JPH1164303A - Ultrasonic inspection method for joint of electronic parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To nondestructively discriminate the joining states of minute junctions of electronic parts from the reflected waves of ultrasonic waves transmitted to the junctions. SOLUTION: An ultrasonic pulse transmitted from an ultrasonic oscillator 3 is transmitted to the junction of electronic parts through an electronic parts joining tool 4, and ultrasonic waves reflected from the tool 4 are received. Then the difference between the peak output voltage of the detected waveform and amplitude obtained by converting the received ultrasonic waves, and the peak output voltage of the detected waveform and amplitude of ultrasonic waves reflected from the tool 4 measured while the tool 4 is not in contact with the junction before joining the junction, is computed. Thereafter, the computed difference is compared with a curve indicating the relation between the voltage difference and peel strength, and the peel strength of the junction is estimated from the deviation of the computed difference from the curve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a reflected wave of an ultrasonic wave transmitted from an ultrasonic oscillator from a micro-joined part of an electronic component to determine a good joining condition in a preliminary experiment before processing when determining good joining conditions. The present invention relates to an ultrasonic inspection method for a joint of electronic components used for inspection, monitoring and inspection of a joining state during joining, inspection after joining of joined products, and the like.

[0002]

2. Description of the Related Art The quality of a micro-joined part of an electronic component affects the reliability and productivity of a product. Therefore, in the conventional micro-joining, preliminary experiments are performed in advance to maintain a good joining state, and good joining conditions are obtained. After determining the proper processing has been performed. In addition, to monitor the bonding state during proper processing, the bonded product is extracted, the joint is pressed with a shearing tool to determine the bonding state based on the load when the joint breaks, and the bonded metal in wire bonding Pull test to determine the bonding state from the position where the wire breaks by hooking a wire such as a wire on the hook,
A method in which a cross section is observed with a microscope by shaving a joint portion is widely used.

[0003]

However, the strength test by the pull test and the push test and the microscopic observation of the bonding interface, which have been conventionally used for preliminary experiments, sampling tests for quality control and productivity enhancement, are not performed by the bonding. This is a test method that destroys the part, and there is a problem that the inspected product cannot be used as a product. In addition, a skilled worker is required to make an accurate determination in the inspection, and a long time is required until a determination result is obtained.

[0004] The inventor of the present invention has conducted many experiments and studies for the purpose of solving such problems, and as a result, has found that a joining tool for applying a load or vibration for joining electronic components to a micro joining portion has been developed. By gluing the ultrasonic oscillator and using the joining tool as a transmission medium of the ultrasonic wave transmitted from the ultrasonic oscillator, the ultrasonic waves are concentrated and transmitted to the micro area of the electronic component micro-joining, and from the micro-joining part Reflected,
Compare the amplitude of the received reflected wave with the amplitude of the normal state,
It has been found that an abnormal joining state can be determined nondestructively. In addition, since the micro-joining tool to which the ultrasonic oscillator, which is the ultrasonic transmitter / receiver, is attached, can be directly mounted on the micro-joining machine, the abnormal joining state during joining is monitored by using the amplitude of the reflected wave during the joining process. I learned that I can do it.

[0005]

SUMMARY OF THE INVENTION The present invention has been made on the basis of such knowledge, and the gist of the present invention is that an ultrasonic pulse transmitted from an ultrasonic oscillator is transmitted to an electronic component through an electronic component joining tool. The peak output voltage of the detected waveform amplitude that is transmitted to the joint and reflected and received and converted, and the ultrasonic wave reflected from the welding tool measured in a separated state where it is not in contact with the joint before welding Calculate the difference between the detected waveform amplitude and the peak output voltage, and compare it with the voltage difference-peeling strength relationship line based on the bonding state in the normal state set in advance to determine the peeling strength of the joint from the deviation. This is an ultrasonic inspection method for an electronic component joint to be estimated.

According to the present invention, the peak output voltage of the detected waveform amplitude of the reflected wave from the joining tool in the separated state in which the electronic component joining tool before the inspection is not in contact with the joint in the sampling inspection is provided. If the difference between the detected waveform amplitude of the reflected wave during the inspection in which the electronic component joining tool is in contact with the joint and the peak output voltage is obtained, this is also an inspection method that can be used for sampling inspection.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is provided for easy understanding of the present invention, and shows an embodiment of an ultrasonic inspection method according to the present invention. In FIG. 1, reference numeral 1 denotes a member to be joined to an electronic component, on which a micro joining member 2 is joined. 3 is an ultrasonic oscillator. The ultrasonic oscillator 3 oscillates ultrasonic pulses of various frequencies and receives reflected ultrasonic waves. The ultrasonic oscillator 3 is bonded to the electronic component bonding tool 4. The ultrasonic pulse transmitted from the ultrasonic oscillator 3 is transmitted to the joint of the electronic component joined member 1 via the electronic component joining tool 4. The electronic component joining tool 4 applies a load force (joining load), vibration, and the like necessary for joining the electronic component workpiece 1 and the micro joining member 2 to the micro joining member 2.
A tool that applies bonding load and vibration to gold and aluminum wires, which are bonding members for wire bonding, and a TAB that bonds to integrated circuit components (chips)
Tools such as a bonding head for applying a bonding load to the tape and a pressure head for applying a load to the soldered portion of the electronic component are used. That is, the ultrasonic pulse transmitted from the ultrasonic oscillator 3 is transmitted to the electronic component bonded member 1 via the electronic component bonding tool 4 and receives the reflected ultrasonic wave.

Reference numeral 5 denotes an ultrasonic measuring device. The ultrasonic measuring device 5 has a function of outputting an electric pulse for causing the ultrasonic oscillator 3 to oscillate an ultrasonic wave or amplifying and outputting an electric signal of a reflected wave received and converted by the ultrasonic oscillator 3. It is. The ultrasonic measuring device 5 includes a pulser 6 for controlling the timing of outputting an electric pulse signal for causing the ultrasonic oscillator 3 to oscillate ultrasonic waves and a magnitude of the electric pulse signal, and a reflected wave converted by the ultrasonic oscillator 3. 7, a gate 8 having a function of setting a specific time zone to be detected from the output of the electric signal of the reflected wave amplified by the receiver 7 and the electric signal of the reflected wave.
And a peak detector 9 that outputs a peak voltage of the detected waveform amplitude in a specific time zone set by the above.
In the present invention, an ultrasonic measuring device 5 that has been conventionally developed may be used. The use of the output terminal of the ultrasonic measurement device 5 enables the following measurement. (1) Received and converted by the ultrasonic oscillator 3, and the receiver 7
The electric signal of the reflected wave from the joint of the electronic components amplified by the above and the electric pulse signal of the pulser 6 used for transmitting the ultrasonic oscillator 3 are outputted from the waveform output terminal of the gate 8 and the pulser 6 When the trigger signal output from the output terminal is connected to the oscilloscope 10, the received reflected wave can be observed. (2) The reflected wave received by the ultrasonic oscillator 3 includes the reflected wave from the joining boundary surface between the electronic component joined member 1 and the macro joined member 2. When a time zone in which a reflected wave appears from the joining boundary surface between the electronic component member-to-be-joined 1 and the macro-joining member 2 is set by the gate 8, a rectangular wave electric signal to which a constant voltage is applied only in that time zone is output from the gate 8 to the peak detector. 9
Sent to From the square wave electric signal and the electric signal of the reflected wave amplified by the receiver 7 and passed through the gate 7, the peak detector 9 detects the peak voltage of the detected waveform amplitude in the set time zone, and outputs from the output terminal of the peak detector 9. The output signal is used to evaluate the electronic component micro-joint.

Reference numeral 11 denotes a personal computer. The personal computer 11 calculates the difference between the peak voltages of the detected waveform amplitudes before and during joining output from the peak detector 9 and compares them with a preset voltage difference / peeling strength relation curve to estimate the peeling strength of the joint. And an abnormal joining state is determined. Display 1 for estimation and judgment results
2 and output to the printer 13 if necessary.

The ultrasonic inspection method of the present invention in the above-described measuring apparatus will be described in detail. FIG. 2 is an explanatory diagram showing a path in which ultrasonic waves transmitted from the ultrasonic oscillator 3 during the welding are transmitted to the micro-joining portion via the electronic component joining tool 4 and reflected. In FIG. 2, the ultrasonic oscillator 3 is bonded to an electronic component joining tool 4. The ultrasonic wave transmitted from the ultrasonic oscillator 3 during the bonding propagates through the electronic component bonding tool 4 and is partially reflected at the contact interface between the micro-joining member 2 and the electronic component bonding tool 4, and The remaining transmitted ultrasonic wave propagates through the micro-joining member 2 and is reflected at the joining boundary surface between the micro-joining member 2 and the electronic component-joined member 1, and further transmitted through the electronic component-joined member 1. The light is reflected by the bottom surface of the electronic component material 1. These reflected waves propagate through the electronic component bonding tool 4 used in the transmission, and the receiver 3 is the same element as the ultrasonic oscillator 3.
Is received. The reflected wave reflected at the contact interface between the electronic component joining tool 4 and the micro joining member 2 and the reflected wave reflected from the joining boundary surface of the micro joining member 2 and the bottom surface of the electronic component joined member 1 are reciprocating time intervals. Is short, the reflected wave received by the receiver 3 is a reflected wave in which the reflected waves reflected from the contact interface, the junction boundary surface, and the bottom surface of the electronic component overlap.

Before the joining, since the electronic component joining tool 4 and the micro joining member 2 are not in contact with each other, the ultrasonic wave transmitted from the ultrasonic oscillator 3 is only a reflected wave from the lower end of the electronic component joining tool 4. The reflected waves that appear and are received do not include the reflected waves from the bonding interface of the micro bonding member 2 or the bottom surface of the electronic component bonded member 1. The bonding state of the micro bonding member 2 is included in the reflected waves from the bonding boundary surface of the micro bonding member 2 and the bottom surface of the electronic component bonded member 1, and the time when these reflected waves appear is determined by the time of the micro bonding tool 4. Because it differs depending on the length and the electronic component to be joined 4 to be measured,
Measure in advance to find the time zone.

In the ultrasonic inspection method of the joint of electronic parts, first, a reflected wave from the tip of the micro joining tool 4 before joining is measured, and then a reflected wave during joining is measured. Receiver 7
The respective reflected waves amplified before and during the joining can be observed on the oscilloscope 10 as the output signal of the gate 8 by using the trigger signal from the output terminal of the pulser 6. Further, when a time zone in which the reflected wave from the bonding boundary surface of the micro-joined member 2 and the bottom surface of the electronic component-joined member 1 is measured which is measured in advance using the gate 8 is set, the gate 8 having a constant voltage only in the set time zone. The peak output voltage of the detected waveform amplitude in the set time zone is output from the output terminal of the peak detector 9 from the square wave electric signal from the receiver and the electric signal of the reflected wave amplified by the receiver 7 and is input to the personal computer 11. . The personal computer 11 calculates the difference between the peak output voltage before joining and during the joining, compares the peak output voltage with a preset voltage difference / peeling strength relationship curve, estimates the joining strength, and determines whether the estimated joining strength is normal. In the case where the peel strength is less than or equal to the peel strength, it is determined that the joint is abnormal. Since the voltage difference / peeling strength relation curve used for the judgment differs depending on the material and shape of the micro joining tool to be used, it is measured in advance for each micro joining tool to be used. The output voltage difference, the estimated value of the peel strength, and the determination result of the bonding state are displayed on the display 12 and can be output to the printer 13 if necessary. This measuring method can be applied not only to the measurement during the micro-joining but also to the sampling inspection of the joined electronic parts after the micro-joining.

In the sampling inspection, the measurement in the separated state where the electronic component joining tool 4 is not in contact with the micro joining member 2 before the inspection is the measurement before joining, and the electronic component joining tool 4 is connected to the micro joining member 2 before the inspection. The state during the inspection that is in contact is the measurement during the bonding, and the processing and determination of the measurement result can use the same method as the processing and the determination during the micro bonding.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a sampling inspection of a wire bonding portion will be described below with reference to the drawings. 2 is a ceramic capillary having a diameter of 1.5 mm and a length of 11.3 mm. The ultrasonic oscillator 3 has a diameter of 6 mm.
A probe having a frequency of 20 MHz is used. The micro joining member 2 is formed by joining a gold wire having a diameter of 25 μm on an IC chip, and the diameter of the joining portion is about 100 μm. FIG. 3 is a diagram showing a measurement example of a reflected wave from the wire bonding portion measured by pressing the bonding tool (capillary) 4 for wire bonding against the micro-joining portion 4 of the gold wire with a measurement load of 60 g. The reflected wave is reflected at the contact interface between the wire bonding joining tool (capillary) 4 and the gold wire micro-joining member 2, the gold wire micro-joining member 2 and the electronic component bonding material (IC chip) 1. The reflected waves reflected from the bonding boundary surface and the bottom surface of the electronic component bonded member (IC chip) 1 are detected in an overlapping manner. The reflected wave reflected from the bonding boundary surface of the gold wire micro bonding member 2 including the bonding state of the gold wire and the electronic component bonded material (IC chip) 1 and the bottom surface of the electronic component bonded member (IC chip) 1 are 2 .4
Appears in a time zone of .about.2.6 .mu.s, and this time zone is used as the time zone of the detected waveform by using the gate 8. FIG. Since the peak voltage of the detected waveform amplitude in the time zone of 2.4 to 2.6 μs is output to the output terminal of the peak detector 9, the bonding tool (capillary) 4 for wire bonding is measured using the gold bonding member 2. Is performed during the sampling inspection in which the wire is not in contact with the wire bonding tool (capillary) 4 and the gold wire micro-joining member 2, and the peak output voltage of each detected waveform amplitude is transmitted to the personal computer 11. Is entered. Personal computer 11
Calculates the difference between the output voltage when the wire bonding tool (capillary) 4 is in contact with the gold wire micro-joined part 2 and the state when the wire tool is not in contact with the gold wire micro-joined part 2. The peeling load is estimated by comparing with the relationship of the peeling load in.

FIG. 4 shows the relationship between the difference between the output voltage when the bonding tool (capillary) 4 for wire bonding is in contact with the gold wire micro-joining part 2 and the state where it is not in contact with the peeling load in the push test. It is a figure showing an example of the result of having measured beforehand using a 1.5-mm and 11.3-mm-length ceramic capillary. Bonding tool (capillary) for wire bonding used in FIG.
In the case of No. 4, when the voltage difference is 0.08 V or more, the peeling load is 60
g or more, indicating a normal bonding state.
If the voltage difference due to the amplitude of the reflected wave is 0.08 V or less, it is determined that the connection is abnormal, and the defective product can be estimated from the voltage difference.

[0016]

As described above, the present invention utilizes the electronic component joining tool as an ultrasonic transmission medium, sends ultrasonic waves to the micro joining member via the electronic component joining tool, and joins the joining surface of the micro joining member. In order to propagate the ultrasonic wave reflected in the electronic component bonding tool and receive the ultrasonic wave, a diameter of about 100 mm
Measurement of a micro area of μm is enabled. Also, since the micro-joining tool to which the ultrasonic oscillator is bonded is incorporated into the micro-joining machine for measurement, the measurement can be performed during the joining process. Measure the relationship between the peak voltage difference of the detected waveform amplitude and the peel strength from the received bonding interface or the bottom of the electronic component and the peel strength in advance, and use the voltage difference / peel strength relationship curve to calculate the peel strength from the peak voltage of the detected waveform. It can be estimated non-destructively, and an abnormal state can be determined by comparing with a voltage change in a normal junction state. This inspection method can also be used for sampling inspection during micro-joining or after completion of joining, and it becomes possible to monitor the micro-joined portion during the joining process and control joining conditions during joining. Therefore, in the present invention, there is no need for quality evaluation by a strength test such as a pull test or a push test or a microscope observation of an interface when determining good bonding conditions.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a configuration of the present invention in one embodiment in which the present invention is applied to an electronic component joint.

FIG. 2 is an explanatory diagram showing a path where ultrasonic waves transmitted from an ultrasonic oscillator bonded to an electronic component bonding tool are reflected at an electronic component bonding portion.

FIG. 3 is a diagram showing a measurement example of a reflected wave from a wire bonding unit.

FIG. 4 is a diagram showing an example of a relationship between a peak output voltage difference of a detected waveform amplitude and a peeling load in a sampling inspection of a wire bonding portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic component joining member 2 Micro joining member 3 Ultrasonic oscillator 4 Joining tool 5 Ultrasonic measuring device 6 Pulser 7 Receiver 8 Gate 9 Peak detector 10 Oscilloscope 11 Personal computer 12 Display 13 Printer

Claims (1)

[Claims] An ultrasonic pulse transmitted from an ultrasonic oscillator is transmitted to a joint of an electronic component via an electronic component joining tool, and a detection waveform obtained by receiving and converting an ultrasonic wave reflected from the joint is received. Calculate the difference between the peak output voltage of the amplitude and the peak output voltage of the detected waveform amplitude of the ultrasonic wave reflected from the welding tool measured in a state where it is not in contact with the joint before welding, and set it in the normal state set in advance. An ultrasonic inspection method for a joint part of an electronic component, comprising comparing a voltage difference / peeling strength relation line based on a joining state of the electronic part and estimating a peel strength of the joint part from an amount of deviation.