Manufacturing method of circuit board embedded with carbon oil resistor

Abstract

The invention discloses a method for manufacturing a circuit board embedded with a carbon oil resistor, which comprises the following steps of: taking a double-sided copper-clad plate, manufacturing a circuit pattern comprising a carbon oil connecting pattern which comprises a wire end and a connecting end, adhering a dry film to two sides, a dry film windowing pattern is manufactured in the area, corresponding to the carbon oil pattern, of the surface where the carbon oil connection pattern is located, plasma treatment is conducted, then film stripping is conducted, a carbon oil layer is manufactured in the area of the carbon oil pattern, a bonding layer prepreg is taken, core plates of other layers are taken and stacked and pressed together with the carbon oil plate, and the circuit board embedded with the carbon oil resistor is formed through subsequent procedure manufacturing; by designing the connecting end, the carbon oil layer has a larger bonding area, the bonding force of the carbon oil layer is increased, prepregs are laminated and bonded to the surface of the carbon oil layer, the interlayer bonding force of the carbon oil layer is improved, and the problems of falling, layering of a multi-layer board and even board explosion of the multi-layer board caused by poor bonding of the carbon oil layer are solved.

Description

Technical Field

[0001] The present invention relates to the field of circuit board processing, and particularly to a method for manufacturing a circuit board with embedded carbon oil resistors. Background Art

[0002] In recent years, with the rapid development of intelligent electronic products, the technology of their supporting control modules has also been continuously improved. For some application scenarios that require the miniaturization, multi-functionality, and intelligence of electronic modules, it is required that the circuit board has a high-density design. Since ordinary electronic components are generally soldered on the surface of the circuit board, which requires a certain amount of surface space, while the corresponding internal space is relatively sufficient. Therefore, resistors are made in the form of carbon oil on the circuit pattern layer of the circuit board, and further can be embedded into the circuit board to form a high-density wiring design, improving the volume and surface space utilization rate of the circuit board, and improving the support function performance of the circuit board.

[0003] In the prior art for making carbon oil patterns, generally, a carbon oil layer is screen-printed and then baked and cured to form a carbon oil resistor module. Then, the carbon oil layer is laminated into the circuit board by using the lamination method of traditional multi-layer circuit boards.

[0004] However, since carbon oil generally has strong inertness, and the formed granularity is larger than that of ordinary ink, and the bonding force between the cured carbon oil and the insulating dielectric layer and copper layer of the circuit board is relatively low, the problem of carbon oil layer peeling off is likely to occur. Even if the carbon oil layer is not easy to peel off after screen-printing and baking, during the lamination of multi-layer circuit boards, the high-temperature and high-pressure conditions will further cause poor bonding force or peeling off of the carbon oil layer between layers, thus generating potential hazards of circuit board delamination and explosion.

[0005] Therefore, based on the above background and problems, a manufacturing method is needed that can effectively improve the bonding force between the carbon oil layer and the circuit board body, as well as the bonding force and reliability of the carbon oil layer laminated into the circuit board. Summary of the Invention

[0006] Aiming at the problems of weak bonding force in the prior art for making carbon oil layers and peeling off of the carbon oil layer or poor interlayer bonding force of the circuit board after manufacturing a multi-layer circuit board with an embedded carbon oil layer, the present invention provides a method for manufacturing a circuit board with embedded carbon oil resistors. The circuit board is processed according to design data, and a carbon oil pattern is designed on the inner layer of the circuit board. The manufacturing method includes the following steps: S10: Take a double-sided copper clad laminate and make a circuit pattern including a carbon oil connection pattern to form a circuit pattern board. The carbon oil connection pattern includes a wire end and a connection end, and the width of the connection end is greater than that of the wire end. S20: Stick dry film on both sides of the circuit pattern board, make a dry film opening pattern in the area corresponding to the carbon oil pattern on the side where the carbon oil connection pattern is located, perform plasma treatment, and then strip the film; form an activation board; S30: Make a carbon oil layer in the carbon oil pattern area of the activation board to form a carbon oil board; S40: Take a bonding layer prepreg and other core boards, stack them together with the carbon oil board according to the layout structure to form a stacked structure. The bonding layer prepreg is arranged adjacent to the carbon oil layer and is pressed. After subsequent processes are carried out, the circuit board with the embedded carbon oil resistor is formed.

[0007] Further, the length and width of the connection end are pre-expanded compared with the pattern in the design data, and a grid pattern is made on the connection end.

[0008] Further, the single side of the dry film opening pattern is pre-expanded compared with the carbon oil pattern.

[0009] Further, the shape of the carbon oil layer is dumbbell-shaped. The single side width of the "dumbbell" part at both ends of the dumbbell shape is greater than the width of the connection end, and the width of the "central rod" part in the middle of the dumbbell shape is equal to the specified width in the design data.

[0010] Further, the carbon oil layer is made by screen printing.

[0011] Further, the screen printing is as follows: screen print 1 / 4 to 1 / 3 of the thickness of the carbon oil pattern in the design data for the first time, and bake at 125°C to 160°C for 5 min to 20 min; screen print the remaining thickness of the carbon oil pattern for the second time, and bake at 125°C to 160°C for 30 min to 70 min.

[0012] Further, the bonding layer prepreg is composed of a high-flow prepreg and other bonding layers stacked together, and the high-flow prepreg is arranged adjacent to the carbon oil layer.

[0013] Further, the resin content of the high-flow prepreg is 56% to 68%.

[0014] Further, a release layer and a heat-conducting layer are respectively arranged on the upper and lower surfaces of the stacked structure in sequence; the heat-conducting layer is an aluminum sheet layer or a copper foil layer.

[0015] Further, the heating rate of the pressing is 1.0°C / min to 2.5°C / min; after the pressing is completed and cooled down, the cold pressing extension time is 15 min to 25 min.

[0016] The present invention designs connection ends to enable the carbon oil layer to have a larger bonding area, further designs a grid pattern to further increase the bonding force between the carbon oil layer and the connection ends, and further adopts a manufacturing method of secondary screen printing and secondary baking to manufacture the carbon oil layer, which can improve the bonding force between the carbon oil layer and the board surface from the perspectives of screen printing and curing. By laminating a high-flow glue prepreg on the surface of the carbon oil layer, the interlayer bonding force between the carbon oil layer and the prepreg is improved. Further, a release layer and a heat-conducting layer are provided, and a lamination method of slow heating and extended cold pressing time is further adopted to effectively improve the bonding force between the embedded carbon oil layer and the multilayer board, forming an effective and reliable manufacturing effect of the carbon oil layer, and improving problems such as peeling caused by poor bonding of the carbon oil layer, delamination of the multilayer board, and even explosion of the multilayer board; the overall processing forms a process-based manufacturing process with front-back coordination, realizing the process-based manufacturing of the circuit board with embedded carbon oil resistors. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0018] Figure 1 It is the main process flow chart included in the embodiment of the present invention; Figure 2 It is the plane structure diagram of the circuit pattern board formed by manufacturing this embodiment including the carbon oil connection pattern; Figure 3 For Figure 2 the cross-sectional structure diagram of the A-A plane of; Figure 4 It is the plane diagram of the activation board formed by manufacturing this embodiment including the dry film opening pattern; Figure 5 For Figure 4 the cross-sectional structure diagram of the B-B plane of; Figure 6 It is the plane diagram of the carbon oil board formed by manufacturing this embodiment including the carbon oil layer; Figure 7 For Figure 6 the cross-sectional structure diagram of the C-C plane of; Figure 8 It is the plane diagram of the carbon oil layer formed by manufacturing a bad design of this kind; Figure 9 It is the plane diagram of the carbon oil layer formed by manufacturing another bad design of this kind; Figure 10 It is the cross-sectional structure diagram of the stacked structure formed by manufacturing this embodiment; Figure 11 The figure is a schematic cross-sectional structure diagram of a circuit board with an embedded carbon oil resistor made in this embodiment.

[0019] Description of the reference numerals in the drawings:

[0020] The realization of the object of the present invention, its functional features and advantages will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] It should be noted that all the directional indications (such as up, down, left, right, front, back, inside, outside, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0023] In addition, the descriptions such as "first" and "second" in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0024] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0025] Please refer to Figure 1 ; Figure 1 It is the main process flow chart included in the embodiment of the present invention.

[0026] The circuit board with an embedded carbon oil resistor in the embodiment of the present invention is processed according to the design data. The inner layer of the circuit board is designed with a carbon oil pattern, and its manufacturing method includes Figure 1 the main manufacturing process flow, which will be described in detail in the following steps.

[0027] Please refer to Figure 2 andFigure 3 ; Figure 2 Schematic plan view of a circuit pattern board formed with a carbon oil connection pattern in this embodiment; Figure 3 is Figure 2 Cross-sectional structure schematic diagram of the A-A plane of.

[0028] Step S10: Take a double-sided copper clad laminate, which includes an insulating dielectric layer 120, a first-side copper layer, and a second-side copper layer 130, and fabricate a circuit pattern including a carbon oil connection pattern 110 thereon to form a circuit pattern board 10; the carbon oil connection pattern 110 includes a wire end 1110 and a connection end 1120, and the width of the connection end 1120 is greater than that of the wire end 1110.

[0029] In this embodiment, the form of directly fabricating a carbon oil layer on two wire ends in the prior art is changed to first designing a connection end 1120 for the wire end 1110, so as to improve the bonding force between the carbon oil layer 310 and the wire and prevent the problem that the carbon oil layer 310 is easily separated from the wire end.

[0030] It should be noted that since the connection end 1120 is added, the resistance value formed by the carbon oil layer 310 needs to be recalculated, and the pattern of the carbon oil layer 310 needs to be redesigned. See the description of the subsequent processes for specific fabrication.

[0031] In this embodiment, the length and width of the connection end 1120 are pre-expanded compared with the pattern in the design data, and a grid pattern is fabricated on the connection end 1120.

[0032] In this embodiment, the width and length of the connection end 1120 are designed to be larger, which can effectively increase the bonding area between the carbon oil layer 310 and it, thereby improving the bonding force. Further designing a grid pattern can form a structure in which the subsequent screen-printed carbon oil layer 310 and the grid pattern are mutually embedded, further improving the bonding force between the carbon oil and the connection end 1120.

[0033] Please refer to Figure 4 , Figure 5 ; Figure 4 Schematic plan view of an activation board formed with a dry film opening pattern in this embodiment; Figure 5 is Figure 4 Cross-sectional structure schematic diagram of the B-B plane of.

[0034] Step S20: Attach dry films 210 to both sides of the circuit pattern board 10, fabricate a dry film opening pattern 2110 in the area corresponding to the carbon oil pattern on the surface where the carbon oil connection pattern 110 is located, perform plasma treatment, and then strip the film; an activation board 30 is formed.

[0035] In this embodiment, the area where the carbon oil layer 310 needs to be fabricated is subjected to plasma treatment. By leveraging the activation advantage of plasma treatment, the surface activity of the insulating dielectric layer 120 and the connection end 1120 in this area is enhanced, and a uniform rough surface is formed, providing a board surface foundation that is more conducive to bonding for the subsequent fabrication of the carbon oil layer 310, thereby improving the bonding strength.

[0036] In this embodiment, the single side of the dry film opening pattern 2110 is pre-expanded compared to the carbon oil pattern.

[0037] Appropriately increasing the area of the dry film opening pattern 2110 appropriately enlarges the area subjected to plasma treatment, providing a tolerance range for alignment errors for the subsequent fabrication of the carbon oil layer 310, enabling the carbon oil layer 310 to completely adhere within the area subjected to plasma treatment.

[0038] Please refer to Figure 6 、 Figure 7 and Figure 8 、 Figure 9 ; Figure 6 is a schematic plan view of a carbon oil board fabricated in this embodiment, including a carbon oil layer; Figure 7 is Figure 6 a schematic cross-sectional structure view of the C-C plane of Figure 8 is a schematic plan view of a carbon oil layer fabricated according to a bad design of this type; Figure 9 is a schematic plan view of a carbon oil layer fabricated according to another bad design of this type.

[0039] Step S30: Fabricate a carbon oil layer 310 in the carbon oil pattern area of the activation board 20 to form a carbon oil board 30.

[0040] In this embodiment, the fabrication of the carbon oil layer 310 is performed by screen printing to form the carbon oil layer 310.

[0041] In this embodiment, a screen with a mesh count of 71T, 100T, or 120T is preferably used for screen printing. The screen printing process is as follows: for the first time, screen print 1 / 4 to 1 / 3 of the thickness of the carbon oil pattern in the design data, and bake at 125°C to 160°C for 5 min to 20 min; for the second time, screen print the remaining thickness of the carbon oil pattern, and bake at 125°C to 160°C for 30 min to 70 min.

[0042] Adopt the method of screen printing twice. For the first screen printing, a relatively thin base layer is formed, and baking at a relatively high temperature for a short time is used for pre-curing (not complete curing). This not only enables the carbon oil to have a better bonding force with the surface after plasma treatment in the relatively thin state, but also provides a similar and compatible carbon oil base layer bonding foundation for the second screen printing, further improving the bonding force of the carbon oil layer in the second screen printing. Moreover, thorough curing at a relatively high temperature for a long time is adopted after the second screen printing, improving the overall bonding effect of the carbon oil layer 310.

[0043] In this embodiment, the shape of the carbon oil layer 310 is dumbbell-shaped. The single-side width of the "dumbbell" part 3110 at both ends of the dumbbell shape is greater than the width of the connection end 1120, and the width of the "central rod" part 3120 in the middle of the dumbbell shape is equal to the specified width in the design data.

[0044] On the one hand, due to the reason of designing the connection end 1120 based on the above-mentioned wire end 1110, it is necessary to increase the width of the "dumbbell" part 3110 of the carbon oil layer 310 at the same time so that the carbon oil layer can effectively cover the connection end 1120. On the other hand, since the width of the "dumbbell" part 3110 is increased, it is necessary to correspondingly reduce the width of the "central rod" part 3120 to make the resistance value of the carbon oil layer 310 reach the required resistance value and prevent resistance deviation; for the specific resistance value calculation, the actual resistance value can be calculated according to the width of the "central rod" part 3120 and the length of the area (blank area) between the connection ends 1120, and after the carbon oil layer 310 is manufactured, a resistance measuring instrument or a flying probe tester can be used to test the specific resistance value.

[0045] As Figure 8 、 Figure 9 shown, if the two ends of the "dumbbell" part 3110 are not pre-expanded, and subsequent errors and displacements occur during screen printing, it may cause poor connection between the carbon oil layer 310 and the connection end 1120, which may affect the resistance value effect or make the resistance value unstable.

[0046] Please refer to Figure 10 、 Figure 11 ; Figure 10 is a schematic cross-sectional structure diagram of the stacked structure manufactured in this embodiment; Figure 11 is a schematic cross-sectional structure diagram of the circuit board with the embedded carbon oil resistor manufactured in this embodiment.

[0047] Step S40: Take the bonding layer semi-cured sheet 410, and take other layer core boards 420, and stack them together with the carbon oil board 30 according to the layout structure to form a stacked structure. The bonding layer semi-cured sheet 410 is arranged adjacent to the carbon oil layer and is pressed. After subsequent processes are carried out, the circuit board 50 with the embedded carbon oil resistor is formed.

[0048] In this embodiment, the adhesive prepreg 410 is composed of a high-flow prepreg 4110 and other adhesive layers 4120 laminated together, and the high-flow prepreg 4110 is arranged adjacent to the carbon oil layer 310.

[0049] In this embodiment, the resin content of the high-flow prepreg 4110 is 56% to 68%.

[0050] In this embodiment, the high-flow prepreg 4110 is laminated on one side of the carbon oil layer 310. The colloid with a relatively high content (usually epoxy resin or acrylic acid) and the resin contained in the carbon oil of the carbon oil layer 310 are used to form a more reliable bonding force, improve the bonding force between the prepreg and the carbon oil layer 310, and prevent problems such as delamination and explosion of the multilayer circuit board embedded in the carbon oil layer 310 during lamination or application.

[0051] In this embodiment, a release layer 430 and a heat-conducting layer 440 are sequentially arranged on the upper and lower surfaces of the stacked structure 40; the heat-conducting layer 440 is an aluminum sheet layer or a copper foil layer.

[0052] Setting the heat-conducting layer 440 can effectively and efficiently conduct the heat during the lamination process between layers, especially to the high-flow prepreg 4110, improve the resin flow effect between layers, and improve the conformal coating property.

[0053] In this embodiment, the heating rate of the lamination is 1.0 °C / min to 2.5 °C / min, preferably 1.6 °C / min or 18 °C / min; after the lamination is completed and cooled, the cold pressing extension time is 15 min to 25 min, preferably 20 min.

[0054] In this embodiment, a relatively slow heating rate is adopted to enable the adhesive prepreg and the insulating dielectric layers of each layer to be heated slowly and evenly, so as to form a slow and sufficient filling effect of the colloid, prevent problems such as poor adhesion and filling effect caused by colloid crystallization. Extending the cold pressing time after the lamination is completed can effectively ensure the slow self-cooling of the board body, prevent problems such as delamination caused by excessive shrinkage, and increase the bonding force between layers.

[0055] It should be noted that due to the relatively high precision of the circuit board in the actual design and processing process, the actual structure diagram and the dimensions such as the thickness and line width between each layer are in the micron level. For example, the thickness of each layer is generally 5 μm to 50 μm. If the accompanying drawings of the specification are made according to the actual ratio, there will be a problem of unclear illustration. Therefore, in order to more clearly represent the implementation process of the manufacturing method, the accompanying drawings of this embodiment are all schematic diagrams with enlarged technical features, which do not represent the dimensions of the actual structure diagram, nor do they represent an enlarged diagram of the actual structure diagram in proportion.

[0056] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or any direct / indirect application in other related technical fields shall be included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing a circuit board with embedded carbon oil resistors, wherein the circuit board is processed according to design data, and the inner layer of the circuit board is designed with a carbon oil pattern; characterized in that: The production method comprises the following steps: S10: Take a double-sided copper clad laminate, make a circuit pattern including a carbon oil connection pattern, and form a circuit pattern board; The carbon oil connection pattern includes a wire end and a connection end, and the width of the connection end is greater than that of the wire end; S20: attaching dry films to both sides of the circuit pattern board, making dry film window patterns on the surface where the carbon oil connection pattern is located and the area corresponding to the carbon oil pattern, performing plasma treatment, and then removing the film to form an activated board; S30: forming a carbon oil layer on the carbon oil pattern area of ​​the activation plate to form a carbon oil plate; S40: Take the adhesive layer semi-cured sheet and other core boards, and stack them together with the carbon oil board according to the layout structure to form a stacked structure. The adhesive layer semi-cured sheet is arranged adjacent to the carbon oil layer and pressed together, and is manufactured through a post-process to form the circuit board with embedded carbon oil resistors.

2. A method for manufacturing a circuit board with embedded carbon oil resistors as claimed in claim 1, characterized in that: The length and width of the connection end are pre-enlarged compared to the pattern of the design data, and the connection end is made with a grid pattern.

3. A method for manufacturing a circuit board with embedded carbon oil resistors as claimed in claim 1 or 2, characterized in that: The single side of the dry film window pattern is pre-enlarged compared with the carbon oil pattern.

4. A method for manufacturing a circuit board with embedded carbon oil resistors as claimed in claim 3, characterized in that: The shape of the carbon oil layer is dumbbell-shaped, the single-side width of the "dumbbell" parts at both ends of the dumbbell shape is greater than the width of the connecting end, and the width of the middle "center rod" part of the dumbbell shape is equal to the specified width in the design data.

5. The method for manufacturing a circuit board with embedded carbon oil resistor according to claim 1, characterized in that: The carbon oil layer is formed by silk screen printing.

6. A method for manufacturing a circuit board with embedded carbon oil resistors as claimed in claim 5, characterized in that: The silk screen printing is as follows: the first silk screen printing is 1 / 4 to 1 / 3 of the thickness of the carbon oil pattern in the design data, and is baked at 125°C to 160°C for 5min to 20min; the second silk screen printing is the remaining thickness of the carbon oil pattern, and is baked at 125°C to 160°C for 30min to 70min.

7. The method for manufacturing a circuit board with embedded carbon oil resistors as claimed in claim 1, characterized in that: The bonding layer prepreg is composed of a high-flow adhesive prepreg and other bonding layers in a stacked manner, and the high-flow adhesive prepreg is disposed adjacent to the carbon oil layer.

8. A method for manufacturing a circuit board with embedded carbon oil resistors as claimed in claim 7, characterized in that: The high-flow adhesive prepreg has an adhesive content of 56% to 68%.

9. A method for manufacturing a circuit board with embedded carbon oil resistors as claimed in claim 1, characterized in that: A release layer and a heat-conducting layer are respectively disposed on the upper and lower surfaces of the stacked structure in sequence; the heat-conducting layer is an aluminum sheet layer or a copper foil layer.

10. A method for manufacturing a circuit board with embedded carbon oil resistors as claimed in claim 1 or 9, characterized in that: The heating rate of the pressing is 1.0°C / min to 2.5°C / min; after the pressing is completed and the temperature is lowered, the cold pressing extension time is 15min to 25min.

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