Method for detecting welding quality of high-precision diverter

Abstract

The invention provides a method for detecting the welding quality of a high-precision shunt, and belongs to the technical field of nondestructive testing of electronic components. Aiming at the problems of low coverage rate, poor reliability and the like of the existing destructive sampling inspection, a non-destructive full inspection scheme based on resistance measurement is provided. Comprising the steps that an existing high-precision resistance tester capable of eliminating thermoelectric force is adopted, and a shunt welding area is connected through a four-wire system test interface of the existing high-precision resistance tester; a 1A test current (adaptive to a range of 10-100 [mu] Omega) is set, and thermoelectric force interference is eliminated by using a current commutation function; dynamically acquiring forward and reverse voltage drops and calculating an average resistance value; and the welding quality is judged by comparing the resistance value with a preset qualified interval. And if the resistance value exceeds the limit, judging that missing soldering or unsoldering exists. According to the method, welding defect identification with the micro-ohm-level precision is achieved, the detection precision reaches + / -5 micro ohms, the single detection time is shorter than 1 second, the problems of destructiveness and low coverage of traditional sampling inspection are solved, and the method can be applied to full-process quality control of micro-resistance elements such as a shunt for a new energy vehicle.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic component quality detection, in particular to a non-destructive high-precision shunt welding quality detection method based on resistance measurement principle, which is suitable for full-process quality control of micro-ohm shunts. BACKGROUND

[0002] The resistance value of high-precision shunts (such as current detection shunts for new energy vehicles) is extremely small (usually 10-100 μΩ), and the welding quality directly affects the conductivity. However, the traditional detection method has two defects: (1) destructive sampling inspection, which requires cutting the welding part to observe the open welding / de-welding, cannot cover 100% of the products, and the damaged samples cannot be used; (2) risk of missed detection, welding defects may exist in the uncut area, and the sampling inspection conclusion is unreliable.

[0003] The existing resistance tester cannot stably measure the micro-ohm resistance change due to thermoelectric potential interference and contact resistance error.

[0004] Patent No. 202210766303.9 discloses a high-precision resistance tester capable of eliminating thermoelectric potential, which comprises a single-chip microcomputer, a display screen, a constant-current constant-voltage circuit, a measurement current reversing circuit, a collection conversion circuit, a gear conversion circuit and an AD conversion circuit connected with the single-chip microcomputer. The test current output by the constant-current constant-voltage circuit enters the measurement current reversing circuit, and the forward current or negative current output by the measurement current reversing circuit flows into the gear conversion circuit. A plurality of sampling resistors in the gear conversion circuit are connected in parallel and are connected in series with the measured resistance. The control end of the collection conversion circuit is connected with the single-chip microcomputer. The collection conversion circuit collects the voltage drop across the sampling resistor or the measured resistance, and then transmits the analog-to-digital converted signal to the single-chip microcomputer through the AD conversion circuit. The present application can eliminate the influence of contact potential and thermoelectric potential in resistance testing, and improve the accuracy and precision of testing. SUMMARY

[0005] The present application aims to provide a method for detecting the welding quality of high-precision shunts to solve the problems raised in the background art:

[0006] (1) How to use the high-precision resistance tester capable of eliminating thermoelectric potential in the existing patent to solve the detection problem of shunt open welding / de-welding, especially for micro-ohm resistance (10-100 μΩ) welding quality, which can only be detected by destructive sampling inspection, with limited effect.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] A method for detecting the welding quality of high-precision shunts, comprising the following steps:

[0009] a) the test interface of the high-precision resistance tester capable of eliminating thermoelectric potential is connected with the welding area of the high-precision shunt respectively;

[0010] b) by detecting the resistance value of the high-precision shunt between the test interfaces, if the resistance of the high-precision shunt is in the qualified interval of the nominal resistance value, it is considered that the high-precision shunt does not exist the conditions of empty welding or welding off. Otherwise, the welding operation of the high-precision shunt is unqualified.

[0011] On the basis of the above technical solutions, the application can also be improved as follows.

[0012] Further, in step b, the first gear of the high-precision resistance tester capable of eliminating thermoelectric potential is selected, which is suitable for 10-100 mu omega high-precision shunt; the test current is set to 1A; the current reversing function is enabled to eliminate thermoelectric potential;

[0013] The test interface of the high-precision resistance tester capable of eliminating thermoelectric potential is connected with the two ends of the shunt welding area through four-wire system;

[0014] The solid-state relay is switched to the resistance acquisition mode of the measured resistance.

[0015] Further, the qualified interval is ±1% to ±5% of the nominal resistance value of the shunt.

[0016] The method for detecting the welding quality of the high-precision shunt utilizes the physical characteristics that local resistance abnormally increases due to welding defects: if the welding is qualified, the resistance value R of the shunt is within the design nominal range (such as ±5% deviation); if the welding is empty or off, the conductive cross-sectional area of the defect is reduced, and R significantly exceeds the reasonable interval (such as > ±5%).

[0017] The method for detecting the welding quality of the high-precision shunt creates a micro-resistance-welding defect correlation model: a quantitative relationship between resistance anomaly and welding defect is established; and the existing tester's mu omega level measurement capability is innovatively applied to the welding quality field; the whole-process closed-loop quality control is realized, real-time data is fed back to the production system, and the welding parameters are dynamically optimized.

[0018] The method for detecting the welding quality of the high-precision shunt has the following beneficial effects:

[0019] (1) non-destructive detection, realizing 100% online detection of products, avoiding sampling errors;

[0020] (2) high-precision defect positioning, current reversing to eliminate thermoelectric potential, and AD conversion chip IC7 temperature compensation to ensure micro-ohm level stability;

[0021] (3) efficiency improvement, single detection < 10 seconds, which is greatly improved compared with the traditional destructive detection efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the detection process architecture diagram of the method for detecting the welding quality of the high-precision shunt.

[0023] Figure 2 is the block diagram of the dynamic detection process in the method for detecting the welding quality of the high-precision shunt.

[0024] Figure 3 is the photo of the shunt resistance after bending in the method for detecting the welding quality of the high-precision shunt.

[0025] Figure 4 is the detail photo of the material welding seam reliability of the shunt resistance in the method for detecting the welding quality of the high-precision shunt. DETAILED DESCRIPTION

[0026] In order to make the above objectives, features and advantages of the present application more apparent, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced in a variety of ways beyond those specifically described herein, and that the present application is not limited to the specific embodiments described below.

[0027] The terms "vertical", "horizontal", "left", "right", and similar expressions used herein are for illustrative purposes only and do not indicate the only implementation.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0029] Reference will now be made to Figures 1 to 2 .

[0030] The method for detecting the welding quality of the high-precision shunt comprises the following steps:

[0031] The test interfaces of the high-precision resistance tester capable of eliminating thermoelectric potential are connected with the welding areas of the high-precision shunt respectively. The resistance value of the high-precision shunt between the test interfaces is detected. If the resistance of the high-precision shunt is in the qualified interval of the nominal resistance value, it is considered that the high-precision shunt does not exist the conditions of empty welding or welding off. Otherwise, the welding operation of the high-precision shunt is unqualified.

[0032] During detection, select the 1st gear (20 mΩ range) of the high-precision resistance tester that can eliminate thermoelectric potential, and adapt the 10-100 μΩ high-precision shunt; set the test current to 1 A (controlled by the direct current optocoupler V1 of the constant current and constant voltage circuit); enable the current reversing function (measuring current reversing circuit) to eliminate thermoelectric potential;

[0033] The test interfaces (I1, I2) of the high-precision resistance tester that can eliminate thermoelectric potential are connected to the welding area of the shunt through four-wire connection (to avoid contact resistance interference);

[0034] The solid-state relay (SR5-SR8) is switched to the measured resistance collection mode (controlled by the single-chip P3.6 / P3.7 ports).

[0035] The method for detecting the welding quality of the high-precision shunt takes the 100 μΩ shunt as an example:

[0036] On the high-precision resistance tester that can eliminate thermoelectric potential, the parameters are set as follows: tester gear 1st gear (20 mΩ); constant current output 1 A; qualified interval: 95-105 μΩ (nominal value ± 5%).

[0037] The detection process of the method for detecting the welding quality of the high-precision shunt:

[0038] Before detection, select the shunt resistance for material welding seam reliability, and the sample varieties (Sample Varieties) are: HoFL3-12636-100 μΩ-5%, and the reference standards are GB / T 11345-2013 and GB / T 231.1-2009; the results are as follows Figures 3 to 4 , and the results are good. After the 90-degree elbow, no brittle cracks are found in the joint.

[0039] The detection process is as follows:

[0040] Step a: positive current output (P3.4=0, P3.5=1), and the measured voltage drop V+=98 μV;

[0041] Step b: negative current output (P3.4=1, P3.5=0), and the measured voltage drop V-=-96 μV;

[0042] Step c: calculate the average resistance R=(|98|+|96|) / 2=97 μΩ;

[0043] Step d: determine that 97 μΩ ∈ [96, 105] μΩ, and the welding is qualified.

[0044] If the measured shunt resistance exceeds the upper limit (R=105 μΩ), an alarm is triggered, and the shunt is scrapped.

[0045] In addition, 5pcs shunt resistors on the production line are randomly selected, and the method for detecting high-precision shunt welding quality is used for sampling inspection (product calibration: HoFL3-13676-12μΩ-5%).

[0046]

[0047] All 5pcs shunt resistors are qualified, and the material welding reliability of the above 5pcs shunt resistors is passed.

[0048] The method for detecting high-precision shunt welding quality can also be applied to temperature compensation algorithm (AD conversion chip IC), eight-gear adaptive switching logic, and communication interface (external communication interface circuit) integrated with the MES system.

[0049] The above is only one embodiment of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of variations and improvements can be made, which should be considered as belonging to the protection scope of the present application.

Claims

1. A method for detecting the welding quality of a high-precision shunt, comprising the following steps: a) connecting the test interfaces of a high-precision resistance tester capable of eliminating thermoelectric potential to the welding areas of the high-precision shunt respectively; b) detecting the resistance values of the high-precision shunt between the test interfaces, and if the resistance of the high-precision shunt is within the qualified interval of the nominal resistance value, it is considered that the high-precision shunt does not have the conditions of no welding or welding separation; otherwise, the welding operation of the high-precision shunt is unqualified.

2. The method for detecting the welding quality of a high-precision shunt according to claim 1, characterized in that: in step b), the first gear of the high-precision resistance tester capable of eliminating thermoelectric potential is selected to adapt to the 10-100 μΩ high-precision shunt; the test current is set to 1 A; the current commutation function is enabled to eliminate thermoelectric potential; the test interfaces of the high-precision resistance tester capable of eliminating thermoelectric potential are connected to the two ends of the shunt welding area through four-wire system; the solid-state relay is switched to the resistance collection mode.

3. The method for detecting the welding quality of a high-precision shunt according to claim 1, characterized in that: the qualified interval is ±1% to ±5% of the nominal resistance value of the shunt.

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