CN-122015664-A - Method for detecting solder mask deviation of printed circuit board

CN122015664ACN 122015664 ACN122015664 ACN 122015664ACN-122015664-A

Abstract

The invention discloses a method for detecting solder mask deviation of a printed circuit board, which relates to the technical field of printed circuit boards and solves the problem that single-wavelength laser scanning or contact thickness measuring methods are commonly adopted in solder mask thickness detection, and single-wavelength laser is easy to be interfered by the surface evenness of a solder mask layer; the method does not need to rely on an additional reference area, avoids the defect that the traditional single-wavelength laser detection is affected by surface reflection and ink color, ensures that only the flat point positions are subjected to thickness calculation through angle matching, further improves the accuracy of thickness detection, and provides reliable data support for accurate judgment of thin areas and thick areas.

Inventors

QIAN JIANGHUI
ZENG FENG

Assignees

博罗县鸿源华辉电子有限公司

Dates

Publication Date: 20260512
Application Date: 20260121

Claims (8)

1. The method for detecting the solder mask deviation of the printed circuit board is characterized by comprising the following steps of: Firstly, performing machine vision scanning treatment on a printed circuit board after finishing the solder resist oil film coating treatment, confirming RGB values associated with different points, performing sum verification treatment on the RGB values, confirming RGB features associated with different points, and performing point location partition planning based on the RGB features to divide the surface area of the printed circuit board into a base material area or a solder resist area; Performing laser displacement scanning treatment on the marked solder mask area, performing scanning process by adopting lasers with different wavelengths, recording the rebound position of each reflection line, locking reflection fold lines with different wavelengths at the same reflection position, locking solder mask reflection points and substrate reflection points based on angle characteristics, and further confirming the solder mask thickness of the corresponding points; And thirdly, based on different solder resist thicknesses associated with different points in the solder resist area, confirming abnormal characteristics associated with different solder resist areas, marking, and displaying marked processed images.
2. The method for detecting solder mask bias of a printed circuit board according to claim 1, wherein in the first step, the specific manner of dividing the surface area of the printed circuit board into the base material area or the solder mask area is as follows: Performing visual scanning processing on the printed circuit board, confirming RGB values associated with different points in the printed circuit board, performing summation processing on the RGB values associated with the corresponding points, confirming the RGB total value associated with the corresponding points, and marking as Z i , wherein i represents different points; Comparing and checking the related total value Z i with a preset numerical value interval, wherein the numerical value interval comprises a substrate interval or a welding resistance interval, the endpoint values of the two groups of intervals are preset values, if Z i belongs to the substrate interval, the corresponding point position is marked as a substrate point position, if Z i belongs to the welding resistance interval, the corresponding point position is marked as a welding resistance point position, and if Z i does not belong to the substrate interval or the welding resistance interval, no marking is carried out; The area covered by the substrate points is marked as a substrate area, and the area covered by the solder mask points is marked as a solder mask area.
3. The method for detecting solder mask bias of printed circuit board according to claim 1, wherein in the second step, the specific way of executing the scanning process by using the lasers with different wavelengths is as follows: Performing laser displacement scanning treatment on the welding-resistant area by adopting visible light with the wavelength of 550nm, aiming at different point positions in the welding-resistant area, gradually debugging the emission angle A1 of emitted laser to ensure that the laser reflection point accurately falls on the corresponding point position, confirming the reflection line associated with the corresponding generated laser, confirming the falling point of the reflection line on the receiving panel, confirming the included angle A2 generated by the reflection line and the receiving panel, recording the corresponding point position with the identical A1 and the corresponding point position A2 as a flat point position, otherwise, not performing any calibration; For a plurality of groups of leveling points marked in the solder resist area, performing laser displacement scanning treatment on a substrate area below the leveling points by adopting near infrared light with the wavelength of 1350nm, preferentially enabling a reflection point of the near infrared light to fall on the leveling points, gradually expanding the emission angle of the near infrared light downwards, recording the reflection falling point of a reflection line of the near infrared light in real time, stopping when the recorded reflection falling point is at the same point as the reflection falling point of visible light on the leveling points, and recording the current state as a standard state.
4. The method for detecting solder mask bias of printed circuit board according to claim 3, wherein in the second step, the specific means for locking the solder mask reflective point and the substrate reflective point are as follows: Identifying the emitting angle F1 of near infrared light and the emitting angle F2 of visible light in a standard state, then identifying receiving angles J1 and J2 generated by a corresponding reflecting line and a receiving panel, wherein J1 is the reflecting line of the near infrared light, J2 is the reflecting line of the visible light, generating a substrate reflecting point 1 of the near infrared light based on the emitting angle F1 of the near infrared light and the receiving angle J1, then synchronously identifying a welding resistance reflecting point 2 of the visible light, identifying a straight line distance between the substrate reflecting point 1 and the welding resistance reflecting point 2, and sequentially identifying the welding resistance thickness related to each flat point by taking the straight line distance as the welding resistance thickness of the corresponding point.
5. The method for detecting solder mask bias of printed circuit board according to claim 1, wherein in the third step, the specific way of identifying and marking the abnormal feature in the solder mask area is as follows: Identifying the total number of the leveling points in different solder mask areas, if the total number is 1, recording the solder mask thickness associated with the corresponding leveling points as the area characteristics of the current solder mask area, if the total number exceeds 1, carrying out average value processing on the multiple groups of solder mask thicknesses associated with the multiple groups of leveling points in the corresponding area, and taking the average value obtained by processing as the area characteristics associated with the corresponding area; if the area characteristics are less than 5um, the corresponding solder mask areas are marked as thin areas, if the area characteristics are more than 8um, the corresponding solder mask areas are marked as thick areas, and no mark is carried out on the solder mask areas with the area characteristics between 5 and 8 um; and if no leveling point exists in a certain solder resist area, marking the solder resist area as a pending area.
6. The method for detecting solder resist bias of a printed circuit board according to claim 1, further comprising: And fourthly, carrying out feature verification on the printed circuit boards with the abnormal features, identifying abnormal vectors related to the abnormal features in the printed circuit boards, synchronously comparing the abnormal vectors of the identified different printed circuit boards, and identifying whether the abnormal features associated with the printed circuit boards have similar features or not, if so, directly carrying out signal display, and if not, not carrying out any processing.
7. The method for detecting solder mask bias of printed circuit board according to claim 6, wherein in the fourth step, the specific way of confirming the abnormal vector is as follows: Confirming a central point of a printed circuit board and marking the central point as a main point, confirming an associated solder resist area based on abnormal characteristics marked on the surface of the corresponding printed circuit board, confirming the central point of the solder resist area and marking the central point as a secondary point, taking the main point as a starting point, taking the secondary point as an end point, generating abnormal vectors associated with the corresponding solder resist area, and sequentially confirming a plurality of groups of abnormal vectors existing in the printed circuit board; And synchronously confirming the abnormal vectors of other printed circuit boards with abnormal characteristics, and identifying whether similar vectors exist among the abnormal vectors of different printed circuit boards, wherein the tail end points of a certain group of abnormal vectors are used as circle centers, a group of circles with the radius of 1um are constructed, if the tail end points of other abnormal vectors are positioned in the circles constructed by the abnormal vectors, the similar vectors are recorded, if the similar vectors exist, the two groups of printed circuit boards are marked as undetermined circuit boards, otherwise, no marking is carried out.
8. The method for detecting solder mask bias of printed circuit board according to claim 7, wherein in the fourth step, the specific way of identifying the abnormal feature is as follows: and sequentially checking and comparing a plurality of groups of abnormal vectors in the circuit boards to be determined, sequentially marking the similar vectors in the circuit boards to be determined, recording the total number QG of the similar vectors, and then confirming the total number ZG of the abnormal vectors in the corresponding single circuit boards to be determined.

Description

Method for detecting solder mask deviation of printed circuit board Technical Field The invention relates to the technical field of printed circuit boards, in particular to a method for detecting solder mask deviation of a printed circuit board. Background A Printed Circuit Board (PCB) is used as a core interconnection carrier of electronic equipment, and the coating precision of a surface solder mask layer directly determines the insulating performance, the welding reliability and the service life of a product. The thickness uniformity and the position accuracy of the solder mask are core quality control indexes of the solder mask process, namely if the solder mask is too thin, the exposed oxidation of a circuit is easy to cause the risk of short circuit to be improved, if the solder mask is too thick, the solder mask can cover a bonding pad to cause the problem of cold joint and off-joint of components, and the error division of a solder mask area can directly cause the deviation of a detection target area to cause the outflow of batch defective products. In the traditional PCB solder mask detection flow, the area division is mostly dependent on manual visual or single visual threshold segmentation, the mode is greatly influenced by the color, surface reflection and illumination conditions of the ink, the erroneous judgment of a substrate area and a solder mask area is extremely easy to occur, atypical areas cannot be effectively screened, the solder mask thickness detection generally adopts a single-wavelength laser scanning or contact thickness measuring method, the single-wavelength laser is easily interfered by the surface evenness of a solder mask layer, the ink is difficult to penetrate to directly obtain the surface position of the substrate, the additional reference area is required to be relied on for calibration, the defects of low detection efficiency and insufficient precision exist, the contact thickness measuring rule can cause physical damage to the solder mask layer, and the method is not suitable for finished product detection. Meanwhile, the traditional detection method only carries out isolation quality judgment on a single PCB, lacks the correlation analysis capability of commonality abnormality among a plurality of PCBs, and cannot timely identify systematic process problems caused by production equipment defects (such as surface cracks of a compacting plate and alignment deviation of an exposure machine). When the equipment has hidden faults, the source can be traced after batch defective products are accumulated, so that the production loss is greatly increased, and the large-scale production requirement of high-density and high-precision PCBs is difficult to meet. Therefore, it is needed to develop a method for detecting solder mask deviation integrating precise area division, high-precision thickness detection and systematic anomaly traceability, so as to solve the problems of high partition misjudgment rate, low thickness detection precision, weak anomaly traceability and other pain points in the traditional technology and realize full-process closed loop control of the quality of the PCB solder mask process. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a method for detecting the solder mask deviation of a printed circuit board, which solves the problem that single-wavelength laser is easy to be interfered by the surface flatness of a solder mask layer when a single-wavelength laser scanning or contact thickness measuring method is commonly adopted for detecting the solder mask thickness. The invention aims to realize the technical scheme that the method for detecting the solder mask deviation of the printed circuit board comprises the following steps: Firstly, performing machine vision scanning treatment on a printed circuit board after finishing the treatment of the solder resist oil film coating, confirming RGB values associated with different points, performing sum verification treatment on the RGB values, confirming RGB features associated with different points, and performing point location partition planning based on the RGB features to divide the surface area of the printed circuit board into a base material area or a solder resist area, wherein the specific mode is as follows: Performing visual scanning processing on the printed circuit board, confirming RGB values associated with different points in the printed circuit board, performing summation processing on the RGB values associated with the corresponding points, confirming the RGB total value associated with the corresponding points, and marking as Z i, wherein i represents different points; Comparing and checking the related total value Z i with a preset numerical value interval, wherein the numerical value interval comprises a substrate interval or a welding resistance interval, the endpoint values of the two groups of intervals are preset values, if Z i belongs to the sub