Processing method for avoiding fracture of copper sheet in flexible area of multi-layer rigid-flexible printed circuit board

Abstract

A processing method for avoiding fracture of a copper sheet in a flexible area of a multi-layer rigid-flex board comprises the following steps: step 1, manufacturing an inner layer structure of the multi-layer rigid-flex board, and pressing a cover film; step 2, cutting the TPI; step 3, laminating TPI (Thermoplastic Polyimide); 4, PP is cut; 5, PP is attached; 6, transmitting the pressure of the copper foil; step 7, etching; and step 8, solder resist and degumming. The TPI is attached to the soft board area of the circuit board, the covering film on the inner side and the copper foil on the outer side are bonded through the TPI, in the subsequent machining process of the circuit board, no cavity exists between the copper foil on the outer layer and the covering film on the inner layer, and the problem that the copper foil is broken in the machining process is effectively solved; the method is high in practicability and has high popularization significance.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing processes, and more particularly to a processing method for avoiding copper foil cracking in the flexible area of ​​a multilayer rigid-flex board. Background Technology

[0002] Lightweight and thinner designs are the current development trend for multilayer rigid-flex circuit boards. Therefore, as the overall thickness of circuit boards continues to decrease, it is necessary to design PP lamination with thinner TOZ or thinner copper foil. However, the conventional open-cover method (etched cover opening) for flexible boards often results in a high rate of copper foil breakage and defective scrap.

[0003] Specifically, during the initial opening process, because the flexible circuit board area and the outer thin copper foil form a cavity, the outer copper foil is prone to cracking and allowing chemicals to enter after subsequent processes such as grinding, cleaning, and sandblasting. During circuit fabrication, the chemicals within the cavity of the flexible circuit board area continuously overflow and contaminate the board surface, leading to a high rate of defects in the circuit board section. Summary of the Invention

[0004] Therefore, it is necessary to provide a processing method to avoid copper foil cracking in the flexible zone of a multilayer rigid-flexible bonded plate, addressing the shortcomings of existing technologies.

[0005] A processing method for avoiding copper foil cracking in the flexible zone of a multilayer rigid-flexible bonded plate includes the following steps:

[0006] Step 1: Fabricate the inner layer structure of the multi-layer rigid-flex plate and press the cover film onto it;

[0007] Step 2: Cut TPI. Take the TPI material and cut it to the same size as the flexible board area of ​​the circuit board.

[0008] Step 3: Laying TPIs. The cut TPIs are laminated onto the flexible board area of ​​the circuit board, and vacuum pre-pressing is performed using a vacuum pre-pressing device.

[0009] Step 4: Cut PP, take PP material and cut or punch it to the same size as the rigid board area of ​​the circuit board;

[0010] Step 5: Attach the PP, attach the cut PP to the rigid area of ​​the circuit board;

[0011] Step 6: Press copper foil. Take copper foil material and use a pressing machine to press the copper foil onto the surface of the circuit board.

[0012] Step 7: Etching. First, perform routine outer layer processing on the circuit board until the pattern transfer is completed. Then, perform etching on the circuit board. During etching, the copper foil in the flexible board area is etched away to expose the TPI in the flexible board area.

[0013] Step 8: Solder resist removal. Solder resist processing is performed on the rigid board area of ​​the circuit board, and then plasma adhesive removal is used to remove the TPI from the flexible board area to obtain a complete rigid-flex board product.

[0014] Furthermore, in step 2, inward compensation is performed when cutting the TPI material to prevent the cut TPI from extending into the rigid plate area during bonding. The inward compensation parameter range is 0.3-0.5mm.

[0015] Furthermore, in step 3, the standard parameters for vacuum preloading are a temperature of 100°C and a pressure of 20 kg / cm². 2 Vacuuming lasts for 5 seconds, and pre-compression lasts for 5 seconds.

[0016] Furthermore, steps 4 to 7 can be repeated multiple times.

[0017] In summary, the beneficial effects of the processing method for avoiding copper foil cracking in the flexible area of ​​a multilayer rigid-flex board according to the present invention are as follows: by designing to attach TPI to the flexible area of ​​the circuit board, and using TPI to bond the inner cover film and the outer copper foil respectively, no cavity will appear between the outer copper foil and the inner cover film during subsequent processing of the circuit board, effectively avoiding the problem of copper foil cracking during processing; 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 5 in this invention;

[0019] Figure 2 This is a cross-sectional structural diagram of step 6 in the present invention;

[0020] Figure 3 This is a cross-sectional structural diagram of step 7 in the present invention;

[0021] Figure 4 This is a cross-sectional structural diagram of step 8 in the present invention. Detailed Implementation

[0022] 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.

[0023] like Figures 1 to 4 As shown, the present invention provides a processing method for avoiding copper foil cracking in the flexible region of a multilayer rigid-flexible bonded plate, comprising the following steps:

[0024] Step 1: Fabricate the inner layer structure of the multi-layer rigid-flex plate and press the cover film onto it;

[0025] Step 2: Cut TPI. Take the TPI material and cut it to the same size as the flexible board area of ​​the circuit board. When cutting the TPI material, you can make inward compensation according to customer needs and equipment accuracy to avoid the cut TPI extending into the rigid board area when it is bonded. The inward compensation parameter range is 0.3-0.5mm. Cutting a TPI of appropriate size can meet the bonding support of the flexible board area of ​​the circuit board without causing adverse effects on the rigid board area.

[0026] Step 3: Laying TPI. The cut TPI is laminated onto the flexible board area of ​​the circuit board, and vacuum pre-pressing is performed using a vacuum pre-pressing device. Specifically, in this embodiment, the standard parameters for vacuum pre-pressing are a temperature of 100℃ and a pressure of 20 kg / cm². 2 Vacuuming lasts for 5 seconds, pre-compression lasts for 5 seconds;

[0027] Step 4: Cut PP, take PP material and cut or punch it to the same size as the rigid board area of ​​the circuit board;

[0028] Step 5: Attach the PP, attach the cut PP to the rigid area of ​​the circuit board;

[0029] Step 6: Pressing the copper foil. Take copper foil material and use a pressing machine to press the copper foil onto the surface of the circuit board. After pressing the copper foil, the copper foil layer completely covers the flexible board area and the rigid board area of ​​the circuit board. Since the copper foil is supported by TPI in the flexible board area, the copper foil in the flexible board area will not break after pressing and bonding, ensuring good sealing of the flexible board area and effectively preventing the problem of chemical seepage during subsequent processing.

[0030] Step 7: Etching. First, perform routine outer layer processing on the circuit board until the pattern transfer is completed. Then, perform etching on the circuit board. During etching, the copper foil in the flexible board area is etched away to expose the TPI in the flexible board area.

[0031] Specifically, in this embodiment, steps 4 to 7 can be repeated multiple times; repeating steps 4 to 7 can achieve the forming and processing of more layers of rigid-flexible plates, ensuring that different production needs are met.

[0032] Step 8: Solder resist removal. Solder resist processing is performed on the rigid board area of ​​the circuit board, and then plasma adhesive removal is used to remove TPI from the flexible board area to obtain a complete rigid-flex board product. Plasma adhesive removal is a dry process, which is cleaner and more environmentally friendly than conventional chemical adhesive removal. At the same time, plasma adhesive removal can penetrate into fine structures such as micropores and blind vias, removing residues (such as epoxy resin and glass fiber) through physical bombardment and chemical reaction, and activating the surface. The treated surface is clean and hydrophilic, enhancing the adhesion of subsequent plating or coating.

[0033] In summary, the beneficial effects of the processing method for avoiding copper foil cracking in the flexible area of ​​a multilayer rigid-flex board according to the present invention are as follows: by designing to attach TPI to the flexible area of ​​the circuit board, and using TPI to bond the inner cover film and the outer copper foil respectively, no cavity will appear between the outer copper foil and the inner cover film during subsequent processing of the circuit board, effectively avoiding the problem of copper foil cracking during processing; 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 processing method for avoiding copper skin rupture in a flexible area of a multilayer rigid-flex combined board, characterized in that, The method comprises the following steps: Step 1: making the inner structure of the multi-layer rigid-flex printed circuit board and pressing the cover film; Step 2: cutting the TPI, taking the TPI material and cutting it into the size consistent with the soft board area of the circuit board; Step 3: attaching the TPI, attaching the cut TPI to the soft board area of the circuit board and performing vacuum pre-pressing processing by using a vacuum pre-pressing device; Step 4: cutting the PP, taking the PP material and cutting or punching it into the size consistent with the hard board area of the circuit board; Step 5: attaching the PP, attaching the cut PP to the hard board area of the circuit board; Step 6: transferring the copper foil, taking the copper foil material and pressing the copper foil on the surface of the circuit board by using a transfer machine device; Step 7: etching, first performing conventional outer layer processing and manufacturing until completing pattern transfer, and then performing etching processing on the circuit board, wherein the copper foil of the soft board area is etched and eliminated during the etching processing, and the TPI of the soft board area is exposed; Step 8: solder mask glue removal, performing solder mask processing on the hard board area of the circuit board, and then removing the TPI from the soft board area by using plasma glue removal to obtain a complete rigid-flex printed circuit board product.

2. The processing method for avoiding copper skin breakage in the flexible area of a multilayer rigid-flex combined board according to claim 1, wherein: In the step 2, the TPI material is cut with internal shrinkage compensation to avoid the cut TPI from extending into the hard board area when being attached, and the internal shrinkage compensation parameter range is 0.3-0.5 mm.

3. The processing method for avoiding copper skin breakage in the flexible area of a multilayer rigid-flex combined board according to claim 1, wherein: In the step 3, the standard parameters of vacuum pre-pressing are temperature 100°C, pressure 20 kg / cm 2 , vacuuming for 5 seconds, pre-pressing for 5 seconds.

4. The processing method for avoiding copper skin breakage in the flexible area of a multilayer rigid-flex combined board according to claim 3, wherein: The steps 4 to 7 can be repeated multiple times.

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