Processing technology of optical module circuit board

Abstract

The invention relates to a processing technology of an optical module circuit board, which comprises the following steps of: cutting a double-sided copper-clad plate, cutting the plate, and manufacturing an inner-layer circuit to obtain an inner-layer plate; performing hot melting and riveting on the inner-layer plate and then adding layers to obtain a first multi-layer plate; the first multilayer board is subjected to browning copper reduction, laser target burning, plasma degumming, copper deposition and electroplating, vacuum tree plug, high-cutting grinding and circuit manufacturing; performing double-sided layer adding on the treated first multilayer board to obtain a second multilayer board, and performing browning copper reduction, laser target burning, plasma degumming, copper deposition electroplating, vacuum tree plug, high-cutting grinding and circuit manufacturing on the second multilayer board to obtain a semi-finished board; and performing finger gold plating, LPI printing, vacuum etching and the like on the semi-finished board to obtain a finished board. The processing technology can meet the market requirements of 800G optical module products, the high-speed resistance yield is improved, and the mass production capability of the optical module technology is realized.

Description

Technical Field

[0001] This application relates to the technology of circuit board processing, and specifically to a processing technology for optical module circuit boards. Background Art

[0002] With the popularization of 5G and the rapid development of artificial intelligence (AI), products related to high-speed data transmission and the application of high-speed transmission technologies have shown an explosive growth. The update and iteration of optoelectronic signal conversion and technology have greatly promoted the high-speed development of the optical communication market. Among them, as the basic hardware for massive data transmission in optoelectronic communication, optical modules have gradually developed from 10G and 25G to 400G and even 800G. For PCB board products of 800G optical module type, due to their strict high-speed impedance control requirements and the processing difficulty of high-speed materials, although PCB board factories in the industry have conducted a lot of research and process improvements on their processing technologies, in the application process of materials at the M8 level, innovative process development and the improvement of high-speed impedance yield rate and technical improvement are still required. Summary of the Invention

[0003] In order to overcome the above defects, this application provides a processing technology for optical module circuit boards, which can meet the market demand of 800G optical module products, improve the high-speed impedance yield rate, and realize the mass production capacity of optical module processes.

[0004] The technical solution adopted by this application to solve its technical problems is as follows:

[0005] A processing technology for optical module circuit boards includes the following steps:

[0006] Cutting: Take a double-sided copper clad laminate, perform cutting, panel cutting, and inner layer circuit manufacturing on the double-sided copper clad laminate to obtain an inner layer board;

[0007] First lamination: Thermally rivet and add layers to two or more inner layer boards to obtain a first multi-layer board;

[0008] Processing of the first multi-layer board: Perform brownization and copper reduction, laser burning of targets, laser drilling, mechanical drilling of blind holes, drilling of buried holes, plasma degumming, copper plating by immersion, vacuum plugging, high-precision grinding, and circuit manufacturing on the first multi-layer board;

[0009] Second lamination: Add layers on both sides of the processed first multi-layer board to obtain a second multi-layer board, and perform brownization and copper reduction, laser burning of targets, laser drilling, mechanical drilling of blind holes, drilling of buried holes, plasma degumming, copper plating by immersion, vacuum plugging, high-precision grinding, and circuit manufacturing on the second multi-layer board to obtain a semi-finished board. The second lamination process can be repeated as needed to obtain the required number of layers;

[0010] Post-treatment: The semi-finished board is subjected to gold-plated fingers, LPI printing, vacuum etching, baking, immersion gold, text, testing, and packaging processes to obtain the finished board;

[0011] Among them, in the process of drilling blind holes by machine, a cross-layer depth-controlled machine is used to drill blind holes, and the drilling depth is set at 6.5 ± 1 mil, the depth of the blind hole is 6.5 ± 1 mil, and after drilling the blind hole, a laser is used to drill a through-hole with a depth of 6 ± 1 mil;

[0012] Laser ablation is used to form positioned target holes on the outer layer, the second outer layer, and the third outer layer, that is, the alignment system uses ablation positioning.

[0013] Optionally, when the second lamination process needs to be carried out three or more times, the blanking process includes: taking a double-sided copper clad laminate, performing blanking, cutting, drilling positioning holes, brownization and copper reduction, laser drilling, plasma treatment, horizontal copper deposition, electroplating filling, and making inner layer circuits on the double-sided copper clad laminate to obtain an inner layer board.

[0014] Optionally, the conditions of the blanking process include: baking temperature 190°C ± 10°C, baking time 3h ± 1h, lamination time 4h ± 1h, lamination pressure 500 psi ± 50 psi, and heating rate 3 - 4°C / min.

[0015] Optionally, in the vacuum plugging process, a vacuum negative pressure plugging machine is used, an aluminum sheet stencil is set up, and after alignment, the machine-drilled blind holes are filled with resin to ensure that the holes are filled completely without bubbles.

[0016] Optionally, the method for making the aluminum sheet stencil includes the following steps:

[0017] Drilling: Copper-free substrates are clamped above and below the aluminum sheet, and numerical control drilling is carried out according to the holes that need to be filled with resin. The thickness of the aluminum sheet is 0.2 mm ± 0.05 mm; the thickness of the copper-free substrate is 0.1 mm ± 0.02 mm, and the size is 600 mm * 675 mm;

[0018] Aluminum sheet cleaning: Use 2000-mesh sandpaper to polish both sides of the effective hole-filling area in the board until it is flat without burrs, and use 200-mesh coarse sandpaper to polish the 50-mm-wide area outside the non-hole-filling area until it is rough;

[0019] Attaching the perforated aluminum sheet to the stencil: Attach the drilled aluminum sheet to the stencil according to the size of the aluminum sheet;

[0020] Gluing: Apply Nanbao resin glue to the 80-mm-wide area where the stencil and the aluminum sheet are attached, and let it stand for 2H to cure the resin;

[0021] Mesh cutting: Cut off the silk screen in the hole-filling area, and attach aluminum foil tape to the contact area between the silk screen and the aluminum sheet to prevent the silk screen and glue residue from being exposed.

[0022] Optionally, the conditions for plasma degumming are as follows: treatment time 30 - 40 min, vacuum degree 200 ± 20 mtorr, power 4 - 10 KW, temperature 75 ± 5 °C.

[0023] The beneficial effects of this application are as follows: When drilling holes in this application, the process of drilling blind holes with a cross-layer depth control machine drill is adopted. After the depth control is completed, the blind holes are detected by AOI scanning for blind hole drilling omission, and a special drill with a self-ground 148° is used to ensure the accuracy of drilling. The process of burning the target of high-order HDI products is adopted, that is, the current core layer alignment system is changed to burning target alignment, which improves the docking accuracy of HDI blind holes, reduces the scrapping of offset holes, improves the production efficiency of the sub-outer layer and the outer layer of HDI products, and reduces non-exposure. This processing technology can meet the market demand of 800G optical module products, improve the high-speed impedance yield, and realize the mass production capacity of optical module technology; solve the problems of blind hole alignment accuracy, 1OZ copper thickness high-precision depth control cross-layer blind hole processing, and segmented finger reverse etching hanging gold; reduce production costs, simplify the production process flow, enable the process to have the ability to be introduced into mass production, and the production process is simple and controllable. Description of the Drawings

[0024] Figure 1 It is a diagram of the resistance test series conduction coupon scheme in this application. Specific Embodiments

[0025] Next, the technical solutions in the embodiments of this application will be clearly and completely described in combination with the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0026] A processing technology for an optical module circuit board includes the following steps:

[0027] Blanking: Take a double-sided copper clad laminate, perform blanking, cutting, and inner layer circuit manufacturing on the double-sided copper clad laminate to obtain an inner layer board;

[0028] First lamination: Thermally rivet and add layers to two or more inner layer boards to obtain a first multi-layer board;

[0029] Processing of the first multi-layer board: Perform treatment on the first multi-layer board including brownization and copper reduction, laser burning of the target, laser drilling, machine drilling of blind holes, drilling of buried holes, plasma degumming, copper deposition and electroplating, vacuum plugging, high-speed cutting and grinding, and circuit manufacturing.

[0030] Second lamination: The processed first multi-layer board is subjected to double-sided build-up to obtain a second multi-layer board, and the second multi-layer board is subjected to brown oxidation and copper reduction, laser burning of targets, laser drilling, mechanical drilling of blind holes, drilling of buried holes, plasma degumming, copper deposition and electroplating, vacuum plugging, high-precision grinding, and circuit production processes to obtain a semi-finished board. The second lamination process can be repeated as needed to obtain the required number of layers;

[0031] Post-treatment: The semi-finished board is subjected to gold plating of fingers, printing of LPI, vacuum etching, baking, immersion gold, text, testing, and packaging processes to obtain a finished board;

[0032] Among them, in the process of mechanical drilling of blind holes, a cross-layer depth-controlled mechanical drill is used for blind holes, the drilling depth is set at 6.5±1 mil, the depth of the blind hole is 6.5±1 mil, and after drilling the blind hole, a laser is used to drill a through-hole with a depth of 6±1 mil;

[0033] Through laser burning of targets, positioned target holes are formed on the outer layer, the second outer layer, and the third outer layer, that is, the alignment system uses target burning for positioning. In the drilling process of this application, a cross-layer depth-controlled mechanical drill is used for blind holes. After the depth-controlled drilling, the blind holes are detected by AOI scanning for missed drilling, and a special drill with an angle of 148° by self-grinding is used to ensure the accuracy of drilling; the target burning process of high-order HDI products is adopted, that is, the current core layer alignment system is changed to target burning alignment, which improves the alignment accuracy of HDI blind holes, reduces the rejection rate of offset holes, improves the production efficiency of the second outer layer and the outer layer of HDI products, and reduces the exposure rejection rate. This processing technology can meet the market demand of 800G optical module products, improve the high-speed impedance yield rate, and realize the mass production capacity of optical module technology; solve the problems of blind hole alignment accuracy, the processing of 1OZ copper thickness high-precision depth-controlled cross-layer blind holes, and the problem of anti-etching and suspended gold of segmented fingers; reduce the production cost, simplify the production process flow, enable the process to have the ability to be introduced into mass production, and the production process is simple and controllable.

[0034] When the second lamination process needs to be carried out three or more times, the blanking process includes: taking a double-sided copper clad laminate, and performing blanking, cutting, drilling of positioning holes, brown oxidation and copper reduction, laser drilling, plasma treatment, horizontal copper deposition, electroplating filling, and production of inner layer circuits on the double-sided copper clad laminate to obtain an inner layer board.

[0035] The conditions of the blanking process include: baking temperature 190℃±10℃, baking time 3h±1h, lamination time 4h±1h, lamination pressure 500psi±50psi, and heating rate 3-4℃ / min. High-temperature and long-time stress relief baking is carried out on the M8 high-speed material, and a special pressing process with long time and large pressure is carried out to ensure the blanking of the M8 high-speed material.

[0036] In the vacuum plugging process, a vacuum negative pressure plugging machine is used, an aluminum sheet mesh plate is installed, and after alignment, the mechanical drill blind holes are filled with resin to ensure that the plugging is full and there are no bubbles.

[0037] The manufacturing method of the aluminum sheet mesh panel includes the following steps:

[0038] Drilling: Sandwich a copper-free substrate above and below the aluminum sheet, and perform numerical control drilling according to the holes that need to be filled with resin. The thickness of the aluminum sheet is 0.2mm ± 0.05mm; the thickness of the copper-free substrate is 0.1mm ± 0.02mm, and the size is 600mm * 675mm;

[0039] Aluminum sheet cleaning: Use 2000-mesh sandpaper to polish both sides of the effective hole-filling area inside the plate until it is flat without burrs, and use 200-mesh coarse sandpaper to polish the 50mm-wide area outside the non-hole-filling area until it is rough;

[0040] Attaching the aluminum sheet to the empty mesh: Attach the drilled aluminum sheet to the mesh panel according to the size of the aluminum sheet;

[0041] Gluing: Apply Nanbao resin glue to the 80mm-wide area where the mesh panel and the aluminum sheet are attached, and let it stand for 2H to cure the resin;

[0042] Mesh cutting: Cut off the wire mesh in the hole-filling area, and attach aluminum foil tape to the area where the wire mesh contacts the aluminum sheet to prevent the wire mesh and glue residue foreign objects from being exposed.

[0043] The conditions for the plasma degumming are: treatment time 30 - 40min, vacuum degree 200 ± 20mtorr, power 4 - 10KW, temperature 75 ± 5°C.

[0044] Example 1: 10L board three-stage two-pressure process

[0045] Cutting / plate cutting → Inner layer → Laminating and punching → Inner layer AOI → Laminating 1 → Brownification and copper reduction → Laser burning the target 1 → Laser drilling 1 [hole diameter 4mil] → Back drilling → Pumice → Back drilling AOI → Laser drilling 2 [hole diameter 6mil] → Drilling buried holes → Plasma degumming 1 → Horizontal PTH → Pulse electroplating → Filling dry film → Electroplating filling → Sub-outer layer dry film → Sub-outer layer vacuum etching → Sub-outer layer AOI → Laminating 2 → Brownification and copper reduction → Laser burning the target → Laser drilling 3 → Drilling → Plasma degumming 2 → High cutting and grinding → Horizontal PTH → Electroplating filling → Vacuum resin plugging → High cutting and grinding → PTH / VCP → Dry film → Vacuum etching → Middle test AOI → Resistance value testing → Printing LPI1 → Gold plating fingers → Printing LPI2 → Vacuum etching → Stripping the film → Baking (150°C * 1H) → Positive film wet film → Selective dry film → Solder mask baking → Immersion gold → Selective stripping the film → Lettering → Plate warping → Laser target → Forming 1 → V-CUT → Blind fishing → Forming → Chamfering → Testing → Measuring impedance → Final inspection → Packaging.

[0046] The specific steps are as follows:

[0047] 1. Cutting / plate cutting:

[0048] Board type: R-5795(N) with 1OZ copper thickness, raw material size 1041mm * 1244mm. Cutting size: 410mm * 515mm, baked at 190°C for 3H after cutting.

[0049] 2. Inner layer: Inner layer circuits are formed on the inner core board.

[0050] Graphic pre-expansion ratio: X = 1.00096, Y = 1.00164.

[0051] 3. Laminating and punching: CCD grabs the punching Mark points and punches 8 rivet holes in one go.

[0052] 4. Inner layer AOI: Optically scans to detect circuit pattern defects.

[0053] 5. Laminating 1: The patterns of 6 layers of 3 inner core boards of L3 / L4, L5 / L6, and L7 / L8 are hot-melted and riveted with rivets. After combining copper foil and PP sheets and laminating, the sub-outer layer (i.e., L2 / L9 layer) multilayer board is processed.

[0054] Copper foil: 0.33OZ, PP type: 1080-RC 70%.

[0055] 6. Brown oxidation and copper reduction: Through treatment with brown oxidation solution on the laminate, while thinning the copper, a thin blackish-brown brown oxidation film is formed, which is convenient for absorbing the laser energy during the laser drilling process in the next process and avoiding poor laser hole patterns caused by reflected laser energy.

[0056] 7. Laser burning of the target: By using the laser ablation method, the preset target patterns on the inner layer are exposed, preparing for target positioning and recognition for laser drilling 1 to process the blind holes of L2-L3 and L9-L8 layers.

[0057] 8. Laser drilling 1: CCD grabs the targets of laser burning of the target and produces and processes the blind holes of L2-L3 and L9-L8 layers.

[0058] 9. Machine drilling of blind holes L2-L4: Using back drilling for precise processing, with phenolic backing plate and special 0.25 * 5.0 * 165° angle drill bit, setting the drilling depth at 6 ± 1mil, precisely processing the cross-layer blind holes of L2-L4 layers; at the same time, drilling 2.0mm blind hole positioning holes for laser drilling 2 in the middle of the targets of laser burning of the target.

[0059] Back drilling depth control: Sidewall 5.5 ± 1mil, center thickness 6 ± 1mil, bottom residual thickness control 1.5 ± 1mil, diameter 0.25 ± 0.05mm.

[0060] 10. X-RAY target drilling: For the reserved inner layer target patterns, use X-RAY rays to grab the graphic targets and drill 3.1mm target holes for use in the second back drilling of the L9-L7 layer back holes.

[0061] 11. Machine-drilled blind holes L9 - L7: Use back drilling for precision processing, paired with phenolic backing plates and special 0.25 * 5.0 * 165° angle drill bits. Set the drilling depth to 6 ± 1 mil to precision process the through-layer blind holes between L2 - L4 layers; at the same time, drill a 2.0 mm laser drilling 2 blind hole positioning hole in the middle of the laser ablation target point.

[0062] Back drilling depth control: Sidewall 5.5 ± 1 mil, center thickness 6 ± 1 mil, bottom residual thickness control 1.5 ± 1 mil, diameter 0.25 ± 0.05 mm.

[0063] 12. Laser drilling 2 [hole diameter 6 mil]:

[0064] The CCD grabs the 2.0 mm back drilling target points of L2 - L4 layers inside the back drilling holes of L2 - L3 layers, and laser processes the blind holes in the holes of L2 - L3 layers. The CCD grabs the 2.0 mm back drilling target points of L9 - L7 layers inside the back drilling holes of L9 - L7 layers, and laser processes the blind holes in the holes of L9 - L7 layers.

[0065] 13. Drilled buried vias: Use mechanical drilling to process the buried through-holes of L2 - L9 layers.

[0066] 14. Pumice: Use the emery sandblasting process to clean the black-brown copper film on the board surface to facilitate the blind hole AOI detection and processing in the next process.

[0067] 15. Blind hole AOI: Use the Kangle AOI vision automatic scanning level to detect the drilling quality status at the bottom of the blind hole to ensure that there are no problems of exposed copper due to over-drilling or under-drilling.

[0068] 16. Plasma desmearing 1:

[0069] Use the plasma process to perform plasma cleaning on the drilled boards [first-order blind holes, through-layer blind holes, buried through-holes] to remove the resin gum residues on the inner wall of the holes, and prepare for the PTH electroless copper plating in the next process. Desmearing parameters: See Table 1 below

[0070] Table 1: Desmearing parameters

[0071]

[0072] 17. Horizontal PTH:

[0073] Use a horizontal electroless copper plating line to deposit a thin layer of copper on the inner walls of [first-order blind holes, through-layer blind holes, buried through-holes].

[0074] 18. Electroplating filling:

[0075] Perform gantry electroplating filling on the circuit board that has completed electroless copper plating;

[0076] Plating is carried out once for 90 minutes with 10 ASF, and after flipping the chuck, plating is carried out a second time for 90 minutes with 10 ASF; the surface copper is controlled at 1.3 ± 0.2 mil, the stepped position at the bottom of the blind hole needs to be filled, and the depression depth is controlled at 6 mil ± 1 mil.

[0077] 19. Vacuum tree plug 1:

[0078] A vacuum plug hole machine is used with an aluminum sheet stencil to fill the through buried holes and interlayer blind holes with resin.

[0079]

Processing method of aluminum sheet stencil

[0080] Use a 0.2 mm thick aluminum sheet, sandwich 0.1 mm FR-4 thin copper-free substrates on the top and bottom, and carry out numerical control drilling according to the holes that need to be filled with resin [the drilling ratio needs to be consistent with the pnl, that is, the actual PCB board expansion and contraction in the base material board]. The drilling hole diameter is 0.05 mm larger than the resin filling hole diameter on each side. There should be no burrs at the hole opening during the processing of the aluminum sheet; the aluminum sheet is 80 mm larger than the PCB working piece size on each side; and the outer 50 mm wide area is polished rough with 200-mesh coarse sandpaper; attach the processed aluminum sheet to a 90-mesh empty wire mesh, attach it to the inside of the wire mesh with aluminum foil glue, then apply Nanbao resin glue on the outside of the wire mesh, wait for 2 hours after standing still for the resin glue to cure, and cut off the wire mesh within the pnl size with a blade.

[0081] Specifically, it includes the following steps:

[0082] ① Prepare 1 piece of 0.2 mm aluminum sheet and 2 pieces of 0.1 mm copper-free substrates with a size of 600 mm * 675 mm;

[0083] ② Drilling program: Expansion ratio DX = 1.00072, DY = 1.00078;

[0084] ③ Drilling processing: Use the drilling program parameters of

aluminum substrate

[0085] ④ Aluminum sheet cleaning: Use 2000-mesh sandpaper to polish both sides of the effective plug hole area within the pnl to be flat without burrs, and use 200-mesh coarse sandpaper to polish the 50 mm wide area outside the non-plug hole area rough;

[0086] ⑤ Attach the aluminum sheet to the empty wire mesh: Attach the drilled aluminum sheet to the stencil according to the aluminum sheet size

[0087] ⑥ Glue brushing: Apply Nanbao resin glue to the 80 mm wide area of the stencil-aluminum sheet attachment area. And let it stand for 2 hours to cure the resin.

[0088] ⑦ Mesh cutting: Cut off the wire mesh within the plug hole area, and attach aluminum foil tape to the contact area between the wire mesh and the aluminum sheet to prevent the wire mesh and glue residue foreign objects from being exposed;

[0089] Use a vacuum negative pressure plugging machine, set up an aluminum mesh board, and after alignment, fill the machine-drilled blind holes with resin to ensure that the holes are filled completely without bubbles.

[0090] 20. High-speed cutting and grinding 1

[0091] For the surface resin that has been filled completely and dried and cured, use a ceramic brush roll + non-woven brush roll to grind and level it, removing the excess resin residue on the surface to ensure that the hole openings are flat without protrusions.

[0092] 21. Vacuum resin plugging 2

[0093] Refer to the 19th step above to process the blind holes of L9 - L7 layers for resin plugging.

[0094] 22. High-speed cutting and grinding 2

[0095] Refer to the 20th step above to use a ceramic brush roll + non-woven brush roll to grind and level the surface resin of the blind holes of L9 - L7 layers that have been filled completely and dried and cured, removing the excess resin residue on the surface to ensure that the hole openings are flat without protrusions.

[0096] 22. PTH / Cover hole electroplating

[0097] Cover a layer of copper on the hole openings of the machine-drilled blind holes and buried holes that have been resin-filled and ground and leveled. The thickness of the cover hole copper is 0.5 mil, and the surface copper thickness is controlled at 1.45 - 1.7 mil.

[0098] 23. Sub-outer layer dry film (sub-outer layer: L2 / L9 layers)

[0099] For the sub-outer layer PCB that has completed the buried hole, machine-drilled blind hole, and cover hole processes, process the sub-outer layer circuit through LDI image transfer technology. Dry film model: LDI8338, dry film thickness 1.5 mil.

[0100] 24. Sub-outer layer vacuum etching

[0101] For the PCB board with the sub-outer layer image transferred and covered with anti-etch dry film, perform acid etching to etch out the circuit pattern and remove the anti-etch layer dry film.

[0102] 25. Sub-outer layer AOI

[0103] For the PCB board with the sub-outer layer circuit completed, perform optical automatic scanning and repair and determine the defects.

[0104] 26. Lamination

[0105] For the PCB board with the sub-outer layer circuit completed, perform browning treatment. Browning solution concentration: Micro-etching rate:

[0106] After the brown oxidation of the PCB board is completed, stack and press it according to the stack structure design to complete the outer layer pressing; PP model 1080 - 70%, thickness: 2.94 mil; copper foil model: HVLP - 0.33 OZ; pressing process: M8 (the pressing process parameters are as shown in Table 2 below)

[0107] Table 2: Pressing process parameters

[0108]

[0109] 27. Brown oxidation copper reduction

[0110] Perform brown oxidation copper reduction on the PCB board after the outer layer pressing is completed. Use the brown oxidation chemical solution to reduce the thickness of the copper foil and process the bright copper foil into brownish - red to facilitate the uniform absorption of laser energy during laser processing to form a blind hole pattern with a true roundness > 80%.

[0111] 27. Laser ablation of the target: Adopt the laser ablation method to expose the preset target patterns of L2 / L9, preparing for the target positioning and recognition for laser drilling of blind holes in layers L1 - L2 and L10 - L9.

[0112] 28. Laser drilling 3: Perform laser processing on the PCB board after pressing and brown oxidation treatment. The diameter of the blind hole is 0.1 mm; the CCD grabs the target points of the laser ablation of the target, and produces and processes the blind holes in layers L2 - L3 and L9 - L8.

[0113] 29. Drilling

[0114] Use mechanical drilling to process the through - holes of layers L1 - L10. Adopt the covering aluminum sheet + coated drill bit, high - speed M8 material parameters, and the spindle speed is 20Kr.

[0115] 30. High - speed cutting and grinding

[0116] Use a non - woven brush roller to remove the surface brown oxidation film and ensure that the copper surface is clean without foreign objects.

[0117] 31. Plasma degumming 2

[0118] Adopt the plasma process to perform plasma cleaning on the drilled board [first - order blind holes, through - holes], removing the resin gum residue on the inner wall of the holes to prepare for the next process of PTH electroless copper plating. (The parameters are the same as those in Step 16 [Plasma degumming 1])

[0119] 32. Horizontal PTH

[0120] Use a horizontal electroless copper plating line to deposit a thin layer of copper on the inner wall of [first - order blind holes, through - holes].

[0121] 33. Electroplating filling

[0122] For the outer-layer PCB boards that have completed electroless copper plating, use the gantry electroplating filling process to fill the first-order blind vias and electroplate a layer of copper with a thickness of 0.7 mil on the inner wall of the through vias.

[0123] 34. Vacuum plugging

[0124] Use a vacuum negative pressure plugging machine, set up an aluminum mesh plate, and after alignment, perform resin plugging on the outer-layer machine-drilled through vias.

[0125] 35. High-speed cutting and grinding

[0126] For the surface resin after the outer-layer through vias are filled and dried and cured after electroplating, use a ceramic brush roll + non-woven brush roll to grind and level it, remove the excess resin residue on the surface, and ensure that the hole opening is flat without protrusions.

[0127] 36. PTH / VCP

[0128] On the resin at the hole opening of the outer-layer through vias, chemically deposit a layer of copper, and use the VCP pulse electroplating process to thicken the copper thickness of the covered hole to 0.5 mil, and control the surface copper to 1.27 - 1.47 mil.

[0129] 37. High-speed cutting and grinding

[0130] Grind and polish the PCB board after the covering electroplating is completed to eliminate the brush marks on the board surface and ensure that the copper surface is clean and flat. Prepare the copper surface cleaning for the subsequent gold finger pattern processing and electroplating gold process.

[0131] 38. Dry film

[0132] Cover the copper-plated PCB board with the anti-etching photosensitive film of LDI8338, transfer the outer-layer circuit pattern to the photosensitive film using the laser direct imaging technology, and remove the unexposed part by sodium carbonate development, retaining the circuit pattern of the photosensitive anti-etching film.

[0133] 39. Positive etching

[0134] For the PCB board that has completed the image transfer, perform acidic etching to etch away the exposed copper, retain the circuit pattern, and use sodium hydroxide to remove the photosensitive dry film layer.

[0135] 40. Middle inspection AOI

[0136] Perform optical automatic inspection on the PCB board that has completed the circuit etching and repair the repairable defects.

[0137] 41. Resistance test

[0138] For the PCB board that has completed the etching, use a special four-wire fixture for detection, test the coupon in series, ensure the connection performance of various holes and graphic circuit layers, and there is no functional quality risk.

[0139] Schematic diagram of the [resistance test series conduction coupon] can be seen in the attachment Figure 1 ;

[0140] Description of the design scheme of the series test coupon:

[0141] (1) Monitor the alignment accuracy of 2nd-order blind vias, the alignment of machine-drilled through-layer blind vias and laser 6mil stepped blind vias, the plugging of first-order blind via alignment with tree plugs, and the blind via covering of first-order blind via alignment.

[0142] (2) Monitor the ICD and functional risks in processes such as laser, plasma desmearing, PTH copper plating, electroplated copper, and copper plating thickness of via covering.

[0143] (3) Facilitate the quality inspection of all hole types such as blind vias, blind via alignments, through-layer blind vias, buried vias, and through vias by a group of slices simultaneously.

[0144] 42. Solder mask pumice

[0145] Adopt sandblasting process to clean the oxide and foreign matters on the board surface and prepare for the subsequent gold plating dry film process.

[0146] 43. Gold plating dry film

[0147] 44. Print LPI1

[0148] 45. Gold plating fingers

[0149] 46. Gold plating dry film 2

[0150] 47. Print LPI2

[0151] 48. Vacuum etching

[0152] 49. Film stripping

[0153] 50. Baking (150°C * 1H)

[0154] 51. Positive wet film

[0155] 52. Selective chemical dry film

[0156] 53. Solder mask baking

[0157] 54. Immersion gold

[0158] 55. Selective chemical film stripping

[0159] 56. Lettering

[0160] 57. Press board warping

[0161] 58. Laser target

[0162] 59. Molding 1

[0163] 60、V-CUT

[0164] 61、Blind fishing

[0165] 62、Forming

[0166] 63、Bevel edge

[0167] 64、Testing

[0168] 65、Measuring impedance

[0169] 66、Final inspection

[0170] In this embodiment, a high-precision alignment process of laser burning the target is adopted. Among them, the laser burning target modules are reserved in the L3 layer and the L7 layer;

[0171] After the first pressing, the first-order blind hole is processed by laser burning the target for alignment;

[0172] The L2-L4 layer is processed by cross-layer machine drilling of controlled-depth blind holes and CCD target grabbing for single-layer processing;

[0173] The L9-L7 layer is processed by cross-layer machine drilling of controlled-depth blind holes and CCD target grabbing for single-layer processing;

[0174] The L2-L9 layer is processed by through buried holes for CCD target grabbing and blind hole positioning holes;

[0175] The sub-outer layer is processed by CCD target grabbing and LDI;

[0176] For the second pressing of the second-order blind hole, the L1-L2 layer is laser burned through the L1-L2 layer, and the target point of the L3 layer is burned out for target grabbing and positioning processing;

[0177] For the second pressing of the second-order blind hole, the L10-L9 layer is laser burned through the L10-L9 layer, and the target point of the L8 layer is burned out for target grabbing and positioning processing;

[0178] For the through hole, the X-RAY target hole is positioned by CCD target grabbing to drill the positioning hole, and the through hole is positioned and processed;

[0179] The outer layer is processed by LDI CCD target grabbing and positioning;

[0180] The solder mask is processed by LDI with free expansion and contraction and partition alignment;

[0181] Comprehensively monitor the blind holes and the series test coupon design of the machine-drilled cross-layer blind holes.

[0182] Example 2: 10L board three-order three-pressing process

[0183] Cutting / Panel Cutting → Inner Layer → Lamination & Punching → Inner Layer AOI → Lamination 1

L3-L8

L2-L9

Hole Diameter 4mil

Hole Diameter 6mil

L1-L10

[0184] Example 3: Five-Stage Four-Lamination Process for 10L Board

[0185] Cutting / Panel Cutting → Drilling Location Holes → Brown Oxidation and Copper Reduction → Laser Drilling → Plasma → Horizontal PTH → Electroplating for Filling → Inner Layer → Inner Layer AOI → Lamination 1

L4-L7

L3-L8

L2-L9

Hole Diameter 4mil

Hole Diameter 6mil

L1-L10

[0186] It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all fall within the protection scope of this application. Therefore, the protection scope of the patent of this application shall be subject to the appended claims.

Claims

1. A processing technology for an optical module circuit board, characterized in that: It includes the following steps: Blanking: Take a double-sided copper clad laminate, perform blanking, cutting, and inner layer circuit manufacturing processes on the double-sided copper clad laminate to obtain an inner layer board; First lamination: Thermally rivet and add layers to two or more inner layer boards to obtain a first multi-layer board; First multi-layer board processing: Perform brownification and copper reduction, laser burning of targets, laser drilling, mechanical drilling of blind holes, drilling of buried holes, plasma degumming, electroless copper plating, vacuum plugging, high-precision grinding, and circuit manufacturing processes on the first multi-layer board; Second lamination: Perform double-sided layer addition on the processed first multi-layer board to obtain a second multi-layer board, and perform brownification and copper reduction, laser burning of targets, laser drilling, mechanical drilling of blind holes, drilling of buried holes, plasma degumming, electroless copper plating, vacuum plugging, high-precision grinding, and circuit manufacturing processes on the second multi-layer board to obtain a semi-finished board. The second lamination process can be repeated as needed to obtain the required number of layers; Post-processing: Perform gold finger plating, LPI printing, vacuum etching, baking, immersion gold plating, text printing, testing, and packaging processes on the semi-finished board to obtain a finished board; Among them, in the mechanical drilling of blind holes process, a cross-layer depth-controlled mechanical drill is used to drill blind holes, the downward drilling depth is set at 6.5 ± 1 mil, the depth of the blind hole is 6.5 ± 1 mil, and after drilling the blind hole, a laser is used to drill a through-hole with a depth of 6 ± 1 mil; Target holes are formed on the outer layer, the second outer layer, and the third outer layer through laser burning of targets, that is, the alignment system uses target burning for alignment.

2. The processing technology of the optical module circuit board according to claim 1, characterized in that: When the second lamination process needs to be performed three or more times, the blanking process includes: Take a double-sided copper clad laminate, perform blanking, cutting, drilling of positioning holes, brownification and copper reduction, laser drilling, plasma treatment, horizontal electroless copper plating, electroplating for filling, and inner layer circuit manufacturing processes on the double-sided copper clad laminate to obtain an inner layer board.

3. The processing technology of the optical module circuit board according to claim 1, characterized in that: The conditions of the blanking process include: baking temperature 190°C ± 10°C, baking time 3h ± 1h, lamination time 4h ± 1h, lamination pressure 500 psi ± 50 psi, heating rate 3 - 4°C / min.

4. The processing technology of the optical module circuit board according to claim 1, characterized in that: In the vacuum plugging process, a vacuum negative pressure plugging machine is used, an aluminum sheet mesh plate is installed, and after alignment, the mechanical drill blind holes are filled with resin to ensure that the holes are fully filled without bubbles.

5. The processing technology of the optical module circuit board according to claim 4, characterized in that: The manufacturing method of the aluminum sheet mesh plate includes the following steps: Drilling: Sandwich a copper-free substrate between the upper and lower sides of the aluminum sheet, and perform numerical control drilling according to the holes that need to be filled with resin. The thickness of the aluminum sheet is 0.2 mm ± 0.05 mm; the thickness of the copper-free substrate is 0.1 mm ± 0.02 mm, and the size is 600 mm * 675 mm; Aluminum sheet cleaning: Use 2000-mesh sandpaper to polish both sides of the effective hole-filling area inside the board until it is flat without burrs, and use 200-mesh coarse sandpaper to polish the 50-mm-wide area outside the non-hole-filling area until it is rough; Attaching the drilled aluminum sheet to the mesh plate: Attach the drilled aluminum sheet to the mesh plate according to the size of the aluminum sheet; Brushing glue: Brush Nanbao resin glue on an 80-mm-wide area of the mesh plate-aluminum sheet attachment area, and let it stand for 2H to cure the resin; Cutting the mesh: Cut off the wire mesh in the hole-filling area, and attach aluminum foil tape to the area where the wire mesh contacts the aluminum sheet to prevent the wire mesh and glue residue foreign objects from being exposed.

6. The processing technology of the optical module circuit board according to claim 1, characterized in that: The conditions for the plasma degumming are as follows: treatment time is 30 - 40 min, vacuum degree is 200 ± 20 mtorr, power is 4 - 10 KW, and temperature is 75 ± 5 °C.

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