JP2770094B2 - Bonding tool mounting state determination device and method for bonding device in bonding apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor integrated circuit (I).
C) and a bonding apparatus for assembling semiconductor components of a large-scale integrated circuit (LSI). In particular, in an ultrasonic bonding apparatus for performing bonding using ultrasonic waves, it is necessary to determine whether a bonding tool mounted on the apparatus is in a good or bad state. The present invention relates to a bonding tool mounting state determination device and a determination method thereof that can be automatically determined.

[0002]

2. Description of the Related Art In a conventional bonding apparatus, a plurality of I
A lead frame for wire bonding on which a C chip (semiconductor) is arranged in the longitudinal direction is intermittently fed one pitch at a time by a transfer means for transferring the lead frame in the longitudinal direction, and the sent lead frame is bonded by a heater block heated by a heater block. After being transferred onto the stage, the electrodes (pads) of the IC chip provided on the lead frame and the surrounding leads are bonded and connected by wires formed of aluminum wires or gold wires. As a bonding tool used in this bonding apparatus, one having a configuration as shown in FIG. 4 is known.

A bonding tool 21 shown in FIG. 4 includes an ultrasonic horn 22, an ultrasonic vibrator (electric-acoustic conversion element) 23, and a capillary 24 as a bonding tool.
It is composed of

The ultrasonic horn 22 has a straight horn portion 22a, a cylindrical flange portion 22b for mounting and fixing an ultrasonic vibrator (electric-acoustic conversion element) 23, and a distal end as shown in FIG. a conical portion 22c having a slit 22c ₁ formed longitudinally section, and the hole 22d formed on one side surface of the conical portion 22c for fastening and fixing the capillary 24, a screw screwed into the hole 22e.

The ultrasonic horn 22 is mainly formed of stainless steel or a titanium alloy. Although not shown, a pad on an IC chip having a large area such as a hybrid IC or a thermal head substrate and a lead frame are provided. In order to bond and connect the lead with the wire, the degree of freedom in moving the XY table (not shown) below the straight horn portion 22a and the relationship of a recognition device including a camera and the like arranged above are considered. About 3/2 wavelength (λ)
It consists of the length of the resonance mode. Here, the 3/2 wavelength (λ) resonance mode length is used when the frequency of the normally used ultrasonic wave is about 50 kHz to 100 kHz, for example, when the frequency is 60 kHz and the ultrasonic horn material is stainless steel. In this case, the axial length of the 3/2 wavelength (λ) is appropriately set to a length of about 125 mm.

The straight horn portion 22a has a cylindrical shape, and is located at a nodal point (nodal point of vibration of ultrasonic vibration) about 1 / 4λ from the end of the straight horn portion 22a. A cylindrical flange portion 22b having a large diameter is integrally formed. At the end of the straight horn portion 22a, a shaft (not shown) having a thread formed on the outer periphery is provided, and an ultrasonic vibration including a screw of this shaft and a bolted Langevin type vibrator for generating ultrasonic vibration. The child 23 is screwed and connected. The entire ultrasonic transducer to be connected is securely fixed to the main body head via the cylindrical flange 22b.

The conical portion 22c has a length of 2 / 2λ from the end of the straight horn portion 22a (hereinafter simply referred to as 2/2 λ).
/ 2λ) is formed in a conical shape toward the front. This conical section is the straight horn section 22
This is for increasing the vibration amplitude of the ultrasonic vibration transmitted by a, and its free end is tapered so that the capillary 24 can be easily attached.

The ultrasonic transducer 23 is connected to a connector 26 via lead wires 25a and 25b as shown in FIG.

In the bonding connection using the bonding tool having the above configuration, a lead frame on a bonding stage (not shown) having a heater block disposed on a lower surface is overheated, and the bonding tool is heated in the overheated state. The ball formed at the tip of the wire inserted into the capillary 24 by being moved in the vertical direction by a drive mechanism (not shown) or the like is crushed to the electrode (pad) of the IC chip and overheat-pressed. Ultrasonic vibration is applied from the ultrasonic horn 22 simultaneously with the crushing. These steps are all performed on each chip and lead to complete a series of bonding steps.

[0010]

However, in the bonding tool 21 having the above-described structure, the length of the resonance mode is accurately determined due to the transmission of the ultrasonic vibration, and the positioning with the accuracy of the order of microns is performed. Therefore, precise processing is required. After the mounting of the precision-bonded tool to the apparatus, it is not possible to check whether or not the tool is properly mounted in that state. Only by visually confirming the bonding state can the quality judgment be made. Therefore,
Such a temporary bonding connection must be performed for each device, and the determination must be made by visual inspection.

In addition, a hybrid IC is provided by a conventional device.
When performing bonding connection of an IC having a large area such as a thermal head substrate or the like, the overheated area is widened, the ambient temperature is higher than when the area is small, and the bonding tool 21 is XY. It is driven in the X and Y directions by a table, and in the vertical direction (Z
(Axial direction) so that it can move between a place where the ambient temperature is high and a place where the ambient temperature is low. Therefore, even when the bonding tool 21 is precisely and precisely processed, the ultrasonic horn 22 may expand and contract due to thermal expansion due to the influence of the ambient temperature. Therefore, even if a good result is obtained when the bonding connection is experimentally performed, a good result may not be obtained during the actual bonding.
The automatic bonding apparatus has a drawback that many bonding failures occur because bonding connection is made to a large number of parts to be bonded in a short time. Therefore, the conventional apparatus has a drawback in that it is not possible to immediately determine a defect in the bonding tool itself or a defect in a state of attachment to the apparatus.

In view of the above, the present invention has been made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a bonding tool mounting apparatus capable of automatically judging the mounting state of a bonding tool without actually performing temporary bonding connection. An object of the present invention is to provide a state determination device and a determination method thereof.

[0013]

According to the present invention, there is provided a bonding tool having a capillary attached to a tip thereof, an ultrasonic vibrator for transmitting ultrasonic vibration to the tool, and applying an ultrasonic wave to the ultrasonic vibrator. a bonding apparatus having an ultrasonic generator, the prior SL ultrasonic generator, and operation control means, and storage means comprises a frequency generation means, and a current detection means, from said arithmetic control means The frequency is varied from before and after including the resonance frequency by the instruction to generate the ultrasonic vibrator by exciting the ultrasonic vibrator, and the current value for each of the varied frequencies is detected by the current detecting means and stored as data. Means, a resonance frequency is obtained from the stored data to calculate a selectivity Q ₀ ,
By comparing this with the selectivity Q stored in the storage means in advance, it is possible to determine whether the mounting state of the bonding tool is good or not. Further, the present invention is a bonding apparatus having the above configuration, wherein the ultrasonic generator is configured to generate a variable frequency before and after including a resonance frequency by a frequency generating unit and to excite the ultrasonic transducer. , The resonance frequency is calculated, the impedance at the resonance frequency is calculated, and the impedance is stored in the storage means in advance, and the quality of the mounting state of the bonding tool can be determined. A bonding tool mounting state determination method according to the present invention includes a bonding tool having a capillary attached to a tip thereof, an ultrasonic vibrator for transmitting ultrasonic vibration to the tool, and an ultrasonic vibrator for applying ultrasonic waves to the ultrasonic vibrator. A sound wave generator, wherein the ultrasonic wave generator has an operation control unit, a storage unit, a frequency generation unit, and a current detection unit. The ultrasonic vibrator is excited by generating a variable frequency before and after including the frequency, and the current value for each of the changed frequencies is detected by the current detecting means and stored in the storage means as data. It was seeking resonant frequency to calculate the selectivity Q ₀ from the data, bonding by comparing the selectivity Q stored in advance in the storage means and this Tsu In this case, it is possible to judge the quality of the mounted state of the tool. Also, in the bonding tool mounting state determination method according to the present invention, the ultrasonic generator may generate a variable frequency over a frequency including and including a resonance frequency by a frequency generation unit, and excite the ultrasonic vibrator to generate a resonance. By determining the frequency, calculating the impedance at the resonance frequency, and comparing the impedance with the impedance stored in advance in the storage means, it is possible to determine whether the bonding tool is properly mounted. Further, in the bonding tool mounting state determination method according to the present invention, the ultrasonic generator includes an arithmetic control unit, a storage unit, a frequency generation unit, and a current detection unit, and a command from the arithmetic control unit. By oscillating the ultrasonic vibrator by generating a variable frequency around the resonance frequency including and including the resonance frequency from the frequency generation means, a resonance frequency is obtained, and a frequency near the obtained resonance frequency is precisely measured again. Then, the true resonance frequency is obtained.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. Since the bonding tools shown in FIGS. 4A and 4B have the same configuration and function in this embodiment, they will be described using the same reference numerals, and detailed description will be omitted.

FIG. 1 is a diagram showing a circuit configuration of an ultrasonic generator of a bonding tool mounting state determining apparatus according to the present invention.

In FIG. 1, an ultrasonic generator 1 includes a CPU 2 as arithmetic control means, a memory 3 as storage means, a frequency generator 4 as frequency generating means, and a current detector 5 as current detecting means. , Amplifier 6 and A / D
And a converter 7.

The frequency generator 4 converts the digital data output from the CPU 2 into analog data by the D / A converter 4a, and converts the frequency set by the oscillating unit 4b by the amplifier 4c based on the data into a constant voltage. Amplify and output. The frequency oscillated by the oscillation section 4b is CP
The frequency can be varied and output according to the command from U2. This specific method will be described later. Therefore, the frequency generator 4 can oscillate while changing the frequency at a constant voltage. Frequency output by the frequency generator 4 is applied via the connector 26 shown in the terminal S ₁ and 4 (b) to the ultrasonic transducer 23. Then, the ultrasonic vibrator 23 is excited to transmit ultrasonic vibration to the bonding tool 21. As shown in FIG. 4, the ultrasonic vibration is performed in a state where bonding is not actually performed, that is, in a state where the ultrasonic vibration is attached to a supporting frame (not shown) of the bonding apparatus.

The bonding tool 21 is data in a state of being excited by applied ultrasonic vibration is detected by the current detector 5 through the terminal S ₂ shown in connector 26 and 1 shown in Figure 4 (b). The current detector 5 is formed of a resistor or the like, and is grounded. The resistance value is stored in advance in the memory 3 shown in FIG. 1 as data by an external operation means. The current detected by the current detector 5 is converted into digital data by an A / D converter 7 through an amplifier 6 and input to the CPU 2.
The CPU 2 reads out the input data and basic frequency data stored in the memory 3 in advance, compares them, and determines whether or not the frequency characteristics are good.

Next, a method of determining the mounting state of the bonding tool using the ultrasonic generator 1 will be described in detail. FIG. 2 is a diagram illustrating the relationship between frequency and current when the bonding tool 21 driven by the ultrasonic generator 1 is mounted on the bonding device. FIG. 3 is a flowchart showing a case where the bonding tool mounting state is determined using the apparatus shown in FIG.

First, the memory 3 shown in FIG. 1 has good frequency characteristics, that is, P
As shown by, the fundamental frequency characteristic P centered on the resonance frequency f ₀ and the selectivity Q are set in advance and stored. The setting of the basic frequency characteristic P and the selectivity Q is performed by measuring the optimum data when the bonding tool 21 is actually mounted and bonded by using an external device or the like and storing the data in the memory 3, or A method may be used in which the most suitable data in the range measured using the method described in the embodiment is stored as data, and the values measured by the same method are relatively compared. Further, as shown in FIG. 2, the fundamental frequency characteristic P may be a method of storing a sampled value as long as there is continuity, or any other method that can store optimal data. Also, in the memory 3,
As shown by P in FIG. 2, a method of storing the above-described basic frequency characteristics and the selectivity Q may be used, but a certain width as shown by Ph and Pl is set and stored, and Ph and P are stored.
If it is within the range of l, it can be determined that it is a practical range. In this manner, the basic frequency characteristics and the selectivity Q for determining whether the bonding tool is mounted or not are set in the memory 3.

Next, the bonding tool 21 shown in FIG.
The ultrasonic generator 1 shown in FIG. 1 is driven by an operation of an external operation means in a state where is mounted on the bonding apparatus. The driving of this device may be configured to be automatically driven by the operation of the bonding device. As shown in FIG. 3, when the device shown in FIG. 1 is driven, the CPU 2
It operates according to a predetermined program.

[0022] Now, it is a start S ₀ indicating this state is shown in FIG. 3. Then, as is apparent from FIG. 2, the resonance frequency f ₀
In this case, the impedance becomes minimum, and the resonance current I ₀ becomes maximum. Thus, the CPU 2 outputs the frequency data (f ₀
-.DELTA.f) Setting Step S _1. The set frequency data (f ₀ −Δf) is instructed to the frequency generator 4.

Next, in step _{S 2,} the frequency generator 4
The frequency of (f ₀ −Δf) is set to a constant voltage by the oscillation unit 4b of
And the current value at that time is stored in the memory 3. So
To, bonding tool 1 drives the ultrasonic transducer 23 shown in FIG. 4 from the terminal S ₁ by the amplified frequency at constant voltage is excited by ultrasonic vibration. The frequency output from the frequency generator 4 is time-controlled by the clock of the CPU 2 and output. The time is appropriately set in consideration of the time required for the bonding tool 21 to sufficiently follow and resonate. The resonance current I is detected by the current detector 5 while the bonding tool 21 is excited by the frequency. The detected value is converted into digital data by the A / D converter 7 and stored in the memory 3.

[0024] Next, the process proceeds to step _{S 3,} CPU2
Is a frequency f set in advance to the frequency (f ₀ −Δf).
_The frequency data obtained by adding ₁ is instructed to the frequency generator 4. Frequency generator 4, excite the bonding tool 21 by applying the set frequency in the step S ₂ of the step as well as the ultrasonic transducer 23. The excited resonance current I of the bonding tool 21 is detected and sequentially stored in the memory 3.

[0025] Then, in step S _4, determines whether the frequency f is in the f = (f ₀ + Δf) by CPU 2. In step _{S 4, f = (f 0} +
If not Δf), that is, if N (No), step S ₃
Return to In step S _3, continue to shift to the frequency data is (f ₀ + Δf) by adding predetermined frequency f ₁ after another at regular intervals in accordance with a command from the CPU 2, the resonance by the respective frequency data Current I
Is stored in the memory 3.

[0026] The frequency data in step S ₄ is (f ₀ + Δ
If f), that is, if Y (Yes), step S ₅
Move to The CPU 2 sends the frequency (f ₀ −
The data from Δf) to (f ₀ + Δf) is read out, and the maximum value I of the resonance current is obtained from the data stored in the memory 3.
₀ and the resonance frequency f ₀ . Then, the selectivity Q ₀ is calculated and obtained using a known formula set in the CPU 2.

Next, by comparing the selectivity Q as a reference that is previously stored in the selectivity Q ₀ and the memory 3 obtained in step S ₅ in step S _6, the determination of the quality of the bonding tool mounted state I do. When the obtained value of the selectivity Q ₀ is higher than the reference selectivity Q, that is, when the waveform has a waveform close to the resonance frequency f ₀ , the mounting state is good.

If the above determination is made, step S
_{The process} ends (END) assuming that a series of determinations are completed in ₇ . Upon completion of this, the bonding apparatus determines that the mounting state of the bonding tool is negative according to the above determination result.
Based on a command from the CPU 2, it is possible to notify that there is some abnormality by, for example, issuing an external display or issuing an alarm. Accordingly, it is possible to know by a simple method that there is an abnormality in the mounting of the bonding tool 21 by this notification, so that it is possible to take prompt measures such as emergency measures.

By the way, according to the above description, the case where the fundamental frequency characteristic P and the selectivity Q are stored in the memory 3 has been described. However, it is good to make a determination centering on the resonance frequency f ₀ , but if the main resonance and the sub-resonance occur as shown in FIG.
In some cases, it may not be possible to make a sufficient determination by only using the factor of (1). Therefore, as shown by Ph and Pl, a width having an upper limit and a lower limit with the basic frequency characteristic P interposed therebetween is arbitrarily set and stored, and if it is within the range of Ph and Pl, there is no abnormality in the mounting state of the bonding tool 21. By performing the determination as described above, it is possible to determine the quality of the mounted state even when the sub-resonance occurs as shown in FIG. In setting the Ph and Pl data, some specific frequencies as samples may be selected and stored, and compared with these values. FIG. 5 shows free admittance characteristics using the bonding tool 21 shown in FIG.

In this embodiment, the resonance frequency f ₀ is obtained by the method shown in FIG. 3. By re-measuring the vicinity of the obtained resonance frequency f ₀ precisely again, the true resonance frequency f ₀ is obtained. You can also do so.

Further, in this embodiment, the case where the current value at the time of resonance is measured is described. However, the impedance at the resonance frequency f ₀ is stored in the memory 3 in advance, and the bonding tool 21 shown in FIG. The impedance at resonance is C
By calculating with PU2 and comparing with this,
The state of attachment of the bonding tool may be determined.

[0032]

As described above, according to the present invention, it is possible to judge the quality of the mounted state without performing the temporary bonding with the bonding tool mounted on the bonding apparatus. Further, according to the present invention, even during bonding, there is an effect that the quality of the mounted state can be automatically determined by a simple method in a state of being mounted on the apparatus. Therefore, the quality of the mounting state of the bonding tool can be easily determined,
There is an effect that work efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of an ultrasonic generator of a bonding tool mounting state determination device according to the present invention.

FIG. 2 is a diagram illustrating a relationship between a frequency and a current when a bonding tool driven by the ultrasonic generator illustrated in FIG. 1 is mounted on the bonding device.

FIG. 3 is a flowchart showing a case where a bonding tool mounting state is determined using the apparatus shown in FIG. 1;

FIG. 4 is a diagram showing a conventional bonding tool and a state in which an ultrasonic vibrator is attached to the tool.

FIG. 5 is a diagram illustrating an example of a measurement result of a free admittance characteristic of the bonding tool illustrated in FIG. 4;

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic generator 2 CPU 3 Memory 4 Frequency generator 5 Current detector 6 Amplifier 7 A / D converter 21 Bonding tool 22 Ultrasonic horn 23 Ultrasonic transducer 24 Capillary 26 Connector

Claims (8)

(57) [Claims] 1. A bonding tool having a capillary attached to a tip thereof, an ultrasonic vibrator for transmitting ultrasonic vibration to the tool, and an ultrasonic generator for applying ultrasonic waves to the ultrasonic vibrator. A bonding apparatus, wherein the ultrasonic generator includes an arithmetic control unit, a storage unit,
Frequency generating means, and a current detecting means, wherein the frequency is varied from before and after including a resonance frequency from the frequency generating means by a command from the arithmetic and control means to generate a variable frequency to excite the ultrasonic transducer, and a variable current value of each frequency detected by the current detection means and stored in the storage means as data, from this stored data in search of the resonance frequency to calculate the selectivity Q _0, which as previously storing means in the storage A bonding tool mounting state determining device for determining whether the mounting state of the bonding tool is good or not by comparing the selected degree of selection Q. 2. The storage device according to claim 1, wherein said storage means can store frequency characteristic data having an arbitrary upper limit and lower limit with respect to the fundamental frequency characteristic data.
2. The bonding tool mounting state determination device according to claim 1. 3. A bonding tool having a capillary attached to a tip thereof, an ultrasonic vibrator for transmitting ultrasonic vibration to the tool, and an ultrasonic generator for applying ultrasonic waves to the ultrasonic vibrator. A bonding apparatus, wherein the ultrasonic generator generates a resonance frequency by generating a variable frequency before and after including the resonance frequency by a frequency generation unit to excite the ultrasonic vibrator, thereby obtaining a resonance frequency. Calculate the impedance,
A bonding tool mounting state determination device, wherein the quality of the mounting state of the bonding tool can be determined by comparing the impedance with an impedance stored in a storage unit in advance. 4. A bonding tool having a capillary attached to a tip thereof, an ultrasonic vibrator for transmitting ultrasonic vibration to the tool, and an ultrasonic generator for applying ultrasonic waves to the ultrasonic vibrator, The ultrasonic generator includes an arithmetic control unit, a storage unit,
Frequency generating means, and a current detecting means, wherein the frequency is varied from before and after including a resonance frequency from the frequency generating means by a command from the arithmetic and control means to generate a variable frequency to excite the ultrasonic transducer, and a variable current value of each frequency detected by the current detection means and stored in the storage means as data, from this stored data in search of the resonance frequency to calculate the selectivity Q _0, which as previously storing means in the storage A method of determining the mounting state of the bonding tool, wherein the quality of the mounting state of the bonding tool can be determined by comparing the selected degree of selection Q. Wherein said frequency generating means, according to claim 4 bonding tool mounted state determination method according to, characterized in that to be able to occur by varying the frequency at constant voltage. 6. The memory device according to claim 1, wherein said storage means is capable of storing frequency characteristic data having an arbitrary upper limit and lower limit with respect to fundamental frequency characteristic data.
The bonding tool mounting state determination method according to claim 4 or 5 . 7. A bonding tool having a capillary attached to a tip thereof, an ultrasonic vibrator for transmitting ultrasonic vibration to the tool, and an ultrasonic generator for applying ultrasonic waves to the ultrasonic vibrator, The ultrasonic generator, by generating a variable frequency over and around the resonance frequency including the resonance frequency by the frequency generation means to excite the ultrasonic transducer, determine the resonance frequency, calculate the impedance at the resonance frequency,
A bonding tool mounting state determination method, wherein the quality of the mounting state of the bonding tool can be determined by comparing the impedance with the impedance stored in the storage means in advance. 8. A bonding tool having a capillary attached to a tip thereof, an ultrasonic vibrator for transmitting ultrasonic vibration to the tool, and an ultrasonic generator for applying ultrasonic waves to the ultrasonic vibrator, The ultrasonic generator includes an arithmetic control unit, a storage unit,
By having a frequency generating means and a current detecting means, and by changing the frequency before and after including the resonance frequency from the frequency generating means by a command from the arithmetic control means to generate and excite the ultrasonic vibrator, And determining a resonance frequency, and precisely measuring a frequency near the determined resonance frequency again to determine a true resonance frequency.