Manufacturing method of stepped circuit board

Abstract

The invention discloses a manufacturing method of a stepped circuit board, which comprises the following steps of: pretreating a substrate, and forming a positioning mark of a stepped copper thickness area on an inner layer through an LDI (Laser Direct Imaging) laser direct imaging technology; coating an anti-corrosion dry film on the substrate, exposing an area needing deep etching through an LDI exposure device, and then developing the area; etching for the first time: partially etching the region needing deep etching, so that the thickness of residual copper in the deep etching region is equivalent to the thickness of copper needing to be etched in the shallow etching region; exposing a region needing shallow etching through an LDI light explosion device, and then developing the region; etching for the second time, namely etching the copper thickness remaining in the deep etching area and the shallow etching area; removing the film; performing press fit; and flattening the copper surface. According to the manufacturing method of the stepped circuit board, a differentiated etching process is adopted, a multi-layer stepped copper structure is pressed at a time, the manufacturing process is simple, and the copper thickness tolerance is small.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board manufacturing, and in particular to a method for manufacturing a stepped circuit board. Background Art

[0002] As electronic devices evolve toward intelligence, high precision, and high standards, they require increasingly sophisticated PCBs to support these electronic control systems. Navigation and radar circuit boards, in particular, demand greater power and current carrying capacity. As current increases, while circuit board module size and thickness remain fixed, copper thickness inevitably increases accordingly. Because navigation and radar circuit boards have varying copper thickness requirements for their circuitry and RF transmit and receive pads, these boards are essential for achieving their functionality, particularly in phased array radars. Therefore, stepped copper thicknesses are designed to meet varying functional requirements across different areas of the same surface. Consequently, demand for circuit boards with stepped copper thicknesses and step grooves is increasing.

[0003] Existing stepped copper production is generally achieved through multiple pressing or local electroplating, which is complex and has high production costs; and the existing chemical etching method easily leads to poor copper thickness uniformity, thus affecting signal integrity.

[0004] In view of this, the object of the present invention is to provide a new step circuit board manufacturing process to solve the above technical problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for manufacturing a stepped circuit board, which adopts a composite process of a differentiated etching process and a PP window opening process to achieve a single-time pressing of a multi-layer stepped copper structure, with a simple manufacturing process and a small copper thickness tolerance.

[0006] A method for manufacturing a stepped circuit board comprises the following steps:

[0007] Step S1: pre-processing the substrate, forming positioning marks of stepped copper thickness areas on the inner layer by LDI laser direct imaging technology;

[0008] Step S2, coating a dry resist film on the substrate, exposing the area to be deeply etched by an LDI exposure device, and then developing the area;

[0009] Step S3, the first etching, partially etches the area that needs deep etching, so that the remaining copper thickness in the deep etching area is equivalent to the copper thickness that needs to be etched in the shallow etching area; wherein the upper spray pressure of the deep etching area is controlled to be 2.5-3.0 bar, and the lower spray pressure is 2.5-3.5 kgf / cm 2 , the transmission speed of the circuit board is 1-3m / min;

[0010] Step S4, exposing the area requiring shallow etching by an LDI photoexposure device, and then developing the area;

[0011] Step S5, etching for the second time, etching the remaining copper thickness in the deep etching area and the shallow etching area, controlling the upper spray pressure to 1.0-1.5 bar, the lower spray pressure to 1.0-2.0 kgf / cm2, and the transmission speed of the circuit board to 3-7 m / min;

[0012] Step S6, film removal;

[0013] Step S7: Lamination: Lamination of the inner and outer circuit boards. The lamination adopts a staged temperature-raising lamination process. The lamination parameters of the first stage are: 120°C, 15 MPa, 30 minutes. The lamination parameters of the second stage are: 180°C, 25 MPa, to achieve curing and molding.

[0014] Step S8, copper surface planarization treatment, using chemical mechanical polishing process, polishing liquid pH value is 8.5-9.0, surface roughness Ra ≤ 0.3 μm;

[0015] The etching solution used in step S3 and step S5 includes copper chloride and hydrogen peroxide, wherein the concentration of copper chloride is 120-140 g / L, the temperature of the etching solution is 45-50° C., and the redox potential is 550-600 mV.

[0016] Furthermore, in step S1, the substrate is made of FR4 substrate.

[0017] Furthermore, the substrate is a high-frequency substrate with a Tg of 180°C.

[0018] Furthermore, in step S3 and step S5, the nozzle of the spray etching can be adjusted to an angle of 30-90°.

[0019] Furthermore, in step S5, during the second etching, a wedge-shaped guide plate is provided on the side wall of the etching groove to make the sprayed etching liquid form a turbulent flow.

[0020] Compared with the prior art, the method for manufacturing a stepped circuit board provided by the present invention has the following beneficial effects:

[0021] 1. The manufacturing method of the stepped circuit board of the present invention adopts a differentiated etching process, which can realize a single pressing of a multi-layer stepped copper structure. The manufacturing process is simple. By controlling the spray pressure and transmission speed in different etching stages, the copper thickness tolerance can be controlled within ±2um, and the copper thickness tolerance is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 It is a schematic diagram of the process of two etchings in the method for manufacturing a stepped circuit board of the present invention;

[0024] Figure 2 It is a schematic diagram of an etching device for the first etching in the method for manufacturing a stepped circuit board of the present invention;

[0025] Figure 3 It is a schematic diagram of an etching device for the second etching in the method for manufacturing a stepped circuit board of the present invention; DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the specific implementation methods of the present invention are further described below.

[0027] It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of 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.

[0028] See also Figure 1 , is a schematic diagram of the two etching processes in the method for manufacturing a stepped circuit board of the present invention. A method for manufacturing a stepped circuit board comprises the following steps:

[0029] Step S1: pre-processing the substrate, forming positioning marks of stepped copper thickness areas on the inner layer by LDI laser direct imaging technology;

[0030] This embodiment takes a 5G base station power amplifier circuit board as an example, and the substrate is selected from FR4 substrate. Preferably, the substrate is a high-frequency substrate with a Tg of 180°C.

[0031] Step S2: Coating a dry resist film on the substrate and exposing the area to be deeply etched using an LDI exposure device, followed by development of the area. The LDI exposure device irradiates the photoresist with ultraviolet light, transferring the designed circuit pattern to the circuit board through a photochemical reaction, thereby providing precise pattern protection for subsequent etching.

[0032] Step S3, the first etching, partially etches the area that needs deep etching, so that the remaining copper thickness in the deep etching area is equivalent to the copper thickness that needs to be etched in the shallow etching area; wherein the upper spray pressure of the deep etching area is controlled to be 2.5-3.0 bar, and the lower spray pressure is 2.5-3.5 kgf / cm 2 , the transmission speed of the circuit board is 1-3m / min, preferably 1.5m / min;

[0033] Please refer to Figure 2 , is a schematic diagram of the etching device for the first etching in the method for manufacturing a stepped circuit board of the present invention. The etching device for the first etching includes a first etching tank 11, a first conveyor belt 12 passing through both ends of the first etching tank 11, a first driving device (not shown) for driving the first conveyor belt 12, and a first spray device 14. Among them, the first spray device 14 includes a first spray pump 141 connected to the first etching tank 11, a first upper spray pipe 142 and a first lower spray pipe 143 connected to the first spray pump 141, a first pressure control valve 144 and a second pressure control valve 145 provided on the first upper spray pipe 142 and the first lower spray pipe 143, and a plurality of first nozzles 146 provided on the first upper spray pipe and the first lower spray pipe. The spray pressure of the first upper spray pipe and the first lower spray pipe is adjusted by controlling the first pressure control valve 144 and the second pressure control valve 145. The spray pressure of the first upper spray pipe 142 is 2.5-3.0 bar, and the spray pressure of the first lower spray pipe 143 is 2.5-3.5 kgf / cm 2 .

[0034] The first nozzle 146 includes a first joint 1461 connected to the first upper spray pipe 142 / the first lower spray pipe 143, and a first spray head 1462 connected to the first joint. The first joint 1461 is a universal joint to facilitate the adjustment of the angle of the first spray head. Specifically, the adjustable angle of the first spray head is 30-90 degrees.

[0035] Step S4, exposing the area requiring shallow etching by an LDI photoexposure device, and then developing the area;

[0036] Step S5, etching for the second time, etching the remaining copper thickness in the deep etching area and the shallow etching area, controlling the upper spray pressure to 1.0-1.5 bar, the lower spray pressure to 1.0-2.0 kgf / cm2, and the transmission speed of the circuit board to 3-7 m / min, preferably 5 m / min;

[0037] Please refer to Figure 3, is a schematic diagram of the etching device for the second etching in the method for manufacturing a stepped circuit board of the present invention. The etching device for the second etching includes a second etching tank 21, a second conveyor belt 22 running through both ends of the second etching tank 21, a second driving device (not shown) for driving the second conveyor belt 22, a second spray device 24, and a wedge-shaped guide plate 25 connected to the side wall of the second etching tank 261. Among them, the second spray device 24 includes a second spray pump 241 connected to the second etching tank 21, a second upper spray pipe 242 and a second lower spray pipe 243 connected to the second spray pump 241, a third pressure control valve 244 and a fourth pressure control valve 245 provided on the second upper spray pipe and the second lower spray pipe, and a plurality of second nozzles 246 provided on the second upper spray pipe and the second lower spray pipe. The spraying pressure of the second upper spray pipe and the second lower spray pipe is adjusted by controlling the third pressure control valve 244 and the fourth pressure control valve 245, wherein the spraying pressure of the second upper spray pipe is 1.0-1.5 bar, and the spraying pressure of the second lower spray pipe is 1.0-2.0 kgf / ㎝2.

[0038] The second nozzle 246 includes a second joint 2461 connected to the second upper spray pipe 242 / second lower spray pipe 243, and a second nozzle 2462 connected to the second joint. The second joint 2461 is a universal joint to facilitate the adjustment of the angle of the second nozzle. Specifically, the adjustable angle of the second nozzle 2462 is 30-90 degrees.

[0039] Wedge-shaped guide plates 25 are located above the second conveyor belt. The etching liquid ejected from the second nozzle 245 flows through the wedge-shaped guide plates, causing the liquid flow to become turbulent. The purpose is to create a physical barrier within the etching tank, change the local flow field, and make the copper ion content in the etching tank more uniform, thereby improving the etching effect. Preferably, there are multiple wedge-shaped guide plates, which are spaced apart.

[0040] Step S6, film removal;

[0041] Step S7: Lamination: Lamination of the inner and outer circuit boards. The lamination adopts a staged temperature-raising lamination process. The lamination parameters of the first stage are: 120°C, 15 MPa, 30 minutes. The lamination parameters of the second stage are: 180°C, 25 MPa, to achieve curing and molding.

[0042] Step S8, copper surface planarization treatment, using chemical mechanical polishing process, polishing liquid pH value is 8.5-9.0, surface roughness Ra ≤ 0.3um.

[0043] The etching solution used in step S3 and step S5 includes copper chloride and hydrogen peroxide, wherein the concentration of copper chloride is 120-140 g / L, the temperature of the etching solution is 45-50° C., and the redox potential is 550-600 mV.

[0044] After testing, the 5G base station power amplifier circuit board of this embodiment, after lamination, X-RAY detection showed that the interlayer offset was less than 25um, the current carrying capacity of the thickened area was increased by 40%, and the impedance consistency was ±3%.

[0045] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for manufacturing a stepped circuit board, characterized in that: The steps include: Step S1: pre-processing the substrate, forming positioning marks of stepped copper thickness areas on the inner layer by LDI laser direct imaging technology; Step S2, coating a dry resist film on the substrate, exposing the area to be deeply etched by an LDI exposure device, and then developing the area; Step S3, the first etching, partially etches the area that needs deep etching, so that the remaining copper thickness in the deep etching area is equivalent to the copper thickness that needs to be etched in the shallow etching area; wherein the upper spray pressure of the deep etching area is controlled to be 2.5-3.0 bar, and the lower spray pressure is 2.5-3.5 kgf / cm 2 , the transmission speed of the circuit board is 1-3m / min; Step S4, exposing the area requiring shallow etching by an LDI photoexposure device, and then developing the area; Step S5, etching for the second time, etching the remaining copper thickness in the deep etching area and the shallow etching area, controlling the upper spray pressure to 1.0-1.5 bar, the lower spray pressure to 1.0-2.0 kgf / cm2, and the transmission speed of the circuit board to 3-7 m / min; Step S6, film removal; Step S7: Lamination: Lamination of the inner and outer circuit boards. The lamination adopts a staged temperature-raising lamination process. The lamination parameters of the first stage are: 120°C, 15 MPa, 30 minutes. The lamination parameters of the second stage are: 180°C, 25 MPa, to achieve curing and molding. Step S8, copper surface planarization treatment, using chemical mechanical polishing process, polishing liquid pH value is 8.5-9.0, surface roughness Ra ≤ 0.3 μm; The etching solution used in step S3 and step S5 includes copper chloride and hydrogen peroxide, wherein the concentration of copper chloride is 120-140 g / L, the temperature of the etching solution is 45-50° C., and the redox potential is 550-600 mV.

2. The method for manufacturing a stepped circuit board according to claim 1, wherein: In step S1 , the substrate is made of FR4.

3. The method for manufacturing a stepped circuit board according to claim 2, wherein: The substrate is a high-frequency substrate with a Tg of 180°C.

4. The method for manufacturing a stepped circuit board according to claim 1, wherein: In step S3 and step S5, the nozzle of the spray etching can be adjusted to an angle of 30-90°.

5. The method for manufacturing a stepped circuit board according to claim 1, wherein: In step S5, during the second etching, a wedge-shaped guide plate is provided on the side wall of the etching tank to make the sprayed etching liquid form a turbulent flow.

Images