A production process for ultra-thick copper HDI board

Abstract

A manufacturing process for ultra-thick copper HDI boards, which adopts a new three-time electroplating process, not only ensures the thick copper requirements of HDI, but also avoids the problems of uneven steps, high and low copper plating of blind holes, and depressions at the blind hole openings during electroplating; that is, the copper thickness of the board surface is increased without affecting the copper thickness in the mechanical through hole, avoiding the simultaneous electroplating of copper in the laser blind hole and the mechanical through hole, and taking into account the flatness of the blind hole filling and avoiding the problem of thin copper plating in the mechanical through hole; through the area size of each layer of copper blocks in the large panel, the difference in the residual copper rate of each layer is controlled within 15%, avoiding the warping problem of thick copper boards; adding the design of "graphic copper block + residual copper rate" in the large panel avoids the problem of wrinkling due to lack of glue in the open area when the thick copper boards are pressed together and the warping problem of the finished board. The "square corner" compensation method of the pad avoids the distortion problem of the square pad after etching the thick copper board. It is highly practical and has a strong promotion significance.

Description

Technical Field

[0001] The invention relates to the technical field of circuit boards, and in particular to a manufacturing process of an ultra-thick copper HDI board. Background Art

[0002] With the rapid development of science and technology, the industry has more and more requirements for the electrical performance of various electronic products and the density of electronic products, and its main PCB has gradually become HDI design. In order to meet the needs of heat dissipation and high current for long-term use of electronic products, the copper thickness of PCB boards is required to be higher and higher (generally the copper thickness is required to be around 100μm). Therefore, thick copper HDI design of PCB boards has gradually become a new direction, especially for PCBs used in batteries, automobiles, etc.

[0003] The manufacturing process of traditional HDI boards must take into account both the copper of mechanically drilled through holes and the copper filling of blind holes. Therefore, thin copper plating is tried as much as possible (copper thickness is about 20μm). If thicker copper HDI is to be produced (copper thickness is about 100μm), the copper thickness can only be increased by long-term copper electroplating or thick base copper can be used for production, but these methods all have quality defects to varying degrees.

[0004] If normal thin base copper (1 / 4OZ, 1 / 3OZ, etc.) is used to make blind holes, copper plating is used for a long time to thicken the holes. The process is: laser drilling blind holes → mechanical drilling → electroplating copper. This method has the disadvantages of long copper plating time and poor uniformity of copper thickness on the board surface, which will cause great hidden dangers to the quality of circuit graphics made in the subsequent process;

[0005] If thick base copper (1OZ, 2OZ, etc.) is used to make blind holes, the copper is too thick to be directly laser-drilled. A copper window larger than the blind hole diameter must be opened at the blind hole position, and then the blind hole is laser-drilled, followed by electroplating. The process is: open copper window → laser drill blind hole → mechanical drilling → electroplating copper. This method does not require long-term electroplating, but due to the opening of the copper window, there are "steps" and unevenness at the blind hole (such as Figure 1 The problem of "cold soldering" is particularly prone to occur when there are blind holes at the BGA position. Summary of the invention

[0006] Therefore, in view of the deficiencies in the prior art, the present invention aims to provide a process for manufacturing an ultra-thick copper HDI board.

[0007] A process for manufacturing an ultra-thick copper HDI board comprises the following steps:

[0008] Step 1: Direct copper plating after laser blind hole;

[0009] Provide a normal thin base copper, make blind holes on the thin substrate; then electroplate copper to fill the blind holes;

[0010] Step 2: Secondary copper electroplating:

[0011] After the base copper blind hole is filled in step 1, the copper is electroplated again to thicken the hole;

[0012] Step 3: Direct copper plating after mechanical drilling:

[0013] Mechanical drilling is performed on the product after secondary electroplating in step 2, and copper electroplating is performed after mechanical drilling, at which time the blind holes have been filled;

[0014] Step 4: Thick copper filling and lamination:

[0015] The layers to be laminated are laminated with PP with high adhesive content, and several small copper squares are laid in the area outside the delivery unit Set of the large panel. The small copper squares are distributed in a grid. At the same time, the residual copper rate of each layer is adjusted by the size of the copper-laying area between the large panel and the Set, so that the difference in the residual copper rate of each layer is controlled within 15%;

[0016] Step 5: Pad production

[0017] When etching circuits, over-etching is prone to occur. When making pads, a compensation of 25 to 30 um is made on the basis of the required size to make up for the etching difference and ensure that the final pad size is consistent with the original design. In addition, for square pads, the side length at the right angles of the pads is increased to compensate for the small square pads.

[0018] Furthermore, the HDI is a multi-stage HDI board, which includes the following processing flow: inner layer primary circuit → primary pressing → (laser drilling blind hole → electroplating copper to fill blind hole → secondary electroplating copper → mechanical drilling → electroplating copper) → inner layer secondary circuit → secondary pressing → (laser drilling blind hole → electroplating copper to fill blind hole → secondary electroplating copper → mechanical drilling → electroplating copper) → outer layer circuit three pressing.

[0019] Further, in step 1, after electroplating, the copper thickness is 16-25 μm; in step 2, after secondary electroplating, the copper thickness is 60-70 μm; in step 3, after electroplating, the copper thickness is 95-105 μm.

[0020] In summary, the present invention improves the traditional ultra-thick copper HDI manufacturing process method and adopts a new three-time electroplating process, namely: using normal thin base copper, the blind hole does not need to add copper reduction, copper window opening and other process flows, which not only ensures the thick copper requirement of HDI, but also avoids the problem of uneven steps formed at the blind hole mouth during electroplating; after normal laser drilling of the blind hole, thickened copper is used to fill the hole, the blind hole has good flatness, and the problems of high and low difference and depression of copper plating of the blind hole are avoided; after the blind hole is filled, thickened copper is electroplated again, which increases the copper thickness of the board surface without affecting the copper thickness in the mechanical through hole, and can be independently adjusted according to the demand for copper thickness. Adjust the electroplating parameters; copper electroplating is performed after mechanical drilling. The electroplating parameters can be adjusted independently according to the copper plating requirements of the mechanically drilled through holes without affecting the filling effect of the blind holes, avoiding the simultaneous electroplating of laser blind holes and mechanical through holes. In order to take into account the flatness of the blind hole filling, the copper plating in the mechanical through holes is too thin; through the area size of each layer of copper blocks in the large panel, the difference in the residual copper rate of each layer is controlled within 15%, avoiding the warping problem of thick copper plates; by adding the "graphic copper block + residual copper rate" design in the large panel, the problem of wrinkling due to lack of glue and warping of the finished board in the open area when the thick copper plates are pressed together is avoided. By designing the "square corner" compensation method of the pad, the distortion problem of the square pad after etching the thick copper plate is avoided. The invention is highly practical and has a strong promotional significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of a manufacturing process of an ultra-thick copper HDI board of the present invention;

[0022] Figure 2 for Figure 1 A schematic diagram of the structure of the rotating bracket;

[0023] Figure 3 for Figure 1 Schematic diagram of the structure of the tinning tank.

[0024] Serial number name:

[0025] 10, electroplated copper 20, base copper 30, blind hole 40, copper surface height difference after blind hole copper plating 50, large panel 60, unit set 70, small square copper 80, square pad 90, small square pad DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0027] The present invention provides a process for manufacturing an ultra-thick copper HDI board, which specifically comprises the following steps:

[0028] Step 1: Direct copper plating after laser blind hole 30;

[0029] A normal thin base copper 20 (generally with a thickness of 10 to 13 μm) is provided, and a blind hole 30 is made on a thin substrate 10. In this embodiment, the blind hole is drilled by laser. After the blind hole 30 is laser drilled, copper is electroplated to fill the blind hole 30. After the electroplating is completed, the copper thickness is 16 to 25 μm. After the hole is filled, the blind hole 30 has a good flatness, avoiding the problem of the blind hole 30 being sunken. The setting of the thin base copper 10 can overcome the influence of the thick base copper, without adding the process of opening the copper window, thereby avoiding the problem of the "step" of the blind hole opening.

[0030] Step 2: Secondary copper electroplating:

[0031] After the base copper 10 blind hole is filled in step 1, the copper is electroplated again to thicken the copper. After the second electroplating, the copper thickness is 60-70 μm, which increases the copper thickness of the board surface. At this time, since no mechanical drilling is done, the copper thickness in the mechanical through hole is not affected. In addition, the electroplating copper parameters can be independently adjusted according to the different requirements of copper thickness to meet the requirements of various copper thicknesses.

[0032] Step 3: Direct copper plating after mechanical drilling:

[0033] The product after the secondary electroplating in step 2 is mechanically drilled, and copper is electroplated after mechanical drilling. After completion, the copper thickness is 95-105μm, and the blind hole has been filled and the surface is flat. The electroplating parameters can also be adjusted independently according to the copper thickness requirements for the mechanically drilled through holes. For example: the existing thick copper HDI requirements are 95-105μm, and the electroplating time is about 50 minutes. If the thick copper is required to be 120μm, the electroplating time can be increased to 60 minutes without affecting the filling effect of the blind hole, avoiding the simultaneous electroplating of copper for laser blind holes and mechanical through holes. In order to take into account the flatness of the blind hole filling, the copper plating in the mechanical through hole is thin and uneven.

[0034] Step 4: Thick copper filling and lamination:

[0035] For multi-level HDI boards, the main processing flow is: inner layer primary circuit → primary lamination → (laser drilling blind hole → electroplating copper to fill blind hole → secondary electroplating copper → mechanical drilling → electroplating copper) → inner layer secondary circuit → secondary lamination → (laser drilling blind hole → electroplating copper to fill blind hole → secondary electroplating copper → mechanical drilling → electroplating copper) → outer layer circuit.....;

[0036] Since multi-level HDI boards need to be pressed multiple times, and the circuit copper thickness is too thick, a single PP glue filling will easily cause glue shortage and wrinkling in the open area. The open area refers to: the copper in a larger area of ​​the board is etched away during circuit production, forming a certain area or multiple areas. After the circuit is etched, very little copper remains on the board. Therefore, it is necessary to choose PP with a higher glue content. The 106 PP commonly used in HDI boards has a glue content of 72%. If the glue filling is not enough, it is necessary to use PP with a glue content of 75% or 78%. Secondly, in the inner layer design between the unit Set60 and the unit Set60 of the large panel Panel50, the small square copper 70 (such as Figure 2 As shown in the figure, in order to avoid insufficient glue filling in this area, in this embodiment, the small copper square 70 is added to the circuit making tool pattern when making each layer of circuit tools, and is made together with the etched circuit. The purpose of setting the small copper block is to increase the copper left on the board surface after circuit etching. When the multi-layer HDI board is pressed, the layers are bonded together by PP. In order to achieve seamless and tight connection between layers (avoiding the generation of voids, etc.), the copper-free area after circuit etching needs to be filled with glue in PP. The purpose of setting the small copper square is to increase the amount of residual copper on the board surface after circuit etching, thereby reducing the amount of glue in PP to fill these areas.

[0037] In this embodiment, the size of the small copper block 70 is 1*1mm. The 1*1mm copper block is set for grid design, that is, each 1*1mm copper block is surrounded by a 1*1mm copper-free area. The smallest milling cutter used in the HDI board when forming the milling board is 0.9mm. The 0.9mm milling cutter just passes through the 1*1mm copper-free area and will not touch the copper (it is more difficult to cut copper with a knife), so it will not affect the normal service life of the milling cutter. In addition, the 1*1mm small blocks are small in size when forming the milling board, and can better absorb dust, and will not cause quality problems such as scratches on the board surface, thereby ensuring product quality and tool life.

[0038] Furthermore, in the non-delivery area outside the unit set of the large panel, other areas can be set to lay small copper blocks 70 in addition to adding necessary tool holes and tool targets, that is, to increase the amount of copper remaining after circuit etching; at the same time, the residual copper rate of each layer is adjusted by designing the size of the copper plating area between the large panel and the unit set, so that the difference in the residual copper rate of each layer is controlled within 15%. For example, for a ten-layer board, as mentioned above, after the 1*1mm grid-shaped copper blocks are completely designed in the open area, the residual copper rate of the first layer is 90%, and the residual copper rate of the tenth layer is 70%, and the difference between the two sides is 30%, which exceeds 15%. At this time, it is necessary to reduce the amount of 1*1mm grid-shaped copper blocks in the first layer, and change it to a 2*2mm copper-free area between 1*1mm copper blocks. If it is still not enough, a 3*3mm copper-free area is used. By reducing copper blocks and increasing copper-free areas, the difference in residual copper rate can be achieved within 15%, avoiding the difference in copper thickness and traction stress on the two sides, which makes the board more prone to deformation and warping.

[0039] Step 5: Pad production

[0040] Since the copper is too thick after electroplating (usually about 100um), it is easy to over-etch when etching the circuit. For the circuit pad, when making it, it should be compensated by 25-30um on the basis of the required size to make up for the etching difference and ensure that the final pad size is consistent with the original design. For example, if a 100*300mm pad is required, the tool is pre-enlarged to 125*325mm during production, and after etching, it is made into a 100*300mm pad.

[0041] In addition, for the square pad 80, the side length of the pad is increased at the right angle to compensate for the small square pad 90 (such as Figure 3 As shown); the small square pad is designed to ensure the consistency of size, that is, the protruding position after the increase has the same size on both sides, and will not deform or distort after etching; in this embodiment, the side length of the compensating square is 5 to 7 mil; to avoid the square pad from being distorted and deformed into a circle after etching, and to avoid problems such as large green oil leakage due to side erosion at this position.

[0042] In summary, the present invention improves the traditional ultra-thick copper HDI manufacturing process method and adopts a new three-time electroplating process, namely: using normal thin base copper, the blind hole does not need to add copper reduction, copper window opening and other process flows, which not only ensures the thick copper requirement of HDI, but also avoids the problem of uneven steps formed at the blind hole mouth during electroplating; after normal laser drilling of the blind hole, thickened copper is used to fill the hole, the blind hole has good flatness, and the problems of high and low difference and depression of copper plating of the blind hole are avoided; after the blind hole is filled, thickened copper is electroplated again, which increases the copper thickness of the board surface without affecting the copper thickness in the mechanical through hole, and can be independently adjusted according to the demand for copper thickness. Adjust the electroplating parameters; copper electroplating is performed after mechanical drilling. The electroplating parameters can be adjusted independently according to the copper plating requirements of the mechanically drilled through holes without affecting the filling effect of the blind holes, avoiding the simultaneous electroplating of laser blind holes and mechanical through holes. In order to take into account the flatness of the blind hole filling, the copper plating in the mechanical through holes is too thin; through the area size of each layer of copper blocks in the large panel, the difference in the residual copper rate of each layer is controlled within 15%, avoiding the warping problem of thick copper plates; by adding the "graphic copper block + residual copper rate" design in the large panel, the problem of wrinkling due to lack of glue and warping of the finished board in the open area when the thick copper plates are pressed together is avoided. By designing the "square corner" compensation method of the pad, the distortion problem of the square pad after etching the thick copper plate is avoided. The invention is highly practical and has a strong promotional significance.

[0043] The above-described embodiment only expresses one implementation mode of the present invention, and its description is relatively specific and detailed, but it is not to be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A process for manufacturing an ultra-thick copper HDI board, characterized in that: The steps include: Step 1: Direct copper plating after laser blind hole; Provide a normal thin base copper, make blind holes on the thin substrate; then electroplate copper to fill the blind holes; Step 2: Secondary copper electroplating: After the base copper blind hole is filled in step 1, the copper is electroplated again to thicken the hole; Step 3: Direct copper plating after mechanical drilling: Mechanical drilling is performed on the product after secondary electroplating in step 2, and copper electroplating is performed after mechanical drilling, at which time the blind holes have been filled; Step 4: Thick copper filling and lamination: The layers to be laminated are laminated with PP with high adhesive content, and several small copper squares are laid in the area outside the delivery unit Set of the large panel. The small copper squares are distributed in a grid. At the same time, the residual copper rate of each layer is adjusted by the size of the copper-laying area between the large panel and the Set, so that the difference in the residual copper rate of each layer is controlled within 15%; Step 5: Pad production When etching circuits, over-etching is prone to occur. Therefore, when making pads, 25 to 30 um is compensated on the basis of the required size to make up for the etching difference and ensure that the final pad size is consistent with the original design. In addition, for square pads, the side length at the right angles of the pads is increased to compensate for the small square pads.

2. The process for manufacturing an ultra-thick copper HDI board according to claim 1, characterized in that: The HDI is a multi-stage HDI board, which includes the following processing flow: inner layer primary circuit → primary pressing → (laser drilling blind hole → electroplating copper to fill blind hole → secondary electroplating copper → mechanical drilling → electroplating copper) → inner layer secondary circuit → secondary pressing → (laser drilling blind hole → electroplating copper to fill blind hole → secondary electroplating copper → mechanical drilling → electroplating copper) → outer layer circuit three pressing.

3. The process for manufacturing an ultra-thick copper HDI board according to claim 1, characterized in that: In step one, after electroplating, the copper thickness is 16-25 μm; in step two, after secondary electroplating, the copper thickness is 60-70 μm; in step three, after electroplating, the copper thickness is 95-105 μm.

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