Method for combining flexible printed circuit board and reinforcing steel sheet

Abstract

The invention provides a method for combining a flexible printed circuit board and a reinforcing steel sheet, and the method comprises the following steps: S100, carrying out the etching of one side of the reinforcing steel sheet, and etching an annular pattern around the edge of the reinforcing steel sheet; s200, the side, where the patterns are etched, of the reinforcing steel sheet is coated with conductive adhesive, the distance between the conductive adhesive and the edge of the reinforcing steel sheet ranges from 0.05 mm to 0.15 mm, and the conductive adhesive is located in the annular patterns; and S300, pressing the side, coated with the conductive adhesive, of the reinforcing steel sheet at the tail end of the flexible printed circuit board. According to the manufacturing method, the annular patterns are etched on the edge of the reinforcing steel sheet, the conductive adhesive is coated in the patterns, and the conductive adhesive is 0.05-0.15 mm away from the edge, so that the conductive adhesive is effectively limited in the pattern area in the pressing process, and overflow of the conductive adhesive is prevented. The problem that the conductive adhesive overflows to the outside to affect subsequent manufacturing and assembling of the RFPC is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of circuit boards, and particularly relates to a method for combining a flexible printed circuit board with a reinforcing steel sheet. Background Art

[0002] A flexible printed circuit board (RFPC) is a hybrid circuit board that combines the advantages of both rigid and flexible circuit boards. It offers excellent flexibility and durability and is widely used in various electronic devices. In an RFPC, the header and tail refer to two distinct sections of the board, each with different manufacturing requirements and characteristics. The tail section, located at one end of the RFPC, typically connects to other circuits or devices. This section requires reinforcement with thicker steel sheets to provide greater mechanical support and stability. The thickness of the tail sheet is typically ≥0.2mm. Think of it like sewing a rigid sheet onto a soft piece of fabric to strengthen this area and prevent it from being torn or folded. When adding the reinforcement sheet, conductive adhesive is used to adhere the sheet to the tail section of the RFPC, and then the sheet is securely fastened to the tail section by pressing. However, after pressing, the conductive adhesive can overflow, compromising the subsequent fabrication and assembly of the flexible printed circuit board. Summary of the Invention

[0003] In view of this, the present invention provides a method for combining a flexible printed circuit board with a reinforcing steel sheet, thereby preventing the conductive adhesive from overflowing to the outside.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for combining a flexible printed circuit board with a reinforcing steel sheet, comprising: The following steps are included: S100, etching one side of the reinforcing steel sheet to form a ring-shaped pattern surrounding the edge of the reinforcing steel sheet; S200, applying a conductive adhesive on one side of the reinforcing steel sheet having the etched pattern, wherein the conductive adhesive is 0.05-0.15 mm away from the edge of the reinforcing steel sheet and is located inside the annular pattern; S300, pressing the side of the reinforcing steel sheet coated with the conductive adhesive onto the flexible printing plate The tail end of the circuit board.

[0005] Preferably, in step S1, the depth of the etched pattern is 0.08-0.12 mm.

[0006] Preferably, in step S1, the distance between the annular pattern and the edge of the reinforcing steel sheet 1 is 0.01-0.03 mm.

[0007] Preferably, in step S1, the step of etching the pattern is: S110, coating a layer of photoresist on the surface of the reinforcing steel sheet; S120, placing the reinforced steel sheet coated with the photoresist under an ultraviolet exposure machine, and using a mask to project a predetermined pattern onto the photoresist layer; S130, removing the photoresist in the unexposed area by a developer, leaving only the exposed portion; S140, etching a ring-shaped pattern.

[0008] Preferably, in step 140 , after the annular pattern is etched, the photoresist layer is removed.

[0009] Preferably, an organic solvent is used to remove the photoresist.

[0010] Preferably, in step 140 , a strong acid or a strong base is used to etch the annular pattern.

[0011] Preferably, in step S100, after etching the annular pattern, a first internal pattern is etched in the annular pattern, and the distance between the first internal pattern and the edge of the reinforcing steel sheet is 0.035-0.05 mm.

[0012] Preferably, in step S100, a second internal pattern is further etched, and the distance between the second internal pattern and the edge of the reinforcing steel sheet is 0.12-0.15 mm.

[0013] Preferably, the depth of the first inner pattern and the second inner pattern is 0.05-0.1 mm.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention etches a ring-shaped pattern on the edge of the reinforcing steel sheet and applies the conductive adhesive inside the pattern at a distance of 0.05-0.15 mm from the edge. During the pressing process, the conductive adhesive is effectively confined to the pattern area, preventing overflow of the conductive adhesive. This solves the problem of conductive adhesive overflowing and affecting the subsequent production and assembly of the RFPC.

[0015] (2) The present invention further refines the distribution and bonding area of the conductive adhesive by etching the first internal pattern and the second internal pattern on the basis of the annular pattern, thereby improving the firmness and stability of the connection between the reinforcing steel sheet and the RFPC board. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of a method for combining a flexible printed circuit board and a reinforcing steel sheet provided in one embodiment of the present invention; Figure 2This is a schematic structural diagram of a reinforcing steel sheet provided in one embodiment of the present invention.

[0017] Reference numerals: reinforcing steel sheet 100 , annular pattern 1 , first inner pattern 2 , second inner pattern 3 . DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to specific embodiments so that those skilled in the art can understand the present invention more clearly.

[0019] A flexible printed circuit board (RFPC) is a hybrid circuit board that combines the advantages of both rigid and flexible circuit boards. It offers excellent flexibility and durability and is widely used in various electronic devices. In an RFPC, the header and tail refer to two distinct sections of the board, each with different manufacturing requirements and characteristics. The tail section, located at one end of the RFPC, typically connects to other circuits or devices. This section requires reinforcement with thicker steel sheets to provide greater mechanical support and stability. The thickness of the tail sheet is typically ≥0.2mm. Think of it like sewing a rigid sheet onto a soft piece of fabric to strengthen this area and prevent it from being torn or folded. When adding the reinforcement sheet, conductive adhesive is used to adhere the sheet to the tail section of the RFPC, and then the sheet is securely fastened to the tail section by pressing. However, after pressing, the conductive adhesive can overflow, compromising the subsequent fabrication and assembly of the flexible printed circuit board.

[0020] Combine Figure 1-2 The present invention provides a method for combining a flexible printed circuit board and a reinforcing steel sheet, comprising the following steps: S100, etching one side of the reinforcing steel sheet 100 to form an annular pattern 1 surrounding the edge of the reinforcing steel sheet 100; S200, applying conductive adhesive to one side of the reinforcing steel sheet 100 where the pattern is etched, with the conductive adhesive being 0.05-0.15 mm away from the edge of the reinforcing steel sheet 100 and being located inside the annular pattern 1; Exemplarily, the conductive glue is arranged inside the annular pattern 1, and the annular pattern 1 serves to limit the conductive glue to avoid a large amount of overflow of the conductive glue. At the same time, the distance between the conductive glue and the edge of the reinforcing steel sheet 100 is 0.05-0.15mm, which avoids overflow of the conductive glue.

[0021] S300 , pressing the side of the reinforcing steel sheet 100 coated with the conductive adhesive onto the rear end of the flexible printed circuit board.

[0022] For example, after applying the conductive adhesive, the reinforcing steel sheet 100 is pressed onto the rear end of the flexible printed circuit board. This allows the reinforcing steel sheet 100 and the circuit board to be tightly connected through physical compression. During the pressing process, the conductive adhesive acts between the reinforcing steel sheet 100 and the flexible circuit board, ensuring a strong bond.

[0023] The method for combining a flexible printed circuit board with a reinforcing steel sheet 100 of the present invention solves problems such as conductive adhesive overflow and insufficient connection strength through steps such as etching patterns, accurately applying conductive adhesive, and pressing connections, thereby improving electrical performance and mechanical stability, making the application of flexible circuit boards in electronic devices more reliable and durable.

[0024] Furthermore, the etched pattern depth is 0.08-0.12mm. The annular pattern 1 prevents conductive adhesive from overflowing. However, the annular pattern 1 should not be too deep or too shallow, as this will weaken the barrier effect. Controlling the etching depth within the range of 0.08-0.12mm ensures sufficient surface roughness on the reinforcing steel sheet 100, increasing the contact area with the flexible circuit board. This design significantly improves the adhesion between the reinforcing steel sheet 100 and the circuit board, thereby making the two more firmly bonded.

[0025] Furthermore, the distance between the annular pattern 1 and the edge of the reinforcing steel sheet 100 is 0.01-0.03 mm, for example, 0.01 mm, 0.02 mm, or 0.03 mm.

[0026] Furthermore, in step S1, the steps of etching the pattern are: S110, coating a layer of photoresist on the surface of the reinforcing steel sheet 100; Specifically, in order to facilitate etching, a layer of photoresist is first coated on the surface of the reinforcing steel sheet 100. The photoresist can form a protective layer of the pattern in the subsequent etching process.

[0027] S120, placing the reinforced steel sheet 100 coated with the photoresist under an ultraviolet exposure machine, and using a mask to project a predetermined pattern onto the photoresist layer; Specifically, after ultraviolet irradiation, the exposed areas of the photoresist undergo a chemical reaction and become less soluble.

[0028] S130, removing the photoresist in the unexposed area by a developer, leaving only the exposed portion; Specifically, these portions will serve as areas for protecting the surface of the reinforcing steel sheet 100 from being etched.

[0029] S140, etching a ring-shaped pattern 1.

[0030] Specifically, the areas uncovered by the photoresist are removed by chemical etching or electrochemical etching. The etching solution is typically a strong acid or alkaline solution, which can remove the exposed areas of the steel sheet. Through this process, the pattern of the annular pattern 1 is formed on the reinforced steel sheet 100.

[0031] Furthermore, in step 140, after the annular pattern 1 is etched, the photoresist layer is removed. Furthermore, the photoresist is removed using an organic solvent. In some embodiments, in step 140, a strong acid or a strong base is used to etch the annular pattern 1.

[0032] Furthermore, in step S100, after etching the annular pattern 1, a first internal pattern 2 is etched within the annular pattern 1. The distance between the first internal pattern 2 and the edge of the reinforcing steel sheet 100 is 0.035-0.05 mm. Etching the first internal pattern 2 within the annular pattern 1 significantly increases the bonding area and roughness of the reinforcing steel sheet 100, while also optimizing the distribution of the conductive adhesive and improving the overall mechanical strength and electrical performance. The first internal pattern 2 also acts as a limiter, preventing the applied conductive adhesive from exceeding this range.

[0033] Furthermore, in step S100, a second internal pattern 3 is etched, and the distance between the second internal pattern 3 and the edge of the reinforcing steel sheet 100 is 0.12-0.15 mm. The etched second internal pattern 3, by setting the pattern etching position in the area 0.12-0.15 mm from the edge of the reinforcing steel sheet 100, further enhances the bonding area, optimizes the distribution of the conductive adhesive, and significantly improves the stability of the entire bonding interface. This design not only enhances the bonding force between the reinforcing steel sheet 100 and the flexible circuit board, but also improves its mechanical strength, fatigue resistance and electrical performance, allowing the product to work more reliably in various environments. At the same time, the second internal pattern 3 also serves as a limiter, that is, the applied conductive adhesive is prevented from exceeding this range.

[0034] In some embodiments, the depth of the first internal pattern 2 and the second internal pattern 3 is 0.05-0.1 mm, which increases the surface roughness and bonding area of the reinforcing steel sheet 100 .

[0035] Performance testing is the result In Example 1, a reinforcing steel sheet 100 is provided. The distance between the conductive adhesive and the edge of the reinforcing steel sheet 100 is 0.05 mm. The distance between the annular pattern 1 and the edge of the reinforcing steel sheet 100 is 0.01 mm, with a depth of 0.1 mm. The distance between the first internal pattern 2 and the edge of the reinforcing steel sheet 100 is 0.025 mm. The distance between the second internal pattern 3 and the edge of the reinforcing steel sheet 100 is 0.12 mm. The depths of the first internal pattern 2 and the second internal pattern 3 are both 0.12 mm. The flexible printed circuit board and the reinforcing steel sheet are bonded securely without adhesive overflow.

[0036] In Example 2, a reinforcing steel sheet 100 is provided. The distance between the conductive adhesive and the edge of the reinforcing steel sheet 100 is 0.07 mm. The distance between the annular pattern 1 and the edge of the reinforcing steel sheet 100 is 0.03 mm, with a depth of 0.1 mm. The distance between the first internal pattern 2 and the edge of the reinforcing steel sheet 100 is 0.04 mm. The distance between the second internal pattern 3 and the edge of the reinforcing steel sheet 100 is 0.12 mm. The depths of the first and second internal patterns 2 and 3 are both 0.12 mm. The flexible printed circuit board and the reinforcing steel sheet are bonded securely without adhesive overflow.

[0037] Example 3 provides a reinforcing steel sheet 100. The distance between the conductive adhesive and the edge of the reinforcing steel sheet 100 is 0.1 mm. The distance between the annular pattern 1 and the edge of the reinforcing steel sheet 100 is 0.03 mm, with a depth of 0.1 mm. The distance between the first internal pattern 2 and the edge of the reinforcing steel sheet 100 is 0.04 mm. The distance between the second internal pattern 3 and the edge of the reinforcing steel sheet 100 is 0.12 mm. The depths of the first and second internal patterns 2 and 3 are both 0.12 mm. The flexible printed circuit board and the reinforcing steel sheet are bonded securely without adhesive overflow.

[0038] Example 4 provides a reinforcing steel sheet 100. The distance between the conductive adhesive and the edge of the reinforcing steel sheet 100 is 0.15 mm. The distance between the annular pattern 1 and the edge of the reinforcing steel sheet 100 is 0.03 mm, with a depth of 0.1 mm. The distance between the first internal pattern 2 and the edge of the reinforcing steel sheet 100 is 0.04 mm. The distance between the second internal pattern 3 and the edge of the reinforcing steel sheet 100 is 0.12 mm. The depths of the first and second internal patterns 2 and 3 are both 0.12 mm. The flexible printed circuit board and the reinforcing steel sheet are bonded securely without adhesive overflow.

[0039] Comparative Example 1 provides a reinforcing steel sheet 100. The distance between the conductive adhesive and the edge of the reinforcing steel sheet 100 is 0.20 mm. The distance between the annular pattern 1 and the edge of the reinforcing steel sheet 100 is 0.03 mm, with a depth of 0.1 mm. The distance between the first internal pattern 2 and the edge of the reinforcing steel sheet 100 is 0.04 mm. The distance between the second internal pattern 3 and the edge of the reinforcing steel sheet 100 is 0.12 mm. The depths of the first internal pattern 2 and the second internal pattern 3 are both 0.12 mm. The connection between the flexible printed circuit board and the reinforcing steel sheet was free of adhesive overflow. However, some of the resulting products were not strong enough and cracked, with a cracking rate of 0.05%.

[0040] Comparative Example 2 provides a reinforcing steel sheet 100. The distance between the conductive adhesive and the edge of the reinforcing steel sheet 100 is 0.01 mm. The distance between the annular pattern 1 and the edge of the reinforcing steel sheet 100 is 0.03 mm, with a depth of 0.1 mm. The distance between the first internal pattern 2 and the edge of the reinforcing steel sheet 100 is 0.04 mm, and the depths of the first internal pattern 2 and 0.12 mm are both 0.12 mm. Some adhesive overflow occurred when bonding the flexible printed circuit board to the reinforcing steel sheet, but the overflow rate was 0.03%, indicating a strong bond.

[0041] Comparative Example 3 provides a reinforcing steel sheet 100. The distance between the conductive adhesive and the edge of the reinforcing steel sheet 100 is 0.01 mm. The distance between the annular pattern 1 and the edge of the reinforcing steel sheet 100 is 0.03 mm, and the depth is 0.1 mm. Some adhesive overflow occurred when bonding the flexible printed circuit board to the reinforcing steel sheet, but the overflow rate was 0.05%, indicating a strong bond.

[0042] Comparative Example 4 provides a reinforcing steel sheet 100, and the distance between the conductive adhesive and the edge of the reinforcing steel sheet 100 is 0.01 mm. The adhesive overflows from the flexible printed circuit board to the reinforcing steel sheet, with an overflow rate of 0.06%, indicating a strong bond.

[0043] The raw materials not specifically described in the present invention are all existing materials that can be directly purchased from the market.

[0044] The above is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for combining a flexible printed circuit board with a reinforcing steel sheet, characterized in that: Bag The following steps are included: S100, etching one side of the reinforcing steel sheet to form a ring-shaped pattern surrounding the edge of the reinforcing steel sheet; S200, applying a conductive adhesive on one side of the reinforcing steel sheet having the etched pattern, wherein the conductive adhesive is 0.05-0.15 mm away from the edge of the reinforcing steel sheet and is located inside the annular pattern; S300: Pressing the side of the reinforcing steel sheet coated with the conductive adhesive onto the rear end of the flexible printed circuit board.

2. The bonding method according to claim 1, characterized in that: In step S1 , the depth of the etched pattern is 0.08-0.12 mm.

3. The bonding method according to claim 1, characterized in that: In step S1 , the distance between the annular pattern and the edge of the reinforcing steel sheet 1 is 0.01-0.03 mm.

4. The bonding method according to claim 1, characterized in that: In step S1, the steps of etching the pattern are as follows: S110, coating a layer of photoresist on the surface of the reinforcing steel sheet; S120, placing the reinforced steel sheet coated with the photoresist under an ultraviolet exposure machine, and using a mask to project a predetermined pattern onto the photoresist layer; S130, removing the photoresist in the unexposed area by a developer, leaving only the exposed portion; S140, etching a ring pattern.

5. The bonding method according to claim 4, characterized in that: In step 140, After the ring-shaped pattern is etched, the photoresist layer is removed.

6. The bonding method according to claim 5, characterized in that: The photoresist is removed using an organic solvent.

7. The bonding method according to claim 6, characterized in that: In step 140 , a strong acid or a strong base is used to etch the ring-shaped pattern.

8. The bonding method according to claim 3, characterized in that: In step S100, after etching the annular pattern, a first internal pattern is etched in the annular pattern, and the distance between the first internal pattern and the edge of the reinforcing steel sheet is 0.035-0.05 mm.

9. The bonding method according to claim 8, characterized in that: In step S100, a second internal pattern is further etched, and the distance between the second internal pattern and the edge of the reinforcing steel sheet is 0.12-0.15 mm.

10. The bonding method according to claim 9, characterized in that: The depth of the first inner pattern and the second inner pattern is 0.05-0.1 mm.

Images