Manufacturing method of small-spacing lamp panel

Abstract

The invention discloses a manufacturing method of a small-spacing lamp panel. The manufacturing method comprises the following steps: pressing; drilling is conducted, specifically, through holes are mechanically drilled, and the hole diameter is 0.2-0.3 mm; copper deposition: the thickness of a hole wall copper plating layer is 0.3-0.5 [mu] m; electroplating through holes, wherein the copper thickness in the holes is greater than or equal to 18 microns; the through holes are filled with epoxy resin with the shrinkage rate smaller than 0.5%, and curing is conducted; ceramic board grinding is conducted, an aluminum oxide ceramic grinding wheel is adopted for board grinding, the resin surface in the hole is flush with the surface of the outer layer copper foil of the multi-layer circuit board, the surface roughness Ra is smaller than 0.1 micrometer, and board grinding technological parameters are as follows: the pressure is 5-8 N / cm < 2 >, the rotating speed is 200-300 rpm, and the linear speed is 1-2 m / min; secondary copper deposition: copper deposition is carried out on the surface of the hole plugging resin to form a copper plating layer, and the thickness of the copper plating layer is 0.3-0.5 [mu] m; the whole board is electroplated, and the copper thickness on the resin is larger than or equal to 12 micrometers; and manufacturing an outer-layer circuit. The manufacturing method of the small-spacing lamp panel has the advantages of being low in cost, high in yield, simple in process and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board manufacturing, and particularly to a manufacturing method for a small-pitch light board. Background Art

[0002] The traditional manufacturing process for small-pitch LED light boards uses the HDI process. Its process flow is lamination → brownification → laser blind vias → desmear (or plasma) → electroless copper plating → via filling electroplating → outer layer circuit. The blind via alignment accuracy requirement is extremely high (for a P1.25 pitch, the hole position error needs to be < 10um). However, laser drilling easily leads to poor blind via hole shape. Due to blind via electroplating control and parameter reasons, it is difficult to control the via filling efficiency. Via filling electroplating easily generates voids and depressions (generally < 5um), causing quality problems such as copper breakage at the blind via hole corners and soldering defects, affecting the product yield. In addition, there are also defects such as the high cost of the special electroplating solution for blind vias, and the traditional HDI process requires multiple laminations and laser drillings (for example, a 6-layer board needs to go through 2 laminations and 3 laser processes), and the production process is relatively complex.

[0003] In view of this, the purpose of the present invention is to provide a manufacturing method for a small-pitch light board with low cost and high yield. Summary of the Invention

[0004] The purpose of the present invention is to provide a manufacturing method for a small-pitch light board, which has the advantages of low cost, high yield, and simple process.

[0005] The technical solution of the present invention is as follows:

[0006] A manufacturing method for a small-pitch light board includes the following steps:

[0007] Lamination: Laminating single or multiple core boards that have completed the inner layer circuit manufacturing to obtain a multi-layer circuit board;

[0008] Drilling: Mechanically drill through holes with a hole diameter of 0.2 - 0.3mm;

[0009] Electroless copper plating: The thickness of the copper layer on the hole wall is 0.3 - 0.5um, and the backlight is ≥ 9.5 levels;

[0010] Through-hole electroplating: The copper thickness in the hole is ≥ 18um;

[0011] Vacuum resin plugging: Fill the through holes with an epoxy resin having a shrinkage rate < 0.5% and cure it;

[0012] Ceramic grinding: Grind the board using an alumina ceramic grinding wheel to make the surface of the resin in the hole flush with the outer copper foil surface of the multi-layer circuit board, and the surface roughness Ra < 0.1um. The grinding process parameters are: pressure 5 - 8N / cm 2 , rotation speed 200 - 300rpm, wire speed 1 - 2m / min;

[0013] Second copper deposition: Copper is deposited on the surface of the resin in the plugged holes to form a copper plating layer, and the copper plating layer covers the resin material after the vacuum resin plugging of the holes and the ceramic grinding of the board. The thickness of the copper plating layer is 0.3 - 0.5 μm.

[0014] Second electroplating: The whole board is electroplated to make the copper thickness on the resin ≥ 12 μm.

[0015] Fabrication of outer layer circuits.

[0016] Furthermore, in the vacuum resin plugging process of the holes, the resin material used includes the following components by weight percentage:

[0017] Epoxy resin 65 - 75%, silica powder 25 - 35%;

[0018] Among them, the particle size of the silica powder is 1 - 3 μm.

[0019] Furthermore, in the vacuum resin plugging process of the holes, the vacuum degree is -0.08 Mpa, and the curing conditions are curing at a temperature of 140 - 160 °C for 55 - 65 min.

[0020] Furthermore, the PAD pitch of the circuit board lamp beads is P1.0 or P1.25.

[0021] Compared with the prior art, the manufacturing method of the small-pitch lamp board provided by the present invention has the beneficial effects as follows:

[0022] First, the manufacturing method of the small-pitch lamp board provided by the present invention drills holes by means of mechanical through-hole drilling, eliminating the laser drilling process and reducing the equipment cost; at the same time, through-hole electroplating is adopted, which can save the chemical cost compared with the blind-hole electroplating in the prior art.

[0023] Second, the manufacturing method of the small-pitch lamp board provided by the present invention connects the inner layer circuit boards through through-holes, which can improve the alignment accuracy between the PAD and the hole to within 20 μm. Because vacuum resin plugging of the holes is adopted, the void ratio of the resin plugging of the holes < 0.1%. Due to the reasons of electroplating filling chemical and parameter control in the traditional blind-hole filling process, the blind-hole void ratio is generally above 0.5% and there are depressions; after the through-holes are plugged with vacuum resin and then ground with a ceramic plate, the plugged resin is flush with the copper surface of the multi-layer circuit board after lamination, and the plugging efficiency can reach more than 98%. After baking, the depression degree is generally < 2 μm, which can reduce the risk of false soldering when welding components on the circuit board. Therefore, the manufacturing method of the small-pitch lamp board provided by the present invention can significantly improve the alignment accuracy between the PAD and the hole and the flatness of the PAD surface, and reduce quality problems such as poor soldering in the downstream.

[0024] III. The manufacturing method of the small-pitch light board provided by the present invention. After testing, the offset between the lamp bead PAD and the hole position is <5um, which can meet the requirements of conduction alignment. The adhesion of the copper layer on the surface of the resin plug hole area is ≥1.2N / mm, which can meet the requirements of the industry (ASTM D3359 standard). For the manufacturing method of the small-pitch light board of the present invention, the lamp bead pitch can be extended to P1.0. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a schematic structural diagram of an embodiment of the small-pitch light board of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and make the above-mentioned objects, features, and advantages of the present invention more obvious and understandable, the following further describes the specific embodiments of the present invention.

[0028] It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, 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.

[0029] A manufacturing method of a small-pitch light board includes the following steps:

[0030] Lamination: Laminating one or more core boards that have completed the inner layer circuit manufacturing to obtain a multi-layer circuit board;

[0031] Drilling: Mechanically drilling through holes with a hole diameter of 0.2 - 0.3mm;

[0032] Copper deposition: The thickness of the copper layer on the hole wall is 0.3 - 0.5um, and the backlight is ≥9.5 levels;

[0033] Through-hole electroplating: Electroplating on the surface of the copper-deposited holes to form a first copper plating layer on the hole wall of the through holes. The thickness of the first copper plating layer is the copper thickness inside the holes, and the copper thickness inside the holes is ≥18um;

[0034] Vacuum resin plugging: Filling the through holes with an epoxy resin having a shrinkage rate <0.5% and curing it; wherein, the resin material used includes the following components by weight percentage:

[0035] 65 - 75% epoxy resin, 25 - 35% silica powder;

[0036] Among them, the particle size of the silica powder is 1-3um;

[0037] In the vacuum resin plugging process, the vacuum degree is -0.08 Mpa, and the curing conditions are curing for 55-65 minutes at a temperature of 140-160 °C.

[0038] Ceramic grinding plate: Use an alumina ceramic grinding wheel to grind the plate to make the surface of the resin in the hole flush with the outer copper foil surface of the multilayer circuit board, and the surface roughness Ra < 0.1um. Among them, the grinding process parameters are: pressure 5-8 N / cm 2 , rotation speed 200-300 rpm, wire speed 1-2 m / min;

[0039] Secondary electroless copper plating: Electroless copper plating is carried out on the surface of the plugged resin to form a copper plating layer, and the copper plating layer covers the resin material after the vacuum resin plugging and ceramic grinding plate are completed. The thickness of the copper plating layer is 0.3-0.5um;

[0040] Secondary electroplating: Full-board electroplating is carried out to deposit a second copper plating layer on the outer copper foil surface of the multilayer circuit board, and the copper thickness on the resin ≥ 12um is satisfied;

[0041] Outer layer circuit production: The outer copper foil of the multilayer circuit board is combined with the second copper plating layer to form the surface copper layer of the circuit board. The outer layer circuit is produced on the surface copper layer, LDI exposure (alignment accuracy is controlled at ±5um), and the line width / line pitch after etching is 50um / 50um (tolerance is controlled at plus or minus 10%).

[0042] The following elaborates in detail on the manufacturing method of the small-pitch light board of the present invention through specific embodiments.

[0043] Example 1: Fabricate a four-layer LED light board with P1.25

[0044] A manufacturing method of a small-pitch light board includes the following steps:

[0045] Lamination: Laminate the core board with the PP layer and copper foil. After lamination, the total board thickness is controlled at 0.8mm ± 10%;

[0046] Drilling: Mechanically drill through holes with a hole diameter of 0.25mm, and the hole position accuracy is controlled at ±15um;

[0047] Electroless copper plating: The thickness of the copper plating layer on the hole wall is 0.4um, and the backlight ≥ 9.5 levels;

[0048] Through-hole electroplating: Electroplate on the surface of the electroless copper-plated holes to form a first copper plating layer on the through-hole wall, and the thickness of the first copper plating layer is controlled at ≥ 18um;

[0049] Vacuum resin plugging of vias: The resin material includes the following components by weight percentage: 70wt% of epoxy resin (EP-230) and 30wt% of silica powder (particle size 2um); Plugging vias with a vacuum plugging machine (vacuum degree -0.08 Mpa), curing conditions: 150°C / 60 min;

[0050] Ceramic grinding of the board: Grinding parameters: Alumina ceramic grinding wheel (#200 mesh), pressure 6 N / cm 2 , rotation speed 250 rpm, linear speed 1.5 m / min;

[0051] Second copper deposition: Thickness of the copper plating layer is 0.4um;

[0052] Second electroplating: Full-panel electroplating to make the copper thickness on the resin 20um;

[0053] Fabrication of the outer layer circuit: LDI exposure (alignment accuracy controlled at ±5um), line width / line pitch after etching is 50um / 50um (tolerance controlled at ±10%);

[0054] The small-pitch lamp board fabricated in this embodiment has a structure as Figure 1 shown. The small-pitch lamp board of this embodiment includes a multi-layer circuit board 1 formed by lamination, vias 2 penetrating the multi-layer circuit board 1, a first copper plating layer 3 deposited on the via hole walls, plugging resin 4 filled in the vias, a copper plating layer 5 deposited on the surface of the plugging resin, a second copper plating layer 6 deposited on the surface of the outer copper foil of the multi-layer circuit board through a full-panel electroplating process, the outer copper foil of the multi-layer circuit board and the second copper plating layer combine to form a surface copper layer 7, and an outer layer circuit is designed on the surface copper layer.

[0055] In this embodiment, the multi-layer circuit board 1 includes a core board 11, a first PP layer 12 and a second PP layer 13 laminated on both sides of the core board 11, a first copper foil 14 laminated on the surface of the first PP layer 12, and a second copper foil 15 laminated on the surface of the second PP layer 13. The inner layer core board circuit fabrication has been completed before the lamination of the multi-layer circuit board 1. Among them, the core board 11 includes an epoxy resin material layer 111 filled inside, a first core board copper foil 112 and a second core board copper foil 113 laminated on both sides of the epoxy resin material layer 111 filled inside, and circuit layers are designed on the first core board copper foil 112 and the second core board copper foil 113 respectively; the first copper foil 14 and the second copper foil 15 are the outer copper foils of the multi-layer circuit board.

[0056] Correspondingly, the aperture of the through hole 2 is 0.2 - 0.3 mm, and the thickness of the first copper plating layer 3 on the hole wall of the through hole is ≥ 18 μm; the surface of the resin plugging hole is flat after being ground by a ceramic grinding plate, and the resin plugging hole after grinding is flush with the outer copper foil surface of the multi-layer circuit board (i.e., flush with the surfaces of the first copper foil 14 and the second copper foil 15 respectively); the thickness of the copper plating layer 5 is 0.3 - 0.5 μm, and the copper thickness on the resin plugging hole is ≥ 12 μm. In this embodiment, the copper thickness on the resin plugging hole is 20 μm.

[0057] After testing, the offset between the lamp bead PAD and the hole position in this embodiment is < 5 μm, which can meet the requirements of conduction alignment accuracy, and the adhesion of the copper layer on the surface of the resin plugging hole area is ≥ 1.2 N / mm, which can meet the requirements of the industry (ASTM D3359 standard).

[0058] In addition to the above embodiments, the multi-layer circuit board can be formed by laminating multiple core boards as needed. And for the small-pitch lamp bead circuit board of the present invention, the pitch of the lamp bead PAD can be extended to P1.0.

[0059] The above has made a detailed description of the embodiments of the present invention, 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 principle and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A manufacturing method of a small-pitch light board, characterized in that, It includes the following steps: Lamination: Laminating single or multiple core boards with inner layer circuits fabricated to obtain a multi-layer circuit board; Drilling: Mechanically drilling through-holes with a hole diameter of 0.2 - 0.3 mm; Copper deposition on holes: The thickness of the copper layer on the hole wall is 0.3 - 0.5 μm, and the backlight is ≥ 9.5 levels; Through-hole electroplating: The copper thickness in the hole is ≥ 18 μm; Vacuum resin plugging of holes: Using epoxy resin with a shrinkage rate < 0.5% to fill the through-holes and curing; Ceramic grinding plate: Use an alumina ceramic grinding wheel for grinding the plate to make the surface of the resin inside the hole flush with the outer copper foil surface of the multilayer circuit board, and the surface roughness Ra < 0.1um. The grinding process parameters are as follows: pressure 5 - 8N / cm 2 , rotation speed 200 - 300rpm, wire speed 1 - 2m / min; Secondary copper deposition: Conducting copper deposition on the surface of the plugged hole resin to form a copper layer, and the copper layer covers the resin material after vacuum resin plugging and ceramic grinding. The thickness of the copper layer is 0.3 - 0.5 μm; Secondary electroplating: Full-board electroplating to make the copper thickness on the resin ≥ 12 μm; Fabrication of outer layer circuits.

2. The manufacturing method of the small-pitch light board according to claim 1, characterized in that, In the vacuum resin plugging of holes process, the resin material used includes the following components by weight percentage: Epoxy resin 65 - 75%, silica powder 25 - 35%; Among them, the particle size of the silica powder is 1 - 3 μm.

3. The manufacturing method of the small-pitch light board according to claim 1, wherein In the vacuum resin plugging of holes process, the vacuum degree is -0.08 Mpa, and the curing conditions are curing at 140 - 160 °C for 55 - 65 min.

4. The manufacturing method of the small-pitch light board according to claim 1, characterized in that The pitch of the LED pads on the circuit board is P1.0 or P1.25.

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