JPH10311760A - Thermal-history judgment method and thermal-history display label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge a thermal history qualitatively and quantitatively by a method wherein a change in a fluorescence characteristic due to the thermal modification of a fluorescent substance placed under a heating environment together with an object to be heated is measured qualitatively and quantitatively and the relationship between the change amount of a fluorescence characteristic which is measured in advance and the thermal history is found. SOLUTION: A thermal-history display label 40 is composed of a heat-resistant resin film 42 which is composed of a heat-resistant resin to be bonded onto a face to be bonded and in which an adhesive material layer 41 is formed on the rear surface and of an information display pattern 43 which is printed on its surface and which contains a thermal-history labeling agent. As the thermal-history labeling agent, e.g. a compound such as anthracene or the like, its derivative or a substance which is modified to the chemical structure of a support medium is used. In the thermal-history display label 40, simultaneously with the application of the thermal history due to quick heat conduction from an object to be tested or due to heating from a heat source, the thermal-history labeling agent which is printed on the surface of the heat-resistant resin film 42 generates thermal modification corresponding to the thermal history. When the thermal history is detected, the component of fluorescence generated from the information display pattern 43 is converted into an electric signal so as to correspond as a heat exposure amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a judgment method for judging the heat history of an object placed in a heating environment and a heat history display label.

[0002]

2. Description of the Related Art Many industrial products made from such materials, including natural and synthetic chemicals and materials, are subject to heat generation or heat treatment in the reprocessing process during manufacture, use, or disposal. It is well known that heat absorption (abbreviated as heat exposure in the present invention) may cause deterioration of physical properties, performance, function, etc., and that the cause is mainly caused by chemical change of the material due to heat. It is.

It is clear that the degree of deterioration of various physical properties due to heat exposure is a function of the time of exposure to heat (abbreviated as heat exposure time in the present invention), but the rate of deterioration also depends on temperature. The higher the temperature, the faster the deterioration rate.
Therefore, in order to estimate or evaluate the degree of deterioration, it is not sufficient to simply measure the heat exposure time and the applied temperature, that is, the exposure temperature, and it is not sufficient to measure the integrated value of the heat exposure time and the exposure temperature, that is, the heat exposure time. You have to keep track of your history.

Conventionally, in the inspection of the exposure temperature to a component when an excessive heat treatment is performed, a temperature indicating material which changes its properties such as discoloration or melting at a specific temperature or higher has been used. In other words, a coating or label containing a temperature indicating material that reacts at a temperature higher than the temperature at which a failure or a change in physical properties is likely to occur is applied or affixed to the object to be heated, and the exposure temperature is determined based on a change in the color or property of the temperature indicating material after heating. Is to be inspected.

[0005] The temperature indicating material used for performing such an exposure temperature inspection is described in I.G. G. FIG. Farbeind
ustry has a patent from 1937 to 1941 [DRP: 665462 (1938), 699460].
(1940)], and those sold under the name Thermocolor are commercially available in Japan from RIKEN under the trade name of Thermopaint. Due to their thermal properties, they are reversible and irreversible. The latter chemicals, which are classified into two types and are used in tests of exposure temperature, include cobalt, nickel, iron, copper, chromium,
Salts such as manganese and lead are used, and these salts are
Amine or ammonium group, amine group,
Many contain carbonic acid groups, oxalic acid groups, and hydroxyl groups.

As a conventional method for evaluating the thermal history including the exposure temperature and the thermal exposure time, there has been reported a method of monitoring the amount of acid permeation using a redox dye and performing time / temperature integration. (U.S. Pat. No. 3,768,976
issue).

[0007] In addition, an azo dye and an epoxy compound are contained in microcapsules or the like, which are separated by microcapsules that melt or soften at a temperature in the range of 50 to 300 ° C. A heat history detection indicator utilizing the thermal diffusion of both of them and the change in hue caused by the chemical reaction accompanying the mixing has been devised (Japanese Patent Application Laid-Open No. 59-124956).

The problem that the heat history detection indicator disclosed in JP-A-59-124965 cannot be used at a temperature lower than the softening temperature and melting temperature of the partition walls of the microcapsules is solved by increasing the temperature. Is devised so that it is destroyed by internal pressure, and a nucleophilic compound and a compound that changes its hue by reacting with it are separately sealed,
There has been a report on a display material of heat exposure energy determined from the degree of color development occurring at the time of heat exposure (JP-A-63-3568).
No. 4).

In the prior arts relating to these thermal histories, the chemical reaction between chemical substances, in this case, the thermal diffusion phenomenon of the chemical substance occurring when a color-forming reaction is caused depends on the applied exposure temperature and the exposure time. However, the fact that the accumulated amount of the coloring substance generated by the reaction corresponds to the heat history,
This is visually or optically detected by associating this with the degree of change in hue.

[0010]

However, the conventional method of determining the exposure temperature is mainly for grasping the operating conditions and controlling the temperature in the heating process, so that it is possible to determine whether or not the heating has been performed at a specific temperature or higher. However, it was difficult to accurately grasp the integrated value of the temperature actually applied or generated and the duration thereof, that is, the heat history. For example, it has been impossible in principle to continue the heat treatment at a temperature lower than the temperature at which the temperature indicating material reacts or to inspect the heat history when the repetition occurs. Therefore, the evaluation of the reliability of electronic components and the like caused by the accumulation of fatigue and modification of the physical properties of the material, which is gradually promoted by the repetition of such heat treatment, is based on direct chemical analysis and failure analysis of individual materials and components. There was no other way than to use expensive equipment and long evaluation time for inspection. Further, with respect to organic materials such as plastics, there is no method for simply evaluating the thermal history, and there has been no other way but to perform precise instrumental analysis of the materials.

In a conventional method of evaluating the heat history, which is basically performed by visually identifying the change in the hue of a chemical substance caused by the heat treatment, that is, the degree of the change in the color, the heat exposure amount is reduced. Even if some quantitative information could be obtained, it was not enough for a rigorous evaluation. Alternatively, using an optical filter or spectroscope, detect the intensity of reflected light in a specific wavelength range,
A quantitative evaluation method for converting this into an electric signal has also been devised. In some fields, it is used as a densitometer. However, the use of reflected light as an information transmission method is generally expressed in gradations. However, it is not always effective as a method of recording and reading information.

An object of the present invention is to provide a heat history judgment method and a heat history display label for qualitatively and quantitatively judging an integrated value of a temperature and a continuous time, that is, a heat history, received by heating or generated by heat generation. Is to do.

[0013]

The heat history determination method of the present invention is a method for determining the heat history of an object to be heated placed in a heating environment. The qualitative and quantitative measurement of the change in the fluorescence characteristics due to the thermal denaturation of the fluorescent substance placed in the heating environment together with the object to be heated is measured. For the fluorescent substance, the relationship between the amount of change in the fluorescent property and the heat history is measured in advance as data, and based on the data, the heat history of the object to be heated is determined from the measured change in the fluorescent property.

For the measurement of the change in the fluorescence characteristics due to the thermal denaturation of the fluorescent substance, the change in the fluorescence intensity due to the thermal denaturation of the fluorescent substance may be used. May be used.

In the measurement of the change in the fluorescence characteristics due to the thermal denaturation of a fluorescent substance, a plurality of fluorescent substances having different fluorescent spectra are simultaneously used, and the combined fluorescent intensity of each fluorescent spectrum after the thermal denaturation of the plural fluorescent substances is measured. And changes in fluorescence wavelength may be used.

In the thermal history display label of the present invention, a chemical substance that changes its fluorescence characteristics due to thermal denaturation in a heating environment is used as a thermal history labeling agent for determining the thermal history.

It is preferable that the thermal history marker is formed as an information display pattern on a label. Also,
It is preferable that the change in the fluorescence characteristic of the chemical substance is at least one of a change in the fluorescence intensity and a change in the fluorescence wavelength.

Furthermore, an information display pattern printed with a thermally stable non-fluorescent ink or an information display pattern using a thermally stable fluorescent substance may be simultaneously provided, and an adhesive layer may be provided. May be.

That is, the thermal history determination method of the present invention that can achieve the above-mentioned object utilizes the property that the thermal denaturation of a chemical substance changes quantitatively in accordance with the thermal history and accumulates the change. After heating, changes in the intensity of fluorescence and changes in the shape of the fluorescence spectrum emitted from one or more denatured or undenatured chemical substances after heating are measured, and the previously measured changes in the intensity of the fluorescence and the wavelength shift amount of the fluorescence spectrum and the heat are measured. It is characterized in that the thermal history of the object to be heated is qualitatively and quantitatively determined based on the relationship with the history and the change in the intensity of the fluorescence and the wavelength shift amount of the fluorescence spectrum.

The use of a chemical substance that causes a change in the fluorescence characteristics before and after heating, the fluorescence emitted from the chemical substance,
That is, the emitted light can be used as the heat history information, and as a result, a larger amount of information can be handled than when the reflected light is used. Quantitative evaluation of the thermal history can be performed basically by converting the optically detected emitted light into an electrical signal.For example, by associating the emitted light intensity and the thermal history in an arbitrary wavelength range Done. Further, by using the fluorescence intensity between arbitrary plural wavelength ranges and the comparison value thereof, that is, the intensity ratio, more information can be used and the reliability of the thermal history information can be improved.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In describing embodiments of the present invention, specific contents included in terms used will be described.

The term "thermal denaturation" as used herein refers to a change in the structure or state of a chemical substance caused by heating, such as a chemical reaction involving a change in the chemical structure such as decomposition, oxidation, reduction, addition, isomerization, or polymerization. , Melting, diffusion, emulsification, change in state without a chemical reaction such as orientation, especially if it involves a change in the structure or state that can change the fluorescence characteristics of a chemical substance before and after heating, the style is particularly Not limited.

The fluorescent substance of the present invention is a substance which itself has fluorescence, and changes into a non-fluorescent substance by heat denaturation, changes to a new fluorescent substance, or changes in properties. Refers to chemicals or combinations of chemicals that behave as fluorescent or non-fluorescent, but even if the chemical itself before heating is non-fluorescent,
There is no particular limitation as long as it is a chemical substance or a combination of chemical substances that changes into a fluorescent substance due to thermal denaturation, or creates a state that emits fluorescence by interaction with another chemical substance. Preferably, it is desirable to use a chemical substance in which the change before and after the heat treatment becomes clearer, the fluorescence intensity is strong, or the change in the emission wavelength range largely changes before and after the heating.

As specific examples of chemical substances, when utilizing the change in fluorescence intensity, anthracene, benzophenanthrene, pyrene, coronene and the like can be used.
These can be used singly or as a mixture of a plurality of them. When utilizing the change in fluorescence wavelength,
Substances having different ethylene chain lengths such as p-diphenylbenzene can be used.

The fluorescence characteristics used in the present invention refer to the intensity of fluorescence obtained at the time of irradiation with excitation light in an arbitrary wavelength range, the center wavelength of the fluorescence spectrum, the fluorescence color or the deflection of fluorescence, and the like before and after heating. There is no particular limitation as long as the change in physical quantity represented by the above can be quantitatively detected, but it is preferable to use the fluorescence intensity in an arbitrary wavelength region or the intensity ratio of the fluorescence between arbitrary wavelength regions in terms of easy inspection.

In the present invention, the desired temperature range at which the chemical substance to be measured is denatured differs depending on the heating process of the object to be heated and cannot be limited. Then, the temperature is about 150 to 400 ° C. during the mounting process of electronic components, that is, about 150 to 400 ° C. at the time of soldering. As described above, the applicable range of the present invention is not limited to these temperature ranges.

The form of use of the fluorescent substance used for determining the thermal history of the object to be heated according to the present invention is such that the fluorescent substance can be easily brought into close contact with the test object like a paint or a label. In general, it is used by coating or affixing it to the test object, and then spraying a part or wide area of the object to be heated using a coating device such as a spray. Can also be formed.

The fluorescence of the chemical substance subjected to the heat treatment is measured by measuring the light containing the excitation wavelength of the chemical substance attached to the object to be heated or the fluorescent substance formed secondarily by thermal denaturation, preferably the fluorescence. The excitation light not containing light in the emission wavelength range is taken out using a spectroscope, an interference filter, a band-pass filter, or the like, and irradiated onto the object to be heated, preferably uniformly. The fluorescence emitted at this time can be measured for fluorescence intensity at an arbitrary wavelength using various photodetectors, for example, a photomultiplier tube or a photodiode, or the fluorescence spectrum can be measured using a spectroscope and a photodiode array together. ,
The change in the spectrum shape is quantitatively or qualitatively measured as the shift amount of the wavelength, and the heat history added from the change amount is quantitatively determined. When a plurality of fluorescent substances having different emission wavelengths are used, it is possible to visually identify a change in the color of synthetic fluorescence emitted from the fluorescent substance after heating. When utilizing the change in the fluorescence wavelength, it is only necessary to pay attention to the characteristic, for example, the center wavelength of the fluorescence, and since this value does not depend on the intensity of the excitation light, it is necessary to strictly control the intensity of the irradiation light source. And not.

The concept of thermal exposure is used to explain the principle of the present invention. The degree of change in the physical properties of the object to be heated or the reliability as a part due to the heat history, which is the object of the determination of the present invention, generally corresponds to the level of the temperature to which the object to be heated was exposed and the time when the temperature was added. In particular, it is considered that this corresponds to an integral amount of the temperature level exceeding the stable temperature range of the object to be heated and the time to which the temperature is applied. This integrated value is expressed by the concept of heat exposure. Specifically, a fluorescent substance is attached to the same object to be heated as the object to be determined in the state of measurement,
Heating is performed at a plurality of temperatures within the temperature range expected to be added and at a plurality of expected durations and repetition times, and the resulting change in the fluorescent properties due to thermal denaturation of the fluorescent substance is measured. As data related to history,
The heat history is determined based on the change in the fluorescent characteristic of the fluorescent substance of the object to be heated, which is determined as the change in the fluorescent characteristic, which is considered to correspond to the change in the heat exposure degree. In addition, the change in the physical properties of the heated object after heating is evaluated by chemical analysis or failure analysis to determine the correlation with the heat history, and the change in the fluorescent characteristics of the fluorescent material corresponding to the heat history indicates the reliability of the heated material. By providing a threshold value that can maintain reliability, it is also possible to easily evaluate reliability.

Next, in the embodiment of the thermal history judgment method of the present invention, (1) a case where a change in fluorescence intensity is used after a heat treatment of a fluorescent substance, and (2) a case where a change in fluorescence wavelength is used. , (3) Each case of utilizing changes in fluorescence intensity and fluorescence wavelength will be described.

(1) Using a Change in Fluorescence Intensity A description will be given of a method of determining a thermal history using a change in fluorescence intensity due to thermal denaturation of a fluorescent substance. FIG. 1 is an explanatory diagram of the relationship between the relative fluorescence intensity and the heat exposure. FIG. 1A is a schematic graph of the fluorescence spectrum of a chemical substance after performing a heat treatment while changing the heat exposure in a stepwise manner. (B) is a schematic graph showing the relationship between the relative fluorescence intensity and the heat exposure Q at an arbitrary wavelength λ ₀ after the heat treatment performed in (a), and the horizontal axis of (a) represents the wavelength and the vertical axis. The axis represents the relative intensity of the fluorescence, the horizontal axis in (b) represents the heat exposure Q, and the vertical axis represents the relative fluorescence intensity.

Any wavelength λ in FIG.₀At this wavelength
Intensity I after each heat treatment in ₁ ~ I_Three Each
Fluorescence intensity corresponding to the heat exposure received by these heat treatments.
The applied thermal exposure, or thermal history,
Can be guessed. The fluorescence intensity after heating is
Continuous if the predetermined integral value of temperature and time during heating is the same
Or thermal decomposition of fluorescent substance even with intermittent heating
As long as the temperature is higher than the temperature
As long as the total amount is the same, the fluorescence intensity corresponding to that value
The change can be determined with good reproducibility.

(2) Use of Change in Fluorescence Wavelength A description will be given of a method of judging a thermal history using a change in fluorescence wavelength accompanying thermal denaturation of a fluorescent substance. FIG. 2 is an explanatory diagram of the relationship between the center fluorescence wavelength and the heat exposure degree. FIG. 2A shows a stepwise change to a fluorescent substance whose center wavelength changes from λ ₀ to λ _{3 due} to thermal denaturation accompanying heating. Is a schematic graph of a fluorescence spectrum before and after adding different thermal histories to (a), (b) is a center wavelength λ of each fluorescence spectrum obtained after the heat treatment performed in (a).
₁ is a schematic graph showing the relationship between ₁ , λ ₂ , and λ ₃ and the thermal exposure degree Q, wherein the horizontal axis of (a) represents the wavelength, the vertical axis represents the relative intensity of fluorescence, and the horizontal axis of (b) represents the thermal exposure. The degree Q and the vertical axis represent the wavelength.

The heat history can be quantitatively determined by associating the heat exposure with the wavelength shift amount of the fluorescence. If a fluorescent substance with a large wavelength shift is used,
A simple qualitative determination of the heat history based on a change in the color of emitted fluorescent light is also possible.

(3) When Using Changes in Fluorescence Intensity and Fluorescence Wavelength A method of determining a thermal history using changes in fluorescence intensity and fluorescence wavelength associated with thermal denaturation of a fluorescent substance will be described. FIG.
FIG. 4 is an explanatory view of the relationship between the fluorescence intensity and the fluorescence wavelength and the heat exposure degree. FIG. 4A shows two types of fluorescence having different wavelengths λ _a and λ _b , each having a central wavelength of fluorescence, and having different thermal stability. A schematic graph of a synthetic fluorescence spectrum obtained after heat treatment of these fluorescent substances using a combination of substances a and b, (b) is the relative fluorescence intensity at an arbitrary wavelength λ after the heat treatment performed in (a) 5A and 5B are schematic graphs showing the relationship between the heat exposure rate Q and the horizontal axis of FIG. 5A, the wavelength is plotted, the vertical axis is the relative intensity of fluorescence, the horizontal axis of FIG. Represents strength.

A combination of two types of fluorescent substances a and b having different center wavelengths of fluorescence at different wavelengths λ _a and λ _b and having different thermal stability is obtained by heat treatment of these fluorescent substances. Any wavelength λ of the fluorescence spectrum
By associating the amount of change in the fluorescence intensity and the amount of change in the center wavelength of the spectrum of the synthesized fluorescence with the amount of heat exposure, the heat history can be determined qualitatively and quantitatively. Although FIG. 3B shows the relationship between the relative fluorescence intensity and the heat exposure, the heat history can be determined based on the relationship between the wavelength and the heat exposure similarly to FIG. 2B.

As described in the above embodiment (2),
When trying to obtain the same effect by using a single fluorescent substance, it is often difficult to select a chemical substance that obtains the desired fluorescent characteristics, but as described in the present embodiment, By combining a plurality of (two or more) chemical substances exhibiting different thermal stability and fluorescent properties, more chemical substances can be used.

Next, an embodiment of the heat history display label of the present invention will be described in detail with reference to the drawings. FIG. 4 is a schematic perspective view of a heat history display label according to the embodiment of the present invention. In the figure, reference numeral 40 denotes a heat history display label, 41 denotes an adhesive layer, 42 denotes a heat-resistant resin film, and 43 denotes an information display pattern. , 4
Reference numeral 4 denotes a release paper.

Referring to FIG. 4, as a basic embodiment of the heat history display label 40 of the present invention, an adhesive layer 41 made of a heat-resistant resin for bonding on a surface to be adhered is formed on the lower surface. A label comprising a heat-resistant resin film 42 and an information display pattern 43 containing a thermal history marker printed on the surface thereof is proposed. The present embodiment is for describing a basic function, and is not necessarily limited to this format as long as the label has an information display pattern 43 containing a fluorescent heat history labeling agent. .

As the heat-resistant resin film 42 used for the heat history display label 40 of the present invention, a thin film made of a heat-resistant resin such as a silicone resin, a polyimide resin, a polyester resin, an epoxy resin, and a phenol resin can be used.
For use in a high-temperature environment of 00 ° C. or higher, it is desirable to use a silicone or polyimide resin-based resin excellent in heat resistance and light transmittance. The adhesive layer 41 applied to the heat-resistant resin film also uses an adhesive mainly composed of a heat-resistant resin.

The shape of the information display pattern 43 printed on the surface of the heat resistant resin film 42 is not particularly limited as long as the heat history information can be detected quantitatively and with good reproducibility. From those coated uniformly with a thermal history marking material, those that print a single bar-shaped pattern with a certain area on a part of the label surface, and those that are arranged in a plurality of barcodes are proposed. . In particular, when simultaneously managing information on the object to be heated other than the heat history information, such as supplementary information such as a manufacturing date and a manufacturing number, a pattern made of a non-fluorescent or thermally stable fluorescent substance is allowed to coexist. It is also possible.

The thermal history labeling agent used in the label of the present invention is not particularly limited as long as it is a chemical substance or a combination of chemical substances whose fluorescence characteristics change quantitatively before and after heating. Can use a chemical substance whose fluorescent property changes. For use in the relatively high temperature range described in the present invention, for example, at around 200 ° C., anthracene, methylanthracene, benzanthracene, benzofluorene,
Anthramine, benzoflavone, aminoacridone, xanthone, pyrene, harmaline, lumazine, benzopyrene, aminoacridine, anthrol, anthrone, phenanthrene, rubrene, chrysene, kaempferol,
Compounds such as phenylnaphthalene, cresolphthalein, triphenylene, thioxanthone, phenoxazine, anthralphine, N-phenylnaphthylamine, and phenanthridine, and derivatives thereof and those obtained by modifying the chemical structure of a supporting medium can be used. Is prepared by dissolving or dispersing the same in various heat-resistant resins, and the information display pattern 43 is printed or applied to the heat-resistant resin film 42 for use. Since the fluorescence characteristics of the above-mentioned thermal history labeling material vary depending on the type or composition of the supporting medium or additive to be dispersed or dissolved, the form of use is not limited.

Next, a basic method of using the heat history display label 40 will be described. Heat history display label 4 of the present invention
0 is the adhesive layer 4 applied to the back surface of the heat-resistant resin film 42
Via 1 is proposed the use of bonding to any heated object surface. If the test object is exposed to heat for some reason, the heat history display label 40 that has been adhered has a heat history almost equivalent to that of the test object due to rapid heat conduction from the test object or direct heating from a heat source. At the same time, the thermal history marking agent printed on the surface of the heat resistant resin film 42 undergoes thermal denaturation corresponding to the thermal history.

The heat history is detected by uniformly irradiating the surface of the heat history display label 40 cooled to room temperature with excitation light in the wavelength range in which the heat history label emits fluorescence, so that the information display pattern 43 emits fluorescent light. Is emitted and passes this light of an arbitrary wavelength range.Preferably, only the fluorescence component is extracted using a wavelength selection filter such as an interference filter that does not contain excitation light and selectively obtains only fluorescence, Converts the amount of light or light in an arbitrary wavelength range into an electrical signal,
The heat history is detected by associating the obtained value with the heat exposure amount.

[0045]

EXAMPLES The thermal history determination method and the thermal history display label of the present invention will be described in more detail below by way of examples, using the thermal history inspection method of mounting electronic components on a printed wiring board as an example. I do. The scope of the present invention is not limited to these examples.

Example 1 (Heat History Judgment Method) (1) Preparation of Heated Sample for Heat History Judgment Anthracene (1% by weight) as a fluorescent substance for heat history judgment, and a cresol novolac type as a heat-resistant support material A mixture of a resin composition composed of an epoxy resin (82.5% by weight) and a phenol novolak type phenol resin (16.5% by weight) as a curing agent was prepared, and used as a thermal history determination probe. The resin composition comprising the compound is prepared by adding anthracene crystal powder to an epoxy resin, kneading the mixture for 30 minutes in an automatic mortar, and confirming that the anthracene crystal powder is sufficiently pulverized and uniformly dispersed. Is added and kneaded, and a vacuum degassing process is performed for about 5 minutes, and this is uniformly applied to the surface of a 3 cm square IC chip, which is an electronic component, and cured at room temperature for about 1 week to obtain a sample to be heated. Was.

(2) Determination of heat history The heat treatment of the IC chip was carried out by inserting the IC chip into an IR reflow heating device [Nihon Handa Co., Ltd. type 215] with the IC chip fixed. As a heating method, two types of continuous heating and repeated heating were used.

In the continuous heating method, the heating temperature is set to 175, 200, 225 and 2 as the temperature range in which the solder melts.
Set to 50 ° C, 1, 2, 3,
The printed wiring board on which the IC chip was mounted was continuously heated for 5, 8, and 10 minutes, and immediately after the predetermined time had elapsed, was taken out, allowed to stand at room temperature, and air-cooled.

In the repetitive heating method, the heating temperature is set to 175, 200, 225 and 250 ° C. as in the continuous heating method.
After heating for 1 minute in each temperature zone, taking out, returning to room temperature, and heating again,
This was repeated 3, 5, 8, and 10 times, and the total heating time was the same as in the continuous heating method.

The fluorescence spectrum was determined using a Xe-Hg lamp manufactured by Ushio Electric Co., Ltd. as an irradiation light source.
An irradiation light source having a center wavelength of 365 nm and a half width of about 10 nm was obtained using a bandpass filter. This light was sent 10 m from the direction perpendicular to the IC chip surface using an optical fiber.
An area of mφ is radiated, and the fluorescence obtained at this time is picked up from an angle of 45 ° with respect to the IC chip surface using an optical fiber, and this fluorescence light is used as a spectral fluorescence detector IMUC manufactured by Otsuka Electric Co., Ltd. It measured using -7000. Irradiation light intensity is
A part of the light after passing through the band-pass filter was taken out using a branched optical fiber, and monitored by a photomultiplier tube (manufactured by Hamamatsu Photonics).

FIG. 5 is a graph showing the results of determination of a fluorescence spectrum obtained from an anthracene-containing epoxy resin mixture applied to the surface of an IC chip after a continuous heat treatment at a heating temperature of 250 ° C. Anthracene undergoes a change in relative fluorescence intensity corresponding to the difference in the amount of heating, but its spectrum shape is maintained, so it is possible to indirectly estimate the thermal history by determining the fluorescence intensity at any wavelength. Becomes

[0052]

[Table 1]

Table 1 shows the relationship between the relative fluorescence intensity of anthracene at 410 nm and the heating temperature and heating time. As is clear from Table 1, the fluorescence intensity obtained at any wavelength after the heat treatment has a relationship corresponding to the heat history, that is, the heat exposure (integration of the heating temperature and the heating duration),
By determining the fluorescence intensity, the applied heat exposure can be quantitatively estimated. The difference in the rate of change of the fluorescence intensity due to the difference in the heating method in Table 1 is that, in the repetitive heating method, the process of repeating heating and cooling in units of one minute is repeated, so that the printed circuit board and the IC chip reach the set temperature. This is due to the loss of heat exposure until the heat exposure is reached. According to the heat history determination method of the present invention, such a slight difference in heat exposure can be detected.

Embodiment 2 (Heat History Display Label) FIG. 6 is a schematic side view of a heat history display label according to Embodiment 2 of the present invention.
FIG. 7 is a schematic top view of a thermal history display label according to Embodiment 2 of the present invention, and FIG. 8 is a schematic configuration diagram of an excitation light irradiation and detection system for measuring fluorescence from the thermal history display label. In the figure, reference numeral 60 denotes a heat history display label, 61 denotes an adhesive layer, 62 denotes a heat-resistant resin film, 63 denotes an information display pattern, 6
4 is a release paper, 65 is a silicone resin, 66 is a heat history labeling agent, 80 is a heat history display label, 81 is a Xe-Hg light source,
82 is a bandpass filter, 83 is excitation light, 84 is fluorescence, 85 is a wavelength selection filter, 86 is an optical fiber, 87
Is a spectroscope, and 88 is a computer.

Embodiment 2 will be described with reference to FIGS. Silicone resin (trade name: X-40-3004)
H, manufactured by Shin-Etsu Chemical Co., Ltd.)
After adding 0.5 parts by weight of T-PL-50T (manufactured by Shin-Etsu Chemical Co., Ltd.) and performing uniform kneading and vacuum deaeration, a polyimide resin-based heat-resistant resin film 62 (trade name: Kapton 25 μm, Coating on one surface of Toray Dupont Co., Ltd.) and drying by heating at 120 ° C. for 3 minutes.
1 was formed, and a release paper 64 was bonded thereon. Next, a silicone resin 65 (trade name: KE-1300T,
Shin-Etsu Chemical Co., Ltd.) and a crosslinking agent (trade name: CAT-13)
00T, Shin-Etsu Chemical Co., Ltd.) in a weight ratio of 10: 1 at room temperature, and then 30 parts by weight of anthrone (special grade of reagent, Wako Pure Chemical Industries, Ltd.) as a thermal history marker 66 were uniformly dispersed and mixed. Then, a vacuum degassing process was performed to produce an information display ink. Using a metal mask having a thickness of 300 μm, a 10 mm × 5 mm information display pattern 6
Screen printing as 3, cured at room temperature all day and night,
A heat history display label 60 of 20 mm × 30 mm square was obtained.

This heat history display label 60 is printed with paste solder and adhered to an electronic component by 10 cm × 15.
Affixed to the surface of a printed circuit board of cm square, this is a far-infrared reflow heater (Nihon Solder, 215 type)
, And heat treatment was performed for 0, 2, 4, 6, 8, 10 minutes at each heating temperature of 150, 180, 210, 240, and 270 ° C. After cooling each heat history display label subjected to these heat treatments to room temperature, X is applied to the surface of the heat history display label.
e-Hg lamp light source 81 (trade name: UXM-300Y)
A, Ushio Inc.)
Using (Yamashita Denso), the substrate surface is irradiated with excitation light 83 having a center wavelength of 365 nm perpendicularly, and a fluorescent light 84 generated at that time is subjected to a wavelength selection filter 85 for cutting off the reflection of the excitation light and stray light. 4 for printed wiring board
Spectroscope 87 using optical fiber 86 from an angle of 5 degrees
(Ocean Optics Inc. PS1000)
And the data of the spectral spectrum is transferred to a computer 88 (Digital Hinote Ultra C).
T475), and the fluorescence intensity at a wavelength of 423 nm was measured. Table 2 shows an example of the relationship between the fluorescence intensity and the heat treatment conditions obtained from the heat history display label 60 after the heat treatment.

[0057]

[Table 2]

As is clear from Table 2, the relative intensity of the fluorescence at 432 nm obtained by irradiating the excitation light to the heat history display pattern after the heat treatment performed at different heating temperatures and treatment continuation times was determined by heating. It can be seen that the higher the temperature and the longer the heating time, the greater the increase. The change in the fluorescence intensity corresponds to the product of the added heating temperature and the heating time, that is, the heat history.
Therefore, the thermal history can be quantitatively evaluated by grasping the relationship between the energy intensity of the excitation light irradiated when measuring the fluorescence and the fluorescence intensity at an arbitrary wavelength obtained at that time.

Embodiment 3 (Heat History Display Label) Embodiment 3 will be described in detail with reference to FIG. FIG. 9 is a schematic side view of a heat history display label according to Embodiment 3 of the present invention. In the figure, reference numeral 90 denotes a heat history display label, 91 denotes an adhesive layer, 92 denotes a heat-resistant resin film, and 93 denotes heat history display. pattern,
94 is a release paper, 65 is a silicone resin, 96 is a thermal history labeling agent, 97 is a fluorescent standard pattern, and 98 is a fluorescent standard substance.

A silicone resin-based pressure-sensitive adhesive layer 91 was formed on the back surface of the heat-resistant resin film 92 using the same procedures and materials as in Example 2, and then anthrone was dispersed as a thermal history marker 96. A silicone resin 95 is screen printed and a thermal history display pattern 9 of 10 mm × 5 mm square is formed.
6, anthracene carboxylic acid (manufactured by Wako Pure Chemical Industries, special grade reagent) as a fluorescent standard substance 98, a silicone resin 95 (brand name: KE-1300T, manufactured by Shin-Etsu Chemical Co., Ltd.) and a crosslinking agent (brand name: CAT -1300, manufactured by Shin-Etsu Chemical Co., Ltd.) was kneaded in the same manner as in Example 2, and then subjected to a vacuum deaeration treatment to uniformly disperse 30 parts by weight of the fluorescent standard agent. , Thickness 3
Using a 00 μm metal mask, screen printing is performed on the surface of the heat-resistant resin film 92 and cured at room temperature for 24 hours to produce a fluorescent standard pattern 97, and a thermal history having a thermal history display pattern 93 and a fluorescent standard pattern 97 simultaneously. The display label 90 was produced.

A heat history display label 90 was attached to a printed wiring board in the same procedure as in Example 2, heated, and then cooled to room temperature.
m of excitation light, and the fluorescence intensity (Fs) of anthracene carboxylic acid as a fluorescent standard substance at a fluorescence center wavelength of 465 nm, and the fluorescence center wavelength of anthrole generated by thermal denaturation of anthrone as a thermal history labeling agent About 423n
The fluorescence intensity (Ft) at m was measured by the same detection method as in Example 2, and Ft / Fs, which was the ratio of the two fluorescence intensities, was determined. Obtained from the heat history display label 90 after the heat treatment,
Table 3 shows an example of the relationship between the fluorescence intensity ratio (Ft / Fs) and the heat treatment conditions.

[0062]

[Table 3]

As shown in Table 3, the ratio of the relative intensity of the fluorescent light obtained from the fluorescent standard pattern at an arbitrary wavelength to the relative intensity of the fluorescent light obtained from the heat history display pattern at the arbitrary wavelength is also similar to that of Example 2. A value corresponding to the processing condition is obtained, and it can be seen that it can be used for quantitative evaluation of the heat history. In this case, since the ratio of the relative intensity of the fluorescence between arbitrary wavelengths is constant regardless of the excitation light energy, the management of the excitation light intensity required in Example 2 and the relationship between the excitation high intensity and the fluorescence intensity are required. It is not necessary to grasp the heat history, and a more simple quantitative measurement of the heat history becomes possible.

Example 4 (Heat History Display Label) FIG.
Example 4 will be described with reference to FIG. FIG. 10 is a schematic top view of a heat history display label according to Example 4 of the present invention. In the figure, reference numeral 100 denotes a heat history display label, 102 denotes a heat resistant resin film, 103 denotes a heat history display pattern, and 107 denotes a fluorescent standard. A pattern 109 is a supplementary information pattern.

In this embodiment, in addition to the heat history display pattern 103 made of the heat history labeling agent and the fluorescent standard pattern 107 made of the fluorescent labeling agent described in the third embodiment, the manufacturing date and serial number The heat history display label 100 also has a supplementary information pattern 109 indicating information such as the heat history. The supplementary information pattern 109 is obtained by incorporating information other than the heat history into the heat history display label in advance, and is made of a thermally stable ink or a thermally stable fluorescent substance, and does not change itself by heating. Printed in material. Although there is no particular limitation on the display form, for example, the bar code shown in FIG. 10 is proposed. The detection of the heat history information is performed in the same procedure as in the second and third embodiments, and an existing barcode reader or the like can be used for the supplementary information.

[0066]

As described above, according to the thermal history determination method of the present invention, the amount of change in the fluorescence intensity or the wavelength of the fluorescence accompanying the thermal denaturation of the chemical substance attached to the object to be heated is determined in advance under a predetermined condition. By comparing with the measured data of the relationship between the change in the fluorescence intensity or the wavelength of the fluorescence and the heat history obtained by the measurement, the heat history can be easily and quantitatively determined.

In addition, by using a chemical substance whose fluorescence characteristics change during the heat treatment for the detection of the heat history, the added heat history can be quantitatively detected by using the luminescence light having a large amount of information. Since it becomes possible, by using a heat history display label printed with a heat history indicator as an information display pattern on the surface of the heat-resistant resin film having an adhesive layer,
There is an effect that a simple heat history inspection can be performed at an arbitrary place.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the relationship between relative fluorescence intensity and heat exposure. (A) is a schematic graph of the fluorescence spectrum of the chemical substance after performing the heat treatment while changing the thermal exposure stepwise. (B) is a schematic graph showing the relationship between the relative fluorescence intensity and the heat exposure Q at an arbitrary wavelength λ ₀ after the heat treatment performed in (a).

FIG. 2 is an explanatory diagram of a relationship between a central fluorescence wavelength and a thermal exposure. (A) shows that the central wavelength is λ due to thermal denaturation accompanying heating.
It is a typical graph of the fluorescence spectrum before and after adding a different thermal history to the fluorescent substance which changes from ₀ to (lambda) ₃ in steps. (B) is a schematic graph showing the relationship between the center wavelengths λ ₁ , λ ₂ , and λ ₃ of each fluorescence spectrum obtained after the heat treatment performed in (a) and the heat exposure Q.

FIG. 3 is an explanatory diagram of the relationship between the fluorescence intensity and the fluorescence wavelength and the thermal exposure. (A) is obtained after a heat treatment of these fluorescent substances, using a combination of two types of fluorescent substances a and b each having a center wavelength of fluorescence at wavelengths λ _a and λ _b and having different thermal stability. It is a schematic graph of a synthetic fluorescence spectrum. (B) is a schematic graph showing the relationship between the relative fluorescence intensity and the heat exposure Q at an arbitrary wavelength λ after the heat treatment performed in (a).

FIG. 4 is a schematic perspective view of a heat history display label according to the embodiment of the present invention.

FIG. 5 is a graph showing a determination result of a fluorescence spectrum obtained from an anthracene-containing epoxy resin mixture applied to the surface of an IC chip after a continuous heat treatment at a heating temperature of 250 ° C.

FIG. 6 is a schematic side view of a heat history display label according to a second embodiment of the present invention.

FIG. 7 is a schematic top view of a heat history display label according to Embodiment 2 of the present invention.

FIG. 8 shows a diagram for measuring fluorescence from a thermal history label.
It is a schematic block diagram of an excitation light irradiation and detection system.

FIG. 9 is a schematic side view of a heat history display label according to Embodiment 3 of the present invention.

FIG. 10 is a schematic top view of a heat history display label according to Example 4 of the present invention.

[Explanation of symbols]

 40, 60, 80, 90, 100 Thermal history display label 41, 61, 91 Adhesive layer 42, 62, 92, 102 Heat resistant resin film 43, 63 Information display pattern 44, 64, 94 Release paper 65, 95 Silicone resin 66, 96 Heat history labeling agent 81 Xe-Hg light source 82 Band pass filter 83 Excitation light 84 Fluorescence 85 Wavelength selection filter 86 Optical fiber 87 Spectroscope 88 Computer 93, 103 Heat history display pattern 97, 107 Fluorescence standard pattern 98 Fluorescence standard substance 109 Supplementary information pattern λ wavelength I relative fluorescence intensity Q heat exposure τ time

Claims (10)

[Claims] 1. A method for judging the thermal history of an object to be heated placed in a heating environment, the method comprising: changing a fluorescence characteristic of the fluorescent substance placed in the heating environment together with the object to be heated due to thermal denaturation. Is measured qualitatively and quantitatively, based on the relationship between the amount of change in the fluorescent property and the heat history measured in advance for the fluorescent substance, the heat history of the object to be heated from the change in the measured fluorescent property. A method for determining a heat history, comprising: determining. 2. The thermal history determination method according to claim 1, wherein the change in the fluorescent characteristic due to the thermal denaturation of the fluorescent substance is a change in the fluorescence intensity due to the thermal denaturation of the fluorescent substance. 3. The thermal history determination method according to claim 1, wherein the change in the fluorescence characteristic due to the thermal denaturation of the fluorescent substance is a change in the fluorescence wavelength due to the thermal denaturation of the fluorescent substance. 4. A method for measuring a change in fluorescence characteristics caused by thermal denaturation of the fluorescent substance, wherein the fluorescent substance is a plurality of fluorescent substances used simultaneously and having different fluorescence spectra, and the change in fluorescent properties caused by thermal denaturation is performed. The thermal history determination method according to claim 1, wherein is a change in a combined fluorescence intensity and a fluorescence wavelength of each fluorescence spectrum after thermal denaturation of the plurality of fluorescent substances. 5. A thermal history display label, wherein a chemical substance that changes its fluorescent property due to thermal denaturation in a heating environment is used as a thermal history labeling agent to determine the thermal history. 6. The thermal history display label according to claim 5, wherein the thermal history indicator is formed as an information display pattern on a label. 7. The thermal history display label according to claim 5, wherein the change in the fluorescence characteristic of the chemical substance is at least one of a change in a fluorescence intensity and a change in a fluorescence wavelength. 8. The thermal history display label according to claim 6, further comprising an information display pattern printed with a thermally stable non-fluorescent ink. 9. The thermal history display label according to claim 6, which further has an information display pattern using a thermally stable fluorescent substance. 10. The heat history display label according to claim 5, which has an adhesive layer.