Pressure transmission method of high-temperature-resistant protective film and manufactured circuit board

Abstract

The invention provides a pressure transmission method of a high-temperature-resistant protective film and a manufactured circuit board. The pressure transmission method comprises the following steps: S1, browning treatment: carrying out browning treatment on a copper surface to be laminated with a protective film on the surface of a copper-clad plate; s2, positioning and fixing a protective film: fixing a layer of protective film outside the copper layer on the surface of the copper-clad plate subjected to brownification treatment; the protective film is a thermoplastic PI (Polyimide) film, and the protective film is Tgt; 200 DEG C; s3, laying an auxiliary material: sequentially stacking the copper-clad plate fixed with the protective film and the auxiliary material to form a special auxiliary material stacking structure; s4, setting parameters of a pressure transmitting procedure, and performing pressure transmitting and pressing on the plate, so that the protective film is laminated and bonded on the FPC circuit board; and S5, after the pressure transmitting and pressing are completed, the plate is disassembled.

Description

Technical Field

[0001] The invention relates to the field of FPC circuit board preparation, and in particular to a pressure transmission method for a high temperature resistant protective film and the prepared circuit board. Background Art

[0002] For products in certain fields, such as shield machines and photolithography machines, the heat resistance quality requirements for circuit boards are very high, and the products need to be able to maintain basic performance for a certain period of time in a high temperature environment. If the circuit board wants to achieve excellent heat resistance and high performance requirements, it is necessary to use a high Tg type protective film.

[0003] For example, the DuPont HT series protective film with a high Tg value is a PI type protective film made of a polyimide material with thermoplastic properties. The Tg value can reach above 200°C, which is the protective film with the highest Tg value in the industry. The copper layer of this protective film has excellent high temperature resistance and is usually used in high-end products with a relatively small scope of use. This protective film is a high Tg value protective film made using a pressure transfer process. The pressure transfer temperature needs to reach a higher temperature point before the protective film will be in a molten state and have a higher adhesion. Therefore, when pressing this type of product, it is very difficult to apply the same pressing process used for protective films with a Tg value of 100°C to the pressing of the DuPont HT series protective film with a high Tg value. Ordinary protective films can meet the quality requirements by using a fast pressing process. However, because the Tg value of the DuPont HT series protective film reaches above 200°C, conventional fast pressing machines cannot reach a temperature of 300+°C and cannot be effectively pressed. Moreover, the obtained pressed products have a series of quality problems. For example, the prepared circuit board products have problems such as delamination, drug infiltration, and gold infiltration. Therefore, this type of high Tg protective film needs to be pressed by a high-temperature press machine. The industry has rarely used the actual pressing process for this type of protective film, and there is currently no applicable pressing method. Summary of the invention

[0004] Based on this, it is necessary to provide a pressure transmission method for a high temperature resistant protective film and a circuit board obtained therefrom.

[0005] In order to solve the above technical problems, the present invention provides a pressure transmission method for a high temperature resistant protective film, comprising the steps of:

[0006] S1. Browning treatment: Browning treatment is performed on the copper surface of the copper clad laminate to be bonded with the protective film;

[0007] S2. Positioning and fixing the protective film: a layer of protective film is fixed on the surface copper layer of the copper clad laminate after the browning treatment; the protective film is a thermoplastic PI film, and the Tg of the protective film is greater than 200°C;

[0008] S3, laying auxiliary materials: stacking the copper clad laminate with the protective film fixed thereon and the auxiliary materials in sequence to form a special auxiliary material stacking structure;

[0009] S4, setting the parameters of the pressure transfer process, and performing the pressure transfer and pressing, so that the protective film is pressed and bonded to the FPC circuit board;

[0010] S5. After the pressure transfer and pressing plate is completed, the plate is removed.

[0011] Preferably, the Tg value of the protective film is 233°C.

[0012] Preferably, the copper clad laminate comprises an insulating layer, a first copper clad layer is provided on a first surface of the insulating layer, a second copper clad layer is provided on a second surface of the insulating layer, and the insulating layer is made of PI. In step S2, the specific steps of fixing a protective film on the surface copper layer of the copper clad laminate include:

[0013] Select a fixed point on the process edge of the copper clad laminate, remove the copper layer at the position of the fixed point, so that the insulating layer is exposed through the copper layer window at the position of the fixed point, and the exposed insulating layer area at the position of the fixed point is the substrate bonding area;

[0014] The protective film is overlapped and laid on the copper-clad laminate so that the protective film at the fixed point is in direct contact with the substrate bonding area, and the protective film at the fixed point is thermally pressed with the substrate bonding area using a thermal bonding device so that the protective film is aligned and fixed on the copper-clad laminate through the fixed point.

[0015] Preferably, the copper clad laminate is a single-sided copper clad laminate. In step S3, the auxiliary material stack includes a copper clad laminate, a first laminate and a second laminate, the first laminate and the second laminate are stacked on the first surface and the second surface of the copper clad laminate, respectively, the first surface of the copper clad laminate is covered with a protective film, the first laminate includes PTFE, HDPE, aluminum foil, steel plate, felt and a carrier, and the second laminate includes PTFE, aluminum foil, steel plate, felt and a cover plate.

[0016] Preferably, the copper clad laminate is a double-sided copper clad laminate. In step S3, the auxiliary material stack includes a copper clad laminate, a first laminate and a second laminate. The first laminate is stacked on the first surface of the copper clad laminate, and the second laminate is stacked on the second surface of the copper clad laminate. The first surface and the second surface of the copper clad laminate are respectively covered with protective films. The first laminate includes PTFE, HDPE, aluminum foil, steel plate, felt and a carrier plate, and the second laminate includes PTFE, HDPE, aluminum foil, steel plate, felt and a cover plate.

[0017] Preferably, in step S4, the total time used for the pressure transmission process is divided into 8 uninterrupted time periods in chronological order, and the 8 time periods respectively have corresponding pressure transmission parameters, and the pressure transmission parameters include pressure transmission temperature, heating time, pressure PSI, pressure rise time and holding time. When the pressure transmission plate is performed, the temperature is raised in sequence from the 1st time period to the 3rd time period, and the temperature is raised in sequence from the 3rd time period to the 8th time period.

[0018] Preferably, when the pressure is transmitted on the pressure plate, the pressures corresponding to the second to eighth time periods are all 500psi, the pressure transmission temperature corresponding to the third time period is 320°C, the heating time corresponding to the third time period is 15min, and the holding time corresponding to the third time period is 90min.

[0019] Preferably, the browning treatment specifically includes the following steps: micro-etching, water washing, alkali washing, water washing, pre-immersion activation, browning, water washing, and drying.

[0020] Preferably, in the browning treatment process, the pre-impregnation activation is to immerse the washed copper clad laminate in an activator for (20-30) s for activation, and the browning step is to immerse the activated copper clad laminate in a browning solution for (50-60) s, wherein the browning solution includes a mixture of hydrogen peroxide, sulfuric acid and a browning agent.

[0021] A high temperature resistant circuit board is manufactured by the method described above.

[0022] Beneficial effects of the invention: The invention provides a pressure transmission method for applying DuPont HT series high Tg protective films on copper-clad laminates.

[0023] Before attaching the protective film, the FPC is subjected to a specific browning treatment; and by optimizing the program parameters of each section of the pressure transmission, the protective film is thermally bonded to the FPC under optimal conditions, effectively solving the bonding problem of the protective film with a high glass transition temperature; at the same time, by using a specific pressure-transmitting auxiliary material stack, the protective film and the FPC are effectively filled and coated, effectively solving the problems of stratified bubbles in the protective film and wrinkles on the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other purposes, features and advantages of the present invention will become more clear by more specific description of the preferred embodiments of the present invention shown in the accompanying drawings. The same reference numerals indicate the same parts in all the accompanying drawings, and the accompanying drawings are not deliberately scaled to the actual size, and the focus is on illustrating the main purpose of the present invention.

[0025] Figure 1 It is a schematic diagram of the auxiliary material stacking structure when the FPC is a single-sided copper-clad laminate for pressure transmission in a preferred embodiment of the present invention;

[0026] Figure 2It is a schematic diagram of the auxiliary material stacking structure when the FPC is a double-sided copper-clad laminate for pressure transmission in a preferred embodiment of the present invention;

[0027] In the figure: copper clad laminate 1; protective film 100; PTFE 2; HDPE 3; aluminum foil 4; steel plate 5; felt 6 and carrier plate 7; cover plate 8. DETAILED DESCRIPTION

[0028] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings.

[0029] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to another element and integrated therewith, or there may be an intermediate element at the same time. The terms "installed", "one end", "the other end" and similar expressions used herein are for illustrative purposes only.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art. The terms used in the specification herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0031] refer to Figure 1 and Figure 2 The present invention provides a pressure transmission method of a high temperature resistant protective film 100, comprising the steps of:

[0032] S1, browning treatment: browning the copper surface of the copper clad laminate 1 to be bonded with the protective film 100;

[0033] S2, positioning and fixing the protective film 100: fixing a layer of high temperature resistant protective film 100 on the surface copper layer of the copper clad laminate 1 after browning treatment; the protective film 100 is a thermoplastic PI film, and the Tg of the protective film 100 is greater than 200°C;

[0034] S3, laying auxiliary materials: stacking the copper clad laminate 1 fixed with the protective film 100 and auxiliary materials in sequence to form a dedicated auxiliary material stacking structure;

[0035] S4, setting the parameters of the pressure transfer process, and performing the pressure transfer and pressing, so that the protective film 100 is pressed and bonded to the FPC circuit board;

[0036] S5. After the pressure transfer and pressing plate is completed, the plate is removed.

[0037] This protective film 100 is manufactured using a pressure transfer process. The temperature needs to reach a certain point before the protective film 100 will be in a molten state and have efficient adhesion. When the pressure transfer method of the present application is used to press this type of high-temperature resistant protective film 100 product, specific pressure transfer parameters and pressure transfer stacking structures are used to achieve excellent bonding between the protective film 100 and the circuit board, thereby ensuring that the circuit board product has excellent reliability performance.

[0038] In a preferred embodiment, the Tg of the protective film 100 is greater than 225° C. Preferably, the Tg of the DuPont HT series protective film 100 is 233° C. The protective film 100 has excellent high temperature resistance. The protective film 100 is attached to a circuit board with high heat resistance requirements, so that the circuit board product can maintain basic performance for a certain period of time in a high temperature environment.

[0039] refer to Figure 1 In a preferred embodiment, the copper clad laminate 1 is a single-sided copper clad laminate 1, and PTFE, HDPE, aluminum foil 4, steel plate 5, and felt 6 are sequentially stacked on the single side with the protective film 100, and the outermost layers on both sides of the single-sided copper clad laminate 1 are clamped and pressed using a carrier plate 7 and a cover plate 8, respectively. In step S3, the auxiliary material stack includes a copper clad laminate 1, a first laminate and a second laminate, and the first laminate and the second laminate are respectively stacked on the first surface and the second surface of the copper clad laminate 1, and the first surface of the copper clad laminate 1 is covered with a protective film 100, the first laminate includes PTFE, HDPE, aluminum foil 4, steel plate 5, felt 6 and a carrier plate 7, and the second laminate includes PTFE, aluminum foil 4, steel plate 5, felt 6 and a cover plate 8.

[0040] The present invention provides an optimized auxiliary material stacking structure, an optimized auxiliary material stacking structure and the orientation of a circuit board product stacked with a protective film 100, so that the product achieves an effective coating and filling effect, thereby solving the problem of circuit board product delamination bubbles and substrate wrinkles caused by applying the same pressing process used for the existing protective film 100 with a Tg value of 100°C to the pressing of the DuPont HT series protective film 100 with a high Tg value.

[0041] refer to Figure 2In a preferred embodiment, if the copper clad laminate 1 is a double-sided copper clad laminate 1, PTFE, HDPE, aluminum foil 4, steel plate 5, and felt 6 are sequentially stacked on the two sides with the protective film 100, and the outermost layers of the two sides of the double-sided copper clad laminate 1 are clamped and pressed using a carrier plate 7 and a cover plate 8. In step S3, the auxiliary material stacking structure includes a copper clad laminate 1, a first laminate and a second laminate, the first laminate is stacked on the first surface of the copper clad laminate 1, and the second laminate is stacked on the second surface of the copper clad laminate 1. The protective film 100 is laid on the first surface and the second surface of the copper clad laminate 1, respectively. The first laminate includes PTFE, HDPE, aluminum foil 4, steel plate 5, felt 6, and a carrier plate 7, and the second laminate includes PTFE, HDPE, aluminum foil 4, steel plate 5, felt 6, and a cover plate 8. PTFE is the abbreviation of polytetrafluoroethylene, which is Teflon; HDPE is the abbreviation of high-density polyethylene.

[0042] In the auxiliary material stacking structure of pressure transmission, the thickness of PTFE is 0.05mm, which plays a role of release; the thickness of HDPE is 100mm, and the melting point is 140-155℃. It plays an effective role of coating and filling through high temperature melting. The aluminum foil 44 is a hard aluminum foil 4 with a thickness of 0.05mm, which plays a role of leveling in the process of pressure transmission. The steel plate 55 is 5 layers of steel plates between each layer of plates. The thickness of the felt 66 is 4.0mm, which is made of high temperature resistant fiber / base cloth / high temperature resistant fiber. The above PTFE and hard aluminum foil 4 materials can withstand high temperatures of 300-400℃; if it is a single-sided panel, a single-sided coating stacking structure is adopted, that is, HDPE is not used on the side of the non-protective film 100, and HDPE is only used on the adjacent layer of the protective film 100.

[0043] Adopting the existing laminating and pressure-transferring method of the protective film 100 to laminat the protective film 100 with a Tg greater than 200°C will result in poor bonding with the circuit board, leading to problems such as delamination of the circuit board. The layout of the existing auxiliary material stacking structure and the material thickness of each layer of the auxiliary material stacking structure are greatly different from the optimized auxiliary material stacking structure of this application. The existing auxiliary material stacking structure is only suitable for laminating the existing protective film 100 with a Tg less than 100°C. The product protective film 100 may be delaminated and have bubbles, and may also cause problems such as drug seepage and gold seepage in the post-process products, as well as product wrinkles and product mold printing. This application optimizes the pressure-transfer stacking structure and pressure-transfer parameters after the FPC is browned, effectively solving the problems of delamination and bubbles of the product protective film 100, substrate wrinkles, and delamination of gold-seepage drugs.

[0044] The present application performs browning treatment before film lamination, adopts optimized auxiliary material stacking structure, and optimizes the program parameters of each section of the pressure transfer process to perform lamination of the high temperature resistant protective film 100, thereby achieving effective coating and filling of the protective film 100 and the FPC, and effectively solving the problems of stratified bubbles and substrate wrinkles of the protective film 100.

[0045] In a preferred embodiment, in step S4, the total time used for the pressure transfer process is divided into 8 uninterrupted time periods in chronological order, and the 8 time periods respectively have corresponding pressure transfer parameters, and the pressure transfer parameters include pressure transfer temperature, heating time, pressure PSI, pressure rise time and holding time. When the pressure transfer plate is performed, the temperature is raised in sequence from the 1st time period to the 3rd time period, and the temperature is raised in sequence from the 3rd time period to the 8th time period.

[0046] In a preferred embodiment, when the pressure is transmitted and pressed, the pressure corresponding to the second time period to the eighth time period is 500psi, the pressure transmission temperature corresponding to the third time period is 320°C, the heating time corresponding to the third time period is 15min, and the holding time corresponding to the third time period is 90min. The heating and cooling rates of the pressure transmission parameters cannot be too fast, otherwise the thermal expansion and contraction effect will cause wrinkles in the product. Optimize the pressure transmission parameters to solve the problem of stratified bubbles.

[0047] For products with rigid-flex boards, high-frequency pure glue, and special protective film 100, due to the characteristics of the material itself, it is necessary to increase the bonding strength with the FPC copper surface, and the copper surface needs to be browned. Conventional materials only need to be subjected to ordinary micro-etching treatment on the copper surface of the FPC motherboard before applying the protective film 100. The conventional micro-etching amount is about 0.3 to 0.6μm. The rough surface after micro-etching can only meet the basic bonding strength of the product, and it is impossible to achieve good adhesion for the protective film 100 with a high Tg value.

[0048] In a preferred embodiment, the copper surface is browned before the protective film 100 is attached: the browning treatment specifically includes the following steps: micro-etching treatment, water washing, alkali washing, water washing, pre-impregnation activation, browning, water washing, and drying. Among them, water washing is performed after micro-etching treatment, alkali washing and browning treatment, so as to wash away the residual liquid and impurities on the surface of the circuit board by water washing to avoid adverse effects on the next step of the process; a micro-etching tank is set for micro-etching treatment, and the role of micro-etching treatment is to etch and clear the oxide layer on the surface of the circuit board; after removing the surface oxide layer, pre-impregnation activation and browning are performed successively, so as to process the surface of the copper layer into a rough surface, and the amount of micro-etching after treatment is 0.7-1.3μm, and the area combined with the protective film 100, pure glue, PP and other auxiliary materials is larger, and the bonding force will be stronger, which can effectively improve the problems of product stratification, drug penetration, gold penetration caused by insufficient bonding force.

[0049] In a preferred embodiment, in the browning treatment process, the pre-impregnation activation is to immerse the washed copper clad laminate 1 in an activator for (20-30) s for activation, and the browning step is to immerse the activated copper clad laminate 1 in a browning solution for (50-60) s, wherein the browning solution includes a mixture of hydrogen peroxide, sulfuric acid and a browning agent.

[0050] Preferably, the pre-impregnation activation step is to immerse the washed copper clad laminate 1 in an activator for 25 seconds for activation, and the browning step is to immerse the activated copper clad laminate 1 in a browning solution for 60 seconds.

[0051] refer to Figure 1 and Figure 2 In a preferred embodiment, the copper clad laminate 1 includes an insulating layer, a first copper clad layer is provided on the first surface of the insulating layer, a second copper clad layer is provided on the second surface of the insulating layer, and the material of the insulating layer is PI. In step S2, the specific steps of fixing a layer of protective film 100 outside the surface copper layer of the copper clad laminate 1 include: selecting a fixed point on the process edge of the copper clad laminate 1, removing the copper layer at the position of the fixed point, so that the insulating layer is exposed through the copper layer window at the position of the fixed point, and the exposed insulating layer area at the position of the fixed point is the substrate bonding area; superimposing the protective film 100 on the copper clad laminate 1, so that the protective film 100 at the fixed point is in direct contact with the substrate bonding area, and using a thermal bonding device to perform thermal compression bonding between the protective film 100 at the fixed point and the substrate bonding area, so that the protective film 100 is aligned and fixed on the copper clad laminate 1 through the fixed point. The protective film 100 is superimposed and coated on the copper clad laminate 1, so that the protective film 100 at the fixing point is in direct contact with the substrate bonding area, so that the protective film 100 with a high Tg value used in this application can be well fixed on the copper clad laminate 1, and fixed positioning is achieved to avoid displacement before pressure transmission and pressing. No adhesive is needed, which avoids the contamination of the circuit board surface by adhesive, and also avoids the damage to the pressure transmission steel plate caused by the use of mechanical fixing methods such as staples, resulting in problems such as damage to the flatness of the pressure transmission steel plate.

[0052] The high temperature resistant circuit board is prepared by the above method.

[0053] In order to have a further understanding and recognition of the technical solution of the present invention, preferred embodiments are listed and further described in detail.

[0054] Embodiment 1

[0055] like Figure 1 As shown, a pressure transmission method for a high temperature resistant protective film comprises the steps of:

[0056] S1. Using a single-sided copper-clad laminate whose insulating layer is made of PI, the copper surface of the copper-clad laminate to be bonded with a protective film is subjected to a browning treatment process of micro-etching, water washing, alkali washing, water washing, pre-impregnation activation, browning, water washing, and drying in sequence, wherein the copper-clad laminate in the pre-impregnation activation is immersed in the activator for 25 seconds for activation, and the copper-clad laminate in the browning step is immersed in the browning solution for 60 seconds.

[0057] S2, a DuPont HT0100 protective film having a Tg of 233° C. fixed to the surface copper layer of the copper clad laminate after the browning treatment:

[0058] A fixed point is selected on the copper clad laminate, and the copper layer is removed at the position of the fixed point, so that the insulating layer is exposed through the copper layer window at the position of the fixed point, and the exposed insulating layer area at the position of the fixed point is the substrate bonding area; the protective film is superimposed and coated on the copper clad laminate, so that the protective film at the fixed point is in direct contact with the substrate bonding area, and the protective film at the fixed point is thermally pressed with the substrate bonding area using a thermal bonding device, so that the protective film is aligned and fixed on the copper clad laminate through the fixed point.

[0059] S3 stacks the copper clad laminate fixed with a protective film and auxiliary materials in sequence to form a special auxiliary material stack structure; the auxiliary material stack structure includes a copper clad laminate, a first stack and a second stack, the first stack and the second stack are stacked on the first surface and the second surface of the copper clad laminate respectively, the first surface of the copper clad laminate is covered with a protective film, the first stack includes PTFE, HDPE, aluminum foil, steel plate, felt and a carrier, and the second stack includes PTFE, aluminum foil, steel plate, felt and a cover plate.

[0060] S4, set the parameters of the pressure transfer process, and perform the pressure transfer platen so that the protective film is pressed and bonded to the FPC circuit board; divide the total time used for the pressure transfer process into 8 uninterrupted time periods in chronological order, and the 8 time periods have corresponding pressure transfer parameters, and the pressure transfer parameters include pressure transfer temperature, heating time, pressure PSI, pressure rise time and holding time. When performing the pressure transfer platen, the first time period to the third time period are heated in sequence, and the third time period to the eighth time period are heated in sequence. The parameters of the 8 time periods of the pressure transfer process are shown in Table 1 below:

[0061] Table 1

[0062] Number of segments 1 2 3 4 5 6 7 8 temperature 60 250 320 300 280 260 200 40 Heating time 5 35 15 10 10 10 10 25 Pressure PSI 70 500 500 500 500 500 500 500 Ramp-up time 0 0 0 0 0 0 0 0 Keep Time 10 20 90 10 10 5 5 5

[0063] In Table 1, the unit of temperature is (°C); the unit of heating time, pressure increasing time and holding time is (S); and the unit of pressure is (KPa).

[0064] S5. After the pressure transfer and pressing is completed, the board is disassembled to obtain an FPC circuit board with the copper layer surface completely bonded with the DuPont HT0100 protective film with a Tg of 233°C, achieving a good bonding of the high Tg protective film and meeting the requirements of a high heat-resistant circuit board.

[0065] Effect example

[0066] 1. Appearance

[0067] Take the FPC circuit board prepared by the method in Example 1 and attached with the protective film of DuPont HT0100 with a Tg of 233°C, observe the circuit board after disassembly, and evaluate the appearance of the circuit board. The results are shown in Table 2:

[0068] Table 2

[0069]

[0070]

[0071] There is no curling, delamination bubbles, or substrate wrinkles, indicating that the circuit board product obtained by laminating the high Tg value protective film using the present invention has good interlayer bonding strength, and the pressure transfer method of the present application can achieve effective lamination of the high Tg value protective film without causing obvious quality problems.

[0072] 2. Heat resistance test

[0073] Five FPC circuit boards prepared in Example 1 and coated with the protective film of DuPont HT0100 with a Tg of 233° C. were subjected to heat resistance test:

[0074] Open the protective film on the circuit board covered with the protective film to expose the pads of the heating circuit. Use the positive and negative poles of direct current to overlap the pads to form a loop. After power is turned on, the temperature of the circuit board is changed by heating the internal resistance of the circuit board components. By changing the current of the direct current, the temperature of the circuit board rises to 250-320 degrees in turn to conduct heat resistance test:

[0075] (1) Pass current to heat the circuit board so that the internal resistance heating temperature reaches 250-260°C and maintain this temperature for 5 minutes;

[0076] (2) Then, by increasing the DC current, the internal resistance heating temperature reaches 320°C and is maintained for 10 seconds; by changing the DC current, steps (1) and (2) are tested 20 times in a cycle.

[0077] After the heat resistance test, the FPC circuit board was powered off and placed at room temperature for 1 hour. The circuit board was observed and it was found that the surface of the circuit board did not change color due to oxidation.

[0078] In summary, the FPC circuit board prepared by the preparation method of Example 1 can be well bonded to the high Tg protective film, and has good interlayer bonding and heat resistance. When the pressure transmission method of the present application is used to press this type of high temperature resistant protective film product, the protective film can have excellent bonding with the circuit board through specific pressure transmission parameters and pressure transmission stacking, ensuring that the circuit board product has excellent reliability.

[0079] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0080] In the description of this specification, the description with reference to the terms "preferred embodiment", "further embodiment", "other embodiments" or "specific example" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0081] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A pressure transmission method for a high temperature resistant protective film, characterized in that: Includes steps: S1. Browning treatment: Browning treatment is performed on the copper surface of the copper clad laminate to be bonded with the protective film; S2. Positioning and fixing the protective film: a layer of protective film is fixed on the surface copper layer of the copper clad laminate after the browning treatment; the protective film is a thermoplastic PI film, and the Tg of the protective film is greater than 200°C; S3, laying auxiliary materials: stacking the copper clad laminate with the protective film fixed thereon and the auxiliary materials in sequence to form a special auxiliary material stacking structure; S4, setting the parameters of the pressure transfer process, and performing the pressure transfer and pressing, so that the protective film is pressed and bonded to the FPC circuit board; S5. After the pressure transfer and pressing plate is completed, the plate is removed.

2. The pressure transmission method according to claim 1, characterized in that: The Tg value of the protective film is 233°C.

3. The pressure transmission method according to claim 2, characterized in that: The copper clad laminate comprises an insulating layer, a first copper clad layer is provided on a first surface of the insulating layer, a second copper clad layer is provided on a second surface of the insulating layer, and the insulating layer is made of PI. In step S2, the specific steps of fixing a protective film on the surface copper layer of the copper clad laminate include: Select a fixed point on the process edge of the copper clad laminate, remove the copper layer at the position of the fixed point, so that the insulating layer is exposed through the copper layer window at the position of the fixed point, and the exposed insulating layer area at the position of the fixed point is the substrate bonding area; The protective film is overlapped and laid on the copper-clad laminate so that the protective film at the fixed point is in direct contact with the substrate bonding area, and the protective film at the fixed point is thermally pressed with the substrate bonding area using a thermal bonding device so that the protective film is aligned and fixed on the copper-clad laminate through the fixed point.

4. The pressure transmission method according to claim 1, characterized in that: The copper clad laminate is a single-sided copper clad laminate. In step S3, the auxiliary material stack includes a copper clad laminate, a first laminate and a second laminate, the first laminate and the second laminate are stacked on the first surface and the second surface of the copper clad laminate respectively, the first surface of the copper clad laminate is covered with a protective film, the first laminate includes PTFE, HDPE, aluminum foil, steel plate, felt and a carrier plate, and the second laminate includes PTFE, aluminum foil, steel plate, felt and a cover plate.

5. The pressure transmission method according to claim 1, characterized in that: The copper clad laminate is a double-sided copper clad laminate. In step S3, the auxiliary material stack includes a copper clad laminate, a first laminate and a second laminate. The first laminate is stacked on the first surface of the copper clad laminate, and the second laminate is stacked on the second surface of the copper clad laminate. The first surface and the second surface of the copper clad laminate are respectively covered with protective films. The first laminate includes PTFE, HDPE, aluminum foil, steel plate, felt and a carrier plate, and the second laminate includes PTFE, HDPE, aluminum foil, steel plate, felt and a cover plate.

6. The pressure transmission method according to claim 1, characterized in that: In step S4, the total time used for the pressure transmission process is divided into 8 uninterrupted time periods in chronological order. The 8 time periods have corresponding pressure transmission parameters, including pressure transmission temperature, heating time, pressure PSI, pressure rise time and holding time. When the pressure transmission plate is performed, the temperature is raised in sequence from the 1st time period to the 3rd time period, and the temperature is raised in sequence from the 3rd time period to the 8th time period.

7. The pressure transmission method according to claim 6, characterized in that: When the pressure is transmitted on the pressure plate, the pressures corresponding to the second to eighth time periods are all 500psi, the pressure transmission temperature corresponding to the third time period is 320°C, the heating time corresponding to the third time period is 15min, and the holding time corresponding to the third time period is 90min.

8. The pressure transmission method according to claim 1, characterized in that: The browning treatment specifically includes the following steps: micro-etching, water washing, alkali washing, water washing, pre-immersion activation, browning, water washing, and drying.

9. The pressure transmission method according to claim 8, characterized in that: In the browning treatment process, the pre-impregnation activation is to immerse the washed copper clad laminate in an activator for (20-30) seconds for activation, and the browning step is to immerse the activated copper clad laminate in a browning solution for (50-60) seconds, wherein the browning solution includes a mixture of hydrogen peroxide, sulfuric acid and a browning agent.

10. A high temperature resistant circuit board, characterized in that: The method is as described in any one of claims 1 to 9.

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