JP4992787B2 - Printed wiring board and inspection method thereof - Google Patents

Description

  The present invention relates to a printed wiring board and an inspection method thereof, and more particularly, to a printed wiring board and an inspection method thereof that can identify an insulation failure portion and an insulation defect portion between wirings.

  With the development of technology in recent years, miniaturization of devices found in portable electronic devices has progressed. In order to reduce the size of the device, the semiconductor device and the printed wiring board have been reduced in size and increased in density. Particularly, in the printed wiring board, a narrow wiring width and a wiring gap have been required for increasing the density. Furthermore, since various use environments are assumed for portable electronic devices that are carried and used, severe conditions are required for the insulation reliability of the printed wiring board. On the other hand, in the case of stationary devices, due to the effects of cost reduction and higher functionality, printed wiring must be routed with a narrow wiring width and wiring gap in order to mount a multi-pin BGA on an inexpensive through board with a small number of layers. It has been demanded and is a severe condition for insulation reliability.

  However, if there is an insulation failure in the circuit formed on the printed wiring board, the location of the insulation failure is identified by the amount of metal that can be visually observed due to the failure of insulation and the substrate surface being burned out or by the progress of electrochemical migration. This is difficult unless it is a defective part that has progressed remarkably, such as occurrence of a phenomenon such as precipitation.

  For maintenance management for maintaining the insulation of the circuit as described above, for example, Patent Document 1 proposes a structure in which a thermochromic material is coated on the outermost periphery of an electric cable with respect to the electric cable assembly. In this structure, when an abnormality occurs in the insulator and the temperature rises, the thermochromic material is discolored, and the location where the abnormality has occurred can be observed with the naked eye.

Moreover, in patent document 2, an electrochromic element sheet | seat is inserted between a printed wiring board and a base, a continuity test is performed, and the conduction | electrical_connection defect location of the component circuit of a printed wiring board is detected from the discoloration location of an electrochromic element sheet | seat. It has been proposed.
Japanese National Patent Publication No. 10-509550 (FIG. 1) Japanese Patent Laid-Open No. 61-221680 (FIG. 1)

  However, when the structure proposed in Patent Document 1 is directly applied to a printed wiring board, there are some problems. For example, since a thermochromic material layer displaying a fault defect is formed on the insulating material covering the conductor wiring of the printed wiring board, even if insulation failure occurs in the insulating material near the conductor wiring, Since the influence is mitigated by the insulating material on it, the thermochromic material on it further hardly reacts. In addition, thermochromic materials that display fault defects are arranged on the outermost periphery, and thermochromic materials that display fault defects can appear due to the influence of the environment during assembly or the influence of external factors. There is a problem that it is impossible to distinguish between deterioration due to heat generation inside the electric cable and deterioration due to external factors.

  The structure proposed in Patent Document 2 is considered to be suitable for detecting a conduction failure due to a circuit defect, but it is difficult to detect a slight defect in the insulating layer for eliminating a possible insulation failure in the future. .

  It is an object of the present invention to provide a special observation of an insulation defect location or an insulation defect location in a printed wiring board in which insulation failure has occurred or a printed wiring board having slight insulation defects that will cause insulation failure in the future. An object of the present invention is to provide a printed wiring board that can be easily identified by visual inspection without using an auxiliary device, and an inspection method thereof.

  A printed wiring board according to a first aspect of the present invention for solving the above problems is a printed wiring board in which a conductor wiring and an insulating layer are formed on a base material, wherein the insulating layer contains an electrochromic material. It is characterized by being.

  In a preferred aspect of the present invention, the electrochromic material is configured to be encapsulated in microcapsules, the electrochromic material is configured to be encapsulated in microcapsules, or the printed wiring board The electrochromic material is configured to exist around and in the insulating layer.

  Further, the printed wiring board according to the second aspect of the present invention is a printed wiring board in which a conductor wiring and an insulating layer are formed on a base material. It is characterized by the presence of chromic material.

  As a preferable aspect of the printed wiring board of the present invention according to the first and second aspects, (1) the insulating layer is a solder resist, and (2) the electrochromic material is a spirooxazine radical derivative. (3) The printed wiring board is configured to be a flexible substrate, a rigid substrate, or a rigid flexible substrate before or after mounting the electronic component.

  In order to solve the above-mentioned problem, a printed wiring board inspection method according to a first aspect of the present invention is a printed wiring board in which a conductor wiring and an insulating layer are formed, and an electrochromic material is included in the insulating layer. A step of preparing a wiring board; and a step of inspecting a change in color of the insulating layer by applying a voltage to the conductor wiring.

  Further, the printed wiring board inspection method according to the second aspect of the present invention is a printed wiring board in which a conductor wiring and an insulating layer are formed on a substrate, and the periphery of the printed wiring board and in the insulating layer. And a step of preparing a printed wiring board in which an electrochromic material is present, and a step of inspecting a change in color of the insulating layer by applying a voltage to the conductor wiring.

  According to the printed wiring board according to the first and second aspects of the present invention, the insulating layer covering the conductor wiring is configured to contain an electrochromic material, and the electrochromic material is disposed around the printed wiring board and the insulating layer. When there is a part where the insulation has deteriorated in the insulating layer between the conductor wiring, or when there is a minute defect that may cause insulation deterioration, when voltage is applied between the conductors, The electrochromic material at that location is discolored, and a defective portion or a defective progress portion can be directly confirmed.

  According to the printed wiring board inspection method according to the first and second aspects of the present invention, a step of preparing the printed wiring board according to the present invention, and applying a voltage to the conductor wiring, the color of the insulating layer And there is a step of inspecting the change, so that there is a place where the insulation is deteriorated in the insulating layer between the conductor wirings constituting the printed wiring board, or there is a minute defect where there is a possibility of insulation deterioration, The electrochromic material at that location is discolored, and a defective portion or a defective progress portion can be directly confirmed. As a result, it is possible to easily identify visually a printed wiring board that is free from insulation defects and has no fine defects that may cause insulation deterioration without using a special observation auxiliary device.

  Next, embodiments of a printed wiring board, a manufacturing method thereof, and an inspection method thereof according to the present invention will be described in detail with reference to the drawings.

[Printed wiring board]
FIG. 1 is an explanatory view showing a printed wiring board according to a first embodiment of the present invention, (A) is a perspective view, and (B) is an enlarged sectional view of “S1”. The printed wiring board 1 is formed by forming conductor wirings 11 and 12 and an insulating layer 13 on a base material 10, and the insulating layer 13 contains an electrochromic material.

  As the base material 1 and the conductor wirings 11 and 12 provided on the base material 1, those conventionally used as a constituent material of the printed wiring board can be applied and are not particularly limited. For example, the base material may be a rigid substrate made of FR4 material, FR5 material, BT resin material, Teflon (registered trademark) material, or a composite rigid substrate obtained by combining them, or a copper pattern on a polyimide film. May be a single-sided flexible substrate, a double-sided flexible substrate, a multilayer flexible substrate, or a flex-rigid substrate combining them. In general, a copper pattern is formed as the conductor wirings 11 and 12, but the printed wiring board of the present invention is more preferable than the conductor wirings 11 and 12 formed in correspondence with the recent narrow pitch. .

  The insulating layer 13 is provided so as to cover the conductor wirings 11 and 12 on the substrate 1. The insulating layer 13 may cover the entire surface thereof, or may cover an arbitrary region, and is usually preferably provided as one that functions as a solder resist. The insulating layer 13 includes an electrochromic material. The electrochromic material is usually encapsulated in microcapsules, and the microcapsules are uniformly dispersed in the insulating layer 13. The electrochromic material is a material that is colored or disappears by a reversible oxidation-reduction reaction that is electrically induced.

  The reason why the electrochromic material is encapsulated in the microcapsule is that the electrochromic material needs to be mixed with the resin material for forming the insulating layer, and the electrochromic material is stably present in the resin material. Further, by encapsulating with a microcapsule, it is possible to prevent the electrochromic material from isomerizing and coloring due to the influence of other external environment such as ultraviolet light. As the electrochromic material, various materials can be exemplified. In consideration of encapsulating the electrochromic material in the microcapsule as in the first embodiment, an inorganic electrochromic material such as tungsten oxide is suitable. .

  A microcapsule can encapsulate an electrochromic material, and further needs to be bonded and stable with an epoxy material that is an insulating layer forming material that functions as a solder resist, for example. Therefore, MMA (methyl methacrylate) or polylactic acid is used. It can be preferably used. Furthermore, it is more desirable if it is a material having a light shielding property against UV light. Such microcapsules can be produced by a conventionally known general method such as formation and growth on a core material by a polymerization reaction.

  The microcapsules encapsulating the electrochromic material are mixed in a liquid resin material for forming an insulating layer and uniformly dispersed in the insulating layer 13 formed by a general insulating layer forming process.

  FIGS. 2A and 2B are explanatory views showing an aspect in which the insulation degradation portion of the formed insulating layer develops color, FIG. 2A is a cross-sectional view showing the color development aspect of the insulating layer, and FIG. 2B is an enlarged cross section of “S2”. FIG. In FIG. 2, the insulating layer 13 that protects and insulates the conductor wirings 11 and 12 is deteriorated, and the microcapsules 22 contained in the insulating layer 13 and the state of the minute cracks 17 are shown.

  As shown in FIG. 2B, a crack 17 is generated from the edge of the wiring 12, the crack 17 propagates and grows in the insulating layer 13, and the crack 17 communicates with another wiring 11. When the influence of moisture absorption or the like by the external environment is applied, an insulation failure occurs with impurity ions in the insulating layer 13 in a voltage application environment, and minute electricity flows. When electrical conduction due to insulation failure occurs between the conductor wirings 11 and 12, the microcapsules (including the electrochromic material) 16 at the location where the electrical conduction has occurred are colored by electroisomerization of the electrochromic material, and the colored portion 14 can be specified. Since the isomerized electrochromic material is stable in a colored state unless the isomerization is restored by reversing the electric potential by applying a reverse potential, the colored state is maintained even after the voltage application is stopped. The defective part indicated by can be directly identified. Note that reference numeral 15 in FIG. 2B denotes a non-colored microcapsule at a part not related to the crack 17.

  3A and 3B are explanatory views showing a manufacturing process of the printed wiring board according to the second embodiment of the present invention, in which FIG. 3A is a perspective view of the process, and FIG. 3B is “S3” of the obtained printed wiring board. FIG. The printed wiring board 2 is formed by forming conductor wirings 11 and 12 and an insulating layer 18 on a substrate 10, and an electrochromic material exists around the printed wiring board 2 and in the insulating layer 18. It makes the aspect which does. In addition, since the thing similar to what was demonstrated in the said 1st Embodiment can be used for the board | substrate 10, an insulating layer formation material, and an electrochromic material, description is abbreviate | omitted here.

  As shown in FIG. 3A, the printed wiring board 2 of the second embodiment has an insulating layer 18 on the base material 10 on which the conductor wirings 11 and 12 are formed so as to cover the conductor wirings 11 and 12. The printed wiring board 2 on which the electronic components 23 and 24 are mounted is prepared, and the printed wiring board 2 is immersed in an organic solvent containing an electrochromic material. An electrochromic material is present around the printed wiring board 2 thus obtained, and an electrochromic material is also present in the insulating layer 18.

  As the electrochromic material, the same materials as those described in the first embodiment can be used, but still other electrochromic materials having the property of being dissolved in an organic solvent may be used. As the organic solvent, an organic solvent that does not affect the already mounted electronic components 23 and 24, such as toluene and xylene, can be preferably used. The blending amount of the electrochromic material in the organic solvent is not particularly limited, but may be, for example, about 0.2 mmol / L with respect to the organic solvent.

  The electrochromic material is immersed in the insulating layer 18 on the surface layer of the printed wiring board 2 by immersing the printed wiring board 2 after completion of manufacturing including component mounting in a mixed solution in which an electrochromic material is mixed in an organic solvent. The electrochromic material can be adsorbed on the surface layer of the printed wiring board 2. The electrochromic material can be allowed to exist in the insulating layer 18 constituting the printed wiring board by drying the printed wiring board after permeating or adsorbing the electrochromic material at room temperature and under reduced pressure.

  Such a method is particularly preferable because it can avoid the possibility that the electrochromic material is isomerized or decomposed (destroyed) by a process such as heat or UV irradiation treatment during the manufacturing process of the printed wiring board. And since the printed wiring board 2 produced in the second embodiment can be directly dispersed in the insulating layer 18 without encapsulating the electrochromic material in the microcapsule, it is at an earlier stage than when encapsulated in the microcapsule. Defects can be detected.

  FIGS. 4A and 4B are explanatory views showing an aspect in which the insulation degradation portion of the formed insulating layer develops color, FIG. 4A is a cross-sectional view showing the color development aspect of the insulating layer, and FIG. 4B is an enlarged cross section of “S4”. FIG. In FIG. 4, the insulating layer 18 that protects and insulates the conductor wirings 11 and 12 is deteriorated, and a minute crack 22 generated in the insulating layer 18 and a colored portion in the vicinity of the crack are shown.

  As shown in FIG. 4B, a crack 22 is generated from the edge of the wiring 12, the crack 22 propagates and grows in the insulating layer 18, and the crack 22 communicates with another wiring 11. When the influence of moisture absorption or the like by the external environment is applied, an insulation failure occurs with impurity ions in the insulating layer 18 under a voltage application environment, and minute electricity flows. When electrical conduction due to poor insulation occurs between the conductor wirings 11 and 12, the electrochromic material existing around the electrically conductive crack is isomerized and colored to identify the colored portion 21 (see FIG. 4A). Therefore, the colored state is maintained even after the voltage application is stopped, and the defective portion indicated by the colored portion 21 can be directly specified.

  As described above, according to the printed wiring board 1 according to the first embodiment of the present invention, the insulating layer 13 covering the conductor wirings 11 and 12 is configured to include the electrochromic material, and the second embodiment. According to the printed wiring board 2 of the present invention, since the electrochromic material is configured to exist around the printed wiring board and in the insulating layer 18, it is insulated from the insulating layer between the conductor wirings when a voltage is applied between the conductors. When there is a deteriorated part or there is a fine defect part that may cause insulation deterioration, the electrochromic material at that part is discolored, and the defective part and the defective progress part can be directly confirmed.

[Example of electrochromic material]
Next, an example of an electrochromic material that can be preferably used for the printed wiring board of the present invention will be described in detail. The following chemical formula is a general formula of a spirooxazine radical derivative that can be used as an electrochromic material.

In the chemical formula, X ¹ is a chalcogen element (oxygen, sulfur, selenium, tellurium, etc.), an alkylidene group (ethylidene, propylidene, isopropylidene, butylidene, etc.), or a cycloalkylidene group composed of a cyclic structure thereof. X ² is a chalcogen element (oxygen, sulfur, selenium, tellurium, etc.). R ^{1 to} R ¹¹ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms (methyl, ethyl, propyl, butyl), an alkoxy group (methoxy, ethoxy, propoxy, butoxy, etc.), an aryl group (phenyl, Tolyl, xylyl, biphenyl, etc.), a halogenated alkyl group, a cyano group, an amino group, a nitro group, or a halogen atom. In addition, R ^{1 to} R ¹¹ in adjacent carbon atoms may be bonded to each other to form an aromatic ring or a heterocyclic ring that may have a substituent. In the chemical formula, n is 0 or 1.

  Such spirooxazine radical derivatives have both a stable radical group contributing to electron transfer and a spirooxazine compound exhibiting chromic characteristics for identification.

  Here, a spirooxazine compound constituting a spirooxazine radical derivative is compared with a spiropyran compound known as a chromic compound. The spiropyran compound has a carbon-carbon double bond part (-C = C-) functioning as a chromophore in the pyran ring, and this bond site is a structure in which an autooxidation reaction due to singlet oxygen is likely to occur. It is said that the period for maintaining the durability of reversible isomerization is short. On the other hand, the spirooxazine compound constituting the spirooxazine radical derivative has a structure in which the pyran ring of the spiropyran compound is replaced with an oxazine ring, and is a carbon-nitrogen that is a chromophore on the oxazine ring in the same manner as the pyran ring of the spiropyran compound. When the double bond portion (-C = N-) is attacked by singlet oxygen, it is difficult to bond with singlet oxygen compared to carbon-carbon double bond (-C = C-). Is done. A spirooxazine radical derivative composed of such a spirooxazine compound is less susceptible to auto-oxidative degradation, thus improving the durability of isomerization.

  In order to use it preferably as an electrochromic material, it is necessary that the reversible reaction of radical groups is stable with respect to isomerization by electron transfer. In this spirooxazine radical derivative, a pyrrolidine ring, a piperidine ring, an oxazolidine ring, an oxazine ring, a thiazolidine ring, a thiazine ring, a selenazolidine ring, a selenazine ring, etc., forming a spiro ring with respect to the oxazine ring of the spirooxazine compound. Since it has a nitroxy radical site (> N—O.), Which is a stable radical species, the above requirement is sufficiently satisfied.

  This spirooxazine radical derivative is obtained by adding a hydroxyl radical to the nitrogen atom by a process such as dehydration after hydroxylamination of the nitrogen atom adjacent to the spirocarbon in the spirooxazine compound generally known as a chromic compound, Can be generated.

[Inspection method of printed wiring board]
The printed wiring board inspection method of the present invention is a method for inspecting the printed wiring boards 1 and 2 according to the first and second embodiments. The first inspection method is a method for inspecting the printed wiring board 1 according to the first embodiment. The conductor wirings 11 and 12 and the insulating layer 13 are formed on the base material 10. , 16 and a step of preparing a printed wiring board in which the electrochromic material enclosed in the insulating layer 13 is included, and a voltage is applied to the conductor wirings 11 and 12 to inspect the color change of the insulating layer 13. A method having a process. On the other hand, the second inspection method is a method for inspecting the printed wiring board 2 according to the second embodiment, and is a printed wiring board in which the conductor wirings 11 and 12 and the insulating layer 18 are formed on the substrate 10. The step of preparing the printed wiring board 2 in which the electrochromic material exists around the printed wiring board and in the insulating layer 18, and the voltage change is applied to the conductor wirings 11 and 12 to inspect the color change of the insulating layer 18. A method having a process.

  According to such an inspection method, the insulation layer (13, 18) between the conductor wirings 11 and 12 constituting the printed wiring boards 1 and 2 has a location where insulation has deteriorated, or a fine defect that may cause insulation deterioration. When a location exists, the electrochromic material at that location changes color, and a defective portion or a defective progress location can be directly confirmed. As a result, it is possible to easily identify visually a printed wiring board that is free from insulation defects and has no fine defects that may cause insulation deterioration without using a special observation auxiliary device.

  Next, the present invention will be described in more detail with reference to examples. In the following examples, a spirooxazine radical derivative having the above chemical formula is used as an example of an electrochromic material. In addition, the printed wiring board of this invention is not limited only when the following electrochromic materials are used.

In the spirooxazine radical derivative represented by the above chemical formula, a compound was synthesized in which X ¹ is isopropylidene, X ² is oxygen, R ¹ and R ² are methyl groups, R ^{3 to} R ⁹ are hydrogen atoms, and n is 0. .

  First, 2-methylene-3,3,5,5-tetramethylpyrrolidine 3 mmol (417 mg) and 2-nitrosophenol 3 mmol (369 mg) were dissolved in 40 ml of dehydrated methanol solvent, heated to reflux, and then the solvent was distilled off under reduced pressure. . The resulting residual reaction product was developed and separated on a silica gel column (developing solvent: ethyl acetate / normal hexane mixed solvent), and the solvent was removed from the resulting solution by distillation under reduced pressure. An excessive amount of hydrogen peroxide was dropped into 0.61 mmol (150 mg) of the purified compound in dehydrated ether to obtain a precursor compound. 0.50 mmol (130 mg) of this precursor compound was added to 30 ml of dehydrated ether, and 0.50 mmol (116 mg) of silver (I) oxide was added with ice cooling, followed by thorough stirring. Anhydrous sodium sulfate was added, suction filtration was performed, and the obtained filtrate was concentrated under reduced pressure to a half volume by a rotary evaporator. The residue was cooled at a low temperature (−78 ° C.) with a mixture of ethanol and dry ice to obtain a spirooxazine radical derivative having the aforementioned substituent.

In addition, generation | occurrence | production of the radical of the obtained spirooxazine radical derivative has been confirmed by electron spin resonance analysis (ESR). Further, the structure and the like were confirmed by ¹ H-NMR measurement results (solvent: CDC1 ₃ , standard: TMS), elemental analysis results, and the like.

Similarly, X ¹ is isopropylidene, X ² is oxygen, R ⁵ is a methyl group, R ⁸ is a nitro group, R ¹ , R ⁴ , R ⁶ , R ⁷ , R ⁹ are hydrogen atoms, and n is 0 Thus, a spirooxazine radical derivative in which R ² and R ³ are bonded to each other to form an aromatic 6-membered ring was also synthesized.

  The obtained derivative is used as an electrochromic material, microencapsulated with MMA (methyl methacrylate), the microcapsules are dispersed and mixed in an epoxy resin solution, and the resulting mixed solution is used as conductor wirings 11 and 12. The insulating layer 13 functioning as a solder resist was formed by coating on the surface of the formed printed wiring board 1 to produce the printed wiring board 1 according to the first embodiment.

  Further, using the same mixed solution, the printed wiring board 2 in which the insulating layer 18 is formed on the conductor wirings 11 and 12 and the electronic components 23 and 24 are mounted in the mixed solution 19. Immersion was performed to produce a printed wiring board 2 according to the second embodiment.

  Thus, the spirooxazine radical derivative can be used as an electrochromic material used in the printed wiring board of the first embodiment or the second embodiment. And the spirooxazine radical derivative has the advantage that stable electrochromic properties can be obtained over a long period of time, and if such a spirooxazine radical derivative is contained in the insulating layer constituting the printed wiring board according to the present invention, Insulation defects that cause or may cause insulation failure can be identified, and the occurrence of defects that gradually progress with time can be maintained and managed over a long period of time.

  According to the printed wiring board and the inspection method of the present invention, it is possible to easily identify a defective portion due to insulation deterioration of the printed wiring board, and it can be applied to maintenance and repair applications.

It is explanatory drawing which shows the printed wiring board which is 1st Embodiment of this invention, (A) is a perspective view, (B) is an expanded sectional view of "S1". It is explanatory drawing which shows the aspect which the insulation degradation part of an insulating layer colors, (A) is sectional drawing which shows the coloring aspect of an insulating layer, (B) is an expanded sectional view of "S2". It is explanatory drawing which shows the manufacturing process of the printed wiring board which is 2nd Embodiment of this invention, (A) is a perspective view of a process, (B) is an expanded cross section of "S3" of the obtained printed wiring board FIG. It is explanatory drawing which shows the aspect which the insulation degradation part of an insulating layer colors, (A) is sectional drawing which shows the coloring aspect of an insulating layer, (B) is an expanded sectional view of "S4".

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Printed wiring board 10 Base material 11,12 Conductor wiring 13 Insulating layer 14 Colored part 15 Microcapsule (non-colored)
16 microcapsules (color development)
17 Crack (defect)
18 Insulating layer 19 Solution in which electrochromic material is dissolved 20, 21 Colored portion 22 Crack (defect)
23, 24 Electronic components

Claims (6)

A substrate, and two or more conductive wiring provided on the substrate, an insulating layer provided so as to cover the conductor wire, in the composed formed printed wiring board, the insulating layer is the conductor A printed wiring board comprising an electrochromic material for specifying a portion where electrical conduction is made between wirings.   The printed wiring board according to claim 1, wherein the electrochromic material is encapsulated in microcapsules.   The printed wiring board according to claim 1, wherein the electrochromic material is present around the printed wiring board and in the insulating layer. It said insulating layer is a solder resist, printed circuit board according to any one of claims 1-3. The printed wiring board according to any one of claims 1 to 4 , wherein the electrochromic material is a spirooxazine radical derivative. The printed wiring board, before or after mounting the electronic component, a flexible substrate, a rigid substrate or a rigid flexible substrate, printed wiring board according to any one of claims 1-5.

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