JP3075864B2 - Wire bonding method using solder wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing various electronic components, for example, in the case of performing wire bonding between a semiconductor chip and its lead terminals or circuit patterns using a metal wire. The present invention relates to a wire bonding method using a solder wire.

[0002]

2. Description of the Related Art Conventionally, it has been very common to use a gold wire for this kind of wire bonding. However, a gold wire is very expensive and the cost is greatly increased.
Therefore, a solder wire is used instead of the gold wire. The features of using a solder wire are that the cost can be sufficiently reduced, and that the solder wire has a function as a safety fuse against temperature or overcurrent, and a function as a complete fuse against temperature and overcurrent. Can be

In wire bonding, a gold wire is inserted into a capillary tool, and a ball is formed at the end of the wire by heating and melting, and the ball is pressed against a work such as a semiconductor chip. When a solder wire is used instead of the gold wire, an extremely thick oxide film must be formed on the surface of the ball when the ball is formed by heating and melting. Therefore, a situation occurs in which it cannot be joined to a work such as a semiconductor chip.

In view of the above, the inventor of the present invention has proposed that, in an earlier patent application (Japanese Patent Application No. 4-38141), an oxygen gas and a hydrogen gas are mixed in a middle of a solder wire inserted into a capillary tool in an inert gas atmosphere. By heating and melting with an oxyhydrogen flame composed of a mixed gas of the above, balls are formed at both ends of the cut at the same time as cutting, and both ball portions are pressed against a work such as a semiconductor chip. We proposed a ball-and-ball type wire bonding method using solder wires to be joined.

[0005]

However, the method according to the invention of the prior application cuts the middle of the solder wire by heating and melting it with an oxyhydrogen flame in an atmosphere of an inert gas, and at the same time cutting the solder wire. A ball portion is formed at both ends. When heating and melting the solder wire by the oxyhydrogen flame, it is generated by an excess oxygen gas in the oxyhydrogen flame and a combustion reaction between oxygen gas and hydrogen gas. Because of the water vapor, an oxide film is generated on the surface of the ball. In other words, an oxide film is generated on the surface of the ball despite the formation of the ball in an inert gas atmosphere. However, the reliability of bonding to a work such as a semiconductor chip and the strength of bonding are still insufficient.

Further, the temperature of the oxyhydrogen flame is about 30.
Since the temperature is much higher than the melting temperature (about 300 ° C.) of the solder, such as 00 ° C., the diameter of the ball changes greatly depending on the state of the oxyhydrogen flame. Also, there is a problem in that it is very difficult to control to make the diameters uniform.

According to the present invention, in the ball-ball type wire bonding using a solder wire, it is possible to greatly improve the reliability of bonding to a work and the strength of bonding, and to make the diameter of a ball portion a predetermined size. Another object of the present invention is to provide a method capable of easily making the diameters uniform.

[0008]

In order to achieve this technical object, the present invention provides an inert gas atmosphere in the vicinity of a work such as a lead frame or a semiconductor chip and the vicinity of a capillary tool through which a solder wire is inserted. At the same time, the middle of the solder wire pulled out of the capillary tool is blown by blowing an inert gas heated to a high temperature, and at the same time, ball portions are formed at both ends of the blow. It is characterized by being pressed and joined to a workpiece such as.

[0009]

[Operation] When a solder wire is blown in the middle and ball portions are formed at both ends of the solder wire, an inert gas heated to a high temperature is sprayed on the solder wire in an inert gas atmosphere as described above. By fusing,
A ball portion can be formed at each of both ends of the fusing in a state where an oxide film generated on the surface of the ball portion is significantly reduced.

[0010]

As described above, according to the present invention, at the time of ball-ball type wire bonding using a solder wire, an oxide film generated on the surface of the ball portion formed on the solder wire can be reduced. Alternatively, the reliability of bonding to a work such as a semiconductor chip and the strength of bonding can be greatly increased, and the effect of reliably reducing the occurrence of wire bonding mistakes at the time of wire bonding with solder wires can be obtained.

Moreover, since the temperature of the solder wire can be easily controlled by blowing the solder wire by blowing a high-temperature inert gas, the variation in the diameter of the ball portion can be reduced, and the diameter of the ball portion can be reduced. There is also an effect that can be set arbitrarily.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given of an embodiment of the present invention in which a safety fuse is provided by wire bonding using a solder wire in a tantalum electrolytic capacitor having a safety fuse against temperature or overcurrent. As shown in FIG. 8, the tantalum electrolytic capacitor 1 has an anode terminal 3 protruding from a capacitor element 2 fixed to one of a pair of left and right lead terminals 4 and 5, while the capacitor element 2 2 and the other lead terminal 5 are wire-bonded with a safety fuse 6 made of solder wire, and the whole of them is packaged in a mold part 7 made of a thermosetting synthetic resin. , 5 in the mold section 7
Along the rear side.

1 to 7, reference numeral 10 denotes a pair of lead terminals 4 of the tantalum electrolytic capacitor 1.
5 shows a lead frame integrally formed at an appropriate pitch along the longitudinal direction.
The anode terminal 3 provided with the capacitor element 2 is fixed to each one of the lead terminals 4, and the lead frame 10 is arranged in the longitudinal direction of the lead terminal 4 as shown by an arrow A. , 5 intermittently.

Reference numeral 11 denotes a machine stand (not shown).
1 shows a heater block disposed so as to extend along the longitudinal direction of the lead frame 10, and a heater (not shown) for heating the lead frame 10 to an appropriate temperature is provided inside the heater block 11. And
A cover plate 12 having an opening 13 for wire bonding at substantially the center is attached to the upper surface of the heater floc 11.

A tunnel portion 14 through which the lead frame 10 passes is formed between the upper surface of the heater block 11 and the cover plate 12, while the cover plate 12 supplies an inert gas into the tunnel portion 14. By connecting a pipe 15 and supplying an inert gas such as a nitrogen gas or an argon gas into the tunnel portion 14 from the inert gas supply pipe 15, the inert gas is blown out from the opening 13. In a box 16 surrounding the opening 13,
A space between the capacitor element 3 fixed to one lead terminal 4 of the lead frame 10 and the other lead terminal 5 is connected by a solder wire forming a safety fuse 6.
It is configured to perform wire bonding.

The wire bonding using the solder wires is performed as shown in FIGS. That is, a vertically movable capillary tool 17 is disposed just above the other lead terminal 5 in the lead frame 10, and a lower end of a solder wire 18 inserted into the capillary tool 17 is provided as shown in FIG. To
When the ball portion 18a is formed, the capillary tool 17 is moved downward toward the other lead terminal 5 to press and join the ball portion 18a against the other lead terminal 5, as shown in FIG. It moves up afterwards.

Next, an inert gas heated to a temperature of, for example, 800 to 1000 ° C. by a heating means (not shown) is blown from a nozzle 19 to a portion of the solder wire 18 protruding from the capillary tool 17, whereby 6 and FIG. 7, the solder wire 1
8 is blown into the solder wire 18 and the solder wire piece 18 ′ joined to the other lead terminal 5, so that the ball portion 18 a is attached to the lower end of the solder wire 18 by the solder blow. A ball portion 18b can be formed at the tip of the wire 18 '.

Then, the solder wire piece 18 'joined to the other lead terminal 5 is moved forward by the bending tool 20 reciprocating in a substantially horizontal direction, so that the ball portion 18b at the tip of the solder wire piece 18' is moved forward. Is bent so as to abut against the capacitor element 3, and then the ball portion 18b at the tip of the solder wire piece 18 'is bent.
Is pressed against and joined to the capacitor element 3 by the downward movement of the vertically movable pressing tool 21, thereby completing the wire bonding.

At the time of this wire bonding, the vicinity of the capillary tool 17 and the vicinity of the solder wire 18 inserted therethrough are kept in an inert gas atmosphere by an inert gas blown out from the opening 13, while the solder wire By blowing an inert gas heated to a higher temperature from the nozzle 19 to the solder wire 18, an oxide film is generated on the surfaces of the ball portions 18 a and 18 b formed at both ends of the blow. Can be reliably reduced.
The reliability of the bonding of the a and 18b to the other lead terminal 5 and the capacitor element 3 and the bonding strength can be greatly increased.

Each of the tantalum electrolytic capacitors for which wire bonding has been completed as described above is packaged in a synthetic resin mold part 7 and then separated from the lead frame 10. The terminals 4 and 5 are bent along the mold part 7 to obtain a finished product. In the above-described embodiment, the case where the safety fuse 6 is provided by wire bonding using a solder wire in the tantalum electrolytic capacitor 1 is shown. However, the present invention is not limited to this, and other electronic components may be used. It goes without saying that the present invention can also be applied to a case where wire bonding is performed using a solder wire.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged sectional view taken along line III-III of FIG. 1;

FIG. 4 is a perspective view showing a first state of wire bonding according to the embodiment of the present invention.

FIG. 5 is a perspective view showing a second state of the wire bonding according to the embodiment of the present invention.

FIG. 6 is a perspective view showing a third state of the wire bonding according to the embodiment of the present invention.

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 6;

FIG. 8 is a vertical sectional front view of the tantalum electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tantalum electrolytic capacitor 2 Capacitor element 3 Anode terminal 4, 5 Lead terminal 6 Safety fuse 7 Mold part 10 Lead frame 11 Heater block 12 Cover plate 13 Opening hole for spouting inert gas 14 Tunnel part 15 Inactive gas supply pipeline 16 Box 17 Capillary tool 18 Solder wire 18 'Solder wire piece 18a, 18b Ball portion 19 High-temperature inert gas jet nozzle

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-61-253824 (JP, A) JP-A-49-88077 (JP, A) JP-A-4-165635 (JP, A) JP-A-59-880 40540 (JP, A) JP-A-4-237139 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/60 301

Claims (1)

(57) [Claims] An inert gas atmosphere is provided around a work such as a lead frame or a semiconductor chip and a capillary tool through which a solder wire is inserted. Solder characterized by being blown with active gas and simultaneously forming ball portions at both ends of the blow, and pressing and joining both ball portions to a work such as a lead frame or a semiconductor chip. Wire bonding method using wires.