CN116381342A - Method for detecting copper migration of inner layer of flexible circuit board - Google Patents
Method for detecting copper migration of inner layer of flexible circuit board Download PDFInfo
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- CN116381342A CN116381342A CN202310254394.2A CN202310254394A CN116381342A CN 116381342 A CN116381342 A CN 116381342A CN 202310254394 A CN202310254394 A CN 202310254394A CN 116381342 A CN116381342 A CN 116381342A
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- circuit board
- flexible circuit
- leakage failure
- resistance value
- internal leakage
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 65
- 239000010949 copper Substances 0.000 title claims abstract description 62
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 62
- 238000013508 migration Methods 0.000 title claims abstract description 40
- 230000005012 migration Effects 0.000 title claims abstract description 40
- 238000000034 method Methods 0.000 title claims abstract description 35
- 210000001787 dendrite Anatomy 0.000 claims abstract description 37
- 238000012360 testing method Methods 0.000 claims abstract description 37
- 238000012545 processing Methods 0.000 claims abstract description 10
- 238000009413 insulation Methods 0.000 claims description 54
- 238000005260 corrosion Methods 0.000 claims description 13
- 230000007797 corrosion Effects 0.000 claims description 13
- 239000003344 environmental pollutant Substances 0.000 claims description 11
- 238000005259 measurement Methods 0.000 claims description 11
- 231100000719 pollutant Toxicity 0.000 claims description 11
- 238000001931 thermography Methods 0.000 claims description 9
- 230000009467 reduction Effects 0.000 claims description 4
- 230000000694 effects Effects 0.000 claims description 3
- 239000003292 glue Substances 0.000 claims description 3
- 238000005498 polishing Methods 0.000 claims description 3
- 239000011347 resin Substances 0.000 claims description 3
- 229920005989 resin Polymers 0.000 claims description 3
- 239000000463 material Substances 0.000 abstract description 16
- 230000008569 process Effects 0.000 abstract description 9
- 230000006872 improvement Effects 0.000 abstract description 8
- 239000010410 layer Substances 0.000 description 21
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 19
- 229910001431 copper ion Inorganic materials 0.000 description 18
- 238000010586 diagram Methods 0.000 description 11
- 239000004642 Polyimide Substances 0.000 description 6
- 239000011295 pitch Substances 0.000 description 6
- 229920001721 polyimide Polymers 0.000 description 6
- 238000001514 detection method Methods 0.000 description 5
- 239000000853 adhesive Substances 0.000 description 4
- 230000001070 adhesive effect Effects 0.000 description 4
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 3
- 239000011889 copper foil Substances 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000012790 adhesive layer Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 230000005284 excitation Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
Images
Classifications
-
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
-
- 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
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0266—Marks, test patterns or identification means
- H05K1/0268—Marks, test patterns or identification means for electrical inspection or testing
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/16—Inspection; Monitoring; Aligning
Abstract
The invention discloses a method for detecting copper migration of an inner layer of a flexible circuit board, which comprises the following steps: judging whether a test line in the flexible circuit board has internal leakage failure or not under the preset working condition, wherein the test line is an adjacent and insulated tested wire on each layer of line of the flexible circuit board, and each tested wire is connected with a surface line and an inner layer line through a via hole; if the flexible circuit board has internal leakage failure, slicing the flexible circuit board; obtaining the appearance of the flexible circuit board after slicing treatment; copper dendrites exist in the flexible circuit board, and it is determined that copper migration phenomenon exists in the flexible circuit board, so that internal leakage failure exists in the flexible circuit board. The invention can improve the accuracy of detecting the leakage failure in the flexible circuit board and provide scientific basis for risk avoidance, material selection and processing process improvement.
Description
Technical Field
The invention relates to the technical field of flexible circuit boards, in particular to a method for detecting copper migration of an inner layer of a flexible circuit board.
Background
Flexible circuit (Flexible Printed Circuit, FPC) boards are increasingly used in the fields of mobile phone motherboards, camera modules, intelligent wearable devices, and the like, due to the advantages of thin thickness, small volume, light weight, flexibility, and the like. There are two types of adhesives used in FPC boards: acrylic and epoxy resins. Acrylic acid has good heat resistance and high bonding strength, and is widely used, but has certain hygroscopicity, the bonding performance of the acrylic acid is reduced under a damp-heat environment, and cracks or gaps are easy to appear in a bonding interface or a bonding material, so that a channel is provided for copper ion migration. Therefore, the leakage caused by the inner layer copper migration of the FPC multilayer board is one of typical failure modes of the FPC multilayer board, and the failure is obvious after a period of use due to the fact that the leakage belongs to the loss type failure, and once the failure loss is large, the inner layer copper migration detection and evaluation of the board is very critical before the product leaves a factory and even before the board is used in batches.
At present, a detection method for a circuit board based on a copper migration mechanism in the industry mainly aims at a rigid printed board, and a detection method for copper migration of an inner layer of an FPC (flexible printed circuit) multilayer board lacks relevant standard guidance at present, and related use or manufacturing enterprises only refer to an excitation method of the rigid printed board for ion migration, so that whether electricity leakage occurs or not is judged through monitoring of insulation resistance, but inaccuracy in detection can be caused due to the stacking feature of the FPC multilayer board.
Disclosure of Invention
The invention provides a method for detecting copper migration of an inner layer of a flexible circuit board, which can improve the accuracy of detecting leakage failure in the flexible circuit board and provides scientific basis for risk avoidance, material selection and processing process improvement.
According to one aspect of the invention, there is provided a method for detecting copper migration in an inner layer of a flexible circuit board, comprising:
judging whether a test line in the flexible circuit board has internal leakage failure or not under the preset working condition, wherein the test line is an adjacent and insulated tested wire on each layer of line of the flexible circuit board, and each tested wire is connected with a surface line and an inner layer line through a via hole;
if the flexible circuit board has internal leakage failure, slicing the flexible circuit board;
obtaining the appearance of the flexible circuit board after slicing treatment;
copper dendrites exist in the flexible circuit board, and it is determined that copper migration phenomenon exists in the flexible circuit board, so that internal leakage failure exists in the flexible circuit board.
Optionally, the flexible circuit board is under a preset working condition, and determining whether the test circuit in the flexible circuit board has an internal leakage failure includes:
acquiring the resistance value of the insulation resistance between the test lines at intervals of preset time;
judging whether the flexible circuit board has internal leakage failure according to the reduction condition of the resistance value of the insulation resistor.
Optionally, determining whether the flexible circuit board has an internal leakage failure according to a decrease of a resistance value of the insulation resistor includes:
the resistance value of the insulation resistor is reduced to be smaller than a first preset resistance value, and the leakage failure of the flexible circuit board is determined;
and if the surface of the flexible circuit board has no leakage failure, determining that the flexible circuit board has internal leakage failure.
Optionally, determining whether the flexible circuit board has an internal leakage failure according to a decrease of a resistance value of the insulation resistor includes:
the resistance value of the insulation resistor is reduced to be smaller than a first preset resistance value, and the leakage failure of the flexible circuit board is determined;
if at least one of copper dendrites, pollutants and corrosion products exist on the surface of the flexible circuit board, determining that the flexible circuit board has surface leakage failure;
eliminating the influence of surface leakage failure on the resistance value of the insulation resistance of the flexible circuit board;
and acquiring the resistance value of the insulation resistor after the surface of the flexible circuit board is treated, and if the resistance value of the insulation resistor is smaller than a second preset resistance value, determining that the electric leakage inside the flexible circuit board fails, wherein the second preset resistance value is smaller than the first preset resistance value.
Optionally, removing the resistive effect of the surface leakage failure on the insulation resistance of the flexible circuit board includes:
the surface of the flexible circuit board is treated to remove at least one of copper dendrites, contaminants, and corrosion products.
Optionally, if the flexible circuit board has an internal leakage failure, before slicing the flexible circuit board, the method further includes:
and determining the position of the leakage failure in the flexible circuit board.
Optionally, determining the location of the electrical leakage failure within the flexible circuit board includes:
and determining the position of the leakage failure in the flexible circuit board through a microscopic infrared thermal imaging system.
Optionally, if the flexible circuit board has an internal leakage failure, slicing the flexible circuit board includes:
obtaining a measurement sample of a flexible circuit board cut into a preset size;
encapsulating and curing the measurement sample by using resin glue;
and (3) polishing the measurement sample along the direction parallel to the surface of the flexible circuit board.
Optionally, obtaining the morphology of the flexible circuit board after slicing treatment includes:
and observing the appearance of the flexible circuit board after slicing by a metallographic microscope to obtain the appearance of the flexible circuit board after slicing.
Optionally, the flexible circuit board is under a preset working condition comprising:
the working voltage is less than or equal to 100V;
the preset temperature and humidity conditions comprise any one of 85 ℃ temperature, 85% RH humidity, 40 ℃ temperature, 93% RH humidity, 65 ℃ temperature, 88% RH humidity, 60 ℃ temperature and 90% RH humidity;
the preset time includes any one of 2 hours, 1 hour, 0.5 hours, 10 minutes, and 1 minute.
According to the technical scheme, the flexible circuit board is subjected to slicing treatment under the preset working condition if the flexible circuit board has internal leakage failure; obtaining the appearance of the flexible circuit board after slicing treatment; copper dendrites exist in the flexible circuit board, and it is determined that copper migration phenomenon exists in the flexible circuit board, so that internal leakage failure exists in the flexible circuit board. According to the technical scheme provided by the embodiment of the invention, after the internal leakage failure of the flexible circuit board is initially determined, the copper migration phenomenon in the flexible circuit board is further determined through the copper dendrite morphology in the flexible circuit board, so that the internal leakage failure of the flexible circuit board is caused, the accuracy of detecting the internal leakage failure of the flexible circuit board is improved, and therefore, unqualified products caused by copper ion migration are screened out in advance according to the determined leakage failure type, and scientific basis is provided for flexible circuit board risk avoidance, material selection and processing process improvement.
It should be understood that the description in this section is not intended to identify key or critical features of the embodiments of the invention or to delineate the scope of the invention. Other features of the present invention will become apparent from the description that follows.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a flexible circuit board multilayer board according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for detecting copper migration in an inner layer of a flexible circuit board according to an embodiment of the present invention;
FIG. 3 is a detailed flow chart of step 110 of FIG. 2;
FIG. 4 is a flow chart included in step 112 of FIG. 3;
FIG. 5 is a further flowchart included in step 112 of FIG. 3;
fig. 6 is an internal schematic view of a flexible circuit board according to an embodiment of the present invention;
FIG. 7 is a schematic view of the inside of a flexible circuit board according to another embodiment of the present invention;
FIG. 8 is a detailed flow chart of step 120 of FIG. 2;
FIG. 9 is a schematic view of a copper dendrite provided by an embodiment of the present invention;
FIG. 10 is a schematic view of yet another copper dendrite provided by an embodiment of the present invention;
FIG. 11 is a failure circuit diagram of an insulation resistor according to an embodiment of the present invention;
FIG. 12 is a schematic diagram of a location of an internal leakage failure according to an embodiment of the present invention;
fig. 13 is a schematic view of yet another copper dendrite provided by an embodiment of the present invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Fig. 1 is a schematic structural diagram of a flexible circuit board multilayer board according to an embodiment of the present invention, wherein the material of the flexible circuit board multilayer board includes polyimide, copper and an adhesive, the polyimide is an insulating material and a protective film, the copper is a conductive material, and the adhesive is an adhesive material for connecting the polyimide layer and the copper foil.
Referring to fig. 1, the flexible wiring board multilayer board includes an inner layer flexible board including a first flexible insulating board and a second flexible insulating board each including a polyimide layer 10 and an adhesive layer 30 on upper and lower surfaces of the polyimide layer 10, and an outer layer flexible board. The outer flex includes a polyimide layer 10 and an adhesive layer 30. The test circuit comprises a first tested circuit and a second tested circuit, the first tested circuit comprises copper foils 20 positioned on the upper surface and the lower surface of the first flexible insulating plate and the second flexible insulating plate and connected through conductive through holes, and the second tested circuit comprises copper foils 20 positioned on the upper surface and the lower surface of the first flexible insulating plate and the second flexible insulating plate and connected through conductive through holes.
The embodiment of the invention provides a method for detecting copper migration of an inner layer of a flexible circuit board, and fig. 2 is a flowchart of the method for detecting copper migration of the inner layer of the flexible circuit board, and referring to fig. 2, the method comprises the following steps:
If a test voltage is applied to the test circuit under a preset working condition, the test voltage range can be 45VDC-100VDC, and the first tested circuit and the second tested circuit can generate internal leakage failure of the flexible circuit board, wherein the internal leakage failure is a manufacturing process problem in the flexible circuit board or a void, a crack or a gap exists in a bonding material; while adjacent and mutually insulated wires to be tested, which are not shown in fig. 1, may appear on the surface of the flexible circuit board, the surface leakage failure may be copper ion residue, the presence of pollutants, corrosion products, etc. on the surface of the flexible circuit board. By observing and excluding the leakage failure caused by the surface of the flexible circuit board, it can be determined whether the test circuit in the flexible circuit board has internal leakage failure.
Specifically, the preset working conditions include: the working voltage is less than or equal to 100V, the preset temperature and humidity conditions comprise that the temperature is 85 ℃, the humidity is 85%RH, the temperature is 40 ℃, the humidity is 93%RH, the temperature is 65 ℃, the humidity is 88%RH, the temperature is 60 ℃ and the humidity is 90%RH, copper dendrites appear on the surface or the inside of a flexible circuit board through excitation of copper ion migration of a tested wire under the preset working conditions, so that whether the test wire in the flexible circuit board has leakage failure is judged, and whether the test wire in the flexible circuit board has internal leakage failure can be judged through further testing, and by way of example, whether the flexible circuit board has internal leakage failure is judged through observing the reduction condition of insulation resistance of the tested wire or observing the appearance of the surface of the flexible circuit board.
And 120, if the flexible circuit board has internal leakage failure, slicing the flexible circuit board.
If the flexible circuit board has internal leakage failure, the flexible circuit board can be transversely sliced in parallel with the board surface direction, and the appearance of the internal leakage failure position can be accurately observed through slicing.
And 130, obtaining the appearance of the flexible circuit board after slicing.
The appearance of the sliced flexible circuit board after being processed can be observed through a stereo microscope or a metallographic microscope, obvious copper dendrite growth occurs, so that the fact that the inner layer of the flexible circuit board has copper migration phenomenon and further causes internal leakage failure of the flexible circuit board is determined, the appearance of the sliced flexible circuit board after being processed is not obtained in the prior art, therefore, the specific cause of the internal leakage failure of the flexible circuit board cannot be determined, the detection accuracy is reduced, and scientific basis cannot be provided for material selection and processing process improvement.
And 140, determining that copper dendrites exist in the flexible circuit board, and further causing internal leakage failure of the flexible circuit board due to copper migration phenomenon in the flexible circuit board.
If the growth of copper dendrites in the flexible circuit board is observed, it can be shown that the bonding material in the flexible circuit board has certain hygroscopicity under the preset working condition, the bonding performance of the bonding material is reduced under the damp-heat environment, and cracks or gaps exist in the bonding interface or the bonding material, so that a channel is provided for copper ion migration, and copper ion generates copper migration phenomenon, so that the inner leakage failure of the flexible circuit board is caused. Through confirm electric leakage failure type according to the inside electric leakage phenomenon of flexible circuit board, can avoid panel emergence electric leakage risk when putting into use, also can further confirm whether the material selection type is suitable simultaneously, whether processing procedure needs the improvement.
According to the technical scheme, the flexible circuit board is subjected to slicing treatment under the preset working condition if the flexible circuit board has internal leakage failure; obtaining the appearance of the flexible circuit board after slicing treatment; copper dendrites exist in the flexible circuit board, and it is determined that copper migration phenomenon exists in the flexible circuit board, so that internal leakage failure exists in the flexible circuit board. According to the technical scheme provided by the embodiment of the invention, after the internal leakage failure of the flexible circuit board is initially determined, the copper migration phenomenon in the flexible circuit board is further determined through the copper dendrite morphology in the flexible circuit board, so that the internal leakage failure of the flexible circuit board is caused, the accuracy of detecting the internal leakage failure of the flexible circuit board is improved, and therefore, unqualified products caused by copper ion migration are screened out in advance according to the determined leakage failure type, and scientific basis is provided for flexible circuit board risk avoidance, material selection and processing process improvement.
Optionally, fig. 3 is a detailed flowchart of step 110 in fig. 2, referring to fig. 3, where step 110 includes, when the flexible circuit board is in a preset working condition, determining whether an internal leakage failure exists in a test circuit in the flexible circuit board:
The preset time includes any one of 2 hours, 1 hour, 0.5 hour, 10 minutes, and 1 minute, and the resistance value of the insulation resistance between the test lines may be measured every 1 minute, for example. The insulation resistance values between the test lines at preset intervals are obtained, so that after the flexible circuit board is stored for a period of time under preset working conditions, whether the insulation resistance values are reduced or not is monitored, and whether the flexible circuit board has internal leakage failure or not is judged, and the preset time in the embodiment of the invention is described in detail in the following figure 11.
And 112, judging whether the flexible circuit board has internal leakage failure according to the reduction condition of the resistance value of the insulation resistor.
The flexible circuit board is under a preset working condition, has certain hygroscopicity after a period of time, has reduced bonding performance in a wet and hot environment, is easy to generate cracks or gaps in a bonding interface or a bonding material, so that a channel is provided for copper ion migration, if the resistance value of an insulation resistor is reduced to a certain extent, the condition that short circuits occur between test lines due to copper ion migration is proved, and the flexible circuit board can be judged to have leakage failure.
Optionally, fig. 4 is a flowchart included in step 112 in fig. 3, referring to fig. 4, step 112 includes, according to a decrease of a resistance value of the insulation resistor, determining whether an internal leakage failure exists in the flexible circuit board:
and 1120, reducing the resistance value of the insulation resistor to be smaller than a preset resistance value, and determining the leakage failure of the flexible circuit board.
When the preset resistance value is 100MΩ and the resistance value of the insulation resistor is reduced to be smaller than 100MΩ, the condition that short circuit occurs between test lines due to copper ion migration is proved, and the flexible circuit board is determined to have leakage failure.
And 1121, if no leakage failure exists on the surface of the flexible circuit board, determining that the internal leakage failure of the flexible circuit board exists.
The surface leakage failure may be caused by at least one of copper dendrites, pollutants and corrosion products, and if the surface of the flexible circuit board does not have copper dendrites, it is illustrated that copper ions on the surface of the flexible circuit board do not migrate after a period of time under a preset working condition, the surface of the flexible circuit board does not have leakage failure, and the leakage failure on the surface of the flexible circuit board can be eliminated, so that the leakage failure inside the flexible circuit board can be determined.
Optionally, fig. 5 is a flowchart of step 112 in fig. 3, referring to fig. 5, step 112 includes, according to a decrease of the insulation resistance, determining whether the flexible circuit board has an internal leakage failure:
and 1122, the resistance of the insulation resistor is reduced to be smaller than a preset resistance value, and the flexible circuit board is determined to have leakage failure.
The preset resistance value is 100MΩ, the resistance value of the insulation resistor is reduced to be smaller than 100MΩ, the condition that short circuit occurs between test lines due to copper ion migration is proved, and the flexible circuit board leakage failure is determined.
And 1123, if at least one of copper dendrites, pollutants and corrosion products exist on the surface of the flexible circuit board, determining that the flexible circuit board has surface leakage failure.
If the growth of copper dendrites on the surface of the flexible circuit board is observed through an optical microscope, the existence of copper ion migration phenomenon on the surface of the flexible circuit board can be determined, and the condition that short circuit occurs between test circuits due to copper ion migration is proved, so that the existence of leakage failure on the surface of the flexible circuit board can be determined.
The copper dendrite, pollutant or corrosion product on the surface of the flexible circuit board can be treated by alcohol, the influence of surface leakage failure on the resistance value of the insulation resistance of the flexible circuit board is eliminated, and the insulation resistance test is performed again after air drying.
And 1125, obtaining the resistance value of the insulation resistor after the surface of the flexible circuit board is treated, and if the resistance value of the insulation resistor is smaller than a preset resistance value, determining that the internal leakage of the flexible circuit board fails.
If the resistance value of the insulation resistor after the surface of the flexible circuit board is treated is smaller than 100MΩ, it is indicated that no copper dendrite, no pollutant or no corrosion product residue exists on the surface of the flexible circuit board, and thus the surface of the flexible circuit board is subjected to leakage failure, and the inside of the flexible circuit board is determined to be subjected to leakage failure.
Specifically, if the resistance of the insulation resistor is greater than 100mΩ, it indicates that the flexible circuit board only has copper dendrites on the surface to cause electric leakage, the interior of the board is not failed, fig. 6 is a schematic diagram of the interior of the flexible circuit board provided by the embodiment of the present invention, fig. 7 is another schematic diagram of the interior of the flexible circuit board provided by the embodiment of the present invention, and referring to fig. 6 and fig. 7, it is found that the interior of the flexible circuit board does not have a copper ion migration phenomenon, which is not an analysis object of the present scheme, and after the test, it can be proved that the flexible circuit board has no phenomenon of abnormal material selection and processing process.
Optionally, step 1124 includes excluding the resistive effect of surface leakage failure on the insulation resistance of the flexible circuit board including:
the surface of the flexible circuit board is treated to remove at least one of copper dendrites, contaminants, and corrosion products.
The copper dendrite, the pollutant or the corrosion product on the surface of the flexible circuit board is cleaned by alcohol, so that the copper dendrite, the pollutant or the corrosion product can be removed, the influence of surface leakage failure is eliminated, and after the copper dendrite, the pollutant or the corrosion product on the surface of the flexible circuit board is removed, the insulation resistance is detected again, so that whether the leakage failure exists in the flexible circuit board can be determined.
Optionally, if the flexible circuit board has an internal leakage failure, step 120 further includes:
and determining the position of the leakage failure in the flexible circuit board.
The flexible circuit board is utilized to generate electric leakage between circuits when copper ions migrate, the microscopic infrared thermal imaging system is utilized to capture the position of electric leakage failure, and slicing treatment is carried out on the position of the flexible circuit board, so that the accuracy of the slicing treatment position can be improved, the test time is saved, and the success rate of metallographic slicing is improved.
Optionally, determining the location of the electrical leakage failure within the flexible circuit board includes: and determining the position of the leakage failure in the flexible circuit board through a microscopic infrared thermal imaging system.
The radiation heat of the leakage area is relatively high, so that the leakage failure position inside the flexible circuit board is determined through the micro infrared thermal imaging system, and the leakage failure position can be red in the micro infrared thermal imaging system.
Optionally, fig. 8 is a detailed flowchart of step 120 in fig. 2, and referring to fig. 8, step 120 includes:
And cutting the leakage failure position inside the flexible circuit board into a measurement sample conforming to the measurement size.
And 122, encapsulating and curing the measurement sample by using resin glue.
Wherein, epoxy resin is used: the curing agent is uniformly mixed and stirred according to the ratio of 1:1, and after the bubbles are removed, the invalid position on the sample is encapsulated, and the curing agent can be cured for 8 hours at room temperature.
And 123, polishing the measurement sample along the direction parallel to the surface of the flexible circuit board.
Wherein, grind and polish along the direction parallel to FPC face with the abrasive paper of different mesh numbers to observe under metallographic microscope, expose copper dendrite.
Optionally, obtaining the morphology of the flexible circuit board after slicing treatment includes: and observing the appearance of the flexible circuit board after slicing by a metallographic microscope to obtain the appearance of the flexible circuit board after slicing.
Fig. 9 is a schematic diagram of copper dendrites provided by the embodiment of the present invention, and fig. 10 is a schematic diagram of another copper dendrite provided by the embodiment of the present invention, referring to fig. 9 and 10, without positioning by using a microscopic infrared thermal imaging system, by observing the morphology of a slice of a flexible circuit board after processing by a metallographic microscope, it can be observed that copper ion migration exists in the slice of the flexible circuit board, thereby determining that copper dendrite growth exists.
Optionally, the flexible circuit board is under a preset working condition comprising: the working voltage is less than or equal to 100V; the preset temperature and humidity conditions comprise any one of 85 ℃ temperature, 85% RH humidity, 40 ℃ temperature, 93% RH humidity, 65 ℃ temperature, 88% RH humidity, 60 ℃ temperature and 90% RH humidity; the preset time includes any one of 2 hours, 1 hour, 0.5 hours, 10 minutes, and 1 minute.
Wherein, the working voltage is less than or equal to 100V, and the preferred working voltage can be 10V.
Exemplary, fig. 11 is a failure circuit diagram of an insulation resistance according to an embodiment of the present invention, and referring to fig. 11, a flexible circuit board is stored in a wet heat box at a storage condition temperature of 85 c, a humidity of 85% rh for 500 hours, an operating voltage of 10VDC, and an insulation resistance test voltage of 100VDC is applied between adjacent and mutually insulated wires to be tested. The resistance of the insulation resistance between the tested wires is tested every 1min during the storage period, and the phenomenon that the resistance of the insulation resistance is reduced after the storage is carried out for 240 hours can be found, namely, the flexible circuit board is stored for a period of time under the preset working condition, and then the copper ion migration phenomenon can occur, so that the short circuit condition occurs between the tested wires, and the phenomenon that the resistance of the insulation resistance is reduced is caused; the abscissa is the time for measuring insulation resistance between test lines, the ordinate is the resistance value of insulation resistance between test lines, three lines respectively represent the resistance values of insulation resistance of test lines of different pitches within a preset time, the insulation resistance values of the test lines at pitches of 0.05mm,0.1mm and 0.25mm are exemplarily shown in fig. 11, the pitch of the adjacent and insulated wires to be tested is 0.05mm, the pitch of the adjacent and insulated wires to be tested is 0.1mm, the pitch of the adjacent and insulated wires to be tested is 0.25mm, and it can be seen from fig. 11 that the insulation resistance of the wires to be tested at the pitch of 0.05mm is reduced, so that it can be determined that the leakage failure occurs in the wires to be tested here.
The surface of the flexible circuit board is observed through an optical microscope, obvious dendrite growth is not seen on the surface of the flexible circuit board, and the occurrence of leakage failure in the flexible circuit board can be further judged; by applying a working voltage between test lines, an exemplary working voltage may be 50V DC, and by capturing the leakage position by using a micro-infrared thermal imaging system, fig. 12 is a schematic diagram of the position of internal leakage failure provided by the embodiment of the present invention, and referring to fig. 12, black dots in a black circle are leakage positions, and the black dots are displayed in red under the micro-infrared thermal imaging system, so as to determine the position of internal leakage failure of the flexible circuit board. And then slicing the flexible circuit board, observing under a metallographic microscope until copper dendrites are exposed, wherein fig. 13 is a schematic diagram of another copper dendrite provided by the embodiment of the invention, and referring to fig. 13, it can be observed that copper dendrite growth exists at a black circle to determine that the flexible circuit board has internal leakage failure, so that unqualified products caused by copper ion migration are screened out in advance according to the determined leakage failure type, and scientific basis is provided for risk avoidance, material selection and processing process improvement of the flexible circuit board.
It should be appreciated that various forms of the flows shown above may be used to reorder, add, or delete steps. For example, the steps described in the present invention may be performed in parallel, sequentially, or in a different order, so long as the desired results of the technical solution of the present invention are achieved, and the present invention is not limited herein.
The above embodiments do not limit the scope of the present invention. It will be apparent to those skilled in the art that various modifications, combinations, sub-combinations and alternatives are possible, depending on design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.
Claims (10)
1. The method for detecting the copper migration of the inner layer of the flexible circuit board is characterized by comprising the following steps of:
judging whether a test line in the flexible circuit board has internal leakage failure or not under the preset working condition, wherein the test line is an adjacent and insulated tested wire on each layer of line of the flexible circuit board, and each tested wire is connected with a surface line and an inner layer line through a via hole;
if the flexible circuit board has internal leakage failure, slicing the flexible circuit board;
obtaining the appearance of the flexible circuit board after slicing treatment;
copper dendrites exist in the flexible circuit board, and it is determined that copper migration phenomenon exists in the flexible circuit board, so that internal leakage failure exists in the flexible circuit board.
2. The method of claim 1, wherein determining whether an internal leakage failure exists in a test line within the flexible circuit board under a predetermined operating condition of the flexible circuit board comprises:
acquiring the resistance value of the insulation resistance between the test lines at intervals of preset time;
and judging whether the flexible circuit board has internal leakage failure or not according to the reduction condition of the resistance value of the insulation resistor.
3. The method according to claim 2, wherein determining whether the flexible circuit board has an internal leakage failure according to a decrease in the resistance of the insulation resistor comprises:
the resistance value of the insulation resistor is reduced to be smaller than a preset resistance value, and the leakage failure of the flexible circuit board is determined;
and if the surface of the flexible circuit board has no leakage failure, determining that the internal leakage of the flexible circuit board fails.
4. The method according to claim 2, wherein determining whether the flexible circuit board has an internal leakage failure according to a decrease in the resistance of the insulation resistor comprises:
the resistance value of the insulation resistor is reduced to be smaller than a preset resistance value, and the leakage failure of the flexible circuit board is determined;
if at least one of copper dendrites, pollutants and corrosion products exist on the surface of the flexible circuit board, determining that the flexible circuit board has surface leakage failure;
eliminating the influence of surface leakage failure on the resistance value of the insulation resistance of the flexible circuit board;
and acquiring the resistance value of the insulation resistor after the surface of the flexible circuit board is treated, and if the resistance value of the insulation resistor is smaller than a preset resistance value, determining that the internal leakage of the flexible circuit board fails.
5. The method of claim 4, wherein excluding the resistive effect of surface leakage failure on the insulation resistance of the flexible circuit board comprises:
and processing the surface of the flexible circuit board to remove at least one of copper dendrites, pollutants and corrosion products.
6. The method according to claim 1, wherein if the flexible circuit board has an internal leakage failure, the method further comprises, before slicing the flexible circuit board:
and determining the position of the leakage failure in the flexible circuit board.
7. The method of claim 1, wherein determining the location of the electrical leakage failure within the flexible circuit board comprises:
and determining the position of the leakage failure in the flexible circuit board through a microscopic infrared thermal imaging system.
8. The method of claim 1, wherein slicing the flexible circuit board if there is an internal leakage failure of the flexible circuit board comprises:
obtaining a measurement sample of the flexible circuit board cut into a preset size;
encapsulating and curing the measurement sample by using resin glue;
and polishing the measurement sample along the direction parallel to the surface of the flexible circuit board.
9. The method of claim 1, wherein obtaining the profile of the sliced flexible circuit board comprises:
and observing the appearance of the flexible circuit board after slicing treatment through a metallographic microscope so as to obtain the appearance of the flexible circuit board after slicing treatment.
10. The method of claim 1, wherein the flexible circuit board is subjected to a predetermined operating condition comprising:
the working voltage is less than or equal to 100V;
the preset temperature and humidity conditions comprise any one of 85 ℃ temperature, 85% RH humidity, 40 ℃ temperature, 93% RH humidity, 65 ℃ temperature, 88% RH humidity, 60 ℃ temperature and 90% RH humidity;
the preset time includes any one of 2 hours, 1 hour, 0.5 hours, 10 minutes, and 1 minute.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310254394.2A CN116381342A (en) | 2023-03-16 | 2023-03-16 | Method for detecting copper migration of inner layer of flexible circuit board |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310254394.2A CN116381342A (en) | 2023-03-16 | 2023-03-16 | Method for detecting copper migration of inner layer of flexible circuit board |
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| CN116381342A true CN116381342A (en) | 2023-07-04 |
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| CN202310254394.2A Pending CN116381342A (en) | 2023-03-16 | 2023-03-16 | Method for detecting copper migration of inner layer of flexible circuit board |
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| Country | Link |
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| CN (1) | CN116381342A (en) |
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