Preparation method of high-order HDI stepped golden finger circuit board

Abstract

The invention relates to the technical field of PCB manufacturing, in particular to a preparation method of a high-order HDI stepped golden finger circuit board. The invention provides a preparation method of a high-order HDI stepped golden finger circuit board. The preparation method comprises the following steps: preparing an inner-layer core board, preparing a daughter board and preparing a mother board in sequence; in the process of preparing the inner-layer core board, board drying, browning, board drying and pressing are sequentially carried out after the inner layer is inspected; in the process of preparing the daughter board, plasma degumming and blind hole bottom inspection are sequentially carried out after laser drilling, blind hole inspection is carried out after hole filling electroplating, HCT test is carried out after daughter board inspection, and board drying is carried out after brownification; in the process of preparing the mother board, plasma degumming and blind hole bottom inspection are sequentially carried out after laser drilling, and HCT test is carried out after outer layer inspection. According to the preparation method disclosed by the invention, the dimensional stability and reliability of the high-order HDI stepped golden finger circuit board are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB manufacturing, and particularly to a method for preparing a high-order HDI stepped gold finger circuit board. Background Art

[0002] A high-order HDI stepped gold finger is a special connection structure used in high-frequency and high-reliability electronic devices. On an insulating substrate, a printed circuit, a printed component, or a conductive pattern formed by combining the two is made according to a predetermined design, which is called a printed circuit; the finished board made by this method is called a printed circuit board or a printed wiring board (PCB board). The high-order HDI stepped gold finger is a key interconnection structure on the PCB board.

[0003] The high-order HDI stepped gold finger is mainly applied to the field of acceleration cards for AI servers. The design characteristics of the PCB board of the AI acceleration card carrying the GPU are as follows: (1) High-order HDI design. The improvement of AI computing power requires denser circuit patterns to be routed on the same-size PCB, resulting in an increase in the HDI order and the overall number of layers of the product; this poses challenges to the dimensional stability and reliability of the material's resistance to multiple pressings, as well as to the reliability of the laser blind vias and multi-order stacked vias and the alignment of multi-order blind vias on the PCB. (2) The AI acceleration card retains the hot-pluggable attribute of the PCIe gold finger of conventional graphics card products. Since the gold finger plugging and unplugging require a fixed board thickness, the board thickness requirement at the gold finger position is inconsistent with the overall board thickness of the product, leading to the design of the stepped gold finger, and the stepped gold finger requires the PCB cover-lifting process, further increasing its manufacturing complexity. (3) AI servers require high-frequency and high-speed signal transmission with low signal loss, so the performance such as the dielectric loss of the copper clad laminate needs to be continuously improved; from the perspective of material selection, after the PCIe bus is upgraded, the server's material requirements for CCL reach the very low loss and ultra-low loss levels, and such materials require special process parameters for processing.

[0004] In view of this, this invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a high-order HDI stepped gold finger circuit board, which can successfully manufacture a high-order HDI stepped gold finger circuit board with excellent dimensional stability and reliability.

[0006] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0007] The present invention provides a method for preparing a high-order HDI stepped gold finger circuit board, including: sequentially preparing an inner core board, a daughter board, and a mother board;

[0008] In the process of preparing the inner core board, after inner layer inspection, baking, brownification, baking, and lamination are carried out in sequence;

[0009] In the process of manufacturing the daughter board, after laser drilling, plasma desmearing and blind via bottom inspection are carried out in sequence, blind via inspection is carried out after through-hole plating, HCT test is carried out after daughter board inspection, and baking the board is carried out after brown oxidation.

[0010] In the process of manufacturing the mother board, after laser drilling, plasma desmearing and blind via bottom inspection are carried out in sequence, blind via inspection is carried out after through-hole plating, and HCT test is carried out after outer layer inspection.

[0011] Further, the method for manufacturing the high-order HDI stepped gold finger circuit board includes: sequentially manufacturing an inner layer core board, manufacturing daughter board I, manufacturing daughter board II, manufacturing daughter board III, manufacturing daughter board IV, and manufacturing the mother board;

[0012] The process for manufacturing the inner layer core board includes: sequentially carrying out blanking, inner layer dry film, inner layer etching, inner layer inspection, baking the board, brown oxidation, baking the board, and lamination;

[0013] The process for manufacturing daughter board I includes: sequentially carrying out target drilling, laser drilling, mechanical drilling, plasma desmearing, blind via bottom inspection, electroless copper plating, through-hole plating, blind via inspection, resin plugging of vias, ceramic grinding of the board, daughter board dry film, acid etching, daughter board inspection, HCT test, daughter board solder mask, daughter board wet film, daughter board dry film, daughter board development, gold finger plating, stripping the film, daughter board dry film, daughter board development, etching leads, stripping the film, pasting high-temperature adhesive, fast pressing, laser cutting, fast pressing, brown oxidation, baking the board, and lamination;

[0014] The processes for manufacturing daughter board II, manufacturing daughter board III, and manufacturing daughter board IV include: sequentially carrying out target drilling, laser drilling, drilling holes at the board edge, plasma desmearing, blind via bottom inspection, electroless copper plating, through-hole plating, blind via inspection, daughter board dry film, acid etching, daughter board inspection, HCT test, brown oxidation, baking the board, and lamination;

[0015] The process for manufacturing the mother board includes: sequentially carrying out target drilling, laser drilling, plasma desmearing, blind via bottom inspection, electroless copper plating, through-hole plating, blind via inspection, copper reduction, target drilling, drilling, plasma desmearing, electroless copper plating, electroplating, resin plugging of vias, ceramic grinding of the board, copper reduction, target drilling, drilling, plasma desmearing, electroless copper plating, panel electroplating, outer layer dry film, outer layer development, pattern electroplating, outer layer alkaline etching, outer layer inspection and HCT test, solder mask, characters, surface treatment, shaping, controlled-depth milling, and finished product cleaning.

[0016] Further, the resin material of the insulating layer in the high-order HDI stepped gold finger circuit board includes PPO.

[0017] Further, it includes at least one of the following features (1) to (3);

[0018] (1) Before brownification, the temperature of the baking plate is 170 - 190°C, and the time is 2 - 4h;

[0019] (2) After brownification, the temperature of the baking plate is 115 - 125°C, and the time is 30 - 60min;

[0020] (3) After brownification, the residence time between the baking plate and lamination ≤ 24h.

[0021] Further, the blind hole inspection is carried out after the blind via plating, so that the depression value after blind via plating ≤ 10μm.

[0022] Further, laser blind holes are formed by the laser drilling. The single - side ring width between the laser blind holes and the corresponding sub - outer - layer copper pads is 2 - 3mil, and the alignment offset between the corresponding sub - outer - layer copper pads and the laser blind holes does not exceed the single - side ring width;

[0023] And / or, the alignment method of the laser drilling is: using the board - edge positioning holes for positioning, ablating the target corresponding to the sub - outer - layer of the laser blind holes, and using the method of grasping the sub - outer - layer target for alignment to achieve the alignment between the laser blind holes and the corresponding sub - outer - layer copper pads.

[0024] Further, the alignment method during the pattern exposure of the daughter board and the mother board is: using a combination target of 1 mechanical drill hole and 4 - 20 laser blind holes located outside the mechanical drill hole for alignment. The 4 - 20 laser blind holes are made by laser drilling, and the mechanical drill hole is made by aligning with the target of each layer of drill target. During the circuit exposure, the CCD camera is used to capture the combination target of the laser blind holes and the mechanical drill hole for alignment, and algorithm processing is carried out for compensatory matching.

[0025] Further, the daughter board I includes a gold finger; the preparation process of the gold finger includes the following steps:

[0026] Pull copper leads at the gold - finger plating position of the daughter board I to connect the circuits in the gold - finger area with the copper at the board edge; perform solder mask printing at the non - gold - finger position in the uncovering area of the daughter board I; perform wet - film printing or dry - film covering on the gold - finger leads, then perform dry - film pasting on the whole board surface, and after exposure and development, expose the gold - finger area; perform gold plating on the gold - finger position, after stripping the film, perform film pasting, exposure, and development on the whole board surface to expose the gold - finger leads, and etch away the gold - finger leads to obtain the gold finger;

[0027] Perform high - temperature glue pasting on the uncovering position. The high - temperature glue includes an A side and a B side. The A side of the high - temperature glue includes PI glue, and the B side includes glue components. The B side of the high - temperature glue is bonded to the gold finger.

[0028] Further, the high-temperature adhesive treatment includes: after the B side of the high-temperature adhesive is attached to the position of the gold finger, it is quickly pressed at 170-190°C for 1-3 minutes, then laser cutting is performed, and after removing the high-temperature adhesive waste, it is quickly pressed at 170-190°C for 1-3 minutes;

[0029] And / or, in the process of preparing the mother board, the controlled-depth milling includes: milling open the position of the cover removal.

[0030] Further, the high-order HDI stepped gold finger circuit board includes 10-30 layers of 3-10 order HDI stepped gold finger circuit boards.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The circuit board product prepared by the preparation method of the high-order HDI stepped gold finger circuit board of the present invention has excellent dimensional stability and overall reliability; the reliability of the multi-order laser blind vias and stacked vias is good; the alignment matching of the multi-order laser blind vias and through vias is good; the circuit board meets the requirements of the stepped gold finger. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a schematic diagram of the laser blind via of the present invention and the copper pad of its corresponding sub-outer layer.

[0035] Figure 2 It is a schematic diagram of the cumulative alignment deviation of the laser blind via of the present invention.

[0036] Figure 3 It is a schematic diagram of the short circuit between the drilled hole of the mother board of the present invention and the inner copper layer.

[0037] Figure 4 It is the alignment method during the graphic exposure of the daughter board and the mother board of the present invention.

[0038] Figure 5 It is a schematic cross-sectional structure diagram of the high-order HDI stepped gold finger circuit board of Embodiment 1 of the present invention. Detailed Embodiments

[0039] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0040] The preparation method of a high-order HDI stepped gold finger circuit board according to an embodiment of the present invention will be specifically described below.

[0041] In some embodiments of the present invention, a preparation method of a high-order HDI stepped gold finger circuit board is provided, including: sequentially preparing an inner core board, a daughter board, and a mother board;

[0042] In the process of preparing the inner core board, after inner layer inspection, baking, brownification, baking, and lamination are carried out in sequence;

[0043] In the process of preparing the daughter board, after laser drilling, plasma degumming and blind hole bottom inspection are carried out in sequence, after blind hole electroplating, blind hole inspection is carried out, after daughter board inspection, HCT test is carried out, and after brownification, baking is carried out;

[0044] In the process of preparing the mother board, after laser drilling, plasma degumming and blind hole bottom inspection are carried out in sequence, after blind hole electroplating, blind hole inspection is carried out, and after outer layer inspection, HCT test is carried out.

[0045] The circuit board prepared by the preparation method of the high-order HDI stepped gold finger circuit board of the present invention has the following advantages:

[0046] The circuit board has excellent dimensional stability and overall reliability;

[0047] The circuit board meets the reliability requirements of multi-order laser blind hole stacked holes;

[0048] The circuit board has good alignment matching of multi-order laser blind holes and through holes;

[0049] The circuit board meets the requirements of stepped gold fingers.

[0050] The insulating layer material in the high-order HDI stepped gold finger circuit board of the present invention is a high-speed material of ultra-low loss grade. The resin system of this type of material is PPO, and specific process parameters need to be matched, and the corresponding degumming method needs to be matched. Plasma degumming needs to be used for degumming after drilling, and the traditional potassium permanganate degumming is no longer applicable.

[0051] To ensure the dimensional stability of the high-order HDI stepped gold finger circuit board, in the preparation process of the inner core board, after inner layer inspection, a baking step is added. Since the copper foil is partially etched away after inner layer etching, the stress balance of the PCB (the stress of warp and weft glass fibers) is broken, and the size changes, requiring the establishment of a new stress balance. Baking can accelerate this stress release process and improve the dimensional stability of the product.

[0052] Since the selected material is a high-speed material of ultra-low loss grade (such as a material with a loss factor Df≤0.008), the PPO resin system material in it is prone to moisture absorption. In the preparation processes of the inner core board and the daughter board, baking is required after brownification before lamination to remove moisture. Baking can prevent a large amount of moisture from remaining during the high-temperature and high-pressure lamination process. If water vapor cannot be effectively discharged, it will cause problems such as lamination white spots, delamination, air bubbles and voids, and poor bonding force, resulting in a reliability risk of delamination and explosion of the product.

[0053] To ensure the reliability of multi-order blind via stacking vias, in the present invention, a blind via bottom inspection is set after each laser drilling, and the bottom of the via after plasma desmearing is inspected to ensure that there is no residual glue at the bottom of the via before proceeding to the next step. Because if there is residual glue at the bottom of the via, a blind via pad-off defect will occur, and it is very easy for the blind via copper boundary to separate during the use of the product, resulting in product failure.

[0054] To ensure the reliability of multi-order blind via stacking vias, a blind via inspection is set after filling and electroplating. If there is a large depression at the blind via, it will cause difficulties in the subsequent manufacturing processes, such as the subsequent laser drilling not being able to penetrate, or the accumulation of blind via depressions during subsequent electroplating filling.

[0055] To further ensure the reliability of multi-order stacked blind vias, an HCT test is added after each outer layer inspection. HCT is a high current impact resistance test, which is a test method for testing the reliability of blind via interconnection of HDI products. By adding this process step in each blind via manufacturing process, the reliability of HDI blind via stacking vias can be inspected.

[0056] In some embodiments of the present invention, the preparation method of the high-order HDI stepped gold finger circuit board includes: sequentially preparing an inner core board, a daughter board I, a daughter board II, a daughter board III, a daughter board IV, and a mother board;

[0057] The process of preparing the inner core board includes: sequentially performing blanking, inner layer dry film, inner layer etching, inner layer inspection, baking, brownification, baking, and lamination;

[0058] The process for preparing daughter board I includes: successively performing target drilling, laser drilling, mechanical drilling, plasma degumming, blind via bottom inspection, electroless copper plating, via filling electroplating, blind via inspection, resin plugging, ceramic grinding, daughter board dry film, acid etching, daughter board inspection, HCT testing, daughter board solder mask, daughter board wet film, daughter board dry film, daughter board development, gold finger plating, film stripping, daughter board dry film, daughter board development, lead etching, film stripping, applying high-temperature adhesive, quick pressing, laser cutting, quick pressing, brown oxidation, board baking, and lamination;

[0059] The processes for preparing daughter board II, daughter board III, and daughter board IV include: successively performing target drilling, laser drilling, drilling of board edge holes, plasma degumming, blind via bottom inspection, electroless copper plating, via filling electroplating, blind via inspection, daughter board dry film, acid etching, daughter board inspection, HCT testing, brown oxidation, board baking, and lamination;

[0060] The process for preparing the mother board includes: successively performing target drilling, laser drilling, plasma degumming, blind via bottom inspection, electroless copper plating, via filling electroplating, blind via inspection, copper reduction, target drilling, drilling, plasma degumming, electroless copper plating, electroplating, resin plugging, ceramic grinding, copper reduction, target drilling, drilling, plasma degumming, electroless copper plating, surface electroplating, outer layer dry film, outer layer development, pattern electroplating, outer layer alkaline etching, outer layer inspection, HCT testing, solder mask, characters, surface treatment, shaping, controlled-depth milling, and finished product cleaning.

[0061] In some embodiments of the present invention, the resin material of the insulating layer in the high-order HDI stepped gold finger circuit board includes PPO (epoxy polyphenylene oxide). The material of the insulating layer in the high-order HDI stepped gold finger circuit board of the present invention includes high-speed materials of ultra-low loss grade (such as materials with loss factor Df ≤ 0.008), and the resin system of this type of material is PPO, and corresponding process parameters such as lamination parameters and drilling parameters need to be matched.

[0062] In some embodiments of the present invention, before brown oxidation, the temperature of board baking is 170 - 190 °C, and the time is 2 - 4 h; typically but not restrictively, for example, before brown oxidation, the temperature of board baking can be 170 °C, 180 °C, 190 °C, or the range value between any two of them, and the time can be 2 h, 3 h, 4 h, or the range value between any two of them.

[0063] In the preparation method of the high-order HDI stepped gold finger circuit board of the present invention, baking the board at 170 - 190 °C for 2 - 4 h before brown oxidation can accelerate the stress release process and is beneficial to improving the dimensional stability of the product.

[0064] In some embodiments of the present invention, after brownification, the temperature of the baking plate is 115 - 125 °C, and the time is 30 - 60 min; typically but not restrictively, for example, after brownification, the temperature of the baking plate is 120 °C, and the time can be 30 min, 40 min, 50 min, 60 min, or any range value between any two of them.

[0065] In the method for preparing the high - order HDI stepped gold finger circuit board of the present invention, after brownification, baking the plate at 120 °C for 30 - 60 min can remove moisture, which is beneficial to the subsequent lamination.

[0066] In some embodiments of the present invention, after brownification, the residence time between baking the plate and lamination ≤ 24 h.

[0067] In order to further control the water absorption of the material, the residence time between baking the plate after brownification and lamination is controlled within 24 h to prevent the product from getting damp during long - term residence, and dehumidification treatment is carried out on materials such as prepregs.

[0068] In some embodiments of the present invention, blind - hole inspection is carried out after via - filling electroplating, so that the depression value after via - filling electroplating ≤ 10 μm.

[0069] A blind - hole inspection step is set after via - filling electroplating to ensure that the depression value after via - filling electroplating ≤ 10 μm, thereby ensuring that no large depression occurs at the blind - hole.

[0070] In some embodiments of the present invention, laser blind - holes are formed by laser drilling. The single - side ring width between the laser blind - holes and the corresponding sub - outer - layer copper pads is 2 - 3 mil, and the alignment offset between the corresponding sub - outer - layer copper pads and the laser blind - holes does not exceed the single - side ring width.

[0071] In some embodiments of the present invention, the alignment method for laser drilling is as follows: Using the board - edge positioning holes for positioning, ablating the target of the corresponding sub - outer - layer of the laser blind - holes, and using the method of grasping the sub - outer - layer target for alignment to achieve the alignment between the laser blind - holes and the corresponding sub - outer - layer copper pads.

[0072] There are difficulties in the alignment of multi - order blind - holes: Refer to Figure 1 , for the alignment between the laser blind - holes of the present invention and their corresponding sub - outer - layer copper pads, the single - side ring width between the corresponding sub - outer - layer copper pads and the laser blind - holes is 2 - 3 mil, and the alignment offset between the corresponding sub - outer - layer copper pads and the laser blind - holes does not exceed the single - side ring width. For this alignment requirement, the alignment method used for laser drilling is: Using the board - edge positioning holes for positioning, ablating the target of the corresponding sub - outer - layer of the laser blind - holes at this level, and using the method of grasping the sub - outer - layer target for alignment to achieve the alignment between the laser blind - holes and the corresponding sub - outer - layer copper pads. At the same time, the exposure of the dry film of the subsequent sub - board layer of this laser blind - hole layer is also aligned using the board - edge laser blind - holes produced by this laser drilling.

[0073] In some embodiments of the present invention, the alignment method during the pattern exposure of the daughter board and the mother board is as follows: A combined target consisting of 1 mechanical drill hole and 4 to 20 laser blind holes located around the mechanical drill hole is used for alignment. The 4 to 20 laser blind holes are made by laser drilling, and the mechanical drill hole is made by aligning with the target of each layer's drill target. During the circuit exposure, a CCD camera is used to capture the combined target of the laser blind holes and the mechanical drill hole for alignment, and algorithm processing is performed to compensate and match.

[0074] The alignment problem between laser blind holes and vias and buried vias is a common problem in multi - layer HDI. See Figure 2 and Figure 3 For multi - layer HDI, it is necessary to consider the alignment of multi - layer blind via stacking holes. If there are alignment deviations in the laser drilling of each layer, and the alignment holes used during the circuit exposure of the daughter board are only the blind holes made by laser drilling, then it is very likely that the alignment deviations of the laser blind holes accumulate in the same direction. The more layers of laser blind holes are stacked, the greater the accumulated deviation value, and it is extremely easy for the mechanical drill holes of the daughter board and the mechanical drill holes of the mother board to short - circuit with the inner - layer copper layer. To solve the above problems, for example, the alignment method during the pattern exposure of the daughter board and the mother board of the present invention is the board - edge alignment hole design as shown in Figure 4 A combined target of 18 laser blind holes on the periphery and 1 mechanical drill hole in the center is used for comprehensive alignment. The 18 laser blind holes are made by laser drilling and have a high alignment matching degree with the sub - outer layer. The central mechanical drill hole is made by aligning with the comprehensive target of each layer's drill target and has a higher alignment matching degree with the mechanical drill hole. During the circuit exposure, the CCD camera captures the laser blind holes and the mechanical drill hole, and after certain algorithm processing, it can compensatorily match between the laser blind holes and the vias and buried vias, thus alleviating the alignment deviation between the laser blind holes and the vias and buried vias.

[0075] In some embodiments of the present invention, daughter board I includes a gold finger; the preparation process of the gold finger includes the following steps:

[0076] Pull copper leads at the gold - plated finger position of daughter board I to connect the circuits in the gold - finger area to the copper on the board edge; perform solder mask printing at the non - gold - finger position in the uncovering area of daughter board I; perform wet film printing or dry film covering on the gold - finger leads, then perform dry film pasting on the entire board surface of the daughter board, and after exposure and development, expose the gold - plated finger area; perform gold - plating treatment on the gold - finger position, and after stripping the film, perform film pasting, exposure, and development on the entire board surface to expose the gold - finger leads, and etch away the gold - finger leads to obtain the gold finger;

[0077] Paste a high - temperature adhesive on the uncovering position. The high - temperature adhesive includes an A side and a B side. The A side of the high - temperature adhesive includes PI glue, and the B side includes a glue component. The B side of the high - temperature adhesive is bonded to the gold finger.

[0078] In some embodiments of the present invention, applying high temperature glue to the uncovered position includes: after attaching the B surface of the high temperature glue to the position of the gold finger, fast pressing at 170-190° C. for 1-3 minutes, then performing laser cutting, removing the high temperature glue waste, and fast pressing at 170-190° C. for 1-3 minutes;

[0079] In some embodiments of the present invention, in the process of preparing the motherboard, the controlled depth milling includes: gong-cutting the position where the cover is uncovered.

[0080] The high-end HDI ladder gold finger circuit board has a special board thickness (1.57mm±0.13mm) design for PCIe gold finger plugging and unplugging, and has ladder gold finger requirements. The ladder gold finger requires the PCB uncovering process. The difficulties encountered are: the gold finger layer is a built-in layer, and the lead electroplating gold finger production needs to be completed on the daughter board and undergo multiple pressing processes. How to ensure that the gold finger position does not overflow with glue, and how to successfully complete the uncovering. The gold finger manufacturing and uncovering process of the present invention is as follows: firstly, a copper lead is pulled at the position where the gold finger needs to be plated on the daughter board I, so that the circuit in the gold finger area is connected to the copper at the edge of the board, so that the board edge and the gold finger position are energized and gold is plated when the gold finger is electroplated; before electroplating the gold finger, solder mask screen printing is first performed at the non-gold finger position of the daughter board layer where the gold finger is located and the uncovering area is required, and the anti-plating effect is achieved after the solder mask is made, and at the same time, the gold finger lead wire needs to be printed with a wet film or covered with a dry film to prevent the lead wire from being plated with gold (the lead wire needs to be etched and removed later, and will resist corrosion after being plated with gold); finally, the daughter board is subjected to a dry film treatment on the entire board surface, and the area where the gold finger needs to be plated is exposed after exposure and development, and the gold is plated. The finger position is gold-plated, and the film is stripped after the gold plating is completed. The film stripping here includes the wet film or dry film at the lead and the dry film on the entire board. After the film is stripped, the entire board is filmed, exposed, and developed to expose the gold finger lead, and the lead is etched away to finally obtain the gold finger; after the gold finger is made, the position that needs to be uncovered is treated with high-temperature glue. The high-temperature glue can prevent glue overflow during the pressing process. Specifically, the high-temperature glue has an A side and a B side. Under high-temperature and high-pressure pressing conditions, the PI glue contained in the A side can be tightly polymerized with the resin, and the B side is partially bonded to the gold finger. However, under normal temperature conditions, the adhesion between the B side and the gold finger will be reduced, which is conducive to uncovering and tearing, forming a step shape. The high-temperature glue can prevent the resin from flowing onto the gold finger, and it can also prevent the solution of the browning process before pressing from penetrating into the gold finger area, and it can also withstand multiple pressings.

[0081] The process of high-temperature glue treatment is as follows: after the B side of the high-temperature glue is bonded to the position of the gold finger, it is placed in a fast pressing machine for fast pressing. Fast pressing can increase the adhesion between the high-temperature glue and the gold finger. Then laser cutting is performed to make the corresponding shape at the corresponding position. After removing the waste of high-temperature glue, fast pressing is performed again to ensure that the high-temperature glue and the gold finger are tightly bonded. At this point, the high-temperature glue bonding is completed.

[0082] In the motherboard manufacturing process, through the controlled-depth milling process, the position that needs to be uncovered is milled to a certain depth. The presence of this high-temperature adhesive makes it easier to uncover the cover, and finally, a stepped gold finger is formed after uncovering the cover.

[0083] In some embodiments of the present invention, the high-order HDI stepped gold finger circuit board includes a 10 - 30 layer 3 - 10 order HDI stepped gold finger circuit board.

[0084] Example 1

[0085] See Figure 5 , the 18-layer 6-order HDI stepped gold finger circuit board provided in this embodiment: includes 3 inner core boards and sub-board I made by the first lamination of 3 inner core boards, sub-board II made by the second lamination, sub-board III made by the third lamination, sub-board IV made by the fourth lamination, and the motherboard made by the fifth lamination; among them, the material of the insulating layer in the circuit board includes a material with a dissipation factor Df ≤ 0.008, and the resin system of this material is PPO;

[0086] Its manufacturing method includes: successively manufacturing the inner core board, manufacturing sub-board I, manufacturing sub-board II, manufacturing sub-board III, manufacturing sub-board IV, and manufacturing the motherboard;

[0087] The process of manufacturing the inner core board includes: successively performing blanking, inner layer dry film, inner layer etching, inner layer inspection, baking the board, brownification, baking the board, and lamination;

[0088] The specific steps include: after the inner core board is cut into the corresponding size by blanking, the film is pasted, exposed, and etched to obtain the inner layer circuit pattern. After inner layer inspection, the board is baked at 180 °C for 2 h, after brownification, the board is baked at 120 °C for 30 min, and then laminated within 24 h; in the process of manufacturing the inner core board, the prepreg is dehumidified;

[0089] The process of manufacturing sub-board I (the layer where the gold finger is located) includes: successively performing target drilling, laser drilling, mechanical drilling, plasma degumming, blind hole bottom inspection, copper deposition, hole filling electroplating, blind hole inspection, resin plugging of holes, ceramic grinding of the board, sub-board dry film, acid etching, sub-board inspection, HCT test, sub-board solder mask, sub-board wet film, sub-board dry film, sub-board development, gold plating of the finger, stripping the film, sub-board dry film, sub-board development, etching the lead, stripping the film, pasting high-temperature adhesive, fast lamination, laser cutting, fast lamination, brownification, baking the board, and lamination;

[0090] The specific steps include: after the inner core board, prepreg, and copper foil are laminated, target drilling is performed, and then laser drilling is performed to make laser blind holes and mechanical drilling is performed to make mechanical buried holes; See Figure 1For the alignment between the laser blind vias and their corresponding second-layer copper pads, the single-sided ring width between the copper pads and the laser blind vias is 2 mil, and the alignment offset between the copper pads and the laser blind vias does not exceed the single-sided ring width (2 mil); the alignment method for laser drilling is to use the positioning holes on the board edge to position, ablate the target corresponding to the second layer of the laser blind vias at this level, and adopt the method of grasping the second-layer target for alignment to achieve the alignment between the laser blind vias and the corresponding copper pads. At the same time, the exposure of the dry film of the subsequent sub-board layer of this laser blind via layer is also aligned with the laser blind vias on the board edge made by this laser drilling; Sub-board I includes laser blind vias and mechanical buried vias. When aligning during the graphic exposure of the sub-board, the combination target of 18 laser blind vias on the periphery and 1 mechanical drilling in the center is used for alignment. The 18 laser blind vias are made by laser drilling and have a high alignment matching degree with the second layer. The mechanical drilling in the center is made by aligning with the comprehensive target of the drilling target for each layer and has a higher alignment matching degree with the mechanical drilling. When the circuit is exposed, the CCD camera captures the laser blind vias and the mechanical drilling, and after certain algorithm processing, it can compensatively match between the laser blind vias and the mechanical through holes and mechanical buried vias, thus alleviating the alignment deviation between the laser blind vias and the mechanical through holes and mechanical buried vias;

[0091] After the mechanical drilling is completed, plasma degumming is carried out to clean the residual glue in the holes;

[0092] After plasma degumming, inspection of the bottom of the blind vias is carried out to check the bottom of the holes after plasma degumming. After ensuring that there is no residual glue at the bottom of the holes, the next step is carried out;

[0093] After the inspection of the bottom of the blind vias, electroless copper plating and electroplating to fill the holes are carried out in sequence to fill the laser blind vias with copper and electroplate the buried holes of the mechanical drilling with hole copper;

[0094] After electroplating to fill the holes, inspection of the blind vias is carried out to ensure that the depression value after filling and electroplating is ≤10 μm;

[0095] After the inspection of the blind vias, resin plugging of the mechanical buried vias, ceramic grinding of the board, and production of the circuit pattern of Sub-board I are carried out; Since Sub-board I is the layer where the gold fingers are located, the production of the gold fingers is also required. Therefore, gold finger electroplating leads are set on the circuit layer of Sub-board I. Specifically, copper leads are pulled at the positions where the gold fingers need to be plated on Sub-board I to connect the circuits in the gold finger area to the copper on the board edge, facilitating the energization between the clamping board edge and the gold finger position during gold finger electroplating. After laminating, exposing, developing, and etching, the circuit pattern of Sub-board I is obtained;

[0096] After the circuit pattern of Sub-board I passes the sub-board inspection, an HCT test (high current impact resistance test) is carried out;

[0097] Sub-board I is the layer where the gold finger is located. The preparation process of the gold finger includes: pulling a copper lead at the position of the sub-board I where the gold finger needs to be plated, so that the circuit in the gold finger area is connected to the copper at the edge of the board, so that the clamping board edge and the gold finger position are energized and gold is plated when the gold finger is electroplated; before electroplating the gold finger, firstly, solder mask screen printing is performed at the non-gold finger position of the sub-board layer where the gold finger needs to be uncovered, and the anti-plating effect is achieved after the solder mask is made. At the same time, the gold finger lead wire needs to be printed with a wet film or covered with a dry film to prevent the lead from being plated with gold (the lead wire needs to be etched and removed later, and will be etched and removed), and finally the sub-board is pasted with a dry film on the entire board surface, and the area where the gold finger needs to be plated is exposed after exposure and development, and the gold finger position is plated with gold. After the gold plating is completed, the film is stripped, and the film stripping here includes the wet film or dry film at the lead wire and the dry film on the entire board surface. After the film stripping, the entire board surface is filmed, exposed, and developed to expose the gold finger lead wire, and the lead wire is etched and removed to obtain the gold finger;

[0098] After the gold finger is made, the position where the cover needs to be removed is treated with high-temperature glue. The high-temperature glue includes the A side and the B side. Under the high-temperature and high-pressure lamination conditions, the PI glue contained in the A side can be tightly polymerized with the resin. The B side includes the glue component. The B side is bonded to the gold finger, but under normal temperature conditions, the adhesion between the B side and the gold finger will decrease, which is conducive to the cover being removed and formed into a step shape;

[0099] The high temperature adhesive treatment includes: after the B side of the high temperature adhesive is attached to the gold finger position, it is placed in a fast pressing machine for fast pressing (180°C, 2min), and then laser cutting is performed to make corresponding shapes at corresponding positions, and after removing the waste of high temperature adhesive, fast pressing is performed again (180°C, 2min);

[0100] Finally, browning, baking the plate at 120°C for 30 min and pressing were performed in sequence;

[0101] The process of preparing the daughter board II includes: drilling the target, laser drilling, drilling the board edge hole, plasma degumming, blind hole bottom inspection, copper deposition, hole filling electroplating, blind hole inspection, daughter board dry film, acid etching, daughter board inspection, HCT test, browning, board baking and pressing;

[0102] The specific steps include: pressing the sub-board I with the prepreg and the copper foil to obtain the sub-board II; drilling the sub-board II with the target and then drilling the laser holes and the board side holes in sequence; the purpose of drilling the board side holes is to Figure 4 The mechanical drilling holes in the alignment target shown in FIG. are drilled for alignment during exposure of the sub-plate II pattern;

[0103] Then, after the laser blind vias are treated with plasma to remove the glue, the bottom of the blind vias is inspected. After the copper deposition is completed, filling and electroplating of the vias are carried out. The inspection of the blind vias ensures that the depression value after filling and electroplating is ≤ 10 μm. Then, the pattern of Sub-board II is fabricated, specifically by laminating the film, exposing, developing, and etching to obtain the pattern circuit layer of Sub-board II. After inspection, the HCT test is carried out, followed by brownification, baking the board at 120 °C for 30 min, and lamination.

[0104] The processes for preparing Sub-board III and Sub-board IV are the same as that of Sub-board II.

[0105] The process for preparing the mother board includes: successively carrying out target drilling, laser drilling, plasma glue removal, inspection of the bottom of the blind vias, copper deposition, via filling and electroplating, inspection of the blind vias, copper reduction, target drilling, through-hole drilling, plasma glue removal, copper deposition, electroplating, resin plugging of the vias, ceramic grinding of the board surface, copper reduction, target drilling, through-hole drilling, plasma glue removal, copper deposition, surface electroplating of the board, outer dry film lamination, outer development, pattern electroplating, outer alkaline etching, outer inspection, HCT test, solder mask printing, character printing, surface treatment, shaping, controlled-depth milling, and final product cleaning.

[0106] The specific steps include: laminating Sub-board IV with prepreg and copper foil to obtain the mother board. The hole structure of the mother board has laser blind vias and mechanical through-holes (the alignment method during the pattern exposure of the mother board is the same as that of the sub-board). After target drilling of the mother board, laser drilling, plasma glue removal, inspection of the bottom of the blind vias, copper deposition, and via filling and electroplating, the inspection of the blind vias ensures that the depression value after filling and electroplating is ≤ 10 μm. After the production of the laser blind vias is completed, the mechanical through-holes are fabricated. First, the through-holes that need to be resin-plugged are drilled, plasma glue removal and copper deposition electroplating are carried out, then resin plugging of the vias and ceramic grinding of the board surface are carried out, and copper reduction is carried out to obtain the through-holes after resin plugging. Then, the through-holes that are not resin-plugged are drilled. Similarly, after target drilling, through-hole drilling, plasma glue removal, inspection of the bottom of the blind vias, copper deposition, and electroplating, the production of the outer circuit pattern is carried out, specifically by laminating the outer dry film, developing, then carrying out pattern electroplating and outer alkaline etching to obtain the outer circuit pattern. After inspection, the HCT test is carried out again, solder mask and character are fabricated, surface treatment and shaping are carried out, and then controlled-depth milling is carried out (controlled-depth milling means uncovering the position of the gold fingers and milling a certain depth at the positions that need to be uncovered). After final product cleaning, an 18-layer 6-order HDI stepped gold finger circuit board is obtained.

[0107] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or equivalently replace some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of a high-order HDI stepped gold finger circuit board, characterized in that, Including: Successively preparing an inner core board, a daughter board, and a mother board; In the process of preparing the inner core board, after inner layer inspection, baking, brownization, baking, and lamination are successively carried out; In the process of preparing the daughter board, after laser drilling, plasma desmearing and blind via bottom inspection are successively carried out, after filling via electroplating, blind via inspection is carried out, after daughter board inspection, HCT test is carried out, and after brownization, baking is carried out; In the process of preparing the mother board, after laser drilling, plasma desmearing and blind via bottom inspection are successively carried out, after filling via electroplating, blind via inspection is carried out, and after outer layer inspection, HCT test is carried out.

2. The manufacturing method of the high-order HDI stepped gold finger circuit board according to claim 1, wherein, Including: Successively preparing an inner core board, daughter board I, daughter board II, daughter board III, daughter board IV, and a mother board; The process of preparing the inner core board includes: successively carrying out blanking, inner layer dry film, inner layer etching, inner layer inspection, baking, brownization, baking, and lamination; The process of preparing daughter board I includes: successively carrying out target drilling, laser drilling, mechanical drilling, plasma desmearing, blind via bottom inspection, electroless copper plating, filling via electroplating, blind via inspection, resin plugging, ceramic grinding, daughter board dry film, acid etching, daughter board inspection, HCT test, daughter board solder mask, daughter board wet film, daughter board dry film, daughter board development, gold finger plating, stripping, daughter board dry film, daughter board development, etching leads, stripping, pasting high-temperature adhesive, quick pressing, laser cutting, quick pressing, brownization, baking, and lamination; The processes of preparing daughter board II, daughter board III, and daughter board IV include: successively carrying out target drilling, laser drilling, drilling board edge holes, plasma desmearing, blind via bottom inspection, electroless copper plating, filling via electroplating, blind via inspection, daughter board dry film, acid etching, daughter board inspection, HCT test, brownization, baking, and lamination; The process of preparing the mother board includes: successively carrying out target drilling, laser drilling, plasma desmearing, blind via bottom inspection, electroless copper plating, filling via electroplating, blind via inspection, copper reduction, target drilling, drilling, plasma desmearing, electroless copper plating, electroplating, resin plugging, ceramic grinding, copper reduction, target drilling, drilling, plasma desmearing, electroless copper plating, panel electroplating, outer layer dry film, outer layer development, pattern electroplating, outer layer alkaline etching, outer layer inspection, HCT test, solder mask, characters, surface treatment, shaping, controlled depth milling, and finished product cleaning.

3. The preparation method of the high-order HDI stepped gold finger circuit board according to claim 2, wherein, The resin material of the insulating layer in the high-order HDI stepped gold finger circuit board includes PPO.

4. The preparation method of the high-order HDI stepped gold finger circuit board according to claim 2, characterized in that, Including at least one of the following features (1) to (3); (1) Before the brownization, the temperature of the baking is 170 - 190 °C, and the time is 2 - 4 h; (2) After the brownization, the temperature of the baking is 115 - 125 °C, and the time is 30 - 60 min; (3) After the brownization, the residence time between the baking and the lamination ≤ 24 h.

5. The preparation method of the high-order HDI stepped gold finger circuit board according to claim 2, wherein, The blind via inspection is carried out after the filling via electroplating, so that the depression value after the filling via electroplating ≤ 10 μm.

6. The preparation method of the high-order HDI stepped gold finger circuit board according to claim 2, wherein, Laser blind vias are formed through the laser drilling, the single-sided ring width between the laser blind vias and the corresponding sub - outer layer copper pads is 2 - 3 mil, and the alignment offset between the corresponding sub - outer layer copper pads and the laser blind vias does not exceed the single - sided ring width; And / or, the alignment method for the laser drilling is as follows: Use the positioning holes on the board edge for positioning, ablate the target corresponding to the sub-outer layer of the laser blind hole, and use the method of grasping the sub-outer layer target for alignment to achieve the alignment between the laser blind hole and the corresponding sub-outer layer copper pad.

7. The manufacturing method of the high-order HDI stepped gold finger circuit board according to claim 2, characterized in that, The alignment method during the pattern exposure of the daughter board and the mother board is as follows: Use a combination target of 1 mechanical drill hole and 4 - 20 laser blind holes located around the mechanical drill hole for alignment. The 4 - 20 laser blind holes are made by laser drilling, and the mechanical drill hole is made by aligning with the target of each layer of drill target. During the circuit exposure, use a CCD camera to capture the combination target of the laser blind hole and the mechanical drill hole for alignment, and perform algorithm processing to compensate and match.

8. The preparation method of the high-order HDI stepped gold finger circuit board according to claim 2, characterized in that, The daughter board I includes a gold finger; the preparation process of the gold finger includes the following steps: Pull copper leads at the gold finger plating position of the daughter board I to connect the circuit in the gold finger area to the copper on the board edge; perform solder mask printing at the non-gold finger position in the cover opening area of the daughter board I; perform wet film printing or dry film covering on the gold finger leads, then perform dry film pasting on the entire board surface, and after exposure and development, expose the gold finger area; perform gold plating treatment on the gold finger position, and after stripping the film, perform film pasting, exposure, and development on the entire board surface to expose the gold finger leads, and etch away the gold finger leads to obtain the gold finger; Perform high-temperature glue pasting treatment on the cover opening position. The high-temperature glue includes an A side and a B side. The A side of the high-temperature glue includes PI glue, and the B side includes a glue component. The B side of the high-temperature glue is bonded to the gold finger.

9. The manufacturing method of the high-order HDI stepped gold finger circuit board according to claim 8, wherein, The high-temperature glue pasting treatment includes: After fitting the B side of the high-temperature glue to the gold finger position, perform fast pressing at 170 - 190 °C for 1 - 3 minutes, then perform laser cutting, remove the high-temperature glue waste, and then perform fast pressing at 170 - 190 °C for 1 - 3 minutes; And / or, in the process of preparing the mother board, the depth-controlled milling includes: routing open the cover opening position.

10. The preparation method of the high-order HDI stepped gold finger circuit board according to claim 9, characterized in that, The high-order HDI stepped gold finger circuit board includes a 10 - 30 layer 3 - 10 order HDI stepped gold finger circuit board.

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