KR20100035887A - Ground form gasket for surface mount device and method for manufacturing it - Google Patents

Abstract

PURPOSE: A ground form gasket for the electronic circuit board surface mounting device and manufacturing method thereof minimizes the elasticity degradation according to high-compression or the compression fault by getting over the limit of the compression height of the form gasket. CONSTITUTION: A gasket(10) comprises the poly vinyl alcohol form(12), and the inside cushion material(16) and electric conduction metal coating matrix(20). An inside cushion material comprises the silicon film coated in the surface of the cell accomplishing the poly vinyl alcohol form. The electric conduction metal coating matrix is attached to the outer side surface of the inside cushion material. The heat resistant adhesive for sticking to the electric conduction metal coating matrix is spread between the inside cushion material and electric conduction metal coating matrix.

Description

Ground Form Gasket for Surface Mount Device and Method for manufacturing it

The present invention relates to foam gaskets for ground. More particularly, the present invention relates to a ground form gasket for surface mount of an electronic circuit board.

In general, surface mount device (SMD) electrical contact gaskets are for conducting electricity with devices surface-mounted on an electronic circuit board.

To this end, the gasket should be excellent in electrical conductivity, there should be no change in physical properties due to high heat of 260 degrees to 290 degrees in the reflow equipment, and very demanding conditions such as easy soldering are required.

Conventionally, a solderable spring material such as a beryllium copper foil, a stainless foil, or a copper foil is pressed and used as a contact terminal for grounding an electronic circuit board. This structure has a disadvantage in that an expensive mold ratio is required in manufacturing and elasticity is lowered when a pressure higher than the yield strength is applied.

In the case of the foam gasket structure, a silicone foam or a silicone tube is used as the internal elastic body, and the external conductive material has a structure in which a metal is vacuum-deposited on a polyimide film.

However, the above structure has a problem that the internal elastic material is made of pure silicon in the form of a tube or foamed, so that the ratio of the internal elastic solid content is high, the compression is not 40 to 50% or less. In addition, since the silicon itself is expensive compared to other resins, there is a disadvantage that the raw material cost increases.

As mentioned, foam gaskets for surface mounting of electronic circuit boards require heat resistance and elasticity for internal elastomers. Internal elastic bodies that satisfy these conditions are limited to silicon. However, in the case of silicon, a foam structure in which thermal expansion is minimized at a high temperature in a reflow device is in an open cell form, but it is practically difficult to foam in an open cell form. When using a sponge in the form of a close cell, bubbles inside the cell are expanded and deformed at a high temperature inside the reflow, and thus the positional deviation and twisting due to hot air cannot be prevented.

In addition, the conventional foam gasket type electrical contact terminal generates a repulsive force due to the cohesive force and the buoyancy of the solder when soldering to the electronic circuit board frequently occurs from the position due to the hot air in the reflow.

Accordingly, the present invention provides a ground foam gasket for mounting a surface of an electronic circuit board and minimizing volume expansion and deformation due to high heat during reflow.

In addition, the present invention provides a ground foam gasket for mounting a surface of an electronic circuit board and minimizing compression failure due to high compression.

The present invention also provides a ground form gasket for surface mounting of an electronic circuit board, and a method of manufacturing the same.

In addition, the present invention provides a ground foam gasket for mounting a surface of an electronic circuit board and a method of manufacturing the same, which are capable of minimizing the occurrence of defects by not leaving the home position even in the hot air of the reflow equipment.

To this end, the gasket may include an inner cushioning agent including a foamed resin foam and a silicon film coated on a cell surface constituting the foamed resin foam, and a conductive metal thin film attached to an outer surface of the inner cushioning agent.

A heat resistant adhesive may be further applied between the inner cushioning agent and the conductive metal thin film.

Here, the foamed resin foam may have a structure in which at least one resin selected from polyurethane, NBR rubber, and CR rubber EPDM rubber is foamed in an open cell form.

In addition, the internal cushioning agent may have a structure in which metal powder is further added.

In addition, the heat resistant adhesive may be further added to the metal powder.

The gasket may have a structure in which a groove recessed inward is formed on a surface attached to the electronic circuit board.

The groove may be formed in a shape corresponding to the cross-sectional shape of the cream solder is applied to the electronic printed circuit board and melted between the gasket. The cream solder applied to the electronic printed circuit board may be applied at intervals of 1 to 2 mm with a width of 2 to 4 mm along the length of the gasket.

On the other hand, the gasket manufacturing method foaming the resin to prepare a foamed resin foam, impregnating the foamed resin foam in a silicone resin solution, removing the excess silicone resin infiltrated into the foamed resin foam, the silicone resin is coated It may comprise the step of preparing an inner cushioning agent comprising the step of curing the foamed foam foam, the high temperature aging of the foamed resin foam, and attaching a conductive metal thin film to the outer surface of the inner cushioning agent.

The foamed resin foam may have a structure in which at least one resin selected from polyurethane, NBR rubber, and CR rubber EPDM rubber is foamed in an open cell form.

In addition, the manufacturing method may include mixing the metal powder dispersed in the silicone resin solution with a diluent before impregnating the foamed resin foam in the silicone resin solution.

The curing step may be a structure that passes through a hot air tunnel of 150 ℃ ~ 180 ℃ for 3-5 minutes.

The high temperature aging step may be performed for 1 hour in a curing furnace of 120 ℃ ~ 170 ℃.

The conductive metal thin film attaching step may include applying a heat-resistant adhesive to the conductive metal thin film, attaching the conductive metal thin film to the inner cushioning agent through a mold, and applying a thermal mold and a cooling mold to the inner cushioning agent to which the conductive metal thin film is attached. Forming through, it may include the step of hot aging the molded gasket.

In addition, the manufacturing method may further comprise the step of forming a groove recessed inward on the mounting surface of the gasket during the molding process through the hot mold.

The heat resistant adhesive may have a structure in which a metal powder is mixed.

The heat resistant adhesive may be applied to 0.1 ~ 0.5mm.

The hot mold in the molding step may be set to 150 ~ 200 ℃.

The aging step may be made for 30 minutes to 2 hours in a curing furnace of 150 ~ 200 ℃.

According to the ground form gasket for surface mounting of the electronic circuit board, the merits of the urethane foam of the open cell form and the advantage of the silicone resin can be minimized to minimize melting or volume expansion and deformation due to high heat during reflow.

In addition, by overcoming the limitation of the compression height of the foam gasket and increasing the flexibility, it is possible to minimize the deterioration of elasticity or poor compression due to high compression.

In addition, the gasket can be manufactured with urethane, etc., rather than expensive silicone, thereby lowering the manufacturing cost and increasing price competitiveness.

In addition, by improving the structure of the gasket and increasing its specific gravity, it is possible to minimize the occurrence of defects by not leaving the position in the hot air in the reflow equipment.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

The drawings are schematic and illustrate that they are not drawn to scale. The relative dimensions and ratios of the parts in the figures have been exaggerated or reduced in size for clarity and convenience in the figures and any dimensions are merely exemplary and not limiting. And the same structure, element or part that appears in more than one figure the same reference numerals are used in different embodiments to indicate corresponding or similar features.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” include plural forms as well, unless the phrases clearly indicate the opposite. As used herein, the term "comprising" embodies a particular characteristic, region, integer, step, operation, element, and / or component, and other specific characteristics, region, integer, step, operation, element, component, and / or group. It does not exclude the presence or addition of.

Unless defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Commonly defined terms used are additionally interpreted to have a meaning consistent with the related technical literature and the presently disclosed contents, and are not interpreted in an ideal or very formal sense unless defined.

Embodiments of the invention described with reference to a perspective view specifically illustrate an ideal embodiment of the invention. As a result, various variations of the illustration, for example variations in the manufacturing method and / or specification, are expected. Thus, the embodiment is not limited to any particular form of the depicted area, but includes modifications of the form, for example, by manufacture. For example, the regions shown or described as being flat may have characteristics that are generally coarse / rough and nonlinear. Also, the portion shown as having a sharp angle may be rounded. Thus, the regions shown in the figures are merely approximate, and their shapes are not intended to depict the exact shape of the regions, nor are they intended to limit the scope of the present invention.

1 is a schematic perspective view of a ground form gasket for an electronic circuit board surface mount according to the present embodiment.

The gasket 10 according to the present embodiment includes a foamed resin foam 12 and a silicon film 14 penetrated by the foamed resin foam 12 and coated on the surface of the cell C forming the foamed resin foam. A cushioning agent 16 and a conductive metal thin film 20 attached to the outer surface of the inner cushioning agent 16 are included.

A heat resistant adhesive 18 for adhering the metal thin film 20 is further applied between the inner cushioning agent 16 and the conductive metal thin film 20. The heat resistant adhesive 18 is a thermosetting silicone adhesive.

The metal thin film 20 forms an outer shell of the gasket 10 and is made of a material having excellent conductivity and solderability. The metal thin film 20 may be made of a nickel metal, a pure metal such as copper or an alloy of nickel and copper, an alloy of nickel and iron, an alloy of nickel and tin, or a plated tin of the pure metal or alloy described above. The metal thin film 20 is formed to a thickness of 5㎛ ~ 12㎛. When the thickness of the metal thin film 20 is 5 μm or less, the handling is not easy. When the thickness of the metal thin film 20 is larger than 12 μm, the gasket has a low flexibility, and thus the function as a side part is degraded.

In addition, the metal thin film 20 may be a flexible copper clad laminate (FCCL) film plated with copper tin, etc. after the vacuum deposition of metal on the polyimide film.

The inner cushion 16 acts as an inner elastic body. In the present embodiment, the foamed resin foam 12 of the inner cushioning agent 16 is foamed in the form of an open cell and has a structure having a plurality of cells C communicating with each other. The foamed resin foam is a sponge structure made of a polymer resin such as polyurethane, NBR rubber, CR rubber and EPDM rubber. The foamed resin foam 12 is not particularly limited as long as it is a sponge structure foamed in an open cell form.

The silicon film 14 is coated on the surface of the cell C of the foamed resin foam 12 to compensate for the heat resistance and elasticity of the foamed resin foam 12 having an open cell structure.

In the present exemplary embodiment, the inner cushion 16 or the heat resistant adhesive 18 may further include a metal powder 19 to increase specific gravity. This is to increase the specific gravity of the gasket to prevent the gasket from being released in position by the hot air in the reflow equipment.

The metal powder 19 has high specific gravity and good electrical conductivity, such as copper, silver, stainless steel, and the like. The particle size of the metal powder 19 is 6 ~ 10㎛. When the particle size of the metal powder is out of the above range, a hard problem occurs in dispersion and property management.

2 and 3 show another embodiment of the present gasket 11.

As shown in the drawing, the gasket 11 has a structure in which a groove 30 recessed inward is formed on a surface attached to the electronic circuit board.

The groove 30 has a shape corresponding to a naturally spreading cross-sectional shape of the cream solder 50 applied to the electronic printed circuit board P and melted between the gaskets 11. That is, the groove 30 is formed in a cross-sectional structure of an arch shape in which the top is flat and the side is curved in an arc shape. The height of the groove 30 corresponds to the application height of the cream solder 50 applied on the electronic printed circuit board (P). Since the application height of the cream solder 50 is approximately 0.13 mm to 0.15 mm, the height of the groove 30 may also correspond to or be increased by 0.1 mm to 0.2 mm.

As shown in FIG. 4, the cream solder 50 coated on the electronic printed circuit board P is applied at a distance of 1 to 2 mm with a width of 2 to 4 mm along a length direction of the gasket. do. When the thickness and the coating interval of the cream solder 50 deviates from the above conditions, a soldering defect such as positional deviation occurs. The gap D serves as a preliminary space in which flux components may be discharged when the cream solder is melted. When soldering the flux component contained in the cream solder boils out and flows into the space. In this case, the gasket 11 can be prevented from being displaced from the fixed position of the printed circuit board P by the force of the boiled flux during soldering.

On the other hand, this gasket manufacturing method is as follows.

As shown in FIG. 5, the gasket manufacturing method includes preparing a foamed resin foam by foaming a resin (S100), and impregnating the foamed resin foam in a silicone resin solution to coat a silicone resin on a cell surface of the foamed resin foam. Step (S110), the step of removing the silicone resin overcoated in the foamed resin foam (S120), the step of curing the silicone resin coated foamed resin foam (S130), the high temperature aging of the silicone resin coated foamed resin foam Step (S140), and the step of attaching the conductive metal thin film 20 to the outer surface of the silicone resin coated foam resin foam.

The foamed resin foam 12 is produced by foaming a polymer resin such as polyurethane, NBR rubber, CR rubber EPDM rubber in an open cell form.

As described above, the silicon film 14 is coated on the surface of the cell C of the foamed resin foam 12 to compensate for the heat resistance and elasticity of the foamed resin foam 12 having an open cell structure.

In the impregnation step of the foamed resin foam 12, the silicone resin solution is adjusted to the viscosity during coating using a diluent which is an organic emulsion such as toluene. The mixing ratio of the silicone resin and the diluent of the silicone resin solution is 1: 1 to 1: 2.

In addition, the silicon resin solution is further mixed with the metal powder (19). The metal powder 19 has high specific gravity and good electrical conductivity, such as copper, silver, stainless steel, and the like. The particle size of the metal powder 19 is 6 ~ 10㎛. When the particle size of the metal powder 19 is out of the above range, a hard problem occurs in dispersion and property management. Therefore, by increasing the specific gravity of the gasket, it is possible to prevent the gasket from being released from the position due to the hot air in the reflow equipment.

The metal powder 19 is dispersed in a diluent and evenly dispersed by adding the dispersed solution to a silicone resin, and the viscosity is adjusted with a diluent.

The foamed resin foam 12 is impregnated in the silicone resin solution to which the metal powder 19 prepared as described above is added and then taken out. The silicone resin is coated on all the cells C inside and outside the foamed resin foam foamed in the form of an open cell to form a silicon film 14. The expanded foamed resin foam 12 is passed between rollers maintaining a constant gap to remove the overcoated silicone resin. The silicone resin-coated foamed resin foam 12 passes through a hot air tunnel at 150 ° C. to 180 ° C. for 3 to 5 minutes to volatilize the diluent and perform primary curing treatment. (S110 to S130)

The silicon film coating process is performed continuously, in the present embodiment, a thermosetting silicone resin is described as an example, but a water-reactive (RTV type) silicone resin is also applicable.

The first high temperature curing silicone foam coating foam resin foam 12 is aged for 1 hour in a curing furnace of 120 ℃ ~ 170 ℃. In this case, when a moisture-reactive (RTV type) silicone resin is used, it is aged for complete curing according to the curing conditions of the resin.

The manufacturing method is a silicone resin coated on the surface of all the cells (C) to melt at a high temperature, which is a disadvantage of the open cell-type foamed resin foam 12 by manufacturing the inner cushioning agent 16 through the above process. Will protect. In addition, by implementing the open cell structure that cannot be manufactured with a silicone resin using a resin foam 12 such as urethane as a support, mutual defects can be compensated for. In addition, since the metal powder 19 is added to obtain an appropriate specific gravity, it is possible to satisfy all the conditions required as the internal elastic body of the SMD foam gasket. In addition, since the main material of the inner cushioning agent 16 uses the foamed resin foam 12 such as urethane, which is inexpensive compared to silicon, it is possible to reduce the raw material cost by reducing the amount of expensive silicone resin.

Here, the attaching of the conductive metal thin film 20 may include applying the heat resistant adhesive 18 to the conductive metal thin film 20 (S150), and attaching the conductive metal thin film 20 to the inner cushioning agent 16 through a mold. Step (S160), the step of forming the inner cushioning agent 16 attached to the conductive metal thin film 20 through a hot mold and a cooling mold (S170), and the step of hot aging the molded gasket (S190). have.

In the present embodiment, the heat resistant adhesive 18 is a thermosetting silicone adhesive. The heat resistant adhesive 18 is applied to the metal thin film 20 slitting to a predetermined width by using an adhesive coating device in a 0.1 ~ 0.5mm. (S150)

The metal thin film 20 to which the heat resistant adhesive 18 is applied is wrapped around the outer surface of the foamed resin foam 12 having the open cell shape while passing through the guide mold.

Thus, the foamed resin foam 12 is wrapped around the metal thin film 20, and passes through a hot mold of 150 ℃ to 200 ℃, and passes through the cooling mold, the primary molding and bonding is completed (S170).

Forming and bonding gasket is cut to a certain length and then aged in a curing furnace of 150 ℃ ~ 200 ℃ 30 minutes ~ 2 hours to complete the bonding and molding is complete (S190) the process as described above is completed continuously The gasket is then cut to the desired length to complete the manufacture.

On the other hand, the manufacturing method further includes the step of forming a groove 30 recessed inward on the mounting surface of the gasket during the molding process through the hot mold (S180).

The groove 30 has a shape corresponding to a naturally spreading cross-sectional shape of the cream solder 50 applied to the electronic printed circuit board P and melted between the gaskets 11. That is, the groove 30 is formed in a cross-sectional structure of an arch shape in which the top is flat and the side is curved in an arc shape. The height of the groove 30 corresponds to the application height of the cream solder applied on the electronic printed circuit board. Since the application height of the cream solder 50 is approximately 0.13 mm to 0.15 mm, the height of the groove 30 also corresponds to this or is formed to be 0.1 mm to 0.2 mm higher.

By forming the groove 30 in the gasket as described above, the cream solder melted between the gasket and the printed circuit board stays only in the internal space of the groove 30, thereby preventing the flow of the cream solder. In addition, in the case of a conventional gasket having a flat mounting surface, the cohesion and buoyancy of the melted cream solder act as repulsive forces. However, the grooved gasket has a surface affinity to act as an attraction force. It is possible to prevent the gasket from being released from the position due to the hot air in the.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

1 is a schematic diagram of a ground form gasket for surface mounting of an electronic circuit board according to an embodiment.

2 is a schematic diagram of a ground form gasket for an electronic circuit board surface mount according to another embodiment.

3 and 4 are schematic views illustrating a mounting structure of a foam gasket according to the embodiment of FIG. 2.

FIG. 5 is a schematic flowchart illustrating a manufacturing process of a ground form gasket for mounting an electronic circuit board surface according to the present embodiment.

Explanation of symbols on the main parts of the drawings

10,11 gasket 12 foaming resin foam

14 silicon film 16 inner cushion

18: heat resistant adhesive 19: metal powder

20: thin metal film 30: groove

50: cream solder

Claims (15)

Preparing a foamed resin foam by foaming a resin; impregnating the foamed resin foam with a silicone resin solution; removing excess silicone resin impregnated into the foamed resin foam; and curing the foamed resin foam coated with a silicone resin. Preparing an internal cushioning agent, the method comprising the steps of: aging the silicone resin at a high temperature; Attaching a conductive metal thin film to an outer surface of the inner cushion Method for manufacturing a ground foam gasket for mounting the surface of an electronic circuit board comprising a. The method of claim 1, The foamed resin foam is a method for manufacturing a ground foam gasket for mounting a surface of an electronic circuit board in which at least one resin selected from polyurethane, NBR rubber and CR rubber EPDM rubber is foamed in an open cell form. The method of claim 2, A method of manufacturing a ground form gasket for an electronic circuit board surface mounting method further comprising mixing a metal powder dispersed in a silicone resin solution with a diluent before impregnating the foamed resin foam in the silicone resin solution. 4. The method according to any one of claims 1 to 3, The attaching of the conductive metal thin film may include applying a heat resistant adhesive to the conductive metal thin film, attaching the conductive metal thin film to the inner cushioning agent through a mold, and applying a thermal mold and a cooling mold to the inner cushioning agent to which the conductive metal thin film is attached. A method of manufacturing a ground foam gasket for surface mounting of an electronic circuit board, comprising the step of forming through and hot aging a molded gasket at high temperature. The method of claim 4, wherein And forming a groove recessed inward in the mounting surface of the gasket during the molding through the hot mold. The method of claim 4, wherein The heat-resistant adhesive is a method for manufacturing a ground foam gasket for mounting the surface of the electronic circuit board mixed with metal powder. An electronic circuit board surface mounting ground foam gasket manufactured by the manufacturing method according to any one of claims 1 to 7. An internal cushioning agent including a foamed resin foam foamed in the form of an open cell and a silicone film coated on the cell surface forming the foamed resin foam; A conductive metal thin film attached to the outer surface of the inner cushion An electronic circuit board surface mounting ground foam gasket comprising a. The method of claim 8, The foamed resin foam is a ground foam gasket for mounting a surface of an electronic circuit board having at least one resin selected from polyurethane, NBR rubber, and CR rubber EPDM rubber in an open cell form. 10. The method according to claim 8 or 9, The inner cushioning agent is a ground foam gasket for mounting a surface of an electronic circuit board further comprising metal powder. The method of claim 9, And a heat resistant adhesive applied between the inner cushioning agent and the conductive metal thin film. The method of claim 11, The heat-resistant adhesive is a ground foam gasket for mounting the surface of the electronic circuit board further added metal powder. 10. The method according to claim 8 or 9, The gasket is a ground foam gasket for mounting an electronic circuit board surface having a groove recessed inwardly on a mounting surface of the electronic circuit board. The method of claim 13, Wherein the groove is applied to the electronic printed circuit board and the ground foam gasket for mounting the surface of the electronic circuit board formed in a form corresponding to the melt cross-sectional shape of the cream solder is melted between the gasket. The method of claim 14, The cream solder is applied on the electronic printed circuit board is a ground foam gasket for surface mounting electronic circuit board is applied at intervals of 1 ~ 2mm with a width of 2 ~ 4mm along the longitudinal direction of the gasket.

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