Evaluation method for flux or resist substrate

Abstract

To solve the problem that if a line / space of a wiring pattern is narrow, migration is generated, but a relation between the line / space and the migration generation is not quantified.SOLUTION: A wiring board 102 is immersed in water 202, and thereby copper ions are eluted in the water 202 by a copper wiring pattern 104, and an ion component of flux is eluted. The eluted copper ions are adsorbed by an ion exchange resin 203. The ion exchange resin 203 adsorbing the copper ions is immersed in a regenerant 204, and makes the copper ions eluted in the regenerant 204. After the regenerant 204 has been neutralized by a neutralization liquid 205, reagent bathocuproine is dropped to develop a color. The colored regenerant measures absorbance (Abs) by a wavelength spectral device, and quantifies a copper ion amount. The ion component of the flux is quantified by a conductivity meter.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for predicting migration resistance, a method for evaluating migration, a method for evaluating the mounting of electronic components, a method for evaluating soldering, a method for predicting soldering, and the selection of flux / solder resist for printed circuit boards, electronic circuit boards, laminated boards, laminated films, film wiring boards, etc.

[0002] Furthermore, it relates to a method for determining the quality of a wiring board, and the evaluation device and prediction device therefor. It also relates to the design guidelines and evaluation of the line / space (L / S) of a wiring board. It relates to these evaluation devices and verification devices.

Background Art

[0003] In digital electronic devices such as mobile phones, smartphones, and personal computers, the trend towards higher functionality and multi-functionality has been accelerating in recent years. For higher functionality and multi-functionality, high-density mounting of semiconductor components and the like has been progressing, and thus the line / space of printed wiring boards on which semiconductor components are mounted has been continuously refined.

[0004] The line / space of a printed wiring board is an important matter for high-density mounting of electronic components and the like, but the performance and type of flux and resist also influence high-density mounting of electronic components and the like.

[0005] In printed wiring boards, research and development for excellent migration resistance and ensuring high insulation reliability is actively carried out. However, in order to evaluate migration resistance, it is necessary to conduct an insulation reliability test over a long period, which is a time obstacle in terms of the design and research and development efficiency of printed circuit boards.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] Patent Document 1 describes applying an AC voltage to a degraded printed circuit board in an accelerated degradation test environment to obtain a Cole-Cole plot, and predicting the migration resistance of the printed circuit board based on the presence of Warburg impedance (Fw) on the obtained Cole-Cole plot. [Overview of the project]

[0008] The present invention involves immersing a substrate 102 coated with flux 101, etc., in an aqueous solution containing water to extract metal ions such as copper that constitute the copper wiring (copper foil) pattern, as well as ionic components of the flux. The metal ions are adsorbed with an ion exchange resin, and then the ion exchange resin is placed in a regeneration solution to regenerate the ion exchange resin and extract the metal ions into the regeneration solution. The regeneration solution is neutralized and its absorbance is measured. The ionic components of the flux are measured by conductivity (rate) using a conductivity (rate) meter. [Problems that the invention aims to solve]

[0009] The method described in Patent Document 1 requires calculations to be performed based on the presence of Warburg impedance (Fw) on the Cole-Cole plot. Creating a Cole-Cole plot is time-consuming, and predicting migration using a Cole-Cole plot is indirect and often yields results that deviate from reality.

[0010] Migration occurs when the line / space ratio of the wiring pattern is too narrow. Although migration occurs, the relationship between line / space ratio and migration occurrence has not been quantified. Therefore, experiments and reliability tests are necessary to verify the line / space ratio and proceed with the design. This process requires a long time, thus necessitating a lengthy wiring design process for the circuit board. [Means for solving the problem]

[0011] In this invention, copper ions from the copper wiring pattern 104 dissolve into the water 202 by immersing the wiring board 102 in water 202. In addition, ionic components of the flux dissolve into the water 202. The dissolved copper ions are adsorbed by the ion exchange resin 203.

[0012] The ion exchange resin 203, which has adsorbed copper ions, is immersed in the regeneration solution 204 to allow the copper ions to dissolve into the regeneration solution 204. After neutralizing the regeneration solution 204 with the neutralizing solution 205, reagents such as bathocuproine 206 are added dropwise to induce color development. The absorbance (Abs) of the colored regeneration solution is measured using a wavelength spectrometer to quantify the amount of copper ions (copper ion concentration).

[0013] The ionic components (amount of ions, ion concentration) of the flux dissolved in water 202 change the conductivity of water 202. By measuring the conductivity of water 202 with a conductivity meter, the amount of ions (ion concentration) can be quantified.

[0014] The method for evaluating a wiring substrate according to the present invention is characterized by comprising: a first step of immersing a substrate on which metal wiring is formed in a first aqueous solution; a second step of adsorbing metal ions from the first aqueous solution after the first step onto an ion exchange resin; a third step of eluting metal ions from the ion exchange resin into a second aqueous solution; a fourth step of mixing a neutralizing solution to neutralize the second aqueous solution; a fifth step of mixing a reaction material that forms a complex with metal ions into the second aqueous solution; a sixth step of measuring the transmittance or absorbance of the second aqueous solution after the fifth step; and a seventh step of measuring the conductivity of the first aqueous solution.

[0015] Preferably, the reaction material is at least one of neocuproin and bathocuproin, and the ion exchange resin is preferably a strongly acidic cation exchange resin.

[0016] The wiring board evaluation apparatus of the present invention comprises a first means for eluting metal ions from a substrate on which metal wiring is formed into a first aqueous solution, a second means for adsorbing metal ions from the first aqueous solution onto an ion exchange resin, and a third means for eluting metal ions from the ion exchange resin into a second aqueous solution.

[0017] It is characterized by comprising a fourth means for mixing a reaction material that forms a complex with metal ions in a second aqueous solution, and a fifth means for measuring the transmittance or absorbance of the second aqueous solution.

Advantages of the Invention

[0018] The amount of metal ions can be quantified by causing color development according to the amount of metal ions and measuring the absorbance of the solution containing the component to be measured. In order to quantify the amount of ions eluted from a flux or the like, it becomes possible to efficiently, simply, and rapidly evaluate a wiring board.

Brief Description of the Drawings

[0019] [Figure 1] It is an explanatory diagram of a method for evaluating a wiring board of the present invention. [Figure 2] It is an explanatory diagram of a wiring board used for evaluating a wiring board of the present invention. [Figure 3] It is an explanatory diagram of a wiring board used for evaluating a wiring board of the present invention. [Figure 4] It is an explanatory diagram of a wiring board used for evaluating a wiring board of the present invention. [Figure 5] It is an explanatory diagram of an evaluation apparatus for a wiring board of the present invention. [Figure 6] It is a graph of absorbance (Abs: Absorbance) with respect to the spectral wavelength. [Figure 7] It is a graph of absorbance (Abs: Absorbance) with respect to the spectral wavelength. [Figure 8] It is a graph of absorbance (Abs: Absorbance) with respect to the spectral wavelength. [Figure 9] It is a graph of absorbance (Abs: Absorbance) with respect to the space of the wiring pattern. [Figure 10] It is a graph of absorbance (Abs: Absorbance) with respect to the space of the wiring pattern. [Figure 11] Structural formulas of neocuproine and bathocuproine that form a chelate with copper. [Figure 12] This graph shows the change in resistance value of a circuit board after it has been submerged in a water-based solution. [Figure 13] This is an explanatory diagram showing the change in the amount of ions in an aqueous solution when a wiring board is immersed in water. [Figure 14] This graph shows the change in conductivity of a water-soluble solution when a wiring board is immersed in it. [Modes for carrying out the invention]

[0020] Embodiments of the present invention will be described below with reference to the drawings. In each drawing illustrating embodiments for carrying out the invention, elements or components having the same or similar function will be denoted by the same reference numeral, and their descriptions may be omitted. Furthermore, the embodiments of the present invention described herein can be combined in part or in whole with each other. In addition, some parts of the drawings and other illustrations of the present invention have been omitted, enlarged, or reduced in order to facilitate explanation, understanding, or illustration.

[0021] The present invention can be used not only to evaluate the migration resistance of printed circuit boards and the like, but also to evaluate, adopt, apply, and verify flux residue, flux reliability, flux acid value, suitability of solder material, suitability of soldering conditions, suitability of solder paste, flex, solder paste supply amount, mounting of electronic components, reflow conditions, reflow method, cleaning, etc.

[0022] Furthermore, by quantifying the amount of ions eluted from the flux into the aqueous solution, it is possible to evaluate, adopt, apply, and verify flux residue, flux reliability, flux acid value, suitability of solder material, suitability of soldering conditions, suitability of solder paste, flex, solder paste supply amount, electronic component mounting, reflow conditions, reflow method, cleaning, etc.

[0023] Therefore, although flux 101 is described in the following examples and drawings, it goes without saying that flux 101 may be replaced with solder, solder paste, etc. Also, it goes without saying that flux 101 may be interpreted as solder, solder paste, etc. The wiring board evaluation method and wiring board evaluation apparatus of the present invention can also be applied to the evaluation, analysis, and processing of evaluation boards, and can quantify evaluation guidelines.

[0024] Flux residue is caused by flux vapor, heated flux, and unheated flux, and its effects can range from simple discoloration to complete destruction of the product's function. The problem of reduced insulation resistance due to flux residue is closely related to corrosion. Predicting failures and reductions in insulation resistance due to corrosion is difficult, and there is no generally accepted evaluation method.

[0025] The oxidizing activity of a flux is expressed by the number of milligrams of potassium hydroxide required to neutralize the free acid in 1 gram of flux solids. Even fluxes with the same acid value can vary considerably in activity and corrosiveness. Acid value is completely unrelated to the pH value. Prediction is difficult, and there is no generally accepted evaluation method.

[0026] Solder paste is a mixture of solder powder and high-viscosity flux (vehicle), and is widely used in surface mount applications. Solder paste typically contains 75-90% by weight of solder powder, and special auxiliary components are added to prevent separation of the solder powder and flux, and to impart viscosity and thixotropy.

[0027] Solder pastes using spherical powders with low oxidation are attracting attention for the purpose of high-density mounting and eliminating the need for cleaning after reflow soldering. Although oxidation of spherical powders can be prevented for long periods by carefully managing storage, prediction is difficult, and there is no method for evaluation.

[0028] In surface mount assembly, solder paste is primarily supplied using two methods: a printing method using a screen or metal mask, and a dispenser method that extrudes a fixed amount from a needle. However, the specific amount of solder paste to supply, regardless of whether it's the printing method or the dispenser method, is determined through assembly evaluation. Prediction is difficult and there are no other evaluation methods available.

[0029] Reflow soldering methods include infrared radiation heating, hot air circulation heating, vapor phase condensation heating (VPS), and inert gas atmosphere heating. Infrared radiation heating is inexpensive in terms of both equipment costs and running costs, and is highly productive, but it is unsuitable for mounting components with large differences in heat capacity or components that are not heat resistant.

[0030] While hot air circulation heating is suitable for mounting components with different heat capacities and components that are not heat-resistant, oxidation of the joints due to low-temperature, long-duration heating is a concern. The relationship between the reflow method and joint oxidation is unclear, making oxidation difficult to predict. Furthermore, there are no appropriate evaluation methods.

[0031] In Japan, soldering in consumer electronics is largely done without cleaning. However, with the recent spread of surface mount technology and increased density, even consumer electronics now undergo cleaning to accommodate automated inspection equipment.

[0032] Cleaning methods include immersion in a solvent and cleaning the residue using ultrasonic vibrations, cleaning with solvent vapor, and removing the solvent by high-pressure spraying. Regarding cleaning, it is difficult to predict the cleaning effect, and there is no method for evaluating it.

[0033] There are virtually no evaluation methods, prediction methods, or evaluation devices for the above-mentioned challenges. In reality, the process involves mounting electronic components, conducting reliability tests, etc., to identify the conditions for each challenge, and then making improvements.

[0034] To address the above-mentioned problems, the present invention can be used to quantify evaluation criteria and the degree of problems by implementing the evaluation method or applying the evaluation apparatus of the present invention and measuring absorbance based on color development, thereby contributing to the formulation of design guidelines and countermeasures.

[0035] In this invention, the embodiment is described as measuring absorbance (Abs), but it is not limited to this. For example, it goes without saying that transmittance may be measured. Alternatively, reflectance may be measured and evaluated. Furthermore, evaluations may be performed using a combination of these methods.

[0036] Furthermore, while the explanation assumes that the ion concentration (amount of ions) of an aqueous solution containing flux is measured using a conductivity meter, it is not limited to this method. For example, it goes without saying that the ion concentration (amount of ions) can also be quantified indirectly or directly using a multi-water quality checker, pH meter, water quality analyzer, etc.

[0037] Alternatively, the colored solution may be adsorbed or absorbed onto absorbent paper, and the spectral transmittance, spectral reflectance, etc., of the absorbent paper may be measured. Furthermore, the color difference may be determined or quantified by expressing it numerically. Figure 2 is a schematic diagram illustrating the wiring board of the present invention (referred to as the standard board) used as a standard for evaluating wiring boards.

[0038] Examples of standard substrates (evaluation substrates) 102 include glass epoxy substrates, glass composite substrates, paper phenolic substrates, paper epoxy substrates, ceramic substrates, flexible substrates, metal-based substrates, and rigid substrates. The structure is not limited to laminated substrates; build-up substrates, any-layer substrates, COF (Chip on Film), TAB (Tape Automated Bonding) substrates, etc., are also acceptable.

[0039] Furthermore, the present invention is not limited to the substrate 102 on which the wiring pattern 104 is formed, but can also be applied to or used in metal parts, thin film forming materials, electronic components, plated parts, and metal parts. A wiring pattern 104 is formed on the substrate 102. Multiple types of L / S (line / space) patterns are formed in the wiring pattern according to the purpose.

[0040] Figure 2 illustrates one type of copper wiring pattern on a single substrate 102. However, in this embodiment, multiple copper wiring patterns 104 with different L / S (line / space) configurations are simultaneously formed or fabricated on a single substrate 102, and then separated into evaluation substrates with different L / S configurations. By simultaneously forming multiple types of L / S configurations with different configurations and applying the same etching conditions, the differences in L / S configurations become clear.

[0041] In Figure 2, only a few copper wiring patterns are shown, but in reality, more than 100 wires (sets) are formed with spacing (S) of 0.5 mm, 1 mm, etc. Generally, flux 101 is applied or printed onto the copper wiring patterns.

[0042] The copper wiring pattern 104 is not limited to those arranged or configured on a plane. The present invention can also be applied to substrates and films in which multiple wirings are intersected via an insulating material. Furthermore, the present invention can be applied to the evaluation and verification of contact holes (via holes, etc.) of wiring boards.

[0043] Figure 2(b) is a cross-sectional view along line AA' of Figure 2(a). Flux 101 (not limited to flux, but including solder resist, solid solder, etc.) is applied or printed on the copper wiring pattern 104.

[0044] Connection pattern 105a electrically connects to copper wiring pattern 104a. The voltage applied to connection pattern 105a is applied to copper wiring pattern 104a. Connection pattern 105b electrically connects to copper wiring pattern 104b. The voltage applied to connection pattern 105a is applied to copper wiring pattern 104b.

[0045] Flux 101 is a soldering accelerator. Normally, an oxide film exists on the surface of metal, so simply melting solder with heat is not enough to bond it to the base material. Even if the oxide film is removed, it will combine with oxygen in the air and form a new oxide film. Flux 101 is composed of or formed from a main component, an activator, and a solvent.

[0046] The main component of flux 101 is a resin (rosin, synthetic resin, etc.). When the main component is heated, it removes the oxide film on the surface of the solder and the adherend, and at the same time protects the solder and the adherend surface and prevents re-oxidation.

[0047] Activators are additives that increase the ability of solder to remove oxide films from the surface of the soldered material. Depending on the type of solder and the soldering temperature and time, multiple types of activators may be included.

[0048] Flux 101 contains or has been added activators such as malonic acid, adipic acid, sebacic acid, and ethylamine hydrochloride. These activators generate ions.

[0049] Alcohol-based solvents are used as the solvent to dissolve the solid resin, which is the main component. They also adjust the viscosity of flux 101, improving uniform application to printed circuit boards and other materials, as well as wetting the base material and penetration into gaps.

[0050] For soldering to be successful, an alloy must form between the base material and the solder under normal soldering conditions (solder melting point plus 30-80°C). To achieve this, both the base material and the solder must be in an active state (atomic state).

[0051] Flux plays a role in activating the solder and base metal, and also in protecting the activated surface by preventing re-oxidation due to contact with oxygen in the atmosphere.

[0052] Migration is often caused, particularly by the effects of activators. Activators used in Flux 101 include organic acids, amino acids, amines, and amine hydrohalides.

[0053] Since the selection of flux significantly impacts the efficiency of soldering work, the primary criterion is naturally the flux's workability, or rather, its effectiveness. On the other hand, from the perspective of its use in assembling electronic components, the flux's corrosiveness and electrical insulation properties, i.e., its reliability, are also important factors.

[0054] These two criteria, efficacy and reliability, are contradictory: highly active fluxes are highly corrosive, while non-corrosive fluxes, if they have any activity, it is very low. Many electronic components are sensitive to corrosion.

[0055] The quality of the copper wiring and the selection of flux for the line / space (L / S) of the copper wiring (especially S (space)) are important, but in practice, it is impossible to determine the quality of the selection and the suitability of the combination of the target wiring board and flux without using a wide variety of fluxes on the target wiring board and conducting implementation evaluations.

[0056] This invention addresses this problem by providing a technical concept that allows for the determination, evaluation, and judgment of the quality of flux selection and the suitability of the combination of target wiring board and flux, without requiring implementation evaluation.

[0057] For migration, S (space) is particularly important. Migration tends to occur more easily when S (space) is narrower than a predetermined distance. Since L (line) is affected by the surface area of ​​the copper wiring (copper foil) pattern, it is preferable to manufacture evaluation substrates with a common L (line) width and varying S (space), as shown in Figure 4.

[0058] In the embodiments of this invention, the wiring pattern is described as being made of copper foil, but it is not limited to this. The present invention can also be applied to wiring patterns made of aluminum. Furthermore, the wiring pattern may be made of other metals such as iron, or a metal configuration. Needless to say, the present invention can also be applied to metal plating.

[0059] Figures 2(b), 3, and 4 show cross-sectional views along line AA' in Figure 2(a). The thickness of the copper wiring pattern is D. When copper wiring patterns 104 with different L / S (lines / space) are formed on a single cutout substrate, the thickness D of the copper wiring patterns 104 on each cutout substrate will be the same. Therefore, it is preferable to form copper wiring patterns 104 with different L / S (lines / space) on cutout substrates.

[0060] The occurrence of migration is also affected by the thickness D of the copper foil. Even if the L / S (line / space) is changed, the thickness D of the copper foil is formed to be the same. With the thickness D of the copper foil kept constant, flux 101, etc., is applied, and the evaluation method and evaluation apparatus of the present invention are applied. Needless to say, this invention can be applied not only to the L / S evaluation of the wiring pattern 104, but also to the evaluation and verification of the thickness of the wiring pattern.

[0061] A longer length K for the copper wiring pattern 104 leads to better evaluation and assessment results of migration in the implementation of the present invention. The longer the distance between the copper wiring pattern 104a and the copper wiring pattern 104b, the greater the impact of migration occurrence.

[0062] Furthermore, problems such as flux residue, flux reliability, flux acid value, suitability of solder paste, residue from solder paste, electronic component mounting reliability, poor reflow conditions, and poor cleaning are also likely to occur. Therefore, by implementing the evaluation method of the present invention and using the evaluation apparatus of the present invention, it becomes easier to quantify the amount of problems and implement countermeasures.

[0063] The present invention relates to a method and apparatus that can quantify not only the selection and evaluation of flux 101 and solder resist 101, but also the quality of soldering, solder selection, and soldering condition, and clarify countermeasures, and is applicable to such methods.

[0064] In the embodiment shown in Figure 3, a copper wiring pattern 104 is formed on the substrate 102. The L / S (line / space) of the wiring pattern can be configured or manufactured in multiple types depending on the purpose.

[0065] Figures 3(a), 3(b), and 3(c) in Figure 3 each have different L / S (line / space) configurations. These configurations (forms) are fabricated or configured on a single substrate 102.

[0066] Figure 3(a) shows L1 / S1 (line / space), Figure 3(b) shows L2 / S2 (line / space), and Figure 3(c) shows L3 / S3 (line / space). Flux 101 is applied to each substrate, and the evaluation method of the present invention is carried out. The copper wiring pattern in Figure 3 allows for evaluation of migration and other processes using different L / S (line / space) configurations.

[0067] Figures 4(a), 4(b), and 4(c) in Figure 4 show identical L (lines) but different S (spaces). Multiple configurations (forms) are fabricated or configured on a single substrate 102.

[0068] Figure 4(a) is S1 (space), Figure 3(b) is S2 (space), and Figure 3(c) is S3 (space). Flux 101 is applied to each substrate, and the evaluation method of the present invention is carried out. The copper wiring pattern in Figure 4 allows for evaluation of migration and other processes at different S (space) intervals.

[0069] Space (S) is important for evaluating migration. The narrower (shorter) the space (S), the more likely migration is to occur. In the evaluation of migration according to this invention, a narrower line (L) is better because migration is more likely to occur. By evaluating substrates 102 with different space (S) configurations, it is possible to evaluate or determine how much space (S) is required. This determination can be made quantitatively based on the type, quality, and configuration of the flux 101. Multiple copper wiring patterns 104 with different L / S (line / space) or S (space) configurations are simultaneously formed or fabricated on the substrate 102.

[0070] Using the evaluation substrates shown in Figures 2, 3, and 4, cleaning is performed before applying flux 101. The occurrence of migration differs depending on the cleaning solution or cleaning time. Therefore, by using the same flux 101 but varying the cleaning solution, cleaning time, and cleaning method, the evaluation method of the present invention can be used to evaluate and determine which cleaning solution, cleaning time, and cleaning method are appropriate.

[0071] Although Figure 2 shows only a few copper wiring patterns, in reality, more than 100 copper wiring patterns 104 are formed with equal spacing (S) of 0.5 mm, 1 mm, etc. Flux 101 is applied or printed onto the copper wiring patterns.

[0072] Connection pattern 105a electrically connects to copper wiring pattern 104a. The voltage applied to connection pattern 105a is applied to copper wiring pattern 104a. Connection pattern 105b electrically connects to copper wiring pattern 104b. The voltage applied to connection pattern 105a is applied to copper wiring pattern 104b. A voltage application land is formed at one end of connection pattern 105 as needed.

[0073] The present invention involves immersing a substrate 102 coated with flux 101 in water such as deionized water to extract metal ions such as copper that constitute the copper foil. Alternatively, water or steam 202 may be sprayed onto the substrate.

[0074] Ionic residue derived from the flux dissolves into aqueous solution 202. Higher ion concentration in aqueous solution 202 results in higher conductivity. Ion concentration can be determined by conductivity. Ionic residue and ion concentration are closely related to migration occurrence. Therefore, migration occurrence can be quantified by measuring conductivity with a conductivity meter or similar device.

[0075] After adsorbing metal ions with an ion exchange resin, the ion exchange resin is placed in a regeneration solution to regenerate the resin and extract the metal ions into the regeneration solution. The regeneration solution is then neutralized, and absorbance measurements are performed.

[0076] Figure 1 is an explanatory diagram of the evaluation method for the wiring board of the present invention. Flux 101 and solder resist 101 are applied to the substrate 102 described in Figures 1, 2, and 3 according to the embodiment.

[0077] For example, to evaluate the occurrence of migration that depends on the type of flux 101, flux 101 is applied to the copper wiring patterns 104 of multiple copper wirings as described in Figures 3 and 4.

[0078] Examples of methods for applying flux 101 include brush application, dripping, and spraying. The evaluation method for the wiring board of the present invention can also be applied to determine which of these methods is appropriate.

[0079] When evaluating the appropriate type and quality of flux 101, the evaluation is performed by applying flux 101. For example, flux 101 has a cleaning effect, an antioxidant effect, and a surface tension reduction effect. By changing the type of flux 101, the wiring board evaluation method and wiring board evaluation apparatus of the present invention can be applied.

[0080] The present invention is not limited to flux 101, and it goes without saying that it can be replaced with solder resist, solder, flux-containing solder, etc.

[0081] The period for immersing the substrate 102 in water 202 is 12 to 36 hours. The water 202 is also heated by a heater (heater / cooler) 207. The heating temperature is 50-80°C and is maintained at a predetermined value. The amount of copper ions leaching out from the copper wiring pattern 104 varies depending on the immersion time and heating temperature. If the oxidizing properties of the active substance contained in flux 101 are strong, the amount of copper ions leaching out from the copper wiring pattern 104 will be greater.

[0082] The present invention is not limited to water 202. Solutions such as alcohol may also be used. If water is used, pure water is preferred, but if ion-exchanged water is used, there will be no difference in the color change caused by the reagent. Aqueous solution 202 is a solution; it is not limited to water. If the copper wiring pattern 104 is heavily coated with flux 101, the amount of copper ions that leach out from the copper wiring pattern 104 will decrease.

[0083] Basically, the more copper ions that flow out from the copper wiring pattern 104, the more likely migration is to occur. This invention chelates copper ions and produces color with a color-developing agent. The degree of color development can be measured by measuring the absorbance. Therefore, in principle, the likelihood of migration occurring can be quantified by the amount of copper ions that flow into the water. Furthermore, the greater the amount of ion residue, the more likely migration is to occur. This invention measures and quantifies the ion residue using a conductivity meter or the like. The evaluation of the wiring board is quantified using ion residue (ion concentration) and absorbance measured with a conductivity meter or similar device.

[0084] The amount of copper ions released and ionized varies depending on the contents of flux 101 (active substances, etc.), the type of flux 101, the amount of surface oxidation of the copper wiring pattern 104, the cleanliness of the copper wiring pattern, etc. It also varies depending on the line / space (L / S) of the copper wiring pattern. This invention makes it possible to determine the minimum required space (S) and the appropriate activity level of flux 101 by quantifying the amount of copper ions released by absorbance.

[0085] The amount of metal ions (copper ions) released varies depending on the contents (active substances, etc.) of the flux 101 or solder resist 101, viscosity, coverage of the copper wiring pattern 104, degree of cleanliness of the copper wiring pattern 104, ambient temperature, L / S ratio of the copper wiring pattern 104, etc. By quantifying the changing amount of metal ions (copper ions), it is possible to clarify and determine design guidelines for the copper foil pattern (copper wiring pattern) 104, cleaning guidelines for the flux 101 or solder resist 101, etc., and the substrate 102.

[0086] In this invention, a substrate 102 coated with flux 101 is immersed in deionized water to extract metal ions such as copper that constitute the copper foil. The metal ions are adsorbed with an ion exchange resin, and then the ion exchange resin is placed in a regeneration solution to regenerate the ion exchange resin and extract the metal ions into the regeneration solution. The regeneration solution is neutralized and absorbance measurement is performed.

[0087] Flux residue can cause migration, deterioration of high-frequency characteristics, and defects in resin encapsulation. Whether flux residue after soldering poses a quality problem depends on the specific requirements of the target mounted product and subsequent processes. Typical defects caused by flux residue include reduced electrical reliability such as migration and deterioration of high-frequency characteristics, as well as non-wetting, curing failure, and poor adhesion in the resin molding process. The ion residue and ion concentration of the flux are quantified by measuring conductivity using an ion conductivity meter.

[0088] This invention uses a chelating reagent to measure the concentration of metal ions in a solution and performs absorbance analysis. The following examples illustrate the detection of copper ions, but the present invention is not limited thereto.

[0089] It is preferable to use TAN(1-(2-thiazolyl azo)-2-naphthol) for mercury ions, bathophenanthroline for iron ions, and PAN(1-(2-Pyridylazo)-2-naphthol) for cobalt ions. The extractant can also be o-nitrophenyl octyl ether (o-NPOE).

[0090] Any metal ion can be used, but copper ions, mercury ions, cobalt ions, and iron ions are examples. Any colorant can be used as long as it reacts with these ions to produce color.

[0091] For copper ions, bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) is preferred as a chelating agent; for mercury ions, TAN; for iron ions, bathophenanthroline; and for cobalt ions, PAN is preferred.

[0092] Furthermore, the extractant can be any substance that can effectively extract the reaction products generated by the reaction of these metal ions with the colorant, such as ethers like o-NPOE or esters like phthalates. Figure 5 is an explanatory diagram of an evaluation apparatus for a wiring board according to the present invention as one embodiment, and Figure 1 is an explanatory diagram of an evaluation apparatus for a wiring board according to the present invention as one embodiment. The evaluation apparatus and evaluation method for the wiring board of the present invention will be described below with reference to Figures 1 and 5.

[0093] As shown in Figure 1(a), the substrate 102 is immersed in ion-exchanged water (water) 202. The water 202 is heated by a heater (heater / cooler) 207 and maintained at a predetermined temperature of 50-70°C. The water temperature depends on the progress of migration. The heater (heater / cooler) 207 is temperature-controlled by a heater (heater / cooler) controller 501.

[0094] Furthermore, since the heater (heating / cooling device) 207 not only heats but also maintains a predetermined temperature, it is preferable that it also has a cooling function. In other words, it is a heating / cooling device (heating / cooling device, temperature setting circuit, temperature maintainer) 207. Therefore, the heater (heating / cooling device) 207 may be replaced with other heating devices / heating means or cooling devices / cooling means such as a Peltier element or a hot air blower. The same applies to other embodiments of the present invention. The container 201a is opened and closed by operating the solenoid valve 503a located on the output side of the tank (water) 505. The solenoid valve 503 is controlled by the control circuit 517. The solenoid valve 503 may also be operated manually.

[0095] The deionized water 202 is heated or cooled by the heater (heater / cooler) 207a to maintain a predetermined temperature. The deionized water 202 is stirred by the stirring fan 502a.

[0096] The immersion time for the substrate 102 in deionized water (water) 202 is set to a predetermined time of 12 to 36 hours. A longer immersion time results in a greater amount of metal ions dissolving into the deionized water 202. However, the amount of metal ions that dissolve may plateau over time. Therefore, the optimal immersion time should be determined through experimentation. Furthermore, ion residue from the flux also dissolves into the deionized water (water) 202. The ion residue dissolves relatively quickly.

[0097] Next, as shown in Figure 1(b1), water 202 is poured into (moved) container 201b. Also, as shown in Figure 1(b2), water 202 is poured into (moved) container 201e.

[0098] In Figure 5, the solenoid valve 503b is opened, allowing the contents to move through the piping 518a to container 201b. Additionally, the solenoid valve 503be is opened, allowing the contents to move through the piping 518b to container 201e. Pump 504 is used to move the aqueous solution 202 (water 202) in a short time and in a predetermined volume.

[0099] The container 201b is filled with or contains an ion exchange resin 203. A cation exchange resin (cation exchange resin) is an example of the ion exchange resin 203.

[0100] A cation exchange resin (cation exchange resin) has negatively charged fixed ions inside, and positively charged ions that electrically neutralize them. These positive ions can exchange with other ions. Ion exchange resin 203 adsorbs positive ions present in water. Examples of cation exchange resins (cation exchange resins) include strongly acidic cation exchange resins and weakly acidic cation exchange resins.

[0101] Strong acid cation exchange resins can be used in a wide pH range and can adsorb many positive ions. The ease or difficulty of ion exchange with ion exchange resins varies depending on the type of ion. Generally, strong acid resins tend to exchange and capture ions with higher charge more easily, and hydrated ions with lower atomic numbers (higher atomic numbers) are more easily exchanged. Therefore, copper ions are easily adsorbed. Strongly acidic cation exchange resins are regenerated and reused using chemicals. These chemicals are generally hydrochloric acid or sulfuric acid aqueous solutions. Strongly acidic cation exchange resins are difficult to regenerate due to their strong acidity, and a larger amount of regenerating agent than the theoretical chemical equivalent is required to achieve a high regeneration rate.

[0102] A weakly acidic cation exchange resin may be used as ion exchange resin 203. A weakly acidic cation exchange resin is a resin that has a carboxylic acid group as an exchange group and exhibits weak acidity, similar to acetic acid.

[0103] Chemically, there are two types: methacrylic acid-based and acrylic acid-based. The difference lies in the acidity of the exchange group. Methacrylic acid-based resins can be used in a pH range of approximately 5 or higher, while acrylic acid-based resins can be used in a pH range of approximately 4 or higher. Due to the limited pH range in which they can be used, their applications are more limited compared to strongly acidic cation exchange resins, but they have the advantage of being easily regenerated.

[0104] The adsorption strength (selectivity) of weakly acidic cation exchange resins to various ions is roughly similar to that of strongly acidic cation exchange resins. Selectivity increases with higher valency ions. The selectivity for H ions is very high. Therefore, regeneration is easy when H ions are exchanged with other cations and then returned to the R-COOH form using a chemical agent (generally hydrochloric acid or sulfuric acid aqueous solution) for repeated use. Regeneration is possible with only a slightly larger amount of chemical agent than the theoretical stoichiometric equivalent.

[0105] Alternatively, chelate resins may be used as ion exchange resins. Chelate resins form complexes by binding very strongly to specific metal ions. They exhibit selective adsorption properties for metal ions and can selectively adsorb specific metal ions.

[0106] Chelate resins exhibit significantly higher selectivity for specific metal ions compared to cationic or anionic resins. Since the selectivity for metal ions varies depending on the type of chelate resin, it is necessary to select the appropriate chelate resin based on the target metal species.

[0107] Flux 101 is composed of or formed from a main component, an activator, and a solvent. The main component is a resin (rosin, synthetic resin, etc.). When the main component is heated, it removes the oxide film on the surface of the solder and the adherend, and at the same time protects the solder and the adherend surface and prevents re-oxidation.

[0108] Activators are additives that increase the ability of solder to remove oxide films from the surface of the soldered material. Depending on the type of solder and the soldering temperature and time, multiple types of activators may be included.

[0109] Flux 101 contains or is supplemented with activators such as malonic acid, adipic acid, sebacic acid, and ethylamine hydrochloride. These activators generate ions. An alcohol-based solvent is used to dissolve the solid resin, which is the main component. It also adjusts the viscosity of the flux, improving uniform application to printed circuit boards, wetting of the base material, and penetration into gaps.

[0110] As shown in Figure 1(b1), the ion exchange resin 203 is added to water 202 containing copper ions. Alternatively, the water 202 containing copper ions is poured into a container 201b in which the ion exchange resin 203 is placed.

[0111] In Figure 5, an ion exchange resin 203 is placed inside container 201b, and water 202 from container 201a is injected into container 201b using a pump 504. The ion exchange resin 203 adsorbs metal ions (copper ions) from the injected water 202.

[0112] In Figure 1(a), in addition to metal ions (for example, copper ions), the main resin component dissolves into the water 202, causing the water 202 to become colored. When measuring the absorbance of the colored water 202, the dissolved resin has an effect, making it impossible to selectively detect copper ions.

[0113] In Figure 1(b1), the ion exchange resin 203 selectively adsorbs metal ions. The main resin component is not adsorbed. In Figure 2, the water 202 poured into container 201b is colored because not only copper ions but also the main resin component has dissolved into it.

[0114] The ion exchange resin 203 adsorbs copper ions but does not adsorb the resin components of the main agent. As a result, the ion exchange resin 203 adsorbs copper ions and can separate them from the water 202. Next, the ion exchange resin 203 is washed with water to wash away any resin components attached to its surface.

[0115] The ion exchange resin 203, which has been washed with water, is immersed in the ion exchange resin 203 regeneration solution (ion exchange resin regeneration aqueous solution) 204 filled in the container 201c, as shown in Figure 1(c1).

[0116] The regeneration solution (regeneration aqueous solution) 204 is either hydrochloric acid or sulfuric acid aqueous solution. By using the regeneration solution 204, the ion exchange resin 203 can be reused. By immersing the ion exchange resin 203 in the regeneration solution 204, the ion exchange resin 203 releases metal ions. If the strongly acidic ion exchange resin 203 is of the Na->H type, it is preferable to use a 3-8% hydrochloric acid aqueous solution or a sulfuric acid aqueous solution as the regeneration solution (regeneration aqueous solution) 204.

[0117] For H->Na conversion, pack the column with ion exchange resin and pass 2-4 BV* (*BV: Bed Volume: 1 BV is defined as the volume of packed ion exchange resin) of 0.5-2.0% sodium chloride aqueous solution or sodium hydroxide aqueous solution through it. The contact time between the liquids should be at least 15 minutes (acidic or neutral solution will flow out while the ionic form is being converted).

[0118] For H->K conversion, pass 3-4.5 BV* of a 0.5 M (~3 wt%) potassium hydroxide aqueous solution through the device. For Na->H conversion, pass 5-6 BV* of a 5-8% hydrochloric acid aqueous solution through the device. For example, if you want to convert an H-type cation exchange resin to a Na-type resin, you can do so by immersing and rinsing it in a 1N sodium chloride solution.

[0119] As shown in Figure 1(c1), when the ion exchange resin 203 is immersed in the regeneration solution (ion exchange resin regeneration aqueous solution) 204, metal ions (copper ions) leach into the regeneration solution 204. The metal ions can be extracted into the regeneration solution 204.

[0120] In Figure 5, an ion exchange resin regeneration aqueous solution (regeneration solution) 204 is injected from a tank (regeneration solution) 507 into a container 201b in which an ion exchange resin 203 is placed. The injection is performed by a control circuit 517 controlling a solenoid valve 503c. A heater (heating / cooling device) 207b is placed inside the container 201b to maintain the regeneration solution 204 at a predetermined temperature.

[0121] Next, as shown in Figure 1(d1), a neutralizing aqueous solution (neutralizing solution) 205 is added to the regeneration solution 204 in container 201d. When the regeneration solution 204 is hydrochloric acid (HCl), sodium hydroxide (NaOH) is exemplified as the neutralizing solution 205. Neutralization occurs when an acid and a base react and cancel each other out. When hydrochloric acid and a sodium hydroxide aqueous solution are mixed, the following reaction occurs, producing sodium chloride and water.

[0122] Neutralization is preferable to neutralize the pH during the reaction of the reagents shown in Figures 1(e1) and 5. However, it goes without saying that the neutralization step can be omitted if the pH does not affect the color development of the reagent, or if the effect is negligible.

[0123] In Figures 1(e1) and 5, the reagent is added dropwise, color is developed, and the absorbance is measured. However, the absorbance may also be measured after concentrating the aqueous solution after color development. Alternatively, the colored aqueous solution may be adsorbed onto an absorbent paper or similar material, and then the spectral transmittance or spectral reflectance of the absorbent paper may be measured. When using copper ions as a reagent, it is preferable to use at least one of neocuproine and vasocuproine.

[0124] In Figures 1(e1) and 5, absorbance (Abs) is shown to be measured, but the method is not limited to absorbance. Any method that can quantify the degree or proportion of color development due to metal ions, etc., is acceptable. For example, reflectance and transmittance are also acceptable.

[0125] In Figure 5, neutralizing solution (neutralized aqueous solution) 205 is poured into container 201b from tank (neutralizing solution) 508, and the regeneration solution (regeneration aqueous solution) 204 is neutralized. During neutralization, the pH is measured using a pH meter 519. The pH is adjusted to be between 5 and 9. Preferably, the pH is adjusted to be between 6 and 8.

[0126] The neutralizing solution 205 is injected into the container 201b by opening the solenoid valve 503d. The amount and rate of injection of the neutralizing solution 205 are variable or constant depending on the degree to which the solenoid valve 503d is opened or closed.

[0127] In the above embodiments, the neutralizing solution 205 was injected from the tank (neutralizing solution) 508, but this is not the only way to do so. Needless to say, buffer solutions, reducing agents, and counterion solutions may also be added and injected in addition to the neutralizing solution. Furthermore, neutralization is not limited to aqueous solutions; neutralizing agents consisting of solids or powders may also be used. Examples of buffer solutions include ammonium acetate, hydroxylamine sulfate ((NH3OH)2SO4) as a reducing agent, and picric acid solution as a counterion solution.

[0128] The pH-adjusted regeneration solution 204 is sent to container 515. The water is supplied to the container by the control of the solenoid valve 503g. The amount of water supplied to the container can be as small as 1-4cc, as long as the absorbance can be measured. The remaining regeneration solution 204 is discharged from container 201b by opening the solenoid valve 503f. After the regeneration solution 204 is discharged, the ion exchange resin 203 is washed with water. In Figure 1(e1), the neutralized regeneration solution 204 becomes the evaluation solution 516, and reagent 206 is added dropwise to the evaluation solution 516.

[0129] When the target component is copper ions, vasocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) is exemplified as reagent 206. Vasocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) reacts with copper ions, and vasocuproine coordinates to the copper ions as a ligand, selectively forming a complex with the counterion. A model of vasocuproine complexed with copper ions is shown in Figure 11(b).

[0130] Bathocuproine, when coordinated to a copper ion, has a positive charge, and a negatively charged counterion is added to form an ion pair with it. Picric acid is one example of such a counterion. This complex develops a color ranging from pale yellow to red depending on its concentration. It is preferable to maintain a temperature of approximately 30°C to 60°C to allow for color changes. The color development varies depending on the pH of the evaluation solution 516. It is preferable to adjust the pH to obtain good color development. In addition, the reaction of target components such as metal ions with the colorant decreases due to oxidation, and they become more susceptible to interference from other metal ions. For this reason, a buffer solution and a reducing agent can be added to the solution containing the target components. This allows the pH to be maintained within a predetermined range and the reduced state to be maintained.

[0131] In addition to vasocuproine, neocuproine (2,9-dimethyl-1,10-phenanthroline, DMPHEN) may also be used. A model of neocuproine forming a complex with copper ions is shown in Figure 11(a).

[0132] The evaluation method of the present invention is characterized by injecting neocuproine or vasocuproine into an evaluation solution (evaluation solution) 516 containing copper to form a complex between copper and neocuproine or vasocuproine, and then performing absorbance analysis on the solution containing the complex. By taking an evaluation solution 516 and adding bathocuproine, the copper content in the sample can be measured without being affected by oxidation. The same results can be obtained for neocuproine, which reacts specifically with copper, similar to bathocuproine. The present invention involves immersing a substrate 102 coated with flux 101 or the like in deionized water to extract metal ions such as copper that constitute the copper foil. After the metal ions are adsorbed with an ion exchange resin, the ion exchange resin is placed in a regeneration solution to regenerate the ion exchange resin and extract the metal ions into the regeneration solution. The regeneration solution is neutralized and absorbance measurement is performed.

[0133] Although copper ions have been used as an example, the present invention is not limited thereto. TAN(1-(2-thiazolyl azo)-2-naphthol) is preferred for mercury ions, bathophenanthroline for iron ions, and PAN(1-(2-Pyridylazo)-2-naphthol) for cobalt ions. Furthermore, o-nitrophenyl octyl ether (o-NPOE) can be used as the extractant.

[0134] Any metal ion can be used, but copper ions, mercury ions, cobalt ions, and iron ions are examples. Any colorant can be used as long as it reacts with these ions to produce color.

[0135] For copper ions, bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) is preferred as a chelating agent; for mercury ions, TAN; for iron ions, bathophenanthroline; and for cobalt ions, PAN is preferred.

[0136] Furthermore, the extractant can be any substance that can effectively extract the reaction products generated by the reaction of these metal ions with the colorant, such as ethers like o-NPOE or esters like phthalates.

[0137] Reagents such as bathophenanthroline are added dropwise to the evaluation solution 516 in container 515 from the reagent dispenser 514. A complex is formed by the reagent as shown in Figure 11, and the evaluation solution 516 changes color due to the formation of the complex and the reagent.

[0138] As shown in Figure 5, the spectrometer 511 generates light that has been spectrally separated by wavelength. This generated light becomes incident light 510a and is irradiated onto the evaluation solution 516 injected into the container 515. The evaluation solution absorbs or transmits the incident light 510a, and the emitted light 510b is incident on the photodetector 512. The absorbance (Abs) is measured from the relationship between the intensities of the incident light 510a and the emitted light 510b.

[0139] The spectrometer 511 is controlled by a control circuit (control device) 517. Light of a predetermined wavelength is irradiated from the spectrometer 511, and the light transmitted through the color-developing sample of the evaluation solution 516 is received by the photodetector 512. The received light is converted into a voltage signal or the like by the photodetector 512, the transmittance is calculated, and the absorbance is calculated from that transmittance. As a means of calculation, a computer equipped with a processor and memory or other storage means can be cited, and it is said to be capable of storing and executing a program that calculates transmittance from received voltage signals, etc., and calculates absorbance from transmittance.

[0140] The absorbance of copper complexes is around 485 nm. Therefore, it is preferable to determine the absorbance at 480 nm to 490 nm. As an example, colorimetric analysis is performed at 485 nm. Bathocuproic acid is added, and the absorbance at 485 nm is measured.

[0141] Figure 6 is a graph showing the relationship between wavelength and absorbance (Abs). The dashed line represents the case with low copper ion levels, the dotted line represents the case with high copper ion levels, and the solid line represents an intermediate measurement example between the low and high copper ion levels.

[0142] In Figure 1(a), when a large amount of copper ions are eluted from the evaluation substrate 102, the graph becomes the dotted line in Figure 6. When a small amount of copper ions are eluted from the evaluation substrate 102, the graph becomes the dashed line in Figure 6.

[0143] In all the graphs in Figure 1, the absorbance (Abs) is high near 485 nm. Therefore, the amount of copper ions can be quantified by measuring or determining the absorbance near 485 nm.

[0144] The solid, dotted, and dashed-dotted graphs show how the flux (including solder, solder resist, etc.) 101 changes depending on the type. This is because the flux 101 contains activators, and the oxidation state of the copper wiring pattern 104 changes depending on the type of activator. Since the oxidation state affects the occurrence of migration, the selection and evaluation of flux 101 can be quantified by measuring the absorbance at 485 nm for each type of flux 101.

[0145] Figure 7 shows an example in which the flux (solder resist) 101 is kept the same, but the cleaning method of the wiring board 102 is changed. The absorbance at 485 nm changes depending on the cleaning method. Therefore, by measuring the absorbance at 485 nm, the selection and evaluation of the cleaning method of the wiring board 102 can be quantified. The wavelength for measuring absorbance is preferably in the range of 470 nm to 495 nm, and particularly preferably in the range of 480 nm to 490 nm.

[0146] Figure 8 is a graph showing the change in absorbance over time when measuring absorbance at 485 nm. When a reagent such as bathocuproine is added dropwise to evaluation solution 516, color development begins. The absorbance (Abs) increases as the color develops. The color development reaches a saturation point in about 20 minutes. Therefore, it is preferable to measure the absorbance after stirring for at least 20 minutes after adding the reagent.

[0147] Figure 8 is a graph showing the change in absorbance (Abs) over time (h) as the time (h) for copper ions in water to dissolve from the substrate 102 after immersion in water, as shown in Figure 1(a). Absorbance is normalized to 1.0.

[0148] When the substrate 102 is immersed in water 202, copper ions leach from the copper wiring pattern 104 and other components into the water 202. As the amount of leached copper ions increases, the absorbance measured in Figure 1(e1) increases.

[0149] The elution of copper ions increases over time. As shown in the graph in Figure 8, the absorbance exceeds 0.75 (standard value) after 12 hours, and reaches a nearly saturated absorbance of 1.0 (standard value) after 18 hours. Therefore, it is preferable that the immersion time of the substrate 102 in Figure 1(a) be 18 hours or more. More preferably, it is preferable to immerse it for 24 hours or more.

[0150] In Figures 1(a) and 5, the substrate 102 is shown to be immersed in water 202, but this is not the only method. For example, water, hot water, steam, etc., may be sprayed onto the substrate 102.

[0151] Furthermore, while Figures 1(a) and 5 show the substrate 102 being immersed in water 202, immersed in water, or sprayed with water, the method is not limited to water 202. For example, the substrate 102 may be immersed in alcohol, immersed in alcohol, or sprayed with a solvent or diluent such as alcohol.

[0152] When measuring absorbance at 485 nm, etc., color development begins when a reagent such as bathocuproine is added dropwise to evaluation solution 516. The absorbance (Abs) increases as the color develops. The color development reaches a saturation point in about 20 minutes. Therefore, it is preferable to measure the absorbance after stirring for 20 minutes or more after adding the reagent. Figure 9 is a graph showing the measurement results of absorbance (Abs) for the space (S) (see Figure 4) of the copper wiring pattern 104 on the wiring board 102.

[0153] A higher absorbance indicates a greater amount of copper ions dissolving into water 202. A lower absorbance indicates a smaller amount of copper ions dissolving into water 202. The graph shows an inflection point at a spacing (S) of 0.15 mm. Therefore, it is preferable that the spacing (S) of the copper wiring pattern 104 be 0.15 mm or larger. Thus, a design guideline can be obtained that it is preferable to set the spacing S = 0.15 mm or larger for the copper wiring pattern 104 in the flux 101 used for the measured substrate 102.

[0154] Figure 10, similar to Figure 9, is a graph showing the measurement results of absorbance (Abs) relative to the space (S) (see Figure 4) of the copper wiring pattern 104 on the wiring board 102. Three cases are shown as examples, using flux A, flux B, and flux C. A higher absorbance indicates a larger amount of copper ions eluting into water 202. A lower absorbance indicates a smaller amount of copper ions eluting into water 202.

[0155] It is preferable to measure the fluorescence or phosphorescence characteristics in conjunction with, or instead of, the absorbance measurement. Neocuproine, vasocuproine, etc., form a complex with metal ions. When the evaluation solution 516 is irradiated with light of a wavelength in the ultraviolet region, the complex absorbs ultraviolet light and emits light.

[0156] The metal of the complex can be identified by the wavelength of light with high emission intensity, and the content of metal ions (copper ions) can be quantified based on the emission intensity. By considering both fluorescence (phosphorescence) emission characteristics and absorbance, the amount of copper ions (metal ions) eluted from copper wiring patterns, etc., can be quantified.

[0157] In the embodiments of the present invention, the detection or evaluation of the amount of copper ions leached from copper wiring patterns and the like is primarily illustrated, but the invention is not limited to this. For example, lead, tin, silver, etc., leaching from solder can be detected and evaluated using the evaluation method and apparatus of the present invention.

[0158] In the case of flux A, the graph shows an inflection point when the space (S) is near 0.2 mm. Therefore, it is preferable to use flux A so that the space (S) of the copper wiring pattern 104 is 0.2 mm or larger. Thus, when using flux A on the measured substrate 102, it is preferable to have a space S of 0.2 mm or larger for the copper wiring pattern 104, providing design guidelines and evaluation data.

[0159] In the case of flux B, the graph shows an inflection point when the space (S) is near 0.1 mm. Therefore, it is preferable to use flux B so that the space (S) of the copper wiring pattern 104 is 0.1 mm or larger. Thus, when using flux B on the measured substrate 102, it is preferable to have a space S of 0.1 mm or larger for the copper wiring pattern 104, providing design guidelines and evaluation data.

[0160] In the case of flux C, the graph shows an inflection point when the space (S) is near 0.15 mm. Therefore, it is preferable to use flux C so that the space (S) of the copper wiring pattern 104 is 0.15 mm or larger. Thus, we can obtain design guidelines, evaluation data, and design rules indicating that it is preferable to use flux C in the measured substrate 102 so that the space S of the copper wiring pattern 104 is 0.15 mm or larger. Based on the above, in the embodiment shown in Figure 10, it is preferable to use flux B when the space S of the wiring pattern 104 is narrow-pitch.

[0161] The graph in Figure 10 changes depending on the type, viscosity, and drying state of the flux 101 (solder resist 101). It also changes depending on the cleaning state of the substrate 102. Therefore, by implementing the wiring board evaluation method of the present invention, it is possible to determine design guidelines for the substrate 102 and selection criteria for the flux 101 to be used. Furthermore, quantitative evaluation data can be obtained.

[0162] In the above examples, the amount of copper ions leached from a wiring substrate, etc., was quantified using absorbance, but the present invention is not limited thereto. Substrates can be aluminum substrates, and wiring can be gold-plated, tin-plated, or zinc-plated. Metal ions leached from these can also be quantified using the evaluation method or apparatus of the present invention. Furthermore, the amount of mercury leached can also be evaluated.

[0163] It is preferable to use TAN(1-(2-thiazolyl azo)-2-naphthol) for mercury ions, bathophenanthroline for iron ions, and PAN(1-(2-Pyridylazo)-2-naphthol) for cobalt ions. The extractant can also be o-nitrophenyl octyl ether (o-NPOE).

[0164] Flux 101 contains activators. Flux 101 may contain several types of activators. Malonic acid, adipic acid, sebacic acid, ethylamine hydrochloride, etc., are included or added as activators in Flux 101. These activators generate ions. The shorter the carbon chain of the activator, the higher the ionization concentration, the greater the amount of copper eluted, and the higher the activity tends to be. The shorter the carbon chain of a carboxylic acid, the more contacts the carboxylic acid has with copper, and the greater the reactivity; therefore, the shorter the carbon chain, the higher the density of carboxylic acid at the reaction site.

[0165] Migration and dendrite formation are often facilitated by activators with high copper elution power. Due to the high elution power of the activator, copper dissolves as a positive ion at the positive electrode, is attracted to the negative electrode, accepts electrons there, is reduced, and precipitates. Therefore, evaluating and quantifying the ionization concentration of flux 101 is useful for designing or evaluating wiring boards.

[0166] Higher ion concentration results in higher conductivity. Decreasing ion concentration increases the resistance of the aqueous solution. Flux is applied to the evaluation substrate as described in Figures 2, 3, and 4, and current is passed through it. After current is applied, the evaluation substrate is immersed in the aqueous solution, and the resistance of the solution is measured, resulting in Figure 12.

[0167] Figure 12 shows that the horizontal axis represents the current-passing time, and the vertical axis represents the resistance value converted from the measured conductivity. 10 The values ​​are normalized in ohms. Time (h) = 0 represents the time when no current is applied and indicates the ionic residue of the flux. When current is applied, the ionic residue from the flux is consumed, and the resistance tends to approach that of a flux-free substrate.

[0168] Figure 13 is an explanatory diagram of the changes in ion residue. Numerous flux ions 523 are present between copper wiring patterns 104a and 104b on a wiring board coated with flux 101 (Figure 13(a)). When current is passed through copper wiring patterns 104a and 104b, the ions are consumed by the current (Figure 13(b)). The resistance increases due to the consumption of ions. When all ions are consumed, the increase in resistance stops (Figure 13(c)).

[0169] Figure 14 shows the conductivity (μS / cm) measured for L / S = 0.16 mm (solid line) and L / S = 0.32 mm (dotted line) at elapsed times of 20 hours (h) and 50 hours (h) of energization. The conductivity (μS / cm) of deionized water (dotted line) is 1.54 μS / cm.

[0170] Both L / S = 0.16 mm (solid line) and L / S = 0.32 mm (dotted line) show a decrease in conductivity due to current flow. After 50 hours, the conductivity is at the same level as deionized water.

[0171] If there is a large amount of ionic residue derived from the flux, migration and dendrite formation are likely to occur. Therefore, when selecting flux to be used in wiring boards, it is preferable to quantify the ionic residue. Ionic residue can be quantified by measuring conductivity. Furthermore, flux also contributes to the generation of copper ions.

[0172] Therefore, it is preferable to quantify the amount of copper ions by measuring absorbance. The present invention is highly effective in designing wiring boards by quantifying ion residue (ion concentration) and copper ions.

[0173] As shown in Figure 1(b2), the aqueous solution 202 in container 201a is poured into container 201e as aqueous solution 202a. The aqueous solution 202a is diluted with ion-exchanged water 524 to a ratio of 100 to 1000 times. Next, as shown in Figure 1(c2), the aqueous solution is boiled in the heater (heater / cooler) 207c for a period of 30 seconds to 120 seconds.

[0174] Next, as shown in Figure 1(d2), container 201e is immersed in water 525 filled in container 201f and left to stand until it reaches 20(±2)°C. The water 525 is maintained at 20(±2)°C by heater (heater / cooler) 207c. Next, as shown in Figure 1(e2), the electrical conductivity (conductivity) (μS / cm) of the aqueous solution 202a in container 201e is measured.

[0175] Electrical conductivity (electrical conductivity, electrical conductivity) is a value that indicates how easily electricity flows through something. Generally, when expressing electrical conductivity, the specific conductivity Sm, which is the quantity per unit length, is used rather than S. -1 The conductivity is expressed in (S / m). This is because expressing electrical conductivity per unit length is more convenient for describing the properties of a material. In this example, μS / cm is used as the scale for the conductivity meter. A conductivity meter is a device that measures electrical conductivity by applying an alternating voltage between two electrodes. The electrical conductivity of water increases as the amount of ionic impurities increases.

[0176] As shown in Figure 5, the aqueous solution 202 in container 201a is injected into container 201e via piping 518d by opening the solenoid valve 503e. The aqueous solution injected into container 201a is referred to as aqueous solution 202a.

[0177] Deionized water 524 is poured into container 201e from tank (water) 522. The aqueous solution 202a is diluted with deionized water 524 to a ratio of 100 to 1000 times.

[0178] The aqueous solution 202a is boiled in the heater (cooler) 207c for a period of 30 to 120 seconds. The aqueous solution 202a is stirred by the stirring fan 502b. The heater (cooler) 207c is controlled by the heater (cooler) controller 501, and the aqueous solution 202a is boiled or maintained at a predetermined temperature. After boiling, the aqueous solution 202a is cooled to 20 (±2)°C in the heater (cooler) 207c.

[0179] Solution 202a is delivered to container 201g via piping 518e. The injection of solution 202a into container 201g is controlled by solenoid valve 503j. The electrical conductivity (conductivity) of solution 202a is measured by conductivity meter 521.

[0180] The conductivity meter 521 and absorbance meter 509 are controlled by the control circuit 517. Light of a predetermined wavelength is irradiated from the spectrometer 511, and the light transmitted through the color-developing sample of the evaluation solution 516 is received by the photodetector 512. The received light is converted into a voltage signal or the like by the photodetector 512, the transmittance is calculated, and the absorbance is calculated from that transmittance. The measurement data from the conductivity meter 521 indicates the ion concentration, allowing for the quantification of the activity of flux 101 and other components. The reactivity of the copper wiring pattern 104 with copper (Cu) can be quantified from the absorbance and electrical conductivity (conductivity).

[0181] The present invention can be applied to methods for predicting migration resistance, evaluating migration, evaluating the mounting of electronic components, evaluating soldering, predicting soldering, and determining the quality of wiring boards for printed circuit boards, electronic circuit boards, laminated boards, laminated films, film wiring boards, etc.

[0182] Furthermore, it is not limited to wiring boards, but can also be applied to metal-plated components, metal coatings, metal parts, electrical components, electrical elements, etc. In addition, it can be applied to electronic devices that use metal objects or thin metal films, such as touch panel devices (touch panels), EL display devices (EL display panels), and liquid crystal display devices (liquid crystal display panels).

[0183] The technical concepts disclosed in this specification and these drawings are not limited to the application of these electronic devices. Needless to say, they can also be applied to devices such as mobile devices, television equipment, home appliances, communication equipment, and personal computer equipment, in which components such as thin metal films are formed or arranged on the outside.

[0184] Furthermore, it goes without saying that this technology can also be applied to home appliances, communication equipment, and other devices equipped with touch panel devices (touch panels), EL display devices (EL display panels), and liquid crystal display devices (liquid crystal display panels).

[0185] Although the present invention has been described above based on embodiments, the present invention is not limited to the above embodiments, and modifications can be made without departing from the spirit of the invention. Furthermore, some or all of the embodiments can be combined. [Industrial applicability]

[0186] This disclosure is also useful for designing wiring boards, manufacturing wiring boards, and evaluating electronic devices such as touch panel devices, EL or liquid crystal display devices, etc. [Explanation of Symbols]

[0187] 101 Flux 102 circuit boards 104 Copper Wiring Pattern 105 Connection Patterns 201 Container 202 Water (aqueous solution) 203 Ion exchange resin 204 Ion exchange resin regeneration aqueous solution 205 Neutralized aqueous solution 206 Reagents 207 Heater (heating and cooling device) 501 Heater (heating / cooling) controller 502 Agitation fan 503 Solenoid valve 504 Pump 505 Tank (Water) 507 Tank (Regeneration Solution) 508 Tank (neutralizing solution) 509 Absorbance measuring device 510a incident light 510b Transmitted light 511 Spectrometer 512 Photodetector 514 Reagent Dispenser 515 Container 516 Evaluation Solution 517 Control Circuit 518 Piping 519 pH measuring instrument 521 Conductivity meter 522 Tank (Water) 523 Aeon 524 Ion-exchanged water 525 water

Claims

1. A first means for applying or printing flux or resist onto a substrate having metal, A second means of immersing the metal substrate in a first aqueous solution, or spraying or atomizing the metal substrate with the first aqueous solution, A third means for measuring the conductivity of the first aqueous solution, A fifth means for adsorbing the metal ions of the first aqueous solution onto an ion exchange resin, A sixth means for eluting the metal ions adsorbed on the ion exchange resin into a second aqueous solution, A method for evaluating a flux or resist substrate, characterized by having a seventh means for measuring the amount of metal ions in the second aqueous solution.

2. A first means for applying or printing flux or resist onto a substrate having metal, A second means of immersing the metal substrate in a first aqueous solution, or spraying or atomizing the metal substrate with the first aqueous solution, A third means for measuring the conductivity of the first aqueous solution, A fifth means for adsorbing the metal ions of the first aqueous solution onto an ion exchange resin, A sixth means for eluting the metal ions adsorbed on the ion exchange resin into a second aqueous solution, An eighth means for dropwise adding or mixing a reagent that forms a complex with the metal ion to the second aqueous solution, A method for evaluating a flux or resist substrate, characterized by having a ninth means for measuring the color development of the second aqueous solution.

3. The method for evaluating a flux or resist substrate according to claim 1 or 2, characterized in that the third means involves measuring the conductivity with respect to elapsed time or measuring the resistance value.

4. The aforementioned metal is copper, The method for evaluating a flux or resist substrate according to claim 1 or 2, characterized in that a copper wiring pattern is formed on the substrate.

5. Multiple substrates are prepared by applying or printing different types of flux, A method for evaluating flux or resist substrates according to claim 1 or 2, characterized by measuring the ion content or conductivity of the first aqueous solution of the plurality of substrates.

6. The method for evaluating a flux or resist substrate according to claim 1 or 2, characterized in that the ion exchange resin is a chelate resin.

7. The first aqueous solution is ion-exchanged water, The method for evaluating a flux or resist substrate according to claim 1 or 2, characterized in that the second aqueous solution is an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution.

8. The aforementioned metal is copper, The reagent is neocuproine or vasocuproine. The aforementioned color change measurement is a measurement of absorbance, The method for evaluating a flux or resist substrate according to claim 2, characterized in that the wavelength range for measuring absorbance is 470 mm to 495 nm.

Images