A processing method for controlled deep hole metallization of printed circuit board

Abstract

The present invention discloses a processing method for controlled deep hole metallization of a printed circuit board, the method comprising the steps of setting a copper hollowing area in advance for each circuit layer, controlling the depth of drilling and setting a lead hole, first copper deposition treatment, first thickening treatment, pattern transfer (positive film), tinning electro-deposition thickening treatment, alkaline etching and silk screen solder resist, etc. The method of the present invention is reasonably designed, the setting of the lead hole can ensure that the controlled deep hole can be through, and the hole copper will not be bad during chemical deposition and electro-deposition thickening, and the positive film process can be selected during pattern transfer, which is conducive to the processing of fine circuits.

Description

Technical Field

[0001] The invention belongs to the technical field of printed circuit boards, and in particular relates to a processing method for controlled deep hole metallization of a printed circuit board. Background Art

[0002] As the carrier of electronic product components, the printed circuit board (PCB) is an important part of electronic products and the basis for realizing the functions of electronic products. As the functions of electronic products continue to become more powerful and the styles continue to become more novel, they are increasingly widely used in various electronic products. With the advent of the 5G era, the market prospects for printed circuit boards are broad, and their design structures are becoming increasingly complex. Among them, thick copper power boards have the advantages of carrying large currents, reducing thermal strain, and good heat dissipation. Due to the requirements of current carrying and voltage resistance, there are special requirements for copper thickness and dielectric layer thickness. The dielectric layer thickness is thinner. Conventional controlled depth hole metallized printed circuit boards use CNC drilling machines for controlled depth processing, and the depth control accuracy is ±0.1mm. Therefore, there are the following problems: First, the controlled depth holes are not through-holes. During chemical deposition and electrodeposition thickening, due to the poor circulation of the solution in the controlled depth holes, poor hole copper (no copper in the holes, copper slag in the holes, etc.) will occur. The deeper the controlled depth, the more serious the poor situation; second, because the controlled depth holes are not through-holes, positive etching (using electroplated tin as the anti-corrosion layer) cannot be selected during pattern transfer, and only negative etching can be used, which brings difficulties to the processing of fine lines. Summary of the invention

[0003] In order to solve the above problems, improve the quality of controlled deep hole metallization of printed circuit boards and select positive etching process when transferring patterns, so as to facilitate the processing of fine lines, the present invention provides a processing method for controlled deep hole metallization of printed circuit boards, wherein the printed circuit board comprises a multi-layer circuit layer 1 and a multi-layer dielectric layer 2, a dielectric layer 2 is arranged between each two adjacent circuit layers 1, and the printed circuit board is also provided with controlled deep holes 3, characterized in that the processing method comprises the following steps:

[0004] Step 1: When designing the circuit of the printed circuit board, the circuit layer 1 of the core board below the bottom position of the depth control hole 3 is provided with a copper hollowing area 4, that is, before laminating each layer of the printed circuit board, the corresponding position of each circuit layer 1 that the depth control hole 3 does not penetrate is first hollowed out, so that the copper hollowing area 4 of the laminated multilayer printed circuit board is filled with the medium in the dielectric layer 2;

[0005] Step 2: Perform controlled depth drilling on the laminated multilayer printed circuit board. After the controlled depth hole 3 is processed, add a lead hole 5 from the bottom of the controlled depth hole 3 to the other end of the printed circuit board opposite to the controlled depth hole 3. The cross-sectional size of the lead hole 5 is smaller than the cross-sectional size of the controlled depth hole 3. The thickness of the printed circuit board is H, the depth of the controlled depth hole 3 is h, and the depth of the lead hole 5 is Hh.

[0006] Step 3: The printed circuit board is subjected to the first copper deposition treatment, and a thin layer of copper is formed on the hole wall after cleaning by chemical copper deposition;

[0007] Step 4: The printed circuit board is subjected to a thickening treatment, and the copper layer thickness of the copper-plated board is thickened by an electro-deposition method;

[0008] Step 5: After the thickening, the printed circuit board is pattern-transferred using dry film and film, using a positive film process;

[0009] Step 6: After the pattern is transferred, the printed circuit board is plated with copper and tin, and the hole copper and surface copper are thickened to the finished product thickness by using the electrodeposition method, and a layer of tin is electrodeposited on the effective pattern and hole wall, and the non-effective pattern is covered with a dry film;

[0010] Step 7: Use alkaline etching to process the circuit to obtain a semi-finished printed circuit board;

[0011] Step 8: When printing solder mask on the printed circuit board, cover and plug the lead hole 5.

[0012] In the present invention, the purpose of the copper plating process in step 3 is to conduct the inner circuit layer 1.

[0013] In the present invention, in fact, in step three, a thin layer of copper is generally formed on the hole walls of the depth control hole 3 and the lead hole 5, in step four, the hole walls of the depth control hole 3 and the lead hole 5 are generally thickened, and in step six, copper-tin is generally electrodeposited on the hole walls of the depth control hole 3 and the lead hole 5.

[0014] In a specific implementation manner, the thin copper in step three has a thickness of 0.2-0.4 μm.

[0015] In a specific implementation manner, the thin copper in step three has a thickness of 0.3 μm.

[0016] In a specific embodiment, in step 4, the copper layer of the copper-plated plate is thickened to 5-10 μm, preferably 6-7 μm, by an electroplating method.

[0017] In a specific embodiment, the diameter of the lead hole 5 in step 2 is 0.1-0.3 mm, preferably 0.2 mm.

[0018] In a specific embodiment, the radius of the copper hollowing area 4 in step 1 is larger than the radius of the depth control hole 3, preferably 0.1 to 0.5 mm larger, more preferably 0.3 mm larger.

[0019] In a specific implementation, step eight includes covering the lead hole 5 with green oil.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The method for controlled deep hole metallization of a printed circuit board provided by the present invention provides a lead hole capable of penetrating the controlled deep hole during the processing, and provides a copper sheet hollowing area, so that the method has the following advantages:

[0022] 1. The controlled depth hole can penetrate, and there will be no hole copper defects during chemical deposition and electrodeposition thickening;

[0023] 2. When transferring the pattern, positive etching can be selected, which is conducive to the processing of fine lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a specific embodiment of the present invention.

[0025] The names of the components corresponding to the numbers in the figure are as follows:

[0026] 1-circuit layer; 2-dielectric layer; 3-deep hole; 4-copper hollowing area; 5-lead hole. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present invention.

[0028] Controlled depth holes are generally drilled without drilling through the circuit board, and a certain depth is controlled. Therefore, failure of the controlled depth hole to penetrate will lead to poor copper holes and other situations. The deeper the depth of the controlled depth hole, the more serious the poor situation.

[0029] like Figure 1 As shown, the present invention provides a processing method for controlled deep hole metallization of a printed circuit board, wherein the printed circuit board comprises a multi-layer circuit layer 1 and a multi-layer dielectric layer 2, a dielectric layer 2 is arranged between each two adjacent circuit layers 1, and the printed circuit board (thick copper power board) is also provided with controlled depth holes 3. The method is described below with a specific embodiment.

[0030] Embodiment 1, the processing method comprises the following steps:

[0031] Step 1: When designing the circuit of the printed circuit board, a copper hollowing area 4 is provided on the circuit layer 1 of the core board below the position of the depth control hole 3, that is, before laminating each layer of the printed circuit board, the corresponding position of each circuit layer 1 that is not penetrated by the depth control hole 3 is first hollowed out. The cross-sectional area of ​​a single copper hollowing area 4 is generally larger than the cross-sectional area of ​​the depth control hole 3. The shape of the copper hollowing area 4 is generally circular, and it can also be other shapes. For ease of processing, it is generally circular, and the cross-sectional radius of the copper hollowing area 4 is 0.3mm larger than the cross-sectional radius of the depth control hole 3. After laminating each layer of the circuit layer 1, the copper hollowing area 4 will be filled with the material of the dielectric layer 2 to prevent the copper of the hole wall of the lead hole 5 from being conductive with the circuit layer 1 below the bottom of the depth control hole 3 after copper plating in the subsequent steps.

[0032] Step 2: Perform controlled depth drilling on the laminated multilayer printed circuit board. After the depth control hole 3 is processed, add a lead hole 5 in the depth control hole 3 to the other end of the printed circuit board opposite to the depth control hole 3. The cross section of the lead hole 5 is smaller than the cross section of the depth control hole 3. The thickness of the printed circuit board is H, the depth of the depth control hole 3 is h, and the depth of the lead hole 5 is Hh. Because the client usually welds a measuring needle in the depth control hole 3, the diameter of the lead hole 5 should not be too large, and the diameter of the lead hole 5 is preferably 0.2 mm.

[0033] Step 3: The first copper deposition treatment of the printed circuit board is carried out by using chemical copper deposition to form a thin copper layer on the hole wall after cleaning, with a thickness of about 0.3μm;

[0034] Step 4: The printed circuit board is subjected to a thickening treatment. The copper layer of the copper-plated board is thickened by an electrodeposition method to a thickness of 6-7 μm.

[0035] Step 5: Once the printed circuit board is thickened, the pattern is transferred using dry film and film, and the positive process is adopted. Because the negative process has serious side etching and poor circuit quality, it is not conducive to the processing of fine circuits. After setting the lead hole 5, the thick copper power board can adopt the positive etching process because the potion has good penetration performance and can avoid the situation of incomplete copper plating and tin plating, which is more conducive to the processing of fine circuits.

[0036] Step 6: After the pattern is transferred, the printed circuit board is plated with copper and tin, and the hole copper and surface copper are thickened to the finished product thickness by using the electrodeposition method, and a layer of tin is electrodeposited on the effective pattern and hole wall, and the non-effective pattern is covered with a dry film;

[0037] Step 7: Use alkaline etching to process the circuit to obtain a semi-finished printed circuit board;

[0038] Step 8: When printing solder mask on the printed circuit board, cover the lead hole 5 with green oil.

[0039] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for processing controlled depth hole metallization of a printed circuit board, the printed circuit board comprising a plurality of circuit layers (1) and a plurality of dielectric layers (2), a dielectric layer (2) being provided between each two adjacent circuit layers (1), the printed circuit board further being provided with controlled depth holes (3), characterized in that: The processing method comprises the following steps: Step 1: When designing the circuit of the printed circuit board, the circuit layer (1) below the bottom position of the depth control hole (3) is provided with a copper foil hollowing area (4), that is, before laminating each layer of the printed circuit board, the corresponding position of each circuit layer (1) that the depth control hole (3) does not penetrate is first hollowed out, so that the copper foil hollowing area (4) of the laminated multi-layer printed circuit board is filled with the dielectric in the dielectric layer (2); Step 2: Controlled depth drilling is performed on the laminated multilayer printed circuit board. After the controlled depth hole (3) is processed, a guide hole (5) is added from the bottom of the controlled depth hole (3) to the other end of the printed circuit board opposite to the controlled depth hole (3). The cross-sectional dimension of the guide hole (5) is smaller than the cross-sectional dimension of the controlled depth hole (3). The thickness of the printed circuit board is H, the depth of the controlled depth hole (3) is h, and the depth of the guide hole (5) is Hh. Step 3: The printed circuit board is subjected to the first copper deposition treatment, and a thin layer of copper is formed on the hole wall after cleaning by chemical copper deposition; Step 4: The printed circuit board is subjected to a thickening treatment, and the copper layer thickness of the copper-plated board is thickened by an electro-deposition method; Step 5: After the thickening, the printed circuit board is pattern-transferred using dry film and film, using a positive film process; Step 6: After the pattern is transferred, the printed circuit board is plated with copper and tin, and the hole copper and surface copper are thickened to the finished product thickness by using the electrodeposition method, and a layer of tin is electrodeposited on the effective pattern and hole wall, and the non-effective pattern is covered with a dry film; Step 7: Use alkaline etching to process the circuit to obtain a semi-finished printed circuit board; Step 8: When printing solder mask on the printed circuit board, the lead hole (5) is covered and plugged.

2. The method according to claim 1, characterized in that: The thickness of the thin copper in step 3 is 0.2-0.4 μm.

3. The method according to claim 2, characterized in that: The thickness of the thin copper in step 3 is 0.3 μm.

4. The method according to claim 1, characterized in that: In step 4, the copper layer thickness of the copper-plated plate is thickened to 5-10 μm by electroplating.

5. The method according to claim 4, characterized in that: In step 4, the copper layer thickness of the copper-plated plate is thickened to 6-7 μm by electroplating.

6. The method according to claim 1, characterized in that: The diameter of the lead hole (5) in step 2 is 0.1-0.3 mm.

7. The method according to claim 1, characterized in that: The radius of the copper sheet hollowing area (4) in step 1 is larger than the radius of the depth control hole (3).

8. The method according to claim 7, characterized in that: The radius of the copper hollowing area (4) in step 1 is 0.1-0.5 mm larger than the radius of the depth control hole (3).

9. The method according to any one of claims 1 to 8, characterized in that: Step eight includes covering the lead hole (5) with green oil.

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