JPH11245081A - Heat melting joint member and semiconductor packaging device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To significantly improve fatigue life of a joint part without requiring large and expensive facilies or giving an adverse influence to other circuit parts. SOLUTION: A conductive paste 1, in which fibrous long members 11 wherein specific gravity of one end 111 is bigger than that of the conductive paste 1 are mixed, is applied on a surface of a member 2 to be jointed on a wiring substrate side. Further, a member 3 to be jointed on a building part side is put on the conductive paste 1. Since the viscosity of the conductive paste 1 is high under such a condition, the posture of the long member 11 remains irregular in the conductive paste 1. If the conductive paste 1 is heated to lower its viscosity, the long members 11 are set afloat in the conductive paste 1. Therefore, one end 111 side with a larger specific gravity sinks, and the long members stand downward in an approximately upright condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-melt joining member and a semiconductor mounting device using the same, and more particularly, to a hot-melt joining member capable of greatly improving the fatigue life of a joining portion and the vicinity thereof, and a semiconductor device using the same. The present invention relates to a semiconductor mounting device used.

[0002]

2. Description of the Related Art In recent years, in semiconductor mounting devices, high-density mounting has progressed along with miniaturization and enhancement of functions, and in order to cope with reduction in the size and weight of printed circuit boards, packages of semiconductor elements and LSI chips mounted on the substrates have been developed. The pitch and area between the electrodes are becoming narrower. As a result, at the solder joint between the printed circuit board and the mounting component such as a package or an LSI chip, the rate of defective bonding due to poor wettability at the time of soldering, and the thermal fatigue destruction caused by the thermal cycle during the operation of the device. Growth is a problem. In particular, at present, no definitive countermeasures can be found for disconnection failure due to thermal fatigue failure.

[0003] For example, Japanese Patent Application Laid-Open No. 6-326437 discloses a technique in which a conductive paste is applied to conductive fibers and thermally cured in order to improve the mechanical strength of the solder. Also, JP-A-8-1371 or JP-A-8-371.
Japanese Patent No. 8531 discloses a technique in which a magnetic field is applied to a molten solder including a magnetic elongated body so that the magnetic elongated body in the solder is arranged in a direction orthogonal to a bonding surface.

FIG. 8 is a diagram schematically showing a conventional joining process for aligning the direction of a magnetic elongated body by a magnetic field. In a conductive paste 1 such as a paste solder, a fibrous magnetic length is provided. The scale 30 is mixed in advance.

[0005] In the bonding step using the conductive paste 1, first, the conductive paste 1 having the above-described structure is applied to the surface of one member 2 to be bonded, and the other member 3 is bonded to the conductive member 1. Place on paste 1. In this state, since the conductive paste 1 has sufficient viscosity, the posture of the elongated body 30 inside the conductive paste 1 remains irregular.

Here, when the conductive paste 1 is heated by, for example, a reflow device to generate a magnetic field in a direction perpendicular to the joint surface while reducing the viscosity, the elongated body 30 is substantially formed in the conductive paste 1. It becomes upright posture.

[0007]

In the prior art in which a conductive paste is applied to the conductive fiber and thermally cured, the direction of the fiber is irregular, and the fiber arrangement cannot be aligned in a desired direction. If the fibers are arranged in the same direction as the cracks that may sometimes occur, there is a problem that the cracks will progress rather.

Further, in the prior art in which the direction of the magnetic elongated body is aligned by a magnetic field, there is a problem that the magnetic elongated body is limited to a magnetic material such as Fe, Cr, Ni, or an alloy thereof. The solder material is Pb which is a diamagnetic material.
Therefore, there is a problem that an extremely large-scale and expensive facility is required in order to generate a magnetic field that can move the magnetic elongated body in a desired direction therein. Further, when the coil is mounted on the printed wiring board, there is a problem that an induced current is generated by a magnetic field, which adversely affects other circuit elements.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to greatly reduce the fatigue life of a joint without requiring large-scale and expensive equipment and without adversely affecting other circuit components. It is an object of the present invention to provide a heat-fusible joining member which can be improved and a semiconductor mounting device using the same.

[0010]

Means for Solving the Problems In order to achieve the above object, the present invention is characterized in that the following means are taken. (1) At least a conductive material is mixed, and in a hot-melt joining member that melts in a heated state, a fibrous elongated body is further mixed, and the specific gravity of one end of the elongated body is set to a value in the molten state. The specific gravity of the hot-melt joining member was made different from the specific gravity of the hot-melt joining member to such an extent that the one end could float and sink in the fusible joining member. (2) In a semiconductor mounting device in which a semiconductor device and a wiring board are joined by a hot-melt joining member at respective joining surfaces, a fibrous long body is mixed with the hot-melt joining member, and the long body is mixed. The specific gravity of one end of the heat-fusible joining member is made larger (or smaller) than the specific gravity of the heat-fusible joining member in a molten state, so that the elongated bodies are arranged substantially perpendicular to the surface to be joined. .

According to the above configuration (1), since the elongated bodies are aligned in the direction perpendicular to the gravity in the molten conductive material, the elongated bodies are arranged perpendicular to the thermal stress. By doing so, the proof stress against thermal stress is improved. Further, according to the above configuration (2), when the heat-fusible joining member is melted and solidified, the elongated bodies are aligned in a direction perpendicular to gravity, so that
When the elongated bodies are arranged perpendicular to the thermal stress, the heat-fusible joining member has improved resistance to thermal stress.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram schematically showing a joining process using a conductive paste 1 as a hot-melt joining member according to a first embodiment of the present invention. In the present embodiment, for example, a paste-like solder in which solder and a solvent are mixed is used as the conductive paste 1, and the specific gravity of one end 111 of the conductive paste 1 is larger than the specific gravity of the conductive paste 1. Is mixed.

In the bonding step using the conductive paste 1 including the elongated body 11, the conductive paste 1 having the above-described configuration is first applied to the surface of the member 2 to be bonded on the wiring board side, and further mounted. The member 3 to be joined on the component side is mounted on the conductive paste 1. In this state, the viscosity of the conductive paste 1 is high.
'S posture remains irregular. Here, when the conductive paste 1 is heated by, for example, a reflow device to reduce the viscosity, the elongated body 11 is in a floating state in the conductive paste 1, so that one end 111 having a large specific gravity sinks, and the elongated body 11 is elongated. The body 11 assumes a downward substantially upright posture. In addition, the solvent contained in the conductive paste 1 is splashed by this heat treatment, and the conductive paste 1 is solidified after the heat treatment, so that the elongated body 11 maintains a substantially upright posture.

As described above, according to the present embodiment, the elongated body 11 in the conductive paste 1 can be set in a substantially upright posture without being exposed to a magnetic field, so that a load acting in the horizontal direction due to a difference in expansion coefficient can be reduced. At the same time as the drag increases, the progress of cracks entering the horizontal direction can be delayed. Therefore, no large-scale equipment for applying a magnetic field is required,
Further, the fatigue life of the joint can be greatly improved without adversely affecting other circuit components.

In the above description, the specific gravity at one end of the elongated body is set to be larger than the specific gravity of the conductive paste 1. On the contrary, the second embodiment shown in FIG. As described above, the elongated body 12 in which the specific gravity of the one end 121 is smaller than the specific gravity of the conductive paste 1 may be mixed. With this configuration, the one end 121 side having a small specific gravity floats, and the elongated body 12 can be set in a substantially upright posture in which the one end 121 side is upward.

Further, the specific gravity at one end of the elongated body may be increased and the specific gravity at the other end may be reduced. With this configuration, the posture of the elongated body can be made closer to the upright posture.

Further, the elongated body 11 having one end having a specific gravity larger than that of the conductive paste 1 tends to settle down with respect to gravity. This is effective for improving the fatigue life near the joining member 2. On the other hand, the elongated body 12 having a sufficiently small specific gravity at one end tends to float upward with respect to gravity, and is therefore effective in improving the fatigue life near the member 3 to be joined. Therefore, as in the third embodiment shown in FIG. 3, the elongated body 11 having one end having a specific gravity sufficiently larger than that of the conductive paste 1, and one end having a specific gravity sufficiently smaller than that of the conductive paste 1. By mixing the elongated body 12 with the conductive paste 1, the fatigue life in the vicinity of each joining member can be simultaneously improved.

Next, the elongated members 11 and 12 having the above-described configuration are used.
Will be described. In the present embodiment, as shown in FIG. 4A, the conductive fiber 10 is held by a special jig 19 so that one end thereof is exposed. Next, as shown in FIG. 2B, the tip of the conductive fiber 10 is discharged by the discharge device 20. As a result, the tip of the conductive fiber 10 is processed into a ball shape as shown in FIG. At this time, if necessary, a conductive member may be applied to the ball-shaped tip portion by coating or plating.

The method of machining the tip into a ball shape is not limited to the above-mentioned electric discharge machining, and the tip may be worked into a ball shape by bringing the tip into contact with a heating plate or the like and heating. After processing the tip into a ball shape as described above,
As shown in FIG. 5 (d), by cutting the conductive fiber 10 at a desired position, a long body having one end processed into a ball shape is completed as shown in FIG. 5 (a). .

Here, if the elongated body 11 having one end having a specific gravity larger than that of the conductive paste 1 is formed, the conductive fiber 10 has a specific gravity (or density) of solder (8.4 g · eutectic solder). Cu (8.9), Au larger than cm ⁻³ )
A simple substance such as (19.3), Ni (8.9) and Pb (11.3) or an alloy containing these may be used. In addition, if the elongated body 12 having one end having a specific gravity smaller than that of the conductive paste 1 is formed, Al (2.7) or Zn (7.
A simple substance such as 1) or an alloy containing these may be used.

The method of forming the elongated body is not limited to the above method.
As shown in FIG. 5 (b), an appropriate metal material having a melting point higher than that of solder or a material obtained by plating a plastic with metal is used as the conductive fiber 10, and one end of which has a specific gravity larger than that of solder. Cu, Au, Ni, Pb, or the like, or Al, Zn, or the like having a specific gravity smaller than that of the solder may be added as a simple substance or an alloy by plating.

FIG. 6 is a view schematically showing a bonding step using a conductive paste 1 according to a fourth embodiment of the present invention. The present embodiment is characterized in that one end 131 of the fibrous long body 13 exhibiting good wettability to solder is configured to repel solder.

In the joining step using the conductive paste 1 as described above, first, one of the members to be joined 2
Is coated with the conductive paste 1 having the above-described structure, and the other member 3 to be joined is mounted on the conductive paste 1. In this state, since the viscosity of the conductive paste 1 is high, the posture of the elongated body 13 inside the conductive paste 1 remains irregular. Here, when the conductive paste 1 is heated in the same manner as described above to reduce the viscosity, the elongated body 13 is in a floating state in the conductive paste 1. Are exposed or projected outward from the molten solder. On the other hand, the other portion exhibiting good wettability stops while being buried in the solder, and as a result, the elongated body 13 solidifies in a form arranged along the outer wall of the solder pam. Therefore, generation of cracks due to thermal stress is prevented by the elongated body 13.

As a method of giving solder repelling properties to one end, after forming a fibrous structure in the same manner as described above using various kinds of plastic materials having repelling properties or metals such as aluminum and tin, A method of coating a material (solder, gold, silver, etc.) wettable with solder by leaving it at one end 131 by an appropriate method such as an electroless plating method, or forming a main body portion with a material wettable by solder, There is a method of applying a solder-repelling member (a variety of organic resins such as silicon and fluororesin, and a metal such as aluminum and zinc which is hardly wet to solder) or applying an electroless plating. At this time, by adjusting the specific gravity of the elongated body 13 appropriately, the elongated body 13 can be concentrated on the member to be joined 2 side or the member to be joined 3 side.

In each of the embodiments described above, the linear long body is mixed in the conductive paste 1. However, if the whole body is long, for example, the fiber may be L
It may be processed into a mold, a T-shape, an X-shape or the like, and the specific gravity of the end in the longitudinal direction may be adjusted as described above.

FIG. 7 is a diagram schematically showing a bonding step using a conductive paste according to a fifth embodiment of the present invention.
In the present embodiment, one end 14 is provided in the conductive paste 1.
1 has a characteristic that the specific gravity of the conductive paste 1 is sufficiently larger than the specific gravity of the conductive paste 1 and the specific gravity of the other end 142 is mixed with the conductive wire 14 sufficiently smaller than the specific gravity of the conductive paste 1.

In the joining step using the conductive paste 1, the conductive paste 1 having the above-described structure is first applied to the surface of one member to be joined 2, and the other member 3 to be joined is electrically conductive. It is mounted on the paste 1. In this state, since the viscosity of the conductive paste 1 is high, the posture of the conductive wire 14 inside the conductive paste 1 remains irregular.

Here, when the conductive paste 1 is heated in the same manner as described above to reduce the viscosity, the conductive wire 14 becomes a floating state in the conductive paste 1, so that one end 141 having a large specific gravity is connected to the member to be joined. The other end 142 having a small specific gravity floats until it comes into contact with the member 3 to be joined. Therefore, one end 141 of the conductive wire 14 is on the lower side,
The other end 142 is in the upper substantially upright posture. Further, the solvent contained in the conductive paste 1 flies by this heat treatment,
In a cooled state, the conductive paste 1 hardens, so that the conductive wire 14 maintains a substantially upright posture.

Such a conductive wire 14 is connected to one end and the other end of a sufficiently thin conductive wire, for example, by welding or crimping a metal piece having a lower specific gravity than solder and a metal piece having a higher specific gravity than solder. This can be achieved by doing

According to the present embodiment, the resistance to the load acting in the horizontal direction is increased by the difference in the coefficient of thermal expansion, thereby improving the connection reliability. At the same time, even if the conductive wire 14 is not cut even if a crack is formed in the horizontal direction. Workpieces 2, 3
Since conduction between them is ensured, fatigue life and reliability are greatly improved.

In the above-described embodiment, a conductive paste such as a paste solder has been described as an example of the heat-fusible joining member. However, a long body is mixed in advance in the heat-fusible solder bump. You can leave it.

[0032]

According to the present invention, the following effects are achieved. (1) Since the heat-fusible joining member of the present invention is interposed between the joining surfaces and heated, the fibrous elongated bodies contained therein can be arranged in a direction perpendicular to the joining surface. ,
The proof stress against thermal stress acting in the direction parallel to the joining surface is improved. (2) In the semiconductor mounting device of the present invention, the mounting component and the wiring board are bonded using the heat-fusible bonding member having the above-described configuration, and the long fibrous body is perpendicular to the bonding surface in the bonding member. Since they are arranged in the direction, the proof stress against thermal stress acting in the direction parallel to the joining surface is improved. (3) Since the conductive wires are arranged in the joining member in a direction perpendicular to each joining surface such that one end and the other end thereof respectively contact one and the other of the joining surfaces, cracks or the like , The electrical connection can be maintained as long as the wire is not cut.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method of joining surfaces to be joined according to a first embodiment of the present invention.

FIG. 2 is a view showing a method of joining surfaces to be joined according to a second embodiment of the present invention.

FIG. 3 is a view showing a method of joining surfaces to be joined according to a third embodiment of the present invention.

FIG. 4 is a view showing a method of manufacturing a long body mixed into a conductive paste.

FIG. 5 is a diagram showing a configuration of a long body mixed in a conductive paste.

FIG. 6 is a view showing a method of joining surfaces to be joined according to a fourth embodiment of the present invention.

FIG. 7 is a view showing a method of joining surfaces to be joined according to a fifth embodiment of the present invention.

FIG. 8 is a view showing a method of joining surfaces to be joined according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Conductive paste, 2, 3 ... Joining surface, 11, 12,
13: long body, 14: conductive wire

Claims (13)

[Claims] 1. A heat-fusible joining member in which at least a conductive material is mixed and melted in a heated state, a fibrous long body is further mixed, and a specific gravity of one end of the long body is in a molten state. The specific gravity of the heat-fusible joining member is different from the specific gravity of the heat-fusible joining member to such an extent that the one end can float and sink in the heat-fusible joining member. 2. The device according to claim 1, wherein the specific gravity of one end of the elongated body is large enough to allow the one end to settle in the melted heat-fusible joining member. Hot-melt bonding member. 3. The method according to claim 1, wherein the specific gravity of one end of the elongated body is small enough to allow the one end to float inside the hot-melt joining member in a molten state. Hot-melt bonding member. 4. A heat-fusible joining member in which at least a conductive material is mixed and melted in a heated state, wherein the first and second elongated bodies having one end having a specific gravity different from each other are further mixed; The specific gravity of one end of the long body is large enough to allow the one end to settle in the heat-fusible joining member in a molten state, and the specific gravity of one end of the second long body is molten. A hot-melt joining member, which is small enough to allow the one end to float in the hot-melt joining member in the state. 5. A hot-melt joining member in which at least a conductive material is mixed and melted in a heated state, wherein a fibrous long body is further mixed, and one end of the long body is the hot-melt joint. A hot-melt joining member, wherein the member is repelled and at least a part other than the one end shows sufficient wettability to the hot-melt joining member. 6. A heat-fusible joining member in which at least a conductive material is mixed and melted in a heated state, a conductive long body is further mixed, and a specific gravity of one end of the long body is in a molten state. The specific gravity of the other end is large enough to allow the one end to settle in the hot-melt joining member, and small enough to allow the one end to float in the hot-melt joining member in the molten state. A heat-fusible joining member characterized by the above-mentioned. 7. The heat-fusible joining member is a conductive paste containing at least a paste-like conductive material and a solvent, wherein the solvent is vaporized in a molten state and then solidified in a cooled state. The heat-fusible joining member according to any one of claims 1 to 6, wherein 8. A semiconductor mounting device in which a semiconductor device and a wiring board are joined to each other on a surface to be joined by a hot-melt joining member, wherein the hot-melt joining member includes a fibrous elongated body; A semiconductor mounting device, wherein a body has a specific gravity at one end thereof larger than a specific gravity of the heat-fusible joining member in a molten state, and is arranged substantially perpendicular to the surface to be joined. 9. A semiconductor mounting device in which a semiconductor device and a wiring board are joined by a hot-melt joining member on respective surfaces to be joined, wherein the hot-melt joining member includes a fibrous elongated body, A semiconductor mounting device, wherein a body has a specific gravity at one end thereof smaller than a specific gravity of the heat-fusible joining member in a molten state, and is arranged substantially perpendicular to the surface to be joined. 10. A semiconductor mounting device in which a semiconductor device and a wiring board are joined to each other on a surface to be joined by a hot-melt joining member, wherein the hot-melt joining member includes a fibrous elongated body; The body has a specific gravity at one end thereof greater than the specific gravity of the heat-fusible joining member in the molten state, and a specific gravity of the other end thereof is greater than the specific gravity of the heat-fusible joining member in the molten state. A semiconductor mounting device, which is small and arranged substantially perpendicular to the surface to be joined. 11. A semiconductor mounting device in which a semiconductor device and a wiring board are joined to each other on a surface to be joined by a hot-melt joining member, wherein the hot-melt joining member comprises a fibrous first and second elongated body. The first elongate body has a specific gravity at one end thereof greater than the specific gravity of the heat-fusible joining member in a molten state, and the second elongate body has a specific gravity at one end thereof. A semiconductor mounting device, wherein the specific gravity of the heat-fusible joining members is smaller than a specific gravity in a molten state, and the respective members are arranged substantially perpendicular to the surfaces to be joined. 12. A semiconductor mounting device in which a semiconductor device and a wiring board are joined to each other on a surface to be joined by a hot-melt joining member, wherein the hot-melt joining member includes a fibrous elongated body; The body has a property that one end thereof repels the hot-melt bonding member in a molten state, and at least a part other than the one end has sufficient wettability with respect to the hot-melt bonding member in a molten state. The one end is exposed or protrudes from the surface of the hot-melt joining member, and at least a part other than the one end is embedded in the hot-melt joining member. Semiconductor mounting equipment. 13. A semiconductor mounting device in which a semiconductor device and a wiring board are joined to each other on a surface to be joined by a heat-fusible joining member, wherein the heat-fusible joining member includes a conductive elongated body, In the shaku, the specific gravity of one end is larger than the specific gravity of the heat-fusible joining member in the molten state, and the specific gravity of the other end is larger than the specific gravity of the hot-fusible joining member in the molten state. A length in a longitudinal direction is longer than an interval between the surfaces to be joined, and each of the one end portions is in electrical contact with each of the surfaces to be joined.