A method for processing a stepped groove with a bottom step having a circuit

Abstract

A kind of bottom step has the processing method of step groove with circuit, it includes the following steps: step 1: inner layer circuit;Step 2: solder resist processing;Step 3: paste resist film;Step 4: outer layer circuit;Step 5: process first blind groove;Step 6: process step groove.The present application is designed in the alignment pad of groove bottom circuit, and based on the alignment pad of groove bottom circuit, step groove is processed, can greatly optimize and promote the alignment accuracy between step groove, and reduce the offset amount of step groove bottom relative to internal circuit, can simultaneously realize the requirement of high-precision alignment between step groove body and bottom groove body circuit pattern exposure, compared with conventional processing mode, can satisfy the demand of higher, precision, sharp circuit board product;The present application has strong practicability, and has strong popularization significance.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing processes, and in particular to a method for processing a stepped groove with wiring on the bottom step. Background Technology

[0002] In traditional printed circuit board manufacturing processes, two main solutions are used for processing stepped grooves that require high alignment accuracy.

[0003] The first approach involves grooving the core board and prepreg separately, then laminating all the sub-board layers with the prepreg layers. This method relies on the layer-by-layer alignment of the grooves to form the semi-finished stepped grooves, and the groove shape is maintained by filling and removing materials before and after lamination. However, the alignment accuracy of this process is highly susceptible to interlayer misalignment caused by resin flow during lamination and the cumulative tolerance of multiple alignments, resulting in significant positional deviations between the final stepped grooves, making it difficult to meet high-precision design requirements.

[0004] To improve alignment accuracy, the second approach introduces a step-by-step depth-controlled machining technique. This approach first uses mechanical or laser methods to control the depth of a larger blind groove on the outer layer. Then, using the same alignment reference point, the inner layer blind groove is further controlled to create a deeper groove at the bottom of the outer layer. While this method significantly improves the alignment accuracy between the grooves, its effectiveness is limited by the cumulative interlayer offset caused by multiple lamination processes. Especially when the bottom of the inner layer groove contains circuit patterns, if the alignment point selected from the outer layer is offset, the inner layer circuit patterns may not be fully and accurately exposed within the specified inner groove dimensions. This increases the risk of product scrap due to incomplete pattern exposure, hindering yield improvement. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for processing stepped grooves with wiring on the bottom step, addressing the shortcomings of existing technologies.

[0006] A method for processing a stepped groove with wiring at the bottom includes the following steps:

[0007] Step 1: Inner layer circuitry. Create a copper-clad board and process the inner layer circuitry to form a printed circuit board containing the inner layer circuitry.

[0008] Step 2: Solder mask processing. The printed circuit board containing inner layer circuits is screen-printed with solder mask, exposed, developed, and the solder mask ink is removed, leaving local solder mask. Several alignment pads are formed at the local solder mask area.

[0009] Step 3: Apply adhesive resist film. Apply adhesive resist film to the local solder resist area. The size of the adhesive resist film should be smaller than the size of the local solder resist area.

[0010] Step 4: Outer layer circuitry. The printed circuit board containing the inner layer circuitry is added to the outer layer, and the outer layer circuitry is exposed, developed, and etched to form a multilayer printed circuit board.

[0011] Step 5: Process the first blind trench. On the surface of the multilayer printed circuit board, the first blind trench is processed from the outside to the inside, corresponding to the position of the alignment pad, until the bottom of the trench exposes the alignment pad. The diameter of the first blind trench is larger than the size of the alignment pad and smaller than the size of the local solder mask.

[0012] Step 6: Machining the stepped groove. Using alignment pads as alignment points, the second blind groove and the third blind groove are machined on the multilayer printed circuit board. The second blind groove and the third blind groove together form the stepped groove.

[0013] Furthermore, in step 3, the size of the resist film is 1-2 mm smaller than the size of the local solder resist.

[0014] Furthermore, in step 5, the first blind groove is processed in two steps. The first processing is carried out by mechanical depth control until the bottom of the first blind groove is above the resist film. The second processing is carried out by laser cutting to open the cover until the bottom of the first blind groove exposes the alignment pad.

[0015] Furthermore, in step 5, the diameter of the first blind groove is more than 2 mm larger than the size of the alignment pad, and the diameter of the first blind groove is more than 2 mm smaller than the size of the local solder mask.

[0016] Furthermore, in step 6, the second and third blind slots are machined using a mechanical depth control method.

[0017] In summary, the beneficial effects of the step groove processing method with circuitry at the bottom of the present invention are as follows: by designing the alignment pads on the circuitry at the bottom of the groove and processing the step groove based on the alignment pads of the circuitry at the bottom of the groove, the alignment accuracy between the step grooves can be significantly optimized and improved, and the offset of the bottom of the step groove relative to the internal circuitry can be reduced. It can simultaneously achieve the requirements of high-precision alignment between the step grooves and complete exposure of the circuitry pattern at the bottom of the groove. Compared with conventional processing methods, it can meet the needs of higher-end, more sophisticated circuit board products. The present invention is highly practical and has strong promotional significance. Attached Figure Description

[0018] Figure 1 This is a cross-sectional structural diagram of steps 1 to 3 in this invention;

[0019] Figure 2 This is a cross-sectional structural diagram of step 4 in the present invention;

[0020] Figure 3 This is a cross-sectional structural diagram of step 5 of the process in this invention;

[0021] Figure 4 This is a cross-sectional structural diagram of another part of the process in step 5 of the present invention;

[0022] Figure 5 This is a cross-sectional structural diagram of step 6 in the present invention;

[0023] Figure 6 This is a cross-sectional structural diagram of another part of the process in step 6 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0025] like Figures 1 to 6 As shown, the present invention provides a method for processing a stepped groove with wiring on the bottom step, comprising the following steps:

[0026] Step 1: Inner layer circuitry. Open a copper-clad board 10 and process the inner layer circuitry to form a printed circuit board 20 containing the inner layer circuitry.

[0027] Step 2: Solder resist processing. The printed circuit board 20 containing inner layer circuits is screen-printed with solder resist, exposed, developed, and the solder resist ink is removed, leaving partial solder resist 30. Several alignment pads 40 are formed at the partial solder resist 30. Compared with conventional outer layer or surface alignment pads 40, the alignment pads 40 designed in the inner layer circuit layer of the circuit board (i.e., the layer where the bottom circuit of the groove is located) provide higher alignment accuracy for the stepped groove processing, making the subsequent stepped groove processing more accurate and the offset smaller. It is understood that in other embodiments, the alignment pads 40 formed in step 2 can also be other printed alignment marks, etc., which are all within the protection scope of this invention.

[0028] Step 3: Apply resist film. Apply resist film 50 to the local solder mask 30. The size of resist film 50 is smaller than that of local solder mask 30. Specifically, in this embodiment, resist film 50 is made of high temperature resistant material, and the size of resist film 50 is 1-2mm smaller than that of local solder mask 30. Applying resist film 50 can effectively protect the alignment pads 40 and prevent the alignment pads 40 from being damaged during the subsequent processing of the outer layer circuit of the circuit board. In addition, the resist film 50 is designed to be slightly smaller than the size of local solder mask 30, which can prevent resist film 50 residue during the subsequent processing of blind slots and stepped slots.

[0029] Step 4: Outer layer circuitry. The printed circuit board 20 containing the inner layer circuitry is added to the outer layer, and the outer layer circuitry is exposed, developed, and etched to form a multilayer printed circuit board 60.

[0030] Step 5: Process the first blind groove 70. On the surface of the multilayer printed circuit board 60, the first blind groove 70 is processed from the outside to the inside, corresponding to the position of the alignment pad 40, until the bottom of the groove exposes the alignment pad 40. Specifically, in this embodiment, the first blind groove 70 is processed in two steps. The first processing uses mechanical depth control to process the groove until the bottom of the first blind groove 70 is above the resist film 50. The second processing uses laser cutting to open the groove until the bottom of the first blind groove 70 exposes the alignment pad 40. Processing the first blind groove 70 in two steps can balance processing efficiency and processing accuracy. Mechanical depth control has higher processing efficiency, while laser opening has higher accuracy and can accurately expose the alignment pad 40 at the bottom of the groove.

[0031] The diameter of the first blind slot 70 is larger than the size of the alignment pad 40 and smaller than the size of the local solder mask 30. Specifically, in this embodiment, the diameter of the first blind slot 70 is more than 2 mm larger than the size of the alignment pad 40, and the diameter of the first blind slot 70 is more than 2 mm smaller than the size of the local solder mask 30.

[0032] Step 6: Machining the stepped groove. Using the alignment pad 40 as the alignment point, the second blind groove 80 and the third blind groove 90 are machined on the multilayer printed circuit board 60 using mechanical depth control. The second blind groove 80 and the third blind groove 90 together form the stepped groove. The alignment pad 40 at the bottom of the first blind groove 70 is used as the alignment reference during the machining process of the stepped groove. The resulting stepped groove has extremely high alignment accuracy and significantly reduced offset, which can meet the requirements of extremely high precision circuit manufacturing.

[0033] In summary, the beneficial effects of the step groove processing method with circuitry at the bottom of the present invention are as follows: by designing the alignment pad 40 on the circuitry at the bottom of the groove and processing the step groove based on the alignment pad 40 of the circuitry at the bottom of the groove, the alignment accuracy between the step grooves can be significantly optimized and improved, and the offset of the bottom of the step groove relative to the internal circuitry can be reduced. It can simultaneously achieve the requirements of high-precision alignment between the step grooves and complete exposure of the circuitry pattern at the bottom of the groove. Compared with conventional processing methods, it can meet the needs of higher-end, more sophisticated circuit board products. The present invention is highly practical and has strong promotional significance.

[0034] The embodiments described above illustrate only one implementation of the invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the invention. Therefore, the scope of protection of the invention patent should be determined by the appended claims.

Claims

1. A method of processing a step groove of a bottom step wiring line, characterized by, Includes the following steps: Step 1: Inner layer circuitry. Create a copper-clad board and process the inner layer circuitry to form a printed circuit board containing the inner layer circuitry. Step 2: Solder mask processing. The printed circuit board containing inner layer circuits is screen-printed with solder mask, exposed, developed, and the solder mask ink is removed, leaving local solder mask. Several alignment pads are formed at the local solder mask area. Step 3: Apply adhesive resist film. Apply adhesive resist film to the local solder resist area. The size of the adhesive resist film should be smaller than the size of the local solder resist area. Step 4: Outer layer circuitry. The printed circuit board containing the inner layer circuitry is added to the outer layer, and the outer layer circuitry is exposed, developed, and etched to form a multilayer printed circuit board. Step 5: Process the first blind trench. On the surface of the multilayer printed circuit board, the first blind trench is processed from the outside to the inside, corresponding to the position of the alignment pad, until the bottom of the trench exposes the alignment pad. The diameter of the first blind trench is larger than the size of the alignment pad and smaller than the size of the local solder mask. Step 6: Machining the stepped groove. Using alignment pads as alignment points, the second blind groove and the third blind groove are machined on the multilayer printed circuit board. The second blind groove and the third blind groove together form the stepped groove.

2. The method of claim 1, wherein: In step 3, the size of the resist film is 1-2 mm smaller than the size of the local solder resist.

3. The method of claim 1, wherein: the step of forming the step groove is performed by a process of: forming a first groove in the substrate; and forming a second groove in the substrate, the second groove being formed in a direction opposite to the first groove. In step 5, the first blind groove is processed in two steps. The first processing is carried out by mechanical depth control until the bottom of the first blind groove is above the resist film. The second processing is carried out by laser cutting to open the cover until the bottom of the first blind groove exposes the alignment pad.

4. The method of claim 1, wherein: the step of forming the step groove is performed by a process of: forming a first groove in the substrate; and forming a second groove in the substrate, the second groove being formed in a direction opposite to the first groove. In step 5, the diameter of the first blind groove is more than 2 mm larger than the size of the alignment pad, and the diameter of the first blind groove is more than 2 mm smaller than the size of the local solder mask.

5. The method of claim 1, wherein: the step of forming the step groove includes the steps of: forming a first step groove in the substrate; and forming a second step groove in the substrate, the second step groove being formed after the first step groove. In step 6, the second and third blind slots are machined using a mechanical depth control method.

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