was formed in the silicone-modified polyimide layer with an excimer laser. The semiconductor package and the conductive ball reinforcing resin sheet were heat-pressed at a temperature of 250 ° C. and a pressure of 10 kgf / cm ² for 5 seconds with the solder balls aligned with the openings. The silicone-modified polyimide resin softened and flowed into the opening, spread and adhered to the root of the solder ball. The CSP type semiconductor package with the reinforcing resin sheet was mounted on the circuit of the FR-5 substrate while being positioned and connected by reflow processing. Keep this substrate at -25 ° C
As a result of conducting a temperature cycle test at / 125 ° C. and examining terminal conduction of the semiconductor package, conduction was maintained after 1500 cycles.

Example 3 A 50 μm thick polyimide film (manufactured by Toray DuPont, Kapton) was coated on one side with a glass transition temperature of 125 ° C. and an elastic modulus of 3 × at 250 ° C.
10 ⁶ Pa one-pack type epoxy resin was prepared conductive balls reinforced resin sheet formed by coating to a thickness 10 [mu] m. C with 60 solder balls of 0.3 mm diameter as external connection terminals
An SP type semiconductor package is prepared, and in accordance with the position of the solder ball, the above conductive ball reinforcing resin sheet is
An opening having a diameter of 0.4 mm was machined by a drill. The semiconductor package and the conductive ball reinforcing resin sheet are aligned with the solder ball and the opening, and the temperature is 100 ° C. and the pressure is 5 kg.
Thermocompression bonding was performed at f / cm ² for 3 seconds. One-part epoxy resin is
It softened and flowed into the opening, spread and adhered to the root of the solder ball. The CSP type semiconductor package with the reinforcing resin sheet was mounted on the circuit of the FR-5 substrate while being positioned and connected by reflow processing. This substrate is -25
As a result of conducting a temperature cycle test at ° C./125° C. and examining terminal conduction of the semiconductor package, conduction was maintained after 1500 cycles.

Example 4 A 75 μm thick polyimide film (upilex S, manufactured by Ube Industries, Ltd.) was coated on one side with a thermoplastic silicone having a glass transition temperature of 150 ° C. and an elastic modulus of 8 × 10 ⁶ Pa at 250 ° C. A conductive ball reinforcing resin sheet was prepared by applying a mixed resin of modified polyimide and epoxy resin to a thickness of 20 μm. Diameter 0.
A CSP type semiconductor package having 60 3 mm solder balls as external connection terminals was prepared, and the conductive ball reinforcing sheet was processed to have a 0.4 mm diameter opening by a UV laser in accordance with the position of the solder balls. . The semiconductor package and the conductive ball reinforcing resin sheet are aligned with the solder balls and the openings, and the temperature is set to 250 ° C. and the pressure is set to 10 kgf / cm ^2.
For 10 seconds. The conductive ball reinforcing resin softened and flowed into the opening, spread and adhered to the root of the solder ball. Next, the Iupirex S film as an auxiliary sheet was peeled off such that the conductive ball reinforcing resin remained on the semiconductor package side. The CSP type semiconductor package with the conductive ball reinforcing resin was mounted on the circuit of the FR-5 substrate while being positioned, and connected by reflow processing. This substrate was subjected to a temperature cycle test at −25 ° C./125° C., and the terminal conduction of the semiconductor package was examined. As a result, conduction was maintained after 2500 cycles.

Example 5 A polyimide film (Kapton, manufactured by Toray DuPont) having a thickness of 50 μm was coated on one surface with a glass transition temperature of 145 ° C. and an elastic modulus of 9 × at 250 ° C.
10 ⁶ Pa thermoplastic silicone modified polyimide resin is
A conductive ball reinforcing resin sheet coated to a thickness of 20 μm was prepared. Prepare a CSP type semiconductor package having 60 solder balls with a diameter of 0.3 mm as external connection terminals.
The conductive ball reinforcing resin sheet is drilled with a width of 0.4 mm and a length of 11.5 in accordance with the position of the solder ball.
A rectangular slit-shaped opening of mm was machined. The semiconductor package and the conductive ball reinforcing resin sheet are positioned at a temperature of 25 by aligning the solder balls with the slit-shaped openings.
Thermocompression bonding was performed at 0 ° C. and a pressure of 20 kgf / cm ² for 10 seconds. The thermoplastic silicone modified polyimide resin softened and flowed into the slit-shaped opening, spread to the roots of a plurality of solder balls existing inside the opening, and adhered simultaneously. The CSP type semiconductor package with the reinforcing resin sheet was mounted on the circuit of the FR-5 substrate while being positioned and connected by reflow processing. This substrate is -25 ° C / 125 ° C
As a result of conducting a temperature cycle test on the semiconductor package and examining the terminal conduction of the semiconductor package, conduction was maintained after 1500 cycles.

[0021]

According to the conductive ball reinforcing resin sheet of the present invention, the reinforcing resin sheet previously formed into a film is heated and pressure-bonded, so that the reinforcing resin can be precisely and uniformly applied to the periphery of the conductive ball in a short time. It is possible to supply a conductive ball reinforcing resin which can be adhered and which is excellent in productivity and precision.

[Brief description of the drawings]

FIG. 1 is a view showing a conventional method of applying a conductive ball reinforcing resin.

FIG. 2 shows the configuration of a conductive ball-reinforced resin sheet of the present invention;
FIG. 3 is a diagram showing an example of a method of using the same.

FIG. 3 is a view showing another example of a method of using the conductive ball reinforcing resin sheet of the present invention.

[Explanation of symbols]

 1: semiconductor package 2: conductive ball 3: dispenser 4: liquid reinforcing resin 5: conductive ball reinforcing resin layer 6: auxiliary sheet 7: opening

Claims (8)

[Claims] 1. A conductive ball reinforcing resin which is used by heating and pressing on a conductive ball arrangement surface of a semiconductor package having conductive balls as terminals for external connection. A conductive ball reinforcing resin is applied, and an opening for receiving the conductive ball is formed at a position corresponding to the conductive ball of the semiconductor package to be thermocompression-bonded. A conductive ball-reinforced resin sheet, wherein the elastic modulus of the conductive ball is 1 × 10 ⁷ Pa or less. 2. The conductive ball reinforcing resin sheet according to claim 1, wherein the auxiliary sheet is a polyimide film. 3. The conductive ball reinforcing resin sheet according to claim 1, wherein the auxiliary sheet is a copper foil. 4. The conductive ball reinforcing resin sheet according to claim 1, wherein the adhesive resin is a thermoplastic silicone-modified polyimide. 5. The conductive ball reinforcing resin sheet according to claim 1, wherein the adhesive resin is a mixture of a thermoplastic silicone-modified polyimide and an epoxy resin. 6. The conductive ball reinforcing resin sheet according to claim 1, wherein the adhesive resin is a one-part thermosetting epoxy resin. 7. The conductive ball reinforcing resin sheet according to claim 1, wherein the auxiliary sheet can be peeled off and removed after heat-press bonding to the semiconductor package. 8. The conductive ball reinforcing resin sheet according to claim 1, wherein an opening portion through which a plurality of conductive balls on the surface of the semiconductor package can enter at the same time is formed.