Protective film, preparation method thereof and application of protective film in PCB (Printed Circuit Board) drilling cover plate

Abstract

The invention relates to the technical field of protective films, and provides a protective film, a preparation method of the protective film and application of the protective film in a PCB drilling cover plate. The protective film comprises an outer layer, a middle layer and an inner layer, the outer layer is prepared from low-density polyethylene and linear medium-density polyethylene, and the middle layer is prepared from low-density polyethylene; and the inner layer is prepared from the following raw materials: linear low-density polyethylene, high-density polyethylene and matte master batch. The protective film provided by the invention has the advantages that the attaching property of the protective film and the PCB drilling cover plate is good, bubbles are not easy to appear, wire drawing is not easy to occur during drilling, a drill bit is not damaged, the haze of the protective film is relatively high, reflection and glare are not generated during drilling, and the requirements of the drilling process are met.

Description

Technical Field

[0001] The invention relates to the technical field of composite films, and in particular to a protective film and a preparation method thereof, and application thereof in a PCB drilling cover plate. Background Art

[0002] PCB (Printed Circuit Board) drilling cover is an auxiliary material used in the manufacturing process of PCB (Printed Circuit Board). It is mainly placed on the surface of the PCB board to play multiple functions such as protection, positioning and guidance during drilling operations. During the drilling process, the drilling equipment and drill bit will frequently contact the cover, which may leave scratches, wear and other marks on the surface of the cover, affecting the flatness and finish of the cover, and thus affecting its performance and life.

[0003] In order to extend the service life of the cover plate, a protective film is usually set on the surface of the cover plate. Common PCB drilling cover plate protective films include PET protective film, PE protective film, etc. Although the current protective film can protect the cover plate to a certain extent, it is easy for the film to not fit tightly with the cover plate, resulting in bubbles. At the same time, the tensile strength of the film is too high, resulting in the drill bit driving the wire. The above phenomena will affect the drilling process and easily cause damage to the drill bit. Summary of the invention

[0004] In view of this, the present invention provides a protective film and a preparation method thereof and an application in a PCB drilling cover plate. The drilling cover plate protective film provided by the present invention is tightly attached to the circuit board, has an appropriate tensile strength, is not prone to wire drawing during drilling, and will not damage the drill bit.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A protective film comprises an outer layer, a middle layer and an inner layer;

[0007] The outer layer is prepared from raw materials including, by weight: 50 to 90 parts of low-density polyethylene and 10 to 50 parts of linear medium-density polyethylene;

[0008] The raw material for preparing the middle layer is low-density polyethylene;

[0009] Calculated by weight, the raw materials for preparing the inner layer include: 30 to 80 parts of linear low-density polyethylene, 20 to 50 parts of high-density polyethylene, and 10 to 30 parts of matte masterbatch.

[0010] Preferably, the melt index of the low-density polyethylene used in the outer layer and the middle layer is independently 1.5-2.5 g / 10 min; the density is independently 0.92-0.93 g / cm 3 .

[0011] Preferably, the linear medium density polyethylene used in the outer layer has a melt index of 5 to 8 g / 10 min and a density of 0.93 to 0.95 g / cm 3 .

[0012] Preferably, the linear low-density polyethylene used in the inner layer has a melt index of 1.5 to 2.5 g / 10 min and a density of 0.915 to 0.925 g / cm 3 The high-density polyethylene has a melt index of 5 to 8 g / 10 min and a density of 0.95 to 0.97 g / cm 3 ;

[0013] The matte masterbatch has a melt index of 5 to 8 g / 10 min and a density of 1.2 to 1.5 g / cm 3 .

[0014] Preferably, the brand of low-density polyethylene used in the outer layer and the middle layer is 2420H; the brand of linear medium-density polyethylene used in the outer layer is 81841.27.

[0015] Preferably, the brand of the linear low-density polyethylene used in the inner layer is 201XV; the brand of the high-density polyethylene is H377C; and the brand of the matte masterbatch is 101763-K.

[0016] The present invention also provides a method for preparing the protective film described in the above scheme, comprising the following steps: co-extruding the raw materials for preparing the outer layer, the middle layer and the inner layer to obtain the protective film.

[0017] Preferably, the three-layer co-extrusion comprises: feeding the raw materials for the outer layer, the middle layer and the inner layer into the outer layer, the middle layer and the inner layer extruders respectively for melting and plasticizing, conveying the obtained glue solution to the die head, extruding and blowing the film to obtain a film bubble, and after the film bubble is air-cooled, passing through a stabilizing ring and a herringbone arrangement to be pulled upward for rotation, and after the film bubble is flattened, it is inspected, trimmed, destaticized and rolled to obtain the protective film.

[0018] Preferably, the outer layer extruder, the middle layer extruder and the inner layer extruder are all provided with 5 heating zones, which are recorded as zones 1 to 5 in the order in which the raw materials pass; the temperature of zone 1 of the outer layer extruder is 160-170°C, the temperature of zone 2 is 165-175°C, the temperature of zone 3 is 165-175°C, the temperature of zone 4 is 165-175°C, and the temperature of zone 5 is 165-175°C; the temperature of zone 1 of the middle layer extruder is 150~160℃, the temperature of zone 2 is 150~160℃, the temperature of zone 3 is 150~160℃, the temperature of zone 4 is 150~160℃, and the temperature of zone 5 is 150~160℃; the temperature of zone 1 of the inner layer extruder is 165~175℃, the temperature of zone 2 is 170~180℃, the temperature of zone 3 is 170~180℃, the temperature of zone 4 is 170~180℃, and the temperature of zone 5 is 170~180℃;

[0019] The die head is provided with 4 heating zones, which are respectively recorded as zones 1 to 4 according to the order in which the raw materials pass through; the temperature of zone 1 of the die head is 170-180°C, the temperature of zone 2 is 170-180°C, the temperature of zone 3 is 170-180°C, and the temperature of zone 4 is 170-180°C.

[0020] The present invention also provides the use of the protective film described in the above scheme or the protective film prepared by the preparation method described in the above scheme in a PCB drilling cover plate.

[0021] The present invention provides a protective film, including an outer layer, a middle layer and an inner layer; in terms of mass fractions, the raw materials for preparing the outer layer include: 50 to 90 parts of low-density polyethylene, 10 to 50 parts of linear medium-density polyethylene, and the raw materials for preparing the middle layer are low-density polyethylene; in terms of mass fractions, the raw materials for preparing the inner layer include: 30 to 80 parts of linear low-density polyethylene, 20 to 50 parts of high-density polyethylene, and 10 to 30 parts of matte masterbatch. The present invention adopts low-density polyethylene as the middle layer material, which can adjust the tensile strength of the protective film, improve the die-cutting performance of the protective film, and avoid the phenomenon of wire drawing during drilling; at the same time, the present invention can improve the bonding performance of the protective film by controlling the types and proportions of the raw materials for preparing each layer, so that the obtained protective film can be closely bonded to the PCB drilling cover plate to avoid bubbles. In addition, during the PCB drilling process, it is necessary to observe the drilling situation through the lighting device on the drilling equipment. The current protective film has a low haze, which is prone to reflection and glare, and will interfere with the operator's vision. The present invention adds matte masterbatch to the inner layer of the protective film to improve the haze of the protective film and meet the requirements of the drilling process. DETAILED DESCRIPTION

[0022] The present invention provides a protective film, comprising an outer layer, a middle layer and an inner layer;

[0023] In terms of weight, the raw materials for preparing the outer layer include: 50 to 90 parts of low-density polyethylene, 10 to 50 parts of linear medium-density polyethylene,

[0024] The raw material for preparing the middle layer is low-density polyethylene;

[0025] Calculated by weight, the raw materials for preparing the inner layer include: 30 to 80 parts of linear low-density polyethylene, 20 to 50 parts of high-density polyethylene, and 10 to 30 parts of matte masterbatch.

[0026] In terms of mass fraction, the raw material for preparing the outer layer includes 50 to 90 parts of low-density polyethylene, specifically 60 parts, 70 parts or 80 parts; the melt index of the low-density polyethylene used in the outer layer is preferably 1.5 to 2.5 g / 10 min, more preferably 2 to 2.5 g / 10 min, and the density is preferably 0.92 to 0.93 g / cm 3 , more preferably 0.924 to 0.925 g / cm 3 In a specific embodiment of the present invention, the outer layer uses a low-density polyethylene grade of 2420H, which is produced by CNOOC Shell, has a melt index of 2g / 10min and a density of 0.924g / cm 3 The low-density polyethylene used in the outer layer of the present invention has the characteristics of high cleanliness, good die-cutting and easy processing.

[0027] Based on the weight percentage of low-density polyethylene used in the outer layer, the raw material for preparing the outer layer includes 10 to 50 parts of linear medium-density polyethylene, specifically 20 parts, 30 parts or 40 parts; the melt index of the linear medium-density polyethylene is preferably 5 to 8 g / 10min, more preferably 6 to 7 g / 10min, and the density is preferably 0.93 to 0.95 g / cm 3 , more preferably 0.94 to 0.947 g / cm 3 In a specific embodiment of the present invention, the grade of the linear medium density polyethylene is 81841.27, its manufacturer is Dow Chemical, the melt index is 6g / 10min, and the density is 0.947g / cm 3 The linear medium density polyethylene used in the present invention has the characteristics of high composite strength and good die cutting.

[0028] In the present invention, the raw material for preparing the middle layer is low-density polyethylene, and the melt index of the low-density polyethylene used in the middle layer is preferably 1.5-2.5 g / 10 min, more preferably 2-2.5 g / 10 min, and the density is preferably 0.92-0.93 g / cm 3 , more preferably 0.924 to 0.925 g / cm 3In a specific embodiment of the present invention, the outer layer uses a low-density polyethylene grade of 2420H, which is produced by CNOOC Shell, has a melt index of 2g / 10min and a density of 0.924g / cm 3 The low-density polyethylene used in the middle layer of the present invention has the characteristics of high cleanliness, good die-cutting and easy processing.

[0029] In terms of mass fraction, the raw material for preparing the inner layer includes 30 to 80 parts of linear low-density polyethylene, specifically 50 parts, 60 parts or 70 parts; the melt index of the linear low-density polyethylene is preferably 1.5 to 2.5 g / 10 min, more preferably 1.5 to 2 g / 10 min, and the density is preferably 0.915 to 0.925 g / cm 3 , more preferably 0.918 to 0.92 g / cm 3 In a specific embodiment of the present invention, the grade of the linear low-density polyethylene is 201XV, its manufacturer is Exxon, its melt index is 2g / 10min, and its density is 0.918g / cm 3 The high-density polyethylene used in the present invention has the characteristics of low crystal point, high stiffness and good die-cutting properties.

[0030] Based on the mass fraction of the linear low-density polyethylene used in the inner layer, the raw material for preparing the inner layer includes 20 to 50 parts of high-density polyethylene, specifically 20 parts, 25 parts or 30 parts; the melt index of the high-density polyethylene is preferably 5 to 8 g / 10min, more preferably 6 to 7 g / 10min, and the density is preferably 0.95 to 0.97 g / cm 3 , more preferably 0.96 to 0.964 g / cm 3 In a specific embodiment of the present invention, the grade of the high-density polyethylene is H377C, its manufacturer is Siam, Thailand, the melt index is 7g / 10min, and the density is 0.964g / cm 3 . It has good compatibility and good processability.

[0031] Based on the mass fraction of the linear low-density polyethylene used in the inner layer, the raw material for preparing the inner layer includes 10 to 30 parts of matte masterbatch, specifically 20 parts or 25 parts; the melt index of the matte masterbatch is preferably 5 to 8 g / 10min, and the density is 1.2 to 1.5 g / cm 3 In a specific embodiment of the present invention, the matte masterbatch is of grade 101763-K, manufactured by Anpi, with a melt index of 7g / 10min and a density of 1.37g / cm 3 The matte masterbatch used in the present invention has the characteristics of high haze, good compatibility and easy processing.

[0032] In the present invention, taking the total mass of the outer layer, the middle layer and the inner layer as 100%, the mass fraction of the outer layer is preferably 20-30%, more preferably 25%, the mass fraction of the middle layer is preferably 40-60%, more preferably 50%, and the mass fraction of the inner layer is preferably 20-30%, more preferably 25%.

[0033] In the present invention, the longitudinal tensile strength of the protective film is preferably 20-22.5 MPa, the transverse tensile strength is preferably 18-19.5 MPa, the longitudinal elongation at break is preferably 230-260%, the transverse elongation at break is preferably 550-580%, and the haze is preferably 43-48%.

[0034] In the present invention, the thickness of the protective film is preferably 40 to 60 μm, more preferably 50 μm.

[0035] The present invention also provides a method for preparing the protective film described in the above scheme, comprising the following steps: co-extruding the raw materials for preparing the outer layer, the middle layer and the inner layer to obtain the protective film.

[0036] In the present invention, the three-layer co-extrusion preferably includes: feeding the raw materials for the outer layer, the middle layer and the inner layer into the outer layer, the middle layer and the inner layer extruders respectively for melting and plasticization, conveying the obtained glue solution to the die head, extruding and blowing the film to obtain a film bubble, and after the film bubble is air-cooled, passing through a stabilizing ring and a herringbone arrangement to be pulled upward for rotation, and after the film bubble is flattened, it is inspected, trimmed, destaticized and rolled to obtain the protective film.

[0037] In the present invention, the outer layer extruder, the middle layer extruder and the inner layer extruder are all provided with 5 heating zones, which are recorded as zones 1 to 5 in the order in which the raw materials pass; the temperature of zone 1 of the outer layer extruder is preferably 160-170°C, more preferably 165°C, the temperature of zone 2 is preferably 165-175°C, more preferably 170°C, the temperature of zone 3 is preferably 165-175°C, more preferably 170°C, the temperature of zone 4 is preferably 165-175°C, more preferably 170°C, and the temperature of zone 5 is preferably 165-175°C, more preferably 170°C; the temperature of zone 1 of the middle layer extruder is preferably 150-160°C, more preferably 150°C, and the temperature of zone 2 is preferably The temperature of zone 1 of the inner layer extruder is preferably 165-175°C, more preferably 170°C, the temperature of zone 2 is preferably 170-180°C, more preferably 180°C, the temperature of zone 3 is preferably 170-180°C, more preferably 180°C, the temperature of zone 4 is preferably 170-180°C, more preferably 175°C, and the temperature of zone 5 is preferably 170-180°C, more preferably 175°C.

[0038] In the present invention, the die head is preferably provided with 4 heating zones, which are sequentially recorded as zones 1 to 4 according to the order in which the raw materials pass; the temperature of zone 1 of the die head is preferably 170-180°C, more preferably 175°C, the temperature of zone 2 is preferably 170-180°C, more preferably 175°C, the temperature of zone 3 is preferably 170-180°C, more preferably 180°C, and the temperature of zone 4 is preferably 170-180°C, more preferably 180°C.

[0039] In the present invention, the extrusion pressure of the outer layer extruder is preferably 150-500 bar, more preferably 300-350 bar, the extrusion pressure of the middle layer extruder is preferably 150-500 bar, more preferably 300-320 bar, and the extrusion pressure of the inner layer extruder is preferably 200-500 bar, more preferably 400-420 bar.

[0040] In the present invention, the inspection is preferably performed by inspecting the appearance and crystal points of the film through a crystal point defect detector; after the inspection is completed, the edges are trimmed, and then the single sheets are separated by the lower traction roller and enter the static electricity removal device for static electricity removal, and then rolled up by the front and rear winding devices to obtain the protective film of the present invention.

[0041] The present invention also provides the use of the protective film described in the above scheme or the protective film prepared by the preparation method described in the above scheme in a PCB drilling cover plate. In the present invention, the protective film is specifically used as a protective film for a PCB drilling cover plate, which can protect the PCB drilling cover plate, fits tightly with the cover plate without bubbles, is not easy to draw wires during drilling, does not damage the drill bit, and has a high haze, which does not affect the operator's line of sight during drilling.

[0042] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] A protective film is made of a co-extruded blown film of an outer layer, a middle layer and an inner layer. The weight percentages of the materials of each layer are: 25% for the outer layer, 50% for the middle layer and 25% for the inner layer; the raw material ratios of each layer are shown in Table 1, and the thickness of the protective film is 50 μm.

[0045] Table 1 Example 1 Raw material ratio

[0046]

[0047] The preparation method of the protective film is as follows: the raw materials of the outer layer, the middle layer and the inner layer are mixed in proportion by an automatic batching system, and then sent to the outer layer, the middle layer and the inner layer extruders; the raw materials of the outer layer, the middle layer and the inner layer are melted and plasticized and then sent to the die head for extrusion and blown film; and then cooled by air cooling, and the film is flattened by the upper traction rotation through a stabilizing ring and a herringbone arrangement. The film cooled by the guide roller enters the crystal point defect detector to detect the appearance and crystal points of the film, and then the trimming is separated by the lower traction roller into a single sheet and enters the static elimination device and the front and rear winding device for winding, so as to obtain the protective film; the temperature and pressure of the outer layer, the middle layer and the inner layer extruders and the temperature of the die head are shown in Table 2.

[0048] Table 2 Extruder temperature and pressure and die head temperature

[0049]

[0050] Example 2

[0051] A protective film is made of a co-extruded blown film of an outer layer, a middle layer and an inner layer. The weight percentages of the materials of each layer are: 25% for the outer layer, 50% for the middle layer and 25% for the inner layer. The amount of raw materials used for each layer is shown in Table 3. The thickness of the protective film is 50 μm.

[0052] Table 3 Example 2 Raw material ratio

[0053]

[0054]

[0055] The preparation method is the same as that in Example 1.

[0056] Example 3

[0057] A protective film is made of a co-extruded blown film of an outer layer, a middle layer and an inner layer. The weight percentages of the materials of each layer are: 25% for the outer layer, 50% for the middle layer and 25% for the inner layer. The amount of raw materials used for each layer is shown in Table 4. The thickness of the protective film is 50 μm.

[0058] Table 4 Example 3 Raw material ratio

[0059]

[0060] The preparation method is the same as that of Example 3.

[0061] Comparative Example 1

[0062] A PCB drilling cover plate protective film is made of a co-extruded blown film of an outer layer, a middle layer and an inner layer. The weight percentages of the materials of each layer are: 25% for the outer layer, 50% for the middle layer and 25% for the inner layer. The amount of raw materials used for each layer is shown in Table 5. The thickness of the protective film is 50 μm.

[0063] Table 5 Comparative Example 1 Raw Material Ratio

[0064]

[0065] The preparation method is the same as that of Example 1

[0066] Comparative Example 2

[0067] A PCB drilling cover plate protective film is made of a co-extruded blown film of an outer layer, a middle layer and an inner layer. The weight percentages of the materials of each layer are: 25% for the outer layer, 50% for the middle layer and 25% for the inner layer. The amount of raw materials used for each layer is shown in Table 6. The thickness of the protective film is 50 μm.

[0068] Table 6 Comparative Example 2 Raw Material Ratio

[0069]

[0070] The preparation method is the same as that in Example 1.

[0071] Performance Test:

[0072] The tensile strength, elongation at break, haze and die-cutting conditions of the protective films prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested. The test results are shown in Table 7.

[0073] Table 7 Performance test results

[0074]

[0075] According to the test results in Table 7, it can be seen that the protective film prepared by the present invention has suitable tensile strength and high haze, and at the same time has good die-cutting characteristics and is not easy to draw; while the protective film prepared in Comparative Example 1 has large tensile strength and is not easy to die-cut, and the protective film prepared in Comparative Example 2 has low haze and cannot meet the drilling requirements.

[0076] In addition, the protective films prepared in Examples 1 to 3 were applied to PCB drilling cover plates, and drilling experiments were carried out. The results showed that the protective film and the cover plate surface were tightly attached, no bubbles appeared, no wire drawing occurred during drilling, the drill bit was not easily damaged, and the haze was high, no reflection and glare were generated, the drilling situation could be clearly observed, and the line of sight was not affected.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A protective film, characterized in that: It includes outer layer, middle layer and inner layer; The outer layer is prepared from raw materials including, by weight: 50 to 90 parts of low-density polyethylene and 10 to 50 parts of linear medium-density polyethylene; The raw material for preparing the middle layer is low-density polyethylene; Calculated by weight, the raw materials for preparing the inner layer include: 30 to 80 parts of linear low-density polyethylene, 20 to 50 parts of high-density polyethylene, and 10 to 30 parts of matte masterbatch.

2. The protective film according to claim 1, characterized in that: The melt index of the low-density polyethylene used in the outer layer and the middle layer is independently 1.5-2.5 g / 10 min; the density is independently 0.92-0.93 g / cm 3 .

3. The protective film according to claim 1, characterized in that: The linear medium density polyethylene used in the outer layer has a melt index of 5 to 8 g / 10 min and a density of 0.93 to 0.95 g / cm 3 .

4. The protective film according to claim 1, characterized in that: The linear low-density polyethylene used in the inner layer has a melt index of 1.5-2.5 g / 10 min and a density of 0.915-0.925 g / cm 3 The high-density polyethylene has a melt index of 5 to 8 g / 10 min and a density of 0.95 to 0.97 g / cm 3 ; The matte masterbatch has a melt index of 5 to 8 g / 10 min and a density of 1.2 to 1.5 g / cm 3 .

5. The protective film according to claim 1, characterized in that: The grade of the low-density polyethylene used in the outer layer and the middle layer is 2420H; the grade of the linear medium-density polyethylene used in the outer layer is 81841.

27.

6. The protective film according to claim 1, characterized in that: The brand of the linear low-density polyethylene used in the inner layer is 201XV; the brand of the high-density polyethylene is H377C; and the brand of the matte masterbatch is 101763-K.

7. The method for preparing the protective film according to any one of claims 1 to 6, comprising the following steps: The raw materials for preparing the outer layer, the middle layer and the inner layer are subjected to three-layer co-extrusion to obtain the protective film.

8. The preparation method according to claim 7, characterized in that: The three-layer co-extrusion comprises: feeding the raw materials for the outer layer, the middle layer and the inner layer into the outer layer, the middle layer and the inner layer extruders respectively for melting and plasticizing, conveying the obtained glue solution to the die head, extruding and blowing the film to obtain a film bubble, cooling the film bubble with air, passing through a stabilizing ring and a herringbone arrangement to be pulled upward for rotation, flattening the film bubble, conducting inspection, trimming, removing static electricity and winding, and obtaining the protective film.

9. The preparation method according to claim 8, characterized in that: The outer layer extruder, the middle layer extruder and the inner layer extruder are all provided with 5 heating zones, which are recorded as zones 1 to 5 in the order in which the raw materials pass through; the temperature of zone 1 of the outer layer extruder is 160-170°C, the temperature of zone 2 is 165-175°C, the temperature of zone 3 is 165-175°C, the temperature of zone 4 is 165-175°C, and the temperature of zone 5 is 165-175°C; the temperature of zone 1 of the middle layer extruder is 15 0~160℃, the temperature of zone 2 is 150~160℃, the temperature of zone 3 is 150~160℃, the temperature of zone 4 is 150~160℃, and the temperature of zone 5 is 150~160℃; the temperature of zone 1 of the inner layer extruder is 165~175℃, the temperature of zone 2 is 170~180℃, the temperature of zone 3 is 170~180℃, the temperature of zone 4 is 170~180℃, and the temperature of zone 5 is 170~180℃; The die head is provided with 4 heating zones, which are respectively recorded as zones 1 to 4 according to the order in which the raw materials pass through; the temperature of zone 1 of the die head is 170-180°C, the temperature of zone 2 is 170-180°C, the temperature of zone 3 is 170-180°C, and the temperature of zone 4 is 170-180°C.

10. Use of the protective film according to any one of claims 1 to 6 or the protective film prepared by the preparation method according to any one of claims 7 to 9 in a PCB drilling cover plate.

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