Manufacturing method of small-PAD small-spacing blind buried hole circuit board

Abstract

The invention discloses a method for manufacturing a small-PAD small-spacing blind buried hole circuit board, which comprises the following steps of: performing resin hole plugging and filling on an electroplated buried hole layer, and then manufacturing an inner-layer circuit; copper reduction treatment is carried out after pressing, and the copper thickness range of the panel is controlled to be smaller than or equal to 10 micrometers; all blind holes of the circuit board are drilled through a laser drilling machine, the density of the blind holes is 170-2 million holes / m < 2 >, and the hole diameter is 75-100 microns; a vertical continuous electroplating process is adopted, a segmented setting current electroplating process is adopted in blind hole filling electroplating, and after blind hole filling is completed, the hole filling efficiency is larger than or equal to 95%, the hole filling depression is smaller than or equal to 8 micrometers, and the surface copper range is smaller than or equal to 10 micrometers; copper reduction treatment is carried out before the outer-layer circuit is manufactured, and the copper thickness range of a panel is controlled to be smaller than or equal to 10 microns. According to the manufacturing method of the small-PAD small-spacing blind buried hole circuit board provided by the invention, the manufacturing precision of the small-PAD small-spacing blind buried hole circuit board can be improved, and the product yield is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board manufacturing, and in particular to a method for manufacturing a circuit board with small PAD and small pitch blind buried holes. Background Art

[0002] With the rapid development of display technology, various LED display products have been widely used in monitoring and command, high-definition broadcasting, high-end cinemas, medical diagnosis, classroom teaching, advertising display, conferences and exhibitions, office display, virtual reality and other fields. The mini LED and COB series products integrate a high-density, tiny-sized LED array on a chip, which is commonly known as lamp beads. The smaller and denser the lamp beads, the clearer the display effect. Miniaturization, lightweight, intelligent, three-dimensional, high-definition and low power consumption have become the common goals pursued by consumers in the display field.

[0003] Correspondingly, the PAD of the circuit board lamp beads is also developing towards the direction of small size and small pitch. For example, the size requirement of the PAD of the mini LED and COB series boards is 100um*125um±10μm, and the spacing requirement is 60um±(10-15)μm. The conventional through-hole design of the mini LED and COB series boards cannot meet the production requirements of small-size and small-pitch lamp bead PADs, thus affecting the production yield of such display products. Therefore, the mini LED and COB series boards with high-density interconnection design with blind buried hole design came into being.

[0004] The purpose of the present invention is to provide a mini LED and COB series board production technology with a blind buried hole design to solve the problems of small PAD and small pitch HDI circuit boards PAD size, unqualified spacing and low yield. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for manufacturing a circuit board with small PAD and small pitch blind buried holes, so that the size and spacing of the PAD of the produced circuit board lamp beads meet the precision requirements of the circuit board with small PAD and small pitch blind buried holes, thereby improving the product quality and yield.

[0006] The technical solution of the present invention is as follows:

[0007] A method for manufacturing a small PAD small pitch blind buried hole circuit board, comprising the following steps:

[0008] The buried hole layer after electroplating is filled with resin, and then the inner layer circuit is made;

[0009] After pressing, copper reduction treatment is carried out to control the copper thickness of the board surface to be less than 10μm;

[0010] All blind holes of the circuit board are drilled by laser drilling machine, with a blind hole density of 1.7-2 million holes / ㎡ and a hole diameter of 75-100μm;

[0011] The blind holes are filled with electroplating using a vertical continuous electroplating process, where the blind hole filling electroplating adopts a segmented current electroplating process. After the blind hole filling is completed, the filling efficiency is ≥95%, the filling depression is ≤8um, and the surface copper extreme difference is ≤10μm;

[0012] Copper reduction treatment, after copper reduction, the copper thickness of the board surface is controlled to be ≤10um, and then the outer layer circuit is made;

[0013] After AOI, solder mask, text, molding, flying probe and electrical testing, a small PAD small pitch blind buried hole circuit board is produced.

[0014] Furthermore, the holes are polished after the resin plugging, so that there are no depressions or protrusions on the board, and there is no resin residue in the non-resin plugging area.

[0015] Furthermore, when the inner layer circuit is produced, an LDI exposure machine is used, the exposure scale is controlled at 6 full and 7 residual, and the etching speed is 4.0-4.2m / min.

[0016] Furthermore, when the outer layer circuit is produced, an LDI exposure machine is used, and the exposure scale is controlled at 5 full and 6 residual.

[0017] Furthermore, the current electroplating process is set in sections as follows:

[0018] There are 15 copper cylinders used for filling hole plating cylinders, among which the plating parameters of 1-5 plating cylinders are set to 5ASF, and the jet fan frequency is 15Hz, the plating parameters of 6-9 plating cylinders are set to 10ASF, and the jet fan frequency is 20Hz, the plating parameters of 10-13 plating cylinders are set to 12ASF, and the jet fan frequency is 25Hz, and the plating parameters of 14-15 plating cylinders are set to 15ASF, and the jet fan frequency is 35Hz.

[0019] Furthermore, the electrical test adopts an 8x dense step test process.

[0020] Compared with the prior art, the method for manufacturing a circuit board with small PAD and small pitch blind buried vias provided by the present invention has the following beneficial effects:

[0021] 1. The manufacturing method of the circuit board with small PAD and small pitch blind buried holes provided by the present invention, designs buried holes in the circuit board, which can not only improve the efficiency and stability of power transmission, especially the display panel similar to high-density lamp beads, but also reduce the thermal resistance of the circuit board; a laser drill is used to drill all the blind holes of the circuit board, the blind hole density is 1.7-2 million holes / ㎡, and the aperture is 75-100μm. After the blind holes are filled with electroplating, micropores and dense interconnection can be achieved, the lamp bead PAD is denser, and the display effect is clearer; the hole filling electroplating process adopts a segmented current electroplating process to improve the uniformity of electroplating, so that the hole filling efficiency is ≥95%, the hole filling depression is ≤8um, and the surface copper range is ≤10μm, which can achieve the communication effect of blind hole electroplating and obtain stable quality; after the hole filling electroplating, a copper reduction process is added to control the copper thickness range of the board surface to be ≤10μm, so as to achieve the etched PAD size tolerance and small pitch tolerance to meet user needs. Therefore, the circuit board manufacturing method of the present invention controls a series of parameters to make the circuit board lamp bead PAD small in size and dense in spacing, and controls the electroplating copper thickness and copper thickness uniformity, so that the accuracy of the small PAD and small spacing blind buried hole circuit board meets the requirements, thereby improving product quality.

[0022] 2. The manufacturing method of the small PAD small pitch blind buried hole circuit board provided by the present invention adopts an 8 times dense step test process for electrical testing to realize the electrical function test of the small pitch (2mil) Mini LED HDI board, thereby improving the product yield. DETAILED DESCRIPTION

[0023] In order 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 objects, features and advantages of the present invention more obvious and understandable, the specific implementation modes of the present invention are further described below.

[0024] It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as there is no conflict between them.

[0025] A method for manufacturing a small PAD small pitch blind buried hole circuit board, comprising the following steps:

[0026] Fill the buried hole layer with resin after electroplating, and polish it after resin plugging to make the board have no depressions or protrusions, and no resin residue in the non-resin plugging area;

[0027] For inner layer circuit production, LDI exposure machine is used, the exposure scale is controlled at 6 full and 7 residual, and the etching speed is 4.0-4.2m / min;

[0028] After browning and lamination, copper reduction treatment is carried out to control the copper thickness of the board surface to be less than 10μm;

[0029] All blind holes of the circuit board are drilled by laser drilling machine, with a blind hole density of 1.7-2 million holes / ㎡ and a hole diameter of 75-100μm;

[0030] The blind holes are electroplated and filled by using a vertical continuous hole filling electroplating process, wherein the blind hole electroplating and filling adopts a segmented current electroplating process, and after the blind hole filling is completed, the hole filling efficiency is ≥95%, the hole filling depression is ≤8um, and the surface copper extreme difference is ≤10μm; wherein the segmented current electroplating process is:

[0031] There are 15 copper cylinders used for filling hole plating cylinders, among which the plating parameters of 1-5 plating cylinders are set to 5ASF, and the jet fan frequency is 15Hz, the plating parameters of 6-9 plating cylinders are set to 10ASF, and the jet fan frequency is 20Hz, the plating parameters of 10-13 plating cylinders are set to 12ASF, and the jet fan frequency is 25Hz, and the plating parameters of 14-15 plating cylinders are set to 15ASF, and the jet fan frequency is 35Hz.

[0032] The outer layer circuit is first subjected to copper reduction treatment, and the copper thickness of the board surface is controlled to be less than 10μm after copper reduction; when the outer layer circuit is produced, an LDI exposure machine is used, and the exposure scale is controlled at 5 full and 6 residual;

[0033] After AOI, solder mask, text, molding, flying probe and electrical testing, a small PAD small pitch blind buried hole circuit board is produced; the electrical test adopts 8 times dense step test process.

[0034] The preparation method of the present invention is described in detail below through specific examples.

[0035] A method for manufacturing a small PAD small pitch blind buried hole circuit board, the specific manufacturing process is as follows:

[0036] Cutting and baking: The baking temperature is 165℃ and the baking time is 150min;

[0037] Inner layer buried hole drilling: 0.25mm buried hole, gong cutter speed 120Krpm, feed speed 1.2m / min, life 900mm;

[0038] Inner layer electroplating: VCP electroplating process, hole copper ≥15um, surface copper ≥35um; line speed is 2.25m / min, copper plating parameter is 11ASF, electroplating is carried out twice, one time for the clamping point facing up and one time for the clamping point facing down;

[0039] Resin plugging: The plugging degree is 100%. After the resin plugging, the board is polished to have no depressions or protrusions, and there is no resin residue in the non-resin plugging area. The copper after polishing is ≥35μm;

[0040] Inner layer circuit production: LDI exposure machine is used, the exposure scale is controlled at 6 full and 7 residual, the etching speed is 4.1m / min, and the upper pressure is 2.5Kg / cm 2 , down pressure 2.3Kg / cm 2 ;

[0041] Pressing: heating rate 1.62℃ / min;

[0042] Copper reduction: Browning line 2.5m / min, 3 times, average copper thickness is 8.69μm;

[0043] Laser drilling blind holes: The blind hole density is 1.8 million holes / ㎡, the hole diameter is 100μm, and the roundness of the hole is 93.8% after testing;

[0044] Filling hole electroplating: vertical continuous electroplating process is adopted to fill the blind hole with electroplating, wherein the blind hole filling electroplating adopts segmented current electroplating process, after the blind hole filling is completed, the filling efficiency is ≥95%, the filling depression is ≤8um, and the surface copper extreme difference is ≤10μm; wherein, the segmented current electroplating process is:

[0045] There are 15 copper cylinders used for filling hole plating cylinders, among which the plating parameters of 1-5 plating cylinders are set to 5ASF, and the jet fan frequency is 15Hz, the plating parameters of 6-9 plating cylinders are set to 10ASF, and the jet fan frequency is 20Hz, the plating parameters of 10-13 plating cylinders are set to 12ASF, and the jet fan frequency is 25Hz, and the plating parameters of 14-15 plating cylinders are set to 15ASF, and the jet fan frequency is 35Hz.

[0046] Copper reduction treatment reduces the surface copper thickness to 19-23μm, and controls the board surface copper thickness range to ≤10μm;

[0047] Outer circuit production: LDI exposure machine is used, the exposure scale is controlled at 5 full and 6 residual, the etching speed is 5.0m / min, and the upper pressure is 2.5Kg / cm 2 , down pressure 2.3Kg / cm 2 , so that the etching uniformity reaches more than 90%;

[0048] AOI;

[0049] Solder mask: The viscosity of the opening oil is 110-130dpa.s, the screen printing uses a 43T mesh, the pre-baking condition is 75℃ for 45-50min, the LDI exposure machine is used, the exposure scale is controlled at 6 full and 7 residual, and the developing speed is 5.5-6min;

[0050] After text, molding, flying probe and electrical testing, a small PAD small pitch blind buried hole circuit board, also known as Mini LED HDI circuit board, is produced. Among them, the electrical test adopts an 8x dense step test process.

[0051] The circuit board manufacturing method of the present invention controls a series of parameters so that the precision of the produced small PAD small pitch blind buried hole circuit board meets the requirements, thereby improving the product quality.

[0052] The embodiments of the present invention are 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 are still within the protection scope of the present invention.

Claims

1. A method for manufacturing a small PAD small pitch blind buried hole circuit board, characterized in that: The steps include: The buried hole layer after electroplating is filled with resin, and then the inner layer circuit is made; After pressing, copper reduction treatment is carried out to control the copper thickness of the board surface to be less than 10μm; All blind holes of the circuit board are drilled by laser drilling machine, with a blind hole density of 1.7-2 million holes / ㎡ and a hole diameter of 75-100μm; The blind holes are filled with electroplating using a vertical continuous electroplating process, where the blind hole filling electroplating adopts a segmented current electroplating process. After the blind hole filling is completed, the filling efficiency is ≥95%, the filling depression is ≤8um, and the surface copper extreme difference is ≤10μm; Copper reduction treatment, after copper reduction, the copper thickness of the board surface is controlled to be ≤10um, and then the outer layer circuit is made; After AOI, solder mask, text, molding, flying probe and electrical testing, a small PAD small pitch blind buried hole circuit board is produced.

2. The method for manufacturing a small PAD small pitch blind buried via circuit board according to claim 1, characterized in that: After the resin plugging holes, the board is polished to ensure that there are no depressions or protrusions, and there is no resin residue in the non-resin plugging area.

3. The method for manufacturing a small PAD small pitch blind buried via circuit board according to claim 1, characterized in that: When making the inner layer circuit, an LDI exposure machine is used, the exposure scale is controlled at 6 full and 7 residual, and the etching speed is 4.0-4.2m / min.

4. The method for manufacturing a small PAD small pitch blind buried via circuit board according to claim 1, characterized in that: When making the outer layer circuit, an LDI exposure machine is used, and the exposure scale is controlled at 5 full and 6 residual.

5. The method for manufacturing a small PAD small pitch blind buried via circuit board according to claim 1, characterized in that: The segmented current electroplating process is: There are 15 copper cylinders used for filling hole plating cylinders, among which the plating parameters of 1-5 plating cylinders are set to 5ASF, and the jet fan frequency is 15Hz, the plating parameters of 6-9 plating cylinders are set to 10ASF, and the jet fan frequency is 20Hz, the plating parameters of 10-13 plating cylinders are set to 12ASF, and the jet fan frequency is 25Hz, and the plating parameters of 14-15 plating cylinders are set to 15ASF, and the jet fan frequency is 35Hz.

6. The method for manufacturing a small PAD small pitch blind buried via circuit board according to claim 1, characterized in that: The electrical test adopts 8 times dense step test process.