Dry film pressing method of circuit board

Abstract

The invention discloses a dry film pressing method of a circuit board. The dry film pressing method comprises a preposition step, a pretreatment step, a mold pressing step, an exposure step and a windowing step. In the pre-arrangement step, an anti-welding dry film and a substrate are provided; in the pretreatment step, one surface of the substrate is cleaned; a mold pressing step: pressing a binding surface of the solder mask dry film on the surface layer of the substrate through a mold pressing machine; an exposure step, wherein light is used for carrying out light curing on the solder mask dry film attached to the substrate to generate a solder mask layer; and a windowing step: windowing the solder mask layer on the substrate through a developing agent. Wherein after the exposure step, the maximum thickness and the minimum thickness of the solder mask layer are defined, the thickness difference between the maximum thickness and the minimum thickness is less than 8 microns, and the surface roughness of the solder mask layer is less than 0.2 microns. Therefore, according to the manufactured circuit board, the thickness difference between the maximum thickness and the minimum thickness of the solder mask layer can be reduced, so that poor contact between the chip and the substrate caused by overlarge thickness difference during subsequent processing is avoided.

Description

Technical Field

[0001] The invention relates to a lamination method, in particular to a dry film lamination method for a circuit board. Background Art

[0002] In the prior art, the technology of applying traditional solder mask ink on circuit boards cannot achieve high uniformity of ink thickness and high reflectivity, and thus cannot meet the requirements of existing electronic product displays for high resolution.

[0003] Therefore, the inventors believe that the above defects can be improved, and have devoted themselves to research and applied scientific principles, and finally proposed the present invention which has a reasonable design and effectively improves the above defects. Summary of the invention

[0004] The embodiment of the present invention provides a dry film lamination method for a circuit board, which can effectively improve the defects that may be caused by the existing solder mask ink.

[0005] The embodiment of the present invention discloses a dry film lamination method for a circuit board, characterized in that the dry film lamination method for a circuit board comprises: a pre-step of providing a solder mask dry film and a substrate; a pre-treatment step of cleaning a surface of the substrate; a pressing step of pressing a bonding surface of the solder mask dry film to the surface layer of the substrate by a pressing machine, and pressing out bubbles in the solder mask dry film by the pressing machine under a vacuum environment; an exposure step of photocuring the solder mask dry film bonded to the substrate with a light to generate a solder mask layer; and a windowing step of opening a window of the solder mask on the substrate through a developer so that at least one opening is generated on the solder mask layer, and at least one opening can expose a portion of the surface of the substrate; wherein, after the exposure step, the solder mask layer is defined to have a maximum thickness and a minimum thickness, a thickness difference between the maximum thickness and the minimum thickness is less than 8 microns, and a surface roughness (Ra) of the solder mask layer is less than 0.2 microns.

[0006] Optionally, the surface of the substrate includes a solder mask area and at least one soldering area; wherein the solder mask layer is generated on the solder mask area of ​​the surface.

[0007] Optionally, the thickness difference between the maximum thickness and the minimum thickness is less than 6 microns.

[0008] Optionally, the surface roughness is less than 0.1 micrometer.

[0009] Optionally, in the molding step, the molding step includes a molding time, and the molding time is between 20 seconds and 40 seconds.

[0010] Optionally, in the compression molding step, the compression molding step includes a compression molding temperature, and the compression molding temperature is between 50°C and 70°C.

[0011] Optionally, in the compression molding step, the compression molding step includes a compression molding pressure, and the compression molding pressure is between 0.4 Mpa and 0.8 Mpa.

[0012] Optionally, the developer in the window opening step is at least one of sodium carbonate and potassium carbonate.

[0013] Optionally, at least one expected opening position is defined in the exposure step; wherein an offset value between the expected opening position and the corresponding opening is no greater than 15 microns.

[0014] Optionally, in the window opening step, at least one of the openings comprises an opening length and an opening width; wherein the opening length is greater than 190 microns and less than 1000 microns, and the opening width is greater than 140 microns and less than 950 microns.

[0015] In summary, the dry film pressing method for a circuit board disclosed in the embodiment of the present invention can reduce the thickness difference between the maximum thickness and the minimum thickness of the solder mask layer through the settings of "a solder mask dry film and a substrate" and "a molding step, pressing a bonding surface of the solder mask dry film to the surface layer of the substrate through a molding machine, and pressing out the bubbles in the solder mask dry film under a vacuum environment through the molding machine; an exposure step, using a light to photo-cure the solder mask dry film bonded to the substrate to generate a solder mask layer", so as to avoid poor contact between the chip and the substrate due to excessive thickness difference during subsequent processing. In addition, the surface roughness can be reduced by the above settings to improve the reflectivity of the solder mask layer.

[0016] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, such description and drawings are only used to illustrate the present invention and are not intended to limit the protection scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a dry film lamination method for a circuit board according to an embodiment of the present invention.

[0018] Figure 2 FIG. 4 is a schematic diagram of a solder mask dry film and a substrate according to an embodiment of the present invention.

[0019] Figure 3 It is a schematic diagram of laminating the solder mask dry film on the substrate according to an embodiment of the present invention.

[0020] Figure 4Schematic diagram of a solder mask and the substrate according to an embodiment of the present invention.

[0021] Figure 5 The figure is a three-dimensional schematic diagram of a circuit board with a solder mask according to an embodiment of the present invention.

[0022] Figure 6 for Figure 5 Schematic cross-sectional view along section line VI-VI. DETAILED DESCRIPTION

[0023] The following is an explanation of the implementation method of the "dry film lamination method for circuit boards" disclosed in the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual dimensions. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention.

[0024] It should be understood that, although the terms "first", "second", "third", etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another component, or one signal from another signal. In addition, the term "or" used herein may include any one or more combinations of the associated listed items depending on the actual situation.

[0025] [Dry film lamination method for circuit boards]

[0026] See also Figures 1 to 6 As shown, this embodiment discloses a dry film lamination method for a circuit board. The dry film lamination method for a circuit board can form a solder mask layer 3 on one surface 21 of a substrate 2 with a solder mask dry film 1, and the solder mask layer 3 can prevent the substrate 2 from being soldered by conductive solder between various electronic components.

[0027] Specifically, the solder mask lamination method for the circuit board includes steps S101, S102, S103, S104, S105, and S106. It should be noted that the order of the steps and the actual operation method in this embodiment can be adjusted according to needs and are not limited to those in this embodiment.

[0028] The step S101 is a pre-step, which includes: providing the solder mask dry film 1 and the substrate 2 (e.g., Figure 2 as shown).

[0029] In detail, the solder mask dry film 1 is generated by coating an ink on a carrier and baking it at a high temperature. In addition, the solder mask dry film 1 can replace the traditional solder mask wet film, and the solder mask dry film 1 can simplify the processing process compared with the traditional solder mask wet film. For example, in the processing of the traditional solder mask, the solder mask wet film must first be adjusted in viscosity before being coated on the substrate and then baked; however, since the solder mask dry film 1 is already in a semi-cured state, when the solder mask dry film 1 is used, the coating and baking processes in the processing of the traditional solder mask can be directly omitted.

[0030] The step S102 is a pre-processing step, which includes: cleaning the surface 21 of the substrate 2 .

[0031] Specifically, the pre-treatment step is to use a solution to clean the surface 21 of the substrate 2 and remove impurities (such as oxides, other metals) on the surface 21. The solution may be at least one of water, an acidic solvent, or an alkaline solvent.

[0032] The step S103 is a molding step, which includes: pressing a bonding surface 11 of the solder mask dry film 1 onto the surface 21 of the substrate 2 by a molding machine, and pressing out bubbles in the solder mask dry film 1 by the molding machine under a vacuum environment.

[0033] Specifically, if Figure 3 As shown, the bonding surface 11 of the solder mask dry film 1 is tightly pressed onto the surface 21 of the substrate 2 by the molding machine (not shown) with an appropriate molding pressure, and the bubbles between the solder mask dry film 1 and the substrate 2 can be pressed out at the same time.

[0034] It is worth mentioning that the compression molding step is performed under the vacuum environment; in the compression molding step, a proper compression molding temperature and a compression molding time can be set by the compression molding machine.

[0035] In this embodiment, the die pressure may be between 0.4 MPa and 0.8 MPa; the die temperature may be between 50°C and 70°C; and the die time may be between 20 seconds and 40 seconds, but the present invention is not limited thereto. For example, when the thickness, material, and type of the solder mask dry film 1 are different, the required die conditions are also different; therefore, the die pressure, the die temperature, and the die time can be adjusted according to actual needs.

[0036] As described above, under a vacuum environment and appropriate molding conditions (eg, time, temperature, pressure), it can be ensured that the bonding surface 11 of the solder mask dry film 1 and the surface 21 of the substrate 2 are tightly pressed together without any bubbles remaining.

[0037] Furthermore, when no bubbles remain between the solder mask dry film 1 and the substrate 2, the influence of bubbles on the final product can be avoided, the adhesion of the solder mask dry film 1 to the substrate 2 can be improved, and the thickness uniformity of the solder mask dry film 1 can be ensured.

[0038] The step S104 is an exposure step, which includes: using a light beam to photo-cure the solder mask dry film 1 laminated to the substrate 2 to generate the solder mask layer 3 .

[0039] In detail, the solder mask dry film 1 is in a semi-cured state when pressed onto the substrate 2; then, the solder mask dry film 1 is irradiated with the light so that the solder mask dry film 1 is photocured and the solder mask layer 3 is generated, and the solder mask layer 3 does not contain any bubbles.

[0040] Furthermore, at least one expected opening position A is defined on the solder resist dry film 1, and the light will irradiate the solder resist dry film 1 through a mask, and can pass through the mask to avoid the expected opening position A. At this time, the expected opening position A will not be irradiated by the light; thus, the portion of the solder resist dry film 1 that is not irradiated by the light will not generate the solder resist layer 3.

[0041] Among them, in this embodiment, the light is ultraviolet light, but the present invention is not limited to this; for example, any light that can photo-cure the solder mask dry film 1 can be used to irradiate the solder mask dry film 1 to generate the solder mask layer 3.

[0042] The step S105 is a windowing step, which includes: opening a window on the solder mask layer 3 on the substrate 2 through a developer, so that at least one opening H is generated on the solder mask layer 3, and at least one opening H can expose a portion of the surface 21 of the substrate 2.

[0043] Wherein, the developer is at least one of sodium carbonate (Na2CO3) or potassium carbonate (K2CO3).

[0044] It is worth mentioning that Figure 2 As shown, the surface 21 of the substrate 2 includes a solder mask area R1 and at least one soldering area R2; Figure 5 As shown, the solder mask layer 3 is pressed onto the solder mask area R1 of the surface 21 , and the portion exposed by the opening H is the soldering area R2 .

[0045] Further, if Figure 4 and Figure 5 As shown, in the window opening step, when the substrate 2 is immersed in the developer, the developer can dissolve the uncured solder mask dry film 1 on the substrate 2, thereby generating the opening H, and the position of the opening H is approximately located at the expected opening position A. The offset value between the expected opening position A and the corresponding opening H is not greater than 15 microns. In other words, the position deviation between the opening H and the expected opening position A does not exceed 15 microns.

[0046] In this embodiment, if Figure 5 As shown, the opening H includes an opening length L and an opening width W. The opening length L is optionally greater than 190 microns and less than 1000 microns, and the opening length L is more preferably greater than 190 microns and less than 500 microns; the opening width W is optionally greater than 140 microns and less than 950 microns, and the opening width W is more preferably greater than 140 microns and less than 450 microns, but the present invention is not limited thereto. For example, the substrate 2 is usually imported in large quantities, and different customers have different requirements for the opening H. Therefore, the opening length L and the opening width W of the opening H can be adjusted or compensated according to actual needs.

[0047] like Figure 6 As shown, the solder mask 3 is defined to have a maximum thickness Tmax and a minimum thickness Tmin, and a thickness difference between the maximum thickness Tmax and the minimum thickness Tmin is less than 8 microns. Optionally, the thickness difference is less than 6 microns, but the present invention is not limited thereto.

[0048] In detail, when the thickness difference between the maximum thickness Tmax and the minimum thickness Tmin of the solder mask layer 3 is less than 8 microns, the thickness uniformity of the solder mask layer 3 is greater than 92%; when the thickness difference of the solder mask layer 3 is less than 6 microns, the thickness uniformity of the solder mask layer 3 is greater than 93%.

[0049] For example, when the thickness uniformity value is larger, the pressing flatness of the solder mask layer 3 is higher, thereby, in the window opening step, the accuracy of the opening H can be improved; that is, based on the good flatness of the solder mask layer 3, the offset value between the expected opening position A and the opening H can be reduced, and the burrs generated by the opening H due to the window opening step can be reduced.

[0050] Furthermore, the solder mask 3 can fix the distance between the substrate 2 and a chip during subsequent processes, so that the substrate 2 and the chip are not easily poorly installed due to the uneven structure of the traditional solder mask, and the product yield of subsequent processes can be improved.

[0051] In addition, a surface roughness (Ra) of a solder mask surface 31 of the solder mask layer 3 is optionally less than 0.2 microns, and more preferably less than 0.1 microns. In other words, the solder mask layer 3 generated by the solder mask dry film 1 can effectively reduce the surface roughness of the solder mask surface 31. Therefore, when the surface roughness of the solder mask surface 31 decreases, a reflectivity of the solder mask surface 31 can be improved.

[0052] [PCB with solder mask]

[0053] See also Figures 5 and 6 As shown, an embodiment of the present invention provides a circuit board 100 with a solder mask layer, which includes a substrate 2 and a solder mask layer 3 pressed onto a surface 21 of the substrate 2, and the solder mask layer 3 is formed with at least one opening H.

[0054] Specifically, if Figure 2 As shown, the substrate 2 includes a solder mask area R1 and at least one soldering area R2; Figure 5 As shown, the solder mask layer 3 is pressed onto the solder mask area R1 of the surface 21 , and the portion exposed by the opening H is the welding area R2 . In other words, the welding area R2 is not covered by the solder mask layer 3 .

[0055] It is worth mentioning that Figure 6 As shown, the solder mask 3 is defined to have a maximum thickness Tmax and a minimum thickness Tmin, and a thickness difference between the maximum thickness Tmax and the minimum thickness Tmin is less than 8 mm. Optionally, the thickness difference is less than 6 μm, but the present invention is not limited thereto.

[0056] In detail, when the thickness difference between the maximum thickness Tmax and the minimum thickness Tmin of the solder mask layer 3 is less than 8 microns, the thickness uniformity of the solder mask layer 3 is greater than 92%; when the thickness difference of the solder mask layer 3 is less than 6 microns, the thickness uniformity of the solder mask layer 3 is greater than 93%.

[0057] For example, when the thickness uniformity value is larger, the pressing flatness of the solder mask layer 3 is higher. Therefore, the solder mask layer 3 can fix the distance between the substrate 2 and a chip during the subsequent process, so that the substrate 2 and the chip are not easily poorly installed due to the uneven structure of the traditional solder mask, and the product yield of the subsequent process can be improved.

[0058] In addition, a surface roughness (Ra) of a solder mask surface 31 of the solder mask layer 3 is optionally less than 0.2 microns, and more preferably less than 0.1 microns. In other words, the solder mask layer 3 generated by the solder mask dry film 1 can effectively reduce the surface roughness of the solder mask surface 31. Therefore, when the surface roughness of the solder mask surface 31 decreases, a reflectivity of the solder mask surface 31 can be improved.

[0059] [Table 1 Slice test results of the embodiment]

[0060]

[0061] [Example Results and Discussion]

[0062] As shown in Table 1, Examples 1 to 5 are a circuit board 100 having a solder mask layer 3 manufactured using the dry film lamination method of the circuit board of the embodiment of the present invention, and the circuit board 100 is sliced ​​according to the positions of the nine-square grid, and the slice thickness of the solder mask layer 3 at each position is measured.

[0063] It can be seen from Table 1 above that the thickness difference between the maximum thickness and the minimum thickness of Example 1 is 5.642; the thickness difference between the maximum thickness and the minimum thickness of Example 2 is 5.642; the thickness difference between the maximum thickness and the minimum thickness of Example 3 is 2.821; the thickness difference between the maximum thickness and the minimum thickness of Example 4 is 7.052; the thickness difference between the maximum thickness and the minimum thickness of Example 5 is 5.862.

[0064] According to the above test results, it can be known that the circuit board 100 manufactured by the dry film pressing method of the circuit board according to the embodiment of the present invention can reduce the height difference between the maximum thickness and the minimum thickness of the solder mask 3; that is, the thickness uniformity of the solder mask 3 can be improved.

[0065] [Technical Effects of Embodiments of the Invention]

[0066] In summary, the dry film pressing method for a circuit board disclosed in the embodiment of the present invention can reduce the thickness difference between the maximum thickness and the minimum thickness of the solder mask layer through the settings of "a solder mask dry film and a substrate" and "a molding step, pressing a bonding surface of the solder mask dry film to the surface layer of the substrate through a molding machine, and pressing out the bubbles in the solder mask dry film under a vacuum environment through the molding machine; an exposure step, using a light to photo-cure the solder mask dry film bonded to the substrate to generate a solder mask layer", so as to avoid poor contact between the chip and the substrate due to excessive thickness difference during subsequent processing. In addition, the surface roughness can be reduced by the above settings to improve the reflectivity of the solder mask layer.

[0067] The contents disclosed above are only optional feasible embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention description and drawings are included in the patent scope of the present invention.

Claims

1. A dry film lamination method for a circuit board, characterized in that: The dry film lamination method of the circuit board comprises: A pre-step, providing a solder resist dry film and a substrate; a pre-treatment step of cleaning a surface of the substrate; a molding step, in which a bonding surface of the solder mask dry film is pressed onto the surface of the substrate by a molding machine, and bubbles in the solder mask dry film are pressed out by the molding machine under a vacuum environment; an exposure step, using a light to photo-cure the solder mask dry film attached to the substrate to form a solder mask layer; and a window opening step, opening the solder mask on the substrate through a developer, so that at least one opening is formed on the solder mask, and at least one opening can expose a portion of the surface of the substrate; Wherein, after the exposure step, the solder mask layer is defined to have a maximum thickness and a minimum thickness, a thickness difference between the maximum thickness and the minimum thickness is less than 8 microns, and a surface roughness (Ra) of the solder mask layer is less than 0.2 microns.

2. The dry film lamination method for a circuit board according to claim 1, characterized in that: The surface of the substrate includes a solder mask area and at least one soldering area; wherein the solder mask layer is generated on the solder mask area of ​​the surface.

3. The dry film lamination method for a circuit board according to claim 1, characterized in that: The thickness difference between the maximum thickness and the minimum thickness is less than 6 microns.

4. The dry film lamination method for a circuit board according to claim 1, characterized in that: The surface roughness is less than 0.1 micrometer.

5. The dry film lamination method for a circuit board according to claim 1, characterized in that: In the molding step, the molding step includes a molding time, and the molding time is between 20 seconds and 40 seconds.

6. The dry film lamination method for a circuit board according to claim 1, characterized in that: In the molding step, the molding step includes a molding temperature, and the molding temperature is between 50°C and 70°C.

7. The dry film lamination method for a circuit board according to claim 1, characterized in that: In the molding step, the molding step includes a molding pressure, and the molding pressure is between 0.4 Mpa and 0.8 Mpa.

8. The dry film lamination method for a circuit board according to claim 1, characterized in that: The developer in the window opening step is at least one of sodium carbonate and potassium carbonate.

9. The dry film lamination method for a circuit board according to claim 1, characterized in that: At least one expected opening position is defined in the exposure step; wherein an offset value between the expected opening position and the corresponding opening is no greater than 15 microns.

10. The dry film lamination method for a circuit board according to claim 1, characterized in that: In the window opening step, at least one of the openings includes an opening length and an opening width; wherein the opening length is greater than 190 microns and less than 1000 microns, and the opening width is greater than 140 microns and less than 950 microns.

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