JPH11265910A - Resin film for electric connection and electric connecting method using resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve connection reliability in the case of an electric connection due to a resin film. SOLUTION: Concerning a resin film 1, insulated particles 3 of small thermal expansion coefficient and large diameter and conductive particles 3 of small diameter are mixed into insulated resins. Concerning the conductive particle 4, a metal layer is formed on the surface of a core insulator composed of spherical silica similarly to the insulated particle 3. When such a resin film 3 is thermally press-fitted while being sandwiched between a metal projection 8a and a connecting terminal 7, a thermosetting or thermoplastic resin 2 mechanically bonds a semiconductor chip 5 and a circuit board 6. At such a time, since the conductive particle 4 of small diameter is residual between the metal projection 8a and the connecting terminal 7 sometimes but the insulated particle 5 of large diameter is not residual, the electric connection is secured. Further, since the thermal expansion coefficient is lowered by the insulated particles 3 and the core insulator, the degradation of strength with the passage of time can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin film for electrical connection and an electrical connection method using the same.

[0002]

2. Description of the Related Art In recent years, as electric and electronic devices have become smaller and thinner, the number of configurations in which minute components such as semiconductor chips and minute circuits such as circuit boards are connected has increased. In addition, the wiring pitch of fine circuits is becoming smaller and smaller.

Conventionally, such a connection between a component and a circuit is
The mainstream method is to wire-bond the connection terminals to each other. However, since it is more advantageous to directly connect the connection terminals to face each other in terms of the simplicity of the manufacturing process, cost, etc. Connections are active. The electrical connection between the connection terminals is performed by a method such as connection by solder, connection by a conductive paste, or formation of each connection terminal by gold and compression bonding of gold.

[0004] The portion where the connection terminals are directly connected to each other is often sealed with a resin in order to protect it from the external environment and improve the connection reliability. Specifically, after the connection is made, a liquid inexpensive resin (generally, a thermosetting resin such as a low-viscosity epoxy resin or the like) is passed from the gap between the adjacent connection terminals toward the space between the opposite connection terminals. ) Is introduced and then cured. However, as miniaturization and thickness reduction progress, the gap between the component and the circuit and the gap between adjacent connection terminals become smaller, and it becomes more difficult to flow the liquid resin (so-called underfill).

Therefore, as a method of preventing underfill, a liquid resin is applied in advance to a region of one component (for example, a circuit board) on which the other component (for example, a semiconductor chip) is mounted, and the connection terminals are connected to each other. Are aligned and thermocompression-bonded to perform both electrical connection and mechanical bonding (disclosed in JP-A-2-7180).
In this method, the connection terminals of both parts are in direct contact with each other and are electrically connected by the contraction force of the thermosetting resin at the time of curing.

[0006]

When an electric / electronic device is used in a high-temperature environment, or when it is located near a high-temperature heat-generating semiconductor element such as a power module, the resin for joining the components is not used. The resin expands when heated, and after use is cooled, the resin contracts. The repetition of the expansion and contraction causes deterioration of the resin.

In the conventional connection method, both parts are relatively held only by the curing shrinkage force of the resin around the connection terminals, and the conduction between the two connection terminals is ensured. However, as described above, as the resin deteriorates due to repeated expansion and contraction, the contraction force of the resin is gradually reduced. Then, when the curing shrinkage of the resin at the time of cooling is smaller than the expansion of the resin at the time of heating, an electrical connection failure occurs.

In order to prevent this electrical connection failure, it is necessary to reduce the thermal expansion coefficient of the resin to suppress the thermal expansion. Therefore, usually, insulating particles such as silica particles, which are inorganic substances having a small thermal expansion coefficient, are mixed in the resin.
Thereby, the coefficient of thermal expansion of the resin can be reduced. However, if the surface of the connection terminal is smooth, resin is interposed between the connection terminals facing each other, and electrical connection failure is likely to occur. In particular, insulating particles such as silica particles mixed in the resin are sandwiched between the connection terminals, so that the direct contact between the connection terminals is interrupted and the electrical connection tends to be uncertain.
As shown in FIG. 6, even a configuration in which a metal protrusion (bump) having a sharp tip is provided on a connection terminal of a component (disclosed in Japanese Patent Application Laid-Open No. 9-97816), a metal protrusion 11 and a connection facing the metal protrusion 11 are provided as shown in FIG. There is a possibility that a large number of insulating particles 14 in the resin film 13 are interposed between the terminal 12 and the terminal 12, and the electrical connection becomes unstable.

As described above, when fixing using a thermosetting liquid (paste) resin in flip chip connection, there is a problem that the curing time of the resin is as long as several minutes to several hours and the productivity is low. In addition, when applying liquid resin to an area of one component on which the other component is to be mounted, aligning the respective connection terminals, and then performing thermocompression to electrically and mechanically join the resin, the resin is used during thermocompression. The insulating particles mixed therein may be sandwiched between the connection terminals facing each other, resulting in poor connection.

It is an object of the present invention to provide a resin film for electrical connection that can be connected in a short time and has high connection reliability, and an electrical connection method using the resin film.

[0011]

The resin film for electrical connection of the present invention comprises an insulating resin, insulating particles contained in the resin, and an insulating resin contained in the resin. And conductive particles having a smaller particle size than the conductive particles.

The conductive particles may be formed by forming a metal layer on a surface of a core insulator.

[0013] The insulating particles and the core insulator of the conductive particles may be the same inorganic particles. In that case, it is preferable that the insulating particles and the core insulator of the conductive particles are spherical silica.

[0014] An insulating resin layer may be interposed between the core insulator of the conductive particles and the metal layer.

[0015] The resin may be any of a thermosetting resin, a thermoplastic resin, and a mixture of a thermosetting resin and a thermoplastic resin.

It is preferable that the insulating particles have a smaller coefficient of thermal expansion than the resin.

Further, according to the electrical connection method using a resin film of the present invention, an insulating resin is provided on a connection terminal provided on one of the components, and an insulating resin and a conductive material having a smaller diameter than the insulating particle are provided. Temporarily bonding the resin film containing the particles, and aligning the connection terminal of the one component and the connection terminal provided on the other component so as to face each other via the resin film. And a step of mechanically joining the two parts by melting and then hardening the insulating resin, and conducting the connection terminals facing each other.

Further, the method includes a step of forming a metal projection having a sharp tip on the connection terminal of the other component.

The one component may be a circuit board, and the other component may be a semiconductor chip.

According to the present invention, since a resin film is used instead of a liquid resin, electrical connection and mechanical bonding can be performed in a shorter time. Furthermore, if the conductive particles are configured to have a smaller particle size than the insulating particles, the insulating particles having a large particle size are excluded from the connection terminals when the opposite connection terminals are thermocompression-bonded with a resin film interposed therebetween. Since the conductive particles having a small particle diameter remain preferentially, the connection reliability is improved.

If the thermal expansion coefficient of the insulating particles is smaller than that of the resin, poor connection with time due to expansion and contraction of the resin is less likely to occur, and the mechanical strength, heat resistance and moisture resistance are improved.

[0022]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic sectional view of the resin film 1 of the present invention. In this case, insulating particles 3 and conductive particles 4 are substantially uniformly dispersed in insulating resin 2 serving as a base, and are formed into a film shape.

The insulating resin 2 is made of a thermosetting resin, a thermoplastic resin, a mixture thereof, or the like, and its material is not particularly limited. Examples of the thermosetting resin include epoxy resins such as bisphenol A type, dicyclopentadiene type, cresol novolak type, biphenyl type, and naphthalene type, resol type and novolak type phenol resins, and (R ₂ SiO) n. A silicone resin represented by a structural formula (R is a methyl group or a phenyl group) is used. As the thermoplastic resin, acrylic resin, polyester resin, ABS resin, polycarbonate resin, phenoxy resin and the like are used.

The insulating particles 3 are made of silica, alumina, boron nitride, silicon nitride or the like. Particularly preferably, spherical silica particles having low cost, low specific gravity, and high fluidity are used. The mixing amount of the insulating particles 3 is preferably about 20 to 70% by weight.

The conductive particles 4 include nickel, solder, copper,
A metal layer 4b made of nickel, gold or the like is formed on the surface of a metal particle such as silver or a core insulator 4a made of an insulating resin as shown in FIG.
Are used. The mixing amount of the conductive particles is
About 1 to 10% by volume is preferable. The conductive particles 4 are formed to have a smaller particle size than the insulating particles 3.

Next, an electrical connection method using the resin film 1 will be described with reference to FIGS. In the present embodiment, one of the electric components is the circuit board 5 and the other is the semiconductor chip 6. Here, the circuit board 5 is formed by forming a wiring pattern (not shown) on the surface of a glass epoxy resin substrate, a ceramic substrate such as alumina, or a substrate such as a glass substrate. A terminal 7 is provided. Also, a plurality of connection terminals 8 such as aluminum pads are provided on the surface of the semiconductor chip 6 corresponding to the connection terminals 7 of the circuit board 5.

In this embodiment, first, on the connection terminal 8,
A metal projection (bump) 8a having a sharp tip is formed (step 101). As an example of a method of forming the metal projection 8a, for example, after bonding a bonding wire such as gold or aluminum used for wire bonding to the connection terminal 8 of the semiconductor chip 6, the wire is torn off with an excessive force, and A method of forming by leaving only a part on the connection terminal 8 may be used.

The resin film 1 of the present invention having the above-described structure is temporarily pressure-bonded to a region on the surface of the circuit board 6 where the semiconductor chip 5 is to be mounted (step 102). The shape of the resin film 1 is slightly larger than that of the semiconductor chip 5, and the thickness may be approximately the same level as the sum of the heights of the connection terminals 7, 8 and the metal protrusions 8a of the semiconductor chip 5 and the circuit board 6. . The resin film 1 is a film containing the insulating particles 3 and the conductive particles 4 in the resin 2 as described above.

Then, the semiconductor chip 5 and the circuit board 6 are aligned so that the respective connection terminals 7, 8 face each other (step 103). The semiconductor chip 5 is placed on the circuit board 6 in the aligned state, and thermocompression-bonded (Step 104). After heating and cooling to room temperature, the resin 1 is once melted and then hardened and contracted, so that the semiconductor chip 5 and the circuit board 6 are mechanically joined. At this time, sharp metal projections (bumps) 8a on the connection terminals 8 of the semiconductor chip 5
The tip is crushed by pressure and spreads. When the metal projection 8a is crushed and spread, the resin 2 located in the gap between the circuit board 6 and the connection terminal 7 is pushed outward. At this time, first, the insulating particles 3 having a large particle size are extruded, and in addition, the conductive particles 4 having a small particle size are extruded. The conductive particles 4 having a small particle size slightly remain in the gap between the metal protrusion 8a and the connection terminal 7, but have conductivity, so that the connection terminals 7,
8 does not affect the electrical connection between them. The time required for connection by thermocompression bonding is shorter than in the case where a liquid resin is used.

Ideally, the semiconductor chip 5 and the circuit board 6
It is desirable that nothing be interposed in the gap between the metal projection 8a and the connection terminal 7 at the time of thermocompression bonding, but it is difficult to completely suppress the interposition. At that time, if the insulating particles 3 are interposed in the gap between the metal projection 8a and the connection terminal 7, the electrical connection between the connection terminals 7 and 8 becomes uncertain. However, if the conductive particles 4 are interposed in this gap, electrical connection can be secured without any problem. The conductive particles 4 of the present embodiment have a smaller particle size than the insulating particles 3, and the smaller the particle size, the more the particles tend to remain between the connection terminals 7 and 8. The conductive particles 4 preferentially remain between the gaps 8 to ensure electrical connection. The particle size of the conductive particles is preferably 0.1 to 3 μm, the particle size of the insulating particles is about 5 to 10 μm, and the particle size distribution is preferably narrow. In particular, it is optimal that the conductive particles 4 have a single particle size. .

In the present embodiment, since the insulating particles 3 having a small coefficient of thermal expansion are mixed in the resin 2, the thermal expansion of the entire resin film 1 is suppressed to be small, and the resin 2 with the time change due to the temperature fluctuation. Instability of the connection due to deterioration is prevented.
In particular, the larger the blending amount (occupied volume) of the insulating particles 3 is, the more the thermal expansion coefficient is reduced. Further, as shown in FIG. 2, when the conductive particles 4 also include the core insulator 4 a made of a material having a small thermal expansion coefficient (for example, spherical silica) similarly to the insulating particles 3, the thermal expansion of the resin film 1 can be improved. This is effective for preventing the reduction of the coefficient and the connection instability over time. However, if the conductive particles 4 are too large or too large, an electrical short circuit may occur in the resin film 1, so that the large-diameter insulating particles 3 and the small-diameter conductive particles 4 are separated. A mixed configuration is most desirable.

FIG. 5 is a sectional view of the conductive particles 9 according to the second embodiment of the present invention. The conductive particles 9
Has an insulating resin layer 9a provided between the core insulator 4a and the metal layer 4b as in the first embodiment shown in FIG. 2, thereby improving the adhesion between the core insulator 4a and the metal layer 4b. doing.

[0034]

An embodiment in which the semiconductor chip 5 and the printed board 6 are connected at a pitch of 100 μm using the resin film 1 of the present invention will be described below with reference to a table showing specific results.

Each table shows the main structure of the resin film, the connection conditions by thermocompression bonding, the electric resistance immediately after the connection, and the results of a high-temperature and high-humidity storage test (left at a temperature of 85 ° C. and a humidity of 85% for 800 hours). Connection reliability (represented as reliability 1 in the table) and connection reliability as a result of a temperature cycle test (500 cycles of a cycle of leaving at −40 ° C. for 30 minutes and leaving at 125 ° C. for 30 minutes). (Reliability 2 is shown in the table). Comparative examples are also shown. (Example 1)

[0036]

[Table 1] (Example 2)

[0037]

[Table 2] (Example 3)

[0038]

[Table 3] (Example 4)

[0039]

[Table 4] (Example 5)

[0040]

[Table 5] (Example 6)

[0041]

[Table 6] In the above-described six embodiments, the configuration in which the large-diameter insulating particles 4 and the small-diameter conductive particles 5 having a small coefficient of thermal expansion are mixed in the resin 2 has excellent electrical connection reliability. It is clear that.

Here, the results of conducting the same experiment as in Examples 1 to 6 using a resin film having a structure different from that of the present invention are shown as comparative examples. (Comparative Example 1)

[0043]

[Table 7] In Comparative Example 1, the connection was made with a resin film in which the conductive particles were not mixed. It can be seen that the reliability of the electrical connection was lost when the temperature was changed repeatedly. (Comparative Example 2)

[0044]

[Table 8] In Comparative Example 2, the connection was made with a resin film in which the insulating particles were not mixed, but the reliability of the electrical connection was lost when the device was placed under high temperature and high humidity and when the temperature fluctuation was repeated. You can see that. (Comparative Example 3)

[0045]

[Table 9] Comparative Example 3 was connected by a resin film in which small-diameter insulating particles and large-diameter conductive particles were mixed,
Immediately after the connection by thermocompression bonding, it can be seen that the electrical connection is defective (short). (Comparative Example 4)

[0046]

[Table 10] Comparative Example 4 was connected by a resin film in which insulating particles and conductive particles having the same diameter were mixed, but it can be seen that the reliability of the electrical connection is lost when the temperature changes are repeated.

[0047]

According to the present invention, the conductive particles in the resin film have a smaller particle size than the insulating particles. Large insulating particles are eliminated and electrical connection is ensured.

In addition, since insulating particles having a small coefficient of thermal expansion are mixed in the resin, the coefficient of thermal expansion of the entire resin film is reduced, so that a decrease in mechanical connection strength with time can be prevented, and heat resistance and heat resistance can be reduced. Improves moisture resistance. It is more effective if the conductive particles have a structure including a core insulator similar to the insulating particles inside. Further, when the insulating particles and the core insulator are the same inorganic particles, the production can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a resin film according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a conductive particle according to the first embodiment of the present invention.

FIGS. 3A and 3B are schematic cross-sectional views illustrating an electrical connection method according to the first embodiment of the present invention, wherein FIG. 3A is a view before thermocompression bonding, and FIG.

FIG. 4 is a flowchart of an electrical connection method according to the first embodiment of the present invention.

FIG. 5 is an enlarged sectional view of a conductive particle according to a second embodiment of the present invention.

6A and 6B are schematic cross-sectional views showing a conventional electrical connection method, in which FIG. 6A shows a state before thermocompression bonding, and FIG. 6B shows a state after thermocompression bonding.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 resin film 2 insulating resin 3 insulating particles 4 conductive particles 4a core insulator 4b metal layer 5 semiconductor chip 6 circuit board 7 connection terminal 8 connection terminal 8a metal protrusion (bump) 9 conductive particle 9a insulating resin layer 11 Metal protrusions (bumps) 12 Connection terminals 13 Resin film 14 Insulating particles

Claims (16)

[Claims] 1. An electrical device comprising: an insulating resin; insulating particles contained in the resin; and conductive particles having a smaller particle size than the insulating particles contained in the resin. Resin film for connection. 2. The resin film for electrical connection according to claim 1, wherein the conductive particles are formed by forming a metal layer on a surface of a core insulator. 3. The resin film for electrical connection according to claim 2, wherein the insulating particles and the core insulator of the conductive particles are the same inorganic particles. 4. The resin film for electrical connection according to claim 3, wherein the insulating particles and the core insulator of the conductive particles are spherical silica. 5. The resin film for electrical connection according to claim 2, wherein an insulating resin layer is interposed between the core insulator of the conductive particles and the metal layer. 6. The electrical device according to claim 1, wherein the resin is any one of a thermosetting resin, a thermoplastic resin, and a mixture of a thermosetting resin and a thermoplastic resin. Resin film for connection. 7. The resin film for electrical connection according to claim 1, wherein the insulating particles have a smaller coefficient of thermal expansion than the resin. 8. On a connection terminal provided on one component,
Temporarily compressing a resin film containing insulating particles and conductive particles smaller in diameter than the insulating particles in the insulating resin; and providing the connection terminals of the one component and the other component. And a step of positioning the connected terminals so that they face each other with the resin film interposed therebetween. The two parts are mechanically joined together by melting and then curing the insulating resin. Electrical connection method using a resin film including a step of conducting the connection terminals. 9. The electrical connection method using a resin film according to claim 8, further comprising a step of forming a metal projection having a sharp tip on the connection terminal of the other component. 10. The electrical connection method using a resin film according to claim 8, wherein the conductive particles are formed by forming a metal layer on a surface of a core insulator. 11. The insulating particles and the core insulator of the conductive particles are the same inorganic particles.
An electrical connection method using the resin film described in Item 0. 12. The electrical connection method using a resin film according to claim 11, wherein the insulating particles and the core insulator of the conductive particles are spherical silica. 13. The insulating resin layer interposed between the core insulator of the conductive particles and the metal layer.
An electrical connection method using the resin film according to any one of items 12 to 12. 14. The resin film according to claim 8, wherein the resin is any one of a thermosetting resin, a thermoplastic resin, and a mixture of a thermosetting resin and a thermoplastic resin. Electrical connection method using 15. The method according to claim 8, wherein the one component is a circuit board, and the other component is a semiconductor chip. 16. The electrical connection method using a resin film according to claim 8, wherein the insulating particles have a smaller coefficient of thermal expansion than the resin.