CN115326919A - Insufficient solder defect detection method and detection system - Google Patents
Insufficient solder defect detection method and detection system Download PDFInfo
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- 230000007547 defect Effects 0.000 title claims abstract description 67
- 238000001514 detection method Methods 0.000 title claims abstract description 27
- 229910000679 solder Inorganic materials 0.000 title claims description 19
- 238000003466 welding Methods 0.000 claims abstract description 49
- 239000000463 material Substances 0.000 claims abstract description 30
- RSWGJHLUYNHPMX-UHFFFAOYSA-N Abietic-Saeure Natural products C12CCC(C(C)C)=CC2=CCC2C1(C)CCCC2(C)C(O)=O RSWGJHLUYNHPMX-UHFFFAOYSA-N 0.000 claims abstract description 18
- KHPCPRHQVVSZAH-HUOMCSJISA-N Rosin Natural products O(C/C=C/c1ccccc1)[C@H]1[C@H](O)[C@@H](O)[C@@H](O)[C@@H](CO)O1 KHPCPRHQVVSZAH-HUOMCSJISA-N 0.000 claims abstract description 18
- KHPCPRHQVVSZAH-UHFFFAOYSA-N trans-cinnamyl beta-D-glucopyranoside Natural products OC1C(O)C(O)C(CO)OC1OCC=CC1=CC=CC=C1 KHPCPRHQVVSZAH-UHFFFAOYSA-N 0.000 claims abstract description 18
- 238000001931 thermography Methods 0.000 claims abstract description 14
- 230000006698 induction Effects 0.000 claims description 79
- 238000000034 method Methods 0.000 claims description 24
- 238000010587 phase diagram Methods 0.000 claims description 15
- 238000010586 diagram Methods 0.000 claims description 10
- 239000013598 vector Substances 0.000 claims description 6
- 230000003321 amplification Effects 0.000 claims description 4
- 230000005684 electric field Effects 0.000 claims description 4
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 4
- 238000004891 communication Methods 0.000 claims description 3
- 238000009792 diffusion process Methods 0.000 claims description 3
- 230000005540 biological transmission Effects 0.000 claims description 2
- 230000000737 periodic effect Effects 0.000 claims description 2
- 238000012876 topography Methods 0.000 claims description 2
- 238000003384 imaging method Methods 0.000 abstract description 3
- 238000005516 engineering process Methods 0.000 abstract description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 32
- 238000005476 soldering Methods 0.000 description 18
- 229910052759 nickel Inorganic materials 0.000 description 16
- 229910052782 aluminium Inorganic materials 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- 239000010949 copper Substances 0.000 description 4
- 239000007769 metal material Substances 0.000 description 4
- 229910000838 Al alloy Inorganic materials 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 230000002950 deficient Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 1
- 229910001295 No alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- JRBRVDCKNXZZGH-UHFFFAOYSA-N alumane;copper Chemical compound [AlH3].[Cu] JRBRVDCKNXZZGH-UHFFFAOYSA-N 0.000 description 1
- 239000011365 complex material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- YOCUPQPZWBBYIX-UHFFFAOYSA-N copper nickel Chemical compound [Ni].[Cu] YOCUPQPZWBBYIX-UHFFFAOYSA-N 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
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- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/72—Investigating presence of flaws
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/0002—Inspection of images, e.g. flaw detection
- G06T7/0004—Industrial image inspection
- G06T7/001—Industrial image inspection using an image reference approach
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30108—Industrial image inspection
- G06T2207/30152—Solder
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Abstract
The embodiment of the application discloses and provides a rosin joint defect detection method and a rosin joint defect detection system, the rosin joint defect detection method detects a rosin joint defect area in a welding layer of a piece to be tested based on an eddy current phase-locked thermal imaging technology, and modulates phase-locked eddy currents to heat the piece to be tested according to alternating signals with different frequencies, so that the material complexity and the influence of inconsistent material surface emissivity are effectively inhibited, the imaging of a thermal imager is clearer, the detection depth is larger, and the applicability is wider.
Description
Technical Field
The application relates to the technical field of welding part detection, in particular to a method and a system for detecting a rosin joint defect.
Background
In carrying out the laser welding process to two-layer material, the opposite face of two-layer material forms the welding layer because of laser melting, and this kind of laser welding mode has the risk that appears the rosin joint defect in the welding layer, connects insecurely between the two-layer material that rosin joint defect region corresponds, appears electric conductive property difference easily after using one end time, leads to the trouble to take place. For the detection of the insufficient soldering defect, a finite element analysis method for the insufficient soldering detection is adopted in the prior art, and the method is based on the eddy current pulse thermal imaging principle, and the insufficient soldering defect area is found by analyzing the temperature change curve difference between the insufficient soldering defect and the normal welding area in the heating and cooling processes through the finite element. However, in practical application, the pulsed eddy current heating is not uniform, the detection depth is not large, the imaging image is seriously interfered by the eddy current background noise, the complex surface cannot intuitively form an effective observable image, and the accuracy of the detection result of the insufficient solder defect is influenced.
Disclosure of Invention
The embodiment of the application provides a method and a system for detecting a cold joint defect, which can solve the problems of uneven eddy current heating and poor detection result accuracy caused by shallow detection depth of the existing eddy current pulse detection cold joint defect.
The embodiment of the application provides a method for detecting a cold joint defect, which is used for detecting a welding layer in a piece to be tested and comprises the following steps:
s1) providing high-frequency alternating current, and carrying out amplitude modulation on the high-frequency alternating current through a low-frequency phase-locked signal to generate a periodically-changed current signal;
s2) arranging an induction coil at one side of the to-be-tested piece, and supplying the periodically-changed current signal to the induction coil after power amplification so that the induction coil generates a periodically-changed induction magnetic field;
s3) according to the periodically-changed induction magnetic field generated by the induction coil, the to-be-tested piece generates a phase-locked eddy current with variable frequency so as to heat the to-be-tested piece;
s4) collecting temperature data of one surface of the piece to be tested, which is far away from the induction coil, within a supply time length, wherein the supply time length is the time length for supplying the periodically-changed current signal to the induction coil;
s5) processing the temperature data through Fourier transform to form an amplitude diagram and a phase diagram;
s6) comparing the amplitude diagram and the phase diagram with the amplitude diagram and the phase diagram of the normal welding area of the piece to be tested.
Optionally, in step S2), the induction coils are arranged in parallel with the adjacent surface of the test piece.
Optionally, the device to be tested includes a first layer and a second layer stacked, opposite surfaces of the first layer and the second layer are welded to form the welding layer, and the supply time in step S4) is t r ,
L r And alpha is the sum of the thicknesses of the first layer of the piece to be tested and the welding layer, and the thermal diffusion coefficient of the piece to be tested.
Optionally, in step S3), part of the phase-locked eddy current is converted into heat energy inside the device under test to heat the device under test, the heat generated by the phase-locked eddy current inside the device under test is Q1,
σ denotes the conductivity of the test piece, J S The density of the eddy current induced is shown, and E is the electric field strength.
Optionally, in step S4), the heat Q1 generated by the phase-locked eddy current inside the to-be-tested piece is transferred from the side of the to-be-tested piece close to the induction coil to the side far from the induction coil, and the heat transferred to the side of the to-be-tested piece far from the induction coil is Q2,
in the above formula, ρ represents the material density of the test piece, C p Which represents the thermal capacity of the piece to be tested,
the divergence operator is represented by a vector of vectors,
denotes the gradient operator and k denotes the thermal conductivity of the piece to be tested.
Optionally, when a insufficient soldering defect area exists in the soldering layer of the to-be-tested piece, the temperature of an area, corresponding to the insufficient soldering defect area, on the side, away from the induction coil, of the to-be-tested piece is T1, the temperature of an area, corresponding to the normal soldering area, on the side, away from the induction coil, of the to-be-tested piece is T2, and T1 is less than T2; when the difference between T1 and T2 reaches a maximum value, the current signal supply to the induction coil is stopped.
Optionally, in step S5), fourier transform is performed on the supply time t according to the following formula r The temperature data T are respectively converted from time threshold to frequency threshold to obtain amplitude response and phase response,
n is the maximum time value, ω is the angular frequency,
is phase, A (omega) is amplitude, phase according to multiple temperature data T
The phase map is formed, and the amplitude map is formed according to the amplitudes A (omega) of the plurality of temperature data T.
Optionally, in step S6), an infrared thermal imaging recorder is used to collect a thermography image of the second layer far from the first layer, where the thermography image includes a plurality of pixel temperature points, and each pixel temperature point corresponds to one of the temperature data T.
Simultaneously, this application embodiment still provides a rosin joint defect detecting system for detect the welding layer in waiting to test the piece, rosin joint defect detecting system includes: the phase-locked signal source is used for generating a high-frequency alternating current and a low-frequency phase-locked signal, and the low-frequency phase-locked signal is used for carrying out amplitude modulation on the high-frequency alternating current so as to generate a periodically-changed current signal; the input end of the power amplifier is electrically connected with the output end of the phase-locked signal source so as to receive the periodically-changed current signal, and the power amplifier is used for performing power amplification on the periodically-changed current signal; the induction coil is arranged opposite to one surface of the piece to be tested and is electrically connected with the output end of the power amplifier so as to receive a power amplified current signal and generate a periodically-changed induction magnetic field; the thermal imaging instrument is arranged opposite to one surface, far away from the induction coil, of the to-be-tested piece, and is used for acquiring a thermal image of one surface, far away from the induction coil, of the to-be-tested piece; the host computer, the output of thermal imaging appearance with host computer communication connection in order to the host computer transmission temperature data in the thermal image picture, the host computer includes processing module and comparison module, processing module is used for right temperature data carries out Fourier transform in order to form amplitude map and phase diagram, the comparison module is used for comparing the amplitude map and the phase diagram in rosin joint defect region with normal welding region's amplitude map and phase diagram to acquire the topography feature in rosin joint defect region.
Optionally, the thermal imager is an infrared thermal imager.
The method has the advantages that amplitude modulation is carried out on high-frequency alternating current through a low-frequency phase-locked signal, a periodically-changed current signal is formed, the current signal with amplified power is supplied to an induction coil, a periodically-changed induction magnetic field is formed, the induction coil is arranged on one side of a to-be-tested piece, the periodically-changed induction magnetic field generates phase-locked eddy currents with changed frequency inside the to-be-tested piece, the to-be-tested piece is heated through the phase-locked eddy currents with changed frequency, generated heat is transmitted to the side, far away from the induction coil, of the to-be-tested piece, a thermal imaging instrument collects a thermal image of the side, far away from the induction coil, of the to-be-tested piece and generates temperature data, an amplitude image and a phase image are formed according to the temperature data, and the virtual welding defect area in the welding layer of the to-be-tested piece is detected through comparing the amplitude image and the phase image with the amplitude image and the phase image of a normal welding area.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic flowchart of a method for detecting a cold joint defect according to an embodiment of the present application;
FIG. 2 is a schematic structural diagram of a cold joint defect detection system according to an embodiment of the present application;
FIG. 3 is a schematic view of a structure of a test piece.
Description of reference numerals:
100. a cold joint defect detection system 110, a phase-locked signal source 120, a power amplifier 130, an induction coil 140, a thermal imager 150, an upper computer 151, an analysis module 152 and a comparison module;
200. the method comprises the steps of a to-be-tested piece 201, a first surface 202, a second surface 210, a first layer 220, a second layer 230, a welding layer 231, a false welding defect area 232 and a normal welding area.
Detailed Description
The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments obtained by a person skilled in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application. Furthermore, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are given by way of illustration and explanation only, and are not intended to limit the scope of the invention. In the present application, unless indicated to the contrary, the use of the directional terms "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, and more particularly to the orientation of the figures of the drawings; while "inner" and "outer" are with respect to the outline of the device. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the described features.
The method and system for detecting the defect of the cold joint provided by the embodiment of the application modulate the amplitude of the high-frequency alternating current through the low-frequency phase-locked signal to form a periodically-changed current signal, supply the power-amplified current signal to the induction coil to form a periodically-changed induction magnetic field, the induction coil is arranged at one side of the piece to be tested, the periodically-changed induction magnetic field generates a frequency-changed phase-locked eddy current in the piece to be tested, the frequency-changed phase-locked eddy current heats the piece to be tested, the generated heat is transferred to the surface of the piece to be tested, which is far away from the induction coil, the thermal imager collects the thermal image of the surface of the piece to be tested, which is far away from the induction coil, and generates temperature data, forming an amplitude map and a phase map according to the temperature data, comparing the amplitude map and the phase map with those of the normal welding area, whether the insufficient solder defect exists in the welding layer of the piece to be tested can be detected, the method is based on the eddy current phase-locked thermal imaging technology to detect the insufficient solder defect area in the welding layer of the piece to be tested, the AC signals with different frequencies are used for modulating the phase-locked eddy current to heat the piece to be tested, thereby effectively inhibiting the influence of complex materials and inconsistent material surface emissivity, enabling a thermal imager to have clearer imaging, larger detection depth and wider applicability as typical application, the method and the system for detecting the cold joint defects can be used for detecting the cold joint defects of the welding position of two layers of materials, are particularly suitable for detecting the cold joint defects of the welding layer between two layers of conductive metal materials, such as a solder layer between a layer of nickel material and a layer of aluminum material, a solder layer between a layer of nickel material and a layer of nickel material, a solder layer between a layer of nickel material and a layer of copper material, a solder layer between two layers of nickel-aluminum alloy, and a solder layer between two layers of nickel-copper alloy.
In an embodiment of the present application, a method for detecting a cold joint defect is provided, referring to fig. 1 to 3, the method for detecting a cold joint defect is used to detect a cold joint defect of a welding layer 230 in a test piece 200 to be tested, referring to fig. 3, the test piece 200 to be tested includes a first layer 210 and a second layer 220 which are stacked, opposite surfaces of the first layer 210 and the second layer 220 are welded to form the welding layer 230, a first surface 201 of the test piece 200 to be tested is formed on a surface of the first layer 210 away from the second layer 220, a second surface 202 of the test piece 200 to be tested is formed on a surface of the second layer 220 away from the first layer 210, and the first surface 201 and the second surface 202 are arranged opposite to each other.
The method for detecting the insufficient soldering defect described with reference to fig. 1 comprises the following steps:
s1) providing high-frequency alternating current, and carrying out amplitude modulation on the high-frequency alternating current through a low-frequency phase-locked signal to generate a current signal with periodic variation;
s2) arranging the induction coil 130 on one side of the first layer 210 of the piece to be tested 200 in parallel, amplifying the power of the periodically-changed current signal, and supplying the periodically-changed current signal to the induction coil 130 so that the induction coil 130 generates a periodically-changed induction magnetic field;
s3) according to the periodically-changed induction magnetic field generated by the induction coil 130, the to-be-tested piece 200 generates a phase-locked eddy current with variable frequency to heat the to-be-tested piece 200;
s4) collecting temperature data of the second surface 202 of the test piece 200 to be tested for a supply period of time during which the periodically varying current signal is supplied to the induction coil 130;
s5) processing the temperature data through Fourier transform to form an amplitude diagram and a phase diagram;
s6) comparing the amplitude map and the phase map with the amplitude map and the phase map of the normal welding area of the piece to be tested 200.
Meanwhile, in this embodiment, a rosin joint defect detection system 100 is further provided, where the rosin joint defect detection system 100 performs rosin joint defect detection on the welding layer 230 in the test piece 200 to be detected by using the rosin joint defect detection method shown in fig. 1, and referring to fig. 2, the rosin joint defect detection system 100 includes: a phase-locked signal source 110, a power amplifier 120, an induction coil 130, a thermal imager 140 and an upper computer 150. The output end of the phase-locked signal source 110 is electrically connected to the input end of the power amplifier 120, the output end of the power amplifier 120 is electrically connected to the input end of the induction coil 130, the output end of the thermal imager 140 is in communication connection with the upper computer 150, and the thermal imager 140 and the induction coil 130 are arranged oppositely.
When the test piece 200 is used, the test piece 200 is arranged between the induction coil 130 and the thermal imaging camera 140, the induction coil 130 and the first surface 201 of the test piece 200 are arranged in parallel at intervals, and the image acquisition end of the thermal imaging camera 140 faces the second surface 202 of the test piece 200.
The phase-locked signal source 110 is configured to generate the high-frequency alternating current and the low-frequency phase-locked signal in step S1), and the low-frequency phase-locked signal is configured to perform amplitude modulation on the high-frequency alternating current to form a current signal with a period variation, in this embodiment, the frequency range of the high-frequency alternating current is: 100 KHz-300 KHz, the frequency range of the low-frequency phase-locked signal is as follows: 0.1 Hz-1 Hz, the frequency variation range of the periodically-varying current signal obtained after the high-frequency alternating current is subjected to low-frequency phase-locked signal amplitude modulation (amplitude modulation) is as follows: the output end of the phase-locked signal source 110 outputs the current signal with the period variation, and the period variation of the current signal is consistent with the frequency variation of the current signal, that is, the period of the current signal varies according to the frequency variation of the current signal.
The input end of the power amplifier 120 is electrically connected to the output end of the phase-locked signal source 110 to receive the periodically varying current signal, and since the periodically varying current signal is low voltage and the power is usually several watts or less than a few tenths of watts, the heating of the to-be-tested piece 200 cannot be achieved, the power of the periodically varying current signal needs to be amplified, that is, the power in step S2) is amplified, and the power of the periodically varying current signal is amplified to 1KW to 2KW by the power amplifier 120, so that the rapid heating effect on the to-be-tested piece 200 is achieved.
The input end of the induction coil 130 is electrically connected to the output end of the power amplifier 120 to receive a current signal with a periodically changing power, which is amplified to 1KW to 2KW, the induction coil 130 generates a periodically changing induction magnetic field according to the periodically changing current signal, that is, the induction coil 130 generates the periodically changing induction magnetic field in step S2), the induction coil 130 is disposed at one side of the first layer 210 of the to-be-tested piece 200, the periodically changing induction magnetic field generated by the induction coil 130 enables the first surface 201 of the to-be-tested piece 200 and/or the interior of the first layer 210 to generate a phase-locked eddy current with a changing frequency, and the phase-locked eddy current is converted from electric energy to heat energy in the interior of the to-be-tested piece 200 to heat the to-be-tested piece 200. The closer the induction coil 130 is to the first surface 201 of the to-be-tested piece 200, the stronger the induction effect is, the faster the heating response is, but the induction coil 130 cannot contact with the first surface 201, and the contact causes heat conduction, so the distance between the induction coil 130 and the first surface 201 of the to-be-tested piece 200 in this embodiment is 1mm to 5mm.
If the piece to be tested 200 is heated by the ordinary vortex, the ordinary vortex can only be added to a partial area of the piece to be tested 200, so that heat is concentrated, shelters from the heat, interferes with the observation effect, and influences on the judgment of the insufficient solder defect. In this embodiment, the to-be-tested piece 200 is heated by the phase-locked eddy current with variable frequency, and the heat inside the to-be-tested piece 200 is uniformly distributed, so that the to-be-tested piece is convenient to observe and respectively has insufficient solder joint defects.
The supply time period of the periodically varying current signal to the induction coil 130 in step S3) is t r ，
L r α is a thermal diffusivity of the test piece 200, which is a sum of a thickness of the first layer 210 of the test piece 200 and a thickness of the welding layer 230. For example, if the thickness of the first layer 210 is 0.08mm, the thickness of the second layer 220 is 0.08mm, and the thickness of the welding layer 230 formed by laser welding is 0.01mm to 0.02mm, L is r Is 0.09 mm-0.1 mm.
Wherein the phase-locked eddy current generates heat Q1 by converting electric energy into heat energy in the test piece 200,
σ represents the conductivity of the test piece 200, J S The density of the eddy current induced is shown, and E is the electric field strength.
The calculation formula of the electric field intensity E is as follows:
in the above formula, r is the distance between the induction coil 130 and the first surface 201 of the test piece 200, which is 1mm to 5mm, preferably 1mm to 2mm in this embodiment, Q is the charge I/f per unit time, K is the electrostatic constant, I is the current on the induction coil 130, and f is the phase-locked frequency (i.e., the frequency of the periodically varying current signal: 10KHz to 300 KHz).
The phase-locked eddy currents with different frequencies generate heat energy with different frequencies, the heat energy Q1 is transmitted inside the to-be-tested device 200 to a direction close to the second layer 220 to form heat conduction, and the heat energy Q2 is transmitted to the second surface 202 of the to-be-tested device 200.
In the above formula, ρ represents a material of a test pieceMaterial density, C p Represents the specific heat capacity of the test piece,
the divergence operator is represented by a vector of vectors,
denotes the gradient operator and k denotes the thermal conductivity of the piece to be tested.
The first layer 210 and the second layer 220 of the test piece 200 are both made of conductive metal materials, and the welding layer 230 formed by welding the opposite surfaces of the first layer 210 and the second layer 220 is an alloy material layer formed by melting the conductive metal materials forming the first layer 210 and the conductive metal materials forming the second layer 220, for example, if the first layer 210 is a nickel material layer, the second layer 220 is an aluminum material layer, the welding layer 230 is a nickel-aluminum alloy layer.
When the materials of the first layer 210 and the second layer 220 constituting the test piece 200 are the same, for example, the first layer 210 and the second layer 220 are both nickel material layers, the conductivity σ of the test piece 200 is the conductivity of nickel, the material density ρ of the test piece 200 is the material density of nickel, and the specific heat capacity C of the test piece p Namely the heat capacity of the nickel, and the thermal conductivity k of the piece to be tested is the thermal conductivity of the nickel;
when the materials of the first layer 210 and the second layer 220 constituting the test piece 200 are different, for example, the first layer 210 is a nickel material layer, the second layer 220 is an aluminum material layer, the conductivity σ of the test piece 200 is the sum of the conductivity of nickel and the conductivity of aluminum, the material density ρ of the test piece 200 is the sum of the material density of nickel and the material density of aluminum, and the specific heat capacity C of the test piece p Namely the sum of the heat capacity of nickel and the heat capacity of aluminum, and the calculation formula of the heat conductivity k of the piece to be tested is as follows: k = K1 × K2/(K1 + K2), K1 being the thermal conductivity of the nickel of the first layer 210, and K2 being the thermal conductivity of the aluminum of the second layer 220.
In addition, the material of the first layer 210 and the material of the second layer 220 may also be copper, and is selected according to actual needs. Specifically, the properties of nickel, aluminum, and copper are shown in table 1.
TABLE 1
| Nickel (II) | Aluminium | Copper (Cu) | |
| Conductivity sigma (10) 6 S/m) | 14.62 | 22.53 | 60.09 |
| Coefficient of thermal diffusion alpha (10) -6 m 2 /s) | 22.9 | 73 | 112 |
| 100kHz skin depth/mm | 0.042 | 0.335 | 0.205 |
| 0.1s heat wave input depth/mm | 3.03 | 5.40 | 6.71 |
| Density rho (g/cm) 3 ) | 8.9 | 2.7 | 8.9 |
| (20 ℃ C.) specific heat capacity C p (kJ/kg·c) | 0.46 | 0.88 | 0.39 |
| Thermal conductivity k (w/m.k) at (20 ℃ C.) | 71.4 | 273 | 397 |
When the dummy solder defect region 231 exists, air exists in the dummy solder defect region 231, and the density of the air is 1.29 × 10 -6 g/cm 3 Specific heat capacity C at 20 ℃ p 1.004 kJ/kg.c, and a thermal conductivity k at 20 ℃ of 0.26273 w/m.k.
When a cold joint defect exists in the welding layer 230, the welding layer 230 includes a cold joint defect area 231 and a normal welding area 232, the cold joint defect area 231, i.e., a welding nickel aluminum alloy is not welded between the first layer 210 and the second layer 220, a welding blank area formed in the welding layer 230 has no alloy in the cold joint defect area 231, and air exists to form a cold joint. The thermal resistance of the insufficient soldering region 231 is higher than that of the normal soldering region 232, the insufficient soldering region 231 will hinder the heat conduction more than the normal soldering region 232, so that the heat Q2 conducted to the second surface 202 via the insufficient soldering region 231 is lower than the heat Q2 conducted to the second surface 202 via the normal soldering region 232, in other words, the temperature T1 of the region of the second surface 202 corresponding to the insufficient soldering region 231 is lower than the temperature T2 of the region of the second surface 202 corresponding to the normal soldering region 232, T1 < T2, and there is a difference between T1 and T2.
The thermal imager 140 is used for collecting the supply time t r The heat Q2 conducted to the second surface 202 forms a thermal image, which is composed of a plurality of temperature pixels,each temperature pixel point constitutes a temperature data T including a temperature T1 of a region of the second surface 202 corresponding to the cold solder defect region 231 and a temperature T2 of a region of the second surface 202 corresponding to the normal solder region 232. When the difference between T1 and T2 reaches a maximum value, the supply of the periodically varying current signal to the induction coil 130 is stopped, and an optimal thermal image can be obtained. And the time period T1 and the supply time period T required for reaching the maximum difference between T1 and T2 r Are substantially the same, i.e. t1 and t r The absolute value of the difference between them is less than or equal to 1. The thermal imager 140 is an infrared thermal imager.
The thermal imager 140 transmits the temperature data T to the upper computer 150, the upper computer 150 comprises an analysis module 151 and a comparison module 152, the analysis module 151 receives the temperature data T, and the analysis module 151 performs fourier transform on the supply time T according to the following formula r The temperature data T are respectively converted from time threshold to frequency threshold to obtain amplitude response and phase response,
n is the maximum time value, ω is the angular frequency,
is phase, and A (omega) is amplitude, phase according to multiple temperature data T
The phase map is formed, and the amplitude map is formed according to the amplitudes A (omega) of the plurality of temperature data T. The upper computer 150 is also communicatively connected to the phase-locked signal source 110 to control the phase-locked signal source 110.
Since the temperature data T includes the temperature T1 of the region of the second surface 202 corresponding to the defective welding region 231 and the temperature T2 of the region of the second surface 202 corresponding to the normal welding region 232, there is a difference between the amplitude diagram and the phase diagram formed by the temperature T1 corresponding to the defective welding region 231 and the amplitude diagram and the phase diagram formed by the temperature T2 corresponding to the normal welding region 232, and the comparison module 152 can obtain the topographic features of the defective welding region 231 by comparing the difference. Wherein, the upper computer 150 is a PC.
The method and system for detecting a cold joint defect provided by the embodiment of the present application are described in detail above, a specific example is applied in the description to explain the principle and the implementation of the present application, and the description of the above embodiment is only used to help understand the method and the core idea of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (10)
1. A method for detecting a cold joint defect is used for detecting a welding layer in a piece to be tested and is characterized by comprising the following steps:
s1) providing high-frequency alternating current, and carrying out amplitude modulation on the high-frequency alternating current through a low-frequency phase-locked signal to generate a current signal with periodic variation;
s2) arranging an induction coil at one side of the to-be-tested piece, and supplying the periodically-changed current signal to the induction coil after power amplification so that the induction coil generates a periodically-changed induction magnetic field;
s3) according to the periodically-changed induction magnetic field generated by the induction coil, the to-be-tested piece generates a phase-locked eddy current with variable frequency so as to heat the to-be-tested piece;
s4) collecting temperature data of one surface of the piece to be tested, which is far away from the induction coil, within a supply time length, wherein the supply time length is the time length for supplying the periodically-changed current signal to the induction coil;
s5) processing the temperature data through Fourier transform to form an amplitude diagram and a phase diagram;
s6) comparing the amplitude diagram and the phase diagram with the amplitude diagram and the phase diagram of the normal welding area of the piece to be tested.
2. A cold joint defect detection method according to claim 1, wherein in step S2) said induction coil is arranged in parallel with the adjacent surface of said test piece.
3. The insufficient solder defect detection method according to claim 1, wherein the test piece includes a first layer and a second layer arranged in a stack, opposite surfaces of the first layer and the second layer are welded to form the welding layer, and the supply time period in step S4) is t r ,
L r And alpha is the sum of the thicknesses of the first layer of the piece to be tested and the welding layer, and the thermal diffusion coefficient of the piece to be tested.
4. The cold joint defect detecting method according to claim 1, wherein in step S3), part of the phase-locked eddy currents are converted into heat energy inside the device under test to heat the device under test, the amount of heat generated by the phase-locked eddy currents inside the device under test is Q1,
sigma representing the piece to be testedElectrical conductivity, J S The density of the eddy current induced is shown, and E is the electric field strength.
5. The method for detecting a cold joint defect of claim 1, wherein in step S4), the heat Q1 generated by the phase-locked eddy current in the to-be-tested piece is transferred from the side of the to-be-tested piece close to the induction coil to the side far from the induction coil, the heat transferred to the side of the to-be-tested piece far from the induction coil is Q2,
in the above formula, ρ represents the material density of the test piece, C p Indicating the heat capacity of the piece to be tested,
the divergence operator is represented by a vector of vectors,
denotes the gradient operator and k denotes the thermal conductivity of the piece to be tested.
6. The method for detecting a cold joint defect of claim 5, wherein when a cold joint defect area exists in the solder layer of the device under test, the temperature of the area corresponding to the cold joint defect area on the surface of the device under test away from the induction coil is T1, the temperature of the area corresponding to the normal solder area on the surface of the device under test away from the induction coil is T2, and T1 is less than T2;
when the difference between T1 and T2 reaches a maximum value, the current signal supply to the induction coil is stopped.
7. A cold joint defect detecting method according to claim 1, wherein in step S5), said supply time period t is subjected to fourier transform according to the following formula r A plurality of temperature data T are respectively defined by time thresholdSwitching to frequency threshold, obtaining amplitude response and phase response,
n is the maximum time value, ω is the angular frequency,
is phase, and A (omega) is amplitude, phase according to multiple temperature data T
The phase map is formed, and the amplitude map is formed according to the amplitudes A (omega) of the plurality of temperature data T.
8. A cold joint defect detecting method according to claim 7, wherein in step S6), an infrared thermal imaging recorder is used to collect a thermal image of a surface of the second layer far from the first layer, the thermal image includes a plurality of pixel temperature points, and each pixel temperature point corresponds to one of the temperature data T.
9. A cold joint defect detection system for detecting a weld layer in a test piece, the cold joint defect detection system comprising:
the phase-locked signal source is used for generating a high-frequency alternating current and a low-frequency phase-locked signal, and the low-frequency phase-locked signal is used for carrying out amplitude modulation on the high-frequency alternating current so as to generate a periodically-changed current signal;
the input end of the power amplifier is electrically connected with the output end of the phase-locked signal source so as to receive the periodically-changed current signal, and the power amplifier is used for performing power amplification on the periodically-changed current signal;
the induction coil is arranged opposite to one surface of the piece to be tested and is electrically connected with the output end of the power amplifier so as to receive a power amplified current signal and generate a periodically-changed induction magnetic field;
the thermal imaging instrument is arranged opposite to one surface, far away from the induction coil, of the to-be-tested piece, and is used for acquiring a thermal image of one surface, far away from the induction coil, of the to-be-tested piece;
the host computer, the output of thermal imaging appearance with host computer communication connection in order to the host computer transmission temperature data in the thermal image picture, the host computer includes processing module and comparison module, processing module is used for right temperature data carries out Fourier transform in order to form amplitude map and phase diagram, the comparison module is used for comparing the amplitude map and the phase diagram in rosin joint defect region with normal welding region's amplitude map and phase diagram to acquire the topography feature in rosin joint defect region.
10. A cold solder defect detection system according to claim 9, wherein said thermal imager is an infrared thermal imager.
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