A method for manufacturing a second-order HDI circuit board

Abstract

This invention discloses a method for manufacturing a second-order HDI circuit board, comprising the following steps: drilling multiple target holes on the edge of a core board; using the target holes as alignment targets to laser-drill blind vias on the core board; fabricating the inner layer circuitry of the core board, wherein a butterfly-shaped target pattern is designed at each of the four corners of the core board edge during the inner layer pattern fabrication; then etching the butterfly-shaped target pattern and the circuit pattern to form butterfly PADs, each butterfly PAD having four square PADs; laminating the outer layer; automatically detecting the butterfly PADs on the edge of the inner core board using an X-ray inspection device of a laser drilling machine, and laser-drilling the positions of the corresponding butterfly PADs on the outer layer board; then using the butterfly PADs as alignment targets to laser-drill all blind vias on the circuit board; electroplating to fill the blind vias; and fabricating the outer layer circuitry. The method for manufacturing a second-order HDI circuit board provided by this invention solves problems in HDI circuit board production such as via misalignment caused by expansion and contraction, and voids in the electroplated blind vias caused by poor blind via shape during laser drilling.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, and specifically to a method for manufacturing a second-order HDI circuit board. Background Technology

[0002] As electronic products become thinner and smaller, higher density is required for printed circuit boards. HDI (High Density Interconnect) circuit boards achieve smaller apertures, finer line widths, and fewer vias, saving PCB wiring area, significantly increasing component density, and offering advantages such as improved radio frequency interference, electromagnetic interference, and electrostatic discharge.

[0003] Traditional 1st-order HDI boards are relatively thick due to limitations in board thickness and blind via fabrication, resulting in relatively small pre-expansion / contraction data during lamination. Because only one laser-cut blind via is performed, there is no issue of overlapping vias. The diameter of the laser-cut blind via is typically 3.5-4.5 mil, and the blind vias are filled relatively fully, resulting in fewer quality problems caused by expansion / contraction and voids in the blind vias.

[0004] As HDI boards continue to increase in order of second order and above, and as the processing steps of the outermost layer become more repetitive, quality problems arise from processes such as expansion and contraction of HDI boards, fullness of electroplating and filling of holes, and laser hole type of blind holes. How to solve these problems has been a major challenge for HDI board manufacturers for a long time.

[0005] Therefore, the purpose of this invention is to provide a method for manufacturing a second-order HDI circuit board to solve the above-mentioned technical problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for manufacturing a second-order HDI circuit board, which solves the problems of stacked hole misalignment caused by expansion and contraction and electroplating voids caused by poor hole shape of laser-drilled blind holes in the production of HDI circuit boards.

[0007] The technical solution of the present invention is as follows:

[0008] A method for manufacturing a second-order HDI circuit board includes the following steps:

[0009] Step S1: Drill multiple target holes on the edge of the core board, and use the target holes as alignment targets to laser blind holes on the core board;

[0010] Step S2, inner layer circuit fabrication of the core board. When fabricating the inner layer pattern, a butterfly-shaped target pattern is designed on each of the four corners of the core board edge. Then, the butterfly-shaped target pattern and the circuit pattern are etched to form a butterfly PAD. The butterfly PAD has four square PADs.

[0011] Step S3, outer layer lamination;

[0012] Step S4: The butterfly PAD on the edge of the inner core board is automatically detected by the X-RAY inspection equipment of the laser drilling machine, and the position of the corresponding butterfly PAD on the outer board is laser-etched using a laser. Then, the butterfly PAD is used as a positioning target to laser-etch out all the blind holes of the circuit board.

[0013] Step S5: Electroplating to fill blind holes;

[0014] Step S6: Outer layer circuit fabrication.

[0015] Furthermore, in step S4, the blind hole electroplating filling process uses a high-copper, low-acid solution, which includes the following components:

[0016] Copper sulfate pentahydrate 100-280 g / L, sulfuric acid 10-200 g / L, chloride ion 20-100 mg / L, brightener 5-10 mg / L, leveling agent 5-8 mg / L, carrier agent 15-20 mg / L.

[0017] Furthermore, in step S4, the blind hole electroplating filling process adopts a segmented current electroplating process.

[0018] Furthermore, the segmented current electroplating process is as follows:

[0019] The filling electroplating tanks used consist of 15 copper tanks. The electroplating parameters for tanks 1-5 are set to 5 ASF, for tanks 6-9 to 10 ASF, for tanks 10-13 to 12 ASF, and for tanks 14-15 to 15 ASF.

[0020] Furthermore, in step S3, the laser blind hole is formed using three passes: the first pass opens the copper window, the second pass penetrates the dielectric layer, and the third pass repairs the suspended copper and the hole wall.

[0021] Furthermore, it also includes a browning and copper reduction process for the core board and the outer laminate, with the copper thickness controlled at 3-6µm.

[0022] Compared with the prior art, the method for manufacturing a second-order HDI circuit board provided by the present invention has the following advantages:

[0023] I. The method for manufacturing a second-order HDI circuit board provided by this invention involves designing a butterfly-shaped target pattern at each of the four corners of the core board during the inner layer circuit fabrication. Then, the butterfly-shaped target pattern and the circuit pattern are etched together to form a butterfly PAD, which has four square PADs. After the outer layer circuit board is laminated, all blind vias of the circuit board are laser-etched using the butterfly PADs as alignment targets. In this invention, the blind vias of the outer layer circuit board use the butterfly PADs on the core board as alignment targets; that is, each alignment target consists of four small square targets, which is more accurate than traditional round targets and solves the problem of via misalignment caused by expansion and contraction in the prior art.

[0024] II. The method for manufacturing a second-order HDI circuit board provided by the present invention uses three guns when laser drilling blind holes. The first gun opens the copper window, the second gun penetrates the dielectric layer, and the third gun repairs the suspended copper and hole walls. After the blind holes are manufactured, the hole shape is more regular and the flatness after filling is good. This effectively solves the problem of poor hole shape in laser drilling blind holes in the prior art, which leads to voids in the electroplating filling of blind holes.

[0025] Third, the method for manufacturing a second-order HDI circuit board provided by this invention employs a high-copper, low-acid solution system for blind via electroplating and filling, combined with a segmented current electroplating process to ensure full filling of the blind vias. After filling, there are no depressions or voids, and the filling efficiency is significantly improved. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the butterfly PAD in the manufacturing method of the second-order HDI circuit board of the present invention;

[0028] Figure 2 This is a schematic diagram of the blind hole electroplating filling process after the fabrication method of the second-order HDI circuit board of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below.

[0030] It should be noted that the descriptions of these embodiments are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] A method for manufacturing a second-order HDI circuit board includes the following steps:

[0032] Step S1: Drill multiple target holes on the edge of the core board, and use the target holes as alignment targets to laser blind holes on the core board.

[0033] Specifically, there are 4-6 target holes, which are drilled mechanically.

[0034] Step S2, inner layer circuit fabrication of the core board. When fabricating the inner layer pattern, a butterfly-shaped target pattern is designed on each of the four corners of the core board edge. Then, the butterfly-shaped target pattern and the circuit pattern are etched to form a butterfly PAD. The butterfly PAD has four square PADs.

[0035] The inner layer circuit fabrication process involves determining the pre-expansion / shrinkage data of the inner layer circuit based on the material characteristics of the core board, creating the inner layer film according to the pre-expansion / shrinkage, and then etching out the inner layer circuit pattern. Before the inner layer circuit fabrication, a copper reduction process is also included, in which the copper thickness is controlled at 3-6µm.

[0036] The butterfly-shaped pads at the four corners of the core board serve as positioning targets in subsequent processes. Because each butterfly pad has four square pads—meaning each alignment target consists of four small square targets—alignment is more precise than with traditional round targets. The shape of the butterfly pad is as follows: Figure 1 As shown.

[0037] Step S3, outer layer lamination;

[0038] Step S4: The butterfly PAD on the edge of the inner core board is automatically detected by the X-RAY inspection equipment of the laser drilling machine, and the position of the corresponding butterfly PAD on the outer board is laser-etched using a laser. Then, the butterfly PAD is used as a positioning target to laser-etch out all the blind holes of the circuit board.

[0039] In this invention, laser-drilled blind vias employ a three-shot method. The first shot creates a copper window, the second shot penetrates the dielectric layer, and the third shot repairs the suspended copper and the via walls. Laser-drilled blind vias use a laser beam as energy to create blind vias on a circuit board. The first shot penetrates the surface copper to create a copper window, and the second shot penetrates the dielectric layer to the thickness of the bottom copper layer. Due to light reflection, the irregular laser beam can ablate parts of the dielectric layer and surface copper, resulting in rough via walls and suspended copper. This leads to quality problems during electroplating, such as incomplete copper plating, voids, incomplete filling, and residual adhesive at the bottom of the blind via. Therefore, a third shot is added to repair the suspended copper and the via walls, resulting in a more regular via shape and better flatness after filling. This effectively solves the problem of voids in electroplating caused by poor via shape in existing laser-drilled blind vias.

[0040] In this invention, after the outer layer is laminated, a browning copper reduction process is performed before laser blind via fabrication. The copper thickness during the browning copper reduction process is controlled at 3-6µm. Browning can change the color and appearance of the circuit board, giving it a brown or similar color tone, and controlling the copper thickness to 3-6µm results in a more uniform copper thickness.

[0041] Step S5: Electroplating to fill blind holes;

[0042] Specifically, the blind hole electroplating filling process uses a high-copper, low-acid solution, which includes the following components:

[0043] The solution comprises: copper sulfate pentahydrate 100–280 g / L, sulfuric acid 10–200 g / L, chloride ions 20–100 mg / L, brightener 5–10 mg / L, leveling agent 5–8 mg / L, and carrier agent 15–20 mg / L. Preferably, the high-copper, low-acid solution comprises: copper sulfate pentahydrate 200 g / L, sulfuric acid 80 g / L, chloride ions 50 mg / L, brightener 10 mg / L, leveling agent 8 mg / L, and carrier agent 15 mg / L.

[0044] Furthermore, a segmented current plating process is employed to ensure full filling of blind vias. The segmented current plating process in this invention is as follows:

[0045] The filling electroplating tanks used consist of 15 copper tanks. The electroplating parameters for tanks 1-5 are set to 5 ASF, for tanks 6-9 to 10 ASF, for tanks 10-13 to 12 ASF, and for tanks 14-15 to 15 ASF.

[0046] Step S5: Outer layer circuitry is fabricated, followed by processes such as AOI → solder mask → selective gold plating → text → milling → electrical testing → OSP → final inspection to obtain a second-order HDI circuit board.

[0047] The circuit board manufacturing process of this invention results in no depressions or voids after blind via electroplating filling, and improves filling efficiency. A schematic diagram of the blind via electroplating filling process is shown below. Figure 2 As shown, from Figure 2 It can be seen that there is no misalignment after the blind vias are stacked. Testing showed that the filling efficiency of each layer of blind vias was greater than 96%, the blind via shape was qualified, and there were no voids in the filling. The circuit board underwent thermal stress testing at 288℃ for 10 seconds three times without any cracking of the blind vias.

[0048] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for manufacturing a second-order HDI circuit board, characterized in that, Includes the following steps: Step S1: Drill multiple target holes on the edge of the core board, and use the target holes as alignment targets to laser blind holes on the core board; Step S2, inner layer circuit fabrication of the core board. When fabricating the inner layer pattern, a butterfly-shaped target pattern is designed on each of the four corners of the core board edge. Then, the butterfly-shaped target pattern and the circuit pattern are etched to form a butterfly PAD. The butterfly PAD has four square PADs. Step S3, outer layer lamination; Step S4: Using the X-RAY inspection equipment of the laser drilling machine, the butterfly PAD on the edge of the inner core board is automatically detected, and the corresponding position of the butterfly PAD on the outer board is laser-etched. Then, using the butterfly PAD as a positioning target, all blind holes of the circuit board are laser-etched. The laser-etching of blind holes uses three shots: the first shot opens the copper window, the second shot penetrates the dielectric layer, and the third shot repairs the suspended copper and hole wall. Step S5, blind hole electroplating filling; the blind hole electroplating filling process uses a high copper low acid solution, which includes the following components: copper sulfate pentahydrate 200g / L, sulfuric acid 80g / L, chloride ion 50mg / L, brightener 10 mg / L, leveling agent 8 mg / L, carrier agent 15mg / L. The blind hole electroplating filling process adopts a segmented current electroplating process, which is as follows: The filling electroplating tanks used consist of 15 copper tanks, with the electroplating parameters set to 5 ASF for tanks 1-5, 10 ASF for tanks 6-9, 12 ASF for tanks 10-13, and 15 ASF for tanks 14-15. Step S6: Outer layer circuit fabrication.

2. The method of claim 1, wherein It also includes a browning and copper reduction process for the core board and the outer laminate, with the copper thickness controlled at 3-6µm.

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