Manufacturing method for preventing hole wall separation of double-sided circuit board square groove hole after tin spraying

Abstract

The invention discloses a manufacturing method for preventing hole wall separation after tin spraying of a double-sided circuit board square slotted hole, and the method comprises the following steps: S1, drilling a square slotted hole: drilling positioning guide holes at the R corners of the four corners of the square slotted hole; a plurality of round holes are drilled in the middle of the square slotted hole, and the round holes are tangent to slotted hole walls on the four sides of the square slotted hole; slotted holes are drilled in the four sides of the square slotted hole, two first slotted holes for controlling the width of the square slotted hole are drilled firstly, and then two second slotted holes in the length direction of the square slotted hole are drilled; the temperature is Tg + (5-10) DEG C, and the time is 3.5-4.5 h; removing glue residues; electroplating, wherein the copper thickness of the single side of the wall of the slotted hole after electroplating is 27-32 microns; the temperature ranges from 135 DEG C to 145 DEG C, and the time ranges from 1 h to 1.5 h; and tin spraying is conducted, and the thickness of single-side tin of the hole wall of the square groove hole is 5-10 microns. According to the manufacturing method for preventing the hole wall separation after the tin spraying of the square slotted hole of the double-sided circuit board, the hole wall separation after the tin spraying of the square slotted hole of the double-sided circuit board is avoided, so that the reliability of similar circuit boards is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board manufacturing, and particularly relates to a manufacturing method for preventing the separation of the hole wall after hot air leveling spraying of square slot holes on a double-sided printed circuit board. Background Art

[0002] With the rapid development of electronic devices towards miniaturization and high-density interconnection, double-sided printed circuit boards are widely used in fields such as communication, consumer electronics, and automotive electronics due to their compact structure and flexible wiring. In the design of double-sided printed circuit boards, square slot holes (rectangular or square slotted holes) are often used to connect high-power devices, heat dissipation modules, or mechanical fixing components to achieve dual functions of electricity and structure due to their special geometric shapes. However, in the surface treatment process, especially after hot air leveling spraying, the copper layer on the hole wall of the square slot hole is extremely prone to separation from the substrate, seriously affecting the reliability and yield of the product.

[0003] In view of this, it is necessary to provide a new process to solve the above technical problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a manufacturing method for preventing the separation of the hole wall after hot air leveling spraying of square slot holes on a double-sided printed circuit board, which can avoid the separation of the hole wall after hot air leveling spraying of square slot holes on a double-sided printed circuit board, thereby improving the reliability of similar printed circuit boards.

[0005] The technical solution of the present invention is as follows:

[0006] A manufacturing method for preventing the separation of the hole wall after hot air leveling spraying of square slot holes on a double-sided printed circuit board includes the following steps:

[0007] Step S1, drilling square slot holes, including the following steps:

[0008] Step S11, drilling positioning pilot holes at the four R corners of the square slot hole;

[0009] Step S12, drilling a plurality of round holes in the middle of the square slot hole, and the round holes are tangent to the hole walls of the slot holes on the four sides of the square slot hole;

[0010] Step S13, drilling slot holes on the four sides of the square slot hole, where two first slot holes for controlling the slot width of the square slot hole are drilled first, and then two second slot holes in the length direction of the square slot hole are drilled;

[0011] Step S2, baking the board at a temperature of Tg+(5 - 10)°C for 3.5 - 4.5 h;

[0012] Step S3, desmutting, controlling the temperature of the desmutting solution at 75±5°C, the Mn in the solution 7+ is controlled at 55 - 65 g / L, and the Mn 6 + is controlled at <30 g / L, and the amount of desmutting is controlled at 0.1 - 0.3 mg / cm2;

[0013] Step S4, electroplating. The sulfuric acid concentration in the electroplating solution is controlled at 60 - 90 g / L, the copper sulfate concentration is controlled at 100 - 120 mL / L, the chloride ion concentration is controlled at 50 - 80 ppm, and the single-sided copper thickness on the hole wall of the rear square groove is 27 - 32 μm.

[0014] Step S5, baking the board, the temperature is 135 - 145 °C, and the time is 1 - 1.5 h.

[0015] Step S6, spraying tin, so that the single-sided tin thickness on the hole wall of the square groove is 5 - 10 μm.

[0016] Furthermore, in step S1, when drilling the square groove holes, an EA0.7 mm grooving tool is used, and the two - piece stacked drilling process is adopted. The feed rate is 0.3 m / min, and the life is 1000 holes.

[0017] Furthermore, in step S11, the diameter of the positioning pilot hole is 0.4 mm.

[0018] Furthermore, in step S2, when the circuit board is a double - sided board, the board needs to be baked before and after drilling the square groove holes; when the circuit board is a multi - layer board, the board is baked after drilling the square groove holes.

[0019] Furthermore, in step S3, the degumming temperature is 85 ± 3 °C, and the degumming rate is 0.15 - 0.4 mg / cm 2 .

[0020] Furthermore, step S6 includes the following steps:

[0021] Tin immersion, the copper content in the tin solution is 0.5 - 0.9 wt%, the temperature of the tin solution is 260 - 270 °C, and the tin immersion time is 2.5 s.

[0022] Spraying tin in the rosin - passing section, the front and rear air knife temperatures are 340 - 380 °C, and the air pressure is 2.5 - 4.0 Kg / cm 2 ; The tin bath is de - coppered once every 300 square meters of production, and the copper content is controlled at 0.6 - 0.8%.

[0023] Compared with the prior art, the manufacturing method provided by the present invention for preventing the separation of the hole wall after spraying tin on the square groove holes of a double - sided circuit board has the beneficial effects that:

[0024] First, in the manufacturing method provided by the present invention for preventing the separation of the hole wall after spraying tin on the square groove holes of a double - sided circuit board, when drilling the square groove holes, first drill the positioning pilot holes at the four corners, then drill multiple round holes in the middle of the square groove holes to ensure that all the intermediate substrates are drilled through, and finally drill the groove holes on the four sides to control the groove width and groove length, which can prevent the deviation of the square groove hole drilling and improve the drilling accuracy of the square groove hole; after subsequent electroplating and spraying tin processes, the copper thickness and tin thickness on the hole wall are more uniform, avoiding the separation of the hole wall after spraying tin on the square groove holes of the double - sided circuit board, thereby improving the reliability of similar circuit boards.

[0025] 2. The manufacturing method provided by the present invention for preventing the separation of the hole wall after spraying tin on the square groove holes of a double-sided circuit board solves the problem of hole wall separation in multiple dimensions, from structural stability, interface cleanliness to plating uniformity, by controlling drilling accuracy, optimizing thermal management, and coordinately adjusting the process parameters of the metal layer, thereby improving the reliability of the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 is a schematic flow chart of drilling square groove holes in the manufacturing method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and make the above-mentioned objects, features, and advantages of the present invention more obvious and understandable, the following further describes the specific embodiments of the present invention.

[0029] It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] A manufacturing method for preventing the separation of the hole wall after spraying tin on the square groove holes of a double-sided circuit board includes the following steps:

[0031] Step S1: Drill square groove holes, as Figure 1 shown, including the following steps:

[0032] Step S11: Drill positioning pilot holes 1 at the R corners of the four corners of the square groove hole. Specifically, the diameter of the positioning pilot hole 1 is 0.4 mm to ensure accurate drilling positioning;

[0033] Step S12: Drill a plurality of round holes 2 in the middle of the square groove hole. The round holes are tangent to the hole walls of the groove holes on the four sides of the square groove hole to ensure that all the intermediate substrates are drilled through and reduce the residual stress;

[0034] Step S13: Drill slot holes on the four sides of the square slot hole. First, drill two first slot holes 31 that control the slot width of the square slot hole, and then drill two second slot holes 32 in the length direction of the square slot hole. When drilling the slot holes, use an EA0.7mm slot cutter and the two-piece overlapping drilling process. The feed rate is 0.3m / min and the tool life is 1000 holes. The step-by-step processing of the slot holes can avoid deviation and improve the accuracy of the hole wall structure, providing a uniform basis for subsequent copper plating / tin spraying.

[0035] Step S2: Bake the board at a temperature of Tg+(5 - 10)°C for 3.5 - 4.5h.

[0036] When the circuit board is a double-sided board, baking is required before and after drilling the square slot hole. When the circuit board is a multi-layer board, baking is only required after drilling the square slot hole. At this time, the functions of the baking process are: removing residual moisture and volatiles from drilling; releasing drilling stress and reducing substrate deformation; improving the resin state of the hole wall and enhancing the bonding strength.

[0037] Step S3: Desmear. Control the temperature of the desmear solution at 75±5°C, the Mn in the solution is controlled at 55 - 65g / L, the Mn is controlled at <30g / L, and the desmear amount is controlled at 0.1 - 0.3mg / cm2. 7+ Control the Mn in the solution at 55 - 65g / L, and the Mn is controlled at <30g / L. 6 + Specifically, the desmear temperature is 85±3°C, the desmear rate is 0.15 - 0.4mg / cm, thoroughly clean the gum residue on the hole wall to ensure the tight bonding of the electroplated copper layer and the substrate.

[0038] Step S4: Electroplate. Control the sulfuric acid concentration in the electroplating solution at 60 - 90g / L, the copper sulfate concentration at 100 - 120mL / L, and the chloride ion concentration at 50 - 80ppm. After electroplating, the single-sided copper thickness on the hole wall of the square slot hole is 27 - 32um. The single-sided copper thickness on the hole wall can provide sufficient mechanical support and reduce the peeling of the copper layer caused by thermal expansion differences. 2 The single-sided copper thickness on the hole wall can provide sufficient mechanical support and reduce the peeling of the copper layer caused by thermal expansion differences.

[0039] Step S5: Bake the board at a temperature of 135 - 145°C for 1 - 1.5h.

[0040] At this time, the functions of the baking process are: removing residual chemical substances from electroplating; releasing the internal stress of the coating to prevent cracking; preventing delamination in subsequent high-temperature processes.

[0041] At this time, the functions of the baking process are: removing residual chemical substances from electroplating; releasing the internal stress of the coating to prevent cracking; preventing delamination in subsequent high-temperature processes.

[0042] Step S6: Tin spray to make the single-sided tin thickness on the hole wall of the square slot hole 5 - 10um. Specifically, it includes the following steps:

[0043] Immerse in tin. The copper content in the tin solution is 0.5 - 0.9wt%, the temperature of the tin solution is 260 - 270°C, and the immersion time is 2.5s to prevent tin from accumulating at the four corners R of the square slot hole.

[0044] Spray tin through the rosin section, with the front and rear air knife temperatures at 340 - 380 °C and the air pressure at 2.5 - 4.0 Kg / cm 2 ; Remove copper from the tin bath every 300 square meters of production, and control the copper content at 0.6 - 0.8%.

[0045] This spray tin process can reduce the influence of thermal stress on the copper layer.

[0046] The manufacturing method of the present invention for preventing the separation of the hole wall after spray tin of the square groove holes of the double-sided circuit board solves the problem of hole wall separation in multiple dimensions from structural stability, interface cleanliness to plating uniformity through the control of drilling accuracy, optimization of thermal management, and coordinated adjustment of the process parameters of the metal layer, and improves the reliability of the circuit board.

[0047] The above has made a detailed description of the embodiments of the present invention, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principle and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A manufacturing method for preventing the separation of the hole wall after spraying tin on the square slot holes of a double-sided circuit board, characterized in that, It includes the following steps: Step S1, drilling a square groove hole, which includes the following steps: Step S11, drilling positioning pilot holes at the R corners of the four corners of the square groove hole; Step S12, drilling multiple round holes in the middle of the square groove hole, and the round holes are tangent to the groove hole walls on the four sides of the square groove hole; Step S13, drilling groove holes on the four sides of the square groove hole, where two first groove holes for controlling the groove width of the square groove hole are drilled first, and then two second groove holes in the length direction of the square groove hole are drilled; Step S2, baking the board, the temperature is Tg+(5-10)°C, and the time is 3.5-4.5h; Step S3, desmutting. The temperature of the desmutting solution is controlled at 75 ± 5 °C, and the Mn in the solution 7+ is controlled at 55 - 65 g / L, and the Mn 6+ is controlled at < 30 g / L. The amount of desmutting is controlled at 0.1 - 0.3 mg / cm2; Step S4, electroplating, the sulfuric acid concentration in the electroplating solution is controlled at 60-90g / L, the copper sulfate concentration is controlled at 100-120mL / L, the chloride ion is controlled at 50-80ppm, and the single-sided copper thickness of the groove hole wall after electroplating is 27-32um; Step S5, baking the board, the temperature is 135-145°C, and the time is 1-1.5h; Step S6, spraying tin to make the single-sided tin thickness of the groove hole wall 5-10um.

2. The manufacturing method for preventing the separation of the hole wall after spraying tin on the square groove holes of a double-sided circuit board according to claim 1, characterized in that, In Step S1, when drilling the groove hole, an EA0.7mm groove cutter is used, a two-piece stacked drilling process is adopted, the feed speed is 0.3m / min, and the life is 1000 holes.

3. The manufacturing method for preventing the separation of the hole wall after spraying tin on the square groove holes of a double-sided circuit board according to claim 1, characterized in that In Step S11, the aperture of the positioning pilot hole is 0.4mm.

4. The manufacturing method for preventing the separation of the hole wall after spraying tin on the square slot holes of a double-sided circuit board according to claim 1, wherein, In Step S2, when the circuit board is a double-sided board, the board needs to be baked before and after drilling the square groove hole; when the circuit board is a multi-layer board, the board is baked after drilling the square groove hole.

5. The manufacturing method for preventing the separation of the hole wall after spraying tin on the square slot holes of a double-sided circuit board according to claim 1, characterized in that, In step S3, the degumming temperature is 85 ± 3 °C, and the degumming rate is 0.15 - 0.4 mg / cm 2 .

6. The manufacturing method for preventing the separation of the hole wall after spraying tin on the square groove holes of a double-sided circuit board according to claim 1, wherein Step S6 includes the following steps: Dipping in tin, the copper content in the tin bath is 0.5-0.9wt%, the temperature of the tin bath is 260-270°C, and the dipping time in tin is 2.5s. Spray tin through the colophony section, with the front and rear air knife temperatures at 340 - 380 °C and the air pressure at 2.5 - 4.0 Kg / cm 2 ; Remove copper from the tin bath once every 300 square meters of production, and control the copper content at 0.6 - 0.8%.

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