JPH10175064A - Soldering method and solder used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a void on a soldered layer. SOLUTION: In a pellet bonding method, by which a pellet 13 is soldered to a header 11 of a multiple lead frame 1 by a soldering layer 45, a solder 18, in which small holes 17 are pierced to a solder ribbon 16 formed with a Sn-Pb group solder metal layer, is pierced slightly larger than the pellet 13 by a cutter 28. A cut formed solder 20 is loaded on the header 11 by a collet 13. When the formed solder 20 is heated/melted and the pellet 13 is bonded, air and gas between the formed solder 20 and the header 11 is evacuated through the small holes 17, a void is not generated to the soldered layer 45. Accordingly, a void is prevented from generating in the soldered layer, quality reliability of the soldered layer and a product is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering technique, and more particularly, to a soldering technique for soldering an object to be soldered to a base material using a solder material thinly formed of a solder metal as a soldering material. For example, in a manufacturing process of a semiconductor device, a semiconductor pellet (hereinafter, referred to as a pellet).
The present invention relates to a technique effective for utilizing a pellet bonding method for bonding a substrate to a substrate.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device, as a pellet bonding method for fixing a pellet to a substrate,
The following brazing methods may be used: Sn
-Pb-based, Pb-In-based, Au-Sn-based, Au-Ge
Solder ribbon (ribbon), solder foil (foil), solder tape (tape), solder band (band), solder plate (sh)
ee) (hereinafter, referred to as a solder ribbon).
Is formed into a size corresponding to the size of the pellet to be soldered (preform). The molded solder is supplied to the substrate which is a base material, and the pellet is pressed onto the molded solder while being scribed, and the molded solder is heated and melted, so that the pellet is fixed to the substrate via a soldering layer. You.

As an example describing the pellet bonding technique, see Nikkei BP Co., Ltd., May 3, 1993.
One-day “VLSI Packaging Technology (2)” P17
To P22.

[0004]

However, in the above-mentioned pellet bonding method, the molded solder formed by cutting the solder ribbon wound in a reel shape has a warped shape, so that the molded solder is warped. The present inventor has revealed that there is a problem that a sealed space is generated between the base material and air or gas in the sealed space, so that a void is generated in the soldering layer. .

An object of the present invention is to provide a soldering technique capable of preventing the occurrence of voids in a soldering layer.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0007]

The outline of a typical invention among the inventions disclosed in the present application is as follows.

[0008] That is, the present invention is characterized in that an object to be soldered is soldered to a base material using a solder material having small holes formed in a solder material thinly formed of a solder metal.

According to the above-mentioned means, even if a space is formed between the soldering material and the base material, air or gas in the space is exhausted from the small holes, so that a void is generated in the soldering layer. The phenomenon can be prevented.

[0010]

FIG. 1 is a perspective view showing a pellet bonding method according to an embodiment of the present invention. FIG. 2 et seq. Are explanatory diagrams for explaining the operation.

In the present embodiment, the soldering method according to the present invention is used in a pellet bonding step for manufacturing a power transistor (hereinafter, referred to as a power transistor) having a resin-sealed package with a header. The work in the pellet bonding step includes a pellet to be soldered and a multiple lead frame including a header serving as a base material for soldering. First, a multiple lead frame which is a base material side of the soldering method will be briefly described with reference to FIG.

The multiple lead frame 1 is made of a material having good conductivity and heat conductivity, such as an iron-based material such as 42 alloy or a copper-based material (copper or copper alloy) such as oxygen-free copper. By processing, it is integrally formed into a horizontally long rectangular shape or tape shape. The multiple lead frame 1 is formed in a multiple structure in which unit lead frames 2 are repeatedly formed in one direction and connected in a row. Since the same pattern is repeated in the unit lead frame 2, the unit lead frame 2 will be described in principle in the following description.

The unit lead frame 2 has an outer frame (frame) 3 formed in a rectangular plate shape, and the outer frame 3 has a positioning hole 3a. A dam member 4 is arranged in parallel on one side of the outer frame 3, and a first outer lead 5, a second outer lead 6, and a third outer lead 7 are provided between the outer frame 3 and the dam member 4 in the longitudinal direction. Arranged in intervals,
Each is installed in a right angle direction.

A first inner lead 8 and a second inner lead 9 are formed on the dam member 4 so as to be integrally continuous with the first outer lead 5 and the second outer lead 6 located at both left and right ends at positions opposite to the first outer lead 5 and the second outer lead 6. The inner leads 8 and 9 are partially extended in parallel with the dam member 4. Also, a header suspension lead 10 is formed on the dam member 4 so as to be integrally continuous with the third outer lead 7 located at the center on a side opposite to the third outer lead 7, and a pellet is soldered to the header suspension lead 10. A header 11 as a substrate to be formed is integrally formed. Incidentally, the portion between the outer leads 5, 6, and 7 of the dam member 4 constitutes a dam for stopping the resin from flowing out of the cavity during molding of the resin sealing body.

In the multiple lead frame 1, plate members having different thicknesses (so-called deformed members) are used so that the thickness of the header 11 is larger (for example, twice or more) than other portions, and integrated by press working. It is molded. That is,
The header 11 is integrally formed in a substantially square plate shape that is thicker than other portions of the unit lead frame 2. Further, a crank-shaped bent portion 12 is formed in the header suspension lead 10, and the height of the header 11 is higher than the height of the inner leads 8 and 9 by the thickness of the pellet described later, due to the bent portion 12. It has been lowered.

A pellet 13, which is the other work, is manufactured by forming a power transistor element in a state of a semiconductor wafer in a so-called pre-process in a semiconductor device manufacturing process. An adhesive sheet is adhered to the back surface of the semiconductor wafer in which the power transistor elements are formed. The wafer sheet 14 to which the adhesive sheet is adhered is divided into individual pellets 13 in a dicing process. At this time, since the adhesive sheet is stuck, the individual pellets 13 do not fall apart. The wafer sheet 14 divided into the pellets 13 is stretched from an adhesive sheet, and a wafer ring 15 is mounted. In the stretched wafer sheet 14, the adjacent pellets 13, 13 are spaced from each other. Then, in this state, the group of pellets 13 is supplied to the pellet bonding step,
It is set in a pickup device described later.

In the present embodiment, in order to carry out the pellet bonding method, the solder ribbon 16 formed of a Sn-Pb-based solder metal into a ribbon shape having a constant width and a constant thickness is used.
A soldering material 18 in which a number of small holes 17 are opened in the thickness direction is used. Small holes 17 are soldering material 18
Before the solder ribbon 16 is supplied to the pellet bonding step, the solder ribbon 16 is opened. For example, when the solder ribbon 16 is formed by rolling, the small holes 17 are formed simultaneously with the rolling. Alternatively, the small holes 17 may be formed by punching or etching after the solder ribbon 16 is formed. The soldering material 18 is supplied to a pellet bonding step while being wound on a reel 19.

The pellet bonding method according to the present embodiment uses a pellet bonding apparatus 21 shown in FIG. Pellet bonding equipment 21
Is provided with a feeder 22 for feeding the multiple lead frames 1 as a work in one direction (hereinafter, referred to as an X direction), and supplies the multiple lead frames 1 to the feeders 22 at both ends of the feeder 22. 23, and an unloading device 24 for discharging the bonded multiple lead frames 1 from the feeder 22.

On the downstream side of the loading device 23 of the feeder 22, a molding solder supply device 25 for supplying molding solder is provided. The forming solder supplying device 25 is configured to form the forming solder 20 by feeding out the soldering material 18 wound on the reel 19 by a predetermined amount by upper and lower feed rollers and cutting it by a cutter. That is, the reel 19 on which the soldering material 18 has been wound is placed horizontally on one side of the feeder 22, and is set in a direction in which the feed-out direction is orthogonal to the feed direction (X direction) of the feeder 22 (hereinafter referred to as Y direction). The feed ends are upper and lower feed rollers 26, 26 arranged near the feeder 22.
It is inserted between. A pedestal 27 is provided near the feeder 22 between the upper and lower feed rollers 26, 26, and the tip of the soldering material 18 sent out between the upper and lower feed rollers 26, 26 is mounted on the pedestal 27. It has become. The cutter 28 is arranged on the feed roller 26 side of the receiving stand 27, and is configured to shear the tip of the soldering material 18 on the receiving stand 27.

On the opposite side of the feeder 22, a Y table 29 is provided.
And an L-shaped movable base 30 is installed on the Y table 29 so as to be movable in the Y direction. A collet (hereinafter, referred to as a solder collet) 3 for holding the formed solder by vacuum suction is provided at the tip of the moving table 30.
1 is supported to move up and down. The solder collet 31 is configured to vacuum hold the formed solder 20 on the receiving table 27 and to place the held formed solder 20 on the header 11 of the multiple lead frame 1 on the feeder 22.

A put-down device 32 for bonding the pellets to the header is provided on the feeder 22 downstream of the forming solder supply device 25. The put-down device 32 includes a stand 33 on which a bonding head 34 is supported so as to move up and down and rotate. The bonding head 34 is provided with an arm (hereinafter, referred to as a first arm) 35 for bonding the pellet 13 to the header 11.
A collet (hereinafter, referred to as a first collet) 36 for holding the pellet 13 by vacuum suction is attached to the tip of the arm 35.

On the opposite side of the stand 33 of the put-down device 32, a pickup device 37 for picking up the pellets 13 one by one from the wafer sheet 14 is provided. The pickup device 37 has an XY table 38 for moving the wafer ring 15 in the XY directions. Immediately below the XY table 38, a push-up bar 39 for pushing up the pellets 13 adhered to the wafer sheet 14 one by one is provided.
Is provided with a visual observation system 40 for detecting the quality of the image. An arm (hereinafter, referred to as a second arm) 41 of the pickup device 37 is protruded from the bonding head 34, and a collet (hereinafter, referred to as a second collet) for vacuum-holding and holding the pellet is provided at the tip of the second arm 41. ) 42 is attached. An alignment stage 43 is provided on one side of the XY table 38, and the alignment stage 43 is configured to mechanically align the position of the pellet 13 with four blades.

At an intermediate portion of the feeder 22, a heat block (not shown) is laid from a molded solder supply device 25 to an area covering the put down device 32.
The heat block is configured to move up and down with respect to the work transfer path of the feeder 22 so as to be able to contact and separate from the header 11 of the multiple lead frame 1. Although not shown,
A cover is provided outside the heat block so as to surround a heated area of the multiple lead frame 1 with an appropriate margin. A gas supply pipe (not shown) for supplying an inert gas or a reducing gas is connected to the inside of the cover, and the space surrounded by the cover is supplied by the supply of the inert gas or the reducing gas from the gas supply pipe. A non-oxidizing atmosphere is formed.

Next, a pellet bonding method according to an embodiment of the present invention using the pellet bonding apparatus having the above configuration will be described.

In the molded solder supply device 25, the reel 1
The soldering material 18 wound around 9 has feed rollers 26, 2
6 and a predetermined length is placed on the cradle 27. Subsequently, when the cutter 28 is lowered, the soldering material 18 placed on the pedestal 27 is sheared between the pedestal 27 and the feed rollers 26, 26. Due to this shearing, a solder 20 formed by cutting the soldering material 18 is placed on the receiving stand 27. The molded solder 20 is formed into a substantially square foil shape larger than the size of the pellet 13 in plan view. The molded solder 20 on the pedestal 27 is held by vacuum attraction by the solder collet 31, and is conveyed right above the feeder 22.

On the other hand, the multiple lead frames 1 supplied from the loading device 23 to the feeder 22 are stepped forward by one pitch, reach the position of the forming solder supply device 25, and stop intermittently. When the header 11 of the multiple lead frame 1 stops intermittently at the position of the forming solder supply device 25, the soldering collet 31 holding the forming solder 20 is lowered, so that the forming solder 20 is placed on the header 11 as shown in FIG. Relocated as shown.

At this time, since the header 11 is heated by the heat block being raised and abutting on the multiple lead frame 1, the molded solder 20 transferred onto the header 11 is heated and melted. start.

When the intermittent stop period of the step feed operation for the multiple lead frames 1 has elapsed, the heat block is lowered, and the multiple lead frames 1 are stepped by the feeder 22. On the other hand, the solder collet 31 having the molded solder 20 transferred to the header 11 returns to the position of the receiving stand 27 of the molded solder supply device 25, receives the next molded solder 20 formed on the receiving stand 27, and Wait for the supply operation.

On the other hand, in the pickup device 37, based on the observation of the visual observation system 40, the XY table 38 positions the non-defective pellet 13 on the wafer sheet 14 right above the push-up bar 39. The push-up bar 39 pushes up the wafer sheet 14 from below to push up the good-quality pellet 13. The pushed up pellet 13 is the second collet 4
The wafer 2 is held by vacuum suction, transported to the alignment stage 43 by the second arm 41, and transferred to the alignment stage 43. In the alignment stage 43, the pellet 13 is aligned by four blades.

The first collet 36 of the put-down device 32
Picks up the aligned pellets 13 from the alignment stage 43 and conveys them to a put-down stage set on the feeder 22 by the first arm 35. On the other hand, the second collet 42 on which the pellets 13 have been transferred to the alignment stage 43 returns just above the wafer sheet 14 of the pickup device 37, and the next pellet 1
3 and waits for the next operation.

When the header 11 is intermittently stopped at the position of the put-down device 32 with the step-by-step feed to the multiple lead frames 1, the heat block rises and heats the header 11. By this heating, the molded solder 2 on the header 11
0 melts. The molten solder 44 spreads on the header 11 as shown in FIG.

The first collet 36 of the put-down device 32
Is lowered, and the pellet 13 held by vacuum suction is transferred to the header 11.
Is pressed onto and adhered to the molten solder 44 which has been melted and spread. At this time, as shown in FIG. 2, the molten solder 44 has a slightly larger planar shape than the planar shape of the pellet 13 and a uniform thickness over the whole, so that the pellet 13 does not tilt. The solder 11 is adhered to the header 11 by a soldering layer 45 composed of a molten solder 44 in parallel exactly.

When the intermittent stop period of the stepping operation for the multiple lead frames 1 has elapsed, the heat block is lowered. The first collet 36 emptied by bonding the pellet 13 to the header 11 is transferred to the alignment stage 43 by the first arm 35. And the first collet 3
After picking up the next pellet 13, 6 is transferred to the put down stage of the put down device 32 and waits for the next bonding operation.

By simultaneously performing the above operations, the forming solder supply step, the pickup step, and the put-down step are performed for each unit lead frame 2 as the multiple lead frames 1 are advanced. ,
The pellet 13 is soldered to the header 11 as a base material.
5, and the bonding is performed.

By the way, the formed solder formed by cutting the solder ribbon wound in a reel shape has a warped shape as shown in FIG. When the warped shaped solder 20A is placed on the header 11 in a prone state as shown in FIG. 3 (b), a space is created between the opposing surfaces of the shaped solder 20A and the header 11 and oxidation occurs. The prevention gas 46 is confined. When the molded solder 20A containing the antioxidant gas 46 is heated and melted on the header 11, the antioxidant gas 46 remains trapped in the molten solder 44A as shown in FIG. become.
Therefore, as shown in FIG. 3D, the inside of the soldering layer 45A in which the pellet 13 is adhered to the header 11 is filled with the void 47 by the trapped antioxidant gas.
Is generated.

However, in the present embodiment, since the molding solder 20 is formed by cutting the soldering material 18 having the small holes 17 formed in the solder ribbon 16, the pellets 13 are formed in the header 11 without voids. The state of bonding by the layer 45 is obtained.

That is, when the soldering material 18 wound on the reel 19 is cut and formed, the formed solder 20 has a warped shape as shown in FIG. As shown in (f), the warped molded solder 20 is placed on the header 11 in a prone state, and a space is generated between the opposing surfaces of the molded solder 20 and the header 11, and the antioxidant gas 46 is generated. Even if trapped, molded solder 20
Since the small hole 17 is opened in the, the oxidation preventing gas 46 trapped from the small hole 17 is discharged. Therefore, as shown in FIG. 3G, the occurrence of voids in the molten solder 44 is prevented. As a result, FIG.
As shown in (h), the pellet 13 is the header 1
1 is bonded by the soldering layer 45 without voids.

According to the above embodiment, the following effects can be obtained. Cut the soldering material with small holes in the solder ribbon thinly formed by the solder metal to form the molded solder,
By soldering the pellets to the header using this molded solder, even if a space is created between the molded solder and the header, the air and gas in this space can be exhausted from the small holes. The phenomenon that voids are generated in the attachment layer can be prevented.

By preventing the occurrence of voids in the soldering layer, it is possible to prevent the occurrence of adhesive strength of the soldering layer and to reduce the mechanical strength of the soldering layer. Can be fixed to the
The quality and reliability of the power transistor can be improved.

By preparing a soldering member having small holes in advance, it is possible to avoid an increase in the number of steps in performing the pellet bonding step, and thus to prevent an increase in the operation time of the pellet bonding step. be able to.

FIG. 4 is a partially cut-away side view showing a molded solder supply device used in a pellet bonding method according to another embodiment of the present invention.

The second embodiment differs from the first embodiment in that a hole punching device 50 is interposed in the molded solder supply device 25. That is, the punching device 50 includes a plurality of punching pins 51, and the punching pins 51 are arranged right above the receiving base 27 and are driven up and down by the cylinder device 52.

In the second embodiment, the soldering material 18 supplied to the receiving stand 27 is pierced by the piercing pins 51 to open a plurality of small holes 17. Therefore, since the molded solder 20 having the small holes 17 is supplied to the header 11, the same operation and effect as those of the first embodiment can be obtained.

FIGS. 5A and 5B show a molded solder supplying apparatus used in a pellet bonding method according to another embodiment of the present invention. FIG. 5A is a partially cut side view, and FIGS. It is each enlarged partial sectional view for demonstrating an effect | action.

The third embodiment is different from the first embodiment in that the soldering material having the small holes is used instead of the soldering material having the small holes.
No. 9 molding solder 2 with no small holes
OB is configured to be supplied in a state of being turned upside down.

In the third embodiment, the solder ribbon 16 wound on the reel 19 is
, And is sheared by the cutter 28, so that the peripheral part of the molded solder 20B sheared by the cutter 28 is lifted. In this state, the molded solder 20B
5B is transferred to the header 11 as shown in FIG. 5B, a sealed space is not formed between the contact surfaces of the molded solder 20B and the header 11, and therefore, as shown in FIG. As shown, the pellet 13 is bonded to the header 11 by the void-free soldering layer 45.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the embodiment, and various changes can be made without departing from the gist of the invention. Needless to say.

For example, the drilling method is not limited to a mechanical method, and a drilling method using laser irradiation or the like may be used.

In the above description, the case where the invention made by the inventor is mainly applied to the method of pellet bonding of a power transistor, which is the background of the application, has been described. However, the present invention is not limited to this. The present invention can be applied to a whole method of soldering such as a method of pellet bonding of a circuit device (IC) and a method of soldering another electronic component.

[0050]

The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.

A solder material having a small hole is cut from a solder material thinly formed by a solder metal to form a formed solder, and an object to be soldered is soldered to the base material using the formed solder. Thus, even if a space is formed between the molded solder and the base material, the air and gas in this space can be exhausted from the small holes, thereby preventing a phenomenon that voids are generated in the soldering layer. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a pellet bonding method according to an embodiment of the present invention.

FIGS. 2A and 2B show a multiple lead frame, in which FIG. 2A is a partially omitted plan view, FIG. 2B is a view taken along the line bb of FIG.
Is a partially omitted front view.

FIG. 3 is an explanatory diagram for explaining the operation.

FIG. 4 is a partially cut-away side view showing a molded solder supply device used in a pellet bonding method according to another embodiment of the present invention.

FIG. 5 shows a molded solder supply device used in a pellet bonding method according to another embodiment of the present invention;
(A) is a partially cut-away side view, and (b) and (c) are enlarged partial cross-sectional views for explaining the operation.

[Explanation of symbols]

1 ... multiple lead frame, 2 ... unit lead frame, 3
... outer frame (frame), 4 ... dam member, 5 ... first outer lead, 6 ... second outer lead, 7 ... third outer lead,
8: first inner lead, 9: second inner lead, 10 ...
Header suspension lead, 11: header (base material), 12: bent portion, 13: pellet (soldering target), 14: wafer sheet, 15: wafer ring, 16: solder ribbon (solder material), 17: small hole , 18: soldering material, 19: reel, 20, 20A, 20B: molded solder, 21: pellet bonding device, 22: feeder, 23: loading device, 24: unloading device, 25: molded solder supply device, 26: Feed roller, 27 ... Cradle, 28 ... Cutter, 29 ... Y table, 30 ... Movable table, 31 ... Collet for solder, 32 ... Put down device, 33 ... Stand,
34 ... bonding head, 35 ... first arm, 36 ...
1st collet, 37 ... pickup device, 38 ... XY table, 39 ... push-up bar, 40 ... visual observation system, 41 ...
Second arm, 42 second collet, 43 alignment stage, 44 molten solder, 45 soldering layer, 46
Antioxidant gas, 47: void, 50: drilling device, 5
1 ... Punching pin, 52 ... Cylinder device.

Claims (5)

[Claims] 1. A soldering method for soldering an object to be soldered to a base material using a solder material thinly formed of a solder metal as a soldering material, wherein a small hole is formed in the solder material of the soldering material. A soldering method characterized by being opened in the thickness direction. 2. The soldering material in which the small holes are opened in advance is formed into a molded solder having a size corresponding to the soldering object and supplied to the base material, and the solder is placed on the molded solder. The soldering method according to claim 1, wherein an object to be attached is supplied and soldered to the base material. 3. The soldering material is formed by opening the small hole in the solder material during the soldering, and the soldering material is formed into a molded solder having a size corresponding to the soldering object. The soldering method according to claim 1, wherein the soldering object is supplied to the base material, and the object to be soldered is supplied on the formed solder and soldered to the base material. 4. A soldering method for soldering an object to be soldered to a base material using a solder material thinly formed of a solder metal as a soldering material, wherein the soldering material is the object to be soldered. In the soldering method, the molded solder is formed into a molded solder having a size corresponding to and supplied to the base material, and the object to be soldered is supplied on the molded solder and soldered to the base material. Is supplied to the base material in a state where the peripheral portion is warped so as to be separated from the upper surface of the base material. 5. A soldering material characterized in that small holes are formed in a thickness direction in a solder material thinly formed of a solder metal.