Printed circuit board (PCB) based on electroplating filling through hole and preparation method thereof

Abstract

The invention discloses a PCB (printed circuit board) based on electroplating filling of through holes and a preparation method thereof, and belongs to the technical field of circuit board preparation, and the preparation method comprises the steps of material distribution, mechanical drilling, hole plugging, laser drilling, degumming, chemical copper deposition and electroplating filling of the through holes, and the PCB is prepared through the steps. The hole plugging comprises the steps that holes to be subjected to laser drilling are plugged, and hole plugging materials used for hole plugging do not contain glass fibers; the aperture of a hole drilled by the mechanical drilling is larger than or equal to that of a hole drilled by the laser drilling, the laser drilling comprises the step of performing laser drilling on the position where the hole is located after the hole is plugged, and the center of the hole drilled by the mechanical drilling and the center of the hole drilled by the laser drilling are located at the same position; and the number of holes drilled by the mechanical drilling is equal to that of holes drilled by the laser drilling. According to the method, the hole plugging substance is not provided with glass fibers, point discharge does not exist in the laser drill holes machined in the hole plugging substance during electroplating through hole filling, the problem of poor hole filling cavities is solved, and the aspect ratio of the holes is increased to 6: 1.

Description

Technical Field

[0001] The invention relates to a PCB based on electroplating through-hole filling and a preparation method thereof, belonging to the technical field of circuit board preparation. Background Art

[0002] In PCB industry products, electrical interconnection between layers is achieved by using metallized holes. There are many ways to metallize holes. Electroplating filling through-hole process is one of the important electroplating processes. However, the aspect ratio (ratio of board thickness to hole diameter) is relatively low. Most of them can only process X-shaped through-holes with a board thickness of 200~300um, a hole diameter of 80~100um, and an aspect ratio of no more than 4:1 (the processing method is front laser and back laser, and the through-hole shape formed is X, so it is called X-shaped through-hole). Otherwise, serious electroplating filling voids will occur (such as Figure 2 as shown). Summary of the invention

[0003] The object of the present invention is to provide a PCB based on electroplating through-hole filling and a preparation method thereof, so as to solve the problems of low aspect ratio and poor hole filling voids in the process of preparing PCB by electroplating through-hole filling in the prior art.

[0004] To achieve the above objectives, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides a method for preparing a PCB based on electroplating through-hole filling, comprising: PCB is prepared through the following steps: material delivery, mechanical drilling, plugging, laser drilling, debonding, chemical copper deposition and electroplating to fill through holes; The plugging comprises: plugging the hole to be laser drilled, wherein the plugging material used for the plugging does not contain glass fiber; The diameter of the hole drilled by the mechanical drilling is greater than or equal to the diameter of the hole drilled by the laser drilling. The laser drilling includes laser drilling at the location of the hole after plugging the hole. The center of the hole drilled by the mechanical drilling and the center of the hole drilled by the laser drilling are at the same position. The number of holes drilled by the mechanical drilling is equal to the number of holes drilled by the laser drilling.

[0005] Furthermore, when the mechanical drilling is performed, the thickness of the board is greater than 200 um.

[0006] Furthermore, the plugging material used for plugging the hole includes plugging resin, ink and liquid resin.

[0007] Furthermore, the plugging is completed by a common plugging machine or a vacuum plugging machine.

[0008] Furthermore, the viscosity of the plugging material is 200 dPa·s~1000 dPa·s.

[0009] Furthermore, the glass transition temperature of the plugging material is 150°C to 200°C.

[0010] Further, the electroplating through-hole filling includes: S1. The through holes are closed by electroplating copper to overlap the center positions of the through holes, and the through holes are divided into an upper blind hole and a lower blind hole; S2, completing the filling of the blind holes in the upper part and the blind holes in the lower part; S3, filling the opening positions of the upper half blind holes and the lower half blind holes so that the filled holes are sunken to meet the preset requirements.

[0011] Furthermore, during the copper electroplating process, the thickness of the copper is greater than or equal to half of the aperture of the through hole.

[0012] Furthermore, the current density used when executing the step S3 is smaller than the current density used when executing the step S2, and the jet density used when executing the step S3 is smaller than the jet density used when executing the step S2.

[0013] In a second aspect, the present invention provides a PCB based on electroplating through-hole filling, which is prepared based on any method described in the first aspect.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: The present invention provides a PCB based on electroplating through-hole filling and a preparation method thereof, wherein mechanical drilling is first performed at the laser hole position, the hole is plugged, and then laser drilling is performed. Because the plugging material does not contain glass fiber, there will be no tip discharge in the laser drilled hole processed thereon when the through-hole is electroplated and filled, which can effectively solve the poor hole filling voids that occur in the traditional electroplating through-hole filling process, and at the same time, the aspect ratio of the hole can be at least increased to 6:1. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of a method for preparing a PCB based on electroplating through-hole filling provided by an embodiment of the present invention; Figure 2 It is a schematic diagram of poor hole filling voids in the prior art of electroplating through-hole filling provided by an embodiment of the present invention; Figure 3 is a cross-sectional schematic diagram of a board at an intermediate stage of a through-hole filling process of electroplating provided by an embodiment of the present invention; Figure 4 It is a schematic diagram of a PCB prepared by the method of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention.

[0017] Example 1.

[0018] like Figure 1 As shown, the present invention provides a PCB preparation method based on electroplating through-hole filling, comprising: PCB is prepared through the following steps: material delivery, mechanical drilling, plugging, laser drilling, debonding, chemical copper deposition and electroplating to fill through holes; The plugging includes: plugging a hole to be laser drilled, wherein the plugging material used for the plugging does not contain glass fiber; The diameter of the hole drilled by mechanical drilling is greater than or equal to the diameter of the hole drilled by laser drilling. Laser drilling includes laser drilling at the location of the hole after plugging the hole. The center of the hole drilled by mechanical drilling and the center of the hole drilled by laser drilling are at the same position. The number of holes drilled by mechanical drilling is equal to the number of holes drilled by laser drilling.

[0019] The present invention mechanically drills holes at the laser hole positions first, plugs the holes, and then laser drills the holes. Because the plugging material does not contain glass fibers, the laser drilled holes processed thereon will not have tip discharge when the through-holes are electroplated and filled. This can effectively solve the poor hole filling voids that occur in traditional electroplating through-hole filling processes, and at least increase the aspect ratio of the holes to 6:1.

[0020] Example 2.

[0021] The root cause of the defects in the prior art is that during the electroplating process, the glass fiber at the hole wall is electroplated faster than other positions due to the tip discharge, so it will close first to form a void, such as Figure 3 The figure shows the situation in the middle stage of the electroplating process. From the trend of copper plating on the hole wall, it can be seen that after the electroplating is completed, Figure 2 Poor hole filling voids are shown.

[0022] In order to solve the above problems, Figure 1 As shown, the present invention provides a PCB preparation method based on electroplating through-hole filling, and its specific implementation includes the following steps: Step 1: Send materials; Step 2: Mechanical drilling; plate thickness: 450um, mechanical drilling aperture: 150um, mechanical drilling coordinates: the center point of mechanical drilling is equal to the center point of laser drilling, the number of mechanical drilling holes: 20,000; Step 3: plugging holes; plugging material: plugging resin, viscosity: 500dPa·s, Tg: 160℃; Step 4: Laser drilling, the aperture is 75um, laser drilling once on the front side and once on the back side; Step 5: Remove glue; Step 6: Chemical copper deposition; Step 7: Fill the through holes with electroplating.

[0023] Step 7 can be expanded as follows: S1: According to the laser drilling aperture, it is determined that the electroplated copper thickness in the first stage is >37.5um, and the current density is set to 20asf, the electroplating time is 90 minutes, the jet frequency is 20Hz, the copper ion concentration of the solution is controlled at 210-240g / L, and the solution temperature is 24-26℃. According to the formula, the electroplated copper thickness H=current density*electroplating time*0.022 is 39.6um, and the electroplating through-hole bridging period is completed; S2: Set the current density to 15asf, the electroplating time to 60 minutes, the jet frequency to 18Hz, the copper ion concentration of the solution to 210-240g / L and the solution temperature to 24-26℃ to complete the electroplating through-hole filling burst period; S3: Set the current density to 10asf, the electroplating time to 10 minutes, the jet frequency to 10Hz, the copper ion concentration of the solution to 210-240g / L and the solution temperature to 24-26℃ to complete the electroplating through-hole repair period.

[0024] Example 3.

[0025] The present invention provides a PCB based on electroplating through-hole filling, which is prepared by the method provided in Example 1, and its effect is as follows: Figure 4 As shown, there is no hole filling void phenomenon.

[0026] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a PCB based on electroplating through-hole filling, characterized in that: include: PCB is prepared through the following steps: material delivery, mechanical drilling, plugging, laser drilling, debonding, chemical copper deposition and electroplating to fill through holes; The plugging comprises: plugging the hole to be laser drilled, wherein the plugging material used for the plugging does not contain glass fiber; The diameter of the hole drilled by the mechanical drilling is greater than or equal to the diameter of the hole drilled by the laser drilling. The laser drilling includes laser drilling at the location of the hole after plugging the hole. The center of the hole drilled by the mechanical drilling and the center of the hole drilled by the laser drilling are at the same position. The number of holes drilled by the mechanical drilling is equal to the number of holes drilled by the laser drilling.

2. The method for preparing a PCB based on electroplating through-hole filling according to claim 1, characterized in that: When the mechanical drilling is performed, the thickness of the board is greater than 200 um.

3. The method for preparing a PCB based on electroplating through-hole filling according to claim 1, characterized in that: The plugging materials used for plugging the holes include plugging resin, ink and liquid resin.

4. The method for preparing a PCB based on electroplating through-hole filling according to claim 1, characterized in that: The plugging is completed by a common plugging machine or a vacuum plugging machine.

5. The method for preparing a PCB based on electroplating through-hole filling according to claim 3, characterized in that: The viscosity of the plugging material is 200 dPa·s~1000 dPa·s.

6. The method for preparing a PCB based on electroplating through-hole filling according to claim 3, characterized in that: The glass transition temperature of the plugging material is 150°C to 200°C.

7. The method for preparing a PCB based on electroplating through-hole filling according to claim 1, characterized in that: The electroplating through-hole filling comprises: S1. The through holes are closed by electroplating copper to overlap the center positions of the through holes, and the through holes are divided into an upper blind hole and a lower blind hole; S2, completing the filling of the blind holes in the upper part and the blind holes in the lower part; S3, filling the opening positions of the upper half blind holes and the lower half blind holes so that the filled holes are sunken to meet the preset requirements.

8. The method for preparing a PCB based on electroplating through-hole filling according to claim 7, characterized in that: During the copper electroplating process, the thickness of the copper is greater than or equal to half of the aperture of the through hole.

9. The method for preparing a PCB based on electroplating through-hole filling according to claim 7, characterized in that: The current density used when executing the S3 step is smaller than the current density used when executing the S2 step, and the jet density used when executing the S3 step is smaller than the jet density used when executing the S2 step.

10. A PCB based on electroplating through-hole filling, characterized in that: Prepared according to the method according to any one of claims 1 to 9.

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