A processing method for solving surface ink appearance defects

Abstract

The application discloses a kind of processing methods for solving surface ink appearance defects, comprising: after the coating of ink in PCB processing technology is completed, the PCB is tested, confirm whether there is defect in ink appearance, if there is defect, then determine the defect position;According to the determined ink appearance defect position, determine the abnormal category;According to the abnormal category of the determined ink appearance defect, select the corresponding mode for processing.Abnormal category includes: abnormal category one: BGA conductor line (line and BGA pad spacing ≤5 mil), abnormality of copper exposure on the side of the line;Abnormal category two: dense SMDPAD overdistance soldering line, IC spacing soldering line is not printed down abnormality;Abnormal category three: local shrinkage problem of whole board PCB, local area ink cover green & copper exposure abnormality.The processing method for solving surface ink appearance defects optimizes printing screen & negative data according to different types of appearance abnormalities after production board is made, so as to realize the excellent quality performance of surface ink appearance zero defect, zero loss.

Description

Technical Field

[0001] The invention relates to a processing method for solving surface ink appearance defects, and belongs to the technical field of high-speed multilayer board production. Background Art

[0002] In the PCB manufacturing process, the application of solder mask ink is a critical step. The main function of solder mask ink on PCB boards is to protect the circuits and prevent unnecessary soldering of conductors. It also prevents electrical problems between conductors caused by environmental factors. However, during the manufacturing process, uncontrollable factors can cause surface ink appearance defects (such as exposed copper on the circuit pair, underprinting, ink detachment, etc.). To avoid and reduce the defective product rate, timely treatment is required after inspection. The treatment method must meet customer requirements. There are two common solutions to abnormal ink appearance:

[0003] 1. Re-wash the ink, soak and wash the ink on the entire board, optimize the data and re-produce according to the full solder mask process. Disadvantages: starting from scratch and redoing, the operation is cumbersome and affects the product delivery time;

[0004] 2. Localized single-point repairs are performed on localized defects. This approach presents two difficulties. First, the entire board surface must be marked for processing, with no abnormalities missed, making marking difficult. Second, the abnormal areas must be partially printed according to the defect pattern, and the solder mask screen data must be aligned with the defect pattern size. There is also a risk of printing deviation during printing. This requires strict CAM processing of the screen data, making reprinting difficult and time-consuming.

[0005] It can be seen that in order to solve the problem of ink appearance defects more timely and conveniently, there is an urgent need for a treatment method to solve the surface ink appearance defects without having to repeat the full process of solder mask processing, which causes long processing cycles, difficulty in printing operations and inspection due to local printing, and troubles in ink processing due to abnormal front-end processes. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for solving surface ink appearance defects. After the production board is produced and an abnormality occurs, the printing screen and film data are optimized according to the different types of appearance abnormalities to achieve excellent quality performance with zero defects and zero omissions in the surface ink appearance.

[0007] In order to achieve the above objectives / solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0008] A method for solving surface ink appearance defects, comprising:

[0009] After the ink coating is completed in the PCB processing process, the PCB is inspected to confirm whether there is a defect in the appearance of the ink, and if there is a defect, the defect position is determined;

[0010] According to the determined ink appearance defect position, the abnormal type is determined;

[0011] According to the determined abnormal type of the ink appearance defect, a corresponding method is selected for processing.

[0012] Further, the abnormal type includes:

[0013] Abnormal type one: BGA conductor line (line and BGA pad spacing ≤5 mil), abnormal copper exposure on the side of the line;

[0014] Abnormal type two: dense SMD pad spacing soldering line (IC area original spacing ≤8 mil), IC spacing soldering line is not printed down;

[0015] Abnormal type three: local expansion and contraction problem of the whole board PCB, local area ink cover green & copper exposure abnormality.

[0016] Further, the defect processing method of abnormal type one and abnormal type two includes:

[0017] Confirm the main failure type of the abnormal area, use the printing screen to select the distance soldering window on the original board, respectively make the window single side +2Amil ink leakage, the abnormal area is fully covered and printed, the printing machine uses 50 times magnifying glass to check whether there is printing deviation; The KE exposure data remains unchanged, and the LDI machine with better alignment performance is used for exposure operation, and the surface ink is normally inspected after development.

[0018] Further, the defect processing method of abnormal type one and abnormal type two includes:

[0019] The IC printing screen ink leakage point is made according to the IC pad working document, and the soldering window single side +4mil is made, wherein the IC ink leakage point edge is coincided and connected together to make integral ink leakage.

[0020] Further, the defect processing method of abnormal type three includes:

[0021] The single side shrinkage abnormality of the board is deformed, taking the abnormal side as the reference, measuring the single direction average zoom of the abnormal side, the CAM first shrinks and stretches the whole pattern, then adjusts the single side average shrinkage value of the KE optical alignment point, and then performs 1:1 equal proportion PCS internal pattern pre-release data to form the formal working document data.

[0022] Further, the defect processing method of abnormal type three includes:

[0023] The printing DSR screen design is unchanged;

[0024] The second adjustment of the CAM exposure data needs to be pre-released in proportion to the optical positioning point and the in-plate pattern data, the out-of-plate data is guaranteed to be 100% pre-released, the in-PCS pattern is pre-released accordingly, and the consistency of the out-of-plate data and the in-PCS pre-release is guaranteed.

[0025] Further, after selecting the corresponding mode for processing according to the determined abnormal type of the ink appearance defect, further comprising:

[0026] After obtaining the defect-free PCB through corresponding processing, the PCB finished product is obtained through back surface treatment and outer shape;

[0027] The obtained PCB finished product is subjected to functional test, and the functional test includes electrical performance and reliability test.

[0028] Further, the PCB processing process comprises:

[0029] According to the structure of the circuit board, the corresponding inner layer plate is made, the inner layer dry film is pressed, the image is transferred by the inner layer exposure machine, the acid etching is used, and the inner layer pattern is etched on each inner layer substrate;

[0030] According to the sequence of the circuit board structure, the substrate and the adhesive sheet are stacked on the press platform in sequence by using the adhesive sheet, and the circuit board is pressed together by using the hot press;

[0031] The Via hole for connecting the circuit is drilled on the pressed circuit board by using the drilling machine;

[0032] Chemical copper deposition and electroplating copper are carried out to deposit a specified copper thickness on the Via hole wall;

[0033] According to the circuit diagram, the outer layer pattern is made by using full-plate image or pattern electroplating image transfer;

[0034] The circuit board is pre-processed into a clean room for printing, after printing, short baking, and normal exposure according to the CAM data, the circuit board is put into the ink developing line for ink window development, and after the pattern development, UV curing is carried out.

[0035] Compared with the prior art, the beneficial effects achieved by the present application are:

[0036] The processing method for solving the surface ink appearance defect provided by the present application optimizes the printing screen & film data according to different types of appearance abnormalities after the production plate is made, so as to realize the excellent quality performance of zero defect and zero loss of surface ink appearance;

[0037] The processing method for solving surface ink appearance defects provided by the application has obvious improvement in timeliness and success rate in abnormal processing complexity (abnormal point identification and CAM printing screen data) and simplifies processing complexity (abnormal point identification and CAM printing screen data).

[0038] The processing method for solving surface ink appearance defects provided by the application has obvious improvement in timeliness and success rate in abnormal processing complexity (abnormal point identification and CAM printing screen data) and simplifies processing complexity (abnormal point identification and CAM printing screen data).

[0039] The processing method for solving surface ink appearance defects provided by the application has obvious improvement in timeliness and success rate in abnormal processing complexity (abnormal point identification and CAM printing screen data) and simplifies processing complexity (abnormal point identification and CAM printing screen data). BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a schematic diagram of a PCB processing process;

[0041] Figure 2 It is a structural schematic diagram of abnormal type one;

[0042] Figure 3 It is a structural schematic diagram of abnormal type two;

[0043] Figure 4 It is a structural schematic diagram of abnormal type three;

[0044] Figure 5 It is a processing schematic diagram of abnormal type one;

[0045] Figure 6 It is a processing schematic diagram of abnormal type two;

[0046] Figure 7 It is a processing schematic diagram of abnormal type three. DETAILED DESCRIPTION

[0047] The application will be further described below in combination with the drawings. The following examples are only used to more clearly illustrate the technical solutions of the application, and cannot be used to limit the protection scope of the application.

[0048] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0049] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances. Example 1

[0050] This embodiment provides a method for resolving surface ink appearance defects, including:

[0051] After the PCB processing process completes the ink coating, the PCB is inspected to confirm whether there are any defects in the ink appearance. If there are defects, the defect location is determined;

[0052] Determine the type of abnormality based on the determined location of the ink appearance defect;

[0053] According to the determined abnormal type of ink appearance defect, a corresponding method is selected for processing.

[0054] Among them, the inspection method includes: after the surface ink is completed, it is sent to the quality assurance for inspection. The quality assurance will mark the location of the ink appearance defects and notify the technicians to confirm the type of abnormality, and distinguish the three main categories:

[0055] Abnormal type 1: such as Figure 2 As shown in the image, the BGA conductor line (the spacing between the line and the BGA pad is ≤5mil) has abnormal copper exposure on the side of the line. This mainly occurs in the area between the window pad and the line ink. The copper exposure problem on the side of the line is caused by the exposure offset.

[0056] Abnormal type two: as shown in Figure 3 , dense SMD PAD span soldering wire (IC area original manuscript distance ≤8mil), IC span soldering wire does not print down abnormal, mainly appears in IC area, because the distance between dense PAD is small, printing is easy to have ink jump printing problem, leading to not printing down abnormal;

[0057] Abnormal type three: as shown in Figure 4 , local expansion problem of whole board PCB, local area ink cover green & copper exposure abnormal, mainly appears in local area of board surface, because the local expansion deformation of board, according to the original negative material production, leading to abnormal cover green & copper exposure of board.

[0058] The defect treatment method of abnormal type one and abnormal type two includes:

[0059] As shown in Figure 5 and Figure 6 , confirm the main failure type of abnormal area (copper exposure, not printing down, etc.), use the printing screen to select the distance soldering window in the original board, respectively make the window single side +2Amil ink leakage, abnormal area full coverage printing, printing machine hand uses 50 times magnifying glass to check whether there is printing deviation; KE exposure data is unchanged, use LDI machine with better alignment performance to expose operation, normal inspection after surface ink development.

[0060] Abnormal type one & two operation parameters:

[0061] Overprint job parameters Normal case After optimization adjustment Missed dot size 3A X+2A Overprint shape Rectangle (only abnormal area) BGA circle / SMD rectangle Screen mesh B B Printing speed (m / min) C C Squeegee pressure (bar) D D Ink viscosity (dps) E E Exposure job parameters Automatic exposure machine LDI

[0062] Note:

[0063] X is the size of BGA or SMD window single side;

[0064] A is the distance between BGA and wire or the width of SMD and SMD span soldering wire.

[0065] Among them, the printing remediation operation parameters are as follows:

[0066] Category Dense position pitch Screen mesh Ink viscosity (dps) Squeegee pressure (bar) Printing speed (m / min) Category ① 5 mil 200 80±20 5~7 2~3 Category ② 8 mil 200 80±20 5~7 2~3

[0067] Notes:

[0068] 1. Exposure data: original normal exposure data;

[0069] 2. BGA printing screen production selects the soldering window in the original board, makes the soldering window single side +5mil ink leakage;

[0070] 3. IC printing screen ink leakage point is made according to IC Pad working document soldering window single side +4mil (IC ink leakage point edge overlap together to make integral ink leakage).

[0071] The third abnormality type defect processing method comprises:

[0072] As shown in Figure 7 , the board is abnormally deformed by unilateral shrinkage, and the abnormal side is measured by unilateral average scaling (normal case: centering bilateral scaling), CAM first performs overall pattern shrinkage, and then performs unilateral average scaling of KE optical alignment points, and then performs 1:1 equal proportion PCS inner pattern pre-release data after adjustment to form the formal working document.

[0073] The third abnormality type operation parameter:

[0074] Among them, the CAM exposure data is as follows:

[0075] Notes:

[0076] 1. The DSR screen printing design does not change;

[0077] 2. The second adjustment of the CAM exposure data needs to be pre-released in proportion to the optical positioning point and the inner plate data, and the outer plate data is guaranteed to be 100% pre-released, and the corresponding pre-release is performed on the inner plate pattern to ensure the consistency of the outer plate data and the inner plate pre-release.

[0078] After selecting the corresponding mode for processing according to the determined abnormality type of the ink appearance defect, it further comprises:

[0079] After obtaining the defect-free PCB through corresponding processing, the PCB product is obtained through back surface treatment and shape fishing;

[0080] The obtained PCB product is subjected to functional test, and the functional test comprises electrical performance and reliability test.

[0081] In the above processing mode, the reverse thinking mode is used to solve the abnormal problem; wherein, the first and second abnormality types are not limited to single-point repair of abnormal areas, but enlarge the abnormal repair area, so that the problem of difficult identification of abnormal points and difficult processing of CAM screen data can be overcome; the third abnormality type is abnormal shrinkage of inner plate pattern, which is not directly adjusted to the exposure data of the inner plate pattern, but is adjusted to the KE outer optical positioning point first, and then the inner plate pattern is pre-released in proportion, so that the difficult operation problem caused by local adjustment of the exposure data of the inner plate pattern at multiple positions can be overcome.

[0082] As shown in Figure 1 , the PCB processing process comprises:

[0083] Inner layer substrate manufacturing: manufacture corresponding inner layer substrate according to the structure of the circuit board, transfer the image by inner layer dry film pressing and inner layer exposure machine, and etch the inner layer pattern on each inner layer substrate by using acid etching;

[0084] Inner layer substrate pressing: according to the order of the circuit board structure, the substrates and the adhesive sheets are stacked in order on the platform of the pressing machine using the adhesive sheets, and the circuit boards are pressed together using a hot press;

[0085] Outer layer drilling: a via hole for circuit connection is drilled on the pressed circuit board using a drilling machine;

[0086] Outer layer copper deposition and electroplating: chemical copper deposition and electroplating are performed to deposit a specified copper thickness on the via hole wall;

[0087] Outer layer circuit fabrication: outer layer patterns are fabricated according to the circuit diagram using full-board imaging or pattern electroplating imaging transfer;

[0088] Outer layer solder mask fabrication: the circuit board is pretreated and then enters a clean room for printing, after printing, short baking, and normal exposure according to CAM data, the circuit board is placed into an ink developing line for ink window development, and after pattern development, UV curing is performed.

[0089] In summary, the processing method for solving surface ink appearance defects provided by the embodiment optimizes the printing screen and film data according to different types of appearance abnormalities after the production board is fabricated and abnormal, so as to realize zero defects and zero loss of the appearance of the surface ink, and excellent quality performance; Specifically, in terms of product design, for the BGA conductor line (pitch ≤ 5 mil) and dense SMD area (pitch ≤ 8 mil) on the outer layer and the ink soldering requirement, after the abnormality is identified by the operation completion inspection, the remedial rework processing is arranged, the processing complexity (abnormal point identification and CAM printing screen data) is simplified, and the timeliness and success rate of abnormal processing are obviously improved; In terms of abnormal processing capacity, for the pattern shrinkage abnormality of the front station, the soldering station overcomes the influence of the front station process by adjusting the soldering exposure data, has inclusiveness in problem processing, reduces the scrap rate, and ensures the product delivery yield; In terms of assembly, the ink appearance is beautiful, avoids ink defect loss, reduces the risk of soldering failure in assembly, and the product reliability is good.

[0090] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the technical field, several improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A method for solving surface ink appearance defects, characterized in that: include: After the PCB processing process completes the ink coating, the PCB is inspected to confirm whether there are any defects in the ink appearance. If there are defects, the defect location is determined; Determine the type of abnormality based on the determined location of the ink appearance defect; Select the corresponding method to handle the abnormality according to the determined type of ink appearance defect; The types of exceptions include: Abnormality type 1: BGA conductor line, copper exposed on the side of the line is abnormal, among which the BGA conductor line is the distance between the line and the BGAPad ≤ 5mil; Abnormal type 2: dense SMDPAD over-pitch wire bonding, IC spacing wire bonding is not printed abnormally. Among them, dense SMDPAD over-pitch wire bonding means that the original spacing of the IC area is ≤8mil; Abnormality type 3: Local expansion and contraction of the entire PCB, abnormal green ink coverage and exposed copper in local areas; The defect handling methods for exception type 1 and exception type 2 include: Confirm the failure type of the abnormal area, use the overprinting screen to select the part of the original board away from the welding window, and make the ink leakage of +2Amil on each side of the window. Fully cover the abnormal area with printing. During printing, use a 50x magnifying glass to check for printing deviation. Keep the KE exposure data unchanged, and use the LDI machine with better alignment performance for exposure. After the surface ink is developed, check if it is normal. The defect handling method for abnormal type 3 includes: When the board is abnormally deformed due to shrinkage on one side, the average unidirectional scaling of the abnormal side is measured with the side without abnormality as the benchmark. CAM first shrinks and shrinks the entire graphic, and then performs unilateral average shrinkage on the KE optical alignment point. After adjustment, the graphic pre-release data in the PCS is performed at a 1:1 ratio to form the formal working draft data.

2. The method for solving surface ink appearance defects according to claim 1, characterized in that: The defect handling method for abnormality type 1 and abnormality type 2 further includes: The ink leakage points of IC printing screen are made according to the IC Pad working draft with a single side +4mil of welding window. Among them, the edges of the ink leakage points between ICs overlap and connect together to form the overall ink leakage.

3. The method for solving surface ink appearance defects according to claim 1, characterized in that: The defect handling method for the third abnormality type further includes: The printing DSR screen design remains unchanged; The second adjustment of CAM exposure data requires pre-amplification of the optical positioning points and the graphic data inside the board in equal proportion. The data outside the board is guaranteed to be pre-amplified 100%, and the graphics inside the PCS are pre-amplified accordingly to ensure the consistency of the data outside the board and the pre-amplification inside the PCS.

4. The method for solving surface ink appearance defects according to claim 1, characterized in that: After selecting a corresponding method to handle the abnormal type of ink appearance defect, the following steps are also included: After obtaining a defect-free PCB according to the corresponding treatment, the PCB product is obtained through post-surface treatment and shape removal; The obtained PCB finished product is subjected to functional testing, which includes electrical performance and reliability testing.

5. The method for solving surface ink appearance defects according to claim 1, characterized in that: The PCB processing technology includes: According to the structure of the circuit board, the corresponding inner layer board is made, and the inner layer pattern is etched on each inner layer substrate through the inner layer dry film pressing and the image transfer of the inner layer exposure machine, and the use of acid etching; According to the structural order of the circuit board, use the bonding sheet, stack the substrate and the bonding sheet in order on the press platform, and use the hot press to press the circuit boards together; Use a drilling machine to drill via holes for circuit connection on the pressed circuit board; Perform chemical copper deposition and electroplating to deposit a specified copper thickness on the via hole wall; According to the circuit diagram, use full-board image or pattern electroplating image transfer to produce the outer layer pattern; After pre-treatment, the circuit board enters the clean room for printing. After printing, it is short-baked and then normally exposed according to the CAM data. It is placed in the ink developing line for ink window development. After the pattern is developed, UV curing is carried out.

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