High-precision circuit board production process

Abstract

The present invention discloses a high-precision circuit board production process, including cutting, processing of FR-4 double-sided substrate, milling inner groove, processing of copper substrate, preparation before lamination, lamination and degumming, production of outer circuit, optical detection, solder mask, printing text, surface treatment, electrical measurement, inspection and warehousing, etc. The present invention uses the first positioning hole as the positioning reference hole in the whole production process to avoid cumulative processing errors and improve the position accuracy of the heat dissipation boss and the inner and outer graphic circuits; the stacked plates are superimposed and fixed by rivets to ensure that there is no displacement between the single plates during the lamination process, thereby improving the lamination accuracy; by etching an annular boss around the first positioning hole, the flowable colloid generated by the heat melting of the PP semi-cured plate during the lamination process overflows through the gap formed between the annular boss and the second positioning hole, preventing the colloid from overflowing into the first positioning hole, providing a positioning basis for the subsequent high-precision graphic transfer, and ensuring that the precision tolerance of the finished board is controlled within + / -0.06mm.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board processing, and in particular to a high-precision circuit board production process. Background Art

[0002] With the rapid development of science and technology and increasingly fierce competition, all walks of life have strengthened the improvement of production efficiency and product quality, the control of manufacturing costs and scientific and standardized management to enhance the competitiveness of enterprises. Interlayer alignment technology is a very common and important technology in the manufacturing process of multi-layer circuit boards. This technology has a very important impact on the stability of product quality, the effectiveness of processing efficiency and manufacturing costs.

[0003] At present, the production of high-heat dissipation and high-precision circuit boards requires that the tolerance range of the center point of the heat dissipation boss and the non-copper-plated mounting hole be controlled within + / -0.06mm, and the production of the inner and outer circuit layers of the circuit board and the lamination process must be precise and accurate to meet the high position accuracy requirements of high-precision electronic circuits and precision chip mounting. However, due to the superposition of tolerances between the various steps in the production process, the existing circuit board production process results in a tolerance range of only + / -0.15mm between the center point of the heat dissipation boss and the non-copper-plated mounting hole. During the precision chip mounting process, it is easy to have excessive position deviations. At the same time, for high-heat dissipation boards with added bosses, the position accuracy of the copper bosses is often low due to misalignment during lamination, so that the products cannot meet the strict quality requirements of customers' products. Summary of the invention

[0004] In order to overcome the above-mentioned defects, the present invention provides a high-precision circuit board production process.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a high-precision circuit board production process, comprising the following steps:

[0006] Step 1, cutting: Cut the required FR-4 double-sided substrate, PP prepreg substrate and copper substrate into specific sizes for subsequent processing;

[0007] Step 2, processing of the FR-4 double-sided substrate: after drilling a number of via holes on the FR-4 double-sided substrate, an inner layer graphic circuit is made on one side of the FR-4 double-sided substrate;

[0008] Step 3, processing of the copper substrate: the copper substrate is respectively provided with first positioning holes near its four end corners, and the first positioning holes are used as positioning references. The copper substrate is subjected to dry film pasting, exposure, development, and etching to form a heat dissipation boss and an annular boss concentric with the first positioning hole;

[0009] Step 4, processing of the FR-4 double-sided substrate and the PP prepreg: respectively forming an inner groove and a second positioning hole on the FR-4 double-sided substrate and the PP prepreg, wherein the outline dimension of the inner groove is slightly larger than the outer dimension of the heat dissipation boss, the second positioning hole is concentrically arranged with the annular boss, and the diameter of the second positioning hole is slightly larger than the diameter of the annular boss;

[0010] Step 5, preparation before lamination: after the FR-4 double-sided substrate and the copper substrate are browned, a plurality of corresponding riveting positioning holes are respectively opened on the FR-4 double-sided substrate, the PP semi-cured board and the copper substrate, and then the PP semi-cured board, the FR-4 double-sided substrate and the release film are sequentially stacked on the copper substrate to form a laminated board, and a plurality of rivets are respectively passed through the corresponding riveted positioning holes to stack and fix the laminated boards to form a preliminary laminated board;

[0011] Step 6, lamination and glue removal: placing the preliminary laminate on a press for lamination, during which the PP semi-cured board is heated and melted to produce a flowable colloid, which overflows upward through the gap formed between the heat dissipation boss and the inner groove, the gap formed between the annular boss and the second positioning hole, and the electric through hole, and after the colloid solidifies, the release film is torn off, and the overflowed glue is removed by a ceramic grinding plate;

[0012] Step 7, making an outer layer circuit: using the first positioning hole as a positioning reference, making an outer layer graphic circuit on the upper layer of the FR-4 double-sided substrate to complete the preliminary production of the circuit board;

[0013] Step 8, optical inspection: Use optical principles to compare data, inspect the circuit board, and carry out corresponding repairs or scrapping;

[0014] Step 9, solder mask: Cover the copper surface of the circuit board that does not need to be soldered with a layer of solder mask ink;

[0015] Step 10, printing text: using a printer to mark product related information on the circuit board;

[0016] Step 11, surface treatment: forming a surface treatment layer on the copper surface not covered by the solder mask ink by chemical nickel-palladium-gold process;

[0017] Step 12, molding: using the first positioning hole as a positioning reference, a high-precision punching machine is used to punch out non-electroplated through holes in the unit board, and then the unit board shape is punched out to obtain the finished board required by the customer;

[0018] Step 13, electrical testing: the circuit network of the finished board is tested for open circuit and short circuit by contacting the test points of the network with the test needle to remove the bad board;

[0019] Step 14, inspection and warehousing: Inspect the appearance of the finished board, and put it into storage if it is qualified, otherwise it will be scrapped.

[0020] As a further improvement of the present invention, in step 1, the sheet material is processed into a specific size through cutting - baking - planing - grinding.

[0021] As a further improvement of the present invention, the FR-4 double substrate is composed of an insulating board and copper foils arranged on both sides of the insulating board, and the inner layer graphic circuit and the outer layer graphic circuit are respectively arranged on the copper foils on both sides.

[0022] As a further improvement of the present invention, in step 2, the inner layer graphic circuit is formed by copper deposition-electroplating-dry film pasting-exposure-development-etching-removal of dry film and excess copper foil.

[0023] As a further improvement of the present invention, in step 7, the outer layer pattern circuit is formed by dry film lamination-exposure-development-pattern electroplating-etching.

[0024] As a further improvement of the present invention, in step 5, the release film is provided with two layers, and the thicknesses of the two layers of the release film are 0.03 mm and 0.12 mm respectively from bottom to top.

[0025] As a further improvement of the present invention, step 8 specifically includes: using automatic optical detection equipment to compare the circuit board with the 0K pattern to find the difference position; then using a repair machine to judge the difference position one by one, and repair or scrap it.

[0026] As a further improvement of the present invention, the step 9 specifically includes: solder resist pre-treatment - printing solder resist ink - pre-baking - CCD exposure machine exposure - development, wherein the thickness of the solder resist ink is 20-40 μm.

[0027] As a further improvement of the present invention, step 10 specifically includes: writing a printing program according to the product-related information that needs to be printed on the product - using a printer to call the printing program to print the product-related information on the circuit board - baking the printed ink to solidify it and adhere to the circuit board.

[0028] As a further improvement of the present invention, in step 11, the specific steps of the chemical nickel palladium gold process include: degreasing - micro-etching - pre-immersion - activation - nickel deposition - palladium deposition - gold deposition - drying.

[0029] The beneficial effects of the present invention are:

[0030] 1. The first positioning hole is used as the positioning reference hole throughout the production process to avoid cumulative processing errors and improve the position accuracy of the heat dissipation boss, inner and outer layer graphic circuits, and non-copper-plated mounting holes processed by the punch press;

[0031] 2. The stacked plates are fixed by rivets to ensure that there is no displacement between the single plates during the lamination process, thus improving the lamination accuracy;

[0032] 3. By etching an annular boss around the first positioning hole, the flowable colloid generated by the melting of the PP semi-cured board during the pressing process can overflow through the gap formed between the annular boss and the second positioning hole, preventing the colloid from overflowing into the first positioning hole, providing a positioning basis for subsequent high-precision pattern transfer, and ensuring that the precision tolerance of the finished board is controlled within + / -0.06mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the present invention;

[0034] Figure 2 It is a schematic diagram of the stacking state of the finished plate of the present invention;

[0035] Figure 3 It is a schematic diagram of the dimension marking of the heat dissipation boss and the non-electroplated through hole of the present invention.

[0036] Combined with the accompanying drawings, the following description is given:

[0037] 1. FR-4 double-sided substrate; 11. Via holes; 12. Insulating board; 13. Copper foil; 2. PP semi-cured board; 3. Copper substrate; 31. First positioning hole; 32. Heat dissipation boss; 33. Annular boss; 4. Release film; 5. Riveted positioning hole; 6. Rivet; 7. Surface treatment layer; 8. Non-electroplated through hole; A. Inner groove; B. Second positioning hole. DETAILED DESCRIPTION

[0038] A preferred embodiment of the present invention is described in detail below in conjunction with the accompanying drawings.

[0039] See also Figures 1 to 3 The present invention provides a high-precision circuit board production process, comprising the following steps:

[0040] Step 1, cutting: the FR-4 double-sided substrate 1, PP prepreg board 2 and copper substrate 3 required for production are made into specific sizes for subsequent processing;

[0041] Step 2, processing of the FR-4 double-sided substrate 1: after drilling a plurality of via holes 11 on the FR-4 double-sided substrate 1, an inner layer pattern circuit is made on one side of the FR-4 double-sided substrate 1;

[0042] Step 3, processing of the copper substrate 3: first positioning holes 31 are respectively opened near the four corners of the copper substrate 3, and the first positioning holes 31 are used as positioning references. A heat dissipation boss 32 and an annular boss 33 concentric with the first positioning hole 31 are formed on the copper substrate 3 by dry film pasting, exposure, development, and etching;

[0043] Step 4, processing of the FR-4 double-sided substrate 1 and the PP prepreg board 2: respectively punching out an inner groove A and a second positioning hole B on the FR-4 double-sided substrate 1 and the PP prepreg board 2, wherein the outline dimension of the inner groove A is slightly larger than the outer dimension of the heat dissipation boss 32, the second positioning hole B is concentrically arranged with the annular boss 33, and the diameter of the second positioning hole B is slightly larger than the diameter of the annular boss 33;

[0044] Step 5, preparation before lamination: browning the FR-4 double-sided substrate 1 and the copper substrate 3, opening a plurality of corresponding riveting positioning holes 5 on the FR-4 double-sided substrate 1, the PP semi-cured board 2 and the copper substrate 3, and then sequentially stacking the PP semi-cured board 2, the FR-4 double-sided substrate 1 and the release film 4 on the copper substrate 3 to form a laminated board, and stacking and fixing the laminated boards by passing a plurality of rivets 6 through the corresponding riveting positioning holes 5 to form a preliminary laminated board;

[0045] Step 6, lamination and glue removal: the preliminary laminate is placed on a press for lamination. During the lamination process, the PP semi-cured board 2 is heated and melted to produce a flowable colloid, which overflows upward through the gap formed between the heat dissipation boss 32 and the inner groove A, the gap formed between the annular boss 33 and the second positioning hole B, and the electric through hole 11. After the colloid solidifies, the release film 4 is torn off, and the overflowed glue is removed by a ceramic grinding plate;

[0046] Step 7, making the outer layer circuit: using the first positioning hole 31 as a positioning reference, making the outer layer graphic circuit on the upper layer of the FR-4 double-sided substrate 1, and completing the preliminary production of the circuit board;

[0047] Step 8, optical inspection: Use optical principles to compare data, inspect the circuit board, and carry out corresponding repairs or scrapping;

[0048] Step 9, solder mask: Cover the copper surface of the circuit board that does not need to be soldered with a layer of solder mask ink;

[0049] Step 10, printing text: using a printer to mark product related information on the circuit board;

[0050] Step 11, surface treatment: forming a surface treatment layer 7 on the copper surface not covered by the solder resist ink by chemical nickel-palladium-gold process;

[0051] Step 12, molding: using the first positioning hole 31 as a positioning reference, a high-precision punch is used to punch out the non-electroplated through hole 8 in the unit board, and then the unit board shape is punched out to obtain the finished board required by the customer;

[0052] Step 13, electrical testing: the circuit network of the finished board is tested for open circuit and short circuit by contacting the test points of the network with the test needle to remove the bad board;

[0053] Step 14, inspection and warehousing: Inspect the appearance of the finished board, and put it into storage if it is qualified, otherwise it will be scrapped.

[0054] Example:

[0055] A high-precision circuit board production process comprises the following steps:

[0056] Step 1, cutting: the sheet material is processed into the size that meets the engineering design through cutting, baking, planing and grinding.

[0057] Specifically, cutting: cutting large sheets of FR-4 double-sided substrate 1, PP prepreg board 2 and copper substrate 3 into suitable production specifications and sizes. Through engineering design layout, multiple finished boards of this specification and size can be processed simultaneously.

[0058] Baking board: Bake the FR-4 double-sided substrate 1 to remove moisture and eliminate the internal stress of the material to prevent the board from warping.

[0059] Planing: Process the edge of the board to make it smooth and without sharp edges to avoid adverse effects on subsequent processes.

[0060] Corner grinding: The edges and corners of the sheet are rounded to avoid adverse effects on subsequent processes.

[0061] Step 2, processing of the FR-4 double-sided substrate 1: The FR-4 double-sided substrate 1 is composed of an insulating board 12 and copper foils 13 arranged on both sides of the insulating board 12, and the inner layer graphic circuit and the outer layer graphic circuit are respectively arranged on the copper foils 13 on both sides.

[0062] In this step, a plurality of via holes 11 are firstly drilled on the FR-4 double-sided substrate 1, and then an inner layer graphic circuit is produced on the copper foil 13 on one side of the FR-4 double-sided substrate 1 through the steps of copper deposition - electroplating - dry film pasting - exposure - development - etching - removal of dry film and excess copper foil.

[0063] Specifically, a via hole 11 is drilled on the FR-4 double-sided substrate 1 by mechanical drilling. The via hole 11 is used to form a conductive loop between the copper foils 13 on both sides after copper deposition. Then, an automatic hole inspection machine is used to inspect the via hole 11.

[0064] After the drilling is completed, the FR-4 double-sided substrate 1 is subjected to copper deposition, that is, a thin layer of copper is deposited on the FR-4 double-sided substrate 1 and the hole wall of the via hole 13 to facilitate electroplating and metallize the hole to achieve interlayer conduction.

[0065] The copper deposition process specifically includes:

[0066] S1, copper plating pre-treatment: FR-4 double-sided substrate 1 is ground to remove the burrs and scratches on the board, and clean the dust on the board surface and in the holes;

[0067] S2, copper deposition: using redox reaction, a thin copper layer is deposited on the surface of the FR-4 double-sided substrate 1 and in the via hole 13;

[0068] S3, backlight level test: by making hole wall slices and observing them with a metallographic microscope, the coverage of the deposited copper on the surface of the FR-4 double-sided substrate 1 and the inner wall of the via hole 13 is confirmed.

[0069] After copper deposition is completed, the FR-4 double-sided substrate 1 is fixed to the carrier with a cable tie and electroplated by a vertical continuous plating line (VCP for short). The electroplating process can appropriately thicken the surface of the FR-4 double-sided substrate 1 and the copper layer in the via 13 to ensure the reliability of the interconnection between the PCB layers.

[0070] After the electroplating is completed, the copper foil 13 on the side of the FR-4 double-sided substrate 1 close to the copper substrate 3 is processed with an inner layer pattern circuit on the copper foil 13 by pattern transfer.

[0071] Graphic transfer specifically includes:

[0072] S1, Graphics pre-treatment: Clean the surface of the FR-4 double-sided substrate 1 to ensure that the board surface is dry, clean, free of oxidation, glue stains, etc. before sticking the dry film.

[0073] S2, dry film pasting: photosensitive material, i.e. dry film, is pasted on the copper surface through a laminator.

[0074] S3, exposure: using the principle of photosensitive photography, the dry film is exposed to ultraviolet light, a polymerization reaction occurs, and the pattern transfer is completed. To ensure the accuracy of the pattern transfer, the present invention uses an LDI exposure machine to perform the pattern transfer.

[0075] S4, DES (development, etching, and stripping): After development, etching, stripping, and removing the dry film and excess copper foil outside the pattern, the required inner layer pattern circuit is produced.

[0076] Step 3, processing the copper substrate 3: that is, making a first positioning hole 31 , a heat dissipation boss 32 and an annular boss 33 on the copper substrate 3 .

[0077] Specifically, the present invention takes a copper substrate 3 with a thickness of 1.5 mm as an example. First, the first positioning holes 31 with a diameter of 2.525 mm are drilled by a drilling machine at the positions near the four corners of the copper substrate 3, which are used to locate the position of the annular boss 33 and provide a positioning reference for subsequent processing. In addition, the center of each first positioning hole 31 is 8 mm away from the edge of the copper substrate 3 near its corner. Then, a dry film is pasted on the copper substrate 3, and the images of the heat dissipation boss 32 and the annular boss 33 are transferred to the copper substrate 3 by exposure and development using an LDI exposure machine; finally, the heat dissipation boss 32 and the annular boss 33 are etched on the copper substrate 3 by exposing the dry film protection, that is, after the area of ​​the copper substrate 3 not protected by the dry film is uniformly etched downward by 0.3 mm, a heat dissipation boss 32 and annular boss 33 protruding upward by 0.3 mm are formed on the copper substrate 3. The diameter of the annular boss 33 is 10.525 mm, and the concentric arrangement of the first positioning hole 31 and the annular boss 33 forms a height difference between the PP prepreg 2 and the upper end surface of the annular boss 33, thereby preventing the flowing colloid formed after the PP prepreg 2 melts from flowing into the first positioning hole 31. The first positioning hole 31 is used as a positioning reference hole in etching the heat dissipation boss, laminating, making the outer layer graphic circuit and molding, so as to reduce the cumulative tolerance generated in each process, ensure that the tolerance of the finished board is controlled within + / -0.06, and obtain a finished board with a certain precision.

[0078] Step 4, processing the FR-4 double-sided substrate 1 and the PP semi-cured board 2, that is, gong out the inner groove A and the second positioning hole B on the FR-4 double-sided substrate 1 and the PP semi-cured board 2 respectively by a gong machine to avoid the heat dissipation boss 32 and the annular boss 33.

[0079] Specifically, the outline size of the inner groove A is slightly larger than the outer size of the heat dissipation boss 32, the second positioning hole B is concentrically arranged with the annular boss 33, and the diameter of the second positioning hole B is slightly larger than the diameter of the annular boss 33, that is, there is a certain gap between the inner wall of the inner groove A and the outer wall of the heat dissipation boss 31, and there is a certain gap between the second positioning hole B and the annular boss 33, which is used to prevent the overflow of the colloid during lamination. At the same time, based on the position of the first positioning hole 31, the distance between the center of the second positioning hole B and the edge of the copper substrate 3 near its end corner is 8mm, so as to reduce the amount of colloid flowing to the edge of the board during lamination.

[0080] Step 5, preparation before lamination, is to stack the copper substrate 3, PP semi-cured board 2, FR-4 double-sided substrate 1 and release film 4 in sequence and fix them by rivets 6 to form a preliminary laminated board to prevent displacement and misalignment between the single boards during the lamination process, which affects the accuracy of the finished board.

[0081] Specifically, first, clean the FR-4 double-sided substrate 1 and the copper substrate 3 to remove oxidation corrosion, dry stripping film, and eliminate residues and any fingerprints. Use brown solution to treat the copper surface to form an oxide film layer (i.e., browning). The browning treatment provides better adhesion for the epoxy resin and avoids the problem of delamination.

[0082] Secondly, three riveting positioning holes 5 with a diameter of 3.2 mm are drilled on the two opposite long sides of the copper substrate 3. Among them, the distance between the center of the riveting positioning hole 5 and the long side of the board edge is 6 mm, and the three riveting positioning holes 5 are asymmetrically spaced and distributed between the two annular bosses 33. The asymmetrical spacing arrangement of the riveting positioning holes 5 can prevent the boards from being reversed during the stacking process without being discovered, which plays a fool-proof role. Then, holes corresponding to the positions of the riveting positioning holes 5 are drilled on the PP semi-cured board 2 and the FR-4 double-sided substrate 1, and then the copper substrate 3, the PP semi-cured board 2, the FR-4 double-sided substrate 1 and the two layers of release film 4 are stacked from bottom to top on the positioning fixture of the riveting machine to form a laminated board; then, rivets 6 are placed on each riveting positioning hole 5, and the rivets 6 are preferably flat-headed semi-hollow rivets. The rivets 6 are pressurized by the riveting machine to expand and deform, so that the laminated boards are stacked and fixed to obtain a preliminary laminated board, which provides a guarantee for subsequent lamination.

[0083] It can be understood that the heat dissipation boss 32 and the annular boss 33 of the copper substrate 3 sequentially pass through the inner groove A and the second positioning hole B on the PP semi-cured board 2 and the FR-4 double-sided substrate 1, and then two release films 4 with thicknesses of 0.03 mm and 0.12 mm are sequentially laid on the upper surface of the FR-4 double-sided substrate 1 to obtain a laminated board. At this time, the superimposed thickness of the PP semi-cured board 2 and the FR-4 double-sided substrate 1 is equal to the height of the heat dissipation boss 32 and the annular boss 33, that is, the superimposed thickness is equal to 0.3 mm, thereby ensuring that the two release films 4 are on a horizontal plane, and the riveting positioning holes on the release films 4 can be punched out by the pressure of the rivet 6.

[0084] Finally, in this embodiment, the release film is a fluoroplastic film made of a silicon fluoride coating, which has the characteristics of high temperature resistance and easy removal. During lamination, the top surface of the laminate is covered with the release film and the first positioning hole 31, which prevents the resin from flowing into the first positioning hole 31 during lamination, thereby ensuring the flatness of the lamination surface.

[0085] Step 6, lamination and debonding, press the preliminary laminate.

[0086] Specifically, the preliminary laminate is placed in the press. During the lamination process, the epoxy resin of the PP prepreg 2 melts after being heated, and becomes a flowing colloid. The colloid overflows upward through the gap formed between the heat dissipation boss 32 and the inner groove A, the gap formed between the annular boss 33 and the second positioning hole B, and the through hole 11, thereby ensuring that the first positioning hole 31 is not blocked by the colloid. After the colloid solidifies, the release film 4 is torn off, and the overflowed glue is removed by a ceramic grinding plate; at this time, each layer of the single board is tightly pressed together to form a reliable insulation layer.

[0087] Step 7, making the outer layer circuit, that is, making the pattern circuit on the copper foil 13 located on the outer layer.

[0088] Specifically, the first positioning hole 31 is used as the positioning reference hole to produce the outer layer graphic circuit on the outer layer of the FR-4 double-sided substrate 1 to complete the preliminary production of the circuit board; the outer layer graphic circuit is formed by dry film pasting-exposure-development-graphic electroplating-etching. Except that the production sequence of the outer layer graphic circuit is different from that of the inner layer graphic circuit, the specific operation method of the single step is the same as that of the inner layer graphic circuit, which will not be repeated here. In the future, the first positioning hole 31 can also be used as a product installation hole for the finished board.

[0089] Step 8, optical inspection: Specifically, the circuit board is first compared with the 0K pattern through the automatic optical inspection equipment (AOI scanner) to find the difference position; then it is inspected by the repair machine (VRS), and the difference position is judged one by one. After the judgment, the product is scrapped or repaired.

[0090] Step 9, solder mask: that is, a layer of solder mask ink is covered on the copper surface that does not need to be soldered. During the DIP and SMT process, the tin liquid or solder paste will not react with the solder mask oil film, thereby avoiding problems such as tin short circuit. The color of the solder mask is conventionally green, and there are also blue, black, white and red. The corresponding selection is made according to the purpose of the product and the needs of the customer. In this embodiment, black ink is selected.

[0091] The specific process of solder mask includes:

[0092] S1, pre-treatment: the function is to clean and roughen the copper surface, so as to increase the bonding force between the oil film and the copper surface in the subsequent processing;

[0093] S2, printing: the solder mask oil film is covered on the entire board surface by printing, and the screen printing thickness of the solder mask ink is 30μm;

[0094] S3, pre-baking: Since the ink is in liquid state after spraying, it needs to be pre-baked before the next step;

[0095] S4, exposure: solidify the ink to be retained by a CCD exposure machine;

[0096] S5, Development: Remove the uncured ink with sodium carbonate solution to expose the copper surface.

[0097] Step 10, printing text: text, also known as characters, is the number or letter on the circuit board. The most common is white text, of course, there are black or other colors. Its main function is to mark the location and quantity of components on the circuit board. At the same time, the production cycle or some signs according to customer needs will be displayed on the circuit board in the form of characters.

[0098] The specific steps of text printing include:

[0099] S1, Programming: Write the printing program according to the product-related information required to be printed;

[0100] S2, printing: use the printing machine to call the printing program to print product related information on the circuit board;

[0101] S3, baking: bake the printed ink to complete the curing of the text and ensure the adhesion of the solder mask ink and the text.

[0102] Step 11, surface treatment: The copper surface not covered by the solder resist ink (such as pads, hole rings, cursor points, etc.) is easily oxidized. Therefore, a surface treatment layer 7 is formed on the copper surface not covered by the solder resist ink through a chemical nickel-palladium-gold process. The copper surface is covered with a nickel-palladium-gold layer to delay the oxidation of the copper surface, and it can easily react with the tin solution or solder paste of the subsequent DIP or SMT process, which is beneficial to welding.

[0103] The specific process of nickel-palladium-gold process is: degreasing-micro-etching-pre-impregnation-activation-nickel deposition-palladium deposition-gold deposition-drying, and each link will undergo multi-stage water washing treatment. Among them, the nickel layer, nickel layer 3-7.5μm, palladium layer 0.07-0.15μm, gold layer 0.08-0.21μm. Compared with other surface treatment methods, nickel-palladium-gold is suitable for lead-free welding. The surface is very flat, suitable for SMT, and strong resistance to environmental attacks.

[0104] Step 12, molding: using the first positioning hole 31 as the positioning reference hole, a high-precision punch is used to punch out the non-electroplated through hole 8 in the unit board and the unit board shape according to the customer's requirements for the finished board to obtain the finished board required by the customer.

[0105] During the molding process, the size and appearance of the first piece are inspected through two-dimensional or three-dimensional inspection, such as dust, burrs, white spots, etc. After the first piece inspection is qualified, batch molding is carried out to ensure product quality.

[0106] The first positioning hole is used as the positioning reference hole throughout the production process to avoid cumulative processing errors, so that the tolerance from the center of the heat dissipation boss 32 to the center of the non-electroplated through hole 8 is controlled within + / -0.06mm, see the attached Figure 3 The medium dimensions T+ / -0.06 and L+ / -0.06 improve the position accuracy of the heat dissipation bosses and the inner and outer graphic circuits, making the finished board meet the high-precision tolerance requirements.

[0107] Step 13, electrical testing: also known as electrical performance testing, functional testing or open-short circuit testing, etc., mainly involves performing open-short circuit testing on the network of the finished board through the test points where the test needle contacts the network. Automatic testing machines are often used to pick out bad boards, which is highly efficient and saves testing time.

[0108] Step 14, inspection and warehousing: Inspect the appearance of the finished board, and put it into storage if it is qualified, otherwise it will be scrapped.

[0109] Appearance inspection mainly includes:

[0110] 1. Appearance inspection of solder mask, text, molding and surface treatment: including dirty ink and debris on the board surface, blurred and incomplete text, ink deviation, burrs and white spots on the board edge, uneven surface treatment and oxidation, etc.

[0111] 2. Through-hole quality: Check whether the through-hole is blocked (plug-in hole), whether the hole is plugged as required, etc. Specifically, the drilling data is input into the program, the allowable tolerance is input, and then the hole inspection machine is used for automatic inspection, and the products that are detected as NG are manually reviewed.

[0112] 3. Board bending and warping inspection: Board bending and warping have a great impact on the downstream patch of the finished board. If it exceeds the standard, it may cause patch problems such as cold soldering, tombstone, and poor tinning. Specifically, place the finished board on the marble table and use a plug gauge to check it or use a board bending and warping inspection machine for automatic inspection.

[0113] In summary, the high-precision circuit board production process provided by the present invention uses the first positioning hole as the positioning reference hole throughout the entire production process to avoid cumulative processing errors and improve the position accuracy of the heat dissipation boss and the inner and outer layer graphic circuits; the stacked boards are overlapped and fixed by rivets to ensure that there is no displacement between the single boards during the lamination process, thereby improving the lamination accuracy; by etching an annular boss around the first positioning hole, the flowable colloid generated by the heat melting of the PP semi-cured board during the lamination process overflows through the gap formed between the annular boss and the second positioning hole, preventing the colloid from overflowing into the first positioning hole, providing a positioning basis for subsequent high-precision graphic transfer, and ensuring that the precision tolerance of the finished board is controlled within + / -0.06mm.

[0114] Many specific details are described in the above description to facilitate a full understanding of the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited to the specific implementation disclosed above. At the same time, any person familiar with the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A high-precision circuit board production process, characterized in that: The following steps are involved: Step 1, cutting: cutting the required FR-4 double-sided substrate (1), PP prepreg substrate (2) and copper substrate (3) into specific sizes for subsequent processing; Step 2, processing of the FR-4 double-sided substrate (1): drilling a plurality of via holes (11) on the FR-4 double-sided substrate (1), and making an inner layer pattern circuit on one side of the FR-4 double-sided substrate (1); Step 3, processing the copper substrate (3): the copper substrate (3) is provided with first positioning holes (31) respectively near the four end corners thereof, and the first positioning holes (31) are used as positioning references. A heat dissipation boss (32) and an annular boss (33) concentric with the first positioning hole (31) are formed on the copper substrate (3) by dry film pasting, exposure, development, and etching; That is, after the area of ​​the copper substrate (3) not protected by the dry film is uniformly etched downward, an upwardly protruding heat dissipation boss (32) and an annular boss (33) are formed on the copper substrate (3), so that a height difference is formed between the upper end surface of the PP prepreg board (2) and the annular boss (33); Step 4, processing of the FR-4 double-sided substrate (1) and the PP semi-cured board (2): an inner groove (A) and a second positioning hole (B) are respectively formed on the FR-4 double-sided substrate (1) and the PP semi-cured board (2), wherein the outline dimension of the inner groove (A) is slightly larger than the outer dimension of the heat dissipation boss (32), the second positioning hole (B) is concentrically arranged with the annular boss (33), and the diameter of the second positioning hole (B) is slightly larger than the diameter of the annular boss (33); in addition, the distance between the center of the second positioning hole (B) and the edge of the copper substrate (3) near its end corner is 8 mm; Step 5, preparation before lamination: after the FR-4 double-sided substrate (1) and the copper substrate (3) are subjected to browning treatment, a plurality of corresponding riveting positioning holes (5) are respectively opened on the FR-4 double-sided substrate (1), the PP semi-cured board (2) and the copper substrate (3), and then the PP semi-cured board (2), the FR-4 double-sided substrate (1) and the release film (4) are sequentially stacked on the copper substrate (3) to form a laminated board, and a plurality of rivets (6) are respectively passed through the corresponding riveting positioning holes (5) to stack and fix the laminated boards to form a preliminary laminated board; The release film (4) is provided with two layers, and the thicknesses of the two layers of the release film (4) are 0.03 mm and 0.12 mm from bottom to top respectively; Step 6, lamination and glue removal: the preliminary laminate is placed on a press for lamination. During the lamination process, the PP semi-cured board (2) is heated and melted to produce a flowable colloid, which overflows upward through the gap formed between the heat dissipation boss (32) and the inner groove (A), the gap formed between the annular boss (33) and the second positioning hole (B), and the via hole (11). After the colloid solidifies, the release film (4) is torn off, and the overflowed glue is removed by a ceramic grinding plate; Step 7, fabrication of outer layer circuits: using the first positioning hole (31) as a positioning reference, fabricating outer layer graphic circuits on the upper layer of the FR-4 double-sided substrate (1), thereby completing the preliminary fabrication of the circuit board; Step 8, optical inspection: Use optical principles to compare data, inspect the circuit board, and carry out corresponding repairs or scrapping; Step 9, solder mask: Cover the copper surface of the circuit board that does not need to be soldered with a layer of solder mask ink; Step 10, printing text: using a printer to mark product related information on the circuit board; Step 11, surface treatment: forming a surface treatment layer (7) on the copper surface not covered by the solder mask ink by chemical nickel-palladium-gold process; Step 12, molding: using the first positioning hole (31) as a positioning reference, a high-precision punching machine is used to punch out the non-electroplated through hole (8) in the unit board, and then the unit board shape is punched out to obtain the finished board required by the customer; Step 13, electrical testing: the circuit network of the finished board is tested for open circuit and short circuit by contacting the test points of the network with the test needle to remove the bad board; Step 14, inspection and warehousing: Inspect the appearance of the finished board, and put it into storage if it is qualified, otherwise it will be scrapped.

2. The high-precision circuit board production process according to claim 1, characterized in that : In step 1, the sheet material is processed into a specific size through cutting, baking, planing and grinding.

3. The high-precision circuit board production process according to claim 1, characterized in that: The FR-4 double substrate (1) is composed of an insulating board (12) and copper foils (13) arranged on both sides of the insulating board (12), and the inner layer graphic circuit and the outer layer graphic circuit are respectively arranged on the copper foils (13) on both sides.

4. The high-precision circuit board production process according to claim 1, characterized in that: In step 2, the inner layer graphic circuit is formed by copper deposition - electroplating - dry film pasting - exposure - development - etching - removal of dry film and excess copper foil.

5. The high-precision circuit board production process according to claim 1, characterized in that: In step 7, the outer layer pattern circuit is formed by dry film lamination, exposure, development, pattern electroplating, and etching.

6. The high-precision circuit board production process according to claim 1, characterized in that: The step 8 specifically includes: using an automatic optical inspection device to compare the circuit board with the OK pattern to find the difference position; then using a repair machine to judge the difference position one by one, and repair or scrap it.

7. The high-precision circuit board production process according to claim 1, characterized in that: The step 9 specifically includes: solder resist pre-treatment—printing solder resist ink—pre-baking—exposure by a CCD exposure machine—development, wherein the thickness of the solder resist ink is 20-40 μm.

8. The high-precision circuit board production process according to claim 1, characterized in that: The step 10 specifically includes: writing a printing program according to the product-related information required to be printed on the product - using a printing machine to call the printing program to print the product-related information on the circuit board - baking the printing ink to solidify it and adhere to the circuit board.

9. The high-precision circuit board production process according to claim 1, characterized in that: In step 11, the specific steps of the chemical nickel-palladium-gold process include: degreasing - micro-etching - pre-immersion - activation - nickel precipitation - palladium precipitation - gold precipitation - drying.

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