High-efficiency PCB preparation process

Abstract

The application relates to the technical field of PCBs, in particular to a high-efficiency PCB preparation process, which comprises the following steps: PCB pre-treatment, high-precision surface ink printing, high-precision surface UV curing, PCB overturn positioning, non-precision surface ink printing, non-precision surface heat curing and appearance and performance detection, and in the step of non-precision surface heat curing, the thickness, the area and the ink characteristics of the PCB are quantified, the warping risk index R is calculated, and the preset threshold value is used to automatically select and optimize the zoning scheme of step baking, so that the high-efficiency PCB preparation process can guarantee the preparation quality and simultaneously consider the production capacity.

Description

Technical Field

[0001] This invention relates to the field of PCB technology, and in particular to an efficient PCB manufacturing process. Background Technology

[0002] In PCB manufacturing, the process of using UV-cured solder mask on high-precision surfaces and thermosetting solder mask on non-precision surfaces is widely used due to its balance between precision and cost. However, because the curing mechanisms of UV curing and thermosetting are different, the shrinkage rate of the thermosetting layer is much greater than that of the cured UV layer, resulting in significant warping of the PCB board after thermosetting. Excessive warping will affect the reliability of subsequent SMT assembly, soldering, and final assembly.

[0003] In existing technologies, segmented heating (step baking) processes are often used to reduce warpage, but the following problems still exist: the number of heating intervals in step baking is fixed, and the heating intervals cannot be dynamically adjusted according to the board thickness, area, and ink characteristics, resulting in low production efficiency of low-risk PCB boards and difficulty in balancing production capacity while ensuring quality. Summary of the Invention

[0004] To address the issue that existing technologies use a fixed number of heating zones in stepped baking, making it impossible to dynamically adjust the heating zones based on board thickness, area, and ink characteristics, resulting in low production efficiency for low-risk PCBs and difficulty in balancing quality and production capacity, this invention provides a highly efficient PCB manufacturing process.

[0005] The present invention provides a high-efficiency PCB manufacturing process using the following technical solution: A high-efficiency PCB manufacturing process includes PCB pretreatment, high-precision surface ink printing, high-precision surface UV curing, PCB flipping and positioning, non-precision surface ink printing, non-precision surface thermal curing, and appearance and performance testing. The non-precision surface thermal curing process includes the following steps: S61, Obtain input parameters: Obtain the PCB board thickness h, board area A, and ink coefficient a of the thermosetting ink; S62, Calculate the warpage risk index R: , Where a, A0, and h0 are preset constants; S63: Dynamic selection of partition scheme: preset the first threshold R1 and the second threshold R2, where 0 < R1 < R2. When R < R1, the number of baking intervals N = 2, the baking temperatures are 80°C and 150°C respectively, the baking duration T1 for each interval is 30 min, and the transition duration t1 between adjacent intervals is 5 min; when R1 ≤ R < R2, the number of baking intervals N = 3, the baking temperatures are 80°C, 115°C and 150°C respectively, the baking duration T2 for each interval is 20 min, and the transition duration t2 between adjacent intervals is 8 min; when R ≥ R2, the number of baking intervals N = 4, the baking temperatures are 60°C, 90°C, 120°C and 150°C respectively, the baking duration T3 for each interval is 15 min, and the transition duration t3 between adjacent intervals is 12 min; S64. Perform thermal curing: The oven executes the thermal curing program according to the number of baking intervals, baking temperature, total baking duration, and interval transition time.

[0006] Preferably, in S63, the following steps are further included: adjusting the interval transition duration t according to the R value: , where, when R < R1, take R0 = R1 / 2; when R1 ≤ R < R2, take R0 = (R1 + R2) / 2; when R ≥ R2, take R0 = R2 + (R2 - R1) / 2.

[0007] Preferably, measure the actual warpage value W after thermal curing actual , compare it with the target warpage value W target , and obtain the deviation e = W actual - W target , introduce the correction coefficient y, with an initial y = 1, and continuously update the correction coefficient y: , where K is the adjustment sensitivity coefficient, restricting y ∈ [y min , y max , when y is lower than y min , reduce t n , when y is higher than y max , increase t n .

[0008] Preferably, the ink coefficient a is calibrated by a standard test piece. The thickness of the standard test piece is t0 and the area is A0. After curing the ink to be measured, the warpage value W test is measured, then a = W test / W ref , where W ref is the reference warpage value.

[0009] Preferably, the first threshold R1 and the second threshold R2 are determined by an empirical value-taking method.

[0010] Preferably, restrict t∈[t min ,t max When t is lower than t min When t takes t min When t is higher than t max When t takes t max .

[0011] Preferably, the sensitivity adjustment coefficient K is within the following range: 0.1≤K≤0.5.

[0012] Preferably, the oven is a PID-controlled oven.

[0013] Preferably, the oven is connected to a PCB thermosetting warpage control system, which includes: a parameter input module; a risk index calculation module; a zone selection module that stores the temperature sequence and standard transition time for each zone; a transition time scaling module; a warpage detection module; and a closed-loop correction module.

[0014] Preferably, the oven is filled with nitrogen gas for heat oxidation protection during thermosetting.

[0015] The beneficial effects of this invention are as follows: During the thermosetting process, the warpage risk index R is calculated by quantifying the PCB board thickness, board area, and ink characteristics. Based on a preset threshold, a stepped baking zone scheme is automatically selected, including the number of temperature zones, the duration of each zone, and the transition time. At the same time, a closed-loop feedback mechanism is used to dynamically adjust the transition time according to the actual warpage deviation. This allows for the use of more temperature zones and longer baking and transition times for high-warpage-risk boards to suppress deformation and ensure quality, while fewer temperature zones and shorter times are used for low-risk boards to improve efficiency, thus achieving an intelligent balance between quality and production capacity during the thermosetting process. Attached Figure Description

[0016] Figure 1 This is a flowchart of the PCB board manufacturing process in an embodiment of the present invention; Figure 2 This is a flowchart of the non-precision surface ink printing steps in an embodiment of the present invention; Figure 3 This is a formula diagram of the warpage risk index in an embodiment of the present invention; Figure 4 This is a formula diagram of the interval transition time in an embodiment of the present invention; Figure 5 This is a formula diagram of the correction coefficient in an embodiment of the present invention. Detailed Implementation

[0017] The following will combine Figures 1-5 The present invention will be further illustrated by the embodiments.

[0018] This embodiment discloses an efficient PCB manufacturing process.

[0019] The efficient PCB manufacturing process includes the following steps: S1, PCB board pretreatment: The PCB board is subjected to micro-etching, acid washing, water washing and hot air drying on both sides to remove oil stains, oxide layer and impurities from the board surface, so as to provide a stable base for subsequent ink printing.

[0020] S2, high-precision surface ink printing, uses screen printing or spraying to print UV-curable inks on the high-precision surface of the PCB board to obtain a precision ink pattern with uniform thickness.

[0021] S3, High-precision surface UV curing: Using UV curing equipment, the high-precision surface of the PCB board is cured by ultraviolet light, and the ink on the precision surface is rapidly shaped and cross-linked.

[0022] S4, PCB board flipping and positioning: The PCB board is flipped and fixed smoothly by a flipping device to ensure that non-precision surfaces can be printed normally.

[0023] S5, Non-precision surface ink printing: Thermosetting ink is printed on the non-precision surface of the PCB board by screen printing or spraying to obtain a non-precision ink layer with uniform thickness.

[0024] S6, Non-precision surface thermosetting: The PCB board is placed in an oven and baked and cured at a set temperature and time, so that the thermosetting ink is fully cross-linked, improving adhesion, solderability and reliability.

[0025] S7, Appearance and Performance Inspection: Perform visual inspection, adhesion test, solderability test and accuracy measurement on the double-sided ink to confirm that the double-sided curing quality, accuracy and reliability meet the standards.

[0026] Based on the above preparation process, in the S6 non-precision surface thermosetting process, in order to reduce warping caused by the difference in curing steps on both sides of the PCB board, a segmented heating method, i.e., stepped baking, is usually used to thermoset the non-precision surface of the PCB board. In this invention, in order to dynamically adjust the temperature and time parameters of the stepped baking according to the board thickness, area, and ink characteristics, thereby ensuring both quality and production capacity and achieving efficient preparation, the S6 non-precision surface thermosetting process also includes the following steps.

[0027] S61, Obtain input parameters: Obtain the board thickness h of the PCB, the board area A, and the ink coefficient a of the thermosetting ink, so as to adjust the thermosetting process according to the board thickness h, the board area A, and the ink coefficient a of the thermosetting ink in the subsequent steps. Here, the board thickness h refers to the thickness dimension between the precision surface and the non-precision surface of the PCB, the board area A refers to the area of the non-precision surface of the PCB, and the ink coefficient a is determined by the curing performance of the thermosetting ink.

[0028] S62, Calculate the warping risk index R: , where a, A0, and h0 are preset constants, such that the warping risk index increases with the increase of the board area and decreases with the increase of the board thickness.

[0029] S63, Dynamically select the zoning scheme: Preset the first threshold R1 and the second threshold R2, and 0 < R1 < R2. When R < R1, the number of baking intervals N = 2, the baking temperatures are 80°C and 150°C respectively, the baking duration T1 of each interval = 30 min, and the transition duration t1 between adjacent intervals = 5 min; when R1 ≤ R < R2, the number of baking intervals N = 3, the baking temperatures are 80°C, 115°C, and 150°C respectively, the baking duration T2 of each interval = 20 min, and the transition duration t2 between adjacent intervals = 8 min; when R ≥ R2, the number of baking intervals N = 4, the baking temperatures are 60°C, 90°C, 120°C, and 150°C respectively, the baking duration T3 of each interval = 15 min, and the transition duration t3 between adjacent intervals = 12 min. Through the above intelligent zoning, the low-risk PCB boards are subjected to step baking with fewer temperature intervals, shorter baking durations, and shorter transition durations to improve efficiency, and the high-risk PCB boards are subjected to step baking with more temperature intervals, longer baking durations, and longer transition durations to improve quality.

[0030] S64, Perform thermosetting: The oven executes the thermosetting program according to the number of baking intervals, the baking temperature, the total baking duration, and the interval transition time, and finally effectively improves the thermosetting efficiency of the non-precision surface of the PCB while ensuring quality, thereby effectively improving the manufacturing efficiency of the PCB.

[0031] The ink coefficient a in the above warping risk index formula is calibrated by a standard test piece. The thickness of the standard test piece is t0 and the area is A0. The warping value W is measured after curing with the ink to be tested. test , then a = W test / W ref , where W ref is the reference warping value. In some embodiments, the value of a can also be determined by an empirical value.

[0032] The first threshold value R1 and the second threshold value R2 can be determined by means of empirical value taking based on the statistics of a large amount of production data. In other embodiments, a standard test piece can also be used to measure the warpage value under different curing processes, and the first threshold value R1 and the second threshold value R2 can be determined by the change of the warpage value in the experiment.

[0033] In S63, the following steps are further included: adjusting the interval transition duration t according to the R value: , where, when R < R1, take R0 = R1 / 2; when R1 ≤ R < R2, take R0 = (R1 + R2) / 2; when R ≥ R2, take R0 = R2 + (R2 - R1) / 2. Through refined adjustment, even if different PCB boards fall into the same partition scheme, the difference in the interval transition time can be formed according to the specific numerical value of the risk value, so that the interval transition time of the PCB board with a smaller risk value is shortened to improve efficiency, and the interval transition time of the PCB board with a larger risk value is extended to improve quality. In addition, it is restricted that t ∈ [t min , t max . When t is lower than t min , t takes t min . When t is higher than t max , t takes t max to avoid the interval transition time becoming too short or too long after secondary adjustment.

[0034] After thermal curing, the actual warpage value measurement step of the PCB board is carried out by using a height gauge, a feeler gauge or a non-contact laser three-dimensional scanner to obtain the actual warpage value W actual , compare with the target warpage value W target , and obtain the deviation e = W actual - W target . Introduce a correction coefficient y, initially y = 1, and continuously update the correction coefficient y: , where K is the adjustment sensitivity coefficient, and it is restricted that y ∈ [y min , y max . When y is lower than y min , it means that the actual warpage value is much lower than the target warpage value. At this time, the production capacity can be increased by reducing t n , that is, by reducing the interval transition time, such as reducing the interval transition time by 5% - 20%, to improve the preparation efficiency while ensuring the quality. When y is higher than y max , it means that the actual warpage value is much higher than the target warpage value. At this time, the production capacity can be increased by increasing t nThis involves improving quality by extending the transition time within the interval, such as by 5%-20%, allowing the actual warpage value to gradually return to the acceptable range. Ultimately, through this closed-loop correction, the PCB fabrication effect can be adjusted in real time, more accurately balancing the fabrication quality and efficiency. Furthermore, in this embodiment, the sensitivity coefficient K is adjusted to a value within the following range: 0.1 ≤ K ≤ 0.5, to avoid excessively high correction sensitivity and thus reduce unnecessary corrections.

[0035] In this invention, the oven employs PID control to dynamically adjust the baking temperature and time. The oven is integrated with a PCB thermosetting warpage control system, which includes: a parameter input module; a risk index calculation module; a zone selection module storing the temperature sequence and standard transition time for each zone; a transition time scaling module; a warpage detection module; and a closed-loop correction module to complete the aforementioned intelligent stepped baking process. Furthermore, nitrogen gas is introduced into the oven during thermosetting to protect the PCB board from thermal oxidation during continuous high-temperature baking.

[0036] In this embodiment, two PCB boards with different parameters are used as examples. Based on standard test pieces and empirical values, A0 = 100 cm², h0 = 1.2 mm, a = 0.9, R1 = 0.5, and R2 = 1.2. If the PCB board thickness h = 1 mm and the board area A = 150 cm², then... 2 ,So: , Since R>1.2, the N=4 partition scheme is selected, that is, the baking temperatures are 60℃, 90℃, 120℃ and 150℃ respectively, the baking time of each partition is T3=15min, and the transition time between adjacent partitions is t3=12min.

[0037] Further: , Therefore, the actual interval transition time is adjusted as follows: , That is, the time was adjusted to 12 minutes and 32 seconds. Finally, for this PCB board with a high risk of warping, a stepped baking process was carried out with more temperature ranges, longer baking time and longer transition time to improve quality.

[0038] If the PCB board thickness h = 2.4 mm and the board area A = 50 cm², 2 ,So: , Since R < 0.5, a zoned baking scheme with N = 2 is selected, meaning the baking temperatures are 80℃ and 150℃, the baking time for each zone is T1 = 30 min, and the transition time between adjacent zones is t1 = 5 min. Furthermore, Therefore, the actual interval transition time is adjusted as follows: , That is, it was adjusted to 4 minutes and 30 seconds. Finally, for this PCB board with a low risk of warping, a stepped baking process was carried out with fewer temperature ranges, shorter baking time and shorter transition time, so as to improve efficiency while ensuring quality.

[0039] In summary, the implementation principle of the efficient PCB manufacturing process in this embodiment is as follows: During the thermosetting process, the warpage risk index R is calculated by quantifying the PCB thickness, area, and ink characteristics. Based on a preset threshold, a stepped baking partition scheme is automatically selected, including the number of temperature zones, the duration of each zone, and the transition time. At the same time, a closed-loop feedback mechanism is used to dynamically correct the transition time based on the actual warpage deviation. This allows for the use of more temperature zones and longer baking and transition times for high-warpage-risk PCBs to suppress deformation and ensure quality, while fewer temperature zones and shorter times are used for low-risk PCBs to improve efficiency, thus achieving an intelligent balance between quality and production capacity during the thermosetting process.

[0040] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-efficiency PCB manufacturing process, comprising PCB pretreatment, high-precision surface ink printing, high-precision surface UV curing, PCB flipping and positioning, non-precision surface ink printing, non-precision surface thermal curing, and appearance and performance inspection, characterized in that, Among them, The non-precision surface thermal curing includes the following steps: S61, obtaining input parameters: obtaining the board thickness h, board area A of the PCB board, and the ink coefficient a of the thermal curing ink; S62, calculating the warping risk index R: ， Among them, a, A0, and h0 are preset constants; S63: Dynamically select the zoning scheme: preset the first threshold R1 and the second threshold R2, and 0 < R1 < R2. When R < R1, the number of baking intervals N = 2, the baking temperatures are 80°C and 150°C respectively, the baking duration T1 = 30 min for each interval, and the transition duration t1 between adjacent intervals = 5 min; when R1 ≤ R < R2, the number of baking intervals N = 3, the baking temperatures are 80°C, 115°C, and 150°C respectively, the baking duration T2 = 20 min for each interval, and the transition duration t2 between adjacent intervals = 8 min; when R ≥ R2, the number of baking intervals N = 4, the baking temperatures are 60°C, 90°C, 120°C, and 150°C respectively, the baking duration T3 = 15 min for each interval, and the transition duration t3 between adjacent intervals = 12 min; S64, performing thermal curing: The oven executes the thermal curing program according to the number of baking intervals, baking temperature, total baking duration, and interval transition time.

2. The high-efficiency PCB manufacturing process according to claim 1, characterized in that: In S63, the following steps are further included: adjusting the interval transition duration t according to the R value: ， Among them, when R < R1, take R0 = R1 / 2; when R1 ≤ R < R2, take R0 = (R1 + R2) / 2; when R ≥ R2, take R0 = R2 + (R2 - R1) / 2.

3. The high-efficiency PCB manufacturing process according to claim 2, characterized in that: The actual warpage value W was measured after thermosetting. actual Compare the target warp value W target The deviation e=W is obtained. actual -W target Introduce a correction coefficient y, initially y=1, and continuously update the correction coefficient y: ， Where K is the sensitivity adjustment coefficient, restricting y∈[y] min ,y max When y is lower than y min When t decreases n When y is higher than y max When t increases n .

4. The high-efficiency PCB manufacturing process according to claim 1, characterized in that: The ink coefficient α is calibrated using a standard test piece with a thickness of t0 and an area of ​​A0. The warpage value W is measured after the ink to be tested has been cured. test Then a=W test / W ref Among them, W ref For reference warpage value.

5. The high-efficiency PCB manufacturing process according to claim 1, characterized in that: The first threshold R1 and the second threshold R2 are determined by empirical values.

6. The high-efficiency PCB manufacturing process according to claim 2, characterized in that: Restriction t∈[t min ,t max When t is lower than t min When t takes t min When t is higher than t max When t takes t max .

7. The high-efficiency PCB manufacturing process according to claim 3, characterized in that: The adjustment sensitivity coefficient K takes values within the following range: 0.1 ≤ K ≤ 0.

5.

8. The high-efficiency PCB manufacturing process according to claim 1, characterized in that: The oven uses PID to control the oven.

9. The high-efficiency PCB manufacturing process according to claim 8, characterized in that: The oven is connected to the PCB thermal curing warping control system, and the system includes: a parameter input module; a risk index calculation module; a zoning selection module that stores the temperature sequence and standard transition time corresponding to each zone; a transition time scaling module; a warping detection module; and a closed-loop correction module.

10. The high-efficiency PCB manufacturing process according to claim 1, characterized in that: When the oven performs thermal curing, nitrogen is filled for thermal oxidation protection.

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