JPH08148520A - Wire bonder - Google Patents

Abstract

PURPOSE: To obtain a wire bonder in which all inner leads being set at wire bonding positions, can be applied tightly and surely to a heater block. CONSTITUTION: The wire bonder comprises a heater block 4 for heating a lead frame, and a lead clamper 2 for holding a plurality of inner leads positioned on the heater block 4 while pressing. A semiconductor chip on the lead frame is then connected through a wire with the inner lead while clamping the plurality of inner leads arranged on the heater block 4. The wire bonder further comprises a plate 21 for knocking up the lead frame by a predetermined amount in a region on the outside of the clamping position of the lead clamper 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding device for connecting a semiconductor chip mounted on a lead frame and inner leads arranged around the semiconductor chip with wires such as gold wires.

[0002]

2. Description of the Related Art FIG. 6 is a plan view showing a lead frame after die bonding. The illustrated lead frame F is formed into a predetermined shape by using a processing method such as a pressing method or an etching method. A reference hole H serving as a conveyance reference is formed in the outer frame portion of the lead frame F by a wire bonding device. A plurality of die pads D are formed between the outer frames of the lead frame F at a predetermined pitch, and the semiconductor chip C is mounted on each die pad D.

FIG. 7 is a plan view of a main part of a conventional wire bonding apparatus, and FIG. 8 is a side sectional view of the main part.
In the wire bonding apparatus 1 shown in FIGS. 7 and 8, 2 is a lead clamper, 3 is a pair of left and right frame guides, 4 is a heater block, 5 is a vertically movable clamp holder, and 6 is a fixing screw for fixing the lead clamper 2. is there.
A work window 8 of a predetermined size is provided on the tip side of the lead clamper 2.
Is provided. Further, the lead clamper 2 is provided with a lead retainer 9 along the peripheral edge of the work window 8.
On the other hand, a pair of left and right frame guides 3 are formed with guide grooves 3a. Further, a heater 10 serving as a heat source is incorporated inside the heater block 4.

Subsequently, the conventional wire bonding apparatus 1
The operation of will be described. First, the lead frame F on which the semiconductor chip C is mounted is conveyed onto the heater block 4 while being guided by the left and right frame guides 3 as shown in FIG. Next, as shown in FIG. 9, the clamp holder 5 is lowered integrally with the lead clamper 2, and the lead pressing portion 9 is abutted against the inner lead L. Subsequently, the bonding tool 11 mounted on a bonding head (not shown) advances onto the semiconductor chip C through the work window 8 and connects the semiconductor chip C and the inner lead L with the wire W. After that, when the connection of the predetermined number of wires W is completed, the bonding tool 11 and the lead clamper 2 are raised, and then the lead frame F is conveyed again, and thereafter, the number of semiconductor chips mounted on the lead frame F is reduced. Accordingly, the above series of operations is repeated.

[0005]

However, in the conventional wire bonding apparatus 1, the inner lead L
There is a step or twist, the top surface of the heater block 4 or the tip of the lead pressing portion 9 (the portion in contact with the inner lead L) is not flat, and the parallelism between the heater block 4 and the lead clamper 2 is high. If the inner leads L arranged on the heater block 4 are pressed by the lead pressing portion 9 of the lead clamper 2, all the inner leads L cannot be reliably pressed and the inner leads L cannot be reliably pressed. The lead L was insufficiently pressed or lifted. As a result, the heat of the heater block 4 is not sufficiently transmitted to all the inner leads L, the bonding strength of the wire W is insufficient due to insufficient heating, and the wire W is peeled off. There was a problem that reliability was lost.

Further, although the parallelism between the heater block 4 and the lead clamper 2 can be adjusted by the adjusting screw 12, the adjustment work requires skill and the adjustment itself is very troublesome. there were. If the adjustment amount is further increased, there is a possibility that the entire lead clamper 2 is warped and the same problem as described above is caused.

The present invention has been made in order to solve the above problems, and an object of the present invention is to ensure that all the inner leads set at the wire bonding positions are brought into close contact with the heater block and the semiconductor chip and An object of the present invention is to provide a wire bonding device capable of connecting the inner lead with a wire.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and comprises a heater block for heating a lead frame and a plurality of inner leads positioned on the heater block. A wire for connecting the semiconductor chip mounted on the lead frame and the inner lead with a wire, which is equipped with a lead clamper for pressing and holding, and clamps a plurality of inner leads arranged on the heater block with the lead clamper. The bonding apparatus has a push-up mechanism that pushes up the lead frame by a predetermined amount in an area outside the lead clamp position by the lead clamper.

[0009]

In the wire bonding apparatus of the present invention,
Even if the inner lead is clamped by the lead clamper and any one of the inner leads is insufficiently pressed or lifted, the lead frame is pushed up in the area outside the lead clamp position by the lead clamper from that state, The tip side of the inner lead is urged toward the heater block with the clamp position as a fulcrum, and the tip portion of the inner lead is surely brought into close contact with the heater block by the urging force.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a perspective view of an essential part showing an embodiment of a wire bonding apparatus according to the present invention, and FIG. 2 is a side sectional view thereof. In this embodiment,
The same components as those in the above-mentioned conventional example are denoted by the same reference numerals, and redundant description will be omitted as much as possible. In the illustrated wire bonding apparatus 1, 2 is a lead clamper, 3 is a pair of left and right frame guides, and 4 is a heater block. The lead clamper 2 is fixed by a pair of fixing screws 6 to a clamp holder 5 which is supported so as to be able to move up and down by an elevator unit (not shown) (for example, a ball screw unit using a motor as a power source). The lead clamper 2 is positioned on the clamp holder 5 by two positioning pins 7. As shown in FIG. 2, a work window 8 for performing wire bonding is provided on the tip side of the lead clamper 2, and this work window 8 is an external dimension of the semiconductor chip C mounted on the lead frame F. It has a larger opening than. Further, the lead clamper 2 is provided with a lead pressing portion 9 along the work window 8, and the inner lead L is pressed against the heater block 4 by the lead pressing portion 9.

The pair of frame guides 3 regulate the conveying direction of the lead frame F, and they are installed in an opposed state corresponding to the width of the lead frame F.
A guide groove 3a wider than the plate thickness of the lead frame F is formed in each frame guide 3, and the outer frame portion of the lead frame F is inserted into each guide groove 3a when the lead frame is transported. ing.

The heater block 4 is for heating the semiconductor chip C and the inner leads L to a predetermined temperature during wire bonding, and a cylindrical heater 10 serving as a heat source is incorporated therein. ing. The heater block 4 is installed between the pair of frame guides 3. Further, the upper surface of the heater block 4 and the bottom surface of the guide groove 3a of the frame guide 3 are arranged at substantially the same height.

Here, the feature of the present invention resides in that a push-up mechanism for pushing up the lead frame F by a predetermined amount (described later) in an area outside a lead clamp position (described later) by the lead clamper 2 is provided. The specific structure of the push-up mechanism will be described below. First, in the vicinity of the heater 10 incorporated in the heater block 4,
A plate guide hole 20 is formed along the axial direction of the heater block 4 (vertical direction in the illustrated example).
Push-up plates 21 are slidably inserted into the individual plate guide holes 20, respectively.
These push-up plates 21 are provided according to the lead arrangement form of the lead frame F, and in this example, Q
Since the lead frame F for FP (Quad Flat Package) is the object to be handled, one push-up plate 22 is provided in each of the four sides of the heater block 4.

By the way, in the actual wire bonding process, the semiconductor chip C mounted on the lead frame F is positioned and arranged in the central portion of the heater block 4. At this time, the lead clamp position of the lead clamper 2, that is, the contact position of the lead pressing portion 9 with respect to the inner lead L is set to a region slightly outside the wire bonding position of the inner lead tip. Therefore, in the configuration of the present embodiment, the plate guide hole 20 is opened so that the push-up plate 21 is located in a region further outside the lead clamp position.

Further, the lower surface side of each push-up plate 21 is projected from the lower surface of the heater block 4,
For example, it is fixed on the common plate holder 22 by screwing. The plate holder 22 is supported by a drive unit (not shown) such as a ball screw unit using a motor as a power source, an air cylinder, or the like so that the plate holder 22 can be moved up and down, and the upper end surface of the push-up plate 22 projects from the upper surface of the heater block 4. It is possible.

The operation of the wire bonding apparatus 1 of this embodiment will be described next. First, the lead clamper F on which the semiconductor chip C is mounted is conveyed in one direction according to the feeding operation of a feed mechanism (not shown) while being guided by the pair of left and right frame guides 3. Next, of the plurality of semiconductor chips C mounted on the lead frame F, the first (usually the leading position) semiconductor chip 2 is located directly below the work window 8 of the lead clamper 2 as shown in FIG. It is positioned at the set bonding position. At this time, the lead frame F is arranged on the heater block 4 installed between the pair of frame guides 3. At this time, the upper end surface of the push-up plate 21 is arranged at a position slightly lower than the upper surface of the heater block 4 so as not to hinder the conveyance of the lead frame F.

When the first semiconductor chip C is arranged at the bonding position on the heater block 4 in this way, the clamp holder 5 is lowered together with the lead clamper 2 by driving an elevating unit (not shown). As a result, as shown in FIG. 3, the tip portion of the lead pressing portion 9 protruding from the lower surface of the lead clamper 2 abuts the inner lead L. At this time, as described above, due to the step or twist of the inner lead L, the flatness of the lead pressing portion 9, the parallelism between the heater block 4 and the lead clamper 2, etc., the heater block 4 is sufficiently adhered. The inner lead L that does not exist or the inner lead L that slightly rises may occur.

Therefore, in the present embodiment, a drive unit (not shown) is operated in a state in which the tip end portion of the inner lead L is clamped by the lead holding portion 9 of the lead clamper 2 to operate the push-up plate 21 together with the plate holder 22 with the lead clamper. Push up to side 2. As a result, the upper end surface of each push-up plate 21 projects from the upper surface of the heater block 4, and the lead frame F is pushed up by the push-up plate 21 in an area outside the lead clamp position P, as shown in FIG. . In this state, as shown in FIG. 4, with the contact position A between the lead pressing portion 9 and the inner lead L being the fulcrum, and the contact position B between the push-up plate 21 and the lead frame F being the acting point, the inner lead L is An urging force M acts on the tip end of the arrow as indicated by the arrow in the figure. Therefore, even with the inner lead L having a lifted tip, the tip of the lead, which is the wire bonding portion, is reliably brought into close contact with the heater block 4 by the urging force M.

By the way, the push-up amount Z (see FIG. 4) of the push-up plate 21 with respect to the lead frame F is appropriately within the elastic limit of the lead frame F, that is, within the range in which the pushed-up lead frame F can return to the original planar state. It is set, and in this embodiment, Z = 0.2 to 0.3.
It is set to mm. Further, the contact point B between the push-up plate 21 and the inner lead L is appropriately set in the area outside the lead clamp position P, and in the present embodiment, the inner lead slightly inside the tie bar (not shown). It is set at the rear end of L.

Next, a bonding tool (capillary, wedge tool, etc.) 11 mounted on a bonding head (not shown) advances onto the semiconductor chip C through the work window 8 of the lead clamper 2 (see FIG. 3), and the semiconductor thereof. The semiconductor chip C and the inner lead L are connected by the wire W while reciprocating between the chip C and the inner lead L. After that, when the bonding tool 11 is retracted upward after the connection of the predetermined number of wires W is completed, the push-up plate 21 is lowered together with the plate holder 22 by the operation of the drive unit (not shown), and the push-up plate 21 is again pushed from the upper surface of the heater block 4. The upper end surface of 21 is retracted. Then, the lead clamper 2 ascends together with the clamp holder 5 by driving an elevating unit (not shown), whereby the lead pressing portion 9 of the lead clamper 2 separates from the inner lead L, and the clamped state of the lead frame F is released. It

After that, the lead frame F is guided by the frame guide 3 and conveyed at a constant feed pitch by a feed mechanism (not shown), whereby the next (second) semiconductor chip C is positioned at the bonding position. To be done. Such a series of operations is sequentially repeated according to the number of semiconductor chips C mounted on the lead frame F.

As described above, in the wire bonding apparatus 1 of the present embodiment, while the inner lead L set at the wire bonding position while being guided by the frame guide 3 is clamped by the lead clamper 2, the lead clamp position by the lead clamper 2 is held. By pushing up the lead frame F by a predetermined amount Z in the area outside P,
Even if the tip of one of the inner leads floats, a biasing force M is applied to the tip of the inner lead L with the lead clamp position P as a fulcrum, and the tip of the inner lead L is heated by the biasing force M. The block 4 can be firmly attached.

At the contact position A between the lead clamper 2 and the inner lead L and the contact position B between the push-up plate 21 and the lead frame F, as shown in FIG.
If the tip portion of the lead pressing portion 9 and the upper end portion of the push-up plate 21 are angular, local wedge stress may be applied to the surface of the frame, which may cause damage. Therefore, in this embodiment, the upper end of the push-up plate 21 is rounded as shown in FIG. 5A, or the upper end of the push-up plate 21 is formed in a semicircular cross section as shown in FIG. 5B. In addition, as shown in FIG. 5 (c), the tip of the lead pressing portion 9 is rounded. Thereby, the contact position A between the lead clamper 2 and the inner lead L and the contact position B between the push-up plate 21 and the lead frame F.
Then, since the lead pressing portion 9 and the push-up plate 21 come into contact with the frame surface with a curved surface,
No local wedge stress is applied to the respective contact positions A and B, and it is possible to reliably prevent damage to the frame surface due to the push-up of the lead frame F.

In the structure of the above embodiment, the push-up plates 2 are arranged in the four sides of the heater block 4, respectively.
However, the lead frame F to be handled is, for example, an SOP (Small Outline Pack).
In the case of the age type, it can be dealt with only by providing the push-up plates 21 in the two sides of the heater block 4. Further, the specific configuration of the push-up mechanism is not limited to the one using the push-up plate 21 as described above, and although not shown, for example, the leads are arranged along the arrangement direction of the inner leads L on the heater block 4. An eccentric cam is provided in an area outside the clamp position P, and the lead frame F is pushed up by the cam surface by rotating the eccentric cam by a predetermined angle.
In the case of the P type, various modifications are possible, such as installing a pair of left and right frame guides 3 so that they can be raised and lowered, and raising the frame guides 3 by a predetermined amount to push up the lead frame F.

[0025]

As described above, according to the wire bonding apparatus of the present invention, from the state where the inner leads set on the heater block are clamped by the lead clamper, the area outside the lead clamp position by the lead clamper is provided. By pushing up the lead frame with, all inner leads can be surely brought into close contact with the heater block. Therefore, at the time of wire bonding, the heat of the heater block can be surely transferred to all the inner leads.
It is possible to prevent wire connection failures (insufficient adhesive strength, wire peeling, etc.) due to insufficient heating of the inner leads.
The reliability as a semiconductor device can be significantly improved. Further, according to the present invention, all the inner leads are surely brought into close contact with the heater block by the push-up action of the push-up mechanism as described above, without precisely adjusting the parallelism between the heater block and the lead clamper as in the conventional device. Therefore, the time required for mechanical adjustment can be significantly saved.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part showing an embodiment of a wire bonding apparatus according to the present invention.

FIG. 2 is a side sectional view of the wire bonding apparatus in the embodiment.

FIG. 3 is a diagram for explaining the operation of the wire bonding apparatus in the example.

FIG. 4 is an enlarged view of a main part of FIG. 3;

FIG. 5 is a diagram illustrating another embodiment of the present invention.

FIG. 6 is a plan view showing a lead frame after die bonding.

FIG. 7 is a plan view of an essential part showing a conventional wire bonding apparatus.

FIG. 8 is a side sectional view of a main part of a conventional wire bonding apparatus.

FIG. 9 is a diagram illustrating an operation of a conventional wire bonding apparatus.

[Explanation of symbols]

1 Wire Bonding Device 2 Lead Clamper 4 Heater Block 20 Plate Guide Hole 21 Push Up Plate 22 Plate Holder C Semiconductor Chip F Lead Frame L Inner Lead

Claims (1)

[Claims] 1. A heater block for heating a lead frame, and a lead clamper for pressingly holding a plurality of inner leads positioned and arranged on the heater block, the plurality of heater blocks arranged on the heater block. In a wire bonding apparatus for connecting the inner lead with a semiconductor chip mounted on the lead frame with a wire while clamping the inner lead with the lead clamper, a region outside a lead clamp position by the lead clamper. 2. A wire bonding apparatus comprising a push-up mechanism that pushes up the lead frame by a predetermined amount.