JP3013647B2 - Measuring device for discontinuous structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure having a discontinuous surface by measuring the element width, element position, element displacement, element coordinate position, etc. from a scanning measurement of a laser displacement meter for a structure having a discontinuous measurement surface. The present invention relates to an apparatus for measuring a discontinuous structure for obtaining information.

[0002]

2. Description of the Related Art If the terminal height of an LSI package is not uniform or the height of a pad on a printed circuit board to be mounted is not uniform, a soldering failure occurs and the reliability is low. I will. To inspect these, a measurement technique using laser light is used. This measurement technology, which measures the surface displacement and surface shape of a discontinuous structure to be measured, includes a laser displacement measurement technology that uses reflected light when a non-measurement object is irradiated with laser light, and a transmitted light Some are used. For example, a laser displacement measuring instrument using reflection of irradiated laser light is used for inspection of terminal lifting of terminals of an LSI package and inspection of unevenness of a pad portion of a printed circuit board on which the LSI package is mounted. ing.

FIG. 12 is a configuration diagram showing a basic configuration of this conventional laser displacement meter. In the figure, reference numeral 121 denotes a laser generating means for oscillating a laser; 122, a measurement surface to be measured; 123, a lens for condensing laser light reflected on the measurement surface 122; A detector 125 is a position calculating unit that processes a signal output from the detector 124 to calculate a displacement of the measurement surface 122.

[0004] The laser light serving as the spot light emitted from the laser generating means 121 is applied to the measurement surface 122 in a state where the spot diameter is reduced so as to minimize the spot diameter. Since the light reflected on the measurement surface 122 is scattered about the specular reflection direction, a part of the light is received by the lens 123 and
An image of a bright light spot at the upper reflection point is projected on the light receiving surface of the detector 124. The detector 124 outputs to the position calculation means 125 as an electric signal which position of the light receiving surface the incident light is received. Therefore, when the measurement surface 122 is displaced, the reflection point on the measurement surface 122 viewed from the lens 123 is observed to move, and the output signal of the detector 124 changes. A proportional signal output is obtained.

If this laser displacement meter is used, for example, L
Terminal displacement, terminal interval, terminal width, and terminal pitch of SI package can be measured. FIG. 13 is a sectional view showing a measurement state of a terminal state of an LSI package using a laser displacement meter, and a waveform diagram showing signals obtained by the measurement. FIG.
In FIG. 3A, reference numeral 131 denotes a laser displacement meter that performs linear scanning, 132a to 132e denote terminals of an LSI package, and a terminal 132d is a terminal floating. The laser displacement meter 131 linearly scans the terminals 132a to 132e, thereby obtaining a signal 133 as shown in FIG.

The signal 133 is subjected to threshold processing using a reference signal 134, etc., so that each terminal 132a
~ 132e displacement, terminal spacing, each terminal 132a ~ 132
The width of e and the pitch of the terminals can be measured. Here, in order to accurately obtain these measured values, the terminals 132a to 132e
It is desirable that the width is larger than the beam diameter of the laser light used, and that the optical reflectance is uniform and flat.

On the other hand, when measuring the width of a terminal of an LSI package or the like by using transmitted light when a laser beam is irradiated, a measuring device as shown in FIG. 14 is used. FIG.
FIG. 2A is a cross-sectional configuration diagram illustrating an example of terminal width measurement using transmitted light when a laser beam is irradiated. In the figure, 141 is a terminal of a package to be measured, 142 is a laser beam to be irradiated, and 143 is an incident light amount (transmitted light intensity).
Is a light amount detection unit that detects Laser light 142 for irradiation
Is linearly scanned, and the terminal 141 blocks the laser beam 141, so that the transmitted light intensity detected by the light amount detection unit 143 changes as shown in FIG. 14B. The width and the like of the terminal 141 can be measured from the change point of the transmitted light intensity.

[0008]

Conventionally, the above-described configuration has the following problems.
First, in the case of a laser displacement meter using reflection, since the discontinuous structure to be measured, for example, terminals of an LSI package are becoming thinner and smaller in pitch, the spot diameter of the laser light to be irradiated is reduced. Must-have. For this reason, if the error in the distance between the laser displacement meter and the object to be measured is large, measurement cannot be performed.

That is, depending on the installation state of the package to be measured, the distance from the laser displacement meter changes for each package, or the package is inclined. If the distance changes, the average level of the obtained signal changes and the reference level is not constant, making it difficult to identify each terminal of the package. Further, if measurement is performed in a state where the package to be measured is tilted, the reference line of the obtained signal is also tilted, and data such as displacement and pitch cannot be calculated by simple threshold processing.

In the laser displacement meter, a certain range exists as a measurable region before and after the focal position of the irradiated laser beam, that is, the position where the spot diameter of the laser beam is the smallest. As shown in FIG. 15A, the terminal 151 to be measured is
Is within this measurable region of the laser beam 152
However, when the package is far from the focal position, even if the terminals to be measured are not tilted and the terminals are evenly arranged in a horizontal line, as shown in FIG. Signal Hc
Becomes irregular. FIG. 16 shows the obtained displacement signal Hc.
If the state is as shown in FIG.
It can be processed as a quantified signal. Further, when the terminals of the package become smaller and the respective pitches become smaller, FIG.
As shown in (b), the scattered light 152a from the terminal 151a floating at the terminal is likely to enter the detector, causing noise.

On the other hand, when the transmitted light is used, since the spatial spread of the irradiated laser light is finite, the rising of the detected signal intensity has an inclination. This inclination makes detection of the position of each terminal to be measured unclear, and this phenomenon becomes more remarkable as the width of the terminals and the distance between the terminals become finer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. Even when the distance and the size of a discontinuous structure to be measured are reduced, the displacement and the size of the discontinuous structure are reduced. It is an object of the present invention to be able to accurately obtain spatial information such as a distance and an interval.

[0013]

According to the present invention, there is provided an apparatus for measuring a discontinuous structure, comprising: a laser generating means for emitting a spot-shaped laser beam to an object to be measured; and a laser irradiating the object to be measured. Position sensitive detection means for receiving the reflected light of the light and outputting a signal corresponding to the light receiving position, and receiving the reflected light of the laser light applied to the object to be measured and outputting a light quantity signal corresponding to the light quantity A displacement measuring unit comprising: a light quantity detecting means for detecting the light quantity; a displacement calculating means for outputting a displacement signal proportional to the displacement of the object to be measured based on a signal output from the position presence detecting means; Moving means for outputting a coordinate signal corresponding to the position of the displacement measuring unit, and the displacement, width, position, and the like of the measured object based on the displacement signal, the coordinate signal, and the light amount signal.
Signal processing means for calculating an interval.

Further, according to the present invention, there is provided an apparatus for measuring a discontinuous structure, wherein spatial information of the object to be measured is obtained by detecting transmitted light of laser light applied to the object to be measured. In the measuring device, a laser generating means for emitting a spot-shaped laser beam to the measured object to be measured, and a light quantity signal corresponding to the quantity of the received high-order light of the transmitted light of the laser light applied to the measured object Light detection means for outputting
Edge detecting means for receiving the zero-order light of the transmitted light of the laser light applied to the measured object and outputting an edge signal having a peak corresponding to the edge position of the measured object.

[0015]

The width, position and interval of the object to be measured are determined from the obtained light quantity signal, and the displacement of the object to be measured is calculated based on the width, position and interval of the object using the displacement signal.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. FIG. 1A is a configuration diagram showing a configuration of a discontinuous structure measuring apparatus according to an embodiment of the present invention. In the figure, reference numerals 1a to 1f denote terminals of an LSI package to be measured, 2 denotes a laser displacement measuring unit, 3 denotes a moving table on which the laser displacement measuring unit 2 is mounted and moves linearly, and 4 denotes an output by the laser displacement continuation unit 2. Displacement signal Hc, light amount signal Ic
And the coordinate signal Xc output by the moving table 3 is obtained,
A signal processing unit that processes these to calculate the terminal width Wi, the terminal position Pi, the terminal displacement amount Hi, and the terminal distance Di.

The laser displacement measuring section 2 includes a laser generating section 2
a, a position sensitive detection unit 2b, a light amount detection unit 2c, and a signal processing unit 2d. The laser light emitted from the laser generation unit 2a is reflected by terminals 1a to 1f, and a part of the laser light is reflected by the light amount detection unit 2c. It is taken in and output as a light amount signal Ic. Another part of the light reflected from the terminals 1a to 1f is captured by the position sensitive detection unit 2b, and the captured light is reflected by the position sensitive detection unit 2b.
A signal corresponding to where the light is received on the light receiving surface b is output. This signal is processed by the signal processing unit 2d and output as the displacement signal Hc.

The signal processing section 4 binarizes the light quantity signal Ic input at a preset threshold value V as shown in FIG. The displacement signal H is used as a position recognition signal (terminal position Pi).
a displacement calculator 4b that extracts a terminal displacement Hi from c and outputs the displacement of each of the terminals 1a to 1f as a time-series signal;
Using the binarized signal as the position recognition signal, the terminal width Wi and the terminal distance Di are calculated from the coordinate signal Xc, and each of the terminals 1a to 1a is calculated.
And a distance calculator 4c that outputs the width of 1f and the distance between them as a time-series signal.

FIG. 1B is a waveform diagram showing the state of each signal obtained by the measuring apparatus for discontinuous structures according to the first embodiment. Since the amounts of light reflected from the terminals 1a to 1f are equal,
The obtained light quantity signal Ic is a signal having a uniform height, and the binarization processing is easy. As shown in FIG.
The terminals 1a to 1f are discriminated and their positions are recognized based on the quantified light amount signal Ic, whereby the terminal position Pi, the terminal width Wi, and the terminal distance Di can be calculated. Then, by calculating the signal value of the displacement signal Hc corresponding to the calculated terminal position Pi (coordinate position) of each of the terminals 1a to 1f, FIG.
Even when the displacement signal Hc is in the state shown in FIG.
The displacement Hi of a to 1f is obtained.

Embodiment 2 FIG. FIG. 2 is a configuration diagram showing a configuration of a discontinuous structure measuring apparatus according to a second embodiment of the present invention. In FIG. 5, reference numeral 5 denotes a trigger oscillation unit which receives a coordinate signal Xc from the movement table 3 and outputs a trigger signal T to the laser displacement meter side unit 2 for each unit coordinate, and the other components are the same as those in FIG. Since the moving characteristics of the moving table 3 are not strictly constant but fluctuate, the displacement signal Hc and the light amount signal Ic detected and output as they are by the laser displacement meter side unit 2 at equal intervals.
The coordinate values of c are not equally spaced. However, in this embodiment, since the laser displacement meter side unit 2 controls the period detected by the trigger signal output for each unit coordinate when the moving table 2 moves, the displacement signal Hc to be output and the light amount signal Ic are output. Is less distorted.

Embodiment 3 FIG. FIG. 3 is a configuration diagram showing a configuration of a discontinuous structure measuring apparatus according to a third embodiment of the present invention. In the figure, reference numeral 34 denotes a signal processing unit in the measuring apparatus for discontinuous structures according to the second embodiment, which is different from the signal processing unit 4 shown in FIG. 1, and is a correction unit 34d for correcting the output signal of the distance calculation unit 4c. The other parts are the same as those in FIG. The correction unit 34d includes terminals 1a to 1d output from the distance calculation unit 4c.
The time-series signals of the width of 1f and the distance between them are added to the displacement signal Hc using a preset look-up table.
Refer to and correct.

Here, as described above, the light amount signal Ic is suitable for quantifying the terminal position and the terminal width. FIG.
Is obtained by superimposing the obtained displacement signal Hc and light amount signal Ic on the terminals of the LSI package.
Regarding the terminal width Wi, the light amount signal Ic is larger than the displacement signal Hc.
It shows a value closer to the actual size value. The reason why the displacement signal Hc is not suitable for the terminal width measurement is due to the displacement amount calculation formula for obtaining the displacement signal Hc. However, even if the terminal width Wi and the terminal distance Di are obtained by using the light amount signal Ic, there is an obstacle to higher measurement accuracy as described below.

When the terminal to be measured is shifted from the focal position of the laser beam to be irradiated, that is, the position where the spot diameter is minimum, the measured terminal width Wi is different. As shown in FIG. 5, the measurement result of the terminal 52a whose measurement distance is at the focal position of the laser beam 51 is different from the measurement result of the terminal 52b whose terminal is closer to the focal position and the measurement result of the terminal 52c at the former position. Become. As shown in FIG. 6, the measured terminal width Wi has a minimum value when the terminal position is at the focal position of the irradiated laser beam, and when it deviates therefrom, it is measured to be larger than the actual width. Since this can be obtained in advance by an experiment, this is set in the correction unit 24d (FIG. 3) as a reference table, and the data obtained from the distance calculation unit 4c may be corrected. As a result, even when the distance from the object to be measured is different, for example, when the terminal is lifted, the width and the pitch can be accurately measured.

Embodiment 4 FIG. A signal such as the light amount signal Ic originally has a characteristic that the baseline fluctuates. Therefore, if used as it is, an accurate coordinate position of the measured object cannot be obtained. Here, as shown in FIG. 7, the reference signal RFc and the light quantity signal Ic, which are pulses having different initial phases but the same cycle,
c, the light amount signal I is calculated using the following equation (1).
By calculating the phase φ _OPT and the pitch D _{OPT of} c, an accurate coordinate position can be obtained.

M (φi, di) = {Ic (n) × RFc (n, φi, di)} δn {M (φi, di) | MAX} (1) where di is a reference The pulse pitch (period), φi, of the signal RFc is the initial phase value of the reference signal RFc.

FIG. 8 is a configuration diagram showing a configuration of a measuring apparatus for a discontinuous structure according to the fourth embodiment. In the figure, reference numeral 81 denotes a reference table in which a reference signal RFc is set, and reference numeral 82 denotes a template matching unit that calculates a coordinate position of a terminal to be measured or the like based on the reference signal RFc and the light amount signal Ic set in the reference table 81. It is. The template matching unit 82 adds and subtracts the light amount signal Ic according to the polarity of the reference signal RFc and sequentially accumulates the result, and the maximum value of the result calculated by the addition and subtraction accumulation means 821 to 82n. And a maximum value detecting means 82a for detecting the

In the reference table 81, a reference signal RFc as shown in FIG.
To 82n perform the processing simultaneously with the reference signal RFc and the light amount signal Ic, and the maximum value of the result is detected by the maximum value detecting means 82a.
The initial value of the phase _φOPT of c. FIG. 9 shows the correlation strength between the reference signal RFc and the light amount signal Ic when the pitch di is changed from 226 to 280 μm in 6 μm steps.
The relationship of the initial value of the phase _φOPT is shown. From the figure, D _OPT =
It shows that φ _OPT = 190 μm at 250 μm. This process may be used for the displacement signal Hc.

Embodiment 5 FIG. By the way, if the light intensity distribution due to the reflected light from the object to be measured obtained by irradiating the laser beam is spatially symmetrical with a Gaussian shape, the position-sensitive detector 2b (FIG. 1) obtains the light intensity distribution. The reflected light intensity is always constant, and the maximum value in the distribution at that time can be obtained. However, when the object to be measured is a discontinuous structure such as an LSI package terminal, and the terminal width and the terminal interval become finer, multiple scattering light is generated due to a part of the terminal floating and the like, and the position-sensitive detector The received light intensity distribution of 2b becomes complicated. Here, instead of the position sensitive detection unit 2b, a CCD
If the intensity distribution of the incident reflected light is recognized by using the image sensor and the maximum value among them is used as the output of the light quantity signal Ic, the light quantity signal Ic is always constant.

In the case of the fifth embodiment, as shown in FIG. 10, a CCD line sensor 102 is used to output a light amount signal Ic, which is installed in a state orthogonal to the scanning direction. Note that the CCD line sensor 102 does not need to be installed in a direction orthogonal to the scanning direction, and may be arranged in any manner as long as the optical path of the reflected light is adjusted using a lens or the like.

Embodiment 6 FIG. FIG. 11 shows a sixth embodiment of the present invention, which is a measuring apparatus of a discontinuous structure for measuring a terminal width, a terminal interval, and the like of an LSI package by using transmitted light of a laser beam applied to an object to be measured. It is a block diagram showing a structure. In FIG. 11A, reference numeral 111 denotes a terminal to be measured,
Reference numeral 112 denotes a laser beam to be irradiated, 113 denotes a light detection unit that detects higher-order light of the transmitted laser beam 112, and 114 denotes an edge detection unit that is disposed on the light detection unit 113 and is smaller than the light detection unit 113. The edge detection unit 114 is configured as shown in FIG.
As shown in (b), the zero-order light of the laser light transmitted through the terminal 111 is detected, and an edge signal 115 is output.
The light detection unit 113 detects higher-order light from the transmitted laser light 112 and outputs a transmitted light intensity signal 116.

Conventionally, as shown in FIG. 14, since only one transmitted light intensity is measured by one light detecting section 143, since the spatial spread of the laser light 142 is finite, Transmitted light intensity 144 obtained by presence
There was a slope in the rise, and accurate measurement could not be performed. However, in the sixth embodiment, the edge detection unit 1
With the addition of 14, the edge signal 115 and the transmitted light intensity signal 116 are obtained, and by using them, the width, interval, position, and the like of the terminal 111 can be accurately measured.

[0032]

As described above, according to the present invention, even if the distance and the size of the discontinuous structure to be measured are reduced, the spatial information such as the displacement, the size and the distance of the discontinuous structure can be obtained. There is an effect that it can be obtained accurately.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of a measurement apparatus for a discontinuous structure according to an embodiment of the present invention, and a waveform diagram illustrating states of obtained signals.

FIG. 2 is a configuration diagram showing a configuration of a discontinuous structure measuring apparatus according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a configuration of a discontinuous structure measuring apparatus according to a third embodiment of the present invention.

FIG. 4 is a waveform diagram showing a state in which a displacement signal Hc and a light amount signal Ic are superimposed.

FIG. 5 is a cross-sectional configuration diagram illustrating a positional relationship between a focal position of a laser beam and a measurement distance of a terminal.

FIG. 6 is a correlation diagram showing a correlation between a measurement distance and a measurement result.

FIG. 7 is a waveform diagram showing a reference signal having a different initial phase and a reference signal having a different pulse width.

FIG. 8 is a configuration diagram illustrating a configuration of a measurement apparatus for a discontinuous structure according to a fourth embodiment of the present invention.

[9] when changing at 6μm step pitch di to 226～280Myuemu, the correlation strength of the reference signal RFc light quantity signal Ic, it is a waveform diagram showing the relation between the initial value of the phase phi _OPT.

FIG. 10 is a configuration diagram illustrating a configuration of a measurement apparatus for a discontinuous structure according to a fifth embodiment of the present invention.

FIG. 11 is a configuration diagram illustrating a configuration of a measurement apparatus for a discontinuous structure according to a sixth embodiment of the present invention.

FIG. 12 is a configuration diagram showing a basic configuration of a conventional laser displacement meter.

13 is a cross-sectional view showing a measurement state of a terminal state of an LSI package using the laser displacement meter of FIG. 12, and a waveform diagram showing obtained signals.

FIG. 14 is a cross-sectional configuration diagram illustrating an example of terminal width measurement using transmitted light when a laser beam is irradiated.

FIG. 15 is a sectional view showing a positional relationship between a laser beam and a terminal.

FIG. 16 is a waveform diagram showing a waveform of a signal obtained by a conventional laser displacement meter.

FIG. 17 is a waveform chart showing a binarized state of the obtained light quantity signal.

[Explanation of symbols]

 1a to 1f terminal 2 laser displacement measuring unit 2a laser generating unit 2b position sensitive detecting unit 2c light amount detecting unit 2d signal processing unit 3 moving table 4 signal processing unit 4a binarization processing unit 4b displacement calculating unit 4c distance calculating unit Di terminal Distance Hc Displacement signal Hi terminal displacement amount H Ic Light amount signal Pi terminal position Wi terminal width Xc coordinate signal

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshifumi Kimura 8-1-1, Tsukaguchi-Honmachi, Amagasaki-shi, Hyogo Mitsubishi Electric Corporation Production Technology Laboratory (56) References JP-A-4-120406 (JP, A) JP-A-2-27207 (JP, A) JP-A-62-128311 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102

Claims (9)

(57) [Claims] 1. A laser generating means for emitting a spot-shaped laser beam to an object to be measured, a reflected light of the laser beam applied to the object to be measured, and a signal corresponding to the light receiving position. Sensible detecting means for outputting the reflected light of the laser light applied to the object to be measured, and a light quantity detecting means for outputting a light quantity signal corresponding to the light quantity, and an output of the position sensitive detecting means. A displacement measuring unit configured to output a displacement signal proportional to the displacement of the object to be measured by a signal to be measured; and coordinates corresponding to the position of the displacement measuring unit by linearly moving the displacement measuring unit. A moving means for outputting a signal; and a signal processing means for calculating a displacement, a width, a position, and an interval of the measured object based on the displacement signal, the coordinate signal, and the light amount signal. Measuring device. 2. The measuring apparatus for a discontinuous structure according to claim 1, wherein said light amount detecting means is a light detecting element in which a plurality of light detecting sections are arranged. 3. A measurement apparatus for a discontinuous structure which obtains spatial information of a measurement object by detecting transmitted light of a laser beam applied to the measurement object to be measured. A laser generating means for emitting a spot-shaped laser beam; a light detecting means for receiving a higher-order beam of transmitted light of the laser beam applied to the object to be measured and outputting a light amount signal corresponding to the light amount; Edge detection means for receiving the zero-order light of the transmitted light of the laser light applied to the measurement object and outputting an edge signal having a peak corresponding to the edge position of the measurement object. Structure measuring device. 4. The measuring apparatus for a discontinuous structure according to claim 1, wherein the coordinate signal is based on unit coordinates of the displacement measuring unit. 5. The measurement apparatus for a discontinuous structure according to claim 1, wherein the signal processing unit binarizes the light amount signal and outputs a binarized light amount signal.
An apparatus for measuring a discontinuous structure, comprising: a value converting means; and a displacement calculating means for calculating a displacement of the object to be measured based on the binarized light quantity signal and the displacement signal. 6. The measuring device for a discontinuous structure according to claim 1, wherein the signal processing device binarizes the light amount signal and outputs a binarized light amount signal.
An apparatus for measuring a discontinuous structure, comprising: digitizing means; and dimension calculating means for calculating a width, a position, and an interval of the measured object based on the binarized light amount signal and the coordinate signal. 7. The apparatus for measuring a discontinuous structure according to claim 1, wherein the signal processing unit binarizes the light amount signal and outputs a binarized light amount signal.
Value calculating means; dimension calculating means for calculating the width, position, and interval of the measured object based on the binarized light quantity signal and the coordinate signal; A measuring unit for measuring a discontinuous structure, comprising: a correction unit that sets a correlation with an interval and corrects a value calculated by the dimension calculation unit with reference to the displacement signal. 8. The apparatus for measuring a discontinuous structure according to claim 1, wherein the signal processing means adds and subtracts a reference table in which a plurality of reference signals having different initial phases are set, and an input signal. A template matching means for performing preprocessing by using the reference signal that gives the maximum value of the calculation result. 9. The apparatus for measuring a discontinuous structure according to claim 1, wherein the signal processing means sets a plurality of first reference signals having different initial phases and a plurality of second reference signals having different reference periods. And a template matching means for performing pre-processing by using the first and second reference signals that give the maximum value of the addition / subtraction accumulation result of the input signal. Structure measuring device.