CN112462146A - Method for detecting salt drops of electrode material resisting electrochemical migration insulation failure - Google Patents
Method for detecting salt drops of electrode material resisting electrochemical migration insulation failure Download PDFInfo
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- CN112462146A CN112462146A CN202011299515.8A CN202011299515A CN112462146A CN 112462146 A CN112462146 A CN 112462146A CN 202011299515 A CN202011299515 A CN 202011299515A CN 112462146 A CN112462146 A CN 112462146A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/08—Measuring resistance by measuring both voltage and current
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/2801—Testing of printed circuits, backplanes, motherboards, hybrid circuits or carriers for multichip packages [MCP]
- G01R31/281—Specific types of tests or tests for a specific type of fault, e.g. thermal mapping, shorts testing
- G01R31/2817—Environmental-, stress-, or burn-in tests
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Abstract
The invention provides a salt droplet detection method for resisting electrochemical migration insulation failure of an electrode material. Selecting 0.1-3 mmol/l NaCl or 0.1-0.8 mmol/lNa2SO4The solution is used for detecting the resistance of a plurality of electrode materials to electrochemical migration insulation failure under the pollution of soluble salt, and comprises the following steps: first, sample preparation. Cleaning and drying a sample; preparing NaCl or Na with a certain concentration2SO4And (3) solution. And II, preparing a test environment. The method comprises the following steps: sample access to the test system; the bias voltage and the measurement parameters are set. And thirdly, carrying out an experiment. The method comprises the following steps: starting a video recording; dripping liquid drops; starting an experimental system; the experiment was continued until 120s after the insulation resistance failure. And fourthly, processing and analyzing data. Carrying out morphology analysis on the failure phenomenon of the circuit board; extracting characteristic life time, carrying outAnd (4) judging the insulation failure resistance. The testing method provided by the invention is simple and efficient, and the experimental principle accords with the practical application condition.
Description
Technical Field
The application relates to the technical field of engineering materials, in particular to a salt drop detection method for resisting electrochemical migration insulation failure of an electrode material.
Background
The circuit board is an important component of the electronic equipment, and the reliability of the circuit board directly determines the reliability of the electronic equipment. The circuit board and the components packaged on the circuit board have various electrode material combinations, but with the development of a high-density circuit, the line spacing of the circuit is continuously reduced, and under the action of certain environmental temperature, humidity and bias voltage between electrodes, insulation failure based on an electrochemical migration mechanism is easy to occur between the electrode materials. Because the atmospheric environment pollution is serious, dust particles in the atmosphere enter the electronic product along with the air flow and are deposited on the surfaces of a circuit board and an electronic component, so that the electrochemical reaction between electrodes is intensified, the electrochemical migration of electrode materials is promoted, crystal branches are formed, and the short circuit fault between the electrodes is caused.
Studies have shown that room atmosphere naturally contains about 3% soluble salt content in the dust deposit, and that the coverage with salt-containing dust reduces the critical humidity of the circuit board surface, which makes it easier to condense a water film on the circuit board surface under low ambient humidity conditions. The soluble salt dissolved in the water film on the surface of the circuit board increases the ion concentration, reduces the surface insulation resistance, and accelerates the corrosion and dissolution of the anode material, thereby accelerating the electrochemical migration failure between the electrodes. The phenomenon of electrochemical migration between lines on the surface of the circuit board is remarkably aggravated by NaCl salt solution with a concentration of even 0.1 mmol/l. When the concentration of the NaCl solution is 0.1 mmol-3 mmol/l, the electrochemical migration failure between the electrodes of the silver-dipped circuit board is aggravated along with the increase of the concentration, and the failure time is reduced in a negative power function. Similar acceleration effects are also present for electrodes of other materials, such as SAC305 and pure tin electrodes. Except NaCl, Na2SO4Is also one of the main components of soluble salt in dust, and has been shown by research to be Na2SO4The solution also has an accelerating effect on the electrochemical migration of the alloy electrode. In the method for detecting the environmental reliability of the electronic product,salt spray experiments are used more often, and a 5% NaCl concentration causes severe corrosion of many metal materials. The research and test method for the electrochemical migration characteristic of the electrode material of the circuit board mostly adopts a temperature and humidity bias method and a water drop experiment method of pure water. The electrode materials of the circuit board and the packaging component thereof are various, and relate to various materials such as Au, Ag, Cu, Sn, Ni and the like, and at present, a detection technical scheme suitable for evaluating the resistance to electrochemical migration insulation failure of the electrode materials of the circuit board and the packaging component thereof in a soluble salt polluted environment does not exist.
In order to simulate the capacity of resisting electrochemical migration insulation failure of the electrode material of the circuit board under the pollution of soluble salt in dust, the detection method provided by the invention analyzes and designs the type and concentration range of the soluble salt and the application method.
In the aspect of selecting soluble salt species, the dust component of natural dust deposition in Beijing indoor is analyzed, and cations mainly comprise Ca2+，Na+，Mg2+，K+，NH4 +The anion mainly comprises NO3 -，Cl-，SO4 2-，F-Wherein Ca is2+，Na+And NO3 -，Cl-，SO4 2-The mass percentage of (A) is higher. Due to the NO content3 -Salts are always flammable and strongly corrosive, and therefore such salts are not used in the assay. CaSO4Is a slightly soluble salt and is not adopted. NaCl and Na2SO4Are two kinds of soluble salts which are common in natural dust components of the atmosphere, and therefore, the soluble salts are selected as representative substances of the soluble salts to be used as pollution sources on the surface of a circuit board.
In the aspect of selecting the concentration of soluble salt, according to the principle that the insulation failure mechanism of different electrode materials under different salt solution concentrations is electrochemical migration, the concentration of NaCl solution is selected to be 0.1-3 mmol/l, and Na is selected2SO4The concentration of the solution is 0.1-0.8 mmol/l. Higher salt concentrations can cause ionic conduction insulation failure of aqueous solutions between circuit board electrodes rather than electrochemical migration failure mechanisms.
For the simulation of adopting soluble salt with a certain concentration as an environmental pollution source, some methods adopt a method of directly throwing salt particles to a circuit board and then adopting temperature-humidity bias, the electrochemical migration failure time in the method is longer, usually in the order of magnitude of tens of hours, and the salt particle distribution is discrete, so that the electrochemical migration failure time has larger deviation; salt spray experiments are also directly adopted, but the electrode is seriously corroded due to too high NaCl concentration, and the insulation failure mechanism between the electrodes is changed. In the existing water drop experimental research which adopts NaCl solution, the salt solution is mainly used for driving electrochemical migration to generate, and the quantitative detection method of the components and different concentrations of the salt solution aiming at different electrode materials to resist the electrochemical migration insulation failure is not researched. In order to evaluate the resistance of a plurality of circuit board electrode materials to electrochemical migration insulation failure under the condition of soluble salt pollution, the method adopts a salt drop experiment method with proper concentration and components at room temperature, improves the repeated times of the experiment, eliminates abnormal values, and finally uses a Weibull model to fit the failure life of the circuit board so as to improve the effectiveness and consistency of the detection method.
Disclosure of Invention
1. In view of the above, the present invention provides a method for detecting salt droplets of an electrode material against electrochemical migration insulation failure, wherein the method selects NaCl or Na2SO4Solution for electrochemical migration mechanism based isolation between electrode materials of circuit board or electronic component packaged on circuit board in electronic product
Simulating and detecting edge failure, which comprises the following steps:
first, preparation of experimental sample
1) Taking 10 samples of the same material to be detected;
2) ultrasonically cleaning a tested circuit board or electronic element sample by deionized water with the resistivity of 18.2M omega for 30 minutes in an experiment, and drying for 12 hours in an environment of 40 +/-2 ℃;
second, preparation of experimental apparatus
1) Deionized water with the resistivity of 18.2 MOmega is used for configuring the concentration of 0.1 mmol/l-3 mmol/ll NaCl or 0.1 mmol/l-0.8 mmol/l Na2SO4A solution;
2) fixing a sample to be detected on a sample table and adjusting the center of a visual field;
3) connecting a probe of a picoammeter with two electrodes of a sample to be detected;
4) carry out the parameter setting of skin ampere meter surface insulation resistance test, include: measuring the insulation resistance of the surface between the electrodes at intervals of 1s and at a test voltage of 3-5V;
third, the experimental procedure
1) Opening an optical microscope camera above the sample table, focusing, and starting a video recording;
2) dripping NaCl or Na on a sample to be detected by using a liquid transfer device2SO4The solution is prepared, so that the salt solution drops completely cover the surfaces of two adjacent electrodes of the tested circuit board or circuit board element;
3) starting a skin ampere meter, applying a test voltage, testing the surface insulation resistance of the two electrodes, and simultaneously reading and storing test data of the insulation resistance of the skin ampere meter by using a computer;
4) observing corrosion between sample electrodes in real time through an optical microscope, and confirming generation of electrochemical migration crystal branches;
5) the experiment is continued until the surface insulation resistance between the two electrodes read by the picometer is reduced to 50k omega and then is finished for 120 s;
6) replacing the sample, installing the sample on a sample table, connecting a picometer, and repeating the experimental steps (1) - (5);
fourth, data processing
1) Drawing a curve of the surface insulation resistance between the two electrodes along with the change of time by using the stored surface insulation resistance data, and taking the time from starting a picometer until the surface insulation resistance is reduced to 50k omega as failure time;
2) repeating the experiment for 10 times on the same model sample, removing abnormal data according to a 3 sigma criterion, and taking the Weibull characteristic value of the failure time as the service life of the sample under the experimental condition;
3) comparing the resistance of different sample electrode materials to electrochemical migration insulation failure by using the service life of the sample, wherein the longer the service life is, the stronger the resistance of the material to electrochemical migration insulation failure is.
2. The inspection method according to claim 1, wherein the inspection method is applied to different materials of the circuit board or electrodes of the electronic components packaged on the circuit board.
The invention has the advantages that:
1) the detection method provided by the invention is simple and rapid;
2) the detection method provided by the invention has reasonable research basis for the type and concentration of the adopted salt solution, and can realize accelerated simulation of surface insulation failure between the circuit board and the encapsulated element electrode thereof under soluble salt pollution based on an electrochemical migration mechanism;
3) the detection method provided by the invention improves the reliability of the experimental result by monitoring the surface insulation resistance change between the electrodes of the circuit board on line and observing the growth of the electrochemical migration crystal branches between the electrodes in real time;
4) the detection method provided by the invention takes the average failure time obtained by monitoring the surface insulation resistance failure between the electrodes as an evaluation index, evaluates the capability of the sample electrode material in resisting the electrochemical migration insulation failure, and has better discrimination;
5) the invention is suitable for evaluating the capacity of resisting electrochemical migration insulation failure of various electrode materials, and is suitable for
The application range is wide.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a sample of a Y-shaped circuit board;
FIG. 2 is a block diagram of a salt droplet experiment testing system;
FIG. 3 is a diagram showing the electrochemical migration product morphology of a 0.1mmol/l NaCl liquid drop Y-shaped silver-dipped circuit board;
FIG. 4 is a graph showing the degradation of the insulation resistance between electrodes of a sample on a circuit board in a 0.1mmol/l NaCl droplet experiment;
FIG. 5 is the appearance of electrochemical migration products of a 3mmol/L NaCl liquid drop Y-shaped silver-dipped circuit board;
FIG. 6 is a degradation curve of the surface insulation resistance between electrodes of a sample of a silver-dipped circuit board in a 3mmol/l NaCl droplet experiment;
FIG. 7 shows 0.1mmol/l Na2SO4The appearance of the electrochemical migration product of the liquid drop Y-shaped silver-dipped circuit board;
FIG. 8 shows 0.1mmol/l Na2SO4The surface insulation resistance between electrodes of a circuit board sample in a liquid drop experiment is represented by a degradation curve;
FIG. 9 shows 0.8mmol/l Na2SO4The appearance of the electrochemical migration product of the liquid drop Y-shaped silver-dipped circuit board;
FIG. 10 shows 0.8mmol/l Na2SO4The degradation curve of the surface insulation resistance between electrodes of a sample of the silver-dipped circuit board in a liquid drop experiment;
FIG. 11 is a diagram of the electrochemical migration product morphology of a 0.1mmol/l NaCl droplet Y-type bare copper circuit board;
FIG. 12 is a graph showing the degradation of insulation resistance between electrodes of a bare copper circuit board sample in a 0.1mmol/l NaCl droplet experiment;
FIG. 13 is a diagram of the morphology of electrochemical migration products of a 3mmol/L NaCl droplet Y-type bare copper circuit board;
FIG. 14 is a graph showing the degradation of insulation resistance between electrodes of a bare copper circuit board sample in a 3mmol/l NaCl droplet experiment;
FIG. 15 shows 0.1mmol/l Na2SO4The appearance of the electrochemical migration product of the liquid drop Y-shaped bare copper circuit board;
FIG. 16 is 0.1mmol/l Na2SO4The surface insulation resistance between electrodes of a sample of the bare copper circuit board is degraded in a liquid drop experiment;
FIG. 17 shows 0.8mmol/l Na2SO4The appearance of the electrochemical migration product of the liquid drop Y-shaped bare copper circuit board;
FIG. 18 is 0.8mmol/l Na2SO4Surface insulation resistance between electrodes of sample of bare copper circuit board in liquid drop experimentA degradation curve.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The samples of the embodiments of the invention generally described and illustrated in the drawings herein can be designed in a variety of different materials and salt solutions. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The invention comprises the following steps:
first, preparation of experimental sample
1) Selecting a Y-shaped circuit board for illustration, wherein as shown in FIG. 1, the electrode materials are silver-dipped and bare copper, and the number of samples of each material is 40 respectively;
2) ultrasonically cleaning a circuit board sample to be tested by deionized water with the resistivity of 18.2M omega for 30 minutes, and drying for 12 hours in an environment of 40 +/-2 ℃. The step is to remove the pollutants in the processing, residual, transportation and storage processes of the circuit board and ensure the accuracy of the detection result.
Second, preparation of experimental apparatus
1) Preparing NaCl solution with concentration of 0.1mmol/l and 3mmol/l and Na solution with concentration of 0.1mmol/l and 0.8mmol/l with deionized water with resistivity of 18.2M omega2SO4A solution;
2) fixing a sample on a sample stage, observing from an optical microscope and simultaneously adjusting the position of the sample to be placed at the center of the visual field, as shown in FIG. 2;
3) connecting a probe of a picoammeter with two electrodes of a sample to be detected;
4) starting a Pear meter measuring software, setting the interval time of measuring the surface insulation resistance between the electrodes to be 1s and the test voltage to be 3V, wherein the voltage can drive the electrochemical migration between the electrodes and can not accelerate the electrochemical migration too fast to reduce the discrimination of the failure time of different electrode materials;
third, the experimental procedure
1) Opening an optical microscope camera above the sample table, focusing, and starting a video recording;
2) dripping 2 mul of 0.1mmol/l NaCl solution on the circuit board to be detected by using a liquid transfer machine to completely cover the two poles of the Y-shaped circuit board;
3) starting a skin ampere meter, applying a test voltage, testing the surface insulation resistance of the two electrodes, and simultaneously reading and storing test data of the insulation resistance of the skin ampere meter by using a computer;
4) observing corrosion between sample electrodes in real time through an optical microscope, and confirming generation of electrochemical migration crystal branches until the crystal branches are connected with the two electrodes;
5) the experiment is continued until the skin ampere meter shows that the surface insulation resistance between the two electrodes is reduced to 50k omega, then the experiment is kept for 120s, the output voltage of the skin ampere meter is closed, and the experiment is ended;
6) replacing the sample, installing the sample on a sample table, connecting a picometer, and repeating the experimental steps (1) - (5);
fourth, data processing
1) Drawing a curve of the surface insulation resistance between the two electrodes along with the change of time by using the stored surface insulation resistance data, and taking the time from starting the picoammeter until the surface insulation resistance is reduced to 50k omega as failure time;
2) repeating the experiment for 10 times on the same model sample, removing abnormal data according to a 3 sigma criterion, and taking the Weibull characteristic value of the failure time as the service life of the sample under the experimental condition;
3) comparing the resistance of different sample electrode materials to electrochemical migration insulation failure by using the service life of the sample, wherein the longer the service life is, the stronger the resistance of the material to electrochemical migration insulation failure is.
Fifth, experimental results
FIG. 3 shows the morphology of dendrites formed by electrochemical migration of a Y-type silver-impregnated circuit board under the pollution of 2 μ l of 0.1mmol/l NaCl drops, which proves that electrochemical migration does occur between parallel electrodes of the circuit board, anode metal loses electrons and is oxidized to form metal cations, the metal cations move to a cathode by taking salt drops as a medium under the action of an electric field, the electrons are reduced to metal atoms, the subsequent metal cations continuously move to the cathode, and the dendrites are generated by reduction on the reduced atoms until an inter-electrode short circuit is formed and the surface insulation resistance fails.
FIG. 4 is a degradation curve of the insulation resistance of the surface of the electrodes of the Y-shaped silver-dipped circuit board under the pollution of 0.1mmol/l NaCl liquid drops, in a salt liquid drop experiment, the insulation resistance of the surface of the circuit board is greatly reduced after crystal branches are formed between the electrodes, and is finally stabilized below 50k omega, namely electrochemical migration insulation failure occurs, and the failure time is 141 s.
FIG. 5 shows the morphology of dendrites formed by electrochemical migration of a Y-shaped silver-dipped circuit board under the pollution of 2 mul of 3mmol/l NaCl liquid drops, and as the concentration of the liquid drops is increased, the electrochemical migration reaction is more severe, and the generated dendrites become coarse but the number is reduced.
FIG. 6 is a degradation curve of the insulation resistance of the surface between the electrodes of the Y-shaped silver-dipped circuit board under the pollution of 3mmol/l NaCl liquid drops, and the failure time is obviously shortened to 26 s.
TABLE 10.1 and 3mmol/l NaCl drop contamination of the failure time of the Y-type silver-impregnated circuit boards
Note: removing abnormal data according to 3 sigma criterion
Along with the increase of the concentration of NaCl solution, the morphology of crystal branches can be obviously changed, the trunk becomes coarse, but the number of the trunk is reduced, the generation speed becomes fast, and the failure time is shortened.
FIG. 7 shows the thickness of the Y-type silver-dipped circuit board at 2. mu.l of 0.1mmol/l Na2SO4The crystal branches are in the shape of crystal branches formed by electrochemical migration under the pollution of liquid drops, and the speed of the crystal branches generated by the electrochemical migration reaction is higher than that of NaCl solution.
FIG. 8 shows the ratio of 0.1mmol/l Na of the Y-type silver-dipped circuit board2SO4The liquid drops pollute the degradation curve of the insulation resistance on the surface between the electrodes, and the failure time is shortened to 91 s.
FIG. 9 shows the Y-type circuit board at 2. mu.l of 0.8mmol/l Na2SO4The shape of the crystal branches formed by electrochemical migration under the pollution of the liquid drops is more violent along with the increase of the concentration of the liquid drops, and the generated crystal branches become thicker but the number of the crystal branches is reduced.
FIG. 10 shows a Y-type silver-dipped circuit board at 0.8mmol/l Na2SO4The liquid drop pollutes the degradation curve of the insulation resistance on the surface between the electrodes, and the failure time is obviously shortened to 10 s.
TABLE 20.1 and 0.8mmol/l Na2SO4Failure time of Y-type silver-dipped circuit board under liquid drop pollution
Note: removing abnormal data according to 3 sigma criterion
Along with Na2SO4The concentration of the solution is increased, the change trend of the crystal branch morphology and the failure time is the same as that of NaCl liquid drops under pollution, and the change trend of electrochemical migration products and failure time obtained by changing the types and the concentrations of the pollution liquid drops and carrying out experiments is the same when the plating material is unchanged, so that the detection method is suitable for the detection condition of pollution of different salt solutions.
FIG. 11 shows the morphology of dendrites formed by electrochemical migration of a Y-type bare copper circuit board under the contamination of 2 μ l of 0.1mmol/l NaCl liquid drops.
FIG. 12 is a graph showing the deterioration curve of the insulation resistance of the surface between the electrodes of the Y-type bare copper circuit board, which shows the same tendency as that of the immersion silver sample, but shows a prolonged failure time of 276 s.
FIG. 13 shows the morphology of dendrites formed by electrochemical migration of a Y-type bare copper circuit board under the contamination of 2 μ l of 3mmol/l NaCl drops.
FIG. 14 is a graph showing the deterioration curve of the insulation resistance of the surface between the electrodes of the Y-type bare copper circuit board, which shows the same change tendency as that of the immersion silver sample, but shows a long failure time of 127 seconds.
TABLE 30.1 and 3mmol/l NaCl drop contamination of the failure time of Y-type bare copper circuit boards
Note: removing abnormal data according to 3 sigma criterion
It can be seen that under the same pollution condition, even if the surface materials of the circuit board are different, the variation trend of the crystal branch morphology and the insulation resistance is consistent.
FIG. 15 shows a Y-type bare copper circuit board at 2. mu.l of 0.1mmol/l Na2SO4The appearance of crystal branches formed by electrochemical migration under the pollution of liquid drops.
FIG. 16 is a graph showing the deterioration of the insulation resistance of the surface between the electrodes of the Y-type bare copper circuit board, and the failure time is 161 s.
FIG. 17 shows the thickness of the Y-type bare copper circuit board at 2. mu.l of 0.8mmol/l Na2SO4The appearance of crystal branches formed by electrochemical migration under the pollution of liquid drops.
FIG. 18 is a graph showing the deterioration of the insulation resistance of the surface between the electrodes of the Y-type bare copper circuit board, and the failure time was 91 seconds.
TABLE 40.1 and 0.8mmol/l Na2SO4Failure time of Y-shaped bare copper circuit board under liquid drop pollution
Note: removing abnormal data according to 3 sigma criterion
The Y-shaped silver-dipped and bare copper circuit board is respectively filled with NaCl and Na with different concentrations2SO4The experimental results in the drops demonstrate that the silver-impregnated circuit boards are less resistant to electrochemical migration insulation failure than bare copper circuit boards. Under the condition that the types and concentration ranges of the solutions are proper, the method is suitable for detecting the electrochemical migration resistance insulation failure of circuit boards with different coating materials.
The principle of the detection of the insulation failure of the surface of the circuit board is as follows:
the experimental sample is a silver-dipped Y-shaped circuit board, the distance between parallel wires is 0.64mm, the thickness of a silver coating on the surface is 0.15m, the base metal is copper, and the thickness is 50 m. Under the condition of certain temperature and relative humidity, anions in the salt liquid drops destroy an oxide film of the anode metal, promote the oxidation of the anode metal, form anode metal ions, influence the degree and the characteristics of electrochemical migration on the surface of the circuit board, and cause insulation failure between circuit boards.
In order to accelerate the simulation of the effect of soluble salt on the insulation failure of the circuit board under the actual condition, NaCl and Na which are main components in dust soluble salt are selected2SO4As representatives of dust-soluble salts, by controlling NaCl and Na2SO4The solution concentration acts to accelerate electrochemical corrosion of the electrode material to promote the formation of electrochemical migration. However, the salt solution concentration is too high, which leads to ion conduction between electrodes and changes electrochemical migration to cause insulation failure mechanism, so that reasonable salt solution concentration selection is very critical.
The detection of the surface insulation resistance and the electrochemical migration product of the circuit board is an important index for judging the insulation performance degradation and failure mechanism of the circuit board. The failure life of the circuit board and the appearance detection of the electrochemical migration reaction product are obtained through the online monitoring of the surface insulation resistance of the circuit board, and a basis is provided for the final evaluation of the insulation failure of the circuit board.
The invention provides a simulation detection method for insulation failure of a salt droplet polluted circuit board based on electrochemical migration, wherein NaCl and Na are selected in the scheme2SO4The solution is representative of a soluble salt, which is observed for its ability to electrochemically migrate the circuit board. Under the action of the electric field, the anions in the solution move to the anode directionally. The metal of the anode of the circuit board is subjected to electrochemical corrosion in an anion-enriched environment, and finally the metal of the anode of the circuit board is ionized, moves to the cathode in a solution film layer under the drive of an electric field, and is reduced into metal atoms to form crystal branches, so that the reduction of the insulation resistance between the electrodes and even the short circuit are caused, and the phenomenon is electrochemical migration. The simulation detection method provided by the invention conforms to the actual electrochemical migration mechanism between the electrodes of the circuit board and the packaging element thereof, simulates the effect of soluble salt on the insulation failure between the electrodes, meets the requirement of accelerated experiment, and can be used for detecting and evaluating the insulation failure between the electrodes based on the electrochemical migration mechanism. And NaCl and Na2SO4The anions in the solution can chemically react with electrode materials (Ag, Cu, Ni, Sn, Pb, etc.) of a common circuit board and a packaging element thereof, so that the oxidation of the anode material is accelerated, and the electrochemical migration of metal ions is promoted to form. Therefore, the detection method of the invention is suitable for different materials of the circuit board or the electrodes of the electronic elements packaged on the circuit board.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (2)
1. A method for detecting the salt drops of electrode material against electrochemical migration and insulation failure includes such steps as choosing NaCl or Na2SO4The solution is used for simulating and detecting the insulation failure based on an electrochemical migration mechanism between electrode materials of a circuit board or an electronic element packaged on the circuit board in an electronic product, and the specific steps comprise:
first, preparation of experimental sample
1) Taking 10 samples of the same material to be detected;
2) ultrasonically cleaning a tested circuit board or electronic element sample by deionized water with the resistivity of 18.2M omega for 30 minutes in an experiment, and drying for 12 hours in an environment of 40 +/-2 ℃;
second, preparation of experimental apparatus
1) Preparing NaCl with the concentration of 0.1 to 3mmol/l or Na with the concentration of 0.1 to 0.8mmol/l by deionized water with the resistivity of 18.2M omega2SO4A solution;
2) fixing a sample to be detected on a sample table and adjusting the center of a visual field;
3) connecting a probe of a picoammeter with two electrodes of a sample to be detected;
4) carry out the parameter setting of skin ampere meter surface insulation resistance test, include: measuring the insulation resistance of the surface between the electrodes at intervals of 1s and at a test voltage of 3-5V;
third, the experimental procedure
1) Opening an optical microscope camera above the sample table, focusing, and starting a video recording;
2) dripping NaCl or Na on a sample to be detected by using a liquid transfer device2SO4The solution is prepared, so that the salt solution drops completely cover the surfaces of two adjacent electrodes of the tested circuit board or circuit board element;
3) starting a skin ampere meter, applying a test voltage, testing the surface insulation resistance of the two electrodes, and simultaneously reading and storing test data of the insulation resistance of the skin ampere meter by using a computer;
4) observing corrosion between sample electrodes in real time through an optical microscope, and confirming generation of electrochemical migration crystal branches;
5) the experiment is continued until the surface insulation resistance between the two electrodes read by the picometer is reduced to 50k omega and then is finished for 120 s;
6) replacing the sample, installing the sample on a sample table, connecting a picometer, and repeating the experimental steps (1) - (5);
fourth, data processing
1) Drawing a curve of the surface insulation resistance between the two electrodes along with the change of time by using the stored surface insulation resistance data, and taking the time from starting a picometer until the surface insulation resistance is reduced to 50k omega as failure time;
2) repeating the experiment for 10 times on the same model sample, removing abnormal data according to a 3 sigma criterion, and taking the Weibull characteristic value of the failure time as the service life of the sample under the experimental condition;
3) comparing the resistance of different sample electrode materials to electrochemical migration insulation failure by using the service life of the sample, wherein the longer the service life is, the stronger the resistance of the material to electrochemical migration insulation failure is.
2. The inspection method according to claim 1, wherein the inspection method is applied to different materials of the circuit board or electrodes of the electronic components packaged on the circuit board.
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| CN113533361A (en) * | 2021-06-25 | 2021-10-22 | 万向一二三股份公司 | Visual characterization method for insulation failure of lithium ion battery |
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| CN113358809A (en) * | 2021-06-09 | 2021-09-07 | 北京科技大学 | Method for determining soluble anions of pollutants on surface of material and application of method |
| CN113533361A (en) * | 2021-06-25 | 2021-10-22 | 万向一二三股份公司 | Visual characterization method for insulation failure of lithium ion battery |
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