JPH0477463B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to connection of thin lead wires to electrodes formed on lead frames of semiconductor devices, semiconductor elements fixed on lead frames, or electrodes on circuit boards. The present invention relates to a wire bonding method using ultrasonic waves suitable for.

[Conventional technology]

Wire bonding using ultrasonic vibration is well known, and is also used, for example, in manufacturing a resin-sealed power transistor shown in FIG. The lead frame assembly 1 shown in FIG. 4 consists of a lead frame 2, a power transistor chip 3, and a thin lead wire 4. The lead frame assembly 1 shown in FIG. The lead frame 2 is connected to a support plate 5, an external lead 6 disposed at one end of the support plate 5, a tie bar 7 connecting the external leads 6 in parallel, a first connecting strip 8, and the other end of the support plate 5. The positioning lead 9 and the second positioning lead 9 that connects the positioning lead 9 in parallel.
It consists of 10 connecting strips. As shown in the figure, the lead frame 2 is a multi-element lead frame in which a plurality of support plates 5 are connected in parallel.

When manufacturing the lead frame assembly 1, the power transistor chip 3 is fixed on the support plate 5 of the lead frame 2, and then the electrodes on the power transistor chip 3 and the external leads 6, that is, the external connection electrodes are connected with thin lead wires. Connect with 4. Here, fixing of the power transistor chip 3 and connection of the thin lead wires 4 are performed by well-known die bonding and wire bonding, respectively. Thereafter, a resin sealing body 15 is formed on the lead frame assembly 1 by well-known transfer molding, and after performing a predetermined process, the tie bar 7, the first and second connecting strips 8, 10, and the positioning lead 9 are formed. By cutting and removing the resin-sealed transistors, individualized resin-sealed transistors are obtained.

The bonding device for connecting thin lead wires 4 using ultrasonic vibration shown in FIG.
, a fixing jig 14, a drive device 14a for the fixing jig 14, a guide pin 11, and a drive device 11a for the guide pin 11. During wire bonding, a thin lead wire 4 is drawn out from a capillary 12, and the thin lead wire 4 is pressed against the electrode of the transistor chip 3 by the capillary 12, and ultrasonic vibration is applied to the capillary 12 in a direction parallel to the surface of the electrode. That is, the thin lead wire 4 is pressed against the electrode and rubbed together to connect. When wire bonding is performed on the external leads 6 of the lead frame 2, the lead frame 2 is placed on the mounting table 13, and the fixing jig 14 is used to press the lead frame 2 at a predetermined position.

[Problem that the invention seeks to solve]

By the way, wire bonding using this ultrasonic vibration method has the following problems.

The thin lead wire 4 is the electrode to be connected (in Fig. 5,
When the capillary 12 is pressed against the electrode (on the power transistor chip 3), the ultrasonic vibration of the capillary 12 is applied to the lead frame 2 through the connecting portion. Due to this vibration, the lead frame 2 slides on the mounting table 13 in the direction of the vibration, albeit slightly. When this sliding occurs, sufficient ultrasonic vibration is not applied to the connecting portion (wire bonding portion) of the thin lead wire 4, resulting in insufficient connection. This kind of problem occurs because the fixing location of the lead frame 2 by the fixing jig 14 is far from the wire bonding part, so the inventor provided a large number of fixing jigs 14 to fix the lead frame 2 at multiple locations. I tried a method to fix it. However, it has not been possible to sufficiently fix the lead frame 2 by providing a large number of fixing points so as not to interfere with the movement of the capillary 12.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method that can perform good wire bonding without reducing the degree of freedom of the capillary.

[Means for solving problems]

In order to solve the above problems and achieve the above objects, the present invention connects a thin lead wire to an electrode included in an assembly consisting of a support and an electronic element and/or circuit board fixed to the support. At this time, the assembly is placed on a mounting table, and the thin lead wire is placed against the electrode while ultrasonic vibration is applied to the capillary feeding out the thin lead wire in a direction substantially parallel to the surface of the electrode. In the wire bonding method using ultrasonic waves in which connection is performed by pressing with Provide an uneven surface in advance,
The present invention relates to a wire bonding method characterized in that the uneven surface of the support body and the uneven surface of the mounting table are engaged with each other when the thin lead wire is connected to the electrode using the ultrasonic vibration.

[Effect]

The support body in the above invention is, for example, a lead frame or something similar thereto, and supports an electronic element and/or a circuit board. By meshing the uneven surface of the support with the uneven surface of the mounting table, sliding of the support during wire bonding is suppressed, and the contact state of the lower region of the wire bonding part of the support with the mounting table is improved. The thin lead wire can achieve good bonding. Note that the present invention can also be applied to ultrasonic wire bonding combined with thermocompression bonding.

〔Example〕

Next, a method for manufacturing a resin-sealed power transistor according to an embodiment of the present invention will be described. However, in FIGS. 1 to 3, the symbols 1 to 14 and 8a, 11a,
Since the parts indicated by 12a and 14a are substantially the same as the parts indicated by the same reference numerals in FIGS. 4 and 5, their explanation will be omitted.

The difference between FIGS. 1 to 3 from FIGS. 4 and 5 is that the back surface of the support plate 5 has an uneven surface 16 as shown in FIG. The surface of the mounting table 13a also has an uneven surface 17. Each uneven surface 16, 17 is an external lead 6
It is formed by providing grooves 18 and 19, respectively, so as to extend in the same direction. Support plate 5
The depth of the grooves 18 in the uneven surface 16 is desirably 20 to 250 μm, which is 1/8 or less of the thickness (about 2 mm) of the support plate 5, and more preferably 70 to 150 μm.

The mounting table 13 has a first portion 13a on which the support plate 5, positioning leads 9 and connecting strips 10 are placed, and a second portion 13 on which the external leads 6 and connecting strips 8 are placed.
b, and is configured such that the second portion 13b can be moved relative to the first portion 13a.

The first portion 13a is provided with a first mounting surface 20 on which the support plate 5 is mounted, a second mounting surface 21 on which the positioning lead 9 and the connecting strip 10 are mounted, and a second mounting surface 21 on which the positioning lead 9 and the connecting strip 10 are mounted. An inclined surface 22 is provided at the boundary between the first and second mounting surfaces 20 and 21. That is, the upper surface of the first portion 13a is adjusted so as to correspond to the stepped portion 23 and the lower surface of the supporting plate 5 and the lower surface of the positioning lead 9, which are caused because the thickness of the supporting plate 5 is larger than that of the positioning lead 9. is formed. Furthermore, the first part 13a has a projection 24 for preventing the connecting strip 10 from shifting to the right.

The second part 13b has an upper surface 25 on which the external leads 6 and the connecting strips 8 rest. Between this upper surface 25 and the first mounting surface 20 of the first portion 13a, there is a step corresponding to the step between the support plate 5 and the external lead 6. The protrusion 26 of the second portion 13b is formed to prevent the connecting strip 8 from shifting to the left. Note that the second mounting surface 2 of the first portion 13a
The upper surfaces 25 of the first and second portions 13b are substantially mirror surfaces that are smoother than the first mounting surface 20.

When performing wire bonding, the lead frame assembly 1 is prepared in the same manner as described in FIGS. 4 and 5, and the lead frame 2 is arranged so that the lower surface side thereof is fitted onto the mounting table 13. At this time, the uneven surface 16 of the support plate 5 is engaged with the first mounting surface 20, that is, the uneven surface 17 of the first portion 13a. Further, the wide part of the external lead 6 connected to the support plate 5 is held down by the fixing jig 14, as in the conventional example.

Next, as in the conventional example, ultrasonic vibration is applied to the capillary 12 to connect one end of the thin lead wire 4 to the electrode on the power transistor chip 3 and the other end to the external lead 6. At this time, the direction of the ultrasonic vibration of the capillary 12 is parallel to the surface of the electrode, and the direction of the arrow 28 in FIG. do. During wire bonding using this ultrasonic vibration method, the lead frame 2 tries to slide in the direction of the ultrasonic vibration of the capillary 12 as in the conventional example, but the uneven surface 16 of the support plate 5 and the uneven surface 17 of the mounting table 13a are in mesh with each other, so the lead frame 2 will not slide. Therefore, incomplete connection of the thin lead wire 4 can be prevented. Moreover, since the fixing jig 14 does not contact the support plate 5 but only contacts the external lead 6, it does not interfere with the movement of the capillary 12.

When performing wire bonding to the next transistor chip 3 on the support plate 5, the lead frame 2 is unfixed by the fixing jig 14, and the second portion 1
3b upwardly to lift the lead frame assembly 1, lifting the support plate 5 from the first portion 13a and moving the lead frame assembly 1 in this longitudinal direction, that is, in the direction of juxtaposition of the external leads 6 (arrow 2).
8) to position the support plate 5 to be wire bonded under the capillary 12.
To move the lead frame assembly 1 in the direction of the arrow 28, the guide pin 11 is inserted into the guide pin insertion hole 8a of the connecting strip 8, and the guide pin driving device 1 is moved.
This is achieved by moving the guide pin 11 in the direction of the arrow 28 by means of the arrow 1a. A pair of protrusions 2
4 and 26 is somewhat larger than the width of the lead frame 2, the protrusions 24 and 26 do not impede movement of the lead frame 2. After wire bonding, the same resin sealing body 15 as shown in FIG. 4 is provided to form individual resin sealing transistors as in the conventional example.

This embodiment has the following advantages.

(1) Since the uneven surface 16 of the support plate 5 and the uneven surface 17 of the first portion 13a are engaged with each other, the sliding of the support plate 5, that is, the lead frame 2 during ultrasonic vibration is restricted, and the support plate 5 is It is stably supported by the stand 13. Therefore, ultrasonic wire bonding can be performed satisfactorily without significantly changing the existing lead frame and automatic wire bonder.

(2) Since it is not necessary to fix the support plate 5 with a fixing jig, wire bonding using the capillary 12 can be performed without being hindered by the fixing jig.

(3) Even though the uneven surfaces 16 and 17 are provided, the lead frame assembly 1 is moved by moving the second portion 13b upward and lifting one uneven surface 16 from the other uneven surface 17. This movement can be achieved smoothly. That is,
The substantially mirror-finished back surface of the external lead 6 is connected to the mirror-finished upper surface 25 of the second portion 13b.
Slide the lead frame 2 in the direction of arrow 2.
Since it moves in the direction of 8, this movement is achieved smoothly.

(4) The uneven surface 16 on the back surface of the support plate 5 can be easily formed by coining during a series of press operations for forming the lead frame 2. Therefore, an increase in the cost of the lead frame 2 can be suppressed.

(5) The uneven surface 16 on the back surface of the support plate 5 additionally has the known effect of increasing the adhesion with the resin sealing body 15 provided as shown in FIG. In addition, when forming the resin sealing body 15 by injecting the sealing resin from the second connecting strip 10 side during well-known transfer molding, the uneven surface 16 of this embodiment
The direction in which the grooves 18 extend substantially coincides with the flow direction of the resin. Thereby, the flow of the resin can be improved, and the resin sealing body 15 can be formed stably and favorably.

(6) The upper surface of the mounting table 13 has a step corresponding to the step on the lower surface of the lead frame 2, and substantially the entire lower surface of the lead frame 2 is formed so as to be in contact with the mounting table 13, and the protruding portion 24, 26, the movement of the external leads 6 of the lead frame 2 in the extending direction can be effectively suppressed.

[Modified example]

The present invention is not limited to the above-described embodiments, but can be modified, for example, as follows.

(1) The direction in which the grooves 18 and 19 forming the uneven surfaces 16 and 17 extend is the direction in which the external leads 6 are juxtaposed, that is, the second direction.
It may also be in the direction of arrow 28 in the figure. In this case, it is desirable that the direction of ultrasonic vibration of the capillary 12 be perpendicular to the arrow 28 in FIG.

(2) The uneven surfaces 16 and 17 may be rough surfaces other than those based on the grooves 18 and 19, such as a matte surface, a corrugated surface, a surface dotted with convex portions or concave portions, and the like. However, it is necessary to form it so that it has a component in a direction substantially perpendicular to the direction of ultrasonic vibration of the capillary 12. In addition, in the case of a pear-shaped surface, the height of the protrusion forming the pear-shaped surface should be 5 μm or more, preferably 10 μm.
It is desirable to do more than that. In addition, the uneven surface 1
The cross-sectional shapes of 6 and 17 may be triangular, rectangular, semicircular, or the like. Furthermore, the pitch of the grooves 18 on the uneven surface 16 and the pitch of the grooves 19 on the uneven surface 17 may not be made to match, but may be integer multiples.
Further, the roughness of the rough surface such as a matte surface may be made different between the lower surface of the support plate 5 and the upper surface of the first portion 13a.

(3) The mounting table 13 may be divided into three parts, for example, and only the lower part of the support plate 5 may be moved up and down.

(4) Various thin wires such as Au wire and Al wire can be used as the lead thin wire 4. It is also applicable to wire bonding (ball bonding, stitch bonding, etc.) that uses a combination of thermocompression bonding and ultrasonic vibration.

(5) Without moving the fixing jig 14, place it on the mounting table 13.
The lead frame 2 may be fixed and released by moving up and down.

(6) The engagement of the uneven surfaces 16 and 17 may not be the engagement of a plurality of concave portions and a convex portion, but may be the engagement of a single concave portion and a convex portion. That is, the back surface of the support plate 5 and the mounting table 1
One recess is provided on one side of the upper surface of 3, and one recess is provided on the other side.
Two convex portions may be provided and these may be engaged with each other.

(7) The back surfaces of the external leads 6 and positioning leads 9 may also be made rough.

〔Effect of the invention〕

As described above, according to the present invention, highly reliable wire bonding can be easily achieved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a lead frame assembly and bonding device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line -- in FIG. 1, and FIG. 3 is a plan view of the mounting table in FIG. 1. FIG. 4 is a plan view of the lead frame assembly, and FIG. 5 is a cross-sectional view of the conventional lead frame assembly and bonding device taken along the line - in FIG. 4. DESCRIPTION OF SYMBOLS 1... Lead frame assembly, 2... Lead frame, 3... Transistor chip, 4... Thin lead wire, 5... Support plate, 6... External lead, 12
... Capillary, 13 ... Mounting table, 14 ... Fixing jig, 16, 17 ... Uneven surface.

Claims (1)

[Claims] 1. When connecting thin lead wires to electrodes included in an assembly consisting of a support and an electronic element and/or circuit board fixed to the support, the assembly is placed on a mounting table. , an ultrasonic wire that connects the thin lead wire by pressing the thin lead wire against the electrode with the capillary while applying ultrasonic vibration in a direction substantially parallel to the surface of the electrode to the capillary feeding out the thin lead wire; In the bonding method, an uneven surface is provided in advance on at least a part of the surface of the support that is in contact with the mounting table, the mounting table is also provided with an uneven surface that engages with the uneven surface of the support, and the ultrasonic vibration is applied. A wire bonding method characterized in that the uneven surface of the support body and the uneven surface of the mounting table are engaged with each other when the thin lead wire is connected to the electrode. 2. The wire bonding method according to claim 1, wherein the support body is a lead frame having a support plate to which the electronic element and/or circuit board is fixed, and an external lead connected to the support plate. 3. The uneven surfaces of the support body and the mounting table are surfaces formed by providing grooves extending in a direction intersecting the vibration direction of the capillary, respectively. Wire bonding method described.