A protective film, a method for manufacturing the same, and an application thereof in a PCB drilling cover plate

Abstract

The present application relates to the technical field of protective film, and provides a protective film, a preparation method thereof and application 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, the middle layer is prepared from low-density polyethylene, and the inner layer is prepared from linear low-density polyethylene, high-density polyethylene and matte master batch, the protective film and the PCB drilling cover plate are good in adhesion, bubbles are not prone to occur, and the protective film is not prone to wire drawing during drilling, the drill bit is not damaged, the protective film has high haze, reflection and glare are not generated during drilling, and the requirements of the drilling process are met.

Description

Technical Field

[0001] This invention relates to the field of composite film technology, and more particularly to a protective film, its preparation method, and its application in PCB drilling cover plates. Background Technology

[0002] A PCB (Printed Circuit Board) drill cover is an auxiliary material used in the manufacturing process of PCBs. It is primarily placed on the surface of the PCB to provide protection, positioning, and guidance during drilling operations. During drilling, the drilling equipment and drill bit frequently come into contact with the cover, potentially leaving scratches and abrasions on its surface. This affects the cover's flatness and smoothness, consequently impacting its performance and lifespan.

[0003] To extend the lifespan of the cover plate, a protective film is usually applied to its surface. Common protective films for PCB drilling cover plates include PET protective film and PE protective film. Although the current protective films can provide some protection for the cover plate, they are prone to poor adhesion between the film and the cover plate, resulting in air bubbles. At the same time, if the tensile strength of the film is too high, it can cause the drill bit to pull out the threads. All of these phenomena can affect the drilling process and easily damage the drill bit. Summary of the Invention

[0004] In view of this, the present invention provides a protective film, a method for preparing the same, and its application in PCB drilling cover plates. The drilling cover plate protective film provided by the present invention adheres tightly to the circuit board, has suitable tensile strength, is not prone to stringing during drilling, and will not damage the drill bit.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

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

[0007] The raw materials for preparing the outer layer, by mass parts, include: 50-90 parts of low-density polyethylene and 10-50 parts of linear medium-density polyethylene;

[0008] The middle layer is made from low-density polyethylene.

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

[0010] Preferably, the low-density polyethylene used in the outer and middle layers has a melt index of 1.5–2.5 g / 10 min and a density of 0.92–0.93 g / cm³. 3 .

[0011] Preferably, the linear medium-density polyethylene used in the outer layer has a melt index of 5-8 g / 10 min and a density of 0.93-0.95 g / cm³. 3 .

[0012] Preferably, 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 / cm³. 3 The high-density polyethylene has a melt index of 5–8 g / 10 min and a density of 0.95–0.97 g / cm³. 3 ;

[0013] The matte masterbatch has a melt index of 5–8 g / 10 min and a density of 1.2–1.5 g / cm³. 3 .

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

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

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

[0017] Preferably, the three-layer co-extrusion includes: feeding the raw materials for the preparation of the outer layer, middle layer and inner layer into the outer layer, middle layer and inner layer extruders respectively for melt plasticization, conveying the resulting adhesive liquid to the die head, extruding and blowing film to obtain a film bubble, the film bubble being cooled by air and then traction and rotated by a stabilizing ring and a herringbone pattern, flattening the film bubble and then inspecting, trimming the edges, removing static electricity and winding it up to obtain the protective film.

[0018] Preferably, the outer extruder, middle extruder, and inner extruder are each equipped with five heating zones, numbered 1 to 5 according to the order in which the raw materials pass through. The temperature of zone 1 in the outer extruder is 160–170°C, zone 2 is 165–175°C, zone 3 is 165–175°C, zone 4 is 165–175°C, and zone 5 is 165–175°C. The temperature of zone 1 in the middle extruder is… The temperatures in zones 1, 2, 3, 4, and 5 of the inner extruder are 150–160°C, 165–175°C, 170–180°C, 170–180°C, 170–180°C, and 170–180°C respectively.

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

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

[0021] This invention provides a protective film comprising an outer layer, a middle layer, and an inner layer. By weight, the outer layer is prepared from 50-90 parts of low-density polyethylene and 10-50 parts of linear medium-density polyethylene; the middle layer is prepared from low-density polyethylene. By weight, the inner layer is prepared from 30-80 parts of linear low-density polyethylene, 20-50 parts of high-density polyethylene, and 10-30 parts of matte masterbatch. This invention uses low-density polyethylene as the middle layer material, which can adjust the tensile strength of the protective film, improve its die-cutting performance, and prevent stringing during drilling. Simultaneously, by controlling the types and proportions of raw materials for each layer, this invention can improve the adhesion performance of the protective film, ensuring a tight bond between the resulting protective film and the PCB drilling cover plate, preventing air bubbles. In addition, during PCB drilling, the drilling process requires the use of lighting devices on the drilling equipment to observe the drilling status. Current protective films have low haze, which easily causes reflection and glare, interfering with the operator's vision. This 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 Implementation

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

[0023] The outer layer is prepared from the following raw materials by weight: 50-90 parts low-density polyethylene and 10-50 parts linear medium-density polyethylene.

[0024] The middle layer is made from low-density polyethylene.

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

[0026] The outer layer is prepared from 50 to 90 parts by weight, specifically 60, 70, or 80 parts of low-density polyethylene. 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 / cm³. 3 More preferably, it is 0.924–0.925 g / cm³. 3 In a specific embodiment of the present invention, the low-density polyethylene used in the outer layer is grade 2420H, manufactured by CNOOC Shell, with a melt index of 2 g / 10 min and a density of 0.924 g / cm³. 3 The low-density polyethylene used in the outer layer of this 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 materials for preparing the outer layer include 10 to 50 parts of linear medium-density polyethylene, specifically 20, 30, or 40 parts; the melt index of the linear medium-density polyethylene is preferably 5 to 8 g / 10 min, more preferably 6 to 7 g / 10 min, and the density is preferably 0.93 to 0.95 g / cm³. 3 More preferably, it is 0.94–0.947 g / cm³. 3 In a specific embodiment of the present invention, the linear medium-density polyethylene is grade 81841.27, manufactured by Dow Chemical, with a melt index of 6 g / 10 min and a density of 0.947 g / cm³. 3 The linear medium-density polyethylene used in this invention has the characteristics of high composite strength and good die-cutting properties.

[0028] In this invention, the raw material for preparing the middle layer is low-density polyethylene. 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 / cm³. 3 More preferably, it is 0.924–0.925 g / cm³. 3In a specific embodiment of the present invention, the low-density polyethylene used in the outer layer is grade 2420H, manufactured by CNOOC Shell, with a melt index of 2 g / 10 min and a density of 0.924 g / cm³. 3 The low-density polyethylene used in the middle layer of this invention has the characteristics of high cleanliness, easy die-cutting, and easy processing.

[0029] The inner layer is prepared from 30 to 80 parts by weight, specifically 50, 60, or 70 parts of linear low-density polyethylene. 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 / cm³. 3 More preferably, it is 0.918–0.92 g / cm³. 3 In a specific embodiment of the present invention, the linear low-density polyethylene is grade 201XV, manufactured by ExxonMobil, with a melt index of 2 g / 10 min and a density of 0.918 g / cm³. 3 The high-density polyethylene used in this invention has the characteristics of low crystal point, high stiffness, and good die-cutting properties.

[0030] Based on the mass fraction of linear low-density polyethylene used in the inner layer, the raw materials for preparing the inner layer include 20 to 50 parts of high-density polyethylene, specifically 20, 25, or 30 parts; the melt index of the high-density polyethylene is preferably 5 to 8 g / 10 min, more preferably 6 to 7 g / 10 min, and the density is preferably 0.95 to 0.97 g / cm³. 3 More preferably, it is 0.96–0.964 g / cm³. 3 In a specific embodiment of the present invention, the high-density polyethylene is grade H377C, manufactured by Siam, Thailand, with a melt index of 7 g / 10 min and a density of 0.964 g / cm³. 3 It has good compatibility and good processability.

[0031] Based on the mass fraction of linear low-density polyethylene used in the inner layer, the raw materials for preparing the inner layer include 10 to 30 parts of matte masterbatch, specifically 20 or 25 parts; the melt index of the matte masterbatch is preferably 5 to 8 g / 10 min, and the density is 1.2 to 1.5 g / cm³. 3 In a specific embodiment of the present invention, the matte masterbatch is grade 101763-K, manufactured by Anpeise, with a melt index of 7 g / 10 min and a density of 1.37 g / cm³. 3 The matte masterbatch used in this invention has the characteristics of high haze, good compatibility, and easy processing.

[0032] In this invention, the total mass of the outer layer, middle layer and inner layer is calculated 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 this 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 this invention, the thickness of the protective film is preferably 40-60 μm, more preferably 50 μm.

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

[0036] In this invention, the three-layer co-extrusion preferably includes: feeding the raw materials for the preparation of the outer layer, middle layer and inner layer into the outer layer, middle layer and inner layer extruders respectively for melt plasticization, conveying the resulting adhesive liquid to the die head, extruding and blowing film to obtain a film bubble, the film bubble is cooled by air and then traction and rotated by a stabilizing ring and a herringbone pattern, the film bubble is flattened and then inspected, trimmed, destaticated and wound up to obtain the protective film.

[0037] In this invention, the outer extruder, middle extruder, and inner extruder are each equipped with five heating zones, which are sequentially designated as zones 1 to 5 according to the order in which the raw materials pass through. The preferred temperature for zone 1 of the outer extruder is 160–170°C, more preferably 165°C; the preferred temperature for zone 2 is 165–175°C, more preferably 170°C; the preferred temperature for zone 3 is 165–175°C, more preferably 170°C; the preferred temperature for zone 4 is 165–175°C, more preferably 170°C; and the preferred temperature for zone 5 is 165–175°C, more preferably 170°C. Similarly, the preferred temperature for zone 1 of the middle extruder is 150–160°C, more preferably 150°C; and the preferred temperature for zone 2 is... The temperature of zone 1 is preferably 150-160℃, more preferably 160℃; the temperature of zone 2 is preferably 170-180℃, more preferably 180℃; the temperature of zone 3 is preferably 170-180℃, more preferably 180℃; the temperature of zone 4 is preferably 170-180℃, more preferably 180℃; the temperature of zone 5 is preferably 170-180℃, more preferably 175℃; the temperature of zone 5 is preferably 170-180℃, more preferably 175℃.

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

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

[0040] In this invention, the inspection is preferably performed by using a crystal point defect detector to inspect the appearance and crystal points of the film; after the inspection is completed, the film is trimmed, then separated into individual sheets by the lower traction clamping roller and sent to an antistatic device for antistatic treatment, and then wound up by the front and rear winding devices to obtain the protective film of this invention.

[0041] This invention also provides the application of the protective film described in the above-described scheme or the protective film prepared by the preparation method described in the above-described scheme in PCB drilling cover plates. In this invention, the protective film is specifically used as a protective film for PCB drilling cover plates, which can protect the PCB drilling cover plate, fit tightly to the cover plate without air bubbles, and is not prone to stringing during drilling, thus not damaging the drill bit. Furthermore, it has a high degree of haze, so it does not obstruct the operator's vision during drilling.

[0042] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] Example 1

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

[0045] Table 1 Raw material ratios for Example 1

[0046]

[0047] The preparation method of the protective film is as follows: The raw materials of the outer layer, middle layer and inner layer are mixed in proportion by an automatic batching system and then fed into the outer layer, middle layer and inner layer extruders. The raw materials of the outer layer, middle layer and inner layer are melted and plasticized and then fed into the die head for extrusion and blown film. After being cooled by air, the film is flattened by the upper traction rotation through the stabilizing ring and herringbone pattern. After being cooled by the guide roller, the film enters the crystal point defect detector to detect the appearance and crystal points of the film. Then, the edges are cut and separated into individual sheets by the lower traction clamping roller and wound into the antistatic device and the front and rear winding devices to obtain the protective film. The temperature and pressure of the outer layer, middle layer and inner layer extruders and the temperature of the die head are shown in Table 2.

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

[0049]

[0050] Example 2

[0051] A protective film is made of three layers: an outer layer, a middle layer, and an inner layer, by co-extrusion blown film. The weight percentages of the materials in each layer are as follows: 25% for the outer layer, 50% for the middle layer, and 25% for the inner layer. The raw material usage of each layer is shown in Table 3. The thickness of the protective film is 50 μm.

[0052] Table 3 Raw material ratios for Example 2

[0053]

[0054]

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

[0056] Example 3

[0057] A protective film is made of three layers: an outer layer, a middle layer, and an inner layer, by co-extrusion blown film. The weight percentages of the materials in each layer are as follows: 25% for the outer layer, 50% for the middle layer, and 25% for the inner layer. The raw material usage of each layer is shown in Table 4. The thickness of the protective film is 50 μm.

[0058] Table 4 Raw material ratios for Example 3

[0059]

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

[0061] Comparative Example 1

[0062] A protective film for PCB drilling cover is made of three layers: outer layer, middle layer and inner layer, by co-extrusion blown film. The weight percentage of each layer is as follows: outer layer 25%, middle layer 50%, inner layer 25%. The raw material usage of each layer is shown in Table 5. The thickness of the protective film is 50μm.

[0063] Table 5 Raw material ratios for Comparative Example 1

[0064]

[0065] The preparation method is the same as in Example 1.

[0066] Comparative Example 2

[0067] A protective film for PCB drilling cover is made of three layers: outer layer, middle layer and inner layer, by co-extrusion blown film. The weight percentage of each layer is as follows: outer layer 25%, middle layer 50%, inner layer 25%. The raw material usage of each layer is shown in Table 6. The thickness of the protective film is 50μm.

[0068] Table 6 Raw material ratios for Comparative Example 2

[0069]

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

[0071] Performance testing:

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

[0073] Table 7 Performance Test Results

[0074]

[0075] According to the test results in Table 7, the protective film prepared by the present invention has suitable tensile strength and high haze, and also has good die-cutting characteristics and is not easy to fray; while the protective film prepared in Comparative Example 1 has high 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 conducted. The results showed that the protective film and the cover plate surface were tightly bonded, with no air bubbles appearing. The film did not string during drilling, was not easily damaged by the drill bit, and had high haze, so it did not produce reflection or glare. The drilling situation could be clearly observed without affecting the line of sight.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A protective film for a drill hole cover, characterized in that, It consists of an outer layer, a middle layer, and an inner layer; The outer layer is prepared by the following raw materials in parts by weight: 50-90 parts of low-density polyethylene and 10-50 parts of polyethylene with grade 81841.

27. The raw material for preparing the middle layer is low-density polyethylene; The raw materials for preparing the inner layer are, by mass parts: 30-80 parts of linear low-density polyethylene, 20-50 parts of high-density polyethylene, and 10-30 parts of matte masterbatch. The outer and middle layers use low-density polyethylene grade 2420H; the inner layer uses linear low-density polyethylene grade 201XV; the high-density polyethylene grade is H377C; and the matte masterbatch grade is 101763-K. The longitudinal tensile strength of the protective film for the borehole cover plate is 20~22.5MPa, the transverse tensile strength is 18~19.5MPa, the longitudinal elongation at break is 230~260%, the transverse elongation at break is 550~580%, and the haze is 43~48%.

2. The protective film for the borehole cover plate according to claim 1, characterized in that, The low-density polyethylene used in the outer and middle layers has a melt index of 1.5~2.5 g / 10 min and a density of 0.92~0.93 g / cm³. 3 .

3. The protective film for the borehole cover plate according to claim 1, characterized in that, The inner layer uses linear low-density polyethylene with a melt index of 1.5~2.5 g / 10min and a density of 0.915~0.925 g / cm³; the high-density polyethylene has a melt index of 5~8 g / 10min and a density of 0.95~0.97 g / cm³; the matte masterbatch has a melt index of 5~8 g / 10min and a density of 1.2~1.5 g / cm³. 3 .

4. A method for preparing the protective film for the borehole cover plate according to any one of claims 1 to 3, comprising the following steps: The raw materials for the outer, middle, and inner layers are co-extruded in three layers to obtain the protective film for the drilled cover plate.

5. The preparation method according to claim 4, characterized in that, The three-layer co-extrusion includes: [the following steps are mentioned:] [The text abruptly ends here, likely due to an incomplete sentence or a missing section.] The raw materials for the preparation of the outer, middle, and inner layers are respectively fed into the outer, middle, and inner layer extruders for melt plasticization. The obtained adhesive liquid is conveyed to the die head, and the extruded film is blown to obtain a film bubble. After the film bubble is cooled by air, it is traction-rotated by a stabilizing ring and a herringbone pattern. The film bubble is flattened and then inspected, trimmed, destaticated and wound up to obtain the protective film for the drilled cover plate.

6. The preparation method according to claim 5, characterized in that, The outer layer extruder, the middle layer extruder Both the outer and inner extruders are equipped with five heating zones, numbered 1 to 5 according to the order in which the raw materials pass through. The outer extruder has zones 1-5 with temperatures ranging from 160-170°C, 165-175°C, 165-175°C, 165-175°C, and 165-175°C respectively. The middle extruder has zones 1-50-160°C with temperatures ranging from 150-160°C, 150-160°C, and 150-160°C respectively. Zone 1 temperature is 150~160℃, and Zone 5 temperature is 150~160℃; the temperature of Zone 1 of the inner extruder is... 165~175℃, Zone 2 temperature is 170~180℃, Zone 3 temperature is 170~180℃, Zone 4 temperature is 170~180℃, Zone 5 temperature is 170~180℃; The die head is equipped with four heating zones, which are numbered 1 to 4 according to the order in which the raw materials pass through. The temperature of zone 1 is 170-180℃, zone 2 is 170-180℃, zone 3 is 170-180℃, and zone 4 is 170-180℃.

7. The application of the drill cover plate protective film according to any one of claims 1 to 3 or the drill cover plate protective film prepared by the preparation method according to any one of claims 4 to 6 in PCB drill cover plates.

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