JPH0257968A - Ultrasonic inspection device - Google Patents

Abstract

PURPOSE:To ensure checking of peeling even if water is present at a peeled position by operating and judging the difference in positive peak values of the reflected wave signals at a bonded part which are obtained with two probes having a low frequency and a high frequency. CONSTITUTION:This apparatus is composed of probes 6H and 6L, a switch 15, a gate 11', a detector 16, an A/D converter 17, a switch 18, a memory 19, a subtractor 20, a judging device 21 and an attenuator 22. The probe 6H has a higher oscillating frequency than that of the probe 6L. A considerably higher oscillating frequency is selected for said oscillating frequency itself. Then the switch 18 is changed into the first probe, and the peak value of the reflected signal from a bonded part is taken out. The switch 18 is changed into the second probe, and the peak value of the reflected wave signal from the bonded part is taken out. The difference between the two peaks is obtained. The presence of absence of the peeling on the bonded surface is judged based on the difference thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic testing device that non-destructively tests the adhesion state of bonded surfaces inside a subject using ultrasonic waves.

[Conventional technology]

2. Description of the Related Art Ultrasonic inspection means that emit ultrasonic waves to a subject and inspect the internal state of the subject (presence or absence of defects, etc.) based on signals of reflected echoes from the subject are well known. As an example of such an inspection, a case where the object to be inspected is a semiconductor device will be described.

FIG. 3 is a sectional view of the semiconductor device. In the figure, 1 is a silicon chip that constitutes a semiconductor circuit, and 2 is a silicon chip 1.
3 is a lead frame for connecting the silicon chip 1 to an external circuit, and 4 is a molded resin body for molding these. The molded resin body 4 is made of synthetic resin. A large number of lead frames 3 are arranged in a direction perpendicular to the plane of the paper, and these lead frames 3 and silicon chips 1 are connected by extremely thin lead wires (not shown). 5 indicates a semiconductor device.

In such a semiconductor device 5, in the manufacturing process,
The silicon chip 1 and the mold+MB'O body 4, and the lead frame 3 and the mold resin body 4 may not be completely bonded to each other, and peeling may occur.

In the semiconductor device 5 where such peeling has occurred, is there any part of the peeled part? Electricity gets mixed in, and this hot air interferes with the function of the silicon chip 1, often making it unusable.Also, if peeling occurs, cracks tend to occur in the molded resin body from this part, and these cracks cause hot air to leak out. This will further encourage the intrusion of Therefore, it is essential to inspect the presence or absence of the peeling when using the semiconductor device 5. The ultrasonic inspection apparatus used for this inspection will be explained with reference to FIG.

FIG. 4 is a block diagram of a conventional ultrasonic inspection apparatus. In the figure, 5 is the semiconductor device shown in FIG.

6 is a probe that focuses and emits an ultrasonic beam 7 using an acoustic lens. The probe 6 emits an ultrasonic beam 7 and converts the reflected wave from the semiconductor device 1.5 into an electrical signal proportional to the ultrasonic beam 7. A balsa 8 applies an electric pulse to the probe 6, and the probe 6 emits an ultrasonic beam 7 by applying the pulse from the balsa 8. 9 is a receiver that receives and amplifies the electric signal of the ultrasonic reflected wave from the probe 6; 10 is an oscilloscope that displays the output signal waveform of the receiver 9;

Reference numeral 11 denotes a peak detector that detects the peak value of the output signal of the receiver 9 within a certain specific time. The specific time in the peak detector 11 is selected to be the time at which the reflected wave from the vicinity of the inspection target portion of the semiconductor device 5 reaches the probe 6. 12 is a signal processing device that processes the peak value detected by the peak detector 11 to determine the presence or absence of peeling in the inspection target portion; 13;
is a monitor T that displays the results obtained from the signal processing bag W12.
It is V.

Next, the outline of the operation of the ultrasonic inspection apparatus shown in Fig. 4 will be explained in Fig. 5.
This will be explained with reference to the waveform diagrams of reflected wave signals shown in FIGS. (a) and (b). A reflected wave signal from the probe 6 is amplified by a receiver 9 and displayed on an oscilloscope 10. By the way, when the adhesion between the silicon chip 1 and the molded resin body 4 or the adhesion between the lead frame 3 and the molded resin body 4 is normal, the waveform of the reflected wave signal at the adhesive part is shown in FIG. 5(a). The waveform will look like this. On the other hand, if peeling occurs in the bonded part and an air layer is formed, the waveform of the reflected wave signal will be smaller than the waveform shown in FIG. 5(a), as shown in FIG. 5(b). It is also known that the peak value is large and the phase is reversed. Therefore, by observing the waveform displayed on the oscilloscope 10, it is possible to determine whether or not the adhesive portion has peeled off.

However, what is displayed on the oscilloscope 10 is
Not only the waveform of the reflected wave signal from the adhesive part, but also the waveform from the surface of each element constituting the semiconductor device 5 is displayed, and it is not easy to observe the waveform of the reflected wave signal from the adhesive part, and it is difficult to observe the waveform of the reflected wave signal from the adhesive part. Even if this occurs, the signal waveform may not become that large, or the phase reversal may not clearly appear.

Therefore, it is extremely difficult to determine the presence or absence of peeling using the oscilloscope 10. For this reason, the peak detector 11
Also, a means for determining the presence or absence of peeling using the signal processing device 12 has been proposed. The determination by this determining means is made as follows.

The peak detector 11 receives the signal from the receiver 9 and detects a positive peak value and a negative peak value of the waveform (waveform of the bonded portion) within a specific time.

These peak values when there is no separation in the bonded part are shown in Figure 5 (
PI and PI are shown in a), and the peak values when peeling occurs are shown as P and +P2 in FIG. 5(b). The signal processing device 12 inputs the absolute values of the two peak values and performs an operation of subtracting the negative peak value from the positive peak value. By the way, when there is no peeling in the adhesive part, the absolute values of the peak values P+ and Pz are in the relationship Pi > p2, and when there is peeling, the absolute values of the peak values p+' and pz' are p
, r >P2', so the difference (p+ - Pg) when there is no peeling is positive, and the difference when there is peeling (p.

-pz') becomes negative, and by determining whether the above subtracted value is positive or negative, it is possible to know the reversal of the latter phase.
distance can also be detected. Note that even if peeling occurs in the bonded portion, the above difference may be positive. In that case, since the value of the difference will be a small value, the above-mentioned subtraction is performed by setting a certain threshold value when the difference is positive and incorporating this dark value. Specifically, the darkness value is further subtracted from the difference value, and whether the obtained value is positive or negative is determined.

Depending on whether the result of the subtraction is positive or negative as described above, the signal processing device 12 outputs a high level signal if the difference is positive, for example.
If negative, a low level signal is output. Based on this output signal, the monitor TV 13 displays, for example, white when it is at a high level and black when it is at a low level. In this way, by scanning the plane of the semiconductor device 5 with ultrasonic waves, the presence or absence of peeling at each point on the scanning line A is displayed as a white and black image on the screen of the monitor TV 13, and inspection can be performed. .

[Problem to be solved by the invention]

The semiconductor device 5 is inspected by the ultrasonic inspection device not necessarily immediately after its manufacture, but at a time when a considerable amount of time has passed since its manufacture, for example, when the semiconductor device 5 is inspected by the ultrasonic inspection device.
This is often done just before it is incorporated into various machines, devices, etc. By the way, when there is peeling in the bonded portion of the semiconductor device 5, as time passes, conductive air enters the peeled portion, and water eventually accumulates in this portion. This is remarkable when cracks are generated from the peeled portion as described above. When a layer of water is formed in the peeled area in this way, when an ultrasonic wave is emitted, the size of the reflected wave will be the same as B, where no water is present (B, where a layer of air is formed). )
The reflected wave is small compared to the reflected wave of , and is reduced to a slightly lower level than the reflected wave of normal bonding. Therefore, it is impossible to distinguish between a normal adhesion state and a state where water has accumulated in the peeled area, and if water has accumulated there even though there is peeling, it is determined that the adhesion is normal.
This has often caused failures in the equipment 1 machine, etc. in which the semiconductor device 5 is incorporated. Such problems occur not only in semiconductor devices but also in other test objects.

The purpose of the present invention is to solve the problems in the above-mentioned prior art,
An object of the present invention is to provide an ultrasonic inspection device that can reliably detect peeling of a joint surface of a subject.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an ultrasonic inspection apparatus that radiates ultrasonic waves to a subject and inspects a joint surface inside the subject based on the reflected wave signal. a second probe having a second vibration frequency higher than the first vibration frequency;
a switch for switching between the first probe and the second probe, and a positive peak value of each reflected wave signal output from the first probe and the second probe; The present invention is characterized in that it includes a signal processing means for calculating a difference, and a determining means for determining whether or not there is peeling of the bonded surface based on the difference signal obtained by the signal processing means.

[For production]

Switch the switch to the first probe side and take out the peak value of the reflected wave signal from the bonded part, and switch the switch to the second probe side to take out the peak value of the reflected wave signal from the bonded part. Extract the peak value. Then, find the difference between these two peak values,
Based on the difference, the presence or absence of peeling of the bonded surface is determined.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a block diagram of an ultrasonic inspection apparatus according to an embodiment of the present invention. In the figure, the same parts as those shown in FIG. 4 are given the same reference numerals. 6L and 6H are probes having different vibration frequencies. Probe 6H is probe 6L
A material having a higher vibration frequency, and which itself has a considerably high vibration frequency, is selected. A switch 15 selectively switches between the probe 6L and the probe 6H. 11' is a gate. This gate 11' is the fourth
It has only the function of extracting a signal within a certain time period during the function of the peak detector 11 shown in the figure, that is, a reflected wave signal of the bonded portion. Therefore, the output of gate 11' is as shown in FIG.
The waveform corresponds to the waveform shown in a). 16 is gate 1
A detector 17 detects the reflected wave signal outputted from the detector 1' and outputs its peak value, and an A/D converter 17 converts the peak value outputted from the detector 16 into a digital value.

Reference numeral 18 denotes a switch that performs a switching operation in conjunction with the switch 15. 19 is a memory, 20 is a subtracter, and 21 is a determiner. The determiner 21 determines whether or not the adhesive portion has peeled off based on the output signal of the subtracter 20. 22 is an attenuator connected to the probe 6H.

Next, the operation of this embodiment will be explained with reference to the waveform diagrams of reflected wave signals shown in FIGS. 2(a) and 2(b). In FIGS. 2(a) and 2(b), time is plotted on the horizontal axis and voltage is plotted on the vertical axis, both of which are slightly enlarged compared to FIG. 5(a). Generally, when an ultrasonic wave with a low vibration frequency passes through a layer of water, there is little attenuation due to interference, but an ultrasonic wave with a high vibration frequency is thickened (attenuated) due to interference.

In this embodiment, the characteristics of ultrasonic waves as described above are used to detect peeling at a peeled portion where water is accumulated.

In this embodiment, the switch 15 is first switched to the probe 6L side. In conjunction with this, the switch 18 is switched to the memo 1J19 side. Further, the probe 6L is moved to a predetermined position for inspection. When a pulse is output from the pulser 8 in this state, the ultrasonic beam 7 is emitted from the probe 6L to the adhesive part to be inspected, and the reflected wave signal is transmitted to the probe 6L,
The 0 reflected wave signal output from the switch 15 and the receiver 9
7. The signal is inputted to the gate 11' through the gate 11', where only the reflected wave signal of the bonded portion as shown in FIG. 5(a) is extracted.
The signal is detected by the detector 1-6 as shown in FIG. 2(a), and the peak value P□ of this detected waveform is output, and the A/
The D converter 17 converts the peak value P i+ into a digital value. The converted peak value P□1 is stored in the memory 19 via the switch ]8.

Next, the switch 15 switches the probe 6H9 switch 1 to the subtractor 20 side, and the probe 6T is placed in a position where its ultrasonic beam 7 is irradiated to the same position as the previous position. be moved to When ultrasonic waves are emitted in this state, the reflected wave signals are transmitted to the switch 15, the receiver 9, and the gate 11.
' is input to the detector 16, and the peak value Pbl of the detected waveform shown in FIG. 2(b) is output. At this time, Pb
The value of P is adjusted by the attenuator 22 so that l≦P0. Thereafter, the peak value P1+l is converted into a digital value by the A/D converter 17 and inputted to the subtracter 20 via the switch 18. At this time, the value previously stored in the memory 19 is also input to the subtracter 20, and the subtracter 20 subtracts both values. The determination unit 21 uses this subtraction result as a reference value.
to be memorized.

Next, the position where the ultrasound beam is irradiated is moved, and the probe 6
Two detected waveforms are obtained using H and the probe 6L in the same manner as above, and the difference between their peak values is obtained from the subtracter 20. The value from the subtracter 20 is sent to the determiner 21, and the difference between it and the previously stored reference value is calculated.

Here, if the adhesive part is normal, the waveform detected by the detector 16 will be as shown by the solid lines in FIGS. 2(a) and 2(b), and the peak value of the probe 6L will be Po, The peak value of 6H is Pbl. On the other hand, if the adhesive part is peeled and water is collected there, the ultrasonic waves from the probe 6H, which has a high vibration frequency, will be attenuated in size due to interference when passing through the water layer. As shown by the broken lines in FIGS. 2(a) and 2(b), the waveform detected by the wave detector 16 shows that the peak value of the probe 6L is a value P0 with relatively small attenuation, and the peak value of the probe 6H is a value P0 with relatively small attenuation. The attenuation is large (iPbt).

Therefore, the difference between peak value Pyu2 and peak value P1□ is greater than the difference between peak value P□ and peak value Pb1O,
the reference value is taken in a normal area of adhesion, and
If the newly inspected part is normal, the output from the determiner 21 will be 0 or a value extremely close to O, and if the newly inspected part is a peeled part where water has accumulated, the output from the determiner 21 will be 0 or very close to O. 2
The output from 1 is a positive value. On the other hand, if the above-mentioned reference value is taken at a peeled part where water has accumulated, and the newly inspected part is a peeled part where water has accumulated, the output from the determiner 21 will be extremely low to 0 or O. If the values are close to each other, and if the newly inspected part is a normal part, the output from the determiner 21 will be a negative value. From the above, if a negative value occurs in the course of successive flaw detection, it is determined that the previously used reference value is a reference value based on the peeled part where water has accumulated, so The reference value that has been used up until now is stored in the current output from the subtracter 20, and flaw detection is performed again from the beginning.

As a result, the output from the determiner 21 will be O or a value very close to O if the bonded portion is normal, and a value considerably larger than 0 if the peeled portion has accumulated water.

In this way, in this example, the same location is inspected separately using a low-frequency probe and a high-frequency probe, each peak value of each reflected wave signal obtained is subtracted, and the subtracted value is Since the inspection is performed based on the above-described method, peeling can be reliably detected even if water accumulates at the peeled part of the adhesive part.

Note that the display is not limited to an oscilloscope, and may be displayed using a monitor TV depending on the brightness.
An indicator light, a buzzer, etc. can also be used.

〔Effect of the invention〕

As described above, the present invention calculates the difference in the positive peak value of each reflected wave signal of the bonded part by two probes of low frequency and high frequency, and determines the presence or absence of peeling based on this. Therefore, even if water is present in the peeled part,
Peeling can be detected reliably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an ultrasonic inspection apparatus according to an embodiment of the present invention, FIGS. 2(a) and 2(b) are detection waveform diagrams of reflected wave signals, and FIG. 3 is a cross-section of a semiconductor device as an object to be inspected. Figure, 4th
The figure is a block diagram of a conventional ultrasonic inspection device, Figure 5 (a)
, (b) is a waveform diagram of a reflected wave signal. 6L, 6H... Probe, 9...
...Receiver 1.11'...Gate,
15.18......Switcher, 16...
...Detector, 17...A/D converter, 19...Memory, 20...
...Subtractor, 21...Determiner, 22...
・・・・・・Attenuator. Figure 1 Figure 1

Claims (3)

[Claims] (1) In an ultrasonic inspection apparatus that radiates ultrasonic waves to a subject and inspects a joint surface inside the subject based on the reflected wave signal, a first probe having a first vibration frequency; , a second probe having a second vibration frequency higher than the first vibration frequency; the first probe and the second probe;
a switch for switching the probe; a signal processing means for calculating a difference between positive peak values of each reflected wave signal output from the first probe and the second probe; 1. An ultrasonic inspection apparatus comprising: determination means for determining the presence or absence of peeling of the bonded surface based on the difference signal obtained by the processing means. (2) In claim (1), the signal processing means includes a detector that detects each of the reflected wave signals and outputs their peak values, and an A/D that converts the output of the detector into a digital value. a transducer, a memory for storing the peak value obtained from the first probe, and calculating a difference between the value stored in the memory and the peak value obtained from the second probe. An ultrasonic inspection device comprising: a subtracter; (3) In claim (1), the determining means comprises discriminating means for determining whether or not the difference signal output from the signal processing means has a value near 0. Sonic testing device.