JP2725117B2 - Wire bonding apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for assembling a semiconductor device, comprising: a first bonding point, for example, an electrode (pad) on a semiconductor chip; and a second bonding point, for example, an external lead provided on a lead frame. And a method for connecting the same using wires.

[0002]

2. Description of the Related Art Conventionally, in a wire bonding apparatus for connecting an electrode on a semiconductor chip serving as a first bonding point and a lead serving as a second bonding point using a gold wire or a wire such as copper or aluminum, a capillary is first used. A high voltage is applied between the tip of the wire protruding from the wire and a discharge electrode (electric torch) to cause a discharge, and the discharge energy melts the tip of the wire and the tip of the wire inserted into the capillary. A ball is formed. Then, while the ball held at the tip of the capillary is brought into contact with the bonding point, heating is performed using both ultrasonic waves and other heating means, and a wire is connected to the bonding point.

FIG. 13 shows the steps of the bonding operation. That is, as shown in FIG. 13A, first, a discharge is caused between the tip of the wire 102 protruding from the tip of the capillary 101 and a discharge electrode (electric torch) (not shown) to melt the wire 102. An initial ball IB is formed and held at the tip of the capillary 101.

A capillary 101 is connected to a pad 10 of an IC chip (semiconductor) 103 serving as a first bonding point.
4 is located directly above. Next, as shown in FIG. 13B, the capillary 101 is lowered and the ball IB is
4 and further pressurized by bonding.
As shown in (c), a predetermined crimping diameter D and a predetermined crimping thickness W
Crush ball IB until D is reached.

At the same time as the pressing action of the crushing, an ultrasonic horn (not shown) is applied to the tip of the capillary 101.
The connection is made by using ultrasonic waves and other heating means in combination. The wire 102 is connected to the pad 104 by heating connection using ultrasonic waves or the like, and then, as shown in FIG. 13D, the capillary 101 is raised and moved in the horizontal direction according to a predetermined loop control, and the second bonding is performed. The capillary 101 is moved down as shown by a two-dot chain line, and the wire 10 is moved by the lower end of the capillary 101.
2 is partially crushed to form a flat portion.

Here, ultrasonic waves are again applied to the tip of the capillary 101 to connect the wire 102 to the lead 105. Thereafter, the wire 102 is pulled to cut the wire 102 from the end of the flat portion, and thereafter, the capillary 101 is raised to complete one bonding operation.

Then, the capillary 101 is again opposed to a discharge electrode (not shown) so that the wire 1 at the tip of the capillary 101
02 between the discharge electrode 02 and the discharge electrode.
The ball IB is formed at the end of the first line, and the state returns to the state shown in FIG.

[0008]

In the conventional wire bonding apparatus shown in FIG. 13, in order to obtain a bonding shape having a predetermined crimping diameter D and a predetermined crimping thickness WD shown in FIG. The operator sets various factors such as the ultrasonic power applied to the tip of the capillary, the ultrasonic application time, and the pressure applied by the capillary to the bonding point as needed. That is, provisional bonding for making these settings is prepared, and bonding is performed on the provisional bonding to select a ball having both a ball compression diameter D and a compression thickness WD within a desired range.

Further, when the capillary for bonding is changed, there is a problem that the bonding state changes depending on the type of the capillary. Therefore, it is difficult for an expert to set each parameter by further adding such an element. However, it is not easy, and in order to obtain the desired bonding shape of the pressure bonding diameter D and the pressure bonding thickness WD, it is necessary to repeat the bonding operation and the measuring operation many times.

In particular, recently, with the increase in the number of pins of the IC, it has been desired to reduce the distance between adjacent pads and to achieve a stable and uniform pressure-bonded ball shape in a situation where the number of pads is reduced.

In view of the above, the present invention has been made in view of the conventional problems. By inputting and executing at least data relating to a predetermined crimping diameter D, a predetermined crimping thickness WD, and a type of a capillary by using a keyboard, The ultrasonic power for obtaining the bonding shape described above, the ultrasonic application time and the pressing force applied to the capillary are automatically calculated,
It is an object of the present invention to provide a bonding apparatus capable of performing bonding of a predetermined shape to a bonding point by a control signal based on the calculation result.

[0012]

SUMMARY OF THE INVENTION The present invention is a wire bonding apparatus for bonding a wire to a bonding point by ultrasonic waves applied to the tip of a capillary, wherein the tip of the capillary is crimped to a bonding point. A keyboard for inputting and executing at least the bonding shape data relating to at least the crimping diameter D and the crimping thickness WD and the data relating to the capillary, and the bonding shape relating to at least the crimping diameter D and the crimping thickness WD inputted by the keyboard. Calculating means for receiving data and data relating to the capillary, and generating an ultrasonic power applied to the tip of the capillary at the time of bonding, a control signal relating to an ultrasonic application time, and a control signal relating to the pressure applied to the capillary at the bonding point; Based on the control signal outputted from the stage, the capillary tip ultrasonic power applied to, which is constituted so as to control the pressure applied to the application time and the capillary. The present invention also provides a wire bonding method for bonding a wire to a bonding point by ultrasonic waves applied to a capillary tip, wherein at least a crimp diameter formed when the capillary tip is crimped to the bonding point by a keyboard. D and the bonding shape data relating to the pressure bonding thickness WD and the data relating to the capillary are input and executed and output to the calculating means, the ultrasonic power applied to the tip of the capillary calculated by the calculating means, the control signal relating to the ultrasonic application time and the bonding. A wire is bonded to a bonding point on the basis of a control signal relating to the pressure of the capillary on the point.

[0013]

Embodiments of the present invention will be described below. FIG.
1 shows a configuration of a wire bonding apparatus according to the present invention. Note that a detailed description of a device having the same function and configuration as a conventional device is omitted.

In FIG. 1, a drive arm 1 and a bonding arm 2 are supported by a shaft 3 so as to be swingable independently. The bonding arm 2 holds, via a support member 5a, an ultrasonic horn 5 to which a capillary 4 for performing bonding connection is attached at the tip. An ultrasonic vibrator 6 for generating ultrasonic waves is provided at an end of the ultrasonic horn 5.
The ultrasonic wave generated by the ultrasonic transducer 6 is applied to the tip of the capillary 4 via the ultrasonic horn 5.

In the vicinity of the rear end face of the ultrasonic vibrator 6, the contacts 7 and 7 'are connected to the drive arm 1 and the bonding arm 2 respectively.
Are provided opposite to each other. The drive arm 1 and the bonding arm 2 have a pair of solenoid units 8.
When the solenoid units 8 and 8 'are excited by a command from a control circuit (not shown), they are attracted to each other, and the bonding arm 2 is supported on the shaft 3 in the direction of arrow ZZ' in FIG. To act on. However, since the contact points 7 and 7 'come into contact with each other and act as a stopper, the positional relationship between the drive arm 1 and the bonding arm 2 is fixedly held.

Between the contacts 7 and 7 'and the solenoid units 8 and 8', pressing coil units 9 and 9 'serving as pressing means are provided with a driving arm 1 and a bonding arm 2.
Detectors 10 and 10 ′ for detecting the displacement of the positional relationship between the drive arm 1 and the bonding arm 2 at the same time as the contacts 7 and 7 ′ are separated.

A vertical swing device for swinging the drive arm 1 up and down in the direction of arrow ZZ 'uses, for example, a cam mechanism (not shown). This vertical rocking device may be replaced with a cam mechanism having a configuration like a linear motor. When the drive arm 1 is oscillated in the direction of the arrow ZZ ′ by this vertical swing device, the bonding arm 2 is also configured to perform a swing motion in conjunction with the drive arm 1.

The operation of the apparatus having the above configuration will be described below with reference to FIG. 13 again.

FIG. 13A shows a lowered state by the capillary 4 (101) for performing the first bonding. A ball IB formed at the tip of the wire 102 is wound by a spool (not shown). (10
1) is fully pulled back to the side and the capillary 4 (10
The pad approaches the pad 104 provided on the IC chip 103 by the constant velocity circular motion of 1).

Thereafter, as shown in FIG.
B collides with the pad 104, and the ball IB is slightly deformed by the kinetic energy of the capillary 4 (101). At this time, the drive arm 1 continues the circular motion in the Z direction in FIG. 1 by a vertical swinging device (not shown), but the bonding arm 2 is connected to the pad via the capillary 4 (101) and the ultrasonic horn 5. Since the drive arm 1 is in a stopped state in contact with the upper surface of the drive arm 104, only the drive arm 1 continuously rotates in the Z direction in FIG. Is displaced.

The displacement is detected by the detector 10, and the vertical swing device is stopped by an instruction from a control circuit, which cannot be shown, based on the detected output. After this stop, the pressurizing coil units 9 and 9 ', which are pressurizing means, are excited to make the
A pressing force is generated in the direction of arrow B shown in FIG. The pressing force in the direction of arrow B is performed by using both the application of ultrasonic waves in the direction of arrow A, the pressing in the direction of arrow B, and a pressing means (not shown). )
As shown in (2), the connection is made until a predetermined pressure bonding diameter D and pressure bonding thickness WD are reached, and the bonding connection to the first bonding point is completed.

The bonding connection to the second bonding point is performed by the capillary 4 as shown in FIG.
(101) is moved in the horizontal direction to be positioned above the lead 105 serving as a second bonding point, and the capillary 101 is lowered as shown by a two-dot chain line to thereby remove the capillary 4.
A part of the wire 102 is crushed by the lower end of (101) to form a flat portion. Here again, capillary 4 (1
The wire 102 is connected to the lead 105 by applying an ultrasonic wave to the tip of (01).

As described above, when the capillary is pressed against the bonding point, a predetermined ultrasonic power is applied for a predetermined time, and a predetermined pressure is applied to the capillary.

FIG. 2 shows a predetermined ultrasonic power as described above,
FIG. 3 shows an example of a control circuit for generating a control signal relating to an ultrasonic application time and a control signal relating to a pressure of a capillary at a bonding point. That is, in FIG. 2, reference numeral 11 denotes a keyboard execution switch. The keyboard execution switch 11 relates to a bonding diameter D, a bonding thickness WD, and a capillary to be formed when a capillary is bonded to a bonding point. Data (details will be described later) is input and executed. When data relating to the bonding diameter D, the bonding thickness WD, and the capillary for the bonding are input, the data is supplied to an arithmetic circuit 12 as arithmetic means including a microprocessor unit (μpc). Here, the data on the capillary includes the wire diameter.

The arithmetic circuit 12 receives the data on the desired bonding diameter D, the bonding thickness WD, and the capillary, and generates the predetermined ultrasonic power by referring to the data table 13 connected to the arithmetic circuit 12. A control signal p, a control signal t for controlling a predetermined ultrasonic application time, and a control signal f relating to the pressure of the capillary at the bonding point are calculated.

The control signals p, t and f calculated by the arithmetic circuit 12 constitute an ultrasonic control circuit 14 for controlling the ultrasonic output, a switch circuit 15 for performing time control, and a capillary pressurizing means. It is supplied to the pressurization control circuit 16. The ultrasonic control circuit 14 includes an arithmetic circuit 1
An ultrasonic drive signal is generated in proportion to the control signal p supplied from the control circuit 2 and supplied to the switch circuit 15.
Further, the switch circuit 15 keeps the ON state for a predetermined time based on the control signal t supplied from the arithmetic circuit 12, during which the ultrasonic drive signal supplied from the ultrasonic control circuit 14 is supplied to the ultrasonic transducer 6. Supply. Further, the pressure control circuit 16 supplies a pressure drive signal proportional to the control signal f supplied from the arithmetic circuit 12 to the pressure coil units 9 and 9 '.

The capillaries 4 are provided with various chamfer diameters as shown in FIG. That is, in FIG. 3, H is the hole diameter of the capillary, CD is the chamfer diameter, θ is the chamfer angle, D is the above-mentioned crimp diameter, and WD is the above-mentioned crimp thickness.

[0028] Then, together with the capillary bonding condition is changed in accordance with various chamfer diameter CD and the like, further type of capillary, i.e. material of the capillary (ceramic or ruby), the taper angle of the capillary (e.g., 30 ⁰ or ²⁰⁰ ), tip shape (normal shape or bottle shape), capillary length L
(For example, 9.5 mm or 11.1 mm or more) also changes the bonding condition. Here, FIG.
Has a normal tip and a taper angle θ
12 (b) shows the length L of the capillary, and FIG. 12 (c) shows the case where the tip of the capillary has a bottle shape.

The data table 13 shown in FIG. 2 includes the above-mentioned capillary chamfer diameter CD in addition to the wire diameter.
And various parameters corresponding to the type of the capillary.

As shown in FIG. 3, the capillaries 4 have various chamfer diameters and the like. That is, in FIG. 3, H is the hole diameter,
CD is the chamfer diameter, θ is the chamfer angle, D
Is the above-mentioned crimp diameter, and WD is the above-mentioned crimp thickness. FIGS. 4 to 11 show the data table 13.
Are stored and stored.

FIGS. 4 to 6 show parameters used when the chamfer diameter CD of the capillary 4 is about 70 μm or more (described as CD ≧ 70 μm).

First, FIG. 4 shows the relationship between the crimping diameter D (μm) on the horizontal axis and the relationship between the ultrasonic power on the vertical axis, obtained by equation (1). In this embodiment, the ultrasonic power is appropriately determined by, for example, dividing the power from the maximum value to the minimum value into 256 types, and therefore, the unit of the ultrasonic power is not determined. y = A ₁ x− {B ₁ − (C ₁ T + D ₁ )} (1) [x: ball pressing diameter, T: ball pressing thickness, A ₁ , B ₁ ,
C ₁ , D ₁ : constant] This is stored in the data table 13 as the first table.

FIG. 5 shows the relationship between the crimping diameter D on the horizontal axis and the ultrasonic application time (ms) on the vertical axis, obtained by equation (2). y = A ₂ x + B ₂ (2) [x: ball compression diameter, A ₂ , B ₂ : constant] This is stored in the data table 13 as a second table.

Further, FIG. 6 shows the compression diameter D on the horizontal axis and the load applied to the capillary 4 on the vertical axis, that is, the search load and the bonding load obtained by the equation (3). y = x−A ₃ (3) [x: ball pressure bonding diameter, A ₃ : constant]

As shown in FIG. 13A, the above-mentioned search load is caused by the capillary moving from a high speed to a low speed as shown in FIG.
As shown in (2), this is the load up to contact with the pad, which is obtained by multiplying the value of the bonding load obtained by equation (3) by a predetermined coefficient. The bonding load refers to a load from the search load to bonding as shown in FIG. These are stored in the data table 13 as a third table.

Next, FIGS. 7 to 9 show parameters used when the chamfer diameter CD of the capillary 4 is less than about 70 μm (described as CD <70 μm).

First, FIG. 7 shows the relationship between the crimping diameter D (μm) on the horizontal axis and the ultrasonic power on the vertical axis, as in FIG. y = A ₄ x− {B ₄ − (C ₄ T + D ₄ )} (4) [x: ball compression diameter, T: ball compression thickness, A ₄ , B ₄ ,
C ₄ , D ₄ : constant] This is stored in the data table 13 as the fourth table.

FIG. 8 shows the relationship between the crimping diameter D on the horizontal axis and the ultrasonic wave application time on the vertical axis, as in FIG. y = A ₅ x + B ₅ (5) [x: ball compression diameter, A ₅ , B ₅ : constant] This is stored in the data table 13 as a fifth table.

Further, FIG. 9 shows the crimping diameter D on the horizontal axis and the load applied to the capillary 4 on the vertical axis, that is, the search load and the bonding load, as shown in FIG. . The search load is obtained by multiplying the value of the bonding load by a predetermined coefficient. y = A ₆ x + B ₆ (6) [x: ball compression diameter, A ₆ , B ₆ : constant] This is stored in the data table 13 as a sixth table.

FIG. 10 shows the relationship between the ultrasonic power correction value and the pressure bonding thickness WD obtained by equation (7).
D represents the correction value (±) of the ultrasonic power on the vertical axis. y = A ₇ T + B ₇ (7) [T: ball compression thickness, y: ultrasonic power, A ₇ , B ₇ :
Constant] This is stored in the data table 13 as a seventh table.

FIG. 11 shows the correction data of the ultrasonic power with respect to the crimping diameter D according to the type of the capillary. Parameter shown in FIG. 11, for example, a material of the capillary is ceramic, the taper angle is 30 ^0, a tip shape is normal, further if the length of the capillary is 9.5mm and y _1, FIG. 11
In the table, y ₁ = Ax + B is stored as a group for each type of capillary with reference as a reference. Therefore, when the type of the capillary changes, y ₁ = Ax
In the reference indicated as + B, the constant of A is multiplied by M ₁ to obtain C (C = A × M ₁ ), and the constant of B is multiplied by N ₁ to obtain D (D = B × N _1). ), it is possible to obtain data relating to FIG. 11 in y _2, for example. Note that the reference constants A and B are set in advance as appropriate.

In this manner, the correction data indicated as y ₃ and y ₄ are sequentially read out as shown in FIG. 11 according to the type of the capillary, and this is finally multiplied by the ultrasonic power as a correction value. Configuration. These data are stored in the data table 13 as an eighth table.

Accordingly, in the above configuration, the keyboard 1
In step 1, the numerical value relating to the compression diameter D and the compression thickness WD of the bonding to be obtained, the numerical value of the chamfer diameter CD of the capillary 4 used for bonding, and the data relating to the type of the capillary are sequentially input, and the execution key is pressed. Then, the arithmetic circuit 12 receives this, and firstly, the chamfer diameter CD is equal to or more than about 70 μm (CD ≧ 70 μm) or the chamfer diameter CD is less than about 70 μm according to the numerical value of the inputted chamfer diameter CD. (CD
<70 μm). In the case of the former, the data table 13 shown in FIGS.
And the seventh to eighth tables shown in FIGS. 10 to 11.

The CPU reads out the ultrasound power data of the control signal p ₁ regarding corresponding to crimp diameter D which is specified by the first table shown in FIG. 4, also crimped diameter D which is specified by the second table shown in FIG. 5 Is read out, and the control signal f is read out on the pressure applied to the capillary 4 at the bonding point corresponding to the crimping diameter D specified by the third table shown in FIG. And the seventh shown in FIG.
A correction value of the ultrasonic power corresponding to the pressure bonding thickness WD specified by the table is read out, and the data of the control signal p ₁ read out by the first table in FIG. obtain a signal p _2.

Finally, a correction value for the crimping diameter D corresponding to the type of the capillary is read out according to the eighth table shown in FIG. 11, and the correction value is multiplied by the provisional control signal p ₂ to control the ultrasonic power. The signal p is obtained.

If the chamfer diameter CD inputted by the keyboard 11 is the latter, that is, CD <70 μm, the fourth to seventh tables shown in FIGS. refer.
The fourth to seventh tables can read out the control signals p ₁ , t, and f under the condition that the chamfer diameter CD is less than about 70 μm, similarly to the first to third tables. p ₁ is the same as in FIG.
Correction value read out by the seventh table shown in 0 is added, the control signal p ₂ provisional Ultrasonic power can be obtained. And reads the correction value for the crimped diameter D corresponding to the capillary type according eighth table shown in FIG. 11 as well (coefficient) relates to the multiplication to ultrasonic power the contrast control signal p ₂ of the temporary The control signal p is obtained.

The control signals p, t, f thus obtained
Is supplied to the ultrasonic control circuit 14, the switch circuit 15, and the pressurization control circuit 16 shown in FIG. 2 as described above, and applies a predetermined ultrasonic power to the ultrasonic vibrator 6 for a predetermined time. A predetermined pressure is applied to the capillary 4 and the set bonding is performed.

[0048]

As is apparent from the above description, according to the present invention, at least the data relating to the ball pressing diameter D, the pressing thickness WD, and the type of the capillary to be bonded are inputted and executed by the keyboard, and designated. The ultrasonic power, the ultrasonic application time, and the pressure applied to the capillary for automatically obtaining the formed bonding shape are automatically calculated, and a predetermined shape can be bonded to the bonding point by a control signal based on the calculation result. There is an effect that can be done. Therefore, it is possible to solve the problem that the bonding operation and the measurement operation are repeatedly performed in order to obtain the desired bonding shape of the crimping diameter D and the crimping thickness WD as in the related art.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a bonding head used in a wire bonding apparatus according to the present invention.

FIG. 2 is a block diagram illustrating an example of a circuit configuration for generating a control signal applied to the bonding head illustrated in FIG. 1;

FIG. 3 is a sectional view showing a state in which bonding is performed at a bonding point by a capillary.

FIG. 4 is a diagram showing the relationship between the crimping diameter and the ultrasonic power stored in the data table of FIG. 2;

FIG. 5 is a diagram showing the relationship between the pressure bonding diameter stored in the data table of FIG. 2 and the ultrasonic wave application time.

FIG. 6 is a diagram illustrating a relationship between a crimping diameter and a load stored in the data table of FIG. 2;

FIG. 7 is a diagram showing the relationship between the crimp diameter and the ultrasonic power stored in the data table of FIG. 2;

FIG. 8 is a diagram showing a relationship between a crimping diameter stored in the data table of FIG. 2 and an ultrasonic wave application time.

FIG. 9 is a diagram illustrating a relationship between a crimp diameter and a load stored in the data table of FIG. 2;

FIG. 10 is a diagram showing a relationship between a correction value of an ultrasonic power and a compression thickness stored in the data table of FIG. 2;

FIG. 11 is a diagram showing a relationship between an ultrasonic power correction coefficient and a type of capillary stored in the data table of FIG. 2;

12 (a) shows the normal shape and taper angle θ at the tip of the capillary, FIG. 12 (b) shows the length L of the capillary, and FIG. 12 (c) shows the tip of the capillary at the bottle It is a figure showing a shape.

FIGS. 13A to 13D are cross-sectional views illustrating a wire bonding process.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Drive arm 2 Bonding arm 3 Axis 4 Capillary 5 Ultrasonic horn 6 Ultrasonic oscillator 7, 7 'Contact 8, 8' Solenoid unit 9, 9 'Drive coil unit 10, 10' Detector 11 Keyboard execution switch 12 Operation circuit 13 Data table 14 Ultrasonic control circuit 15 Switch circuit 16 Pressurization control circuit

Claims (4)

(57) [Claims] 1. A wire bonding apparatus for bonding a wire to a bonding point by ultrasonic waves applied to a tip of a capillary, wherein at least the wire bonding apparatus is formed when the tip of the capillary is crimped to a bonding point. A keyboard for inputting and executing bonding shape data relating to the crimping diameter D and the crimping thickness WD and data relating to the capillary; and receiving at least the bonding shape data relating to the crimping diameter D and the crimping thickness WD and the data relating to the capillary inputted by the keyboard. Calculating means for generating a control signal relating to the ultrasonic power applied to the tip of the capillary at the time of bonding, an ultrasonic application time, and a control signal relating to the pressing force of the capillary at the bonding point, wherein the control signal output from the computing means is provided. Based on the ultrasonic power applied to the capillary tip, the wire bonding apparatus being characterized in that so as to control the pressure applied to the application time and the capillary. 2. The wire bonding apparatus according to claim 1, wherein the data relating to the capillary includes a wire diameter. 3. A wire bonding method for bonding a wire to a bonding point by ultrasonic waves applied to the tip of a capillary, wherein at least a crimping diameter D formed when the tip of the capillary is crimped to a bonding point by a keyboard. And input and execute the bonding shape data related to the pressure bonding thickness WD and the data related to the capillary, and output the calculated data to the calculating means, the control signal regarding the ultrasonic power applied to the tip of the capillary calculated by the calculating means, the ultrasonic application time, and the bonding point. A wire bonding method for bonding a wire to a bonding point based on a control signal relating to a pressure of a capillary applied to the wire. 4. The wire bonding method according to claim 3, wherein the data relating to the capillary includes a wire diameter.