JP2002118148A - Method of mounting semiconductor chip to printed circuit board, and mounting sheet used for embodying the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel semiconductor chip mounting method which can avoid a problem such as an improper connection between bump electrodes of a printed circuit board and terminals of semiconductor chips in a simple step and at low cost, and also to provide a mounting sheet used for embodying the method. SOLUTION: A sheet 2 for mounting of semiconductor chips having a thermosetting resin layer 2-1 of nearly the same thickness as the height of bump electrodes 1-2 of a printed circuit board 1 is manufactured on one surface of a synthetic resin film 2-2, the sheet is compression bonded against a surface of the board 1 provided with the bump electrodes 1-2, the film is peeled off therefrom, the bump electrodes 1-2 are bonded to terminals 3-2 on the chips 3 so that the electrodes are positioned as to correctly face the terminals 3-2 and as contacted therewith, the resin layer 2-1 is heated and cured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a semiconductor chip on a printed wiring board and a semiconductor chip mounting sheet used for carrying out the method.

[0002]

2. Description of the Related Art Conventionally, when a multi-pin LSI package used for an MPU, a gate array, or the like is mounted on a printed wiring board, bump electrodes made of eutectic solder, high-temperature solder, gold, or the like are provided on connection pads of a semiconductor chip. And a flip-chip mounting method in which the bump electrodes are brought into contact with the corresponding terminal portions on the printed wiring board by a so-called face-down method, and are fused / diffusion-bonded. However, according to this method, when the semiconductor chip and the printed wiring board are subjected to periodic fluctuations in temperature, the junction may be broken due to a difference in thermal expansion coefficient between the semiconductor chip and the printed wiring board. Liquid thermosetting resin (underfill material) is injected into the gap between the entire surface on which the bump electrodes are provided and the opposing printed wiring board and cured, and the entire bump joint is joined to the printed wiring board. There has been proposed a method of dispersing thermal stress concentrated on a bump electrode to prevent breakage. However, the gap between the semiconductor chip and the printed wiring board in flip-chip mounting is as small as 40 to 200 μm, so that the step of impregnating the underfill material without voids takes a considerable amount of time, and the lot of the underfill material between lots. There is a problem that the viscosity management is complicated.

As a solution to this problem, a technique of sandwiching a sheet-like thermosetting resin or thermoplastic resin between a semiconductor chip and a printed wiring board and thermocompression bonding is disclosed in, for example, Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open Nos. 213741 and 10-242208 and 10-270497. However, the technique disclosed in Japanese Patent Application Laid-Open No. 9-213741 requires a step of separately providing a sealing portion so as to surround the bump portion with a sealing material, which makes the process complicated and completely avoids the generation of voids. There is a problem that can not be. or,
In the proposal of Japanese Patent Application Laid-Open No. H10-242208, it is necessary to position the underfill resin, and it is unavoidable that the amount of the underfill resin may be excessive or deficient depending on the location, or that voids may occur due to relief holes. Further, in JP-A-10-270497, since the bump electrode of the semiconductor chip is cut into the insulating adhesive film and connected to the terminal portion of the printed wiring board, the coating of the insulating adhesive film remains at the tip of the bump electrode. However, there is a problem in terms of process and reliability, for example, the connection reliability may be impaired.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a simple and inexpensive process for bumping a printed wiring board. An object of the present invention is to provide a novel semiconductor chip mounting method in which an electrode and a terminal of a semiconductor chip are securely connected and no problem such as poor connection occurs, and a mounting sheet used for implementing the method.

[0005]

The first object of the present invention is to provide the following steps [a] to [e], ie, [a] forming a bump electrode of a printed wiring board on one surface of a synthetic resin film. Manufacturing a semiconductor chip mounting sheet provided with a thermosetting resin layer having a thickness T substantially equal to the height H of the semiconductor device; and [b] mounting the semiconductor on the surface of the printed wiring board on which the bump electrodes are provided. Pressing the thermosetting resin layer of the chip mounting sheet; [c] peeling off the synthetic resin film of the semiconductor chip mounting sheet pressed on the bump electrode surface of the printed wiring board; [d] printing wiring board Positioning the bump electrodes of the printed circuit board so that the bump electrodes of the printed circuit board correctly face and contact the corresponding terminals on the semiconductor chip; and That together joined to the terminal, characterized by comprising the steps of heating and curing the thermosetting resin, and is achieved by a method for mounting a semiconductor chip on a printed wiring board. Here, the thickness T of the thermosetting resin layer
Is about the same as the height H of the bump electrode of the printed wiring board to be mounted, specifically, (HT)
Is within ± 30 μm, preferably within ± 15 μm. The allowable limit of the deviation (HT) actually depends on the shape, dimensions, distribution density, arrangement, viscosity of the thermosetting resin and the like of the bump electrode, and is difficult to specify. The objective can be achieved for all the semiconductor chips.

A second object of the present invention is to provide, on one surface of a synthetic resin film, a height H of a bump electrode of a printed wiring board.
A semiconductor chip mounting sheet used for carrying out a method for mounting a semiconductor chip on a printed wiring board according to claim 1, characterized in that it is provided with a thermosetting resin layer having the same thickness T as that of the semiconductor chip mounting sheet. Is done. It is desirable that the synthetic resin film used at this time has a glass transition temperature lower than the curing temperature of the thermosetting resin laminated thereon. As the thermosetting resin, an epoxy resin composition having a curing temperature lower than the joining temperature between the bump electrode of the printed wiring board and the terminal of the semiconductor chip is recommended. Still further, the epoxy resin composition is 50% by weight.
It is desirable to include the above-mentioned inorganic filler.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The drawings are explanatory views showing the configuration of the method of the present invention, but in order to make the description easier to understand, these drawings show bump electrodes and a mounting sheet in an exaggerated manner. FIG. 1 is a partially enlarged sectional view showing a portion related to the present invention in the configuration of a printed wiring board, FIG. 2 is an enlarged sectional view of a semiconductor chip mounting sheet, and FIG. FIG. 4 is a partially enlarged cross-sectional view showing a state in which a semiconductor chip mounting sheet is bonded on a face surface, and FIG. 4 is a partially enlarged cross-sectional view showing a state in which the synthetic resin film of the bonded semiconductor chip mounting sheet is completely peeled off. FIG. 5 and FIG. 5 are partially enlarged sectional views showing a state where a semiconductor chip is mounted on the printed wiring board shown in FIG.

In these figures, 1 is a printed wiring board, 1-1 is its board, 1-2 is a bump electrode,
The bump electrodes are formed by plating with solder, nickel, gold, etc., conductive paste printing using silver paste or gold paste, gold wire ball bonding, solder precoating, solder paste printing reflow, solder ball reflow. And the like. Reference numeral 2 denotes a semiconductor chip mounting sheet (hereinafter, simply referred to as “mounting sheet”) formed by forming a thermosetting resin layer 2-1 on one surface of a synthetic resin film 2-2, and 3 denotes a semiconductor chip. And a terminal 3-2 corresponding to the bump electrode 1-2 of the printed wiring board 1 is provided on the chip wiring surface 3-1.

When mounting the semiconductor chip 3 on the printed wiring board 1 by the method of the present invention, first,
As described in the step (a), the synthetic resin film 2
-2, a semiconductor chip mounting sheet 2 having the thermosetting resin layer 2-1 formed on one surface is manufactured. In this case, the thickness T of the thermosetting resin layer 2-1 is such that when the mounting sheet 2 is attached to the printed wiring board 1, the bump electrodes 1-2 are formed.
Is penetrated through the thermosetting resin layer 2-1 and comes into contact with the synthetic resin film 2-2, and an appropriate amount of the thermosetting resin protrudes around the periphery of the bonding area, leaving no void on the bonding surface. It is determined as follows. Strictly speaking, the upper limit and the lower limit of the thickness T of the thermosetting resin layer 2-1 are the size, shape, number, total volume and distribution state of the bump electrodes 1-2 formed on the printed wiring board 1, as well as heat. Although determined by the hardness of the curable resin layer or the like, the above condition can be satisfied for a generally used printed wiring board by making the height H substantially equal to the height H of the bump electrode 1-2. .

In a mass production plant, the thickness T of the thermosetting resin layer 2-1 is always completely set to the height H of the bump electrode 1-2.
It is difficult to keep the same value as However, if the thickness T of the thermosetting resin layer 2-1 is within ± 30 μm of the height H of the bump electrode 1-2, good results can be obtained for almost all the printed wiring boards 1. There was found. A more desirable value of the thickness T of the thermosetting resin layer 2-1 is within a height H ± 15 μm of the bump electrode 1-2.
When the thickness T of the thermosetting resin layer is within this range, the mounting sheet 2 can be easily pressed, and the tip of the bump electrode can be brought into contact with the synthetic resin film 2-2 with an appropriate pressing force. In addition, no void remains on the sticking surface, and an appropriate amount of the thermosetting resin that protrudes to the periphery of the sticking region also remains.

When the thickness T of the thermosetting resin layer exceeds the height H of the bump electrode + 30 μm, when the mounting sheet 2 is pressed against the printed wiring board, the bump electrode does not penetrate the thermosetting resin layer, and There is a possibility that the connection with the terminal of the chip may be insufficient, and the amount of the thermosetting resin protruding to the peripheral edge of the sticking area becomes excessive, which causes inconvenience. Conversely, its thickness T
However, if the thickness is less than or equal to 30 μm, the gap between the semiconductor chip and the printed wiring board cannot be sufficiently filled with the thermosetting resin, and there is a possibility that voids may be generated.

The epoxy resin composition constituting the thermosetting resin layer 2-1 includes a monofunctional epoxy resin, a bisphenol A epoxy resin, a bisphenol F epoxy resin, a phenol novolak epoxy resin, a cresol novolak epoxy resin, and the like. And polyepoxy resins comprising one or more of these bromides; and polyhydric phenol compounds, urea derivatives, amine compounds, imidazole compounds, modified amine compounds, modified imidazole compounds, and acid anhydrides. A composition comprising a curing agent obtained by mixing seeds or two or more is recommended.

The composition may contain inorganic fillers such as crystalline silica, fused silica, alumina, aluminum nitride, boron nitride, silicon nitride, magnesia, magnesium silicate, etc., rubber components, viscosity modifiers, flame retardants, etc. good. The addition amount of the inorganic filler is preferably 50% by weight or more, and if it is less than that, the effect of reducing the thermal expansion coefficient and the effect of heat conduction are poor, and the reliability is reduced. It is strongly recommended that the composition has a curing temperature lower than the bonding temperature between the bump electrode of the printed wiring board and the terminal of the semiconductor chip. If the curing temperature is higher than the bonding temperature, a heat treatment at a temperature higher than the bonding temperature is required after the bonding, which not only complicates the process but also lowers the reliability of the bonded portion. This epoxy resin composition is usually adjusted to an appropriate viscosity with a solvent, applied to an appropriate synthetic resin film, and dried to form a thermosetting resin layer.

The synthetic resin film 2-2 is merely a carrier of the thermosetting resin layer, and thus there is no particular limitation on the material and the like, but the glass transition temperature is lower than the curing temperature of the thermosetting resin composition. A thermoplastic resin having, for example,
Polyolefins such as polyethylene and polypropylene, ethylene vinyl acetate copolymer, ethylene-alkyl acrylate copolymer, polyester, polyvinyl chloride, polyvinylidene chloride, polyurethane, polyamide, polyamideimide, polyetherimide, polysulfone, polyethersulfone, methyl A thermoplastic film made of a pentene copolymer or the like can be used. Although the thickness of the film is not particularly limited, it is usually used at a thickness of 30 to 500 μm.

As shown in FIGS. 2 and 3, the mounting sheet 2 has its thermosetting resin layer 2-1 bonded to the surface of the printed wiring board 1 on which the bump electrodes 1-2 are provided. . The bonding method is not particularly limited, but is usually performed by roll lamination or press lamination. The bonding is performed at a temperature equal to or higher than the softening temperature of the thermosetting resin layer before hardening and equal to or lower than the curing temperature. Therefore, at this stage, the thermosetting resin layer 2-1 is in a state before being cured. By this bonding step, the bump electrode 1 of the printed wiring board is formed.
-2 penetrates the thermosetting resin layer 2-1 of the mounting sheet, and their ends contact the synthetic resin film 2-2;
In some cases, the surface is strongly pressed.

Next, the synthetic resin film 2-2 of the mounting sheet 2 is peeled off. FIG. 4 shows a synthetic resin film 2-
2 shows a state where it has been completely removed. At this time, the tip of the bump electrode 1-2 is exposed from the surface of the thermosetting resin layer 2-1. Finally, as shown in FIG.
In the face-down method, each bump electrode 1-2 of the printed wiring board is connected to the corresponding terminal 3 of the semiconductor chip 3.
-2 is positioned so as to face and contact correctly, and bonding is performed by applying heat and pressure and, if necessary, ultrasonic vibration. The resin composition of the thermosetting resin layer 2-1 is softened by the heat applied at the time of joining, and then hardens to form a strong cured resin layer between the semiconductor chip 3 and the printed wiring board 1. . After joining in this manner, heat treatment may be applied as necessary, but in this case, the temperature must be lower than the joining temperature.

Hereinafter, an embodiment of mounting a commercially available semiconductor chip on a printed circuit board by the method of the present invention will be described. [Example 1] 260 parts by weight of spherical alumina and a solvent were added to 100 parts by weight of an epoxy resin composition composed of a phenol novolak type epoxy resin, a bisphenol F type epoxy resin, a phenol novolak resin, and a urea derivative, and kneaded and dispersed. The epoxy resin composition having a curing temperature of 160 ° C. was applied to an ethylene-vinyl acetate copolymer film having a glass transition temperature of −20 ° C. and a thickness of 100 μm and dried to obtain a semiconductor chip mounting sheet. The thickness of the thermosetting resin layer was 90 μm.

This mounting sheet is punched into the size of a semiconductor chip to be mounted, pressed by eutectic solder paste printing, and pressed on a bump electrode surface of a printed wiring board on which bump electrodes having a height of 100 μm are formed at 100 locations by reflow. Was applied. The sticking temperature was 80 ° C. Thereafter, the ethylene vinyl acetate copolymer film of the mounting sheet is peeled off from the printed wiring board, the tip of the bump electrode is exposed, and the position of the bump electrode and the terminal of the semiconductor chip is adjusted. Heat and pressure were applied to join the two, and at the same time, the thermosetting resin layer was cured. After joining, heat treatment was further performed at 180 ° C. for 1 hour to complete the curing of the thermosetting resin. At this time, the bonding between the bump electrode of the printed wiring board and the terminal of the semiconductor chip was good at all 100 points, and the connection portion did not break even after 1000 cycles of the temperature cycle test at −55 ° C. and 125 ° C.

Example 2 A thermosetting resin composition comprising a cresol novolak type epoxy resin, a bisphenol A type epoxy resin, an acid anhydride, aluminum nitride, and a solvent at a curing temperature of 180 ° C. was prepared. 50μ
m, and dried by drying to obtain a semiconductor chip mounting sheet. The thickness of the thermosetting resin layer is 165
μm. This mounting sheet is punched into a size of a semiconductor chip to be mounted, and a bump electrode having a height of 120 μm formed by ball bonding of gold wires is formed on each of the semiconductor chips.
It was attached to a printed circuit board at 00 at 120 ° C. by lamination using a hot roll. Thereafter, the polyester film of the mounting sheet is peeled off from the printed wiring board, the tip of the bump electrode is exposed, and the bump electrode and the terminal of the semiconductor chip are aligned.
Heat and pressure were applied while applying ultrasonic vibration at 00 ° C. for 30 seconds to join the two and simultaneously cure the thermosetting resin layer. At this time, the bonding between the bump electrode of the printed wiring board and the terminal of the semiconductor chip was good at all 100 points, and -5
After 1000 cycles of the temperature cycle test at 5 ° C. and 125 ° C., the connection did not break.

[Comparative Example 1] The thermosetting resin composition used in Example 1 was molded into a sheet, and directly sandwiched between the individual semiconductor chips used in Example 1 and the printed wiring board.
After heating and pressing at 80 ° C., the temperature was raised to 220 ° C. to perform joining. In the connection portion between the bump electrode of the printed wiring board and the terminal of the semiconductor chip, 17 locations were defective.

[0021]

Since the present invention is constructed as described above, according to the present invention, the process is simple, the cost is low, and the bump electrodes of the printed wiring board are securely connected to the terminals of the semiconductor chip. In addition, it is possible to provide a novel semiconductor chip mounting method which does not cause a problem such as a connection failure and a mounting sheet used for carrying out the method.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view showing a portion related to the present invention in a configuration of a printed wiring board.

FIG. 2 is a partially enlarged sectional view of a semiconductor chip mounting sheet.

FIG. 3 is a partially enlarged cross-sectional view showing a state in which a semiconductor chip mounting sheet is bonded to a face side of a printed wiring board on a bump electrode side.

FIG. 4 is a partially enlarged cross-sectional view showing a state where the synthetic resin film of the mounting sheet is completely peeled off.

FIG. 5 is a partially enlarged cross-sectional view showing a state where a semiconductor chip is mounted on the printed wiring board shown in FIG. 4 by a face-down method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed wiring board 1-1 Substrate 1-2 Bump electrode 2 Semiconductor chip mounting sheet 2-1 Thermosetting resin layer 2-2 Synthetic resin film 3 Semiconductor chip 3-1 Substrate 3-2 Terminal

Claims (6)

[Claims] 1. A method for mounting a semiconductor chip (3) on a printed wiring board (1), comprising the following steps [a] to [e]. [A] On one surface of the synthetic resin film (2-2), a thermosetting resin layer (2) having the same thickness T as the height H of the bump electrode (1-2) of the printed wiring board (1). Manufacturing a semiconductor chip mounting sheet (2) provided with -1). [B] Bump electrode (1-2) of printed wiring board (1)
Pressure bonding the thermosetting resin layer (2-1) of the semiconductor chip mounting sheet (2) to the surface provided with. [C] a step of peeling off the synthetic resin film (2-2) of the semiconductor chip mounting sheet (2) pressed against the bump electrode surface of the printed wiring board (1). [D] Bump electrode (1-2) of printed wiring board (1)
Is positioned so as to correctly face and contact the terminal (3-2) on the corresponding semiconductor chip (3). [E] Bump electrode (1-2) of printed wiring board (1)
Bonding to the corresponding terminals (3-2) on the semiconductor chip (3) and heat-curing the thermosetting resin (2-1). 2. A thermosetting resin layer having a thickness T substantially equal to the height H of the bump electrode (1-2) of the printed wiring board (1) on one surface of the synthetic resin film (2-2). (2
The semiconductor chip mounting sheet (2) used for carrying out the method for mounting a semiconductor chip on a printed wiring board according to claim 1, characterized in that the sheet (2) is provided. 3. The semiconductor chip mounting sheet (2) according to claim 2, wherein the synthetic resin film (2-2) has a glass transition temperature lower than the curing temperature of the thermosetting resin (2-1). 4. The thermosetting resin (2-1) is made of an epoxy resin composition, and the epoxy resin composition is used for forming a bump electrode (1-2) on a printed wiring board (1) and a semiconductor chip (3). The semiconductor chip mounting sheet (2) according to claim 2 or 3, having a curing temperature lower than a bonding temperature of the terminal (3-2). 5. The thermosetting resin (2-1) contains 50% by weight.
The semiconductor chip mounting sheet (2) according to any one of claims 2 to 4, comprising the above inorganic filler. 6. The thickness T (unit: μm; the same applies hereinafter) of the thermosetting resin layer (2-1) is set so that the height of the bump electrode (1-2) of the printed wiring board (1) to be mounted is H. And when
The semiconductor chip mounting sheet (2) according to any one of claims 2 to 5, wherein H-30≤T≤H + 30.