Coverlay

Abstract

To provide a coverlay suitable for electronic components. [Solution] The coverlay of the present invention includes an adhesive layer (130) and a protective layer (110). The adhesive layer includes a resin with a chloride ion content of less than 50 ppm. The protective layer covers the adhesive layer. The protective layer is made of a material including polyimide and an inorganic filler. The weight of the inorganic filler is 25 to 50 parts by weight when the total weight of the protective layer is 100 parts by weight. The resistance of the coverlay measured when a voltage of 32 V is applied at a temperature of 85°C, a relative humidity of 85%, and for 1,000 hours exceeds 106 Ω.

Description

[Technical Field]

[0001] The present invention relates to a sheet-like material, and more particularly to a coverlay. [Background technology]

[0002] Advances in circuit board production technology have led to the widespread use of fine-pitch circuit boards with line widths of 35 microns or less and high-density circuit boards with line widths / line spacings of 35 microns / 35 microns or less. However, considering the applications of these circuit boards, how to provide a coverlay with good insulation and appropriate hermeticity (which is difficult to understand by directly observing or photographing the circuit layout of the circuit board) has become a research topic. Summary of the Invention [Problem to be solved by the invention]

[0003] Considering the application of circuit boards, it is necessary to provide a coverlay that has good insulation properties and appropriate hermeticity (for example, the circuit layout of the circuit board is not easily understood by directly observing or photographing it). [Means for solving the problem]

[0004] The present invention provides a coverlay suitable for electronic components.

[0005] The coverlay of the present invention includes an adhesive layer and a protective layer. The adhesive layer includes a resin with a chloride ion content of less than 50 ppm. The protective layer covers the adhesive layer. The protective layer is made of a material including polyimide and an inorganic filler. When the total weight of the protective layer is 100 parts by weight, the weight of the inorganic filler is 25 to 50 parts by weight. The resistance of the coverlay measured under conditions of a temperature of 85°C, a relative humidity of 85%, and for 1000 hours is 10 6 Exceeds Ω.

[0006] In one embodiment of the present invention, the adhesive layer further comprises an inorganic filler, and the weight of the inorganic filler is 5 to 15 parts by weight when the total weight of the adhesive layer is 100 parts by weight.

[0007] In one embodiment of the present invention, the resin comprises polyester, hydrocarbon resin, polyimide, mixtures or copolymers thereof.

[0008] In one embodiment of the present invention, the resistance of the coverlay measured under conditions of a temperature of 85°C, a relative humidity of 85%, and 1000 hours with a voltage of 32 V applied was 10 8 Exceeds Ω.

[0009] In one embodiment of the present invention, the light transmittance of the coverlay is 10% or less.

[0010] In one embodiment of the present invention, the protective layer has a first surface in contact with the adhesive layer and a second surface opposite to the first surface, and the second surface has a lower gloss than the first surface.

[0011] In one embodiment of the present invention, the gloss of the second surface measured at a measurement angle of 60° is less than 5 GU.

[0012] In one embodiment of the present invention, the coverlay further comprises a first release layer, and the adhesive layer is located between the first release layer and the protective layer.

[0013] In one embodiment of the present invention, the coverlay further comprises a second release layer, and the protective layer is located between the second release layer and the adhesive layer. [Effects of the Invention]

[0014] For these reasons, coverlays are suitable for use on electronic components because they have low light transmittance or can obscure objects that are covered by them. [Brief explanation of the drawings]

[0015] [Figure 1A]1 is a schematic cross-sectional view of a partial method for fabricating a coverlay according to an embodiment of the present invention; [Figure 1B] 1 is a partial cross-sectional view showing a schematic diagram of a method for partially fabricating a coverlay according to an embodiment of the present invention; [Figure 2] 1 is a schematic cross-sectional view of a partial method for fabricating a coverlay according to an embodiment of the present invention; [Figure 3] 1 is a schematic cross-sectional view illustrating a method for using a coverlay according to an embodiment of the present invention. [Figure 4] 1 is a schematic cross-sectional view illustrating a method for using a coverlay according to an embodiment of the present invention. [Figure 5] 1 is a schematic cross-sectional view illustrating a method for using a coverlay according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the drawings, some elements or layers may be enlarged for clarity, and like numbers refer to like elements throughout the specification.

[0017] Additionally, relative terms such as "below" or "bottom" and "up" or "top" may be used herein to describe the relationship of one element to another element as shown in the figures. It is understood that the relative terms are intended to encompass different orientations of the device in addition to the orientation shown in the figures. For example, if the device in any of the figures were inverted, an element described as being "below" another element would then be defined as being "up" the other element.

[0018] The method for manufacturing a coverlay of the present invention includes forming a protective layer on a release layer and forming an adhesive layer on the protective layer, wherein the optical transmittance of the laminated protective layer and adhesive layer in the thickness direction is 10% or less, and / or the material of the protective layer contains polyimide and inorganic filler, in which the weight of the inorganic filler is 25 to 50 parts by weight when the total weight of the protective layer is 100 parts by weight.

[0019] 1A and 2 are schematic cross-sectional views of a partial fabrication method of a coverlay according to an embodiment of the present invention. FIG. 1B is a partial cross-sectional view of a partial fabrication method of a coverlay according to an embodiment of the present invention. Specifically, FIG. 1B is an enlarged view corresponding to region R1 in FIG. 1A.

[0020] 1A and 1B, a second release layer 520 is provided.

[0021] In one embodiment, the second release layer 520 has a rough surface and the protective layer 110 formed thereon can have a corresponding roughness, for example, by embossing, carving, grinding, etching, or other suitable method to provide the corresponding roughness on the surface 521 of the second release layer 520.

[0022] Continuing to refer to FIGS. 1A and 1B, a protective layer 110 is formed on the second release layer 520.

[0023] In one embodiment, the protective layer 110 can be formed on the second release layer 520 by coating or other suitable methods. For example, a suitable resin composition can be coated on the second release layer 520 and semi-cured or cured by a suitable method (heating, irradiation, drying, leaving to stand, etc.) to form the corresponding protective layer 110.

[0024] In one embodiment, the application method includes, but is not limited to, dipping coating, roll coating, blade coating, bar coating, slot-die coating, or spray coating.

[0025] In one embodiment, the thickness 110T of the protective layer 110 can range from about 3 micrometers (μm) to about 7 micrometers, for example, about 5 micrometers.

[0026] In one embodiment, the protective layer 110 is formed by coating. Therefore, the outer surface of the protective layer 110 can have a corresponding smooth surface. For example, the first surface 111 of the protective layer 110 can be a smooth surface.

[0027] In one embodiment, protective layer 110 can be formed directly on the roughened surface of second release layer 520. Thus, protective layer 110 can have a correspondingly roughened surface. For example, second surface 112 of protective layer 110 can be roughened.

[0028] In one embodiment, the arithmetic mean deviation (Ra) corresponding to the surfaces is used as a roughness comparison measure, with the roughness of the second surface 112 being greater than the roughness of the first surface 111 .

[0029] In one embodiment, the roughness of a surface can be defined by gloss. Furthermore, when the protective layer 110 is formed using a second release layer 520 (also referred to as a rough release film) having a corresponding rough surface, the gloss of the second surface 112 of the protective layer 110 can correspond to the gloss of the rough surface of the second release layer 520. In one embodiment, the gloss of the second surface 112 of the protective layer 110 can be slightly less than the gloss of the rough surface of the second release layer 520. This may be because subsequent processing is required during the formation of the protective layer 110 and / or the formation of the protective layer 110 does not result in complete contact with the rough surface of the second release layer 520 under microscopic observation. For example, if the second release layer 520 has a rough surface with a gloss of 5 GU (gloss units), the gloss of the corresponding protective layer 110 formed therewith can be 2 GU. The gloss can be measured at a measurement angle of 60°.

[0030] In one embodiment, the glossiness of the second surface 112 is less than the glossiness of the first surface 111 .

[0031] In one embodiment, the material used to form the protective layer 110 may include a polyimide (PI) resin and an inorganic filler. When the total weight of the protective layer 110 is 100 parts by weight, the weight of the inorganic filler used in the protective layer 110 is about 25 parts by weight to about 50 parts by weight. The inorganic filler is in the visible light range and can improve the light scattering chromaticity of the protective layer 110 or reduce the visible light transmittance of the protective layer 110.

[0032] In one embodiment, the inorganic filler used in protective layer 110 may include titanium oxide particles, carbon black particles, iron oxide particles, or a mixture thereof. In one embodiment, the weight of the inorganic filler used in protective layer 110 is about 25 to about 50 parts by weight, when the total weight of protective layer 110 is 100 parts by weight.

[0033] In one embodiment, compared to using organic colorants to reduce light transmittance, the method of adding inorganic fillers improves the hardness or abrasion resistance of the protective layer 110, thereby improving the protective power of the protective layer 110. However, it should be noted that the present invention does not completely exclude the possibility of adding organic colorants.

[0034] 2, an adhesive layer 130 is formed on the first surface 111 of the protective layer 110. The adhesive layer 130 can be formed by any suitable means (described in more detail below).

[0035] In one embodiment, the thickness 130T of the adhesive layer 130 may range from about 5 microns to about 25 microns, for example, about 20 microns.

[0036] In one embodiment, the resin composition used to form the adhesive layer 130 may include a polymer such as polyester, hydrocarbon resin, polyimide (PI), or a mixture or copolymer thereof.

[0037] In one embodiment, the resin composition used to form adhesive layer 130 may further include an inorganic filler. When the total weight of adhesive layer 130 is 100 parts by weight, the weight of the inorganic filler used in adhesive layer 130 is 5 to 15 parts by weight. For example, it is about 5 parts by weight, about 10 parts by weight, about 15 parts by weight, or a value between the two aforementioned values. If the proportion of inorganic filler is too high (e.g., more than 15 parts by weight, or even 20 parts by weight or more), the adhesive strength may decrease.

[0038] In one embodiment, the inorganic filler used in adhesive layer 130 may include titanium oxide particles, carbon black particles, iron oxide particles, or a mixture thereof.

[0039] In one embodiment, the material used to form the adhesive layer 130 essentially does not include epoxy resin or its derivatives. Because epoxy resin cannot completely remove halogen ions (such as chloride ions) during its synthesis, the resin itself contains a high concentration of halogen ions, which may have an electrical effect on the manufactured coverlay 100 and may also affect the applicability of the coverlay 100. For example, epoxy resin may have poor anti-ion migration performance, which may result in a corresponding decrease in resistance and a decrease in insulation properties.

[0040] In one embodiment, the concentration of halogen ions (eg, chloride ions) in adhesion layer 130 can be less than 300 ppm by weight, such as less than 50 ppm.

[0041] In one embodiment, the adhesive layer 130 can be formed by coating or other suitable methods, and the adhesive layer 130 can be formed directly on the protective layer 110 .

[0042] In one embodiment, the adhesive layer 130 may be first formed on the protective layer 110 , and then the release layer 510 may be formed or coated on the adhesive layer 130 formed on the protective layer 110 .

[0043] In one embodiment, the adhesive layer 130 may first be formed on the release layer 510, and then the adhesive layer 130 may be placed opposite the protective layer 110, with the adhesive layer 130 sandwiched and bonded between the protective layer 110 and the release layer 510.

[0044] Basically, the manufacturing of the coverlay 100 of this embodiment can be roughly completed by the above method, but the manufacturing method of the coverlay 100 of this embodiment is not limited to the above method.

[0045] 2, the coverlay 100 includes an adhesive layer 130 and a protective layer 110. The protective layer 110 covers the adhesive layer 130.

[0046] In one embodiment, the optical transmittance of the laminated adhesive layer 130 and protective layer 110 in the coverlay 100 is 10% or less.

[0047] In one embodiment, the material of the protective layer 110 includes polyimide and an inorganic filler. When the total weight of the protective layer 110 is 100 parts by weight, the weight of the inorganic filler is 25 to 50 parts by weight, for example, about 25 parts by weight, about 35 parts by weight, about 50 parts by weight, or a value between the two aforementioned values.

[0048] In one embodiment, protective layer 110 has a first surface 111 and a second surface 112. Second surface 112 faces first surface 111. First surface 111 is in direct contact with adhesive layer 130. In one embodiment, second surface 112 has a lower gloss than first surface 111.

[0049] In one embodiment, the material of adhesive layer 130 includes polyester, hydrocarbon resin, polyimide, or a mixture or copolymer thereof. In one embodiment, the material of adhesive layer 130 can further include an inorganic filler, and the weight of the inorganic filler is 5 to 15 parts by weight when the total weight of adhesive layer 130 is 100 parts by weight.

[0050] In one embodiment, the second surface 112 of the protective layer 110 in the coverlay 100 has a gloss of less than 5 GU, for example, about 2 GU or less, when measured at a 60° measurement angle.

[0051] In one embodiment, when adhesive layer 130 (about 20 microns thick) and protective layer 110 (about 5 microns thick) are measured across the entire sheet (i.e., not including any release layers, as described below), a temperature and humidity bias test is performed at a temperature of 85° C. and a relative humidity of 85 RH for 1000 hours (counted at 85 / 85 1000 hr), measuring the corresponding resistance at a bias voltage of 32 volts, and the resistance exceeds 1 million ohms (10 6 Ω).

[0052] In one embodiment, when the resin contained in the adhesive layer 130 is polyester, hydrocarbon resin, polyimide, a mixture or copolymer thereof, the adhesive layer 130 (thickness: about 20 microns) and the protective layer 110 (thickness: about 5 microns) are measured over the entire sheet (i.e., not including any release layer described below). When a temperature and humidity bias test is performed under conditions of a temperature of 85° C. and a relative humidity of 85 RH for 1000 hours (counted at 85 / 85 1000 hr), the corresponding resistance is measured at a bias voltage of 32 volts, and the resistance is 100 million ohms (10 8 Ω).

[0053] In one embodiment, when the adhesive layer 130 (thickness is about 20 microns) and the protective layer 110 (thickness is about 5 microns) are measured across the entire sheet (i.e., not including any release layers described below), the visible light transmittance is about 10% or less, for example about 9% or less, for example about 7% or less, for example about 5% or less, for example about 3% or less, for example about 0.5% or less, for example about 0.1% or less.

[0054] In one embodiment, the coverlay 100 may further include a first release layer 510. The adhesive layer 130 is located between the first release layer 510 and the protective layer 110. As an example of a method of use, the coverlay 100 may be used by separating the first release layer 510 from the coverlay 100. In other words, the coverlay 100 including the first release layer 510 may be in the form of a product, and the coverlay 100 without the first release layer 510 may be in the form of use.

[0055] In one embodiment, the coverlay 100 may further include a second release layer 520. The protective layer 110 is located between the second release layer 520 and the adhesive layer 130. In one example of a method of use, the coverlay 100 may be used by separating it from the second release layer 520. In other words, the coverlay 100 including the second release layer 520 may be in the form of a product, and the coverlay 100 without the second release layer 520 may be in the form of use.

[0056] 3, 4, or 5 is a schematic cross-sectional view illustrating a method of using a coverlay according to an embodiment of the present invention. It should be noted that the following description and the corresponding drawings are merely examples of a method of using the coverlay 100, and the method of using the coverlay 100 is not limited thereto.

[0057] Referring to FIG. 3, in one embodiment, first release layer 510 (if present) is first separated from adhesive layer 130 to expose the outer surface of adhesive layer 130 for use.

[0058] Referring to FIG. 4, in one embodiment, adhesive layer 130 having an exposed surface can be applied to a suitable object.

[0059] In one embodiment, the adhesive layer 130 of the coverlay 100 can be applied over an electronic component.

[0060] In one embodiment, the aforementioned electronic component is, for example, a circuit board 800. The circuit board 800 may include a corresponding core layer 810 and a circuit layer 820 located on the core layer 810. The circuit layout of the circuit layer 820 can be adjusted according to design requirements and is not limited by the present invention.

[0061] In one embodiment, opposing sides of the core layer 810 may have corresponding circuit layers 820. The corresponding circuits of the circuit layers 820 on the opposing sides may be electrically connected via conductive holes 830 that penetrate the core layer 810.

[0062] In one embodiment, the coverlay 100 has a low light transmittance characteristic, which can reduce the possibility that the circuit layout of the circuit layer 820 can be understood by direct observation or direct photography.

[0063] Referring to FIG. 5, in one embodiment, after the adhesive layer 130 is attached to a suitable object, the second release layer 520 (if present) is separated from the protective layer 110, exposing the second surface 112 of the protective layer 110 for use.

[0064] In one embodiment, the second surface 112 of the coverlay 100 is rough, which can obscure the pattern of the covered object. For example, such obscuration can reduce the likelihood that the circuit layout of the circuit layer 820 can be understood through direct observation or photography.

[0065] [Coverlay application example]

[0066] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to the following examples.

[0067] The optical properties (e.g., light transmittance and gloss) of the coverlay in each of the following examples were measured when the coverlay included the laminated adhesive layer and protective layer (i.e., when no corresponding release layer was present). The coverlay was then attached to the same or a similar circuit board (the same or similar to that shown in FIG. 5 ), and the corresponding electrical properties were measured. The circuit board was a high-density circuit board or a fine-pitch circuit board with at least a line width of about 20 microns and a line spacing of about 20 microns (counted at L / S=20 / 20).

[0068] The coverlay structures (e.g., thickness) of the examples are essentially the same or similar, with the difference being in the material composition. Specifically, the thickness of the adhesive layer of the coverlay of each example is essentially 20 microns, and the thickness of the protective layer of the coverlay of each example is essentially 5 microns. The adhesive layer and protective layer of the coverlay of each example may also have different material compositions. For example, in Example 8, the resin composition of the adhesive layer is polyester, and when the total weight of the adhesive layer is 100 parts by weight, the weight of the inorganic filler used in the adhesive layer is 5 parts by weight. The resin composition of the protective layer is polyimide (PI), and when the total weight of the protective layer is 100 parts by weight, the weight of the inorganic filler used in the protective layer is 25 parts by weight. Taking Example 19 as an example, the resin composition of the adhesive layer is a hydrocarbon resin, and when the total weight of the adhesive layer is 100 parts by weight, the weight of the inorganic filler used in the adhesive layer is 5 parts by weight, and the resin composition of the protective layer is polyimide (PI), and when the total weight of the protective layer is 100 parts by weight, the weight of the inorganic filler used in the protective layer is 35 parts by weight.

[0069] The coverlay materials and measurement results for each example are shown in Table 1. The corresponding inorganic filler in Table 1 is titanium oxide particles, and the units are parts by weight (wt%).

[0070] [Table 1]

[0071] Electrical characteristics measurement: Temperature and humidity bias test (THB) was performed under the conditions of temperature 85°C, relative humidity 85RH for 1000 hours (counted at 85 / 85 1000hr), and a bias voltage of 32 volts, measuring the corresponding resistance. The resistance value was 1 million ohms (10 6 Ω), the electrical characteristics test is considered to have passed (counted as a pass). 6 Ω) or less, the electrical characteristics test is deemed to have failed (counted as NG).

[0072] Optical characteristic measurement: Using a commercially available gloss meter, the gloss of the laminated adhesive layer and protective layer was measured at a measurement angle of approximately 60° toward the outer surface of the protective layer (for example, the second surface mentioned above).

[0073] Measurement of optical properties: Using a commercially available optical transmittance measuring device, the transmittance in the visible light region of the laminated adhesive layer and protective layer was measured.

[0074] For example, as shown in Examples 2 to 10, 12 to 15, and 17 to 23 in Table 1, by adding an inorganic filler to the material of the protective layer and / or the material of the adhesive layer, the coverlay can be given low light transmittance (e.g., light transmittance of about 10% or less).

[0075] As shown in Examples 1 to 20 in Table 1, polyester, hydrocarbon resin, and polyimide (PI) are used as the main materials for the adhesive layers in the coverlay, and the ion content (e.g., chloride ion content) therein is less than 50 ppm. Therefore, the coverlay has electrical properties suitable for insulation (e.g., 10 6The resistor may have a resistance greater than Ω.

[0076] As shown in Examples 1-4, 8-14, 16-19, and 21-22 in Table 1, the coverlay manufacturing process uses a corresponding rough release layer (e.g., a rough release layer with a gloss level of 5 GU or less), which allows the coverlay to have a low gloss level (e.g., a gloss level of less than 5 GU).

[0077] As shown in Examples 2 to 4, 8 to 10, 12 to 14, and 17 to 19 in Table 1, the adhesive layers in the coverlays use polyester, hydrocarbon resin, or polyimide (PI) as the main material for the corresponding adhesive layers, and an inorganic filler is added to the material of the protective layer and / or the material of the adhesive layer, and a corresponding rough release layer (e.g., a rough release layer with a gloss level of 5 GU or less) is used. Therefore, the coverlays have low light transmittance (e.g., light transmittance of about 10% or less), low gloss (e.g., gloss level of about 5 GU or less), and electrical properties suitable for insulation (e.g., 10 6 The resistor may have a resistance greater than Ω.

[0078] In summary, the coverlay of the present invention has low light transmittance, or can obscure the covered object, making it suitable for electronic components. [Industrial Applicability]

[0079] The coverlay of the present invention has low light transmittance, or can obscure the covered object, making it suitable for electronic components. Furthermore, when applied to a circuit board, the coverlay of the present invention can provide good insulation and adequate hermeticity (e.g., the circuit layout of the circuit board cannot be easily understood by direct observation or photography). [Explanation of symbols]

[0080] 100: Coverlay 110: Protective layer 111: 1st surface 112:Second surface 110T: Thickness 130: Adhesive layer 130T: Thickness 510: First release layer 520:Second release layer 521: Surface 800: Circuit board 810: Core layer 820:Circuit layer 830: Conductive hole R1: area

Claims

1. an adhesive layer containing a resin having a chloride ion content of less than 50 ppm; a protective layer covering the adhesive layer, The material of the protective layer is Polyimide and a first inorganic filler having a weight of 25 parts by weight to 50 parts by weight when the total weight of the protective layer is 100 parts by weight; The resistance value measured under the conditions of a temperature of 85°C, a relative humidity of 85%, and 1000 hours by applying a voltage of 32 V was 10 ６ Beyond Ω, the adhesive layer further contains a second inorganic filler, and the weight of the second inorganic filler is 5 parts by weight to 15 parts by weight when the total weight of the adhesive layer is 100 parts by weight; The coverlay, wherein the adhesive layer does not include an epoxy resin.

2. The coverlay of claim 1 , wherein the resin comprises a polyester, a hydrocarbon resin, a polyimide, or a mixture or copolymer thereof.

3. The resistance value measured under the conditions of a temperature of 85°C, a relative humidity of 85%, and 1000 hours by applying a voltage of 32 V was 10 ８ The coverlay of claim 2 , wherein the thickness exceeds Ω.

4. The coverlay of claim 1 having a light transmittance of 10% or less.

5. 2. The coverlay of claim 1, wherein the protective layer has a first surface in contact with the adhesive layer and a second surface opposite the first surface, the second surface having a lower gloss than the first surface.

6. 6. The coverlay of claim 5, wherein the second surface has a gloss of less than 5 GU measured at a 60° measurement angle.

7. The coverlay of claim 1 , further comprising a first release layer, the adhesive layer being located between the first release layer and the protective layer.

8. The coverlay of claim 1 , further comprising a second release layer, the protective layer being located between the second release layer and the adhesive layer.

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