Preparation method of printed circuit board with blind slot and printed circuit board

Abstract

The invention discloses a preparation method of a printed circuit board with a blind slot and the printed circuit board, which are used for solving the problems that in the manufacturing process of a multi-layer board, when the inner-layer gold plating area is large, namely the prepreg bonding area is small, a core board can generate large stripping stress in a high-temperature and high-pressure environment in the pressing process, and the bonding effect is poor. And plate explosion and layering are very easy to occur. The preparation method of the printed circuit board comprises the step of drilling a ventilation hole in each of the two ends, corresponding to a blind groove area, of a conventional layer core board. Therefore, the expansion stress of the core board can be released in time through the air holes, and the phenomenon of board explosion and layering when the bonding area of the prepreg of the printed circuit board is relatively low is avoided. The printed circuit board manufactured by the invention has the advantages of no board explosion layering, simple manufacturing method, easy realization of batch production and the like.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit boards, and in particular to a method for preparing a printed circuit board with a blind groove and a printed circuit board. Background Art

[0002] In printed circuit boards, the characteristic of blind slot design is that it will not run through the entire PCB stacking structure, occupying a better space, making the layout of components denser and more flexible, and connecting different layers of signals, simplifying the patching line to reduce the thickness of the circuit board and optimize the overall area. At present, with the increase of blind slot design products, the final welding area of ​​the blind slot is generally made of hard gold plating and soft gold plating. In order to ensure the precise separation of the semi-cured sheet and the gold-plated layer, it is necessary to select a resist film for blocking. The semi-cured sheet in the area covered by the resist film is a hollow area, which means that there is no adhesion after the area covered by the resist film is pressed. After molding, the resist film is manually peeled off at the resist film to expose the gold-plated area. In the existing technology, when the inner layer gold-plated area accounts for more than 30% (that is, the resist film coverage), that is, the semi-cured sheet bonding area is less than 70%, the core board of the printed circuit board will produce a large peeling stress during the high-temperature baking process, and it is very easy to explode and delaminate. Summary of the invention

[0003] The present invention aims to provide a method for preparing a printed circuit board with a blind groove, so as to solve the problem of board delamination at the resistive film when the core board is pressed. The method comprises: S1. Core board cutting: prepare two core boards, namely core board core1 and core board core2; S2, inner layer processing: firstly, drill holes in core board core1 and core board core2, and drill a vent hole at both ends of the blind groove area of ​​core board core1, and then sequentially perform inner layer copper deposition, full board electroplating, inner layer pattern transfer, inner layer etching and film stripping on core board core1 and core board core2; S3, forming a partially gold-plated inner circuit pattern on the core board core2: wet film pattern transfer and dry film pattern transfer are sequentially performed on the core board core2, both of which expose the copper layer in the gold-plated area, and the exposed copper layer is gold-plated after the dry film pattern transfer, and then the dry film and the wet film are removed to form a partially gold-plated core board core2; wet film pattern transfer and dry film pattern transfer are sequentially performed on the core board core2 after the partial gold plating, both of which expose the copper layer in the wire area, and the excess copper layer in the wire area is etched away, and then the film is stripped to form a partially gold-plated inner circuit pattern; S4, pressing and outer layer drilling: the core board core1 after step S2 and the core board core2 after step S3 are stacked and pressed through prepreg, a resist film is placed in the gold-plated area between the core board core1 and the core board core2, and then the production board is drilled according to the drill tape data; S5, forming outer layer circuits and surface treatment; S6, adhesive film processing and finished product molding: remove the adhesive film with controlled depth and shape the shape; S7, FQC final inspection and electrical testing.

[0004] Furthermore, in step S2, the diameter of the air holes ranges from 0.3 to 0.5 mm; the inner copper plating is to copper-plate the walls of the drilled holes of the core board core1 and the core board core2 to form a conductive hole; the inner pattern transfer is to coat the surface of the core board core1 and the core board core2 with a photoresist film, and form a circuit pattern through exposure and development; the core board core2 needs to design leads to the process edge in the gold-plated area to ensure electroplating conduction; the inner layer etching and film stripping are to use alkaline solution to remove the photoresist in the unexposed area, and then etch the exposed copper layer with an acidic etching solution, and the circuit forming is completed after the film is stripped.

[0005] Furthermore, the gold plating in step S3 is nickel gold or soft gold.

[0006] Furthermore, after drilling in step S4, plasma treatment is required to remove the glue residue in the hole and activate the surface of the hole wall to improve the adhesion of subsequent copper deposition, as well as copper deposition and electroplating. After chemical copper deposition, the entire board is electroplated to thicken the hole wall to ensure the conduction reliability of the through hole; the air holes need to be exposed when removing the glue residue, and the air holes are sealed with high-temperature tape during copper deposition and electroplating.

[0007] Furthermore, in step S5, the outer layer circuit is formed by sequentially subjecting the production board to film lamination, exposure, and development processes to form an outer layer circuit pattern, and the unexposed area is exposed by alkaline solution and etched away by acid etching to form an outer layer circuit after film removal; the surface treatment includes AOI optical inspection, solder mask, and character printing; the air holes need to be exposed during the solder mask process, and the air holes need to be sealed with high-temperature tape in other surface treatment processes and in the process of forming the outer layer circuit.

[0008] The present invention provides a printed circuit board with a blind groove, and the printed circuit board is manufactured by adopting the above-mentioned method for manufacturing a printed circuit board.

[0009] The printed circuit board of the present invention has a double-layer core board, and a vent hole is drilled at each end of the blind groove area of ​​core 1 of one of the core boards. Through precise pattern transfer, gold plating process and lamination control PCB, the problem of lamination of the resist film is effectively solved by adding the design of vent holes, ensuring the reliability of the product; it solves the problem that in the method of making double-core lamination of resist film, when the cavity area of ​​the inner blind groove area accounts for more than 30%, it is very easy to produce stratification and explosion in the negative pressure environment during the heating process and the plasma treatment stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is the design drawing of the "breathing hole" of the dual-core pressed-resistance film. DETAILED DESCRIPTION

[0011] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] The present invention provides a method for preparing a printed circuit board with a blind groove, the method comprising: S1. Core board cutting: prepare two core boards, namely core board core1 and core board core2; S2, inner layer processing: first, drill holes in the core board core1 and core2, and drill a vent hole with a diameter range of 0.3-0.5mm at both ends of the blind groove area of ​​the core board core1 for subsequent pressing and exhaust, and then perform inner layer copper plating, full board electroplating, inner layer pattern transfer, inner layer etching and film stripping on the core board core1 and core2 in turn; inner layer copper plating is to copper plate the drilled hole walls of the core board core1 and core2 to form a via hole; inner layer pattern transfer is to coat the surface of the core board core1 and core2 with a photoresist film, and form a circuit pattern through exposure and development; the core board core2 needs to design the lead to the process edge in the gold-plated area to ensure electroplating conduction; inner layer etching and film stripping are to use alkaline solution to remove the photoresist in the unexposed area, and then etch the exposed copper layer with acid etching solution, and complete the circuit forming after film stripping.

[0013] S3, core board core2 forms a partially gold-plated inner layer circuit pattern, including: Step S31, wet film pattern transfer: apply a wet film on the surface of the core board core2, retain the non-gold-plated area through exposure and development, and expose the copper surface of the gold-plated area; S32, dry film pattern transfer: superimpose dry film and double-exposure and develop to further protect the non-gold-plated area and ensure accurate positioning of the gold-plated area; S33, gold plating: nickel-gold plating or soft gold plating is performed on the exposed copper layer to form a local gold-plated structure; S34, film stripping: remove the wet film and dry film on the surface of core board core2, and keep the gold-plated area; S35, wet film pattern transfer: apply wet film on the surface of core board core2, expose and develop to expose the copper layer in the conductor area; S36, dry film pattern transfer: apply dry and wet film on the surface of core board core2, and expose and develop to expose the copper layer in the conductor area; S37, wire etching and film stripping: Etch to remove excess copper layer in the wire area, and after film stripping, a complete inner layer circuit pattern with partial gold plating is formed.

[0014] S4, pressing and outer layer drilling: the core board core1 after step S2 and the core board core2 after step S3 are stacked and pressed through the semi-cured sheet, and a resist film is placed in the gold-plated area between the core board core1 and the core board core2; the production board after pressing is as follows Figure 1 As shown, the production board is then drilled according to the drill tape data to connect the circuits of each layer; after drilling, plasma treatment is required to remove the glue residue in the hole and activate the surface of the hole wall to improve the adhesion of subsequent copper deposition, as well as copper deposition and electroplating. After chemical copper deposition, the hole wall is thickened by electroplating on the entire board to ensure the conduction reliability of the through-hole; the air holes need to be exposed when removing the glue residue, and the air holes are sealed with high-temperature tape during copper deposition and electroplating.

[0015] S5. Formation of outer circuits and surface treatment. To form outer circuits, the production board is subjected to film pasting, exposure and development processes in sequence to form outer circuit patterns. The unexposed areas are exposed by alkaline solution and etched away by acid etching to form outer circuits after film removal. Surface treatment includes AOI optical inspection, solder mask and character printing. The air holes need to be exposed during the solder mask process, and the air holes need to be sealed with high-temperature tape during other surface treatment processes and the process of forming outer circuits. AOI optical inspection is to compare design data through automatic optical inspection to identify circuit pattern defects. Solder mask is silk-screen solder mask ink, and the pad area is retained after exposure and development. Character printing is the character identification of welding points (such as component position numbers).

[0016] S6, resist film processing and finished product molding; use a depth-controlled guillotine to accurately guillotine the resist film position, manually tear off the resist film to expose the inner gold-plated area; mill the board edge according to the designed size to complete the final shape processing.

[0017] S7. Finally, conduct electrical testing and FQC final inspection; test the conductivity and insulation of the finished board; use FQC (final quality inspection) equipment to detect surface defects (scratches, poor gold plating, etc.).

[0018] Among them, in step S4 and step S5, in the process of removing the glue residue and the process of screen printing the solder mask ink, it is necessary to ensure that the vents are exposed so that the high-temperature material can be released through the vents when it expands; and in the process, it is necessary to use high-temperature tape to seal the vents to prevent moisture from entering through the vents and affecting the quality of the finished product.

[0019] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a printed circuit board with a blind groove, characterized in that: The following steps are involved: S1. Core board cutting: prepare two core boards, namely core board core1 and core board core2; S2, inner layer processing: firstly, drill holes in core board core1 and core board core2, and drill a vent hole at both ends of the blind groove area of ​​core board core1, and then perform inner layer copper deposition, full board electroplating, inner layer pattern transfer, inner layer etching and film stripping on core board core1 and core board core2 in turn; S3, forming a partially gold-plated inner circuit pattern on the core board core2: wet film pattern transfer and dry film pattern transfer are sequentially performed on the core board core2, both of which expose the copper layer in the gold-plated area, and the exposed copper layer is gold-plated after the dry film pattern transfer, and then the dry film and the wet film are removed to form a partially gold-plated core board core2; wet film pattern transfer and dry film pattern transfer are sequentially performed on the core board core2 after the partial gold plating, both of which expose the copper layer in the wire area, and the excess copper layer in the wire area is etched away, and then the film is stripped to form a partially gold-plated inner circuit pattern; S4, pressing and outer layer drilling: the core board core1 after step S2 and the core board core2 after step S3 are stacked and pressed through prepreg, a resist film is placed in the gold-plated area between the core board core1 and the core board core2, and then the production board is drilled according to the drill tape data; S5, forming outer layer circuits and surface treatment; S6, adhesive film processing and finished product molding: remove the adhesive film with controlled depth and shape the shape; S7, FQC final inspection and electrical testing.

2. The method according to claim 1, characterized in that The diameter of the vent holes in step S2 is in the range of 0.3-0.5 mm.

3. The method according to any one of claims 1 to 2, characterized in that: The inner layer copper plating in step S2 is to plate copper on the walls of the drilled holes of the core board core1 and the core board core2 to form a through hole.

4. The method according to claim 3, characterized in that In step S3, the gold plating is nickel gold or soft gold.

5. The method according to claim 4, characterized in that In step S4, after drilling, plasma treatment is required to remove the glue residue in the hole, activate the hole wall surface, and perform copper deposition and electroplating; the air holes need to be exposed when removing the glue residue, and high-temperature tape is used to seal the air holes during copper deposition and electroplating.

6. The method according to claim 5, characterized in that In step S5, the surface treatment includes AOI optical inspection, solder mask and character printing; the ventilation holes need to be exposed during the solder mask process, and the ventilation holes need to be sealed with high-temperature tape during other surface treatment processes and the outer layer circuit process.

7. A printed circuit board, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

Images