Thick copper package circuit board resistant to high salt mist corrosion and preparation method thereof

Abstract

The present application relates to the technical field of electronic packaging materials, and particularly relates to a thick copper packaging circuit board capable of resisting high-salt mist corrosion and a preparation method thereof, which comprises the following steps: S1: preparing a glass fiber-BT resin composite core layer for standby; S2: preparing a fluorine-modified polyimide packaging coating solution for standby; S3: preparing a surface corrosion-resistant composite coating for standby; S4: bonding the thick copper foil and the glass fiber-BT composite core layer to obtain a thick copper conductor; S5: applying the fluorine-modified polyimide packaging coating solution to the surface of the thick copper conductor layer to form a packaging layer; S6: spraying the corrosion-resistant coating on the surface of the packaging layer to form a composite corrosion-resistant coating; and S7: performing overall curing and hot pressing to finally obtain a thick copper packaging circuit board product. According to the present application, a multi-layer synergistic protection structure is constructed and the preparation process is optimized, so that the corrosion resistance and structural stability of the thick copper circuit board in a high-salt mist environment are significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic packaging materials, and in particular to a thick copper packaging circuit board resistant to high-salt-mist corrosion and a preparation method thereof. BACKGROUND

[0002] In high-power electronics, electric vehicles, power conversion equipment and other high-load scenarios, circuit boards bear the dual functional requirements of large current and high-density wiring; thick copper packaging circuit boards are widely used in the above-mentioned fields due to their excellent electrical conductivity and thermal load capacity; however, as their application environment expands to extreme conditions such as high humidity, high salt mist and high temperature, the long-term service reliability of the circuit boards is severely challenged; in order to cope with the continuous erosion of external corrosive media, packaging coatings, corrosion-resistant coatings and structural modification methods are gradually introduced in the industry to prolong the service life of the circuit boards and stabilize their performance output.

[0003] However, the existing packaging and protection schemes still have significant deficiencies; on the one hand, the interlayer bonding interface of conventional thick copper boards is weak, and long-term use can easily cause structural failures such as delamination and cracking; on the other hand, traditional packaging coatings and corrosion-resistant films are mostly single-component or low-adhesion systems, which are difficult to provide long-lasting barrier protection in high-salt-mist environments. Therefore, there is an urgent need for a thick copper packaging circuit board resistant to high-salt-mist corrosion and a preparation method thereof to solve the above problems. SUMMARY

[0004] Based on the above purpose, the present application provides a thick copper packaging circuit board resistant to high-salt-mist corrosion and a preparation method thereof.

[0005] A thick copper packaging circuit board resistant to high-salt-mist corrosion, comprising a glass fiber-BT resin composite core layer, a thick copper conductor layer, a fluorine-modified polyimide packaging layer, and a surface corrosion-resistant composite coating.

[0006] Optionally, the fluorine-modified polyimide packaging layer is composed of the following raw materials in mass percentage:

[0007] Fluorinated polyimide resin accounts for 65-75%;

[0008] Nano-aluminum oxide accounts for 8-12%;

[0009] Polytetrafluoroethylene micro powder accounts for 3-6%;

[0010] Gamma-aminopropyl triethoxysilane accounts for 1-2%,

[0011] The balance is a mixed solvent of toluene and NMP;

[0012] The surface corrosion-resistant composite coating is composed of the following components in mass percentage:

[0013] Silane coupling agent accounts for 25-35%;

[0014] Organic zirconium salt accounts for 30-40%;

[0015] Polyvinyl butyral accounts for 8-15%;

[0016] Antioxidant 1010 accounts for 5-10%,

[0017] The rest is xylene.

[0018] A preparation method of a thick copper packaging circuit board resistant to high salt mist corrosion, comprising the following steps:

[0019] S1: BT resin and glass fiber cloth are premixed in a predetermined ratio, and a hot melt impregnation and pressing process is adopted to prepare a glass fiber-BT composite core layer for standby;

[0020] S2: A fluorine-modified polyimide packaging layer material is prepared, fluorinated polyimide resin, nano-aluminum oxide, polytetrafluoroethylene powder and silane coupling agent are sequentially added to a mixed solvent of toluene and NMP, and uniformly dispersed under stirring to form a packaging coating liquid for standby;

[0021] S3: A surface corrosion-resistant composite coating material is prepared, silane coupling agent, organic zirconium salt, polyvinyl butyral and antioxidant 1010 are sequentially added to a xylene solvent, and uniformly stirred to form a corrosion-resistant composite coating for standby;

[0022] S4: The thick copper foil after roughening treatment is attached to the glass fiber-BT composite core layer prepared in S1 by hot pressing lamination to obtain a thick copper conductor;

[0023] S5: The fluorine-modified polyimide packaging coating liquid prepared in S2 is uniformly applied to the surface of the thick copper conductor layer, dried and heat cured to form a packaging layer;

[0024] S6: The corrosion-resistant coating prepared in S3 is sequentially applied to the surface of the packaging layer in the form of spraying to form a composite corrosion-resistant coating;

[0025] S7: The circuit board after completing the construction of each layer is cured and hot-pressed flat at a preset temperature to finally obtain a thick copper packaging circuit board product.

[0026] Optionally, S1 specifically comprises:

[0027] S11: The BT resin is uniformly spread on the surface of the glass fiber cloth in a spread state to form a resin covering layer, and the mass ratio of the BT resin powder to the glass fiber cloth is 6:4;

[0028] S12: The glass fiber cloth covered with resin is sent to a hot melt impregnation device and heated at a temperature of 180-200 DEG C, so that the BT resin melts and penetrates into the fiber gap under heating to form a semi-cured sheet material in which the resin is fully impregnated.

[0029] S13: The prepreg is hot-pressed in a pressing device at a pressure of 0.8-1.2 MPa, a temperature of 200-220℃, and a time of 90-120 seconds to obtain a glass fiber-BT composite core layer with a thickness of 0.2-0.4 mm.

[0030] Optionally, the S2 specifically comprises:

[0031] S21: A mixed solvent is prepared by mixing toluene and NMP at a mass ratio of 3:2 in a stirring reaction kettle, and the mixed solvent is heated to 40℃ for standby;

[0032] S22: The fluorinated polyimide resin is added to the heated solvent, the stirring speed is maintained at 600-800 rpm, and the preliminary sol is pre-dissolved under constant temperature conditions for 20-30 minutes to form a homogeneous suspension system;

[0033] S23: The nano-aluminum oxide, polytetrafluoroethylene powder, and γ-aminopropyl triethoxysilane are sequentially added, and the stirring speed is increased to 900-1000 rpm, and the homogeneous suspension system is continuously dispersed at 60℃ for 50-60 minutes;

[0034] S24: After dispersion is completed, stand for 30 minutes to remove bubbles to obtain a fluorine-modified polyimide encapsulation coating solution.

[0035] Optionally, the S3 specifically comprises:

[0036] S31: A xylene solvent is added to a stirring reaction vessel, and the initial temperature is controlled at 25-30℃, and the stirring speed is set at 500-600 rpm;

[0037] S32: The silane coupling agent and organic zirconium salt are sequentially added, and stirring is continued for 20-30 minutes;

[0038] S33: Then, polyvinyl butyral and antioxidant 1010 are added, and the stirring speed is increased to 800-900 rpm, and the composite solution is continuously stirred at 40-50℃ for 30-40 minutes to form a composite solution;

[0039] S34: The composite solution is filtered through a 100 mesh filter to remove unsolved particles to obtain a corrosion-resistant composite coating.

[0040] Optionally, the S4 specifically comprises:

[0041] S41: An electrolytic copper foil with a thickness of 200-400 μm is subjected to roughening treatment using a chemical micro-etching solution, and the rough etching time is controlled at 30-60 seconds, and the surface roughness Ra of the copper foil after treatment is 0.8-1.5 μm;

[0042] S42: clean the roughened copper foil surface with deionized water, and perform hot air drying treatment at 80-100°C to remove surface residual liquid and moisture;

[0043] S43: laminate the glass fiber-BT composite core layer prepared in S1 and the roughened copper foil in a hot press, set the pressing temperature to 190-210°C, the pressure to 1.0-1.5 MPa, and the pressure holding time to 120-180 seconds, and form a thick copper conductor structure with stable combination of the copper foil and the core layer after cooling to room temperature.

[0044] Optionally, the S5 specifically includes:

[0045] S51: apply the fluorine-modified polyimide encapsulation coating solution prepared in S2 to the surface of the thick copper conductor layer through a coating machine, and control the application speed to be 200-300 mm / s;

[0046] S52: send the coated circuit board into a hot air drying oven, set the drying temperature to be 80-100°C, and the time to be 5-10 minutes, so as to remove the residual solvent and preliminarily shape the coating film;

[0047] S53: place the dried sample in a hot press furnace for heat curing treatment, set the curing temperature to be 220-250°C, and the holding time to be 30-40 minutes, so as to form a cured encapsulation layer with a thickness of 15-20 μm.

[0048] Optionally, the S6 specifically includes:

[0049] S61: uniformly spray the corrosion-resistant composite coating prepared in S3 on the surface of the fluorine-modified polyimide encapsulation layer, set the nozzle aperture to be 0.3-0.5 mm, the spraying air pressure to be 0.2-0.3 MPa, and the spraying distance to be 150-200 mm, cover the entire surface in a spiral trajectory to form the first coating layer, and control the initial film thickness to be 4-6 μm;

[0050] S62: after the first spraying is completed, perform hot air pre-drying at 70-80°C, and the drying time is 5-8 minutes;

[0051] S63: repeat the second spraying process, and arrange the application trajectory staggered with the first one, control the coating film thickness to be 3-5 μm, repeat the drying step S62 again after completion, and form a composite corrosion-resistant coating layer with a final film thickness of 7-11 μm;

[0052] S64: place the sprayed circuit board in an environment at 50-60°C for 2-3 hours for curing.

[0053] Optionally, the S7 specifically includes:

[0054] S71: Place the circuit board sprayed in S6 into a constant temperature hot pressing platform, set the initial heating rate to 2-3℃ / min, and gradually heat to 150-160℃;

[0055] S72: After the temperature is stable, constant hot pressing is applied, the pressure is controlled at 0.5-0.8MPa, and the hot pressing time is maintained for 30-40 minutes;

[0056] S73: After hot pressing is completed, the circuit board is slowly cooled to room temperature under the condition of not removing the pressure, the cooling rate is controlled at 1-2℃ / min, and after the temperature is lower than 40℃, the pressure is removed and the board is taken out, to obtain a thick copper packaging circuit board finished product.

[0057] Advantages of the present application:

[0058] The present application, by sequentially constructing a fluorine modified polyimide packaging layer and a multi-component composite corrosion resistant coating layer outside the thick copper conductor structure, forms a multi-layer synergistic protection system, significantly enhances the corrosion resistance of the circuit board in a high salt spray and high humidity environment; wherein the fluorinated polyimide and the nano filler cooperatively construct a dense packaging film layer, which has excellent insulation and interface stability; the corrosion resistant coating layer is designed by compounding silane, organic zirconium salt and high molecular film forming agent, which can effectively block the corrosion medium and improve the surface chemical corrosion resistance.

[0059] The present application, by in-situ preparation of packaging and corrosion resistant coating liquid, and by using staged application, heat curing and hot pressing leveling process, makes the structure layers of the circuit board realize heat solidification synchronization, stress coordination and interface stability, effectively solves the problems of weak interface adhesion, uneven film formation and size deformation in traditional process, thereby significantly improves the structural integrity, service life and batch production stability of the thick copper circuit board. BRIEF DESCRIPTION OF DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only illustrate the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0061] Figure 1 The thick copper packaging circuit board preparation method of the present application is shown in the figure. DETAILED DESCRIPTION

[0062] The application will be described in detail below with reference to the drawings and specific embodiments. It should be noted that, in order to make the embodiments more detailed, the following embodiments are the best, preferred embodiments, and other alternative ways can also be used by those skilled in the art to implement them; and the drawings are only used to more specifically describe the embodiments, and are not intended to specifically limit the application.

[0063] It should be noted that in the specification, "one embodiment", "embodiment", "exemplary embodiment", "some embodiments" and the like indicate that the described embodiment can include a specific feature, structure or property, but not necessarily every embodiment includes the specific feature, structure or property. In addition, when a specific feature, structure or property is described in combination with an embodiment, it should be within the knowledge of those skilled in the related art to implement such a feature, structure or property in combination with other embodiments (whether or not explicitly described).

[0064] Generally, the terms can be understood at least in part from the context of their usage. For example, depending at least in part upon the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in the singular or can be used to describe combinations of features, structures, or characteristics, in the plural, both singularly and in combination. Additionally, the term "based on" can be understood as not necessarily requiring exclusively derived from that which is stated, but instead can allow for being based on a combination of explicitly and inexplicitly described factors.

[0065] Embodiment 1

[0066] A high-salt-fog-corrosion-resistant thick copper packaging circuit board comprises a glass fiber-BT resin composite core layer, a thick copper conductor layer, a fluorine-modified polyimide packaging layer, and a surface corrosion-resistant composite coating.

[0067] The fluorine-modified polyimide packaging layer is composed of the following raw materials in mass percentage:

[0068] The fluorinated polyimide resin accounts for 78%;

[0069] The nano-aluminum oxide accounts for 10%;

[0070] The polytetrafluoroethylene micro powder accounts for 5%;

[0071] The γ-aminopropyl triethoxysilane accounts for 1.5%,

[0072] The balance is a mixed solvent of toluene and NMP;

[0073] The surface corrosion-resistant composite coating is composed of the following components in mass percentage:

[0074] The silane coupling agent accounts for 30%;

[0075] The organic zirconium salt accounts for 35%;

[0076] Polyvinyl butyral accounts for 10%;

[0077] Antioxidant 1010 accounts for 7%;

[0078] The balance is xylene.

[0079] As shown in Figure 1 A preparation method of a thick copper packaging circuit board resistant to high-salt mist corrosion, comprising the following steps:

[0080] S1: Pre-mix BT resin and glass fiber cloth in a predetermined ratio, and use hot melt impregnation and pressing process to make a glass fiber-BT composite core layer for standby;

[0081] S2: Prepare a fluorine-modified polyimide packaging layer material, add fluorinated polyimide resin, nano-aluminum oxide, polytetrafluoroethylene powder and silane coupling agent into a mixed solvent of toluene and NMP in sequence, and uniformly disperse under stirring to form a packaging coating liquid for standby;

[0082] S3: Prepare a surface corrosion-resistant composite coating material, add silane coupling agent, organic zirconium salt, polyvinyl butyral and antioxidant 1010 into a xylene solvent in sequence, and uniformly stir to form a corrosion-resistant composite coating for standby;

[0083] S4: Bond the thick copper foil after roughening treatment with the glass fiber-BT composite core layer made in S1 by hot pressing lamination to obtain a thick copper conductor;

[0084] S5: Uniformly apply the fluorine-modified polyimide packaging coating liquid prepared in S2 to the surface of the thick copper conductor layer, dry and heat cure to form a packaging layer;

[0085] S6: Apply the corrosion-resistant coating prepared in S3 to the surface of the packaging layer in sequence by spraying to form a composite corrosion-resistant coating;

[0086] S7: Cure and hot-press the circuit board after completing the construction of each layer at a preset temperature to obtain a thick copper packaging circuit board product.

[0087] S1 specifically includes:

[0088] S11: Uniformly spread BT resin on the surface of the glass fiber cloth in a spread state to form a resin covering layer, and the mass ratio of BT resin powder to glass fiber cloth is 6:4;

[0089] S12: Put the glass fiber cloth covered with resin into a hot melt impregnation device, heat at a temperature of 190 DEG C, and make the BT resin melt and penetrate into the fiber gap under heating to form a semi-cured sheet material with fully impregnated resin;

[0090] S13: The prepreg is hot-pressed in a pressing device at a pressure of 1.0 MPa, a temperature of 210°C, and a time of 100 seconds to obtain a glass fiber-BT composite core layer with a thickness of 0.3 mm; the above step can ensure uniform distribution of the resin in the fiber, form a core layer with a dense structure and stable dielectric properties, and help improve the interfacial bonding force of the subsequent copper layer bonding and the overall thermal stability and mechanical strength of the circuit board.

[0091] S2 specifically comprises:

[0092] S21: In a stirred reaction kettle, mixed toluene and NMP at a mass ratio of 3:2 to obtain a mixed solvent, and the mixed solvent is heated to 40°C for standby;

[0093] S22: The fluorinated polyimide resin is added to the heated solvent, the stirring speed is maintained at 700 rpm, and it is pre-dissolved for 25 minutes under constant temperature conditions to form a preliminary sol state;

[0094] S23: Nano-alumina, polytetrafluoroethylene powder and gamma-aminopropyl triethoxysilane are sequentially added, and the stirring speed is increased to 950 rpm, and the homogeneous suspension system is formed by continuously dispersing at 60°C for 55 minutes;

[0095] S24: After dispersion, stand for 30 minutes to remove bubbles, and obtain a fluorine-modified polyimide encapsulation coating liquid; the above step can effectively improve the interfacial compatibility of the nano-filler and the resin system by controlling the order of adding raw materials and the dispersion temperature conditions in sequence, avoid particle agglomeration, ensure good leveling and uniform film formation of the encapsulation coating liquid in the subsequent application process, thereby providing a basis for forming a dense and uniform high-performance encapsulation layer.

[0096] S3 specifically comprises:

[0097] S31: In a stirred reaction vessel, add xylene solvent, and control the initial temperature to be 27°C, and set the stirring speed to be 550 rpm;

[0098] S32: Silane coupling agent and organic zirconium salt are sequentially added, and continue to stir for 25 minutes to ensure uniform dissolution of the zirconium-based complex and silane;

[0099] S33: Then add polyvinyl butyral and antioxidant 1010, and increase the stirring speed to 850 rpm, continue to stir at 45°C for 35 minutes to form a composite solution;

[0100] S34: The composite solution is filtered with a 100-mesh filter to remove unsolved particles, to obtain the anti-corrosion composite coating. The above steps can improve the dissolution efficiency of the organic zirconium salt and the silane material in the solvent system by controlling the addition sequence of different components and the stirring temperature range, avoid the problems of side polymerization or pre-crosslinking, and ensure the uniform distribution of polyvinyl butyl and antioxidants, thereby obtaining an anti-corrosion composite coating with strong interfacial bonding force, good coating continuity and storage stability, to meet the subsequent uniform spraying and film forming requirements.

[0101] S4 specifically includes:

[0102] S41: The electrolytic copper foil with a thickness of 300 μm is roughened by using a chemical micro-etching solution, and the roughening time is controlled to be 40 seconds. The surface roughness Ra of the copper foil after treatment is 1.0 μm;

[0103] S42: The surface of the roughened copper foil is cleaned with deionized water, and hot air drying treatment is carried out at 90°C to remove surface residual liquid and moisture;

[0104] S43: The glass fiber-BT composite core layer prepared in S1 is laminated with the roughened copper foil in a hot press, and the pressing temperature is set to 200°C, the pressure is 1.2 MPa, and the pressure holding time is 160 seconds. After cooling to room temperature, a thick copper conductor structure with stable combination of copper foil and core layer is formed. By roughening the surface of the copper foil before hot pressing, the actual contact area between the copper foil and the BT resin-based core layer can be significantly increased. Combined with the reasonable control of subsequent hot pressing parameters, a firm mechanical locking structure is formed at the copper-resin interface, thereby improving the adhesion stability of the conductor layer.

[0105] S5 specifically includes:

[0106] S51: The fluorine-modified polyimide encapsulation coating solution prepared in S2 is applied to the surface of the thick copper conductor layer by a coating machine, and the application speed is controlled to be 250 mm / s. A cross-bidirectional application method is used to ensure uniform and complete coverage of the surface;

[0107] S52: The coated circuit board is sent into a hot air drying oven, and the drying temperature is set to 90°C for 8 minutes to remove solvent residues and preliminarily set the coating film;

[0108] S53: The dried sample is placed in a hot press furnace for heat curing treatment, and the curing temperature is set to 230°C and the holding time is 35 minutes to form a cured encapsulation layer with a thickness of 18 μm. By controlling the coating thickness and application path, a continuous and uniform film layer of the encapsulation liquid is formed on the surface of the copper conductor. Then, through segmented temperature rising drying and high temperature heat curing, the fluorine-modified polyimide is fully crosslinked to form a film, thereby enhancing the interfacial adhesion and heat resistance stability of the encapsulation layer, and providing excellent barrier protection performance for the circuit board in a high salt mist environment.

[0109] S6 specifically comprises:

[0110] S61: The anti-corrosion composite coating prepared in S3 is uniformly sprayed on the surface of the fluorine-modified polyimide encapsulation layer, the nozzle aperture is set to 0.4 mm, the spraying air pressure is controlled at 0.25 MPa, the spraying distance is 180 mm, the entire surface is covered in a spiral trajectory, the first coating is formed, and the initial film thickness is controlled at 5 μm;

[0111] S62: After the first spraying is completed, hot air pre-drying is performed at 75°C, the drying time is 7 minutes, and stable adhesion of the first layer of coating film is ensured;

[0112] S63: The second spraying process is repeatedly performed, the application trajectory is staggered with the first one, the coating film thickness is controlled at 4 μm, after completion, the drying step S62 is repeated again, and a composite anti-corrosion coating with a final film thickness of 9 μm is formed;

[0113] S64: The circuit board after spraying is placed in an environment at 55°C for 2.5 hours for curing, the stability of the coating structure and the degree of complete solvent evaporation are improved; through two-staggered spraying and staged pre-drying, the anti-corrosion components are orderly distributed in the multi-layer coating film to form a stable laminated structure; combined with the curing step, the coating is fully shaped and the component reaction is completed, thereby obtaining a composite protective coating with strong adhesion and long-lasting salt spray resistance, and the overall chemical corrosion resistance of the circuit board is enhanced.

[0114] S7 specifically comprises:

[0115] S71: The circuit board after spraying completed by S6 is placed in a constant temperature hot pressing platform, the initial heating rate is set to 2.5°C / min, and the temperature is gradually increased to 155°C;

[0116] S72: When the temperature is stable, a constant hot pressing is applied, the pressure is controlled at 0.6 MPa, and the hot pressing time is maintained for 35 minutes to realize the interface hot curing and internal stress release of each layer structure;

[0117] S73: After hot pressing is completed, the circuit board is slowly cooled to room temperature under the condition of not removing the pressure, the cooling rate is controlled at 1.5°C / min, and after the temperature is lower than 40°C, the pressure is removed and the board is taken out to obtain a thick copper encapsulated circuit board finished product; by setting a gentle heating and slow cooling curve and cooperating with a moderate pressure hot pressing time, the synchronous curing of the core layer resin, the encapsulation coating and the anti-corrosion film layer can be effectively completed, and the interface bonding strength and overall flatness of the multi-layer structure are improved.

[0118] Example 2

[0119] The encapsulation layer formula: fluorinated polyimide resin 65%, nano-alumina 8%, polytetrafluoroethylene powder 3%, gamma-aminopropyl triethoxysilane 1%, and the rest is a mixture of toluene and NMP solvent.

[0120] The anti-corrosion coating formula: silane coupling agent 25%, organic zirconium salt 30%, polyvinyl butyral 8%, antioxidant 1010 5%, and the rest is xylene.

[0121] The preparation steps are as follows:

[0122] S1: The BT resin and glass fiber cloth are premixed in a mass ratio of 6:4, and the BT resin is uniformly spread on the surface of the glass fiber cloth in a spread state. Then it is sent to a 180°C heating zone for hot melt impregnation treatment, so that the BT resin fully penetrates the fiber gap to form a semi-cured sheet. The semi-cured sheet is hot pressed at 200°C and 0.8MPa for 90 seconds to obtain a glass fiber-BT composite core layer with a thickness of 0.2mm;

[0123] S2: In a stirred tank, mix toluene and NMP in a mass ratio of 3:2, and heat to 40°C. First, add fluorinated polyimide resin, dissolve for 20 minutes at a stirring rate of 600rpm to form a preliminary sol; then add nano-alumina, polytetrafluoroethylene powder and gamma-aminopropyl triethoxysilane in sequence, increase the stirring speed to 900rpm, continue to disperse at 60°C for 50 minutes, and stand for 30 minutes to remove bubbles to obtain an encapsulation coating liquid;

[0124] S3: Add xylene to the reactor, set the temperature to 25°C, and control the stirring speed at 500rpm; add silane coupling agent and organic zirconium salt in sequence, stir for 20 minutes, then add polyvinyl butyral and antioxidant 1010, increase the stirring speed to 800rpm and heat to 40°C, continue to stir for 30 minutes, and finally remove impurities with a 100 mesh filter to obtain an anti-corrosion composite coating;

[0125] S4: Take an electrolytic copper foil with a thickness of 200μm, perform roughening treatment with a chemical micro-etching solution for 30 seconds to control the surface roughness Ra to 0.8μm; then rinse with deionized water and dry under 80°C hot air; heat press the treated copper foil and the core layer prepared in S1 at 190°C and 1.0MPa for 120 seconds and cool to form a thick copper conductor structure;

[0126] S5: Apply the encapsulation coating liquid uniformly to the surface of the copper conductor by a film applicator at a speed of 200mm / s; send it into an 80°C hot air oven to dry for 5 minutes to remove the solvent; then send it into a hot press furnace for thermal curing at 220°C for 30 minutes to finally form a cured encapsulation layer with a thickness of 15μm;

[0127] S6: The first coating was sprayed in a spiral manner using a nozzle with a caliber of 0.3 mm, an air pressure of 0.2 MPa, and a spraying distance of 150 mm, with the film thickness controlled at 4 μm; then hot air drying was performed at 70 °C for 5 minutes; the second spraying was performed with the tracks staggered, the film thickness was controlled at 3 μm, the drying step was repeated, and the final film thickness was 7 μm; the sprayed plate was placed in an environment at 50 °C for 2 hours for curing;

[0128] S7: The circuit board was placed on a constant temperature hot pressing platform, the temperature was raised at a rate of 2 °C / min, and when the temperature reached 150 °C, a constant pressure of 0.5 MPa was applied and maintained for 30 minutes; after completion, the temperature was lowered to 40 °C at a cooling rate of 1 °C / min without removing the pressure, the pressure was removed, and the circuit board was taken out, and the final product was obtained.

[0129] Example 3

[0130] The encapsulation layer formula: fluorinated polyimide resin 75%, nano-alumina 12%, polytetrafluoroethylene powder 6%, γ-aminopropyl triethoxysilane 2%, and the rest is a mixed solvent of toluene and NMP.

[0131] The anticorrosion coating formula: silane coupling agent 35%, organic zirconium salt 40%, polyvinyl butyral 15%, antioxidant 1010 10%, and the rest is xylene.

[0132] The preparation steps are as follows:

[0133] S1: The BT resin and glass fiber cloth were premixed in a mass ratio of 6:4, the BT resin was uniformly spread on the surface of the glass fiber cloth in a spread state; then it was sent into a 200 °C heating zone for hot melt impregnation treatment, so that the BT resin fully penetrated into the fiber gap to form a semi-cured sheet; the semi-cured sheet was hot pressed at 220 °C and 1.2 MPa for 120 seconds to obtain a glass fiber-BT composite core layer with a thickness of 0.4 mm;

[0134] S2: In a stirred tank, mix toluene and NMP in a mass ratio of 3:2, and heat to 40 °C; first add fluorinated polyimide resin, dissolve for 30 minutes at a stirring rate of 800 rpm to form a preliminary sol; then add nano-alumina, polytetrafluoroethylene powder, and γ-aminopropyl triethoxysilane in sequence, increase the stirring to 1000 rpm, continue to disperse at 60 °C for 60 minutes, and after standing for 30 minutes to degas, obtain the encapsulation coating liquid;

[0135] S3: Add xylene to the reactor, set the temperature to 30 °C, and control the stirring rate at 600 rpm; add silane coupling agent and organic zirconium salt in sequence, stir for 30 minutes, then add polyvinyl butyral and antioxidant 1010, increase the stirring rate to 900 rpm and heat to 50 °C, continue to stir for 40 minutes, and finally remove the impurities with a 100 mesh filter to obtain the anticorrosion composite coating;

[0136] S4: Take the thickness of 400 μm of electrolytic copper foil, using chemical micro-etching solution for roughening treatment for 60 seconds, control the surface roughness Ra to be 1.5 μm; then use deionized water to rinse and dry under 100℃ hot air; after the treatment of copper foil and S1 prepared core layer at 210℃, 1.5 MPa hot pressing for 180 seconds, cooling, forming thick copper conductor structure;

[0137] S5: Through the uniform coating machine to uniformly apply the packaging coating liquid on the surface of the copper conductor at a speed of 300 mm / s; send into the 100℃ hot air oven to dry for 10 minutes to remove the solvent; then send into the hot pressing furnace to heat cure at 250℃ for 40 minutes, finally form a solidified packaging layer with a thickness of 20 μm;

[0138] S6: Use a nozzle with a caliber of 0.5 mm, air pressure of 0.3 MPa, and spraying distance of 200 mm to spray the first coating layer in a spiral manner, with the film thickness controlled at 6 μm; then dry under hot air at 80℃ for 8 minutes; perform the second spraying, with the tracks staggered, the film thickness controlled at 5 μm, and the drying step repeated, finally the film thickness is 11 μm; place the sprayed board in a 60℃ environment for 3 hours of curing;

[0139] S7: Place the circuit board on the constant temperature hot pressing platform, with the heating rate of 3℃ / min, rise to 160℃, then apply a constant pressure of 0.8 MPa, maintain for 40 minutes; after completion, cool down to 40℃ without removing the pressure, with the cooling rate controlled at 2℃ / min, remove the pressure and take out the circuit board, obtain the final product.

[0140] Comparative Example 1

[0141] Step 1: Dip the glass fiber cloth into the BT resin and dry it into a semi-cured sheet, and then hot press it with an electrolytic copper foil with a thickness of 200 μm, the pressing temperature is set to 180℃, the pressing pressure is 1.0 MPa, and the pressing time is 90 seconds, to obtain a copper foil laminated substrate;

[0142] Step 2: Use an alkaline etching solution to perform pattern transfer and etching on the surface of the copper foil, control the etching depth to be about 50 μm, to obtain a circuit structure; then rinse the residual liquid with pure water at 80℃ and dry it with hot air;

[0143] Step 3: Uniformly spray a conventional acrylic three-protection paint on the surface of the circuit board, control the coating film thickness to be 3-5 μm, dry it at 80℃ for 10 minutes, to obtain the finished product.

[0144] Table 1 Comparison of performance parameters of finished products

[0145] Performance item Unit Example 1 Example 2 Example 3 Comparative Example 1 Packaging layer thermal decomposition temperature ℃ 465 452 470 380 Surface protective coating adhesion (crosshatch test) Level 0 1 0 3 Salt spray corrosion blistering time (5% NaCl, 35°C) h ≥1000 800 950 ≤120 Insulation resistance GΩ 10.5 9.2 10.1 4.6 Surface conductivity (after damp heat) μS / cm 0.08 0.1 0.09 0.25 Conductor layer peel strength N / cm 1.6 1.45 1.52 1.1 Packaging layer dielectric strength kV / mm 35 30 34 21 Line width retention rate (after high temperature aging) % 98.7 96.5 97.8 88.4 Cold-heat shock cycle life (-40~+125°C) Times ≥600 450 550 120

[0146] From the above Table 1, it can be seen that Example 1 is the best in terms of thermal stability, with a high proportion of fluorinated polyimide and sufficient dispersion, forming a packaging layer with a heat decomposition temperature of 465°C, better than other schemes, and the maximum dielectric strength (35 kV / mm) ensures the electrical safety performance at high temperature; Example 1 has no corrosion and blistering time in 5% NaCl environment for more than 1000 hours, much higher than 120 hours of Comparative Example 1, indicating that its composite corrosion-resistant coating is more effective in thickness, compactness and hydrophilic interface inhibition; The conductor layer peeling strength and the adhesion of the packaging layer are better than the conventional scheme, and the multi-component fluorine-modified packaging layer of Example 1 provides stronger mechanical bonding force to ensure that the circuit board does not delaminate during long-term use; The electrical insulation performance and cold-heat cycle life of Example 1 are the best, reflecting that its overall structural stability is stronger and its ability to adapt to extreme environmental changes is better than Example 2 and Example 3; Comparative Example 1, as a representative of conventional technology, performs the worst in almost all performance indicators and cannot meet the needs of high reliability and high corrosion environment applications. Example 1 is superior to other examples and Comparative Example 1 in high-temperature insulation, corrosion resistance stability and interface adhesion performance, and is the most suitable preparation scheme for thick copper packaging circuit board in high-salt mist and high-temperature complex environments.

[0147] Table 2 Comparison of other performance parameters

[0148] Comparative item Unit Example 1 Example 2 Example 3 Comparative Example 1 Packaging layer surface roughness Ra (after curing) μm 0.35 0.42 0.4 0.75 Thermal expansion coefficient (Z-axis direction) ppm / °C 28 31 29 45 Coating thickness uniformity (standard deviation) μm ±0.4 ±0.7 ±0.6 ±1.2 Copper-packaging layer interface shear strength MPa 27.5 24.3 26.1 18.6 Circuit board warpage rate (after hot pressing) mm / m 0.3 0.6 0.4 1.2 Process residual rate (non-soluble component deposition residue) % 0.2 0.4 0.3 1.1 One-time pass rate of board making % 98.8 95.3 97.2 87.5

[0149] From the above Table 2, it can be seen that the surface roughness of Example 1 is the lowest (0.35 μm) and the standard deviation of the coating thickness is the smallest (±0.4 μm), indicating that the composition ratio and dispersion process of the coating liquid are more reasonable, forming a denser and more uniform coating, which is beneficial to electrical insulation and subsequent pattern processing; The thermal expansion coefficient is only 28 ppm / °C, which is much better than the 45 ppm / °C of Comparative Example 1, which can effectively reduce the risk of warping, cracking and conductor deformation caused by thermal shock, and improve the thermal dimensional stability; The interface shear strength reaches 27.5 MPa, which is much higher than the 18.6 MPa of Comparative Example 1, which reflects the strong adhesion of the packaging layer to the copper conductor, ensuring that the packaging structure does not delaminate under high humidity conditions; The overall warpage rate of the circuit board is only 0.3 mm / m, which is significantly better than the comparative example, meeting the high-density component assembly and large board size requirements; The one-time pass rate of the board reaches 98.8%, showing strong process control capability and more stability and economy in batch production. In summary, Example 1 performs the best in terms of packaging layer uniformity, dimensional stability and interface bonding strength, and is the preferred scheme to ensure high reliability and high batch consistency of thick copper packaging circuit boards.

[0150] The present application encompasses any alternatives, modifications, equivalent methods and solutions made to the essence and scope of the present application. In order to make the public have a thorough understanding of the present application, specific details are described in the following preferred embodiments of the present application, and the present application can also be fully understood without the description of these details to those skilled in the art. In addition, in order to avoid unnecessary confusion to the essence of the present application, well-known methods, processes, procedures, elements and circuits, etc. are not described in detail.

[0151] The above is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can also be made, which should be considered as the protection scope of the present application.

Claims

1. A thick copper package printed circuit board which is resistant to high salt spray corrosion, characterized by, The glass fiber-BT resin composite core layer, thick copper conductor layer, fluorine modified polyimide encapsulation layer and surface corrosion-resistant composite coating are included. The fluorine modified polyimide encapsulation layer is composed of the following raw materials in percentage by mass: The fluorinated polyimide resin accounts for 65-75%; The nano-aluminum oxide accounts for 8-12%; The polytetrafluoroethylene micro powder accounts for 3-6%; The gamma-aminopropyl triethoxysilane accounts for 1-2%, and the balance is a mixed solvent of toluene and NMP; The surface corrosion-resistant composite coating is composed of the following components in percentage by mass: The silane coupling agent accounts for 25-35%; The organic zirconium salt accounts for 30-40%; The polyvinyl butyral accounts for 8-15%; The antioxidant 1010 accounts for 5-10%, and the balance is xylene. The following steps are included: S1: The BT resin and the glass fiber cloth are premixed in a predetermined ratio, and a hot melt impregnation and pressing process is adopted to prepare a glass fiber-BT composite core layer for standby; 2. The method for preparing the thick copper package circuit board resistant to high salt mist corrosion, for preparing the thick copper package circuit board resistant to high salt mist corrosion according to claim 1, wherein S2: The fluorine modified polyimide encapsulation layer material is prepared, the fluorinated polyimide resin, nano-aluminum oxide, polytetrafluoroethylene micro powder and silane coupling agent are sequentially added to the mixed solvent of toluene and NMP, and uniformly dispersed under stirring to form an encapsulation coating liquid for standby; S3: The surface corrosion-resistant composite coating material is prepared, the silane coupling agent, organic zirconium salt, polyvinyl butyral and antioxidant 1010 are sequentially added to the xylene solvent, and uniformly stirred to form a corrosion-resistant composite coating for standby; S4: The thick copper foil after roughening treatment is bonded with the glass fiber-BT composite core layer prepared in S1 by hot pressing lamination to obtain a thick copper conductor; S5: The fluorine modified polyimide encapsulation coating liquid prepared in S2 is uniformly applied to the surface of the thick copper conductor layer, dried and heat cured to form an encapsulation layer; S6: The corrosion-resistant coating prepared in S3 is sequentially applied to the surface of the encapsulation layer by spraying to form a composite corrosion-resistant coating; S7: The circuit board after completing the construction of each layer is subjected to overall curing and hot pressing flattening at a predetermined temperature to finally obtain a thick copper encapsulation circuit board product. The S1 specifically includes: S11: The BT resin is uniformly spread on the surface of the glass fiber cloth in a spread state to form a resin covering layer, and the mass ratio of the BT resin powder to the glass fiber cloth is 6:4; 3. The method for preparing a thick copper packaged circuit board resistant to high salt spray corrosion according to claim 2, characterized in that, S12: The glass fiber cloth covered with resin is sent into a hot melt impregnation device, heated at a temperature of 180-200℃, and the BT resin is melted and penetrated into the interstitial space of the fibers under heating to form a semi-cured sheet material with fully impregnated resin; S13: The semi-cured sheet material is subjected to hot pressing curing in a pressing equipment under the conditions of a pressure of 0.8-1.2 MPa, a temperature of 200-220℃ and a time of 90-120 seconds to obtain a glass fiber-BT composite core layer with a thickness of 0.2-0.4 mm. The S2 specifically includes: S21: In a stirring reaction kettle, toluene and NMP are mixed in a mass ratio of 3:2 to prepare a mixed solvent, and the mixed solvent is heated to 40℃ for standby; 4. The method for preparing a thick copper packaged circuit board resistant to high salt spray corrosion according to claim 2, characterized in that, S22: The fluorinated polyimide resin is added to the heated solvent, the stirring speed is maintained at 600-800 rpm, and it is pre-dissolved for 20-30 minutes under constant temperature conditions to form a preliminary sol state; ​ ​ S23: Add nano-aluminum oxide, polytetrafluoroethylene powder and gamma-aminopropyl triethoxysilane in sequence, and increase the stirring speed to 900-1000 rpm, and continue to disperse at 60°C for 50-60 minutes to form a homogeneous suspension system; S24: After dispersion, stand for 30 minutes to remove bubbles, and obtain a fluorine-modified polyimide encapsulation coating solution.

5. The method for preparing a thick copper packaged circuit board resistant to high salt spray corrosion according to claim 2, characterized in that, The S3 specifically comprises: S31: Add dimethylbenzene solvent in the stirring reaction container, and control the initial temperature to be 25-30°C, and set the stirring speed to be 500-600 rpm; S32: Add silane coupling agent and organic zirconium salt in sequence, and continue to stir for 20-30 minutes; S33: Then add polyvinyl butyral and antioxidant 1010, and increase the stirring speed to 800-900 rpm, and continue to stir at 40-50°C for 30-40 minutes to form a composite solution; S34: Filter the composite solution through a 100 mesh filter to remove unsolved particles to obtain a corrosion-resistant composite coating.

6. The method for preparing a thick copper packaged circuit board resistant to high salt spray corrosion according to claim 2, characterized in that, The S4 specifically comprises: S41: Coarsen the electrolytic copper foil with a thickness of 200-400 μm using a chemical micro-etching solution, and control the coarsening time to be 30-60 seconds, and the surface roughness Ra of the copper foil after treatment is 0.8-1.5 μm; S42: Clean the surface of the coarsened copper foil with deionized water, and perform hot air drying treatment at 80-100°C to remove surface residual liquid and moisture; S43: Laminate the glass fiber-BT composite core layer prepared in S1 and the coarsened copper foil in a hot press, set the pressing temperature to be 190-210°C, the pressure to be 1.0-1.5 MPa, and the pressure holding time to be 120-180 seconds, and after cooling to room temperature, form a thick copper conductor structure in which the copper foil and the core layer are stably combined.

7. The method for preparing a thick copper packaged circuit board resistant to high salt spray corrosion according to claim 2, characterized in that, The S5 specifically comprises: S51: Apply the fluorine-modified polyimide encapsulation coating solution prepared in S2 to the surface of the thick copper conductor layer through a coating machine, and control the application speed to be 200-300 mm / s; S52: Send the coated circuit board into a hot air drying oven, set the drying temperature to be 80-100°C, and the time to be 5-10 minutes to remove solvent residues and preliminarily shape the coating film; S53: Place the dried sample in a hot press furnace for heat curing treatment, set the curing temperature to be 220-250°C, and the holding time to be 30-40 minutes to form a cured encapsulation layer with a thickness of 15-20 μm.

8. The method for preparing a thick copper packaged circuit board resistant to high salt spray corrosion according to claim 2, characterized in that, The S6 specifically comprises: S61: Uniformly spray the corrosion-resistant composite coating prepared in S3 on the surface of the fluorine-modified polyimide encapsulation layer, set the nozzle aperture to be 0.3-0.5 mm, control the spraying air pressure to be 0.2-0.3 MPa, and the spraying distance to be 150-200 mm, cover the entire surface in a spiral trajectory to form the first coating layer, and control the initial film thickness to be 4-6 μm; S62: After the first spraying is completed, perform hot air pre-drying at 70-80°C for 5-8 minutes; S63: repeat the second spraying process, the application track is staggered with the first one, the coating film thickness is controlled at 3-5 μm, after completion, repeat the drying step of S62 again, to form a composite anticorrosion coating with a final film thickness of 7-11 μm; S64: place the completed spraying circuit board in an environment of 50-60 ℃ for 2-3 hours for curing.

9. The method for preparing a thick copper packaged circuit board resistant to high salt spray corrosion according to claim 2, characterized in that, The S7 specifically comprises: S71: place the completed spraying circuit board in a constant temperature hot pressing platform, set the initial heating rate at 2-3 ℃ / min, gradually heat to 150-160 ℃; S72: when the temperature is stable, apply constant hot pressing, the pressure is controlled at 0.5-0.8 MPa, and the hot pressing time is maintained for 30-40 minutes; S73: after the hot pressing is completed, slowly cool the circuit board to room temperature under the condition of not removing the pressure, the cooling rate is controlled at 1-2 ℃ / min, and after the temperature is lower than 40 ℃, the pressure is removed and the board is taken out, to obtain a thick copper packaging circuit board finished product.

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