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CN-121995707-A - Method for manufacturing exposure alignment of through hole exposure without alignment offset and application

CN121995707ACN 121995707 ACN121995707 ACN 121995707ACN-121995707-A

Abstract

The invention relates to the technical field of PCB manufacture and discloses a method for manufacturing exposure alignment of a through hole without alignment offset, comprising the following steps of providing a PCB board which is electroplated, wherein the PCB board is provided with at least one through hole; laminating a first positive dry film on the C/S surface of the PCB, wherein the photosensitive wavelength of the first positive dry film is 365nm and the light transmittance of the first positive dry film for the wavelength of 405nm is more than 90%, no coloring agent is added in the first positive dry film, and laminating a second positive dry film on the S/S surface of the PCB, wherein the photosensitive wavelength of the second positive dry film is 405nm and the light transmittance of the second positive dry film for the wavelength of 365nm is more than 90%. The method for manufacturing the exposure and alignment of the through hole without alignment offset aims to solve the problems of inaccurate opening position, uneven plating layer in the hole, redundant plating layer on the plate surface and the like caused by alignment offset in the traditional negative dry film alignment and exposure method.

Inventors

  • LU FAMING
  • ZHANG TAO
  • Bian heping

Assignees

  • 昆山沪利微电有限公司

Dates

Publication Date
20260508
Application Date
20260205

Claims (10)

  1. 1. The exposure alignment manufacturing method of the through hole exposure without alignment offset is characterized by comprising the following steps of: S1, providing a PCB board with at least one through hole after electroplating; S2, laminating a first positive dry film on the C/S surface of the PCB, wherein the photosensitive wavelength of the first positive dry film is 365nm, the light transmittance of the first positive dry film to 405nm wavelength is more than 90%, and no colorant is added in the first positive dry film; s3, laminating a second positive dry film on the S/S surface of the PCB, wherein the photosensitive wavelength of the second positive dry film is 405nm, the light transmittance of the second positive dry film to 365nm wavelength is more than 90%, and no colorant is added in the second positive dry film; S4, performing first exposure from the C/S surface by using a 405nm wavelength light source, so that light rays penetrate through the first positive dry film and the through holes and then irradiate on the second positive dry film of the hole area of the S/S surface, and performing polymerization reaction; s5, performing secondary exposure from the S/S surface by using a 365nm wavelength light source, so that light rays penetrate through the second positive dry film and the through holes and then irradiate onto the first positive dry film of the C/S surface hole area, and performing polymerization reaction; and S6, developing the PCB board subjected to the double exposure, and removing the polymerized dry film part to expose the orifice.
  2. 2. The method for manufacturing the exposure alignment of the through hole exposure without the alignment offset according to claim 1, wherein the photosensitive peak wavelength of the first positive dry film in the step S2 is 365nm, the film thickness is 20-30 μm, the light absorption coefficient at 365nm wavelength is 0.8-1.2 μm -1 , the transmittance of light with 405nm wavelength is more than 95%, the resin matrix of the first positive dry film is acrylic ester polymer, and the photoinitiator is aromatic ketone sensitive to 365nm wavelength; The photosensitive peak wavelength of the second positive dry film in the S3 is 405nm, the film thickness is 20-30 mu m, the light absorption coefficient at the wavelength of 405nm is 0.9-1.3 mu m -1 , the transmittance of 365nm light is more than 95%, the resin matrix of the second positive dry film is methacrylate polymer, the photoinitiator is titanium complex or antimony complex sensitive to the wavelength of 405nm, and the spectral transmittance curves of the first positive dry film and the second positive dry film in the respective non-photosensitive wave bands show the characteristics of a platform.
  3. 3. The method for manufacturing the exposure alignment of the through hole exposure without alignment offset according to claim 1, wherein the exposure energy of the first exposure in the step S4 is 80-120mJ/cm 2 , the exposure time is 8-15 seconds, the power density of a light source is 8-12mW/cm 2 , the 405nm light source is arranged in an LED array mode, and the output power of a single LED chip is 3-5W; The exposure energy of the secondary exposure in the step S5 is 60-100mJ/cm 2 , the exposure time is 6-12 seconds, the power density of a light source is 10-15mW/cm 2 , a 365nm light source adopts a high-pressure mercury lamp or an LED light source, and a wavelength screening filter is arranged to enable light rays of 365+/-5 nm wave bands to pass through; The energy parameters of the first exposure and the second exposure are independently adjusted according to the dry film thickness, the aperture of the through hole and the depth of the through hole, and the energy control is realized by adjusting the exposure time or the power of the light source, so that the light energy density penetrating through the through hole to reach the opposite side orifice reaches 1.2-1.8 times of the energy of the polymerization threshold of the side dry film.
  4. 4. The exposure alignment manufacturing method of the through hole exposure without alignment offset according to claim 1, wherein the S2 and S3 are dry film laminated by a hot-pressing roller lamination method, the lamination temperature is 95-115 ℃, the lamination pressure is 0.3-0.5MPa, the lamination speed is 1.0-2.0m/min, the surface of the hot-pressing roller is made of silicone rubber, and the hardness is 70-85 shore a; Pretreating the surface of the PCB before lamination, and adopting microetching liquid to treat for 30-60 seconds or adopting plasma cleaning treatment for 2-5 minutes to remove surface oxides and greasy dirt; The first positive dry film and the second positive dry film are of three-layer structures and comprise a polyester film protective layer, a photosensitive resin layer and a polyethylene isolating film, the polyethylene isolating film is removed firstly during lamination and then is subjected to hot pressing lamination, the polyester film protective layer is reserved after lamination until an exposure process, the non-photosensitive areas of the first positive dry film and the second positive dry film after polymerization keep light transmittance to light rays of a non-photosensitive wave band, and the transmittance attenuation is less than 5%.
  5. 5. The exposure alignment manufacturing method of the through hole exposure without alignment offset according to claim 1, wherein in the step S6, a sodium carbonate aqueous solution with the concentration of 0.8-1.2% is used as a developing solution, the pH value of the developing solution is controlled to be 10.5-11.5, the developing temperature is 25-35 ℃, the spraying pressure is 1.5-2.5bar, the distance between a nozzle and a plate surface is 80-120mm, and the developing time is 50-70 seconds; The developing process is carried out by adopting a spray type developing machine, an upper spraying system and a lower spraying system are arranged to simultaneously develop the C/S surface and the S/S surface of the PCB respectively, the circulating flow of the developing solution is 150-250L/min, deionized water is adopted for flushing after the developing process, the flushing time is 20-40 seconds, the resistivity of flushing water is more than 10MΩ & cm, then hot air drying is adopted, the drying temperature is 60-80 ℃, the drying time is 40-80 seconds, the conductivity of the developing solution is monitored in the developing process, fresh developing solution is replaced when the conductivity rises to be more than 20% of the initial value, and the waste developing solution is discharged after the neutralizing treatment.
  6. 6. The method for manufacturing the exposure alignment of the through hole exposure without alignment offset according to claim 1, wherein an LED exposure machine or an LDI laser direct imaging exposure machine is used as a light source in the S4 and the S5, the LED exposure machine is provided with an LED light source array with the wavelength of 405+/-5 nm and an LED light source array with the wavelength of 365+/-5 nm, and the two groups of light sources can independently control a switch and power output; The method comprises the steps of carrying out primary exposure and secondary exposure respectively by adopting two independent single-wavelength LED exposure machines, wherein the exposure machines are provided with vacuum adsorption platforms, the vacuum degree is between-0.06 and-0.08 MPa, the smooth lamination of a PCB board in the exposure process is ensured, the primary exposure and the secondary exposure both adopt a whole board surface exposure mode, an exposure area covers the whole board surface, no film or mask plate is required to carry out pattern transfer, no pattern alignment operation is required, the distance between an exposure light source and the board surface is 300-500mm, the illumination uniformity is controlled within +/-5%, the nitrogen atmosphere is kept in the exposure process or the exposure is carried out in the air, and the temperature of the exposure is controlled between 20 ℃ and 25 ℃.
  7. 7. The exposure alignment manufacturing method of the through hole exposure without alignment offset according to claim 1 is characterized in that the PCB in the S1 is a semi-finished board with the processes of drilling, copper deposition and full-board electroplating completed, the aperture of the through hole is 0.2-0.5mm, the depth of the through hole is 0.8-2.0mm, the ratio of the aperture to the board thickness is 1:2-1:8, the thickness of a copper layer after full-board electroplating is 15-35 mu m, and the thickness of a copper layer on a hole wall is 20-40 mu m; The PCB is of a single-panel, double-panel or multi-layer structure, and the substrate is an FR-4 epoxy glass fiber board, CEM-1 composite substrate or polyimide flexible substrate, is suitable for manufacturing a plating-resisting pattern with large opening size, pore diameter and the like, and is used for a subsequent single-hole selective plating process.
  8. 8. The exposure and alignment manufacturing method for the through hole exposure without alignment offset according to claim 1, wherein after the S6 development, circular windows are respectively formed at the through hole openings of the C/S surface and the S/S surface, the difference between the diameter of the circular windows and the size of the through hole aperture is controlled within +/-0.05 mm, and the offset between the central position of the windows and the central position of the through hole is less than 0.03mm; The other areas except the hole opening area of the through hole on the plate surface are reserved with unpolymerized first positive dry film and second positive dry film as a plating resistance layer, the thickness of the plating resistance layer is kept at 18-28 mu m, the adhesion force between the plating resistance layer and the copper surface is more than 8N/cm, and the surface of the plating resistance layer is flat and free from bubbles, wrinkles and pinhole defects; after development, the windowing quality is checked by visual inspection or automatic optical detection equipment, whether the windowing edge is smooth or not and whether residual film or over-corrosion phenomenon exists is checked, and the qualification standard is that the windowing edge is neat, the copper surface of the orifice is completely exposed, and the plate surface resistance coating is complete and has no damage.
  9. 9. The method for producing exposure alignment of through holes without alignment shift according to claim 1, further comprising the steps of, after S6: s7, detecting the developed PCB by adopting automatic optical detection equipment, wherein the detection content comprises the diameter of an orifice windowing, the displacement of the windowing position, the integrity of a plating resistance layer and the quality of the windowing edge, the detection precision is +/-0.01 mm, and marking and removing unqualified products; S8, performing hole exposing electroplating procedure on the PCB which is qualified in inspection, placing the PCB into an electroplating tank, electroplating by adopting copper sulfate electroplating solution, wherein the electroplating solution comprises 60-80g/L of copper sulfate and 180-220g/L of sulfuric acid, adding a gloss agent and a leveling agent, wherein the electroplating current density is 1.5-3.0A/dm 2 , the electroplating time is calculated according to the thickness of a required coating, current only enters the inside of a through hole through a window opening area in the electroplating process, a copper layer is deposited on the wall of the through hole, the thickness of the coating is 10-25 mu m, the area of the board covered by a resistance coating does not generate electroplating reaction, and the thickness increment of the copper layer is less than 2 mu m; And S9, removing the plating resist by using alkaline stripping solution, wherein the concentration of the stripping solution is 2-4% of sodium hydroxide solution, the stripping temperature is 40-60 ℃, and the stripping time is 3-8 minutes.
  10. 10. The application of the exposure alignment manufacturing method for the through hole exposure without alignment offset according to any one of claims 1 to 9 is characterized in that the method is applied to manufacturing of a PCB requiring only a plating hole process, and comprises manufacturing of a microwave radio frequency board, a blind hole board, a high density interconnection board HDI, a communication board, an automobile electronic board and a server main board for radar products, wherein the technical specification of the PCB product is that the number of circuit layers is 4 to 16, the minimum line width/line distance is 0.075/0.075mm, the aperture of the through hole is 0.2 to 0.5mm, the thickness of hole copper is 25 to 50 mu m, the thickness of surface copper is 18 to 35 mu m, the thickness difference between the hole copper and the surface copper is controlled within 10 mu m, the method is particularly suitable for manufacturing of high-frequency high-speed circuit boards requiring strict control of impedance values for copper thickness difference of different positions in the hole is less than 15%, and the thickness sensitivity of the surface copper is sensitive to the surface copper, and the impedance offset and signal loss caused by excessive surface copper thickness are avoided through selective hole electroplating.

Description

Method for manufacturing exposure alignment of through hole exposure without alignment offset and application Technical Field The invention relates to the technical field of PCB manufacture, in particular to a through hole exposure alignment manufacturing method without alignment offset and application thereof. Background In the PCB manufacturing process, for products requiring thickening of copper layers in holes and strict control of the thickness of copper layers on the board surface, a hole-only plating process is generally adopted, i.e. only copper layers are deposited in the through holes during the plating process, and no plating occurs on the board surface area. To achieve this, it is necessary to make a plating resist pattern on the surface of the PCB board so that the through-hole openings are exposed and the board surface is covered with the plating resist. The traditional method adopts a negative dry film to carry out exposure and development to manufacture a plating resist pattern, namely, after the negative dry films are respectively attached to the two sides of a PCB, the film is used for carrying out alignment exposure, so that an orifice area is not exposed to light and is kept in a soluble state, a plate surface area is exposed and solidified to form a plating resist layer, and the orifice is exposed after development. The method is widely applied to the manufacture of PCB products with high requirements on the thickness of the hole copper, such as radar products, high-density interconnection boards and the like. However, the conventional negative dry film alignment exposure method has a significant alignment accuracy defect. Because the PCB needs to be subjected to film alignment exposure on the C/S surface and the S/S surface respectively, and film patterns of small-aperture through holes (such as 0.2-0.5 mm) are difficult to align, even if high-precision alignment equipment is adopted, the deviation of 0.05-0.15mm between the film patterns and actual hole sites can be caused due to manual operation errors and repeated positioning precision limitation of the equipment. The alignment offset causes that the window opening position of the hole opening after development is not concentric with the position of the through hole, the window opening edge possibly invades the copper layer of the plate surface or can not completely expose the hole opening, and the thickness of the plating layer in the hole is uneven or the plate surface generates redundant plating layer during subsequent electroplating. Especially for the tiny through holes with the aperture smaller than 0.3mm, the proportion of the para-position offset to the aperture is larger, the product quality and the yield are seriously affected, and the method becomes a key technical bottleneck for restricting the high-precision PCB manufacture. Disclosure of Invention The invention aims to solve the problems of inaccurate opening position, uneven plating layer in holes, redundant plating layer on the plate surface and the like caused by alignment offset in the traditional negative dry film alignment exposure method, and provides a through hole exposure alignment manufacturing method without alignment offset and application thereof. The technical scheme for solving the technical problems is as follows: a method for manufacturing exposure alignment of a through hole without alignment offset comprises the following steps: S1, providing a PCB board with at least one through hole after electroplating; S2, laminating a first positive dry film on the C/S surface of the PCB, wherein the photosensitive wavelength of the first positive dry film is 365nm, the light transmittance of the first positive dry film to 405nm wavelength is more than 90%, and no colorant is added in the first positive dry film; s3, laminating a second positive dry film on the S/S surface of the PCB, wherein the photosensitive wavelength of the second positive dry film is 405nm, the light transmittance of the second positive dry film to 365nm wavelength is more than 90%, and no colorant is added in the second positive dry film; S4, performing first exposure from the C/S surface by using a 405nm wavelength light source, so that light rays penetrate through the first positive dry film and the through holes and then irradiate on the second positive dry film of the hole area of the S/S surface, and performing polymerization reaction; s5, performing secondary exposure from the S/S surface by using a 365nm wavelength light source, so that light rays penetrate through the second positive dry film and the through holes and then irradiate onto the first positive dry film of the C/S surface hole area, and performing polymerization reaction; and S6, developing the PCB board subjected to the double exposure, and removing the polymerized dry film part to expose the orifice. On the basis of the technical scheme, the invention can be improved as follows. Furthermore, the photosensitive peak