JPH03116842A - Bonding and device therefor - Google Patents

Abstract

PURPOSE:To remove a treatment applied on the surface of a material to be bonded and to improve the bondability of the material to be bonded by a method wherein before a bonding is performed on the material to be bonded with the treatment applied on its surface, the material to be bonded is heated in a non-oxidizing atmosphere. CONSTITUTION:A multi-column lead frame 3 with a rust preventive film 3b applied on its surface is fed to a rust preventive removing stage 50 installed on a guide table 7 of a loading device by the loading device installed at the upstream end of a feeder 6. Reducing gas 52 is blown off on this stage 50 from a group of blow-off ports 54 by a gas feed unit 56 through a feed passage 55 and an atmospheric gas containing the reducing gas is formed. This reducing gas 52 is heated by a heat block 51 in the most effective temperature range. When the lead frame 3 is fed in an atmosphere containing this gas 52, the film 3b is decomposed and removed and the multi-column lead frame 3 is fed in order to a pellet bonding stage 30.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to bonding technology, particularly to technology for improving the bondability of objects to be bonded. The present invention relates to a bonding device that is effective for use in a bonding device that performs bonding and electrically connects the pellet to each lead of a lead frame.

[Conventional technology]

In the manufacturing process of semiconductor devices, as a means for electrically connecting the pellet and each lead of the lead frame with wires, as described in JP-A-61-253824 and JP-A-61-253825, To,
The conveyance path (feeder) through which the lead frame is fed along the sidewalk in one direction is kept in an atmosphere of reducing gas S, and after the lead frame is heated to a predetermined temperature while being fed along the sidewalk, wire bonding is performed at the bonding stage. A wire bonding device configured as follows is used.

In addition, as a technique for avoiding deterioration of bondability due to rust during storage of lead frames, for example, as described in Japanese Patent Application Laid-open No. 10547/1983,
A technique has been proposed in which a rust preventive agent made of a compound of a metal and an organic substance is applied to the surface of a lead frame.

[Problem to be solved by the invention]

However, when wire bonding is performed using the above-mentioned wire bonding apparatus to a lead frame whose surface is coated with a rust preventive treatment agent, the rust preventive agent coated on the surface of the lead frame causes The inventor of the present invention has revealed that there is a problem in that the bonding strength between the bonding wire and the lead frame is reduced.

An object of the present invention is to provide a bonding technique that can improve the bondability of objects to be bonded whose surfaces are coated with a rust preventive treatment agent.

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

[Means to solve the problem]

An overview of typical inventions disclosed in this application is as follows.

That is, before bonding is performed on an object to be bonded, the surface of which is coated with a treatment agent, the attached treatment agent is removed by heating the object to be bonded in a non-oxidizing atmosphere. This is what I did.

[Effect]

According to the above-described means, since the rust preventive agent is removed from the surface of the object to be bonded before bonding is performed, deterioration of bondability due to the rust preventive agent is prevented.

〔Example〕

FIG. 1 is a front sectional view showing a bonding device according to an embodiment of the present invention, FIG. 2 is a partially omitted partially cutaway perspective view thereof,
FIG. 3 is a side sectional view taken along line [f[-III] of FIG.

In this embodiment, the bonding apparatus 1 according to the present invention bonds a pellet 2 in which a semiconductor integrated circuit is built to a multi-lead frame 3, and connects the electrode pad of the pellet 2 to the lead 4 of the multi-lead frame 3. The bellet 2 and each lead 4 are electrically connected by bonding the wires 5 to each other.

Here, the multiple lead frame 3 is integrally constituted by a plurality of unit lead frames 3a regularly arranged in one direction, and in this bonding apparatus 11, transportation is performed for each multiple lead frame 3. (Bellet and wire bonding are performed for each unit lead frame 3a.

This bonding apparatus 1 is equipped with a feeder 6 for feeding the multiple lead frames 3 in one direction. The unit lead frame 3a is configured to be fed step by step at a pitch by means (not shown). A wire bonding stage 27 is set in the downstream region of the feeder 6, and this wire bonding stage (will be described later).

) 27 is equipped with an XY child table so as to be movable in the XY force directions, and a bonding head 9 is mounted on the XY table 8. A bonding arm 10 is rotatably supported at its base end by the bonding head 9, and this arm 10 is equipped with a cam mechanism (not shown) so that a capillary 11 fixed at its tip can be moved up and down. It is configured to be driven by A pair of clamper arms 12.13 are installed on the upper side of the bonding arm 10 to be actuated by suitable means (not shown) such as a Nm plunger mechanism, and each tip of both arms 12.13 is capillary 11
The clamper 14 is arranged directly above the clamper 14. A wire 5 pulled out from a reel (not shown) is inserted through the clamper 14 via a guide 15.
Furthermore, it is inserted into the capillary 11.

A discharge electrode 16 is installed independently in the vicinity of the capillary 11, and the upper end of the discharge electrode 16 is rotatably supported so that its tip is positioned below the capillary 11, that is, the wire The capillary 11 is configured to be moved between a position directly below the tip of the capillary 5 and a position to the side of the capillary 11 (retracted position). Also, this release 1
An @'di circuit 17 is connected between the aTi pole 16 and the clamper 14, so that the clamper 14,
That is, the wire 5 inserted therein is used as an anode, and the electrode 16 is used as a cathode, so that a discharge arc is generated from the electrode 16 toward the wire 5.

A cover 18 is provided on the feeder 6 so as to cover substantially the entire multiple lead frame 3 to which the feeder 6 is fed, and the cover 18 has a substantially rectangular opening 19 which is connected to the wire bonding stage. The bonding area of the unit lead frame 3a is covered by the bonding area of the unit lead frame 3a. Opening 1
A lead frame holding member 20 formed in a substantially rectangular frame shape is fitted into the lead frame holding member 9 so as to be movable up and down. It is configured to raise its hoof in conjunction with the operation.

On the other hand, a heat block 21 is installed on the guide table 7 of the feeder 6 and arranged on a wire bonding stage, and the heat block 21 is configured to be temperature-controlled by a heater 21a. The wire bonding stage, that is, the wire bonding block 2I, which is disposed in the area including the opening 19, is provided with a lead frame oxidation prevention gas 22 for preventing oxidation of the multiple lead frame 3. A gas supply device 23 is installed, and this supply device 23 is equipped with an outlet 24. A plurality of air outlets 24 are provided on the upper surface of the heat protector 21 so that the lead frame oxidation prevention gas 22 can be gently blown out around the multiple lead frames 3. Gas is supplied to this group of air outlets 24. 25 is connected.

The gas supply path 25 is connected to a gas supply unit 26, and the gas supply unit 2G supplies an inert gas such as nitrogen (N1) gas, etc. to the frame at a preset flow rate. It is configured so that it can be supplied. The area where the heat block 21 is installed substantially constitutes a wire bonding stage 27.

Further, a pellet bonding stage 30 is set in the upstream region of the wire bonding stage 27 in this feeder 6, a second heat block 31 is installed in this stage 30, and a first heat block 31 in the wire bonding stage 27 is installed in the guide rail 7. heat block 21
They are arranged next to each other. The temperature of the second heat block 3 is controlled separately from that of the first heat block 21 by its heater 31a. The second heat block 31 is equipped with a gas supply device 33 as a means for supplying an anti-oxidation gas 32 to prevent oxidation of the multiple lead frame 3.
This supply device 33 is equipped with an air outlet 34 . Air outlet 3
4 is an anti-oxidation gas 32 around the multiple lead frame 3.
The heat block 31 is installed so that the
A plurality of blow-off ports 34 are provided on the top surface, and a gas supply path 35 is connected to this group of blow-off ports 34 . The gas supply path 35 is connected to a gas supply unit 36, and the gas supply path 36
For example, it is configured to be able to supply an antioxidant gas, for example, nitrogen gas, at a preset flow rate.

On the other hand, in the cover 18 of the pellet bonding stage 30, an insertion port 37 for a dispenser and an insertion port 38 for a collet are arranged at upstream positions, so that they can cover the bonding area of the unit lead frame 3a. It has been established. A dispenser 39 is located directly above the dispenser insertion port 37.
This dispenser 37 is equipped to be able to appear and retract from the IF material as pellet bonding material.
The structure is such that the (Ag) paste 40 can be applied onto the tabs in the unit lead frame 3a. Further, a collet 41 is installed directly above the collet insertion port 3B so as to be able to move in and out of the insertion port 38, and this collet 41 is placed near the feeder 6 (not shown). After pinking up the beret 2, insert it from the insertion slot 38 while holding it, and insert it into the unit lead frame 3.
It is configured so that it can be pounded onto the Ag paste 40 applied to the tab in a.

Furthermore, in this embodiment, a rust preventive treatment agent removal stage 50 is set in the Tsuchiura side area of the pellet pounding stage 30 in the feeder 6, and a third heat bronck 51 is attached to the guide rail 7 in this stage 50. It is installed adjacent to the second heat block 31 in the pellet pounding stage 30. The temperature of the third heat block 51 is controlled separately from the first heat block 21 and the second heat block 31 by the heater 51a.

The M3 heat block 51 disposed in the area of the rust preventive agent removal stage 50 removes the rust preventive agent,
In addition, a gas supply device 53 is provided as a means for supplying reducing gas 52 for reducing the multiple lead frame 3, and this supply device 53 is equipped with an outlet 54. A plurality of air outlets 54 are provided on the upper surface of the heat block 51 so that the reducing gas 52 can be warmly blown out around the multiple lead frame 3.
A gas supply path 55 is connected to the group.

The gas supply path 55 is connected to a gas supply unit 56, and the gas supply unit 56 is configured to supply a reducing gas, for example, a mixed gas consisting of nitrogen gas and hydrogen gas at a preset flow rate. ing.

A gas flow obstruction portion 18a is disposed on the inner surface of the cover 18 placed over the feeder 6 so as to cross the second heat block 31 and the third heat prong 51, and The gas flow on the heat block 31 side and the third
It is provided to protrude downward so as to prevent mixed flow with the gas flow on the heat block 51 side as much as possible.

Next, an embodiment of the bonding method according to the present invention will be explained by explaining the operation of the bonding device according to the above configuration.

The multiple lead frame 3, whose surface is coated with a rust preventive coating 3b made of metal and organic matter, is set on the guide table 7 by a loading device (not shown) installed at the upstream end of the feeder 6. The rust preventive agent is then supplied to a rust preventive removal stage 50.

In addition, the organic substances constituting the rust preventive agent include benzotriazole (C4HsNs), dodecyl mercaptan (C+z[zsSH), and propargyl alcohol (C
, H, OH), etc. Further, the rust preventive coating 3b made of these is applied to the lead frame to a thickness of about 20 mm by a suitable method such as a dipping method.

In this removal stage 50, reducing gas 52 is blown out from a group of outlets 54 by a reducing gas supply unit 56 via a gas supply MrB 55, and the blown out reducing gas 52 is prevented from dissipating by the cover 1B. Therefore, a reducing gas cloud is formed in the reduction stage 50. By the way, bellet bonding stage 3
Dissipation of gas toward the 0 side is prevented by a gas flow obstruction portion 18a protruding from the cover 18.

Then, this reducing gas 52 is transferred to the third heat block 51.
The temperature at which the rust preventive removal effect is exhibited most effectively (for example, 250 °C when the organic substance of the rust preventive is benzotriazole) and the temperature at which the multi-lead frame 3 is not adversely affected (350 °C) °C) or less. Moreover, since the reducing gas 52 is circulated inside the third heat block 51, it is effectively and stably heated.

When the multiple lead frame 3 coated with the rust preventive liquid H3b is supplied to the atmosphere of the reducing gas 52 in which the reduction reaction is most effectively activated in this way, the rust preventive coating 3b is applied. are effectively degraded and completely removed. Also,
For example, even if a copper-based (tlii or copper alloy) material that is easily oxidized is used, the surface of the lead frame 3 from which the rust preventive coating 3b has been removed is reliably prevented from oxidizing, and is will be done.

Further, the multi-lead frame 3 has a third heat bronch 51.
By being heated by this, it is preheated for the next bullet bonding operation.

The multiple lead frames 3 supplied to the rust preventive agent removal stage 50 are sequentially fed to the pellet bonding stage 30 by being fed step by step by the feeder 6 while being subjected to the above-described rust preventive agent removal, reduction and preheating effects. It will be supplied.

A gas 32 for preventing lead frame oxidation is supplied to this pellet bonding stage 30 through a gas supply unit 36.
The anti-oxidant gas 32 is blown out from the outlet 34 via the supply path 35, and the blown-out anti-oxidant gas 32 is prevented from dissipating by the cover 18, so that an anti-oxidant gas atmosphere is formed in the pellet bonding stage 30. There will be. Therefore, the lead frame 3 from which the rust preventive coating has been removed is placed on this pellet bonding stage 301.
Even after being fed, it is prevented from being oxidized.

Ag paste 40 is applied onto the tabs of the multiple lead frames 3 fed to the pellet bonding stage 30 by the dispenser 39 for each unit lead frame 3a, and then the pellets 2 are applied onto the tabs of the collets 4 on the Ag paste 40.
It is inserted by 1.

The multiple lead frame 3 to which the pellets 2 are bonded via the Ag paste 40 is gradually fed toward the wire bonding stage 27 by the feeder 6. During this feeding, the multi-wire frame 3 is heated by the second heat block 31 to the curing temperature of Ag 40, so that the Ag paste 40 is cured by heating. As a result, the pellet 2 becomes pellet-bonded to the lead frame by a bonding layer made of Ag paste 40.

In this way, in the pellet bonding stage 30, the multiple lead frames 3 subjected to pellet bonding are fed step by step by the feeder 6 while being subjected to a hardening action, and are sequentially supplied to the wire bonding stage 27. .

A gas 22 for preventing lead frame oxidation is blown out from a group of outlet ports 24 via a supply path 25 by a gas supply unit 26 to the bonding stage 27 , and the blown out oxidation preventing gas 22 is prevented from dissipating by a cover 18 . To prevent this, an oxidation-preventing gas atmosphere is formed in the bonding stage 27.

At the wire bonding stage 27 in the feeder 6, when the unit lead frame 3a is aligned in the hollow part of the lead frame holding member 20, the multiple lead frames 3 are stopped intermittently.

Subsequently, the lead frame holding member 20 is lowered,
The outer periphery of the unit lead frame 3i within the hollow portion is pressed. And this bonding stage 27
Since an oxidation-preventing gas atmosphere is formed in the unit lead frame 3a, the unit lead frame 3a is immersed in the oxidation-preventing gas atmosphere. Therefore, the multiple lead frame 3 from which the rust preventive liquid 111i3b has already been removed in the rust preventive agent removal stage 30 is reliably prevented from oxidizing.

On the other hand, in capillary 11, release! By bringing the electrode 16 close to the lower end of the wire 5 and closing the IIT source circuit 17, a ball 5a is melted and formed at the tip of the wire 5. At this time, if a reducing gas atmosphere is formed in the bonding stage 27 as in the conventional example, release! There is a risk that combustible gas such as hydrogen gas contained in the reducing gas may be ignited by the arc of the electrode 16.

However, in this embodiment, bonding stage 2
7 only has an oxidation-preventing gas atmosphere made of an inert gas such as nitrogen gas, so there is no risk of ignition (and it is extremely safe to work with).

Subsequently, the capillary 11 is lowered by the bonding head 9 and inserted into the opening 19 of the cover 18, and the pole 5a formed at the tip of the wire 5 aligns with the opening 19 to the pad of the pellet 2 in the unit lead frame 3a. Arrived at JLF1.

At this time, since the pellet 2 is heated by the first heat block 21, the pole 5a is thermocompression bonded onto the pad of the pellet 2.

After the first bonding part is formed, the capillary 11
is relatively moved three-dimensionally within the opening 19 by the XY child table and the bonding head 9, and the opening 1
The intermediate portion of the wire 5 is inserted into a predetermined glue 4 in the unit lead frame 3a that is aligned with the lead frame 9. At this time, since the lead 4 is heated by the first heat block 21, the wire 5 is thermocompressed onto the lead 4.

Incidentally, since the first heat block 21 does not need to activate the reducing gas, the heating temperature thereof is a temperature that does not have an adverse effect on the semiconductor device, and is suitable for thermocompression bonding '4 of the first and second bonding parts. (The temperature may be set to a secured temperature, for example, 160''C to 340''C.

When the second bonding is completed, the wire 5 is gripped by the clamper 14, and the clamper 14 is moved away from the second bonding portion together with the capillary 11. This separation movement causes the wire 5 to be torn off from the second bonding portion. After that, the wire 5 is clamped by the clamper 14.
is released and the capillary 11 is slightly raised, so that the tip of the wire 5 is attached to the pole 5a.
The tail is pushed out (tail extension) by the length required to form the material.

Thereafter, by repeating the above operation, wire bonding work is sequentially performed for each pad and lead in the first unit lead frame 3a.

When the wire bonding for the first unit lead frame 3a is completed, the lead frame holding member 2
0 is raised. When the lead frame holding member 20 rises to the top dead center, the multiple lead frame 3 is fed one pinch ahead by the feeder 6, and a new unit lead frame 3a is fed into the holding member 20 to the corresponding bonding stage.

Thereafter, by repeating the above-mentioned operation, the wire bonding work is performed on all the unit lead frames 3a in the multiple lead frames 3.

By the way, if a copper-based lead frame is used as the lead frame, the bonding part is not partially silver plated, and the rust preventive coating is removed,
Since copper is easily oxidized and a thick oxide film is formed on the bonding surface, bondability in the second bonding is reduced.

That is, when an oxide film is formed, the metal bondability with the wire decreases, resulting in a decrease in bondability.

However, in this example, the lead frame is very effectively reduced in the rust inhibitor removal stage, and after being supplied to the pellet and wire bonding stage, it is immersed in an antioxidant gas atmosphere to prevent oxidation. This effectively prevents the formation of an oxide film on the surface of the copper lead frame, which is easily oxidized, even if the rust preventive treatment agent is removed. is bonded onto the lead 4 with good bondability.

Incidentally, if the rust preventive coating 3b remains on the surface of the lead 4 during bonding of the wire to the lead, the rust preventive will coat the bonding surface between the wire 5 and the lead 4 during the second bonding. By intervening therebetween, the bonding strength at the second bonding portion decreases or bonding becomes impossible.

However, in this embodiment, since the rust preventive agent has already been completely removed from the surface of the multiple lead frame 3, such deterioration in bondability due to the presence of the rust preventive agent can be avoided. It turns out.

According to the embodiment described above, the following effects can be obtained.

0) Before bonding is performed on a bonded object whose surface has been coated with a processing agent such as a v3DI agent, the bonded object is heated in a non-oxidizing atmosphere to remove the applied processing agent. This makes it possible to avoid the presence of a processing agent during bonding to the object to be bonded, thereby preventing deterioration in bondability due to the presence of the processing agent.

(2) According to the above (1), the quality and reliability of the semiconductor device can be improved.

(3) A rust preventive removal stage is provided before the bonding stage to remove the rust preventive film deposited on the surface of the lead frame, and an oxidation preventing gas is supplied to this rust preventive removal stage. By using a reducing gas, it is possible to reduce the amount of reducing gas used and ensure proper bondability of the lead frame, thereby reducing costs while ensuring the desired quality and reliability. can be reduced.

By configuring the temperature 1i1J control of the rust preventive agent removal stage to be performed independently from the pellet and wire bonding stages, the reduction reaction of the reducing gas can be carried out in the most effective manner without being restricted by the temperatures of both bonding stages. Since it can be activated automatically, the rust inhibitor removal effect can be enhanced.

(5) By providing a gas flow obstruction section at the boundary between the rust preventive agent removal stage and the bonding stage, it is possible to suppress the dissipation of reducing gas to the bonding stage, thereby reducing the amount of reducing gas used. This can be further reduced.

(6) By forming the bonding stage in an antioxidant gas atmosphere, it is possible to avoid ignition of combustible gases such as hydrogen contained in reducing gases, so discharge electrodes for forming nail balls can be used. It can improve the safety of wire bonding work using torches and torches.

(7) By effectively reducing the lead frame and reliably preventing the formation of an oxide film, it is possible to maintain good metal bonding properties, ensure proper bonding, and ultimately improve product quality and reliability. In addition, it is possible to reliably prevent the formation of an oxide film even on lead frames that are easily oxidized, such as copper-based lead frames.By realizing the use of copper-based lead frames, costs can be reduced. It is possible to promote the

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the step of removing the processing agent from the surface of the bonding object is not limited to being set online in the pellet and wire bonding step, but may be set offline.

Further, the processing agent removal step is not limited to being set before the pellet bonding step, but may be set between the pellet bonding step and the wire bonding step.

The antioxidant gas supplied to the processing agent removal stage is not limited to a reducing gas, but may also be an inert gas such as nitrogen.

The pellet bonding material is not limited to Ag paste, but may also be a solder material. If a solder material is used, the lead frame is reduced by the processing agent removal stage, so that the solder on the bonding floor is reduced. Since the wettability is increased, the bondability of beret bonding can be improved.

The lead frame is not limited to a copper-based one, but may also be an iron-nickel lead frame, or a multiple lead frame in which multiple lead frames are arranged in one direction. The number of wire bonding devices installed on the wire bonding stage is not limited to the number of wire bonding devices installed on the pellet bonding stage. 1
The number may be even greater than the number of 1tM.

The above explanation has mainly been about the application of the invention made by the present inventor to the field of application which is its background, pellet bonding technology using Ag paste and thermocompression wire bonding technology IH, but the invention is limited thereto. Rather, it can be applied to any bonding technology in general, such as ultrasonic thermocompression bonding or ultrasonic wire bonding technology alone, as well as fR, a mounting technology for electronic components on printed wiring boards.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

Before bonding is performed on an object to be bonded whose surface has been coated with a treatment agent such as rust prevention, the object to be bonded is heated in a non-oxidizing atmosphere to remove the applied treatment agent. Since it is possible to avoid the presence of a processing agent during bonding to the object to be bonded, it is possible to prevent deterioration in bondability due to the presence of the processing agent.

[Brief explanation of drawings]

Fig. 1 is a front sectional view showing a bonding device which is an embodiment of the present invention, Fig. 2 is a partially omitted partially cutaway perspective view, and Fig. 3 is a side sectional view taken along the line ■-■ in Fig. 1. It is a diagram. l...Bonding device, 2...Berent, 3...
・Multiple lead frame (object to be bonded), 3a...
・Unit lead frame, 3b... - Rust preventive coating, 4...
・Lead, 5...Wire, 5a...Ball, 6...
・Feeder, 7... Guide table, 8... XY child table 9... Bonding head, 10... Bonding arm, 11... Capillary (bonding tool), 12.13... Clamper arm, 14・
... Clamper, 15... Guide, 16... Discharge electrode, 17... Power supply circuit, 18... Cover 18a...
- Gas flow obstruction part, 19... opening, 20... lead frame holding member, 21... first heat pump,
22...Lead frame oxidation prevention gas, 23...
Antioxidant gas supply device, 24... Outlet, 25...
- Supply path, 26... Gas supply unit, 27... Wire bonding stage, 30... Pellet bonding stage, 31... Second heat block, 32
...Antioxidant gas, 33...Antioxidant gas supply device, 34-Blower outlet, 35--Supply path, 36--Gas supply unit, 37--Dispenser insertion port, 3
Day... - Collet insertion port, 39... Dispenser,
40...Ag paste (Berent bonding material),
41... Collet, 50... Rust preventive agent removal stage,
51...-Third heat block, 52... Reducing gas, 53... Reducing gas supply device, 54... Air outlet,
55... Gas supply path, 56... Gas supply unit.

Claims (1)

[Claims] 1. Before bonding is performed on a bonding object whose surface has been coated with a treatment agent, the applied treatment can be performed by heating the bonding object in a non-oxidizing atmosphere. A bonding method characterized by removing the agent. 2. A processing agent removal stage is provided before the bonding stage in which bonding is performed on the bonding object, which removes the processing agent adhered to the surface of the bonding object by heating the bonding object. A bonding apparatus characterized in that the processing agent removal stage is configured to be supplied with an antioxidant gas. 3. The bonding apparatus according to claim 2, wherein the processing agent removal stage is disposed on the upstream side of the bonding stage on a feeder that conveys the objects to be bonded in one direction.