WO2021164203A1 - Preparation method for high-precision communication optical module printed circuit board - Google Patents

Abstract

The present invention provides a preparation method for a high-precision communication optical module printed circuit board. Specifically, in an existing circuit board preparation process, a press fitting control method, an electroplating control method, a surface copper thickness control method, a circuit control method, an outer layer size control method, and a connecting finger appearance control method are configured to control the preparation process. The quality and qualification rate of products are strictly controlled in each link of the preparation process in combination with the above methods; thus, the metal surface appearance yield is improved, and disqualification caused by penetration into metal, etc. is reduced.

Description

Method for preparing high-precision communication optical module printed circuit board Technical field

The invention relates to the technical field of circuit board manufacturing, in particular to a method for preparing a high-precision communication optical module printed circuit board.

Background technique

With the gradual increase in download rate requirements, wireless communication increasingly relies on optical fiber communication. In the current wireless communication network, except for the "last mile" which is a "wireless" form, the communication links behind the antenna are all optical fiber networks. In the 5G era, intergenerational upgrades will not only bring about a substantial increase in download speeds. The low latency and large-scale machine communication features that are not available in the 4G era will give birth to new technologies such as unmanned driving and interconnection of all things. Applications.

Therefore, 5G wireless communication will change life far more than 3G and 4G. The inherent advantages of large-capacity and long-distance optical fiber communications have perfectly met the requirements of 5G for bearer networks. In the pre-5G era, the terminal driving force for the rapid development of optical fiber communication technology and industry was the use of wired access for homes and enterprises. Comprehensive coverage and performance upgrades of the area network and backbone network. In the 5G era, mobile phones, automobiles, home appliances, industrial equipment, etc., which are connected in a wireless manner, are used as new terminals, which will jointly promote the technological progress and industrial development of optical fiber communication with terminals connected to the fixed network.

The deployment of 4G has brought a new market segment to the optical module industry. The demand for 5G will inject new impetus into the wireless optical module market and further increase the space of this market segment. The features such as increased site density and time synchronization accuracy of 5G networks have put forward new requirements on the functions and performance of optical modules.

The 5G high-precision communication optical module printed circuit board is an important part of the wireless optical film block. Its golden finger reliability, thickness tolerance uniformity, precise impedance control, and dimensional tolerance control are the key technical problems to be overcome. The proposal puts forward "a method for preparing printed circuit boards for high-precision communication optical modules" mainly to solve the above-mentioned problems, reduce the production cost of printed circuit boards for communication optical modules, and improve the quality of printed circuit boards for optical modules to meet increasing demands. Improve the reliability and precision requirements of printed circuit boards for optical modules.

Summary of the invention

In order to solve the above technical problems, the present invention provides a method for preparing a printed circuit board of a high-precision communication optical module. Specifically, a pressing control method, an electroplating control method, and a surface are provided in the existing circuit board preparation process. Copper control method, circuit control method, outer layer size control method, and gold finger appearance control method, combined with the above methods, strictly control the quality and pass rate of the product in each link of the preparation process, improve the appearance yield of the gold surface, and reduce Infiltrate gold and other scraps. Specifically:

A method for preparing a printed circuit board for a high-precision communication optical module includes the following steps: cutting the PCB substrate in sequence, processing the inner layer board, and performing the copper plating process after the inner layer AOI, pressing and drilling, and is characterized in ,Also includes

Pre-treatment before pressing: clean the secondary outer layer, perform browning treatment, judge whether the exposed surface of the plate after browning exceeds the threshold, if it is, clean it again, otherwise proceed to the pressing process;

Pressing process: select and align the plate and PP base material, perform pressing, check whether the pressing tolerance is consistent with the expansion and shrinkage value, if they are consistent, enter the subsequent process of pressing; otherwise, rework;

Follow-up process of pressing: drilling the circuit board obtained after pressing, and then baking the plate before electroplating and polishing the electroplated conductive plate, after electroplating, the film is removed, the circuit board is etched, and then the solder mask is then used to mill the plate twice. , Complete the external dimension processing of the circuit board.

Among them, the inner and outer layers of the PCB are composed of wires, holes and PAD. During the PCB production process, the inner layer is produced first, including: first pressing a photosensitive dry film on the substrate, and then covering the negative film on the dry film. Then the exposure is performed, where the color of the illuminated area is darker than the color of the non-illuminated area. After exposure, develop, optionally, use an acid solution to harden the dry film.

Among them, the browning treatment is to roughen the copper surface, increase the contact surface with the resin, increase the wettability of the copper surface to the flowing resin, passivate the copper surface, and avoid adverse reactions. Preferably, the browning solution is used. Treatment, the substrate is tightly combined with PP, which is the same as the pretreatment of the inner layer, that is, the copper on the inner layer is oxidized with a strong oxidant to make the surface rough. Because the color of copper oxide is black, the browning treatment is also called blackening Optionally, the browning liquid is an acidic medium, such as H ₂ SO ₄ browning liquid.

The electroplated conductive plate is preferably made of pure copper, or stainless steel, or an alloy material. The electroplated conductive plate is completely disassembled and assembled after polishing is completed. Preferably, the electroplated conductive plate is polished by a rust removing, grinding and polishing machine to ensure that the oxide layer of the electroplated conductive plate is not destroyed.

Compared with the prior art, the present invention has the following advantages:

The present invention performs surface cleaning of the secondary outer printed circuit board and browning treatment before the pressing, and further includes: adopting three-stage overflow water washing and ultrasonic water washing to integrally clean the surface of the secondary outer printed circuit board Clean up the debris residues, clean the front and back of the surface with a dusting wheel, put it into the browning line to complete the browning, check whether there is an unbrowning surface on the surface, when the exposed surface of the browning exceeds 5 single sides, renew Carry out overflow water washing, ultrasonic water washing, dust sticking wheel cleaning, and clean the board surface again until it is qualified.

When entering the pressing stage, use a new steel plate or a newly polished steel plate, check that there is no residual resin and copper scraps on the surface, and then use the principle of "same core synchronization" to select the plate and PP to make the pressing tolerance and expansion and contraction of the plate surface To unanimous. Inspecting the surface also includes: checking whether there is any residual resin or copper scraps on the surface. If not, perform pressing treatment to make the pressing tolerance of the board surface consistent with the expansion and contraction; otherwise, return to the cleaning process.

The electroplating control method provided in the present invention is specifically: baking the plate before electroplating, the parameters of the baking plate: 150℃*2H, because in the existing production process, the material will seep when it is pickled and rusted or electroplated. Into the atomic hydrogen, which in turn causes the metal’s crystal lattice to be twisted out, resulting in a large internal stress, which reduces the toughness of the metal coating and the substrate, and the metal material becomes brittle, and its performance cannot meet the production requirements. Therefore, the present invention first Carry out baking sheet to eliminate hydrogen embrittlement. In order to further improve the performance of metal materials, the preferred baking sheet parameter is to heat at a temperature of 150 ℃ for 2 hours. If the temperature is too high or the time is too long, it is easy to cause annealing of the metal workpiece and reduce The hardness and mechanical strength of the workpiece. If the temperature is too low or the time is insufficient, the elimination of hydrogen is incomplete, and it is difficult to ensure that the hydrogen in the metal material is completely removed.

Further, sand blasting is performed, and the setting parameters are: speed 1.0m-1.5m/min, sand blasting twice (sand blasting pressure is 1.5kg/cm²), the direction is uniformly horizontal, and the direction is strictly prohibited from being inconsistent. It is made of horizontal copper sinking, bulking→deadhesive→neutralizing→sinking copper, at a speed of 2.5m/min, and the direction of the board surface is consistent. When filling holes and electroplating, make the first piece, check the appearance of the board surface, prevent the floating frame from scratching, and check the overall jet flow. The jet flow on both sides of the VCP is consistent. Using 8ASF*90min production, VCP copper cylinder current coefficient ratio is: 0.6/0.6/0.8/0.8/1.0/1.0/1.1/1.1/1.2/1.2, copper sulfate 220-260g/L, sulfuric acid accounts for 5-7%, using Soluble anode. Polishing agent range: 0.5-1.0ml/L, leveling agent range: 8-16ml/L, approximately 1:16, the filling protection current is maintained at more than 50%, and someone will follow up the filling line, and immediately investigate if an abnormality occurs . After the hole filling is completed, the board surface is fully measured for copper. The overall surface copper is distributed within 20-30μm. When the surface copper is greater than this range, it is strictly forbidden to use the grinding method to reduce copper.

Because the board surface line width and line spacing are usually 2.5/2.5mil, it belongs to the domestic leading position. The line width and line spacing have extremely high requirements for copper tolerances, especially for the entire electroplated line surface copper is extremely poor. The copper difference of the whole line and surface mainly includes two aspects: one is the difference of the surface copper between the whole line board and the board, and the other is the surface copper difference of different parts of the board, in order to ensure the surface copper difference of the entire board. The value is within the range, so this surface copper control method is adopted.

The present invention provides a method for controlling surface copper, wherein the complete disassembly of the electroplated conductive plate, and the assembly after polishing is completed, specifically includes: before electroplating, all the electroplated conductive plates are disassembled, including the electroplated conductive plate arms and other metal components, and then proceed Polishing, the passivation layer on the surface of the connection position of the metal part is polished clean and the bright metal surface is leaked out, and then assembled together to ensure good conductivity between the parts of the electroplated conductive plate. The copper block connected between the electroplated conductive plate and the conductive rail is polished clean, and the conductive adhesive is removed from the conductive rail and a layer is reapplied, so that the median copper value between the plates can be kept consistent. The control surface copper in the board adopts the method of integrally correcting the electroplated conductive plate arms. Put the two electroplated conductive plate arms together, and the two electroplated conductive plate arms are parallel to the VCP conductive rails, so that the entire board surface can be guaranteed to be conductive. The rails are kept parallel. When the board surface is inside the copper cylinder, it can be ensured that the distance between any part of the board surface and the titanium basket is the same, so that the uniformity of copper on the front and back of the board can be ensured.

Further, in order to ensure that there will be no abnormalities such as infiltration and plating in the electro-gold process, the present invention uses a line control method to control, specifically the following methods are used to control: 1. The pre-treatment of the line adopts a sandblasting method; 2. The film is removed twice, Prevent the dry film from remaining and form a short circuit of corrosion phenomenon; 3. After the circuit is exposed and developed, the board surface should be stored in a room with a temperature of 22±2°C and a humidity of ≤40%, and the charging time should be controlled within 4H.

As another preferred embodiment, the present invention preferably uses CNC equipment for production, selects a new milling cutter, designs two sets of CNC data for two milling, first produces the set periphery, and then repositions it to reduce the position of the PCB during the continuous molding process. After the first step is completed, precise positioning and milling of the inner groove in the unit of set are used to reduce the dimensional error of the optical module product.

Furthermore, since the gold-plated finger is completed before the solder mask, compared with the original gold finger production process, there are more lines, solder mask and other pre-processes. In order to reduce the scratches on the gold finger during the production process, two plates are prohibited after the gold-plating is completed. Stacked together, select the space-insertion board cart and the cleaned film transport to control the scratches of the gold fingers. The control points are as follows: dry film, electroplating, and etching are transported by the board cart to prevent product friction and scratches; solder mask control For one-time yield, it is forbidden to re-wash heavy industry; after etching to before forming, each board is separated and transported with cleaned film; AOI machine, solder mask printing machine, exposure machine, and inspection table are cleaned before production; When electric milling, the surface is covered with a backing plate to prevent the golden fingers from being damaged by the brush of the main shaft of the forming machine; the speed of the finished product cleaning machine is appropriately slowed down, so that the puller can regulate the plate connection action and avoid scratching the golden fingers.

The invention provides a method for manufacturing a high-precision optical module printed circuit board, which is provided with a pressing control method, an electroplating control method, a surface copper control method, a circuit control method, an outer layer size control method, and a gold finger appearance control method , Combined with the existing problems in the process of preparing high-precision communication optical module printed circuit boards, timely and accurate management and control are carried out to ensure the quality and specifications of the preparation and production. The high-precision optical module printed circuit board of the present invention is manufactured Method to improve the appearance yield of the gold surface and reduce the scraps such as gold infiltration. In industrial production, it has produced huge benefits, greatly reducing the rework time and labor costs caused by quality problems such as scrapping, and greatly improving the yield and production efficiency of circuit boards.

Detailed ways

The core of the present invention is to provide a high-precision communication optical module printed circuit board preparation method, in view of the existing problems in the preparation of circuit boards, from the perspective of quality control, from the source of production, multiple control technical means are set up, Including the pressing control method, the electroplating control method, the surface copper control method, the line control method, the outer layer size control method and the golden finger appearance control method, etc., to realize the timely control and management of the preparation process, and ensure the whole life cycle of the preparation The high quality solves the problems of excessive error caused by various factors in the prior art, friction and scratches caused during the preparation process, and multiple rework problems.

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only These are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

The present invention will be further described in detail below in conjunction with specific embodiments.

Because the golden finger appearance and reliability of the high-precision communication optical module printed circuit board are the key control points for making this type of printed circuit board. Among them, PCB board edge plugs ("Golden Fingers", Connecting Finger) are used as outlets to connect with other devices (such as motherboards, chassis, etc.). The so-called board edge plugs refer to a row of PADs with a certain distance, which are processed by electroplating nickel and gold. The surface is formed and used for board card connection. All signals are connected and transmitted through "golden fingers". Because the surface is gold-plated and the PAD is arranged in a finger-like shape, it is also called "golden finger".

The production process of PCB board with side plugs includes: inner layer processing → inner layer AOI → pressing → drilling → copper sinking → board electricity → outer layer graphics → pattern plating → outer layer etching (alkaline etching) → outer layer AOI→screen printing solder mask (normally produced surface solder mask)→characters→immersion gold→sticking blue glue→blue glue opening window→electroplating nickel→forming→beveling→test→FQC. The ordinary "gold finger" electric gold lead is designed at the front of the "gold finger", and the lead is completely removed by forming and beveling.

Inner layer processing: select the substrate, preferably the copper-clad substrate, and cut the raw materials, that is, cut the raw materials according to the required size, and then remove the moisture through the baking plate to stabilize the size of the board. Among them, chemical cleaning is performed before the inner layer Or mechanical template treatment to remove oil and other organic dirt on the copper surface. The mechanical template is to roughen the copper surface, increase the contact area between the dry film and the copper surface, and increase adhesion. Then, the inner layer pattern transfer is performed, that is, the circuit image on the film is transferred to the base copper foil to form a corrosion-resistant or electroplating-resistant coating film image. After the image is transferred, the inner layer is etched, and the unetched part is removed during the leg film.

Inner layer AOI: Automated Optical Inspection uses the different reflective effects of the copper surface of the PCB board and the substrate, and compares the image of the PCB board with the standard board through optical scanning. The substrate is preferably epoxy resin. The base material, among which the standard board can be selected as CAM material, so as to detect the shortcomings in the PCB circuit pattern. The technical effect of the inner layer AOI is to detect defective PCBs, improve the quality of the PCB circuit, reduce scrap, thereby improving the manufacturing process and increasing the yield.

Further, the inner layer AOI is mechanically drilled and punched by using a punching machine. It also includes the use of a scanner to optically scan the image of the PCB board, so that the inspection machine is used to detect defects in the PCB board circuit diagram. When it is found that the image of the PCB board is inconsistent with the standard board, the line gap repair is carried out through the line patching machine, thereby completing the overall process of memory AOI.

Copper Immersion: Eletcroless Plating Copper is usually also called Copper Immersion or Potting (PTH), which is a self-catalyzed redox reaction, that is, PTH (plated through hole) is performed after the drilling of the double-sided board is completed. ). Specifically include: pretreatment, preferably using metal palladium particles as an activator to make the surface of the substrate absorb a layer of active particles, so that the copper ions of the substrate are reduced, and the reduced metal copper nucleus itself serves as a catalytic layer of copper ions. The reduction reaction of copper continues on the surface of these new copper nuclei. The purpose of copper sinking is to metalize the resin and glass bundles of the non-conductor part on the hole wall for subsequent copper electroplating process. The copper sinking process is preferably: boarding, leavening, degumming after washing, neutralizing after washing, washing and degreasing, washing and microetching, then pickling, washing, presoaking, activation, washing and sinking Copper, the final lower board.

Board electricity: The main processes include: upper board, degreasing, water washing, acid immersion, copper plating and water washing of the lower board. The purpose of board electricity is to thicken the copper-plated layer in the hole to make good conduction.

The process of the outer layer graphics is preferably: first pretreatment, that is, grinding and brushing treatment, and pressing the film after drying, that is, pressing the PCB and the dry film with a hot pressing roller to obtain a uniform layer of resist on the PCB surface. Then exposure is carried out, and the photosensitivity of the dry film is used to make the dry film from a monomer to a polymer through two catalytic factors of light and heat. Finally, after developing and electrographic processing, the film is removed and etched to complete the outer layer pattern production.

Outer layer etching: In the PCB processing process, a lead-tin anti-corrosion layer is pre-plated on the part of the copper foil that needs to be retained on the outer layer of the board, and then the remaining copper foil is etched away by chemical treatment, that is, etching. Among them, the outer layer etching means that only the outer layer of copper is etched.

The outer layer AOI is similar to the inner layer AOI and is tested to ensure the pass rate and quality of the PCB board.

Characters: that is, a specific code or logo is printed for each PCB board, preferably a printing machine or inkjet machine is used for character processing. So as to ensure the identification and processing of each printed PCB board.

Immersion gold: It is a process of applying solderable coating on the surface of bare copper of PCB. Specifically, it includes whole hole, degreasing and washing with water followed by micro-etching and activation, and finally performing nickel, gold and drying to complete the gold-immersion process.

Bevel: The golden finger part of the circuit board is chamfered to obtain a double bevel that meets the size of the blueprint. Preferably, the useless area is cut by the cutting tool at an inclination angle, so that the tip of the golden finger forms a double bevel, so as to facilitate the assembly operation of the next process.

In order to improve the quality of the manufacturing process, it is necessary to set up multiple management and control methods to ensure the pass rate of circuit board preparation. The present invention improves a high-precision communication optical module printed circuit board preparation method. The scope of the pressing control method is set as a control method of the pressing process, which specifically includes:

Pre-treatment before pressing: clean the secondary outer layer, perform browning treatment, judge whether the exposed surface of the plate after browning exceeds the threshold, if it is, clean it again, otherwise proceed to the pressing process;

The cleaning of the secondary outer layer and browning treatment further includes:

Before browning the secondary outer layer, use 3 stages of overflow water washing, length: 1m; 3 stages of ultrasonic washing, length: 1m, speed 3m/min, and clean the debris residues on the surface of the secondary outer printed circuit board as a whole. Then clean the front and back of the surface with a dusting wheel, and then put it into the browning line. After browning, visually check whether there is an unbrowning surface on the surface. When the exposed surface of the browning is more than 5 single sides, perform overflow water washing and ultrasonic Wash with water, clean the dust sticking wheel, and clean the board again until it is qualified.

In the pressing process, use a new steel plate or a newly polished steel plate, check that there is no residual resin and copper scraps on the surface, and then align the plate and PP and press them to make the plate surface pressing tolerance and expansion and contraction consistent.

The subsequent process of pressing: drilling the circuit board obtained after pressing, and then baking the plate before electroplating and polishing the electroplated conductive plate, and then the film is removed after electroplating.

The circuit board is etched and then soldered, and the board is milled twice with a milling cutter to complete the external dimension processing of the circuit board.

Optionally, the present invention also designs an electroplating control method to effectively reduce the rework rate, which specifically includes:

For the process before electroplating, the baking plate process is optional. The parameters of the baking plate are set to a temperature of 150°C, and the baking plate time is 2 hours. Preferably, the treatment is made by sandblasting, and the production speed is preferably 1.0m- 1.5m/min, sand blasting is carried out twice, among which, the blasting pressure is 1.5kg/cm², and the direction is horizontal or vertical. It is strictly forbidden to have inconsistent directions, otherwise it will cause scratches.

Optionally, it is made of horizontal copper sinking. The process is: bulking→gluing→neutralization→copper sinking. The production parameters are set to a speed of 2.5m/min to strictly ensure that the board surface direction is consistent.

Furthermore, during hole filling and electroplating, the first piece should be made, the appearance of the board surface should be checked to prevent the floating frame from scratching, and the overall jet flow should be inspected. The jet flow on both sides of the VCP is consistent. Using 8ASF*90min production, VCP copper cylinder current coefficient ratio is: 0.6/0.6/0.8/0.8/1.0/1.0/1.1/1.1/1.2/1.2, preferably, other production parameters are: copper sulfate 220-260g/L, Sulfuric acid accounts for 5-7%, using soluble anodes. Among them, the range of light agent: 0.5-1.0ml/L, the range of leveling agent: 8-16ml/L, approximately 1:16, the filling protection current is maintained at more than 50%, and someone will follow up the filling line. Once an abnormality occurs Investigate immediately and control the problem at the source in time to avoid greater losses.

Further, after the hole filling is completed, the board surface is fully measured for copper, and the overall surface copper is distributed within 20-30 μm. When the surface copper is greater than this range, it is strictly forbidden to use the grinding method to reduce copper.

Because the board surface line width and line spacing are usually 2.5/2.5mil, it belongs to the domestic leading position. The line width and line spacing have extremely high requirements for copper tolerances, especially for the entire electroplated line surface copper is extremely poor. The copper difference of the whole line and surface mainly includes two aspects: one is the difference of the surface copper between the whole line board and the board, and the other is the surface copper difference of different parts of the board, in order to ensure the surface copper difference of the entire board. If the value is within the range, the present invention sets the use of this surface copper control method.

The control method of surface copper is mainly to ensure the consistency of the distance between any part of the board surface and the titanium basket, thereby ensuring the uniformity of surface copper on the front and back of the board surface. The specific control methods used include: dismantling all electroplated conductive plates before electroplating, including Electroplating the conductive plate arm and other metal components, and then polishing, the passivation layer on the surface of the connection position of the metal component is polished to clean and leaking the bright metal surface, and then assembled together to ensure good conductivity between the components of the electroplating conductive plate. The copper block connected between the electroplated conductive plate and the conductive rail is polished clean, and the conductive adhesive is removed from the conductive rail and a layer is reapplied, so that the median copper value between the plates can be kept consistent. The control surface copper in the board adopts the method of integrally correcting the electroplated conductive plate arms. Put the two electroplated conductive plate arms together, and the two electroplated conductive plate arms are parallel to the VCP conductive rails, so that the entire board surface can be guaranteed to be conductive. The rails are kept parallel. When the board surface is inside the copper cylinder, it can be ensured that the distance between any part of the board surface and the titanium basket is the same, so that the uniformity of copper on the front and back of the board can be ensured.

Further, in order to ensure that there will be no abnormalities such as infiltration and plating in the electro-gold process, the present invention adopts a line control method, specifically: 1. The pre-treatment of the line adopts a sandblasting method; 2. The film is removed twice to prevent dry film residue , Forming a short circuit of corrosion phenomenon; 3. After the circuit is exposed and developed, the board surface should be stored in a room with a temperature of 22±2°C and a humidity of ≤40%, and the charging time should be controlled within 4H.

Because the dimensional accuracy of module PCB products requires ±0.1mm, the dimensional requirements of conventional PCB products are generally ±0.13mm, ±0.15mm.

In order to meet this strict requirement, as another preferred embodiment of the present invention, the present invention adopts strict molding tolerance control technology, selects CNC equipment with higher precision, selects brand-new milling cutters, and designs two sets of CNC data for two milling plates. First make the set periphery, and then reposition it to reduce the deviation of the PCB board position during the continuous molding process. After the first step is completed, the inner groove is accurately positioned and milled in the unit of the set to make the size of the optical module product meet the requirements.

Further, considering that the gold-plated fingers are completed before the solder mask, compared with the original gold finger production process, there are more lines, solder mask and other pre-processes. In order to reduce the scratches on the gold fingers during the production process, two pieces are prohibited after the gold plating is completed. The boards are stacked together, and the spaced board cart and the cleaned film are used to control the scratches of the golden fingers. The control points are as follows: dry film, electroplating, and etching are handled by the board cart to prevent product friction and scratches; solder mask Control the yield rate at one time, and it is forbidden to back and wash heavy industry; after etching to before forming, each plate is separated and transported with cleaned film; AOI machine, solder mask printing machine, exposure machine, and inspection table are cleaned before production ; When electric milling, the surface is covered with a backing plate to prevent the golden fingers from being damaged by the brush of the main shaft of the forming machine; the speed of the finished product cleaning machine is appropriately slowed down so that the puller can standardize the plate connection action and avoid scratching the golden fingers.

In summary, this solution is a high-precision optical module printed circuit board manufacturing method, combined with the specific PCB board production process with edge plugs, respectively in the pressing process, the electroplating process, the electroplating conductive plate polishing treatment before electroplating, and the circuit Corresponding control methods are set up in terms of control and gold finger appearance to ensure the high-precision requirements of the optical module printed circuit board, improve the appearance yield of the gold surface, and reduce the scrap such as gold infiltration.

Although the description of the present invention is made in conjunction with the above specific embodiments, it is obvious that those skilled in the art can make many substitutions, modifications and changes based on the above content. Therefore, all such substitutions, improvements and changes are included in the spirit and scope of the appended claims.

Claims (9)

1. A method for preparing a printed circuit board for a high-precision communication optical module includes the following steps: cutting the PCB substrate in sequence, processing the inner layer board, and performing the copper plating process after the inner layer AOI, pressing and drilling, and is characterized in ,Also includes

   Pre-treatment before pressing: clean the secondary outer layer, perform browning treatment, judge whether the exposed surface of the plate after browning exceeds the threshold, if it is, clean it again, otherwise proceed to the pressing process;

   Pressing process: select and align the plate and PP base material, perform pressing, check whether the pressing tolerance is consistent with the expansion and shrinkage value, if they are consistent, enter the subsequent process of pressing; otherwise, rework;

   Follow-up process of pressing: drilling the circuit board obtained after pressing, and then baking the plate before electroplating and polishing the electroplated conductive plate, after electroplating, the film is removed, the circuit board is etched, and then the solder mask is then used to mill the plate twice. , Complete the external dimension processing of the circuit board.
2. The method according to claim 1, wherein the cleaning the secondary outer layer and performing browning treatment further comprises:

   Three-stage overflow water washing and ultrasonic water washing are used to clean the debris residues on the surface of the sub-outer printed circuit board as a whole. Clean the front and back sides of the surface with a sticky wheel, and put it into the browning line to complete the browning, and then check Whether there is an unbrowning surface on the surface, when the browning exposed surface exceeds 5 single sides, perform overflow water washing, ultrasonic water washing, and dust stick cleaning again, and clean the board surface again until it is qualified.
3. The method according to claim 1, characterized in that, before the pressing process, it further comprises: checking whether there are residual resin or copper scraps on the surface, and if not, perform pressing treatment; otherwise, return to the pre-pressing process. Treatment process.
4. The method according to claim 1, characterized in that, before the electroplating, it also includes sandblasting, the sandblasting speed is set to 1.0m-1.5m/min, the sandblasting is performed twice, and the sandblasting direction is horizontal or vertical. .
5. The method according to claim 1, characterized in that, before the electroplating, it further comprises the steps of copper sinking, and steps of bulking, degumming, neutralizing and copper sinking are performed in sequence.
6. The method according to claim 1, characterized in that it further comprises: the electroplating includes, making a sample, checking whether the appearance of the sample plate surface is qualified, preventing the floating frame from scratching, and checking whether the VCP jets on both sides of the overall jet are consistent; if they are the same; Fill the hole, and then perform the surface copper control process.
7. The method according to claim 6, characterized in that the step of controlling the surface copper comprises: disassembling the electroplated conductive plate and polishing it until the passivation layer on the surface of the connection position of the metal part of the electroplated conductive plate is completely polished and the light is leaked out. Assemble and repaint the inside of the conductive rail, so that the electroplated conductive plate is parallel to the conductive rail as a whole.
8. The method according to any one of claims 1-7, characterized in that, according to the method, CNC equipment is used for production, a brand-new milling cutter is selected, two sets of CNC data are designed for two milling plates, and the set periphery is produced first, and then Repositioning reduces the deviation of the PCB board position during the continuous molding process. After the first step is completed, the internal groove is accurately positioned and milled in the unit of set to reduce the dimensional error of the optical module product.
9. The method according to claim 9, characterized in that it further comprises: the dry film, electroplating, and etching are transported by a plug-in cart to prevent product friction and scratches; after etching, each plate is separated by a cleaned film before forming. Handling; clean the AOI machine, solder mask printing machine, exposure machine, and inspection table before production; cover the surface with a backing plate during electric milling to prevent the molding machine's main shaft from brushing the golden fingers.