High-frequency PCB blind slot metallization process

Abstract

The invention provides a high-frequency PCB blind slot metallization technology. The technology comprises the following steps of cutting, board baking, inner layer circuit etching, AOI, electric milling, laser pre-control, PP cutting, PP electric milling, aluminum sheet preparation, center control, board stacking, aluminum sheet burying, press fit, outer layer manufacturing after press fit, resin hole plugging, cap copper manufacturing, outer layer circuit etching, solder resist printing, character post-baking, depth-controlled milling, uncovering, sand blasting and blind slot metallization, wherein the steps include cutting, board baking, inner layer circuit etching, AOI, electric milling, laser pre-control, PP cutting, PP electric milling, aluminum sheet preparation, center control, board stacking, aluminum sheet burying, press fit, outer layer manufacturing after press fit, resin hole plugging, cap copper manufacturing, outer layer circuit etching and solder resist printing. The quality problem that the blind groove size is larger than or equal to 5 mm * 5 mm, and in the subsequent process, the layered explosion board has bumps is solved; after the blind groove is uncovered, no PP glue flow problem exists at the chamfering position, and the quality problems that the cost is increased and golden fingers or bonding pads are easily damaged due to manual scraping by using a blade are reduced; after the medium at the position of the groove is uncovered, the tawny high-temperature adhesive tape does not need to be manually uncovered, the problem that the adhesive tape is left on a golden finger or a bonding pad copper surface is avoided, an eraser or a jig does not need to be manually used for cleaning, time consumption is reduced, the quality problem of anti-plating metallization is avoided, and the product yield is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of PCB, in particular to a high-frequency PCB blind slot metallization process. BACKGROUND

[0002] The current circuit board blind slot metallization process: a size equal to the slot size of the brown high-temperature adhesive tape is pasted on the copper surface of the blind slot bottom pad or the gold-plated finger, and then the board core layer is pressed together and buried in the board. After pressing, the medium at the blind slot position is removed by mechanical depth control after the completion of the processing in each process flow. Then, the brown high-temperature adhesive tape is manually removed. Then, the slot is chamfered, the PP glue is cleaned, and the remaining glue of the brown high-temperature adhesive tape is removed. Then, sand blasting + chemical cleaning (micro-etching + pickling) is performed. Finally, the gold finger metallization in the slot is performed. The process has the following problems:

[0003] 1. For the case where the blind slot size is greater than 5mm*5mm, there is a quality risk of delamination and explosion of the board due to bulging in the post-process baking + electroplating + character baking;

[0004] 2. After the blind slot cover is removed, the PP glue flows to the copper surface or the gold finger at the chamfered position, which needs to be scraped off by manual use of a blade, increasing the cost and easily damaging the gold finger or pad, seriously affecting the quality;

[0005] 3. When the medium at the slot position is removed, part of the adhesive tape will remain on the gold finger or pad copper surface at high temperature during pressing, which needs to be cleaned by manual use of a rubber eraser or a jig, which is time-consuming and has a quality problem of anti-plating metallization. SUMMARY

[0006] The problem to be solved by the present application is to provide a high-frequency PCB blind slot metallization process to simplify the production process and reduce the product failure rate.

[0007] To solve the above technical problems, the present application provides a high-frequency PCB blind slot metallization process, which comprises the following steps:

[0008] a. Cutting + baking: using high-frequency board core cutting, baking the board core to dry the water vapor on the copper-clad plate;

[0009] b. Inner layer circuit + etching: paste a dry film on the soft plate surface under certain temperature and pressure, then align with the negative, finally use ultraviolet light in the exposure machine to make the dry film not covered by the negative react, form the required circuit pattern on the plate surface, then dissolve the film not irradiated by light through the developing section, then etch the exposed copper through the etching section, finally remove the film through the film removing section to expose the upper layer circuit pattern on the soft plate;

[0010] c. AOI + electro-milling + laser pre-control: AOI detection is performed on the inner layer circuit, and the defective board is removed, and the good board is reserved. The medium at the position where the cover is to be removed is milled in advance by electro-milling, and the single-layer board core is pre-controlled to a depth of 0.1 mm at the controlled depth position by laser.

[0011] d. PP cutting + PP electro-milling: PP cutting is performed, and PP is electro-milled into different window sizes. The first PP is milled 3-5 mm more than the second PP in the window extension, and the second PP is milled 2-3 mm more than the third PP in the window extension.

[0012] e. Aluminum sheet preparation: aluminum sheets are prepared according to the size of the cover removal area.

[0013] f. Control center + stacking + aluminum sheet embedding + pressing: after all the board core layers are browned, they are stacked together with the PP according to the structure diagram, the aluminum sheet is placed in the cover removal groove, and the top layer of the board core is stacked, and then pressing is performed.

[0014] g. Outer layer production after pressing: after pressing, brown + laser drilling + mechanical drilling + back drilling are performed, and then plasma activation + copper plating + hole filling electroplating is performed, and the outer layer circuit + etching is performed.

[0015] h. Resin hole filling + cap copper making + outer layer circuit + etching.

[0016] i. Solder mask printing + character post-baking + depth milling: depth milling is performed on the PCB board blind slot position using mechanical medium electro-milling method.

[0017] j. Cover removal + sandblasting: the aluminum sheet at the blind slot position is removed, and the blind slot is cleaned by sandblasting.

[0018] k. Blind slot metallization: gold finger at the bottom of the blind slot is treated by gold plating.

[0019] Preferably, the thickness of the board cut in step a is 0.127 mm, the copper thickness is 18 um, the baking temperature is 170°C, and the baking time is 2h.

[0020] Preferably, the aluminum content of the aluminum sheet in step e is ≥99.9%.

[0021] Preferably, the length and width of the aluminum sheet in step e are 0.1 mm smaller than the length and width of the cover removal medium slot, and the thickness of the aluminum sheet is one thickness of the cut board core smaller than the thickness of the cover removal medium slot.

[0022] The beneficial effects of the present application are: the present application provides a high-frequency PCB blind slot metallization process, the different thickness of the medium in the circuit board uncovering area and the PP are washed away in advance by electrical milling, the PP of different layers of the medium is also milled in advance, only the uppermost board core is reserved, and the board core in the lowest layer of the uncovering medium uses laser pre-pore with a depth of 0.08 mm and a width of 1 mm; the PP used in the uncovering area selects two pieces of PP with a flow amount of R04450F / 56%, and the two pieces of PP are designed to have a window difference of 4 mm with the PP of other layers in the uncovering position; when the laminated board is pressed, the aluminum sheet is manually inserted into the hollow board in the uncovering area, the surface of the aluminum sheet directly contacts the bottom of the blind slot and is pressed together, because the surface of the aluminum sheet is smooth and not easy to combine with the PP and the medium of the board core, after the related post-process processing is completed, the aluminum sheet is removed by direct control deep uncovering, and the gold finger or pad at the bottom of the blind slot is exposed.

[0023] The quality problem of the layered and exploded board caused by the bulging of the blind slot with a size of greater than or equal to 5 mm*5 mm in the post-process baking plate + electroplating + character baking plate is solved.

[0024] After the blind slot is uncovered, there is no PP glue flow problem at the chamfer position, the use of blades to scrape off increases the cost and is easy to cause quality problems such as damage to the gold finger or pad;

[0025] After the medium at the uncovered slot position is uncovered, there is no need for manual removal of the brown high-temperature adhesive tape, which avoids the problem of residual adhesive tape on the copper surface of the gold finger or pad, and there is no need for manual cleaning using a rubber eraser or jig, which reduces time consumption and avoids the quality problem of anti-plating metallization;

[0026] The manual processing of a large amount of time is reduced, and the product yield is improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 An example of the structure of the present application after cutting + baking plate is shown.

[0028] Figure 2 An example of the structure of the present application after inner layer circuit + etching is shown.

[0029] Figure 3 An example of the structure of the present application after AOI + electrical milling + laser pre-control is shown.

[0030] Figure 4 An example of the structure of the present application after control center + laminated board + aluminum sheet embedding + pressing is shown.

[0031] Figure 5 An example of the structure of the present application after pressing is shown.

[0032] Figure 6 An example of the structure of the present application after resin plug + cap copper + outer layer circuit + etching is shown.

[0033] Figure 7 This illustration shows the structure of the present invention after solder mask printing + character post-baking + controlled depth milling.

[0034] Figure 8 A schematic diagram of the structure of the present invention after the cover is removed is shown.

[0035] Figure 9 A schematic diagram illustrating the structure of the present invention after sandblasting is shown.

[0036] Figure 10 A schematic diagram illustrating the structure of the present invention after blind slot metallization is shown. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure.

[0038] Based on the embodiments described in this disclosure, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this disclosure.

[0039] refer to Figures 1-10 .

[0040] This invention provides a high-frequency PCB blind slot metallization process, comprising the following steps:

[0041] a. Cutting and baking: Use high-frequency board core cutting and bake the board core to dry the moisture on the copper-clad board;

[0042] b. Inner layer circuit + etching: Under certain temperature and pressure, a dry film is applied to the flexible circuit board, and then the film is aligned. Finally, the dry film not covered by the film is irradiated by ultraviolet light in the exposure machine to react and form the required circuit pattern on the board surface. Then, the film that has not been exposed to light is dissolved by the developing solution in the developing section. The exposed copper is etched away by the acid etching solution in the etching section. Finally, the film is removed by the stripping solution in the stripping section, exposing the upper layer circuit pattern of the flexible circuit board.

[0043] c. AOI + Electric Milling + Laser Pre-control: AOI inspection is performed on the inner layer circuit to remove defective boards and keep good boards. The dielectric in the area that needs to be covered is milled off in advance by electric milling. Laser pre-control is used to pre-control the depth of the single-layer core at the depth control position to 0.1mm.

[0044] d. PP cutting + PP electric milling: Perform PP cutting and electric milling to cut PP into different window sizes. The first PP sheet is milled 3-5mm more inward than the second PP sheet, and the second PP sheet is milled 2-3mm more inward than the third PP sheet.

[0045] e. Aluminum sheet preparation: Prepare aluminum sheets according to the size of the uncovered area;

[0046] f. Control Center + Stacking Plates + Embedded Aluminum Sheets + Pressing: After all the core layers have been browned, stack them together with the PP according to the structural diagram, then place the aluminum sheets in the cover groove, and stack the top core layer on top, and then press them together.

[0047] g. Fabrication of outer layer after lamination: After lamination, browning + laser drilling + mechanical drilling + back drilling are performed, followed by plasma activation + copper plating + hole filling electroplating, outer layer circuitry + etching.

[0048] h, Resin plugging + copper capping + outer layer circuitry + etching;

[0049] i. Solder mask printing + character post-baking + controlled depth milling: Controlled depth milling is performed on the PCB blind slot using mechanical electro-milling of the dielectric.

[0050] j. Remove the cover and sandblast: Remove the aluminum sheet at the blind groove location and clean the blind groove with sandblasting;

[0051] k. Metallization of blind slots: The gold fingers at the bottom of the blind slots are metallized.

[0052] Based on the above embodiments, the thickness of the board in step a is 0.127 mm, the copper thickness is 18 μm, the baking temperature is 170°C, and the baking time is 2 h.

[0053] Based on the above embodiments, the aluminum content of the aluminum sheet in step e is ≥99.9%.

[0054] Based on the above embodiments, the length and width of the aluminum sheet in step e are 0.1 mm smaller than the length and width of the uncovered medium groove, and the thickness of the aluminum sheet is less than the thickness of the uncovered medium groove by the thickness of one sheet core of the cut plate.

[0055] By pre-milling the dielectric layer and PP in the circuit board cover area, dielectrics of different thicknesses in the area are washed away. PP layers with different dielectric layers are also pre-milled away, leaving only the topmost core layer. Laser pre-drilling is used on the core layer of the lowest dielectric layer in the cover area, with a depth of 0.08mm and a width of 1mm. Two sheets of R04450F / 56% flow rate PP are selected for the cover area. The two sheets are designed with windows at the cover position, differing from the other PP layers by 4mm. During the lamination and stacking of the boards, aluminum sheets are manually inserted into the empty shell board in the cover area. The aluminum sheet surface directly contacts the bottom of the blind slot and is pressed together. Because the surface of the aluminum sheet is smooth, it is not easy for it to bond with PP and core dielectric. After lamination and related post-processing, the aluminum sheet is removed by direct control deep cover-up, exposing the gold fingers or pads at the bottom of the blind slot.

[0056] This solves the quality problem of bulging, delamination, and board bursting that would occur in the subsequent baking process of blind groove size ≥5mm*5mm, including baking plate, electroplating, and character baking plate.

[0057] There is no PP glue flow at the chamfered area after the blind slot is uncovered. Reducing manual scraping with a blade increases costs and can easily damage the gold fingers or solder pads.

[0058] After removing the medium from the slot, there is no need to manually remove the brown high-temperature tape, avoiding the problem of tape residue on the gold fingers or copper pads. There is no need to manually clean it with an eraser or jig, reducing time consumption and avoiding quality problems related to anti-plating metallization.

[0059] Reduce the amount of time spent on manual processing and improve product yield.

[0060] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high-frequency PCB blind slot metallization process, characterized in that, It includes the following steps: a. Cutting and baking: Use high-frequency board core cutting and bake the board core to dry the moisture on the copper-clad board; b. Inner layer circuit + etching: Under certain temperature and pressure, a dry film is applied to the flexible circuit board, and then the film is aligned. Finally, the dry film not covered by the film is irradiated by ultraviolet light in the exposure machine to react and form the required circuit pattern on the board surface. Then, the film that has not been exposed to light is dissolved by the developing solution in the developing section. The exposed copper is etched away by the acid etching solution in the etching section. Finally, the film is removed by the stripping solution in the stripping section, exposing the upper layer circuit pattern of the flexible circuit board. c. AOI + Electric Milling + Laser Pre-control: AOI inspection is performed on the inner layer circuit to remove defective boards and keep good boards. The dielectric in the area that needs to be covered is milled off in advance by electric milling. Laser pre-control is used to pre-control the depth of the single-layer core at the depth control position to 0.1mm. d. PP cutting + PP electric milling: Perform PP cutting and electric milling to cut PP into different window sizes. The first PP sheet is milled 3-5mm more inward than the second PP sheet, and the second PP sheet is milled 2-3mm more inward than the third PP sheet. e. Aluminum sheet preparation: Prepare aluminum sheets according to the size of the uncovered area; f. Control Center + Stacking Plates + Embedded Aluminum Sheets + Pressing: After all the core layers have been browned, stack them together with the PP according to the structural diagram, then place the aluminum sheets in the cover groove, and stack the top core layer on top, and then press them together. g. Fabrication of outer layer after lamination: After lamination, browning + laser drilling + mechanical drilling + back drilling are performed, followed by plasma activation + copper plating + hole filling electroplating, outer layer circuitry + etching. h, Resin plugging + copper capping + outer layer circuitry + etching; i. Solder mask printing + character post-baking + controlled depth milling: Controlled depth milling is performed on the PCB blind slot using mechanical electro-milling of the dielectric. j. Remove the cover and sandblast: Remove the aluminum sheet at the blind groove location and clean the blind groove with sandblasting; k. Metallization of blind slots: The gold fingers at the bottom of the blind slots are metallized.

2. The high-frequency PCB blind slot metallization process according to claim 1, characterized in that, The thickness of the board in step a is 0.127 mm, the copper thickness is 18 μm, the baking temperature is 170°C, and the baking time is 2 hours.

3. The high-frequency PCB blind slot metallization process according to claim 2, characterized in that, The aluminum content of the aluminum sheet in step e is ≥99.9%.

4. The high-frequency PCB blind slot metallization process according to claim 3, characterized in that, The length and width of the aluminum sheet in step e are 0.1 mm smaller than the length and width of the uncovered medium groove, and the thickness of the aluminum sheet is less than the thickness of the uncovered medium groove by the thickness of one core sheet of the cut material.

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