CN104427755A - Flexible circuit board and manufacturing method thereof - Google Patents

Abstract

A flexible circuit board, which includes a cover film, a conductive circuit pattern, and a first dielectric layer that are sequentially attached to each other. The cover film has at least one opening that passes through the cover film. exposed in the opening, the conductive circuit pattern exposed from the opening forms a solder pad, and a low-temperature solder paste layer is formed on the solder pad, an electronic component is welded to the low-temperature solder paste layer, and the electronic component passes through The low-temperature solder paste layer is electrically connected to the pad, and the first dielectric layer is made of polyethylene naphthalate. The invention also relates to a manufacturing method of the flexible circuit board.

Description

Flexible printed circuit board and its manufacturing method

technical field

The invention relates to the field of manufacturing flexible circuit boards, in particular to a flexible circuit board and a manufacturing method thereof.

Background technique

Due to the personalization of electronic products, the requirements for printed flexible circuit boards used in electronic products are becoming more and more diverse. At present, there is a kind of flexible circuit board. The insulating substrate and protective film layer used to carry and protect the conductive circuit pattern are high light-transmitting materials, so that the internal conductive circuit pattern becomes visible because the insulating material is a high light-transmitting material. Generally, the high light-transmitting insulating substrate and protective film layer material used in the flexible circuit board is polyethylene terephthalate (PET), and the heat resistance of PET material is poor, thus limiting the use of all The scope of application of the flexible circuit board of the above-mentioned PET material, for example, parts cannot be soldered on the flexible circuit board of the PET material.

Contents of the invention

Therefore, it is necessary to provide a flexible circuit board with better heat resistance and its method, so that parts can be soldered on the flexible circuit board.

A method for manufacturing a flexible circuit board, comprising the steps of: providing a copper-clad substrate, the copper-clad substrate comprising a first copper foil layer and a first dielectric layer, wherein the material of the first dielectric layer is polynaphthalene Ethylene glycol diformate; making the first copper foil layer to form a first conductive circuit pattern; forming a cover film on one side of the first conductive circuit pattern, and the cover film has at least one through the cover film an opening, part of the first conductive circuit pattern is exposed from the opening, and the first conductive circuit pattern exposed from the opening forms a solder pad; and a low-temperature solder paste layer is formed on the solder pad, And welding an electronic component to the low-temperature solder paste layer, the electronic component is electrically connected to the welding pad through the low-temperature solder paste layer, thereby obtaining a flexible circuit board.

A flexible circuit board, which includes a cover film, a conductive circuit pattern, and a first dielectric layer that are sequentially attached to each other. The cover film has at least one opening that passes through the cover film. exposed in the opening, the conductive circuit pattern exposed from the opening forms a solder pad, and a low-temperature solder paste layer is formed on the solder pad, an electronic component is welded to the low-temperature solder paste layer, and the electronic component passes through The low-temperature solder paste layer is electrically connected to the welding pad, and the material of the first dielectric layer is polyethylene naphthalate.

Compared with the prior art, the flexible circuit board and the manufacturing method provided by this technical solution use polyethylene naphthalate (PEN) as the dielectric layer and use low-temperature solder paste layer to weld electronic parts, because of the resistance of PEN The thermal performance is better than the heat resistance of PET, and the melting point of the low-temperature solder paste is lower, so that the parts can be welded on the flexible circuit board, and the flexible circuit board can be bonded with the module, so that Expand the scope of use of flexible printed circuit boards.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a copper-clad substrate provided by the first embodiment of the technical solution.

FIG. 2 is a schematic cross-sectional view of the copper-clad substrate of FIG. 1 after fabrication of a circuit substrate.

FIG. 3 is a schematic cross-sectional view of a cover film formed on the circuit substrate of FIG. 2 .

4 is a schematic cross-sectional view of a flexible circuit board formed after printing solder paste and soldering electronic components on the circuit substrate with a cover film in FIG. 3 .

FIG. 5 is a schematic cross-sectional view of the copper-clad substrate provided by the second embodiment of the technical solution.

FIG. 6 is a schematic cross-sectional view of the copper-clad substrate in FIG. 5 after conductive vias are formed.

FIG. 7 is a schematic cross-sectional view of the copper-clad substrate of FIG. 6 after the conductive vias are formed and the circuit substrate is formed.

FIG. 8 is a schematic cross-sectional view after forming a cover film on the circuit substrate of FIG. 7 .

FIG. 9 is a schematic cross-sectional view of a flexible circuit board formed after printing low-temperature solder paste and soldering electronic components on the circuit substrate after forming a cover film in FIG. 8 .

Description of main component symbols

Copper clad substrate 110,910 Copper foil layer 111 first adhesive layer 112,912 first dielectric layer 113,913 Conductive Line Graphics 120 circuit board 101,901 cover film 130 Second adhesive layer 131,914 second dielectric layer 132,932 to open 133,933 pad 121,921 Low temperature solder paste layer 140,950 electronic parts 150,960 flexible circuit board 100,900 first copper foil layer 911 Second Copper Foil Layer 915 Conductive Via 916 Copper on the first side 917 second copper 918 first conductive pattern 920 Second Conductive Line Pattern 922 first cover film 930 Second cover film 940 The third glue layer 931 Fourth glue layer 941 third dielectric layer 942

The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings.

Detailed ways

The flexible circuit board provided by the present invention and its manufacturing method will be further described below with specific examples.

The flexible circuit board manufacturing method provided by the first embodiment of the technical solution includes the following steps:

The first step, referring to FIG. 1 , is to provide a copper clad substrate 110 .

In this embodiment, the copper-clad substrate 110 is a single-sided copper-clad substrate, which includes a copper foil layer 111 , a first adhesive layer 112 and a first dielectric layer 113 that are attached in sequence.

The copper foil layer 111 may be electrolytic copper foil or rolled copper foil. The material of the first adhesive layer 112 is high light-transmitting epoxy-acrylate resin (Epoxy-Acrylate) or epoxy resin (Epoxy). The material of the first dielectric layer 113 is polyethylene naphthalate (PEN) with high light transmission. Compared with PET materials, PEN materials have higher heat resistance, physical and mechanical properties, gas barrier properties, chemical stability, etc.

Of course, the copper clad substrate 110 may not include the first adhesive layer 112 .

The second step, please refer to FIG. 2 , is to manufacture the copper foil layer 111 to form a conductive circuit pattern 120 , so as to obtain the circuit substrate 101 .

In this step, a portion of the copper foil layer 111 is etched away by using an image transfer process and an etching process, so as to obtain the conductive circuit pattern 120 .

The third step, please refer to FIG. 3 , is to provide a cover film 130 , and press-bond the cover film 130 to one side of the conductive circuit pattern 120 of the circuit substrate 101 .

The cover film 130 includes a second adhesive layer 131 and a second dielectric layer 132 that are attached together. The material of the second adhesive layer 131 is epoxy acrylate resin or epoxy resin with high light transmission. The material of the second dielectric layer 132 is polyethylene naphthalate with high light transmission. During pressing, the second adhesive layer 131 is directly attached to the conductive circuit pattern 120 . An opening 133 is formed on the covering film 130, and the opening 133 penetrates through the second adhesive layer 131 and the second dielectric layer 132, and part of the conductive circuit pattern 120 is exposed from the opening 133. The conductive pattern 120 exposed in the opening 133 forms a pad 121 .

Of course, the number of openings 133 can also be multiple, so as to form a plurality of welding pads 121, and the cover film 130 can also only include the second dielectric layer 132, which is formed on one of the conductive circuit patterns by coating or the like. side.

The fourth step, please refer to FIG. 4, forms a low-temperature solder paste layer 140 by printing on the pad 121, and solders an electronic component 150 on the low-temperature solder paste layer 140, thereby forming a flexible circuit board 100.

The electronic component 150 is electrically connected to the pad 121 through the low temperature solder paste layer 140 . Certainly, the low-temperature solder paste layer 140 may also be formed on the solder pad 121 in other ways.

The melting point of commonly used lead-free solder paste is generally 216 degrees Celsius to 220 degrees Celsius, while the heat-resistant temperature of PEN materials is generally around 175 degrees Celsius, that is, the high melting point of commonly used lead-free tin exceeds the heat-resistant temperature of PEN materials; while low-temperature tin The melting point of the paste is generally around 138 degrees Celsius, which is within the heat-resistant temperature range of PEN materials; therefore, in this case, low-temperature solder paste is selected for printing, thereby forming a low-temperature solder paste layer 140 on the solder pad 121 . In this embodiment, the composition of the low-temperature solder paste includes tin-bismuth alloy and flux, wherein, preferably, the tin-bismuth alloy is Sn42Bi58, and the content of flux in the low-temperature solder paste is 10.5%±0.5%.

The flexible circuit board 100 includes a second dielectric layer 132 , a second adhesive layer 131 , a conductive circuit pattern 120 , a first adhesive layer 112 and a first dielectric layer 113 which are sequentially attached. An opening 133 is formed on the flexible circuit board 100, and the opening 133 penetrates through the second glue layer 131 and the second dielectric layer 132, and part of the conductive circuit pattern 120 is exposed from the opening 133. The conductive pattern 120 exposed in the opening 133 forms a pad 121 . A low-temperature solder paste layer 140 is formed on the solder pad 121 , and an electronic component 150 is welded on the low-temperature solder paste layer 140 , and the electronic component 150 is electrically connected to the solder pad 121 through the low-temperature solder paste layer 140 . Wherein, the material of each of the adhesive layers is epoxy acrylate resin or epoxy resin with high light transmission. The material of each dielectric layer is polyethylene naphthalate with high light transmission.

In addition, the above-mentioned manufacturing method of the flexible circuit board 100 may also include the step of laminating the modules, specifically, providing a module and a third adhesive layer after pressing the covering film or welding the electronic parts, The module is bonded to the first dielectric layer 113 through the third adhesive layer, so that the formed flexible circuit board 100 further includes a module, and the module is bonded to the first dielectric layer 113 through a third adhesive layer. The first dielectric layer 113 of the flexible circuit board 100 is bonded together. The module can be a high-transmittance panel or the like.

In the flexible circuit board 100 produced by this technical solution, the conductive circuit pattern 120 can be clearly observed through the highly transparent second dielectric layer 132 and the second adhesive layer 131 of the flexible circuit board 100 . In addition, in order to make the formed conductive circuit pattern 120 more transparent, the first surface of the copper foil layer 111 of the copper-clad substrate 110 that is in contact with the first adhesive layer 112 and the first surface of the copper foil layer 112 and the Blackened layers are formed on the second surfaces opposite to the first surface.

The flexible circuit board manufacturing method provided by the second embodiment of the technical solution includes the following steps:

The first step, referring to FIG. 5 , is to provide a copper clad substrate 910 .

In this embodiment, the copper-clad substrate 910 is a double-sided copper-clad substrate, which includes a first copper foil layer 911, a first adhesive layer 912, a first dielectric layer 913, a second adhesive layer 914 and a second Copper foil layer 915.

The first and second copper foil layers 911 and 915 can be electrolytic copper foil or rolled copper foil. The first and second adhesive layers 912 and 914 are made of epoxy acrylate resin or epoxy resin with high light transmission. The material of the first dielectric layer 913 is polyethylene naphthalate with high light transmission. Compared with PET materials, PEN materials have higher heat resistance, physical and mechanical properties, gas barrier properties, chemical stability, etc.

Of course, the copper-clad substrate 910 may not include the first and second adhesive layers 912, 914, that is, the copper-clad substrate 910 includes the first copper foil layer, the first dielectric layer and the second Two copper foil layers.

The second step, please refer to FIG. 6 , is to form at least one conductive via 916 on the copper-clad substrate 910 .

The conductive via 916 penetrates through the copper clad substrate 910 and electrically connects the first copper foil layer 911 and the second copper foil layer 915 .

In this embodiment, the formation method of the conductive via 916 is as follows: firstly, at least one through hole is formed on the copper-clad substrate 910 by mechanical drilling; and then electroplating to form a conductive copper layer on the wall of the through hole , forming a first surface copper 917 on the surface of the first copper foil layer 911, and forming a second surface copper 918 on the surface of the second copper foil layer 915, and electrically connecting the conductive copper layer to the first copper foil layer 915. The foil layer 911 and the second copper foil layer 915 form the conductive via 916 . Of course, the through holes may also be formed by laser etching.

The third step, please refer to Fig. 7, make the first copper foil layer 911 and the first surface copper 917 to form a first conductive circuit pattern 920, and make the second copper foil layer 915 and the second The surface copper 918 is fabricated to form a second conductive circuit pattern 922, thereby obtaining a circuit substrate 901.

In this step, the first and second conductive circuit patterns 920 and 922 are obtained by using an image transfer process and an etching process. The conductive via 916 is electrically connected to the first conductive circuit pattern 920 and the second conductive circuit pattern 922 .

The fourth step, referring to FIG. 8 , is to provide a first cover film 930 and a second cover film 940, press the first cover film 930 to one side of the first conductive circuit pattern 920 of the circuit substrate 901, and place The second cover film 940 is pressed on one side of the second conductive pattern 922 of the circuit substrate 901 .

The first covering film 930 includes a third adhesive layer 931 and a second dielectric layer 932 . The second covering film 940 includes a fourth adhesive layer 941 and a third dielectric layer 942 . The third and fourth adhesive layers 931 and 941 are made of epoxy acrylate resin or epoxy resin with high light transmission. The second and third dielectric layers 932 and 942 are made of polyethylene naphthalate with high light transmission. An opening 933 is formed on the first covering film 930, the opening 933 penetrates the third adhesive layer 931 and the second dielectric layer 932, and part of the first conductive circuit pattern 920 is exposed from the opening 933 Then, the first conductive pattern 920 exposed from the opening 933 forms a pad 921 .

Certainly, the number of the openings 133 may also be multiple, so as to form multiple welding pads 121 . In addition, the second covering film 940 may also be formed with an opening, so as to expose part of the second conductive circuit pattern 922 . The first and second covering films 930, 940 may also only include the dielectric layer 132, and be formed on one side of the conductive circuit pattern by coating or the like.

The fifth step, please refer to FIG. 9 , forms a low-temperature solder paste layer 950 by printing on the pad 921, and solders an electronic component 960 on the low-temperature solder paste layer 950, thereby forming a flexible circuit board 900.

The electronic component 960 is electrically connected to the pad 921 through the low temperature solder paste layer 950 . Of course, the low-temperature solder paste layer 140 may also be formed on the solder pad 921 in other ways.

The melting point of commonly used lead-free solder paste is generally 216 degrees Celsius to 220 degrees Celsius, while the heat-resistant temperature of PEN materials is generally around 175 degrees Celsius, that is, the high melting point of commonly used lead-free tin exceeds the heat-resistant temperature of PEN materials; while low-temperature tin The melting point of the paste is generally around 138 degrees Celsius, which is within the heat-resistant temperature range of PEN materials; therefore, in this case, low-temperature solder paste is selected for printing, thereby forming a low-temperature solder paste layer 950 on the solder pad 921 . In this embodiment, the low-temperature solder paste includes tin-bismuth alloy and flux, wherein, preferably, the tin-bismuth alloy is Sn42Bi58, and the content of flux in the low-temperature solder paste is 10.5%±0.5%. .

The flexible circuit board 900 includes a second dielectric layer 932, a third adhesive layer 931, a first conductive circuit pattern 920, a first adhesive layer 912, a first dielectric layer 913, and a second adhesive layer 914, which are attached in sequence. , the second conductive circuit pattern 922 , the fourth adhesive layer 941 and the third dielectric layer 942 . The flexible circuit board 900 includes at least one conductive via 916 passing through the first conductive circuit pattern 920, the first adhesive layer 912, the first dielectric layer 913, the second adhesive layer 914 and the second conductive circuit pattern 922 , the conductive via 916 is electrically connected to the first conductive circuit pattern 920 and the second conductive circuit pattern 922 . An opening 933 is formed on the flexible circuit board 900, the opening 933 passes through the third adhesive layer 931 and the second dielectric layer 932, and part of the first conductive circuit pattern 920 is exposed from the opening 933 , the first conductive pattern 920 exposed from the opening 933 forms a pad 921 . A low-temperature solder paste layer 950 is formed on the solder pad 921 , and an electronic component 960 is welded on the low-temperature solder paste layer 950 , and the electronic component 960 is electrically connected to the solder pad 921 through the low-temperature solder paste layer 950 . Wherein, the material of each of the adhesive layers is epoxy acrylate resin or epoxy resin with high light transmission. The material of each dielectric layer is polyethylene naphthalate with high light transmission.

In addition, the flexible circuit board 900 can also be formed with a first module and a second module, the first module and the second dielectric layer of the flexible circuit board 900 through a fifth adhesive layer 932, and the second module is bonded to the third dielectric layer 942 of the flexible circuit board 900 through a sixth adhesive layer. The first module and the second module may be high light-transmitting panels or the like.

In the flexible circuit board 900 produced by this technical solution, the first conductive circuit pattern 920 can be clearly observed through the highly transparent second dielectric layer 932 and the third adhesive layer 931 of the flexible circuit board 900 , the second conductive circuit pattern 922 can be clearly observed through the third dielectric layer 942 and the fourth adhesive layer 941 of the flexible circuit board 900 with high light transmission. In addition, in order to make the formed conductive circuit pattern more transparent, the first surface of the first copper foil layer 911 of the copper clad substrate 910 that is adjacent to the first adhesive layer 912 and the The second surface opposite to the first surface forms a blackened layer respectively, and the third surface of the second copper foil layer 915 that is adjacent to the second adhesive layer 914 and the surface opposite to the third surface Blackened layers are respectively formed on the fourth surfaces.

Compared with the prior art, the flexible circuit board provided by this technical solution and the manufacturing method use PEN as the dielectric layer, and use low-temperature solder paste layer to weld electronic parts, because the heat resistance of PEN is better than that of PET , and the melting point of low-temperature solder paste is low, so that parts can be welded on the flexible circuit board 100, 900, and the flexible circuit board 100, 900 can be bonded with the module, thereby expanding the The scope of use of flexible printed circuit boards.

It can be understood that those skilled in the art can make various other corresponding changes and modifications according to the technical concept of the present invention, and all these changes and modifications should belong to the protection scope of the claims of the present invention.

Claims (10)

1. A method for making a flexible circuit board, comprising the steps of: A copper-clad substrate is provided, the copper-clad substrate includes a first copper foil layer and a first dielectric layer, wherein the material of the first dielectric layer is polyethylene naphthalate; making the first copper foil layer to form a first conductive circuit pattern; A cover film is formed on one side of the first conductive circuit pattern, the cover film has at least one opening passing through the cover film, part of the first conductive circuit pattern is exposed from the opening, and from the opening The exposed first conductive line pattern forms a pad; and A low-temperature solder paste layer is formed on the solder pad, and an electronic component is soldered to the low-temperature solder paste layer, and the electronic component is electrically connected to the solder pad through the low-temperature solder paste layer, thereby obtaining a flexible circuit board . 2. The manufacturing method of the flexible printed circuit board according to claim 1, wherein the cover film comprises a second adhesive layer and a second dielectric layer that fit together, and the material of the second adhesive layer is Epoxy acrylate resin or epoxy resin, the material of the second dielectric layer is polyethylene naphthalate, the cover film is formed on the surface of the first conductive circuit pattern by pressing, when pressing, The second adhesive layer is directly attached to the first conductive circuit pattern. 3. The manufacturing method of the flexible circuit board according to claim 1, wherein the composition of the low-temperature solder paste includes tin-bismuth alloy and flux. 4. The manufacturing method of the flexible circuit board according to claim 3, wherein the tin-bismuth alloy is Sn42Bi58. 5. The manufacturing method of the flexible circuit board according to claim 1, wherein the copper-clad substrate further comprises a second layer on the side of the first dielectric layer away from the first copper foil layer. Copper foil layer, the manufacturing method of the flexible circuit board also includes the step of forming a conductive via hole electrically connecting the first copper foil layer and the second copper foil layer on the copper clad substrate, and the The first copper foil layer is fabricated to form a first conductive circuit pattern while the second copper foil layer is fabricated to form a second conductive circuit pattern. 6. The manufacturing method of the flexible circuit board according to claim 1, characterized in that, a first adhesive layer is further included between the first copper foil layer and the first dielectric layer, and the first The material of the adhesive layer is epoxy acrylate resin or epoxy resin. 7. A flexible circuit board, which includes a cover film, a conductive circuit pattern and a first dielectric layer that are attached in sequence, the cover film has at least one opening that passes through the cover film, and part of the conductive circuit pattern is from The opening is exposed, and the conductive circuit pattern exposed from the opening forms a solder pad, and a low-temperature solder paste layer is formed on the solder pad, and an electronic component is soldered to the low-temperature solder paste layer. The component is electrically connected to the pad through the low-temperature solder paste layer, and the first dielectric layer is made of polyethylene naphthalate. 8. The flexible circuit board according to claim 7, wherein the cover film comprises a second adhesive layer and a second dielectric layer that are attached together, and the material of the second adhesive layer is epoxy acrylic ester resin or epoxy resin, the second dielectric layer is made of polyethylene naphthalate, and the second adhesive layer is directly attached to the conductive circuit pattern. 9. The flexible circuit board according to claim 7, wherein the composition of the low-temperature solder paste includes tin-bismuth alloy. 10. The flexible circuit board according to claim 7, wherein a first adhesive layer is further included between the conductive circuit pattern and the first dielectric layer, and the material of the first adhesive layer is ring Oxyacrylate resin or epoxy resin.