JPH01250743A - Measuring method of density with high precision - Google Patents

Abstract

PURPOSE:To obtain a measured value of a surface density in high precision by a transmitted X-ray measurer and a measured value of a thickness in high precision by a thickness measurer respectively, by making a correction by means of a prescribed formula when the measured value of the surface density of a ceramic tape is determined by a specific formula. CONSTITUTION:On the occasion when a measured value of the surface density of a ceramic tape 3 is determined by the formula I (where N denotes transmitted X-ray detection count cps after correction, (t) the thickness (m) of the tape 3, (rho) the density g/m<2>, (k) an inverse number g/m<2> of the absorption coefficient of the tape 3 for the X-ray, N0 the transmitted X-ray count at t=0, and Ns the transmitted X-ray detection count in case of t=infinity ), a value N corrected by the formula II is substituted for the values N, N0 and Ns in said formula. When the thickness (t) of the tape 3 is measured by a laser thickness measurer 8, the measurer 8 is subjected to a temperature control. Thereby a measured value of a pc counter 5 is corrected and an accurate X-ray count can be calculated. As the result, the surface density (rho) can be measured with high precision, and the density of the tape 3 can be measured with high precision, in combination with the result of highly-precise measurement of the thickness by the measurer 8.

Description

[Detailed Description of the Invention] [Field of Industrial Application] Ceramic packages and the like used as cases for integrated circuits are made by adding a binder to alumina powder, a sintering aid, and a solvent to form a slurry using the doctor blade method. It is made by pressing down a ceramic tape, a so-called green sheet, into a tape shape using a mold, drying it, and firing it.

In order to obtain a homogeneous product, it is necessary to strictly adjust the density of the green sheet (green density), depending on the rolling conditions and the properties of the ceramic powder.

As a method of measuring green sheet density, the areal density of the green sheet is measured using a fluorescent XvA densitometer on the green sheet press line, and the thickness of the green sheet at the relevant part is separately measured, and the green sheet is determined from the measured areal density and thickness. There is a method for calculating the green density of green sheets.The present invention improves this density measurement and relates to a high-precision density measurement method for green sheets.

[Conventional technology]

The green sheet is fired to become a ceramic package material, and the dimensions after firing are approximately 20% of the dimensions before firing.
It also contracts. The required accuracy of product dimensions for such shrinkage is within ±0.5%, which is strict.However, there is a clear correlation between shrinkage and the density change rate before and after firing, and the density after firing is Since it is constant depending on the particle size, it is necessary to measure the density of the green sheet with high precision before firing in order to obtain the product dimensions with high precision.

As a conventional density measurement method, there is a specific gravity measurement method in which a solid is immersed in a liquid and its weight in the liquid is measured (JIS
Z8807), this method involves a destructive test in which a sample is cut to an appropriate size and weight. Therefore, it is impossible to locally measure the density of green sheets on the production line.

(Problem to be solved by the invention) As a means of solving this problem, a method is to obtain density ρ x thickness t (area density ρt) by the absorption method of transmitted X-rays, and divide it by a separately measured thickness t to calculate density ρ. is possible.

Figures 1 (a) and 1 (b) show the areal density measurement method using transmitted X-rays. In the figure (a), the beam emitted from the X-ray tube 1 hits the 21 reflector 2 and produces fluorescent X-rays Z, -K X-rays. It passes through the ceramic tape 3 and enters the proportional counter (pcC counter 5) in the collimator 4. (b)
In the example shown, the Zr reflector 2 is located below, and the beam passes through the ceramic tape 3 twice and enters the PC counter 5.

The above-mentioned pcC counter is an xvAm detector that can measure the X-ray dose as a count number. ■ It is less affected by the ambient temperature of the detector and has good stability. ■ It can count in a high count area (Figure 2 shows the pcC counter). and the maximum detection count number of a semiconductor counter), and has features such as being able to improve accuracy by short-term measurement.

However, as shown in FIG. 3, when the pcC counter detection count number is passed through the wave height discriminator 10, due to its characteristics, as it moves into the high count range, the number of counting errors increases and the pcC
The relationship between the counter's incident X&I detection intensity and the X-ray tube current, which has a linear relationship, is no longer a straight line.In other words, the linearity is distorted, such that the count decreases at a large count, and the measured pcC counter If the areal density is calculated by directly using the count number as the incident X-ray intensity value of the pcC counter, there is a problem that an error occurs in the calculated value of the areal density.

Next, the laser displacement meter, which is known as a highly accurate thickness measurement method, has the following characteristics. Even if the surface of the ceramic tape is uneven with ceramic particles, and even if the laser is diffusely reflected by the unevenness of the ceramic particles, the thickness can be determined by the average value of the values over a wide area. However, the problem with laser displacement meters was that the measuring instruments were susceptible to temperature changes and were susceptible to errors.

The present invention solves the above problems and provides a method for obtaining highly accurate areal density using a transmission XvA measuring device, and obtaining highly accurate thickness measurement values using a thickness measuring device to calculate density with unprecedentedly high accuracy. The purpose is to provide.

[Means to solve the problem]

The known principle formula for the attenuation of X-ray intensity when Zr fluorescence (cps
) [: Thickness of ceramic tape (m) ρ: Density (g/n?) K: Reciprocal of absorption coefficient of ceramic tape for X-rays (g/a) N6: Transmitted x-ray detection count at t=Q (cps) Ns: denoted as transmitted X-ray detection counts (cps) at t=■, and the areal density ρt can be calculated by measuring N when N-, No, and K are known.

The inventor attempted to find a method for correcting fluctuations due to drift in the measured count number of the PC counter 5.

A curve S in FIG. 4 shows the relationship in which the detected count number N'' (cps) of the PC counter changes depending on the intensity of X-rays incident on the PC counter.

If the performance curve S has a linear relationship, the drift of the X-ray source, sensor, etc. with respect to the initial calibration count number N cr calibrated under the standard calibration conditions and the latest calibration count number Ns calibrated under the same conditions. The correction formula for the variation of N'' due to the following will be: Corner N = -X N'' (3) Nc&.

However, due to the characteristics of the wave height discriminator connected to the PC, the actual N0 value increases in count errors as it gets higher in the count range, and as it draws a curve S, it is uniformly (3
) formula cannot be adopted.

The present inventor measures the count change rate for No of the PC counter in response to minute changes in tube current, which has a linear relationship with various incident XwA intensities in each count region, and makes the following correction that strictly matches the actual measurement value. An attempt was made to find the value of the count change rate R4e in the relationship of the formula % (21::).

FIG. 5 shows the relationship between R4r and the X-ray count according to the inventor's experiment. In this experiment, the XkI tube current was 0°220m.
Starting from A, the result when changing to 0.215 mA is shown by the mark O, and the result when changing to 0.225 mA is shown by the mark 0. The calibration point in the figure is the count change rate at point A of about 70,000 cps. The thickness of Rac is Nc/NcI between AB.・The curve connecting the marks and ○ marks starts from point A and is between AC and C+ above point A.

The horizontal line passing through the 0 point at ×Ne/NcI is an asymptote,
Attenuation surface vA toward its asymptote (with point A as the origin and vertical axis N
c/Nc, xc.

C*(N--)l'') (where Cr-C, (1-C')), drawn at the coordinates of the horizontal axis Nc-N'').

In the present invention, when obtaining the areal density measurement value using the above-mentioned formula +1),
The gist of the present invention is a high-precision density measurement method for green sheets, which is characterized by substituting the N value corrected by the above-mentioned equation (2) into the NsNs and Ns values to be substituted into the equation (1).

Further, when carrying out the present invention, it is essential to control the temperature of the thickness measuring device to prevent errors caused by deformation. Therefore, the second invention is characterized in that, in the method of the present invention, the temperature of the thickness measuring device is controlled when the thickness is measured by the thickness measuring device.

(Function) According to the present invention, it is possible to calculate an accurate XI count by correcting the measured value of the PC counter, and as a result, the areal density can be measured with high precision, and a separate thickness measuring device is required. Coupled with the highly accurate thickness measurement result obtained by the method, it is possible to measure the density of green sheets with high accuracy.

〔Example〕

An example of an apparatus suitable for carrying out the measuring method of the present invention will be explained with reference to FIG.

The green sheet 3 is intermittently fed in the direction of the arrow. An X-ray tube 1 is provided above the green sheet 3.
7 enters the reflection plate 2 and is reflected as fluorescent XiZ, -KX rays. The reflected fluorescent X-rays pass through the green sheet 3 again and enter the PC counter 5 located diagonally above the green sheet.

Behind the flow of the green sheet 3, there is a laser thickness measuring device 8 consisting of a C frame 7 kept warm by temperature-controlled air 6, and an upper laser 19a attached to the C frame 7.
Laser light is emitted from the lower laser source 9b, reflected from the green sheet 3, and enters the respective light receiving ends.

The procedure for carrying out the method of the present invention in the apparatus is as follows.

The current measured by the PC counter 5 is pulse height discrimination H (SC
A) Waves having a wave height of a certain level or more are taken out at 10, and the number is counted by the count control section 1).

In the laser thickness measuring device 8, the laser beam displacement of the entire surface of the part measured by the xmi3 thickness measuring device before the green sheet 3 is measured by the laser beam scanned by the span following mechanism 13 and the scanning mechanism 14 which are drive-controlled by the drive control 12, and the average displacement is measured. be converted into This beam displacement passes through the upper displacement converter 15 and the lower displacement converter 16 and enters the thickness calculating section 17, where the thickness of each part of the three green sheets is sequentially calculated.

In the areal density calculation and raw density calculator 18, the areal density value is calculated with high accuracy by adding correction to the 50 counts of the PC counter, and the areal density value is divided by the manually calculated thickness value, and the green sheet is Highly accurate raw density over the entire surface is calculated.

〔Effect of the invention〕

Accuracy is determined by the statistical coefficient of displacement σ/Y (σ: standard deviation, Y:
average value). The number of measurements is (number of counts N) x (
Measurement time t), so σ = f "[, x = Nt, and the displacement coefficient is 1/= fN] - Therefore, the accuracy is better as the number of counts increases and as the measurement time t becomes longer. Become.

FIG. 7 shows the relationship between the green density variation 3σ/Y and the measurement time for the green densities of six types of green sheets, A, B, C, D, E, and P.

Naturally, as the measurement time becomes longer, the green density variation becomes smaller, and the measurement accuracy improves. Furthermore, regardless of the thickness, there is an effect of measuring in a region with a large number of counts, and high accuracy is obtained even in a relatively short time. The green density variation 3σ/X for thickness A is a good result of 0.20%.

Next, the effects of implementing the method of the present invention will be explained.

When the X-ray count is approximately 73,000 cps when the thickness is zero, Sample 0--- Thickness 0.5w, X-ray count approximately 50,000 cps Sample 4--- Thickness 1.0 Tsuru, x* Count about 3
0000cps sample) Measure the fresh density at the same point for L @, @ for time 3
The moving average of 5 points repeatedly measured at 00 seconds/point is plotted in FIGS. 8 and 9.

Figure 8 shows the results when no correction is made to the method of the present invention.
Sample 4) with a small X-ray count far from the count of approximately 73,000 during calibration resulted in an error of approximately ±0.1%.

The results of the correction of the method of the present invention are shown in FIG.

It has become possible to keep the error to less than ±0.05% even with sambu noise.

In addition, the temperature of the C frame 7 in the laser thickness measuring device is ±
When kept at 0.2℃, the variation in the average thickness of 512 points in the scanning area of 3 cranes on the green sheet was within a small range of ±0.4μm, and good results were obtained to ensure reproducibility. Ta.

As described above, the present invention makes it possible to measure the density of green sheets with high precision, and greatly contributes to the production of ceramic packages.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram showing the areal density measurement method using transmitted X-rays, Figure 2 is a diagram showing the relationship between the incident X-ray intensity on the detector and the detector output, and Figure 3 is a diagram showing the relationship between the incident X-ray intensity on the detector and the detector output. A diagram showing the relationship between the count and the X-ray tube current, Figure 4 is a diagram showing the relationship between the count number of the pC counter and the intensity of xi incident on the pC counter, and Figure 5 is a diagram showing the relationship between the count change rate R4t of 13
iI4 A line diagram showing changes in response to X-ray counts, Figure 6 is a schematic diagram showing an example of an apparatus suitable for carrying out the present invention, and Figure 7 is a line showing the relationship between green density variation and measurement time for each thickness. 8 is a line diagram showing the change in green density when no correction is made by the method of the present invention, and FIG. 9 is a line IA showing the change in green density when the correction is made by the method of the present invention. l: X-ray tube, 2: Zr reflector, 3: green sheet, ceramic tape, 4: collimator, 5: PC counter, 6: end air, 7: c frame, 8: laser thickness measuring device, 9a, 9b: Laser displacement meter. Thickness) Measurement time (See) Fig. 7 Fig. 1 Fig. 2 X-ray tube bA) Fig. 3 Fig. 4 Clearance

Claims (1)

[Claims] 1. Regarding the ceramic tape (3), the areal density ρt is measured by a method in which a proportional counter (5) receives transmitted fluorescent X-rays, and the thickness t is separately measured with a thickness measuring device, and the areal density is determined. In the method of calculating the density ρ by dividing by the thickness, the measured value of the areal density is calculated using the following formula (1) N-N_2
=(N_0-N_s)■^-^ρ^t^/^K...(
1) Principle formula where N: transmitted X-ray detection count after correction (c
ps) t: Thickness of ceramic tape (m) ρ: Density (g/m^3) K: Reciprocal of absorption coefficient of ceramic tape for X-rays (
g/m^3) N_0: Transmitted X-ray detection count at t=0 (cps
) N_s: Transmitted X-ray detection count at t=∞ (cps
), N, N_0, N_ should be substituted into equation (1).
The s value has the following formula (2) ▲ Numerical formula, chemical formula, table, etc. ▼ ... (2) Numerical conversion formula where N: Corrected transmitted X-ray detection count number (cps) N^*: Measured Number of transmission X-ray detection counts (cps) N_c: Number of transmission X-ray detection counts (cps) during the latest calibration under the standard calibration conditions N_c_i: Initial transmission X-ray detection when creating a calibration curve under the standard calibration conditions Count number (cps) C_1: Constant C_2: A high-precision density measurement method for ceramic tape, characterized by substituting an N value corrected by a constant. 2. The method for high-precision density measurement of a ceramic tape according to claim 1, wherein the thickness is measured by a thickness measuring device while controlling the temperature of the thickness measuring device.