JP3052662U - Printed circuit board cover lay film pressing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cushioning material which is easily deformed into a concave shape so as to completely conform to a convex shape of a substrate, and which allows a coverlay film to be completely adhered to an outer surface of the convex portion on the substrate. I do. SOLUTION: The thick film 1 is composed of a quadrilateral laminated sheet having a structure in which heat-resistant thin films 2 and 3 are respectively laminated in an unbonded state on the upper surface and the lower surface of a low-temperature hot-melt thick film 1. A sheet for pressing a printed wiring board cover lay film, wherein the thin films 2 and 3 are bonded to each other at an arbitrary position within a region 3 cm inside one side of the thick film 1.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a sheet for pressing a printed circuit board coverlay film. The term “sheet for pressing a printed circuit board coverlay film” as used in the present specification refers to a method in which a plastic film (coverlay film) having an adhesive surface is laminated on one or both sides of a printed circuit board, and a heat roller or a hot plate is used. It means a sheet member that is applied by being interposed between the heat roller or hot plate and the coverlay film during thermocompression bonding.

[0002]

[Prior art]

 Conventionally, when laminating and bonding a coverlay film on a printed circuit board using a heat roller or hot plate, a sheet-like cushion material is interposed between the heat roller or hot plate and the coverlay film, and the cushion material is used. The thermocompression bonding of a coverlay film to a substrate via a substrate is widely performed. Paper and silicone rubber sheets are known as this cushion material. When the cover lay film is laminated and adhered to the printed board, the cushioning material is deformed into a concave shape corresponding to the copper layer convex part on the board by the pressing force of the heat roller or hot plate, and the cover lay film is It has the effect of adhering to the entire surface of the convex portion of the copper layer.

Meanwhile, the above-mentioned cushioning material generally used conventionally has a drawback that it is difficult to completely adhere the coverlay film to the surface of the convex portion because the cushioning-like (elastic) deformation is utilized. In addition, the application thereof requires a work of sandwiching the cushioning material between two separately prepared thin heat-resistant films, which is very troublesome in terms of work. Various types of cushioning materials have been proposed so far in order to improve work efficiency and improve the adhesion between the substrate and the coverlay film. As such a material, for example, a thin heat-resistant film laminated and bonded to both surfaces of a low-temperature hot-melt thick film (Japanese Patent Application Laid-Open Nos. 1-276694 and 2-310990, actual JP-A-4-89340 and JP-A-62-45133 are known. Since such a cushioning material has a structure in which a thin film is entirely laminated and adhered to both sides of a thick film, the cushioning material is interposed between a coverlay film on a substrate and a heat roller or a heat plate. When pressed by a heat roller or heat and pressure to deform into a concave shape corresponding to the copper layer protrusion on the substrate, the thin film that constitutes the lower surface of the cushion material is fixed and cannot move. Even when the film is melted by heat, a strong tensile stress is generated in the thin film laminated on the lower surface. Since this strong tensile stress acts as a force opposing the deformation of the cushion material, it becomes extremely difficult to deform the cushion material into a concave shape so as to completely match the convex shape on the substrate. As a result, the cover lay film cannot be completely adhered to the outer surface of the convex portion of the substrate, so that a fine gap is formed between the cover lay film and the outer surface of the convex portion, and air enters the fine gap. Inconveniences such as generation of air bubbles occur.

[0004]

[Problems to be solved by the invention]

 It is an object of the present invention to provide a cushioning material that can be easily deformed into a concave shape so as to completely match the convex shape of the substrate, and can easily make the cover lay film completely adhere to the outer surface of the convex portion on the substrate. I do.

[0005]

[Means for Solving the Problems]

 The present inventors have conducted various studies to solve the above problems, and as a result, completed the present invention. That is, according to the present invention, the heat-resistant thin film 1 is composed of a quadrilateral laminated sheet having a structure in which heat-resistant thin films 2 and 3 are laminated in a non-adhered state on the upper surface and the lower surface thereof, respectively. The thick film 1 and the thin films 2 and 3 are connected to each other at an arbitrary position within a region 3 cm inside one side of the thick film 1. Sheet is provided. Further, according to the present invention, a heat-resistant thin film 2 is laminated on an upper surface of a low-temperature heat-meltable thick film 1 in an adhesive state, and a heat-resistant thin film 3 is unbonded on a lower surface of the thick film. The thick film 1 and the thin film 3 in the non-adhered state are formed of a quadrilateral laminated sheet having a laminated structure, and the thick film 1 and the non-adhesive thin film 3 are bonded to each other at an arbitrary position within a region 3 cm inside one side of the thick film 1. A sheet for pressing a printed wiring board cover lay film is provided.

[0006]

[Embodiment of the invention]

 Next, the present invention will be described with reference to the accompanying drawings. FIG. 1 is an explanatory cross-sectional view of an example of a sheet for pressing a printed circuit board coverlay film (hereinafter simply referred to as a sheet) of the present invention, and FIG. 2 is a plan view thereof. In these figures, 1 is a low-temperature hot-melt thick film, 2 and 3 are heat-resistant thin films, and 4 is a stop pin. A indicates the entire sheet. The sheet A of the present invention shown in FIGS. 1 and 2 is formed of a quadrangular laminate in which thin films 2 and 3 are entirely laminated in a non-adhered state on both sides of a thick film 1, and one side thereof The thick film 1, the thin film 2, and the thin film 3 are connected and fixed at the corresponding end of the laminate sheet by the stopper 4. The low-temperature hot-melt thick film 1 has a softness at a low temperature within a range in which the adhesive coated on the coverlay film exhibits adhesiveness, for example, 50 ° C. or more, preferably 80 ° C. to 120 ° C. Any resin film that exhibits fusibility can be used. As such a material, an olefin-based polymer film such as a film made of a polyethylene or a polyethylene-based copolymer or a low-temperature softening polypropylene film is preferable. The thickness of this film is usually at least 80 μm, preferably in the range of 100 to 200 μm. The heat-resistant thin films 2 and 3 laminated on both sides of the thick film 1 may be formed of a material that can withstand a higher temperature than the thick film 1. For this purpose, heat-resistant resin films, such as stretched polypropylene films, heat-resistant polyolefin films, polyester films, polyamide films, polyimide films, polytetrafluoroethylene films, polyvinyl fluoride films, fluorinated ethylene / propylene films A film or the like can be used, and a metal film such as an aluminum foil can be used. Among them, a heat-resistant polyolefin film is particularly preferable. Among them, poly-4-methylpentene-1, polychlorotrifluoroethylene, polytetrafluoroethylene, poly-3-methylbutene-1, poly-3-phenylbutene-1 and the like are preferable. Films obtained from the above polymers are preferred. The thickness of the heat-resistant film is thin, for example, 9 to 60 μm, preferably 12 to 30 μm, from the viewpoints of heat conductivity, adhesion between the coverlay film and the substrate, influence on circuits, and the like. is there. Preferable examples of the laminated sheet composed of the thick film 1 and the thin films 2 and 3 in the present invention are as follows. A laminated sheet in which a polytetrafluoroethylene film is laminated can be shown.

[0007] In the quadrilateral laminated sheet of the present invention, the sheet portion to which each film constituting the laminated sheet is bonded is 3 cm inside, preferably 2.5 cm inside from one side of the thick film 1. , More preferably a region 2 cm inside. That is, in FIG. 2, the films are bonded to each other at an arbitrary position in a region indicated by oblique lines within a distance of 1.5 cm from a side a on a perpendicular to the vertical line. In this case, the bonding of the films can be performed over the entire area, or can be performed at one or more points in the area. As a bonding method for fixing the respective films, any conventionally known method, for example, a method using a heat fusion method, a bonding method using an adhesive, a method using a stopper such as a stop needle, a stopper, a stop thread, or the like is used. And a method of bending each film or providing a cut portion to mutually stop each other. In the present invention, a method using a stop needle is particularly preferable, and the film can be easily fixed and fixed by this method. In this case, in the method using a stopper such as a stop needle, the place to be stopped (fixed place) is 1 to 3, preferably 1 or 2 places. In the laminate sheet in which the films are bonded and fixed as described above, most of the thin films 2 and 3 are not fixed, and the thin films 2 and 3 are independent of each other. Therefore, even if the sheet is subjected to deformation such as bending or dents, no substantial tensile stress is generated in the thin film 3 on the lower surface, and no stress against the deformation is generated. Therefore, such a sheet of the present invention is interposed between the coverlay film on the substrate and the heat roller or the hot plate, and pressed by the heat roller or the hot plate to soften or melt the thick film 1. In this case, the coverlay film can be deformed into an accurate concave shape corresponding to the convex shape on the substrate, and as a result, the coverlay film can be completely adhered to the outer surface of the convex portion of the substrate. No bubbles are generated between the ray film and the substrate. In conventional cushioning materials in which a thin film is entirely laminated and adhered to both sides of a thick film, if the lower surface is deformed by dents or the like, the peripheral edge of the film on the lower surface is bonded and fixed. In addition, a large tensile stress is generated in the lower film, which hinders deformation, but the sheet of the present invention does not cause any such inconvenience.

In another example of the present invention, the thin film 2 to be laminated on the upper surface of the thick film 1 may be in a state of being completely or partially adhered to the upper surface of the thick film in advance. Of course, also in this case, the thin film 3 on the lower surface holds the whole or most of the thin film 1 in a non-adhered state with respect to the thick film 1. As long as the thin film 3 is bonded only at the end of one side, when the lower surface of the laminated sheet is deformed through the thin film 3, the thin film 3 on the lower surface is formed. Can be easily and accurately deformed because there is substantially no tensile stress that hinders its deformation.

FIG. 3 is an explanatory view of a cross-sectional state when a coverlay film is heated and pressed on a printed 9 substrate via the sheet of the present invention. In FIG. 3, reference numeral 5 denotes a printed circuit board, 6 denotes a copper layer exposed on the substrate in a convex shape, and 7 denotes a coverlay film. A shows the sheet of the present invention. As can be seen from FIG. 3, the sheet of the present invention is a plastic film whose thick film 1 is easily deformed by heating. On the other hand, since the thin film 3 on the lower surface is only fixed at the left end in the drawing, even if the thin film 3 on the lower surface is concavely deformed, 3 moves slightly to the left, and no substantial tensile stress occurs in the thin film 3. Therefore, the sheet A of the present invention is deformed into a concave shape corresponding to the convex copper layer pattern exposed on the printed circuit board, as shown in the drawing. As a result, the cover lay film 7 is thermocompression-bonded with high precision onto the printed circuit board 6 via the sheet A of the present invention.

[0010] In order to cover the coverlay film on the printed circuit board surface using the sheet of the present invention, the coverlay film and the sheet of the present invention are successively stacked on the printed circuit board surface, and then a heat roller or a hot plate is used thereon. Press. Thus, the state shown in FIG. 3 is formed, and the cover lay film is adhesively coated on the substrate surface. Next, the sheet A is peeled off except for the pressing force to obtain a product in which the cover surface is tightly covered with the substrate surface.

As can be seen from FIG. 3, the sheet of the present invention is pressed by a hot roller or a hot plate, and when a concave portion corresponding to the convex shape of the copper layer of the substrate is formed on the surface thereof, the sheet is softened. The melted thick film 1 moves in the peripheral direction by the reduced volume and is extruded from between the thin films 2 and 3 to the outside. The effluent extruded to the outside causes problems such as adhesion on the substrate. Such a problem can be solved by forming a blank portion where the thick film 1 does not exist in the peripheral portion of the sheet. FIG. 4 shows a plan view of such a sheet. FIG. 4 is a plan view of a quadrilateral laminate sheet. In this figure, reference numeral 1 denotes a thick film, 2 denotes a thin film, and 8 denotes a margin portion formed on the periphery thereof where the thick film 2 does not exist. Such a sheet is suitable for use when the entire surface of the sheet is pressed by a hot plate or the like.

[0012]

[Effect of the invention]

 The printed circuit board cover lay film pressing sheet of the present invention protects the metal layer such as the copper layer exposed on the printed circuit board surface, and furthermore, covers the substrate surface with the cover lay film to improve the mechanical strength of the substrate. At this time, like the conventional cushioning material, it is used by overlapping it on the coverlay film. In this case, the printed circuit board is not particularly limited, and one having a copper layer on one side and one having a copper layer on both sides is arbitrarily used. The printed board may be a solid board in addition to the flexible board. The printed circuit board cover lay film pressing sheet of the present invention is accurately deformed into a concave shape corresponding to the convex pattern of the copper layer on the substrate surface. Therefore, when the sheet of the present invention is used, the coverlay film can be laminated and adhered to the surface of the convex portion with high accuracy corresponding to the convex shape of the copper layer on the substrate surface. In addition, the sheet for pressing the printed circuit board coverlay film of the present invention is different from the conventional case in which a separately prepared cushioning material and a heat-resistant film are laminated and used in actual use. Therefore, the troublesome lamination work is not required, and the workability is extremely excellent.

[0013]

【Example】

 Next, the present invention will be described with reference to examples.

Example 1 A heat-resistant thick film 1 was a 100 μm thick, 500 × 500 mm polyethylene resin film, and poly-methylpentene-1 having a thickness of 30 μm and a size of 500 × 500 mm was formed on both sides thereof. A resin thin film is laminated in a non-adhered state, and the laminated sheet is joined with a stop needle (a device for stopping: MAX-10, HD-10, a fastener: MAX-10, Max No. 10-1M). It was fixed and cushion material was created. In this case, the fixing point by the stop needle was one corner of the laminated sheet as shown in FIG.

Use Example 1 Using the cushion material obtained in Example 1, a coverlay film was laminated on a flexible print substrate having through holes. Lamination is performed by laminating a substrate, a coverlay film that has been pre-drilled at positions corresponding to through holes in the substrate, and cushioning material in this order, heating and pressing with a hot plate, and laminating and bonding the coverlay film to the substrate surface. I let it. In this case, the coverlay film is completely adhered to the convex shape of the copper layer on the substrate surface, no bubbles are seen between the substrate and the coverlay film, and during the next step of soldering, The bubbles did not expand due to the high temperature, and the coverlay film did not peel off and did not affect the pattern of the copper layer. In addition, there is no deviation between the position of the through-hole on the board and the position of the through-hole on the coverlay film, so that the components to be mounted can be accurately mounted. Can be protected. Furthermore, because they are completely adhered, clear patterns can be reproduced and fine patterns can be reproduced.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of an example of a printed circuit board cover lay film pressing sheet of the present invention.

FIG. 2 is a plan view of the sheet shown in FIG.

FIG. 3 is an explanatory cross-sectional view showing a state in which the coverlay film is heat-pressed to the substrate surface via the printed circuit board coverlay film pressing sheet of the present invention.

FIG. 4 is a plan view of another example of the sheet for pressing a printed circuit board coverlay film of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Thick film 2, 3 Thin film 4 Stopper 5 Printed circuit board 6 Copper layer 7 Cover lay film 8 Margin A A sheet (cushion material) for pressing printed circuit board cover lay film of the present invention

Claims (6)

[Utility model registration claims] 1. A quadrangular laminated sheet having a structure in which heat-resistant thin films 2 and 3 are laminated on the upper and lower surfaces of a low-temperature hot-melt thick film 1 in a non-adhered state, respectively. And the thin films 2 and 3 are bonded to each other at an arbitrary position in a region 3 cm inside from one side of the thick film 1. 2. The thick film 1 is made of a polyethylene resin and has a thickness of 80 to 200 μm.
4. The sheet for pressing a printed circuit board coverlay film according to item 1. 3. The sheet according to claim 1, wherein the thin films 2 and 3 are made of poly-4-methylpentene-1 and have a thickness of 9 to 60 μm. 4. The printed circuit board cover lay film pressing sheet according to claim 1, wherein said thick film 1 and said thin films 2 and 3 are joined at one place. 5. The printed circuit board cover lay film pressing sheet according to claim 1, wherein said thick film 1 and said thin films 2 and 3 are joined by a stop pin. 6. A structure in which a heat-resistant thin film 2 is laminated on an upper surface of a low-temperature heat-meltable thick film 1 in an adhesive state, and a heat-resistant thin film 3 is laminated on a lower surface of the thick film in a non-adhesive state. Consisting of a quadrilateral laminate sheet of
The thick film 1 and the non-adhesive thin film 3 are bonded to each other at an arbitrary position in a region 3 cm inside one side of the thick film 1. Pressing sheet.