Manufacturing method capable of improving metallization quality of step platform or counter bore

Abstract

The invention discloses a manufacturing method capable of improving metallization quality of a stepped platform or a counter bore. The manufacturing method comprises the following steps: drilling holes in a production board; a counter bore or a concave platform is formed in the position, corresponding to the milling groove, of the production board in a depth-controlled milling groove mode; carrying out plasma surface treatment on the production board so as to coarsen the surface of the counter bore or the platform and remove glass fiber burrs generated on the surface of the counter bore or the platform after board milling; and sequentially carrying out copper deposition and full-board electroplating treatment on the production board so as to metallize the counter bore or the platform. According to the method, the plasma surface treatment procedure is added after the counter bore or the platform is milled, so that the surface of the platform is coarsened, glass fiber burrs generated after plate milling on the surface of the counter bore or the platform are removed, and the quality problems of copper sheet damage, copper particles, blistering and the like after metallization caused by burrs and insufficient coarsening degree on the surface of the platform are solved.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board manufacturing, and in particular to a manufacturing method capable of improving the metallization quality of a step platform or a countersunk hole. Background Art

[0002] In the process of printed circuit board manufacturing, the PTH platform manufacturing method usually requires first drilling NPTH countersunk holes or platforms on the substrate, and then performing PTH (metallization) electroplating on the drilled substrate for use in conducting circuits.

[0003] At present, when making PTH (metallization) countersunk holes or platforms on circuit boards, countersunk holes or platform processing is first performed after drilling, and then PTH (metallization) copper plating (0.5um plating) and full-board electroplating (15-25um plating) are performed. The processing flow is as follows: front process → outer layer drilling → milling PTH groove → countersunk platform → outer layer copper plating → full-board electroplating → outer layer pattern → pattern electroplating → outer layer etching → back process.

[0004] This approach has the following drawbacks:

[0005] 1. During the gong process, since the gong knife directly acts on the glass fiber PP of the substrate, the glass fiber PP on the plate will be pulled during the cutting process of the gong knife. The glass fiber PP will have tiny fractures under the action of the rotating torque of the gong knife and the horizontal surface cutting force, resulting in unevenness, pits and burrs on the platform surface, and damage or copper particles after copper plating.

[0006] 2. At the same time, the platform is relatively smooth locally and the roughness is insufficient. After copper deposition, the bonding force between the platform surface and the copper deposition layer is insufficient, and the broken glass fiber will hide water vapor. During the electroplating process, the copper layer will bubble when heated.

[0007] At present, in order to avoid burrs when glass fiber PP breaks, the following improvement methods are usually adopted:

[0008] 1. The first method is to slow down the feed speed and rotation speed of the gong cutter, which greatly reduces the efficiency of the gong plate. In addition, since the gong plate cuts the glass fiber PP layer by layer horizontally when the gong cutter end face is cut, and each layer of glass fiber PP is composed of multiple tiny glass fibers, even if the feed speed and rotation speed and other parameters are adjusted during the cutting process, the problems of unevenness and burrs caused by the breakage of glass fiber PP on the surface of the rear platform of the gong platform cannot be fundamentally solved.

[0009] 2. The second method is to use a double-edged gong cutter and adopt a segmented gong method to improve the tool's cutting ability on PP and adjust the depth of the gong plate each time (dividing the overall depth into 3 gongs) to reduce the amount of cutting each time. However, due to the limitations of the processing principle, it is still impossible to ensure that the gong cutter can completely and effectively cut the glass fiber PP on the platform surface when passing through the glass fiber of the plate, and the processing efficiency is low.

[0010] 3. The third method is to add a grinding process to remove burrs, that is, to use the grinding process on the platform position of the gong. However, since the platform position is lower than the surface of the plate, there will be problems such as the platform not being able to be ground partially or the plate surface being worn too much during grinding, and the problem of uneven platform cannot be fundamentally solved. Summary of the invention

[0011] In view of the above-mentioned existing technical defects, the present invention provides a manufacturing method for improving the metallization quality of stepped platforms or countersunk holes. A plasma surface treatment process is added after the countersunk hole or platform is gonged to roughen the platform surface and remove the glass fiber burrs on the countersunk hole or platform surface caused by the gong plate, thereby solving the quality problems of copper skin damage, copper particles and blistering caused by burrs and insufficient roughening of the platform surface after metallization.

[0012] In order to solve the above technical problems, the present invention provides a manufacturing method for improving the metallization quality of a step platform or a countersunk hole, comprising the following steps:

[0013] S1, drilling holes on the production board;

[0014] S2. A countersunk hole or a concave platform is gonged out at the position corresponding to the gong groove on the production plate by controlling the depth of the gong groove;

[0015] S3. Plasma surface treatment is performed on the production plate to roughen the surface of the countersunk hole or platform and remove the glass fiber burrs on the surface of the countersunk hole or platform caused by gong plate;

[0016] S4. The production board is subjected to copper deposition and full-board electroplating treatment in sequence to metallize the countersunk holes or platforms.

[0017] Furthermore, in step S2, the tool speed when countersinking or drilling the platform is 14 mm / s.

[0018] Furthermore, in step S2, the tool speed during countersinking or platforming is 28Krpm / min.

[0019] Furthermore, the following steps are included between step S3 and step S4:

[0020] S31. Bake the production board to remove the gas remaining in the countersunk hole or the platform.

[0021] Furthermore, in step S31, the baking temperature is 105° C. and the baking time is 1 hour.

[0022] Furthermore, after step S4, the following steps are also included:

[0023] S5. Perform outer layer circuit production, solder mask production, surface treatment and molding processes on the production board in sequence to obtain a buried copper circuit board.

[0024] Furthermore, the production board is a multi-layer board in which an inner core board and an outer copper foil are pressed together by a prepreg, and the inner core board has undergone an inner circuit production process before pressing.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] In the present invention, after the countersink or platform is gonged, a plasma surface treatment process is added, in which charged particles impact the surface of the countersink or platform under the action of an electric field, so as to roughen the surface of the countersink or platform and remove the glass fiber burrs on the surface of the countersink or platform caused by gonging, so as to make the surface of the countersink or platform smooth and increase the overall roughness, thereby increasing the bonding force between the countersink or platform and the chemical copper deposition layer, avoiding the problem of stratification and blistering of the copper deposition layer, and also avoiding the problem of copper particles after copper plating due to burrs. It can meet the normal production of PTH (metallization) countersinks or platforms without affecting the normal gonging efficiency.

[0027] Secondly, a baking process is added after the plasma surface treatment, which can effectively remove the gas remaining on the countersunk hole or platform surface during the previous plasma surface treatment process, and further avoid the problem of stratification and bubbles in the copper layer after being heated during electroplating due to the presence of gas.

[0028] In addition, by reducing the tool speed and tool rotation speed when countersinking or laying a platform, specifically: adjusting the tool speed from the current 18mm / s to 14mm / s, and the tool rotation speed from 35Krpm / min to 28Krpm / min, the amount of burrs generated by the tool pulling the glass fiber PP when countersinking or laying a platform can be effectively reduced. DETAILED DESCRIPTION

[0029] In order to more fully understand the technical content of the present invention, the technical solution of the present invention will be further introduced and illustrated in conjunction with specific embodiments below.

[0030] Example

[0031] A method for manufacturing a circuit board shown in this embodiment includes the following processing steps in sequence:

[0032] (1) Cutting: Cut the core board according to the panel size of 520mm×620mm. The thickness of the core board is 0.5mm, and the thickness of the copper layer on both surfaces of the core board is 0.5oz.

[0033] (2) Inner layer circuit production (negative film process): Inner layer pattern transfer, use a vertical coating machine to coat the photosensitive film, the film thickness of the photosensitive film is controlled to 8μm, and a fully automatic exposure machine is used to complete the exposure of the inner layer circuit with a 5-6 grid exposure ruler (21 grid exposure ruler). After development, the inner layer circuit pattern is formed; inner layer etching, the exposed and developed core board is etched to etch the inner layer circuit, and the inner layer line width is measured to be 3mil; inner layer AOI, and then check the inner layer circuit for defects such as open short circuits, circuit gaps, and circuit pinholes. Defective products are scrapped, and non-defective products are sent to the next process.

[0034] (3) Lamination: The browning speed is based on the browning thickness of the bottom copper. The core board, prepreg, and outer copper foil are laminated in sequence as required. Then, appropriate lamination conditions are selected according to the Tg of the sheet material to laminate the laminated board to form a production board.

[0035] (4) Drilling: Based on the existing drilling technology, drilling processing is performed on the production board according to the design requirements.

[0036] (5) Gong groove: A countersunk hole or a concave platform is gonged out at the position corresponding to the gong groove (i.e., stepped platform or countersunk hole) on the production plate by controlling the depth of the gong groove.

[0037] In the above, the tool speed when countersinking or grooving is 14mm / s, which is 4mm / s lower than the tool speed of 18mm / s in the prior art; the tool speed when countersinking or grooving is 28Krpm / min, which is 7Krpm / min lower than the tool speed of 35Krpm / min in the prior art; by reducing the tool speed and speed, the amount of burrs generated by the tool pulling the glass fiber PP when countersinking or grooving can be effectively reduced.

[0038] (6) Plasma treatment: Plasma surface treatment is performed on the production board. Charged particles are used to impact the surface of the countersunk hole or platform under the action of the electric field to roughen the surface of the countersunk hole or platform and remove the glass fiber burrs on the surface of the countersunk hole or platform caused by gong plate, thereby increasing the roughness of the surface of the countersunk hole or platform, thereby increasing the bonding strength between the countersunk hole or platform and the subsequent chemical copper deposition layer, avoiding the problem of stratification and blistering of the copper deposition layer.

[0039] (7) Baking: The production board is baked to remove the gas remaining in the countersunk hole or platform in the previous process.

[0040] In the above, the baking temperature is 105°C and the baking time is 1 hour.

[0041] (8) Copper plating: A thin layer of copper is deposited on the board surface and the hole wall by chemical copper plating, and a thin layer of copper is deposited on the surface of the countersunk hole or platform. The backlight test is level 10, and the thickness of the copper in the hole is 0.5μm.

[0042] (9) Full-board electroplating: The production board is subjected to full-board electroplating treatment to thicken the copper layer of the holes and the copper layer on the board surface, and also thicken the thickness of the surface copper layer of the countersunk hole or platform.

[0043] (10) Production of outer circuits (negative film process): Use a vertical coating machine to coat the photosensitive film, the film thickness of the photosensitive film is controlled to 8μm, and a fully automatic exposure machine is used to complete the exposure of the outer circuit with a 5-6 grid exposure ruler (21 grid exposure ruler). After development, the outer circuit pattern is formed; outer layer etching, the production board after exposure and development is etched to etch out the outer circuit, and the outer layer line width is measured to be 3mil; outer layer AOI, using an automatic optical inspection system, by comparing with the CAM data, detect whether the outer circuit has defects such as open circuit, gap, incomplete etching, short circuit, etc.

[0044] (11) Solder mask and silk screen characters: After the solder mask ink is silk screen printed on the surface of the production board, it is sequentially subjected to pre-curing, exposure, development and thermal curing treatments to solidify the solder mask ink into a solder mask layer; specifically, a "UL mark" is added to the solder mask ink on the TOP surface and the characters on the TOP surface, thereby coating a layer on the circuits and substrates that do not require soldering to prevent bridging between circuits during soldering, provide a permanent electrical environment and resist chemical corrosion, and at the same time beautify the appearance.

[0045] (12) Surface treatment (nickel-gold immersion): The copper surface of the pad at the solder mask opening is treated with chemical principles to uniformly deposit nickel and gold layers of a certain required thickness. The thickness of the nickel layer is 3-5 μm; the thickness of the gold layer is 0.05-0.1 μm. After immersion, the chemical-resistant gold ink is removed.

[0046] (13) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0047] (14) Molding: According to the existing technology and the design requirements, the circuit board is manufactured with a shape tolerance of + / -0.05mm.

[0048] (15) FQC: Inspect the appearance of the circuit board according to the customer's acceptance standards and our inspection standards. If there are any defects, repair them in time to ensure that we provide customers with excellent quality control.

[0049] (16) FQA: Re-test the circuit board’s appearance, hole copper thickness, dielectric layer thickness, green oil thickness, inner layer copper thickness, etc. to see if they meet customer requirements.

[0050] (17) Packaging: According to the packaging method and packaging quantity required by the customer, the circuit boards are sealed and packed with desiccant and humidity card before shipment.

[0051] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for improving the metallization quality of a step platform or a countersunk hole, characterized in that: The following steps are involved: S1, drilling holes on the production board; S2. A countersunk hole or a concave platform is gonged out at the position corresponding to the gong groove on the production plate by controlling the depth of the gong groove; S3. Plasma surface treatment is performed on the production plate to roughen the surface of the countersunk hole or platform and remove the glass fiber burrs on the surface of the countersunk hole or platform caused by gong plate; S4. The production board is subjected to copper deposition and full-board electroplating treatment in sequence to metallize the countersunk holes or platforms.

2. The manufacturing method for improving the metallization quality of the step platform or countersunk hole according to claim 1, characterized in that: In step S2, the tool speed when countersinking or drilling the platform is 14 mm / s.

3. The manufacturing method for improving the metallization quality of the step platform or countersunk hole according to claim 1, characterized in that: In step S2, the tool speed during countersinking or platforming is 28Krpm / min.

4. The manufacturing method for improving the metallization quality of the step platform or countersunk hole according to claim 1, characterized in that: The following steps are also included between steps S3 and S4: S31. Bake the production board to remove the gas remaining in the countersunk hole or the platform.

5. The manufacturing method for improving the metallization quality of the step platform or countersunk hole according to claim 4, characterized in that: In step S31, the baking temperature is 105°C and the baking time is 1 hour.

6. The manufacturing method for improving the metallization quality of the step platform or countersunk hole according to claim 1, characterized in that: The step S4 further includes the following steps: S5. Perform outer layer circuit production, solder mask production, surface treatment and molding processes on the production board in sequence to obtain a buried copper circuit board.

7. The manufacturing method for improving the metallization quality of the step platform or countersunk hole according to claim 1, characterized in that: The production board is a multi-layer board in which an inner core board and an outer copper foil are pressed together by a semi-cured sheet, and the inner core board has undergone an inner layer circuit production process before pressing.