CN116972759A - Method for non-focusing testing thickness of organic coating - Google Patents
Method for non-focusing testing thickness of organic coating Download PDFInfo
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- 238000012360 testing method Methods 0.000 title claims abstract description 142
- 238000000576 coating method Methods 0.000 title claims abstract description 135
- 239000011248 coating agent Substances 0.000 title claims abstract description 131
- 238000000034 method Methods 0.000 title claims abstract description 31
- 238000001228 spectrum Methods 0.000 claims abstract description 57
- 238000010998 test method Methods 0.000 claims abstract description 28
- 230000000630 rising effect Effects 0.000 claims description 40
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 claims description 23
- 239000002184 metal Substances 0.000 claims description 18
- 229910052751 metal Inorganic materials 0.000 claims description 18
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 15
- 238000004519 manufacturing process Methods 0.000 claims description 13
- 229910052802 copper Inorganic materials 0.000 claims description 10
- 239000010949 copper Substances 0.000 claims description 10
- 238000000985 reflectance spectrum Methods 0.000 claims description 4
- 238000004364 calculation method Methods 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 17
- 230000008569 process Effects 0.000 description 6
- 238000005476 soldering Methods 0.000 description 6
- 239000011889 copper foil Substances 0.000 description 5
- 238000001514 detection method Methods 0.000 description 5
- 238000002329 infrared spectrum Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000003466 welding Methods 0.000 description 5
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- 150000001875 compounds Chemical class 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
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- 238000004458 analytical method Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
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- 238000000691 measurement method Methods 0.000 description 2
- 238000004445 quantitative analysis Methods 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 238000004381 surface treatment Methods 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
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- 238000011161 development Methods 0.000 description 1
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- 230000003670 easy-to-clean Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
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- 239000002346 layers by function Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
- G01B11/0625—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of absorption or reflection
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Abstract
The invention provides a method for testing the thickness of an organic coating in a non-focusing way, which comprises the steps of firstly obtaining an infrared reflection spectrum of a standard sample by adopting a non-focusing test method, counting infrared characteristic peak areas in a preset wave number range, establishing a correlation between the infrared characteristic peak areas and the thickness of the organic coating to form a relational expression, obtaining the infrared characteristic peak areas of a sample to be tested by adopting the same test method, and carrying out calculation in the relational expression, thereby determining the thickness of the organic coating to be tested. According to the invention, the infrared reflection spectrum with better accuracy and better stability is obtained through the non-focusing test method, the test area during infrared reflection spectrum test is increased in a manner of artificially generating controllable focusing errors, the test signal is enhanced, the test errors are reduced, the stability of the test result and the accuracy and reliability of the thickness test of the organic coating to be tested on the sample to be tested are improved, and the quick, nondestructive and accurate test of the thickness of the organic coating is realized.
Description
Technical Field
The invention relates to the technical field of testing, in particular to a method for testing the thickness of an organic coating in a non-focusing manner.
Background
Organic coating is often used as functional layer such as anticorrosive coating widely in industrial technology, and the current measuring method of organic coating thickness includes chemical dissolution quantitative method and film thickness measuring instrument measuring method; however, there are problems associated with accurate measurement of the thickness of the organic coating in both of these ways: if the chemical dissolution quantitative method is adopted for analysis, the organic coating can be damaged firstly, and secondly, the method is carried out on the premise that the thickness of the organic coating is quite uniform, and when the thickness of the organic coating is not quite uniform, the quality of the organic coating in a specific area can not be evaluated; the measuring principle of the film thickness measuring instrument on the metal layer generally adopts methods such as magnetic attraction, eddy current or optical rays to measure the film thickness, the measuring range of the thickness of the organic coating is narrow, and particularly the data error is large when the thickness of the organic coating is small. In addition, there are some applications of using non-destructive testing methods such as infrared spectrum to test the thickness of the organic coating, but the application range is extremely limited when using the infrared spectrum testing method to test the thickness of the organic coating on the metal layer, for example, when the infrared reflection spectrum-based testing method affects the uneven surface of the thickness of the organic coating due to the roughness of the metal layer, the accuracy of the thickness test is affected, so in particular, the conventional infrared reflection spectrum-based testing method is not suitable for detecting the thickness of an OSP film (Organic Solderability Preservatives, organic solder mask) on a PCB (Printed Circuit Board, also called a printed circuit board).
The rapid development and wide application of integrated circuits enable the variety and application of PCBs to develop rapidly, and the requirements on the reliability and precision of PCB fabrication are also increasing, wherein copper is used as a main component of a circuit pattern on a PCB to realize the important role of connecting each circuit layer and conducting of the PCB, but copper is used as an active chemical substance, and is easily oxidized or vulcanized when exposed to air, so that the problem of poor fabrication may occur in the subsequent fabrication process, such as high-temperature welding, and the device installation on the surface of the PCB and the reliability of the finally fabricated PCB product are affected. Therefore, in the actual PCB manufacturing process, after the outer layer circuit of the PCB is formed by etching the surface copper foil, a surface treatment process is further performed on the etched copper circuit to prevent the outer layer copper from being oxidized and provide a soldering surface for device mounting on the surface of the PCB.
The OSP film is one of the main processes for carrying out surface treatment on the PCB, and forms a layer of organic film on the clean bare copper surface in a chemical way, so that the copper foil on the PCB surface can be well protected due to oxidation resistance, thermal shock resistance and moisture resistance of the OSP film, and meanwhile, the OSP film is easily and rapidly removed by the soldering flux in the subsequent high-temperature welding process, so that the exposed clean copper surface can be immediately combined with molten soldering tin to form a firm welding spot in extremely short time; meanwhile, the OSP film is generally manufactured by adopting an aqueous compound, the manufacturing process is simple, the economy is good, the environment is protected and harmless, and the OSP film directly acts on the surface of the PCB, so that the damage repair or update is facilitated, and the PCB can be reused conveniently. However, in the actual manufacturing process, the film thickness generated by the OSP film is usually smaller (in the order of μm), so that the OSP film is easy to damage during transportation and storage, the protection effect on the copper foil on the surface of the PCB is reduced, and the welding performance in the subsequent high-temperature welding process is greatly reduced; however, if the thickness of the OSP film is too thick, the cost is increased, the soldering flux is not easy to clean the OSP film during high-temperature soldering, the production efficiency is reduced, and the subsequent soldering performance is affected, so that the thickness of the OSP film on the surface of the PCB must be controlled within a certain range. Controlling the thickness of the OSP film depends on the accurate measurement of the thickness of the OSP film, and is preferably a nondestructive and accurate measurement method; the OSP film is directly attached to the etched copper foil surface on the surface of the PCB, and the thickness unevenness is difficult to accurately test by the traditional nondestructive measurement method of the infrared reflection spectrum, in particular, in the traditional test method of the infrared reflection spectrum, the infrared light emitted is usually required to be focused on a tested sample and then tested, the area of the sample covered by the focusing point is the test area on the sample, the accuracy of measurement is ensured by the smaller test area, but the fed-back test signal is also smaller, and the characteristic peak in the obtained infrared reflection spectrum is easily influenced by the uneven surface of the coating and the thickness of the coating to generate larger fluctuation, so that the accuracy and the stability of measurement are influenced.
Disclosure of Invention
The present invention aims to overcome at least one of the above-mentioned drawbacks of the prior art by providing a method for non-focused testing of the thickness of an organic coating for enabling a fast, non-destructive, accurate measurement of the thickness of the organic coating.
The technical scheme provides a method for testing the thickness of an organic coating in a non-focusing way, which comprises the following steps:
s1, based on correlation reference of a standard sample, the standard sample comprises a metal base layer and a reference organic coating which is arranged on the surface of the metal base layer and has known thickness;
measuring an infrared reflection spectrum of a reference organic coating formed on a standard sample by using a non-focusing test method;
counting infrared characteristic peak areas in a preset wave number range by an infrared reflection spectrum of the reference organic coating;
determining a correlation between the thickness of the organic coating and an infrared characteristic peak area based on the thickness of the reference organic coating and an infrared reflectance spectrum of the reference organic coating;
s2, testing a sample to be tested, wherein the sample to be tested comprises a metal base layer consistent with a standard sample and an organic coating to be tested, which is arranged on the surface of the metal base layer;
measuring an infrared reflection spectrum of an organic coating to be measured formed on a sample to be measured by adopting a non-focusing test method;
counting the infrared characteristic peak area of a preset wave number range by using the infrared reflection spectrum of the organic coating to be detected;
calculating the thickness of the organic coating to be detected from the infrared characteristic peak area of the organic coating to be detected based on the correlation between the thickness of the organic coating and the infrared characteristic peak area determined in the step S1;
the non-focusing test method comprises the following steps: on the basis of focusing the adopted infrared testing device based on the tested sample, the tested sample is vertically lifted by a certain distance to generate focusing error, and the infrared reflection spectrum of the tested sample is obtained through testing under the state of focusing error.
In the technical scheme, the thickness of the organic coating is mainly tested by adopting a non-focusing test method through an infrared test device, under the irradiation of infrared light, compound molecules in the organic coating can absorb infrared light with specific wavelength, thereby generating infrared absorption spectrum or infrared reflection spectrum with corresponding infrared characteristic peaks; specifically, in the technical scheme, firstly, a non-focusing test method is adopted to obtain an infrared reflection spectrum of a standard sample, infrared characteristic peak areas in a preset wave number range are counted, correlation between the infrared characteristic peak areas in the preset wave number range and the thickness of an organic coating on the standard sample is established, a relational expression is formed, based on the relational expression obtained by the standard sample, the infrared reflection spectrum of a sample to be detected is obtained through the non-focusing test method, the infrared characteristic peak areas in the preset wave number range are counted, and the thickness of the organic coating to be detected on the sample to be detected can be obtained through quick calculation by taking the relational expression into. The infrared reflection spectrum of the tested sample with better accuracy and better stability is obtained by adopting a non-focusing test method, and usually in the traditional infrared spectrum test method, when the tested sample is focused, an organic coating with a certain film thickness is coated on a metal layer, so that some fine focusing errors can be inevitably generated during focusing, and when the area of a focusing point is smaller and a test signal is weaker, the fine focusing errors can cause larger influence on the test precision, so that unavoidable test errors are caused; the non-focusing test method artificially generates enough and controllable focusing error by vertically lifting a tested sample by a certain distance after focusing, and increases the irradiation area of infrared light on the sample, namely increases the test area, so that when the infrared characteristic peak area is counted, the preset wave number range counted for the tested organic coating is correspondingly increased, the test signal is enhanced, the fine focusing error during focusing is eliminated, and the test error is reduced; meanwhile, after the test area is increased, the formed infrared reflection spectrum graph comprises the test result of the whole test area, so that the influence of uneven coating surface and different coating thickness in the test area is also included, the variation of test data generated by uneven coating surface and different coating thickness during the test is reduced, the stability of the test result is improved, the stability and the reliability of the correlation between the counted infrared characteristic peak area in the preset wave number range and the thickness of the organic coating are further improved, and the accuracy and the reliability of the thickness test of the organic coating to be tested on the sample to be tested are further improved.
Further, the infrared testing device adopts an FTIR (Fourier transform infrared absorption spectrometer) infrared microscope, and the infrared reflection spectrum of the tested sample is formed based on the reflection mode test of the FTIR infrared microscope; the detection principle of FTIR is that infrared light with all wavelengths is detected simultaneously by using an interferometer, and detected data are converted into a secondary infrared spectrum by mathematical operation of Fourier transform, so that the detection efficiency is extremely high, few optical elements are used, no grating or prism beam splitter is arranged, the loss of light is reduced, infrared light signals are further increased by interference, the radiation intensity reaching the detector is high, the signal-to-noise ratio is high, and meanwhile, the FTIR is used for data acquisition according to the full wave band, and the spectrum obtained by testing is the result obtained by averaging multiple data acquisition, so that the detection has higher accuracy than the traditional infrared spectrometer; by adopting the FTIR reflection mode for testing, the method has the advantages of strong characteristics, quick analysis and no damage to the sample when the infrared reflection spectrum testing method is used for measuring the thickness of the organic coating, and improves the efficiency and accuracy of the test, thereby realizing the quick, nondestructive and accurate test of the thickness of the organic coating. Further, the spatial resolution of FTIR can be further improved by adding a microscopic device to FTIR, further improving the accuracy of the thickness test of the organic coating.
Further, the step S1 specifically includes the following steps:
s11, defining a standard sample series, and manufacturing a plurality of standard samples with reference organic coatings with different thicknesses on the surfaces to form the standard sample series with thickness gradients;
s12, testing a standard sample series, testing and obtaining infrared reflection spectrums of the standard sample series based on a non-focusing test method, and respectively counting infrared characteristic peak areas in a preset wave number range;
s13, correlation fitting, namely correspondingly fitting the reference organic coating thickness of the standard sample series and the infrared characteristic peak area of the preset wave number range, calculating the correlation of the standard sample series and forming a relational expression.
Preferably, in the step S13, the correlation between the reference organic coating thickness of the standard sample series and the infrared characteristic peak area of the predetermined wavenumber range is not less than 0.95.
In the technical scheme, the specific step of providing the correlation reference between the infrared characteristic peak area and the thickness of the organic coating for the sample to be measured based on the standard sample further comprises the following steps: defining a standard sample series, testing the standard sample series and fitting the correlation. When defining a standard sample series, forming the standard sample series with thickness gradient by manufacturing a plurality of standard samples with reference organic coatings coated on the surfaces with different thicknesses, specifically, designing the thickness gradient range of the standard sample series to be wide enough to cover the thickness of the organic coating to be measured on the sample to be measured so as to ensure that the correlation and relation between the infrared characteristic peak area calculated subsequently and the thickness of the organic coating are suitable for measuring the thickness of the organic coating to be measured; meanwhile, the spacing between the thickness gradients of the standard sample series around the thickness of the organic coating to be measured should be reasonably dense, so that the accuracy and reliability of the correlation and relation between the infrared characteristic peak area calculated subsequently and the thickness of the organic coating are ensured. After defining and manufacturing standard sample series with reasonable range and distance, obtaining infrared reflection spectrum of the standard sample series based on the same focusing error test, and respectively counting infrared characteristic peak areas of a preset wave number range, further correspondingly fitting the reference organic coating thickness of the standard sample series and the infrared characteristic peak areas of the preset wave number range, calculating the correlation of the standard sample series and forming a relation. Preferably, in the calculation, the correlation between the reference organic coating thickness and the infrared characteristic peak area in the predetermined wave number range is not less than 0.95 as a significant correlation, and the relational expression formed by the test can be used in the following, and the thickness of the organic coating to be measured on the sample to be measured is obtained by substituting the infrared characteristic peak area in the predetermined wave number range of the sample to be measured into the relational expression.
Further, the predetermined wave number range corresponds to a reflection peak range of a main component in the reference organic coating.
In the technical solution, the frequency unit in the spectroscopy of atoms, molecules and the like usually adopts wave numbers, the wave numbers are the reciprocal of the wavelength, and are used for representing the wave number of light in each unit length in the light propagation direction, and as the compound molecules in the reference organic coating can absorb infrared light with specific wavelength and generate infrared reflection characteristic peaks in a specific wavelength range in the infrared reflection spectrum, the predetermined wave number range in the technical solution corresponds to the reflection peak range in the infrared reflection spectrum generated under the excitation of the infrared light of the main component in the organic coating.
Further, in the non-focusing test method, an optimal rising distance exists for the vertical rising distance of the tested sample, and in the optimal rising distance state, the infrared characteristic peak area of the infrared reflection spectrum of the tested sample in the preset wave number range is obtained through testing to be maximum, and the variation coefficient of the peak area is minimum.
Specifically, before the step S12, the following step S111 is further included:
s111, determining the optimal rising distance, testing infrared reflection spectrums of the standard sample series under a plurality of different vertical rising distances based on the standard sample series, and respectively counting infrared characteristic peak areas in a preset wave number range under different vertical rising distances to form a rising distance gradient; and the vertical rising distance with the largest infrared characteristic peak area and the smallest variation coefficient of the peak area of the infrared reflection spectrum of the standard sample series in the preset wave number range is taken as the optimal rising distance.
In the technical scheme, the non-focusing test method is realized by vertically lifting the sample to be tested by a certain distance, but the purpose of expanding the test area can be realized by lifting the sample, the test area can be increased due to the increase of the vertical lifting distance of the sample, but the lifting distance is too large, so that the infrared signal is reflected out of the receiving range of the detector, the signal is not received by the detector, and the signal strength is weakened instead. Meanwhile, due to errors such as focusing errors, uneven coating surfaces, coating thickness differences and the like, the stability of a test result is correspondingly affected by the change of the test area, so that the stability is in a trend of increasing first and then decreasing second, and therefore, an optimal rising distance exists when a sample is lifted to increase the test area, the test area of the tested sample is maximum, the stability is best, and the infrared characteristic peak area of an infrared reflection spectrum of the tested sample in a preset wave number range is maximum, and the variation coefficient of the peak area is minimum. Therefore, after standard sample series with reasonable range and distance are defined and manufactured, the manufactured standard sample series is adopted to determine the optimal rising distance, so that a data basis is provided for non-focusing tests of the follow-up standard samples and the samples to be tested. Specifically, for testing infrared reflection spectra of the standard sample series under a plurality of different vertical rising distances, a rising distance gradient is formed, infrared characteristic peak areas of a preset wave number range under different vertical rising distances are respectively counted, and the vertical rising distance with the largest infrared characteristic peak area and the smallest peak area variation coefficient of the infrared reflection spectra of the measured standard sample series under the preset wave number range is taken as the optimal rising distance.
Furthermore, the technical scheme can be used for testing the thickness of the OSP film on the PCB, wherein the metal base layers of the standard sample and the sample to be tested are copper, and the reference organic coating on the standard sample and the organic coating to be tested on the sample to be tested are both OSP films formed on the outer copper circuit patterns of the PCB.
In one embodiment of the present disclosure, when the thickness of the OSP film on the PCB is not being tested in focus, the tested sample is raised vertically by 0.4mm based on the focus of the tested sample to generate a focus error; when the infrared characteristic peak in the preset wave number range in the infrared reflection spectrum under the unfocused test is calculated, the preset wave number range is 2937-2880cm -1 ；
The relation between the thickness of the OSP film to be measured and the infrared characteristic peak area of the preset wave number range under the non-focusing test is obtained after fitting the standard sample: the thickness of the OSP film to be measured= 0.70309 × (infrared characteristic peak area of a predetermined wave number range under unfocused test) -0.0491 (μm), and its correlation is 0.9827.
Compared with the prior art, the invention has the beneficial effects that:
1. performing unfocused test on the tested sample by using an infrared testing device to generate a corresponding infrared reflection spectrum, and accurately measuring the thickness of the organic coating according to the lambert-beer law, so that the infrared testing device can realize rapid and nondestructive test on the thickness of the organic coating under the condition of no contact with the organic coating;
2. the infrared reflection spectrum with better accuracy and better stability is obtained by adopting a non-focusing test method; by vertically lifting the tested sample by a certain distance after focusing, enough and controllable focusing errors are artificially generated, the irradiation area of infrared light on the sample is increased, namely the test area is increased, the test signal is enhanced, the fine focusing errors during focusing are eliminated, and the test errors are reduced; meanwhile, after the test area is increased, the formed infrared reflection spectrum graph comprises the test result of the whole test area, the influences of uneven coating surfaces and different coating thicknesses in the test area are dispersed, the variation coefficient of test data is reduced, the stability of the test result is improved, and further the stability and reliability in the process of constructing correlation between the infrared characteristic peak area of the counted preset wave number range and the thickness of the organic coating are improved, so that the accuracy and reliability of thickness test of the organic coating to be tested on a sample to be tested are improved.
Drawings
FIG. 1 is a flow chart of a method of unfocused testing of organic coating thickness in accordance with the present invention.
FIG. 2 is a flow chart of providing correlation and optimal rise distance reference based on a standard sample series in the present invention.
FIG. 3 is a schematic diagram of the optical path of the unfocused test method of the present invention.
FIG. 4 is a graph showing the comparison of the peak area and the variation coefficient of the peak area in the focusing mode after the sample rises by 0.4mm in example 2 of the present invention
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the invention. For better illustration of the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the actual product dimensions; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
Example 1
As shown in fig. 1-3, the present technical solution provides a method for non-focusing testing the thickness of an organic coating, comprising the following steps:
s1, based on correlation reference of a standard sample, the standard sample comprises a metal base layer and a reference organic coating which is arranged on the surface of the metal base layer and has known thickness;
measuring an infrared reflection spectrum of a reference organic coating formed on a standard sample by using a non-focusing test method;
counting infrared characteristic peak areas in a preset wave number range by an infrared reflection spectrum of the reference organic coating;
determining a correlation between the thickness of the organic coating and an infrared characteristic peak area based on the thickness of the reference organic coating and an infrared reflectance spectrum of the reference organic coating;
s2, testing a sample to be tested, wherein the sample to be tested comprises a metal base layer consistent with a standard sample and an organic coating to be tested, which is arranged on the surface of the metal base layer;
measuring an infrared reflection spectrum of an organic coating to be measured formed on a sample to be measured by adopting a non-focusing test method;
counting the infrared characteristic peak area of a preset wave number range by using the infrared reflection spectrum of the organic coating to be detected;
calculating the thickness of the organic coating to be detected from the infrared characteristic peak area of the organic coating to be detected based on the correlation between the thickness of the organic coating and the infrared characteristic peak area determined in the step S1;
the specific method for the unfocused test comprises the following steps: on the basis of focusing the adopted infrared testing device based on the tested sample, vertically lifting the tested sample by a certain distance to generate a focusing error, and testing to obtain an infrared reflection spectrum of the tested sample under the state of the focusing error; the non-focusing test method has the advantages that the tested sample is vertically lifted for a certain distance after focusing, so that enough and controllable focusing error is artificially generated, the test area is increased, the error during focusing is eliminated, and the test error is reduced; meanwhile, after the test area is increased, the formed infrared reflection spectrum graph includes the test result of the whole test area, so that the influence of uneven coating surfaces and different coating thicknesses in the test area is also included, the variation of test data generated by uneven coating surfaces and different coating thicknesses in the test is reduced, and the stability of the test result is improved.
Preferably, the infrared testing device may employ an FTIR infrared microscope, and the obtained infrared reflection spectrum is formed based on a reflection mode test of the FTIR infrared microscope; the FTIR infrared microscope simultaneously detects infrared light with all wavelengths by using an interferometer, so that infrared light signals are increased, the radiation intensity is high, the signal-to-noise ratio is high, detected data are converted into a secondary infrared spectrum by means of mathematical operation of Fourier transformation, the detection efficiency is extremely high, the spatial resolution of a testing device is improved by means of full-band detection and an additional microscopic device, and the accuracy of thickness testing of an organic coating is improved.
Further, the step S1 specifically further includes the following steps:
s11, defining a standard sample series, and manufacturing a plurality of standard samples with reference organic coatings with different thicknesses on the surfaces to form the standard sample series with thickness gradients; specifically, the thickness gradient range of the standard sample series should be designed to be wide enough to cover the thickness of the organic coating to be measured on the sample to be measured, so as to ensure that the correlation and relation between the infrared characteristic peak area calculated subsequently and the thickness of the organic coating are suitable for measuring the thickness of the organic coating to be measured; meanwhile, the spacing between the thickness gradients of the standard sample series around the thickness of the organic coating to be measured should be reasonably dense, so that the accuracy and reliability of the correlation and relation between the infrared characteristic peak area calculated subsequently and the thickness of the organic coating are ensured;
s12, testing a standard sample series, testing and obtaining infrared reflection spectrums of the standard sample series based on a non-focusing test method, and respectively counting infrared characteristic peak areas in a preset wave number range;
s13, correlation fitting, namely correspondingly fitting the reference organic coating thickness of the standard sample series and the infrared characteristic peak area of the preset wave number range, calculating the correlation of the standard sample series and forming a relational expression.
Preferably, in step S13, the correlation between the reference organic coating thickness and the infrared characteristic peak area in the predetermined wavenumber range is not less than 0.95 as a significant correlation, and the thickness of the organic coating to be measured on the sample to be measured may be obtained by substituting the infrared characteristic peak area in the predetermined wavenumber range of the sample to be measured into the relational expression.
Further, the range of the predetermined wave number is determined by a reflection peak range corresponding to the main component in the reference organic coating.
Further, in the non-focusing test method, since the test area is increased due to the increase of the vertical rising distance of the sample, but the rising distance is too large, which causes that the infrared signal is reflected out of the receiving range of the detector, the detector can not receive the signal, the signal strength is weakened instead, and meanwhile, due to the errors of focusing error, uneven coating surface, difference of coating thickness and the like, the change of the test area also affects the stability of the test result correspondingly, so that the stability is in a trend of increasing first and then decreasing, therefore, when the sample is lifted to increase the test area, an optimal rising distance exists, the test area of the tested sample is maximized, the stability is best, and the infrared reflection spectrum of the tested sample is maximized in the infrared characteristic peak area of the preset wave number range, and the variation coefficient is minimized.
Specifically, to define the optimal rising distance of the tested sample, before the step S12 starts the unfocused test on the standard sample series, the following step S111 is further included:
s111, determining the optimal rising distance, testing infrared reflection spectrums of the standard sample series under a plurality of different vertical rising distances based on the standard sample series, and respectively counting infrared characteristic peak areas in a preset wave number range under different vertical rising distances to form a rising distance gradient; and the vertical rising distance with the largest infrared characteristic peak area and the smallest variation coefficient of the infrared reflection spectrum of the measured standard sample series in the preset wave number range is used as the optimal rising distance.
Example 2
The thickness of the OSP film on the PCB was tested by FTIR infrared microscope in this example, specifically, the reflection mode of the FTIR infrared microscope was used for testing with a clean gold mirror as the test background, a background scan of 32Scans, a sample scan of 64Scans, and a resolution of 4cm -1 The integral mode is G, and the integral characteristic peak wave number range is 2937-2880cm -1 ；
The specific test flow is as follows:
s11, manufacturing a PCB standard test board series of OSP films with the surface coverage thickness of copper foil of 0.09 mu m, 0.12 mu m, 0.13 mu m, 0.14 mu m, 0.21 mu m and 0.34 mu m;
s111, respectively testing infrared reflection spectrums of the PCB standard test board series under the focusing mode, the vertical rising distance of 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm and 0.6mm and the statistical wave number range of 2937-2880cm by using the PCB standard test board series -1 As a result, as shown in fig. 4, the FTIR characteristic peak area was gradually increased and then gradually decreased with an increase in the vertical rising distance of the sample, and when the vertical rising distance of the sample was 0.4mm, the average value of the FTIR characteristic peak area was measured to be maximum, and the coefficient of variation of the characteristic peak area was minimum. Therefore, the infrared reflection spectrum of the PCB standard test board series is 2937-2880cm in the wave number range -1 The vertical rising distance with the largest infrared characteristic peak area and the smallest variation coefficient is 0.4mm and is the optimal rising distance;
s12, testing by adopting a reflection mode of an FTIR infrared microscope, on the basis of FTIR focusing, raising a test platform to enable a sample to rise by 0.4mm for FTIR testing, and counting the thickness of an OSP film of a PCB standard test board series and the corresponding wave number range of 2937-2880cm -1 The infrared characteristic peak areas of (2) are shown in the following table:
| thickness of OSP film/. Mu.m | FTIR characteristic peak area |
| 0.0861 | 0.2138 |
| 0.1203 | 0.2260 |
| 0.1269 | 0.2322 |
| 0.1434 | 0.2596 |
| 0.2129 | 0.3394 |
| 0.3402 | 0.5412 |
S13, correspondingly fitting the thickness of the OSP film of the PCB standard test board series and the corresponding wave number range of 2937-2880cm -1 The data correlation is calculated as 0.9827, and the relation is formed as follows: thickness of OSP film to be measured= 0.70309 × (wave number range under unfocused test is 2937-2880cm -1 Infrared characteristic peak area) 0.0491 (μm);
s2, adopting a reflection mode of an FTIR infrared microscope, lifting the test platform to enable the OSP film to be tested to be lifted by 0.4mm on the basis of FTIR focusing, and testing and counting that the wave number range of the OSP film to be tested is 2937-2880cm -1 And (3) bringing the infrared characteristic peak area of the OSP film to be measured into the relational expression obtained in the step S13, and calculating the thickness of the OSP film to be measured.
It should be understood that the foregoing examples of the present invention are merely illustrative of the present invention and are not intended to limit the present invention to the specific embodiments thereof. Any modification, equivalent replacement, improvement, etc. that comes within the spirit and principle of the claims of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A method for non-focusing testing of organic coating thickness comprising the steps of:
s1, based on correlation reference of a standard sample, the standard sample comprises a metal base layer and a reference organic coating which is arranged on the surface of the metal base layer and has known thickness;
measuring an infrared reflection spectrum of a reference organic coating formed on a standard sample by using a non-focusing test method;
counting infrared characteristic peak areas in a preset wave number range by an infrared reflection spectrum of the reference organic coating;
determining a correlation between the thickness of the organic coating and an infrared characteristic peak area based on the thickness of the reference organic coating and an infrared reflectance spectrum of the reference organic coating;
s2, testing a sample to be tested, wherein the sample to be tested comprises a metal base layer consistent with a standard sample and an organic coating to be tested, which is arranged on the surface of the metal base layer;
measuring an infrared reflection spectrum of an organic coating to be measured formed on a sample to be measured by adopting a non-focusing test method;
counting the infrared characteristic peak area of a preset wave number range by using the infrared reflection spectrum of the organic coating to be detected;
calculating the thickness of the organic coating to be detected from the infrared characteristic peak area of the organic coating to be detected based on the correlation between the thickness of the organic coating and the infrared characteristic peak area determined in the step S1;
the non-focusing test method comprises the following steps: on the basis of focusing the adopted infrared testing device based on the tested sample, the tested sample is vertically lifted by a certain distance to generate focusing error, and the infrared reflection spectrum of the tested sample is obtained through testing under the state of focusing error.
2. The method of claim 1, wherein the infrared testing device employs an FTIR infrared microscope, and wherein the infrared reflectance spectrum is formed based on a reflectance mode test of the FTIR infrared microscope.
3. The method for non-focusing test of organic coating thickness according to claim 1, wherein the step S1 specifically comprises the steps of:
s11, defining a standard sample series, and manufacturing a plurality of standard samples with reference organic coatings with different thicknesses on the surfaces to form the standard sample series with thickness gradients;
s12, testing a standard sample series, testing and obtaining infrared reflection spectrums of the standard sample series based on a non-focusing test method, and respectively counting infrared characteristic peak areas in a preset wave number range;
s13, correlation fitting, namely correspondingly fitting the reference organic coating thickness of the standard sample series and the infrared characteristic peak area of the preset wave number range, calculating the correlation of the standard sample series and forming a relational expression.
4. A method of non-focusing testing an organic coating thickness according to claim 3, wherein in said step S13, the correlation between the reference organic coating thickness of the standard sample series and the infrared characteristic peak area of the predetermined wavenumber range is not less than 0.95.
5. The method of unfocused testing of organic coating thickness according to claim 1, wherein the range of predetermined wavenumbers corresponds to the range of reflection peaks of the principal components in the reference organic coating.
6. The method according to any one of claims 1 to 5, wherein in the non-focusing test method, there is an optimal rising distance of a vertical rising distance of the tested sample, and in the optimal rising distance state, the infrared characteristic peak area of the infrared reflection spectrum of the tested sample in a predetermined wave number range is the maximum and the variation coefficient of the peak area is the minimum.
7. The method of non-focusing on testing the thickness of an organic coating according to claim 6, further comprising the following step S111, prior to said step S12:
s111, determining the optimal rising distance, testing infrared reflection spectrums of the standard sample series under a plurality of different vertical rising distances based on the standard sample series, and respectively counting infrared characteristic peak areas in a preset wave number range under different vertical rising distances to form a rising distance gradient; and the vertical rising distance with the largest infrared characteristic peak area and the smallest variation coefficient of the peak area of the infrared reflection spectrum of the standard sample series in the preset wave number range is taken as the optimal rising distance.
8. The method of claim 1-7, wherein the metal base layer is copper, and the reference organic coating and the organic coating to be tested are both OSP films formed on an outer copper circuit pattern of the PCB.
9. The method of claim 8, wherein the distance that the sample is raised vertically is 0.4mm when the thickness of the OSP film on the PCB is measured in a non-focused manner.
10. The method for non-focusing test of organic coating thickness according to claim 9, wherein the predetermined wave number range is 2937-2880cm -1 ；
The thickness of the OSP film to be measured= 0.70309 × (infrared characteristic peak area of a predetermined wave number range under unfocused test) -0.0491, the correlation being 0.9827.
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| CN117288129A (en) * | 2023-11-27 | 2023-12-26 | 承德华实机电设备制造有限责任公司 | Method for detecting thickness of irradiation material contained in tray |
| CN117288129B (en) * | 2023-11-27 | 2024-02-02 | 承德华实机电设备制造有限责任公司 | Method for detecting thickness of irradiation material contained in tray |
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