JPH11254185A - Flex joining material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorb variance in a height and a sphere diameter of a joining material without impairing prescribed electrical and thermal conductivity in mounting an electronic parts to a circuit by dispersing spherical and/or shapeless elastic heat resistant resin powder in lead free solder to produce a joining material. SOLUTION: This joining material 10 is formed by evenly dispersing spherical and/or shapeless elastic heat resistant resin powder 12 in 20-60 vol.% in lead free solder 11 of low melting point or high melting point. The heat resistant resin powder used comprises at least one kind among elastomeric, polyimide, epoxy, silicon, urethane, polymer or acrylic resins. An electrical conductive metal thin film from Sn, Ti, Pd, Pb, Au, Ag, Ni, etc., is formed on its surface. Further, the joining material is in a solid state and has a ball shape of 0.5-1.5 mm diameter, and as required it may be a wire material of 0.1-3 mm diameter or a rectangular cross section thin sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding material used for bonding an electrode pad formed on an electronic component, a circuit board, or the like, and more particularly, to a method for mounting an elastic heat-resistant resin powder inside solder. Flex bonding material.

[0002]

2. Description of the Related Art Conventionally, when an electronic component such as a semiconductor device is mounted on a circuit board, a bonding material having a predetermined shape is fixedly arranged on a plurality of electrode pads formed on the electronic component or the circuit board, and the bonding is performed. 2. Description of the Related Art An electrical conduction circuit is formed between an electrode corresponding to a material and the electrode. Examples of the bonding material include a solder bump, a solder ball, a metal ball having a core such as Cu in a solder ball, and a resin ball having an elastic resin as a core.

[0003]

However, since these joining materials are manufactured in advance in a mass production in a separate step before joining on the electrode pads, joining materials having exactly the same size and shape are manufactured. This is extremely difficult, and there is some variation in height and sphericity (diameter). Therefore, even if the degree of parallelism between the electronic component and the circuit board is accurate, the height of the bonding material interposed therebetween varies, so that in the process of bonding the electronic component to the circuit board, the crimping force is applied to the electronic component. In addition, it is necessary to press the bonding material on the electrode pad against the electrode on the other side to be bonded and heat it. In the case of mounting using the solder bump or solder ball,
Even if the height and sphericity of the solder bumps and solder balls vary, they can be absorbed by the crushing margin during re-melting, but they will be crushed by the weight and spread laterally, and between adjacent electrodes and leads. If the electronic component and the circuit board are narrow, it is difficult to maintain the stand-off between the electronic component and the circuit board. Also, in the case of mounting using metal balls, variations in height and sphericity are smaller than solder bumps and solder balls, and they are less likely to be crushed than solder bumps and solder balls. While the stand-off between the two can be maintained, an unjoined part or poor joint occurs in the other electrode to be joined, and a crimping force is applied to eliminate the unjoined part, or a preliminary solder layer is provided. There is a need. However, when a pressing force is applied, a large stress is applied to an electronic component such as a semiconductor device, and the stress remains at a joint portion of the metal ball. This may lead to destruction of the electronic component and peeling of the joint. In addition, the provision of the preliminary solder layer requires a step of forming the preliminary solder layer, which causes a problem of increasing the manufacturing cost.
Furthermore, when the bonding material according to the above-described conventional example is used, the bonding material in a bonded and hardened state has poor elasticity, so that a thermal stress or an external load due to a difference in thermal expansion coefficient between the electronic component and the circuit board causes. In addition, there is a problem that an excessive load is generated on the neck portion of the joining material, which leads to cracking. In the case of mounting using resin balls, it is more elastic than solder bumps, solder balls or metal balls, and can absorb thermal stress and external loads due to the difference in thermal expansion coefficient between electronic components and circuit boards. Although it seems that the above-mentioned problems have been solved, it is extremely difficult to manufacture balls having the same diameter, and there are problems similar to those of the solder bumps, solder balls, and metal balls. In addition, since the inside is an insulator, there is a problem that conductivity and heat dissipation are poor. The present invention has been made in view of such circumstances, and when mounting an electronic component on a circuit board, the height of the bonding material and the variation in sphericity (diameter) are absorbed, and the distance between the electronic component and the circuit board is reduced. Can be maintained, and the bonding material used for bonding can absorb thermal stress caused by a difference in thermal expansion coefficient between the electronic component and the circuit board, and maintain predetermined electrical conductivity and thermal conductivity. It is an object of the present invention to provide a flex bonding material that can be used.

[0004]

[MEANS FOR SOLVING THE PROBLEMS] Claim 1 which meets the above object.
The flex bonding material according to the present invention has a shape in a solidified state and is a bonding material used for connecting members to be electrically bonded, and is a heat-resistant resin powder having an elastic spherical and / or irregular shape. Are evenly distributed inside the solder. The flex bonding material according to claim 2 is the flex bonding material according to claim 1, wherein the heat-resistant resin powder is 20 to 60.
The volume% and the remainder mainly consist of low melting point or high melting point solder.

A flex bonding material according to a third aspect of the present invention is the flex bonding material according to the first aspect, wherein the heat-resistant resin powder is composed of 20 to 60% by volume, and the balance is mainly composed of lead-free solder. The flex bonding material according to claim 4, wherein the heat-resistant resin powder is an elastomer resin, a polyimide resin, an epoxy resin, or a silicon resin. , Urethane resin, polymer resin, or acrylic resin. The flex bonding material according to claim 5 is the flex bonding material according to any one of claims 1 to 4, wherein Sn, Ti, In, Pd, Pb-Sn, Au,
A conductive metal thin film layer such as Ag or Ni is formed.

A flex bonding material according to a sixth aspect is the flex bonding material according to any one of the first to fifth aspects, wherein the solidified state has an outer diameter of 0.05 to 1.5 m.
m. The flex bonding material according to claim 7 is the flex bonding material according to any one of claims 1 to 5, wherein the solidified state has a wire diameter of 0.1.
It consists of a wire rod of ３3 mm. In a flex bonding material according to an eighth aspect, in the flex bonding material according to any one of the first to fifth aspects, the shape of the solidified state is a thin plate material having a rectangular cross section.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is a front view of a flex bonding material according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a bonding state of an electronic component using the flex bonding material. FIGS. 3A and 3B are perspective views of a flex bonding material according to a second embodiment of the present invention and sectional views showing a state of use thereof, and FIGS. It is the perspective view of the flex bonding material which concerns on 3rd Embodiment, and sectional drawing which shows the use condition.

As shown in FIG. 1, the flex bonding material 10 according to the first embodiment of the present invention has a solid spherical shape (ball shape) having a diameter of 0.05 to 1.5 mm due to its application. Thus, it is composed of a mixture of the solder 11 and the spherical heat-resistant resin powder 12. The heat-resistant resin powder 12 has a diameter of 3 to 30 μm (preferably 10 to 20 μm).
m) About one or two or more of an elastomer resin, a polyimide resin, an epoxy resin, a silicon resin, a urethane resin, a polymer resin, and an acrylic resin. Then, on the surface of the heat-resistant resin powder 12, Sn, Ti, In, Pd, Pb-Sn, Au, A
g or a conductive metal such as Ni is plated. By plating the surface of the heat-resistant resin powder 12 with a conductive metal having good wettability with the solder, the solder 11 and the heat-resistant resin powder 12 are adapted to each other, and the heat-resistant resin powder 12 is added to the solder 11. It can be evenly distributed.

Here, the amount of the heat-resistant resin powder 12 is 20 to 60% by volume of the whole. As a result, a uniform mixture of the heat-resistant resin powder 12 and the solder 11 can be obtained, and the solder 11 can be given elasticity. Therefore, when the amount of the heat-resistant resin powder is less than 20% by volume of the whole, the elasticity is reduced, and when it exceeds 60% by volume, the uniform dispersibility between the solder and the heat-resistant resin powder is deteriorated, and the electric resistance is reduced. And the strength and bondability also deteriorate.

When the flex bonding material 10 is manufactured, as an example, the heat-resistant resin powder 12
Prepare In the production of the heat-resistant resin powder 12, the heat-resistant resin may be formed into a fibrous shape, melt-cut at a predetermined length, rapidly cooled, and formed into a spherical shape by the surface tension.
The plating of the conductive metal on the surface of the spheroidized heat-resistant resin powder 12 may be performed by electroless plating, or may be formed by vapor deposition or the like in some cases. Alternatively, a commercially available heat-resistant resin powder 12 or one whose surface is coated with a conductive metal can be used. After uniformly dispersing the heat-resistant resin powder 12 having a surface plated with a conductive metal in a molten solder by using means such as stirring, the powder is formed into a spherical shape, a thin plate shape, or a linear shape. . When the spherical flex bonding material 10 is formed, as an example, the molten solder uniformly dispersed in the molten solder by using a means such as stirring is subjected to an alternating pressure that repeats pressurization and decompression. The spherical flex bonding material 10 is manufactured by gradually dropping the oil from the thin tube into the oil. Here, the diameter of the flex bonding material 10 can be controlled by the inner diameter of the thin tube to be dropped and the magnitude and cycle of the alternating pressure.

FIG. 2 shows a semiconductor device 13 which is an example of an electronic component manufactured by using the spherical flex bonding material 10 manufactured as described above. Material 10 is used. Thus, even if the flex bonding material 10 has a difference in height, the solder 11 is melted by re-melting the flex bonding material 10, and the weight of the semiconductor device 13 and the margin of crushing of the flex bonding material 10 increase. Since the entire structure is joined to form an electrical joint and includes the heat-resistant resin powder 12, the distance between the semiconductor device 13 and the circuit board can be maintained within a predetermined range, and short circuit due to excessive crushing can be prevented. be able to. In FIG. 2, 1
4 is a semiconductor element, 15 is a substrate, 16 is a sealing resin, 1
Reference numeral 7 denotes a bonding wire.

Next, a flex bonding material 18 according to a second embodiment of the present invention shown in FIG. 3A will be described. The raw material and composition are the same as those of the flex bonding material 10. In manufacturing, the flex bonding material in a molten state is drawn out into a thread shape and manufactured. The diameter depends on the application, but it is preferable for use to make the diameter about 0.1 to 3 mm. This flex bonding material 18 is used in place of ordinary thread solder (wire solder). by this,
A lead wire can be bonded to an electronic component, or electrodes can be bonded together. The flex bonding material 18 is usually sold and stored in a state wound on a reel 19, and is gradually pulled out for use, for example, as shown in FIG.
As shown in (B), the bump 19b is formed by being melted and dropped on the terminal pad 19a.

Next, a flex bonding material 20 according to a third embodiment of the present invention shown in FIG. 4A will be described.
Is the same as In production, the flex bonding material in a molten state is drawn into a plate shape and rolled to produce. The flex bonding material 20 is made of a thin plate having a rectangular cross section, and is used as a raw material when manufacturing another flex bonding material 10 or 18, or requires a large amount of flex bonding material for bonding a large electronic component. Can be used in case. Further, as shown in FIG. 4B, a small piece 22 punched by a press into a predetermined shape is arranged on the terminal pad 21.
It can also be used as a bump.

In the above embodiment, the heat-resistant resin powder is spherical, but may be short fibrous or irregular. In this case, the surface of the fiber is preferably plated with a good conductor so that it is more evenly dispersed in the solder. In the above embodiment, the raw material of the solder is a low melting point alloy material mainly composed of lead and tin. However, the present invention is applicable to a hard solder mainly composed of tin and a solder using no lead at all. Is done. In addition, in the case of the spherical flex bonding material 10, the melting point of the solder is set higher than that of a normal bonding solder, and the shape of the flex bonding material 10 is not changed by using a solder having a low melting point at the time of bonding. When the electronic components are joined as described above, the flex joining material 10
Exerts an action like a conductive ball with elasticity,
It is possible to manufacture an electronic component that is resistant to thermal stress and strain stress while ensuring the bonding property. In this case, the flex bonding material 1
0 solder has a melting point of 20-
It is preferable to have a melting point at a high temperature of about 100 ° C., or higher in some cases.

In the above embodiment, the use of a flex bonding material for bonding a semiconductor device to a circuit board has been described. However, a semiconductor chip and a substrate such as a PCB, and a semiconductor device formed therefrom are used. It can be applied as a joining member between a board and a motherboard. That is, the flex bonding material according to the embodiment includes SON (small outline non-lead), QON (quad outline non-lead), OL (outer lead), BGA (ball grid array), LGA (land grid array), It can also be used for electrode terminals such as FCBGA (flip chip ball grid array) and FC (flip chip).

[0016]

According to the flex bonding material according to the first to eighth aspects, since the spherical and / or irregularly shaped heat-resistant resin powder having elasticity is evenly dispersed inside the solder, the flexibility is added by sponge theory. Have been. Therefore, when the members to be electrically joined to each other are joined by using this flex joining material, the members can be joined elastically, and the heat deformation of the joined electronic components and substrates, and the deformation due to external pressure can be absorbed,
This can prevent breakage of components and equipment and occurrence of cracks. In particular, in the flex bonding material according to the second aspect, the heat-resistant resin powder is 20 to 60% by volume, and the remainder is mainly composed of a low melting point or a high melting point solder, so that appropriate elasticity and electric conductivity are obtained. Have. The flex bonding material according to the third aspect has a heat-resistant resin powder of 20 to 60% by volume, so that it has an appropriate elasticity and electric conductivity and does not use lead. There is an advantage that there is no problem such as elution and it is not a source of pollution. Claim 4
In the flex bonding material described above, the heat-resistant resin powder is made of one or more of an elastomer resin, a polyimide resin, an epoxy resin, a silicon resin, a urethane resin, a polymer resin, and an acrylic resin. Therefore, the manufactured flex bonding material itself has elasticity. In the flex bonding material according to the fifth aspect, Sn, Ti, In, Pd, Pb-Sn, Au, and A are formed on the surface of the heat-resistant resin powder.
Since the conductive metal thin film layer of g, Ni, or the like is formed, compatibility with the solder is good, and the heat-resistant resin powder can be more evenly dispersed in the solder. The flex bonding material according to claim 6, wherein the shape of the solidified state is 0.05 to
Since it has a 1.5 mm ball shape, it can be used as a terminal for joining electronic components such as semiconductor devices or a substrate. The flex bonding material according to claim 7 can be used in place of ordinary thread solder since the solidified state is a wire having a wire diameter of 0.1 to 3 mm. Since the flex bonding material according to the eighth aspect is a thin plate having a rectangular cross section in a solidified state, it can be used as a material for a flex bonding material having another shape or for bonding a large electronic component.

[Brief description of the drawings]

FIG. 1 is a front view of a flex bonding material according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a bonding state of an electronic component using the flex bonding material.

FIG. 3 is a perspective view of a flex bonding material according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a flex bonding material according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Flex bonding material 11 Solder 12 Heat resistant resin powder 13 Semiconductor device 14 Semiconductor element 15 Substrate 16 Sealing resin 17 Bonding wire 18 Flex bonding material 19 Reel 19a Terminal pad 19b Bump 20 Flex bonding material 21 Terminal pad 22 Small piece

Claims (8)

[Claims] 1. A bonding material which has a shape in a solidified state and is used for connecting members to be electrically bonded, wherein a heat-resistant resin powder having a spherical and / or irregular shape having elasticity is soldered. Flex bonding material characterized by being evenly distributed inside. 2. The flex-joining material according to claim 1, wherein the heat-resistant resin powder is 20 to 60% by volume, and the remainder is mainly composed of low melting point or high melting point solder. 3. The heat-resistant resin powder is 20 to 60% by volume, and the remainder is mainly composed of lead-free solder.
Flex bonding material as described. 4. The heat-resistant resin powder comprises at least one of an elastomer resin, a polyimide resin, an epoxy resin, a silicon resin, a urethane resin, a polymer resin, and an acrylic resin. Item 4. The flex bonding material according to any one of items 1 to 3. 5. The surface of the heat-resistant resin powder, wherein Sn,
Ti, In, Pd, Pb-Sn, Au, Ag, or Ni
The flex bonding material according to any one of claims 1 to 4, wherein a conductive metal thin film layer is formed. 6. The solidified form having an outer diameter of 0.05 to 0.05.
The flex bonding material according to any one of claims 1 to 5, which has a ball shape of 1.5 mm. 7. The solidified shape has a wire diameter of 0.1-3.
The flex bonding material according to any one of claims 1 to 5, wherein the flex bonding material is a wire having a length of 1 mm. 8. The flex bonding material according to claim 1, wherein the solidified shape is a thin plate having a rectangular cross section.