A comprehensive inspection method for FPC connector assembly quality

Abstract

This application provides a comprehensive inspection method for FPC connector assembly quality, relating to the field of electronic component inspection technology. The method includes appearance inspection, insertion accuracy inspection, contact reliability inspection, retention force inspection, and comprehensive evaluation. Appearance inspection identifies defects from multiple angles before FPC insertion. Insertion accuracy inspection generates a force-displacement curve, using the displacement value when the first derivative of the thrust first exceeds a threshold as the actual insertion endpoint for accuracy determination. Contact reliability inspection applies micro-vibration excitation to the FPC while it is inserted, simultaneously monitoring electrical signals, and determines contact reliability based on the presence or absence of momentary disconnection. Retention force inspection applies an increasing pull-out force, using the force value when the FPC begins to slip as the measured retention force for evaluation. Comprehensive evaluation integrates the results of each step according to weights, outputting a three-level evaluation result. This invention achieves online comprehensive inspection of FPC connector assembly quality, effectively detecting latent contact defects that are difficult to detect visually.

Description

Technical Field

[0001] This invention relates to the field of electronic component testing technology, and in particular to a comprehensive testing method for the assembly quality of FPC connectors. Background Technology

[0002] FPC connectors are widely used in consumer electronics products such as smartphones, tablets, and wearable devices due to their small size, light weight, and flexibility. The assembly quality of FPC connectors directly affects the signal transmission reliability and lifespan of electronic devices.

[0003] Currently, the main problems in inspecting the assembly quality of FPC connectors are as follows: First, existing inspection methods are mostly single-dimensional. For example, machine vision-based inspection methods can only identify visual defects and cannot determine the contact state between the terminals and the housing; insertion and extraction force tests can only reflect the mechanical characteristics of the insertion process and cannot assess the long-term retention performance of the FPC after insertion. Second, existing inspections are mostly offline sampling inspections. After product assembly, they are sent to separate inspection stations or equipment for testing. The inspection process is separated from the assembly process, which is not only inefficient but also cannot achieve full inspection. Third, some publicly available multimodal fusion inspection methods fuse data from multiple physical fields such as electrical stress, thermal stress, and mechanical stress. The purpose is to diagnose the root cause of defects and predict their evolution trends, which falls under the category of in-depth product reliability analysis, rather than online comprehensive quality judgment during the assembly process. Fourth, there is a lack of inspection methods for the flexible characteristics of FPCs. Due to the softness of the material, FPCs may appear to be properly inserted, but in reality, there may be poor contact between the terminals and the connector contacts. Existing inspection methods lack effective online detection means for such hidden defects.

[0004] To address the aforementioned issues, there is an urgent need for a comprehensive testing method that can simultaneously perform multi-dimensional quality inspections during the FPC connector assembly process. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a comprehensive method for inspecting the assembly quality of FPC connectors.

[0006] The comprehensive testing method for FPC connector assembly quality provided in this application adopts the following technical solution: A comprehensive inspection method for FPC connector assembly quality includes the following steps: S1. Appearance inspection: Before the FPC is inserted into the connector housing, the appearance image data of the FPC connector is obtained through multi-angle visual inspection to identify appearance defects. S2. Insertion in place detection: During the process of inserting the FPC into the connector housing, the insertion thrust and displacement data are collected to generate a force-displacement curve. The displacement value corresponding to the first time the first derivative of the insertion thrust in the force-displacement curve exceeds the preset derivative threshold is taken as the actual insertion endpoint. The actual insertion endpoint is compared with the theoretical insertion endpoint, and the insertion is determined based on the comparison result. S3. Contact reliability test: When the FPC is in the inserted state, apply micro-vibration excitation to the FPC connector. The amplitude of the micro-vibration excitation is A, and the value of A ranges from 0.05 mm to 0.10 mm. During the continuous micro-vibration excitation, continuously monitor the electrical signal of the FPC connector. Determine whether the contact is reliable based on whether there is a momentary interruption in the electrical signal. S4. Holding force detection: When the FPC is inserted, an increasing pull force is applied along the pull-out direction of the FPC. The pull force value is collected in real time and the slippage of the FPC relative to the connector is monitored. The pull force value at the moment when the FPC begins to slip is recorded as the measured holding force. The measured holding force is compared with the preset holding force threshold. The holding force is judged to be qualified based on the comparison result. S5. Comprehensive evaluation: The detection results of steps S1, S2, S3 and S4 are comprehensively evaluated according to preset weights, and the output includes at least a qualified and unqualified judgment result.

[0007] Optionally, identifying appearance defects in step S1 includes at least one of terminal misalignment, terminal lifting, shell cracks, and FPC gold finger contamination.

[0008] Optionally, in step S2, the method for determining whether the insertion is in place based on the comparison result is as follows: if the absolute value of the difference between the actual insertion endpoint and the theoretical insertion endpoint is ≤ the first preset deviation threshold, then the insertion is determined to be in place and qualified; if the absolute value of the difference between the actual insertion endpoint and the theoretical insertion endpoint is > the second preset deviation threshold, then the insertion is determined to be in place; if the absolute value of the difference between the actual insertion endpoint and the theoretical insertion endpoint is > the first preset deviation threshold and ≤ the second preset deviation threshold, then it is determined to be in place and needs to be repaired, where the second preset deviation threshold is > the first preset deviation threshold.

[0009] Optionally, the preset derivative threshold value ranges from 0.5 N / mm to 2.0 N / mm, the first preset deviation threshold value ranges from 0.08 mm to 0.15 mm, and the second preset deviation threshold value ranges from 0.25 mm to 0.4 mm.

[0010] Optionally, in step S3, monitoring the electrical signal of the FPC connector involves monitoring the on-resistance of each terminal of the FPC connector. If the on-resistance of any terminal exceeds a preset resistance threshold during micro-vibration excitation, it is determined that an electrical signal interruption has occurred.

[0011] Optionally, in step S4, the preset holding force threshold F0 is determined according to the model of the FPC connector, F0=n×f_p, where n is the number of terminals of the FPC connector and f_p is the rated holding force of a single terminal.

[0012] Optionally, in step S5, the detection results of each detection step are quantified into a score value, with 1 point for passing, 0.5 points for needing repair, and 0 points for failing, and the sum of the weights of each detection step is 1.

[0013] Optionally, in step S5, the weight of the detection result in step S1 is 0.2, the weight of the detection result in step S2 is 0.25, the weight of the detection result in step S3 is 0.30, and the weight of the detection result in step S4 is 0.25; the first threshold is 0.85, and the second threshold is 0.50; the comprehensive evaluation method is as follows: first, the detection results of each detection step are quantified into score values, and then the weighted total score S = 0.2 × S_appearance + 0.25 × S_insertion position + 0.30 × S_contact reliability + 0.25 × S_holding force, where S_appearance, S_insertion position, S_contact reliability, and S_holding force are the score values ​​of each detection step; if S ≥ 0.85, the output is qualified; if 0.50 ≤ S < 0.85, the output is to be repaired; if S < 0.50, the output is unqualified.

[0014] In summary, this application includes at least one of the following beneficial technical effects: First, this invention integrates four inspection dimensions—appearance inspection, insertion position inspection, contact reliability inspection, and retention force inspection—into a single, coherent online inspection method. This enables multi-dimensional quality inspection to be completed simultaneously during the FPC connector assembly process, eliminating the need to transfer products to multiple inspection stations. This significantly improves inspection efficiency and represents an upgrade from offline sampling inspection to online full inspection.

[0015] Second, this invention proposes a contact reliability testing method targeting the flexible characteristics of FPC. By applying controllable micro-vibration excitation to the FPC in the insertion state and simultaneously monitoring the conduction resistance in real time, the potential contact defects caused by the flexibility of the FPC are exposed as instantaneous electrical signal interruption under micro-vibration excitation, thus realizing the effective detection of the hidden defect of "visually qualified but actually poor contact".

[0016] Third, this invention proposes an insertion positioning detection method based on force-displacement curves. By analyzing the change of the first derivative of the insertion thrust in the force-displacement curve, the actual insertion endpoint is accurately determined by the point of sudden increase in thrust. This effectively eliminates displacement measurement errors caused by the flexible deformation of the FPC and improves the accuracy and reliability of insertion positioning detection.

[0017] Fourth, this invention establishes a four-level comprehensive evaluation system, which weights and integrates the results of the four detection dimensions to output three-level judgment results: qualified, needing repair, and unqualified. This not only avoids the product rejection caused by misjudgment in a single dimension, but also provides differentiated processing paths for products of different quality levels, thereby improving production efficiency and product utilization. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall process of the present invention. Detailed Implementation

[0019] The terminology used in the following embodiments is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification and appended claims of this application, the singular expressions “a,” “an,” “the,” “the,” “the,” and “this” are intended to also include expressions such as “one or more,” unless the context clearly indicates otherwise. It should also be understood that in the following embodiments of this application, “at least one” and “one or more” refer to one, two, or more than two. The term “and / or” is used to describe the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can indicate: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character “ / ” generally indicates that the preceding and following related objects are in an “or” relationship.

[0020] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0021] The following is in conjunction with the appendix Figure 1 The present invention will be described in further detail below. Example 1

[0022] This application discloses a comprehensive inspection method for the assembly quality of FPC connectors, which is applied to an automated assembly production line for FPC connectors. The production line includes a conveying mechanism, a vision inspection module, an insertion actuator, a force sensor, a displacement sensor, a vibration exciter, an electrical signal acquisition module, a pull-out force application mechanism, and an industrial control computer.

[0023] Reference Figure 1 The comprehensive inspection method for FPC connector assembly quality in this embodiment includes the following steps: Step S1 is the appearance inspection. Before the FPC is inserted into the connector housing, the appearance image data of the FPC connector is acquired through multi-angle visual inspection. Specifically, after the conveyor transports the connector housing to the appearance inspection station, the industrial control computer controls three industrial cameras to acquire images of the connector housing from the front view, top view, and side view, respectively. After the acquisition is completed, the industrial control computer runs a visual inspection algorithm to identify the acquired images. The identified content includes at least one of the following appearance defects: whether the terminals are misaligned, whether the terminals are floating, whether the housing is cracked, and whether the FPC gold fingers are contaminated. If any of the above appearance defects are detected, the appearance inspection result is unqualified; if no appearance defects are detected, the appearance inspection result is qualified.

[0024] Step S2 is the insertion completion detection. During the insertion of the FPC into the connector housing, force and displacement sensors collect insertion thrust and displacement data, respectively. The industrial control computer generates a force-displacement curve with insertion thrust as the vertical axis and displacement as the horizontal axis. This force-displacement curve reflects the change in insertion resistance with insertion displacement during the insertion of the FPC into the connector housing.

[0025] In the initial stage of FPC insertion, the gold fingers of the FPC have not yet entered the terminal contact area of ​​the housing, and the insertion thrust is small and changes gradually. As the insertion displacement increases, the FPC gold fingers gradually enter the housing and begin to contact the terminal spring tabs, and the insertion thrust gradually increases. When the FPC is inserted to the bottom of the housing, the reinforcing plate end face of the FPC contacts the limiting surface of the housing, and the insertion thrust suddenly increases.

[0026] The industrial control computer calculates the first derivative of the insertion thrust in the force-displacement curve in real time. When the first derivative first exceeds a preset derivative threshold, it is determined that the FPC has been inserted to the bottom of the housing, and the displacement value corresponding to that moment is taken as the actual insertion endpoint. In this embodiment, the preset derivative threshold is 1.0 N / mm. It should be noted that the preset derivative threshold can be selected within the range of 0.5 N / mm to 2.0 N / mm depending on the structural characteristics of different FPC connector models. When the FPC is thinner and the insertion resistance is lower, a smaller threshold can be selected; when the FPC is thicker and the insertion resistance is higher, a larger threshold can be selected.

[0027] The industrial control computer compares the actual insertion endpoint with the theoretical insertion endpoint. The theoretical insertion endpoint is predetermined based on the FPC connector model and stored in the industrial control computer. If the absolute value of the difference between the actual and theoretical insertion endpoints is less than or equal to a first preset deviation threshold, the insertion is considered successful. In this embodiment, the first preset deviation threshold is 0.10 mm. If the absolute value of the difference between the actual and theoretical insertion endpoints is greater than the first preset deviation threshold and less than or equal to a second preset deviation threshold, the connector is considered to require repair. In this embodiment, the second preset deviation threshold is 0.30 mm. If the absolute value of the difference between the actual and theoretical insertion endpoints is greater than the second preset deviation threshold, the connector is considered incompletely inserted, i.e., unsuccessful.

[0028] Step S3 is the contact reliability test. With the FPC in the inserted state (i.e., after the FPC has been inserted to its actual insertion endpoint in step S2), a micro-vibration excitation is applied to the FPC connector using a vibration exciter. The amplitude A of the micro-vibration excitation is 0.08 mm, and the vibration frequency f is 30 Hz. The duration of the micro-vibration excitation is 2 seconds.

[0029] In this embodiment, the FPC connector is a 10-pin specification, and the FPC thickness is 0.3 mm. The amplitude A of the micro-vibration excitation is determined experimentally based on the FPC connector model. For the 10-pin FPC connector, the experimental calibration process is as follows: starting with an initial amplitude of 0.02 mm, the amplitude is gradually increased in steps of 0.01 mm. Vibration is maintained for 2 seconds at each amplitude while simultaneously monitoring the on-resistance. When the amplitude reaches 0.08 mm, the on-resistance does not experience a momentary interruption exceeding 50 milliohms during continuous vibration, and inspection reveals no damage to the FPC and connector terminals. Therefore, 0.08 mm is determined as the minimum effective detection amplitude for this type of FPC connector. The experimental calibration also confirmed that slight wear occurs on the surface of the FPC gold fingers when the amplitude exceeds 0.12 mm. Therefore, the upper limit of the amplitude is determined to be 0.10 mm to allow for a safety margin.

[0030] During the continuous micro-vibration excitation, the electrical signal acquisition module continuously monitors the continuity resistance of each terminal of the FPC connector. The industrial control computer sets the preset resistance threshold to 50 milliohms. If the continuity resistance of any terminal exceeds 50 milliohms during the micro-vibration excitation, it is determined that an electrical signal interruption has occurred at that moment, and the contact reliability test result is unqualified. If the continuity resistance of all terminals does not exceed 50 milliohms during the entire micro-vibration excitation period, the contact is considered reliable, and the contact reliability test result is qualified.

[0031] Step S4 is the holding force detection. After completing the contact reliability detection, i.e., while the FPC is still in the inserted state, a linearly increasing pull-out force is applied along the FPC pull-out direction by a pull-out force application mechanism. In this embodiment, the pull-out force increment rate V is 1.0 Newtons per second. The pull-out force application mechanism can be a servo motor-driven lead screw mechanism or a pneumatic proportional valve-controlled cylinder mechanism, as long as it can achieve a linearly increasing pull-out force output.

[0032] During the increasing pull-out force, the displacement sensor continuously monitors whether the FPC slips relative to the connector. The industrial control computer acquires the pull-out force value in real time and records the pull-out force value at the moment when the FPC begins to slip as the measured holding force F. The measured holding force F is then compared with the preset holding force threshold F0.

[0033] The preset holding force threshold F0 is determined based on the FPC connector model, where F0 = n × f_p, n is the number of terminals on the FPC connector, and f_p is the rated holding force of a single terminal. In this embodiment, the FPC connector is a 10-pin specification, i.e., n = 10, and the rated holding force f_p of a single terminal is 0.3 Newtons, so F0 = 10 × 0.3 = 3.0 Newtons. If F ≥ 3.0 Newtons, the holding force is considered qualified; if F < 3.0 Newtons, the holding force is considered unqualified.

[0034] Step S5 is a comprehensive evaluation. The industrial control computer performs a comprehensive evaluation of the detection results from steps S1 to S4 according to preset weights.

[0035] First, the test results of each testing step are quantified into a score. The quantification rule is: 1 point for passing, 0 points for failing, and 0.5 points for needing repair.

[0036] Then, the weighted total score is calculated according to the following weights: the weight of the appearance inspection result is 0.2, the weight of the insertion position inspection result is 0.25, the weight of the contact reliability inspection result is 0.30, and the weight of the holding force inspection result is 0.25. The weights assigned above are based on the following criteria: Contact reliability directly determines the electrical conductivity of the FPC connector. The main function of the FPC connector is to transmit electrical signals. Poor contact will lead to signal transmission interruption or signal quality degradation, so it is assigned the highest weight of 0.30. Retention force determines the connection retention capability of the FPC connector when subjected to external force. Insufficient retention force will cause the FPC to fall off unexpectedly under external force, resulting in equipment failure, so it is assigned a weight of 0.25. Insertion position determines the contact depth and contact area between the terminal and the spring. Incomplete insertion will lead to increased contact resistance and signal attenuation, so it is assigned a weight of 0.25. Appearance defects include terminal misalignment, terminal floating, shell cracks, and FPC gold finger contamination. Appearance defects usually only affect the appearance quality of the product and the reliability of subsequent welding processes. Among the four dimensions, the impact on the electrical and mechanical connection functions of the product is relatively small, so it is assigned a weight of 0.20.

[0037] The formula for calculating the weighted total score is: S = 0.2 × S_appearance + 0.25 × S_insertion position + 0.30 × S_contact reliability + 0.25 × S_retention force S_appearance, S_insertion position, S_contact reliability, and S_holding force are the scores for each testing step.

[0038] Finally, based on the weighted total score S, a three-level judgment result is output: if S≥0.85, the product is output as qualified; if 0.50≤S<0.85, the product is output as needing repair; if S<0.50, the product is output as unqualified. Qualified products proceed to the next process; products requiring repair are sent to the repair station for manual or automatic repair; unqualified products are sent to the scrap collection area.

[0039] In this embodiment, the order of the detection steps is as follows: appearance inspection is performed before insertion accuracy inspection, insertion accuracy inspection is performed before contact reliability inspection, and contact reliability inspection is performed before holding force inspection. Performing appearance inspection before FPC insertion avoids the FPC partially obscuring the surface of the housing after insertion, thus affecting the accuracy of the appearance inspection. The order of insertion accuracy inspection, contact reliability inspection, and holding force inspection is because: insertion accuracy inspection requires dynamic data during FPC insertion and must be completed during the insertion process; contact reliability inspection needs to be performed when the FPC is in a stable insertion state; and holding force inspection needs to be performed after contact reliability inspection to avoid applying pull-out force first, which could affect the contact state of the FPC and thus interfere with the contact reliability inspection results.

[0040] The above comprehensive evaluation steps are automatically executed by the industrial control computer, which then outputs the judgment results. The industrial control computer has a pre-installed parameter database for various FPC connector models, including parameters such as theoretical insertion endpoint, preset derivative threshold, first preset deviation threshold, second preset deviation threshold, preset resistance threshold, rated holding force of a single terminal, and micro-vibration excitation amplitude calibration value. When the production line changes product models, operators only need to select the corresponding product model on the industrial control computer's human-machine interface, and the industrial control computer automatically retrieves the relevant parameters, eliminating the need for manual setting. Example 2

[0041] The difference between this embodiment and Embodiment 1 is that the FPC connector in this embodiment is a 4-pin ultra-thin FPC connector, and the thickness t of the FPC is 0.2 mm.

[0042] In step S2, the insertion position detection is performed. The preset derivative threshold is 0.8 Newtons per millimeter, the first preset deviation threshold is 0.08 millimeters, and the second preset deviation threshold is 0.25 millimeters.

[0043] In step S3, contact reliability testing, the micro-vibration excitation amplitude A for this type of FPC connector was determined to be 0.06 mm, the vibration frequency f to be 40 Hz, and the duration to be 1.5 seconds through experimental calibration. The experimental calibration process was as follows: starting with an initial amplitude of 0.02 mm, the amplitude was gradually increased in increments of 0.01 mm. Vibration was maintained for 1.5 seconds at each amplitude while simultaneously monitoring the conduction resistance. When the amplitude reached 0.06 mm, the conduction resistance did not experience any momentary interruption exceeding 40 milliohms during continuous vibration. Therefore, 0.06 mm was determined as the minimum effective detection amplitude for this type of FPC connector. The preset resistance threshold was 40 milliohms.

[0044] In step S4, the holding force detection, the rate of increase of the pull-out force V is 0.8 Newtons per second. F0 = n × f_p = 4 × 0.25 = 1.0 Newtons, where the rated holding force f_p of a single terminal is 0.25 Newtons.

[0045] The remaining steps and parameters are the same as in Example 1. Example 3

[0046] The difference between this embodiment and Embodiment 1 is that the FPC connector in this embodiment is a 20-pin high-density FPC connector, and the thickness t of the FPC is 0.4 mm.

[0047] In step S2, the insertion position detection is performed. The preset derivative threshold is 1.5 Newtons per millimeter, the first preset deviation threshold is 0.15 millimeters, and the second preset deviation threshold is 0.40 millimeters.

[0048] In step S3, contact reliability testing, the micro-vibration excitation amplitude A for this type of FPC connector was determined to be 0.10 mm, the vibration frequency f to be 20 Hz, and the duration to be 3 seconds through experimental calibration. The experimental calibration process was as follows: starting with an initial amplitude of 0.02 mm, the amplitude was gradually increased in increments of 0.01 mm. Vibration was maintained for 3 seconds at each amplitude while simultaneously monitoring the continuity resistance. When the amplitude reached 0.10 mm, the continuity resistance did not experience any momentary interruption exceeding 60 milliohms during continuous vibration. Therefore, 0.10 mm was determined as the minimum effective detection amplitude for this type of FPC connector. The preset resistance threshold was 60 milliohms.

[0049] In step S4, the holding force detection, the rate of increase of the pull-out force V is 1.5 Newtons per second. F0 = n × f_p = 20 × 0.4 = 8.0 Newtons, where the rated holding force f_p of a single terminal is 0.4 Newtons.

[0050] The remaining steps and parameters are the same as in Example 1. Example 4

[0051] The difference between this embodiment and Embodiment 1 lies in the weighting allocation in the comprehensive evaluation. In this embodiment, the FPC connector is used in a high-frequency signal transmission scenario, where contact reliability has a more significant impact on signal quality. Therefore, the weighting allocation is adjusted as follows: the weight of the appearance inspection result is 0.15, the weight of the insertion position inspection result is 0.25, the weight of the contact reliability inspection result is 0.35, and the weight of the holding force inspection result is 0.25. The basis for this weighting allocation is that in high-frequency signal transmission applications, even a small change in contact resistance can lead to increased signal reflection and insertion loss; therefore, the weight of contact reliability is increased from 0.30 to 0.35. Appearance defects have a relatively small impact on high-frequency signal transmission performance; therefore, the weight of appearance inspection results is decreased from 0.20 to 0.15.

[0052] The formula for calculating the weighted total score is: S = 0.15 × S_appearance + 0.25 × S_insertion position + 0.35 × S_contact reliability + 0.25 × S_retention force The thresholds for the Level 3 judgment results are the same as in Example 1: S≥0.85 is qualified, 0.50≤S<0.85 is to be repaired, and S<0.50 is unqualified.

[0053] The remaining steps and parameters are the same as in Example 1. Example 5

[0054] The difference between this embodiment and Embodiment 1 is that in step S3, contact reliability testing, the amplitude A of the micro-vibration excitation is not determined through experimental calibration, but is directly retrieved from the parameter database of the industrial control computer based on the FPC connector model. For different FPC connector models, the applicable micro-vibration excitation amplitude is pre-calibrated through type testing before leaving the factory and stored in the database. In this embodiment, the pre-stored amplitude value for a 4-pin FPC connector is 0.05 mm, for a 10-pin FPC connector it is 0.08 mm, and for a 20-pin FPC connector it is 0.10 mm.

[0055] The remaining steps and parameters are the same as in Example 1.

[0056] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Any equivalent modifications or variations made by those skilled in the art based on the content disclosed in the present invention should be included within the scope of protection set forth in the claims.

Claims

1. A comprehensive inspection method for the assembly quality of FPC connectors, characterized in that, Includes the following steps: S1. Appearance inspection: Before the FPC is inserted into the connector housing, the appearance image data of the FPC connector is obtained through multi-angle visual inspection to identify appearance defects. S2. Insertion in place detection: During the process of inserting the FPC into the connector housing, the insertion thrust and displacement data are collected to generate a force-displacement curve. The displacement value corresponding to the first time the first derivative of the insertion thrust in the force-displacement curve exceeds the preset derivative threshold is taken as the actual insertion endpoint. The actual insertion endpoint is compared with the theoretical insertion endpoint, and the insertion is determined based on the comparison result. S3. Contact reliability test: When the FPC is in the inserted state, apply micro-vibration excitation to the FPC connector. The amplitude of the micro-vibration excitation is A, and the value of A ranges from 0.05 mm to 0.10 mm. During the continuous micro-vibration excitation, continuously monitor the electrical signal of the FPC connector. Determine whether the contact is reliable based on whether there is a momentary interruption in the electrical signal. S4. Holding force detection: When the FPC is inserted, an increasing pull force is applied along the pull-out direction of the FPC. The pull force value is collected in real time and the slippage of the FPC relative to the connector is monitored. The pull force value at the moment when the FPC begins to slip is recorded as the measured holding force. The measured holding force is compared with the preset holding force threshold. The holding force is judged to be qualified based on the comparison result. S5. Comprehensive evaluation: The detection results of steps S1, S2, S3 and S4 are comprehensively evaluated according to preset weights, and the output includes at least a qualified and unqualified judgment result.

2. The comprehensive inspection method for FPC connector assembly quality according to claim 1, characterized in that: The appearance defects identified in step S1 include at least one of terminal misalignment, terminal floating, shell cracks, and FPC gold finger contamination.

3. The comprehensive inspection method for FPC connector assembly quality according to claim 1, characterized in that: In step S2, the method for determining whether the insertion is in place based on the comparison result is as follows: if the absolute value of the difference between the actual insertion endpoint and the theoretical insertion endpoint is ≤ the first preset deviation threshold, the insertion is determined to be in place and qualified; if the absolute value of the difference between the actual insertion endpoint and the theoretical insertion endpoint is > the second preset deviation threshold, the insertion is determined to be in place; if the absolute value of the difference between the actual insertion endpoint and the theoretical insertion endpoint is > the first preset deviation threshold and ≤ the second preset deviation threshold, the insertion is determined to be in place and needs to be repaired, where the second preset deviation threshold is > the first preset deviation threshold.

4. The comprehensive inspection method for FPC connector assembly quality according to claim 3, characterized in that: The preset derivative threshold value ranges from 0.5 N / mm to 2.0 N / mm, the first preset deviation threshold value ranges from 0.08 mm to 0.15 mm, and the second preset deviation threshold value ranges from 0.25 mm to 0.4 mm.

5. The comprehensive inspection method for FPC connector assembly quality according to claim 1, characterized in that: In step S3, the electrical signal of the FPC connector is monitored by monitoring the on-resistance of each terminal of the FPC connector. If the on-resistance of any terminal exceeds a preset resistance threshold during micro-vibration excitation, it is determined that an electrical signal interruption has occurred.

6. The comprehensive inspection method for FPC connector assembly quality according to claim 1, characterized in that: In step S4, the preset holding force threshold F0 is determined according to the model of the FPC connector, F0=n×f_p, where n is the number of terminals of the FPC connector and f_p is the rated holding force of a single terminal.

7. The comprehensive inspection method for FPC connector assembly quality according to claim 1, characterized in that: In step S5, the detection results of each detection step are quantified into a score value: 1 point for passing, 0.5 points for needing repair, and 0 points for failing. The sum of the weights of each detection step is 1.

8. The comprehensive inspection method for FPC connector assembly quality according to claim 1, characterized in that: In step S5, the weight of the detection result in step S1 is 0.2, the weight of the detection result in step S2 is 0.25, the weight of the detection result in step S3 is 0.30, and the weight of the detection result in step S4 is 0.25; the first threshold is 0.85, and the second threshold is 0.50; the comprehensive evaluation method is as follows: first, the detection results of each detection step are quantified into score values, and then the weighted total score S = 0.2 × S_appearance + 0.25 × S_insertion position + 0.30 × S_contact reliability + 0.25 × S_holding force, where S_appearance, S_insertion position, S_contact reliability, and S_holding force are the score values ​​of each detection step, respectively; If S≥0.85, the output is qualified; if 0.50≤S<0.85, the output is to be repaired; if S<0.50, the output is unqualified.

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