KR101301185B1 - Dome switch for button of mobile type equipment and method of making the same - Google Patents

Abstract

PURPOSE: A dome switch for buttons of a portable terminal and a forming method thereof are provided to reduce the use of materials for converting the dome switch, to prevent foreign materials, and to stably attach a dome sheet. CONSTITUTION: A corresponding switch is composed by exposing two contact points (21,23) around a dome switch in a mobile phone FPCB including a conductive pattern (20) on a base film, installing a metal dome (30) on the contact points, and installing a dome sheet (40) covering the metal dome while forming a fusion layer (50) on an interface.

Description

Dome switch for button of mobile terminal and forming method {dome switch for button of mobile type equipment and method of making the same}

The present invention relates to a dome switch for a button or a key of a cellular phone or other portable terminal, and a method of forming the same.

A printed circuit board is formed by forming a circuit with a conductive metal layer on an insulator plate or film serving as a base film or a substrate. Patterning operations such as photolithography may be used to form the circuit.

Among printed circuit boards, flexible printed circuit boards (FPCBs) or flexible printed circuit boards, which can be easily bent by forming a base substrate from a soft material such as thin polyimide, are widely used in recent years. . Such flexible printed circuit boards are flexible, easy to deform, lightweight, and thin, and are widely used in portable electronic and communication devices.

The flexible printed circuit board is used alone or in combination with a rigid printed circuit board in the keypad assembly of a mobile phone, and is a tool for connecting an element circuit or switch such as a main board and an LCD window or a camera. It is used a lot as.

By the way, when the FPCB including the dome switch is used for the side key of the cellular phone, the thickness of the cellular phone continues to decrease according to the tendency of light and small size of the cellular phone, and the width of the FPCB also decreases accordingly.

In the case of forming a dome switch for a side key on such a narrow FPCB, it is difficult to attach a dome sheet covering the dome switch on the FPCB with a cover film that covers the top after forming a circuit element such as a lead or a switch in the base film. do.

Therefore, the dome sheet is conventionally formed by covering the metal dome only in a predetermined area to seal the metal dome so that foreign substances or moisture do not enter from the surroundings, thereby making the dome sheet wider to cover the entire metal dome and the surrounding area.

However, the work of winding around the dome switch and sealing from the periphery is difficult to automate, and there is a problem of time consuming and manpower cost due to manual work, and simply winding does not have good sealing effect, and the dome sheet is also consumed a lot of materials. The cost burden will also increase.

To remedy this, instead of winding a narrow FPCB into a dome sheet, the FPCB and dome sheet are covered to cover a portion of the FPCB, such as a perimeter containing a metal dome, so that no foreign matter enters the perimeter. The method of having an adhesive tape or an adhesive layer in between was sought. In other words, a method of forming an adhesive tape or an adhesive layer only at the periphery of the dome sheet has been attempted to bond the FPCB surface and the dome sheet only around the metal dome of the FPCB on which the metal dome is placed. However, since the adhesive layer is made of a material with too high fluidity, the dome sheet is removed from its place by external force, and the adhesive layer is pushed outwards, causing difficulties in subsequent work, or causing inflow of foreign materials. The pressing operation may not be smooth or may cause an abnormal operation.

Registered Patent No. 1153993

The present invention is to solve the problems of the prior art as mentioned above, in combining the dome sheet covering the metal dome in the dome switch area of the FPCB for the button of the portable terminal, due to the fluidity problem, such as conventional adhesive layer dome An object of the present invention is to provide a method of attaching a dome sheet, which can prevent the occurrence of abnormal switch functions.

An object of the present invention is to provide a dome switch structure for a portable terminal button and a method of forming the same that can stably attach an FPCB and a dome sheet, effectively block foreign material inflow, and reduce the use of materials.

The dome switch structure of the present invention for achieving the above object is

In the FPCB for the portable terminal button having the conductive pattern formed on the base film, the two contacts at the center and the periphery of the dome switch are exposed apart from each other, and the convex shape of the metal dome touches the peripheral contact and does not touch the center contact. The dome sheet is installed in a state, and the dome sheet covering the metal dome is characterized in that the dome sheet is installed in the state of ultrasonic welding with the base film at the outer portion of the peripheral contact in the FPCB.

In the present invention, both the base film and the dome sheet for the FPCB may be made of a polymer resin. Wherein the polymer resin is selected from the group consisting of thermoplastic polymers, thermosetting polymers, polyurethanes, polyolefins, polyvinyl alcohols, polyethylene terephthalates, polyimides, copolymers of two or more of the polymer resins and mixtures of two or more of the polymer resins It may be.

In general, FPCB base films are often made of heat-resistant polyimide, but in order to increase the effectiveness of ultrasonic welding, the base film has a low melting point compared to polyimide, and is amorphous, soft and easy to be fused. Can be used.

The polymer resin constituting the base film and the dome sheet is preferably the same in terms of fusion strength, but may be of different materials. However, it should be chosen so that the difference in melting point between the two materials is not greater than 20 degrees Celsius.

In the method of the present invention for forming the structure of the present invention, the FPCB forming step (S10) of forming the FPCB exposed two contacts for the dome switch, the metal dome in the periphery of the two contacts in the periphery contact position of the center Aligning the dome sheet (S20), the dome sheet is placed so that the dome sheet covers the metal dome, and the dome sheet and the base film of the FPCB are contacted outside the peripheral contacts of the two contacts while the dome sheet covers the metal dome. Sheet alignment step (S30), the jig or tool horn connected to the main horn of the ultrasonic welding machine outside the peripheral contact is in close contact with the dome sheet and the insulating base in the area in contact with the jig or tool horn Ultrasonic fusion step (S40) to make a molten or partially melted state, the cooling jig to remove the jig and cooling (S50) is made.

In the method of the present invention, the FPCBs may be processed separately, but a plurality of FPCBs are processed at one time using an assisting tool, and a jig connected with an ultrasonic horn is also outside the periphery contact of each dome switch of the plurality of FPCBs. While the film is in close contact with each other, the shape can be made to be fused by heating.

According to the present invention in combining the dome sheet covering the metal dome in the dome switch area of the button FPCB of the portable terminal, it is possible to attach the dome sheet stably, effectively block the inflow of foreign matter to the dome switch, dome switch The use of materials for covering can be reduced.

1 is a schematic cross-sectional view showing the structure of a dome switch portion of the present invention;
2 is a flow diagram illustrating one embodiment of the method of the present invention.
Fig. 3 is a conceptual diagram showing a state where a plurality of FPCBs for a mobile phone side key are placed together on a support in one step of implementing the method of the present invention.
FIG. 4 is a conceptual diagram showing the form of sheets or tapes arranged in a matrix corresponding to the FPCB of FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, in a FPCB for a mobile phone side key in which a conductive pattern 20 is formed on a base film 10, two contacts 21 and 23 at a center and a periphery of a dome switch are exposed to be spaced apart from each other. (21, 23) The convex shape of the metal dome 30 is installed in contact with the peripheral contact 21, but not the center contact 23, the dome sheet 40 covering the metal dome 30 is The peripheral portion of the FPCB is ultrasonically fused with the base film 10 at the outer portion of the peripheral contact portion so as to form a fusion layer 50 at the interface.

Here, the base film 10 and the dome sheet 40 for the FPCB 100 are all made of a polymer resin. Polymer resins can be used in a wide variety of ways, for example, thermoplastic polymers, thermosetting polymers are all possible, polyurethane, polyolefin, polyvinyl alcohol, polyethylene terephthalate (PET), polyimide (PI), two of the polymer resins It may be selected from the group consisting of at least two copolymers and a mixture of two or more of the polymer resins.

In general, FPCB base films are often made of heat-resistant polyimide (PI) or PET, but here, in order to increase the effectiveness of ultrasonic welding, the base film has a lower melting point than polyimide, and is amorphous and soft. It can be formed using an easy polymer resin.

In the case of using the thermosetting resin, it is also conceivable to form the base film and the dome sheet with the base material before the thermosetting, and then to perform the thermosetting at the portion while performing the ultrasonic fusion treatment.

The polymer resin constituting the base film and the dome sheet is made of the same material. When fusion-bonded, the molecules constituting the two sheets of material are reconstituted by heat to form a molecular structure integrated with the material. Therefore, the mechanical strength corresponding to the strength of the material itself is increased. Although it is preferable in terms of strength, the base film is particularly superior in strength and heat, and the dome sheet may be formed of another material having a low melting point with strong adhesion to the base film. However, if the melting point difference between the two materials is more than 22 ℃ is usually known to be difficult to fusion, so select so that the difference in melting temperature is not large.

2 shows a flowchart of one embodiment of the method of the present invention.

In this embodiment, first, an FPCB is formed in which two contacts for a dome switch are exposed. This can be done in the same manner as the process of forming an FPCB for a mobile phone side key. For example, a base film is prepared, a metal layer is formed on the base film, a metal pattern is formed through photoresist coating, pattern exposure using a mask, development, and cleaning, and a coverlay film is laminated as necessary. The pattern forms to the outside. For example, the two contacts forming the dome switch are also formed to be exposed to the outside.

Position the metal dome according to the contact position on the FPCB for the side key with the dome switch contacts exposed. Naturally, the metal dome is aligned so that the periphery is positioned at the periphery contact position between the two contacts, and the convex up center part is positioned above the central contact point location between the two contacts.

Next, place the dome sheet on the FPCB where the metal dome is placed. The dome sheet covers the metal dome and is arranged so as to be in direct contact with the base film of the FPCB at the outer side of the two contacts. When the dome sheet is placed, an adhesive layer or a double-sided adhesive tape may be installed on a portion of the dome sheet so as not to distract once arranged.

In this case, the metal dome and the dome sheet are arranged on the FPCB in turn, but the metal dome is first aligned with the dome sheet, and the metal dome and the dome sheet are aligned and combined with the FPCB at once. It will be possible.

Outside the peripheral contacts, a jig or tool horn connected to the main horn of the ultrasonic splicer melts or partially melts the dome sheet and insulating base in the area in contact with the jig or tool horn. . In this case, the ultrasonic fusion is formed in a narrow closed curve, and the width should be made narrow and precise as about 0.3 to 1mm, so that the width of the jig to be touched for ultrasonic welding on the dome sheet is about the same size. This is because the ultrasonic fusion is heated and melted only in the area where the jig touches, and the width is the same because the melted area is not well melted even in the adjacent area.

The time required for the ultrasonic welding is related to the total area of the jig contacting the dome sheet and the output of the ultrasonic welding machine, and can be achieved even in a short time of about 0.1 seconds. Therefore, it is possible to increase the work efficiency according to the fast process. Even if the cost of equipment is high, only one can increase the processing efficiency.

However, the FPCB for the side key is very small, and the dome sheet or other cover attached thereto is very small, and the fused portion is only the periphery of the dome sheet, so that a plurality of FPCB ( 100) to arrange in a matrix form, such as by using the auxiliary die 110, and the metal dome, dome sheet, and other tape attachments are also prepared in the same number as the tape 200 alignment form of FIG. It is desirable to allow fusion to occur for many of these at once to increase the efficiency of the ultrasonic fusion machine and to increase the overall process efficiency.

In this case, when arranging a plurality of FPCBs in a matrix form, as shown in FIG. 2, the regions A to be attached to the tape are arranged on the auxiliary die 110 to be gathered together in position. The tape is placed on the outside, and the tape is arranged in a matrix form in accordance with the area A of FIG. 2 so that the tape can be easily aligned and the inconvenience caused by the area B can be reduced.

The jig, which is coupled to the horn of the ultrasonic fusion machine, for the simultaneous operation of the multiple FPCBs, has a plurality of closed curves in contact with the dome sheet to work with the multiple FPCBs.

In this case, the time of work of one frame can be prevented from being too short, and the temporal adjustment of the work is facilitated, and the quality of the work can be improved by adjusting the work.

The application of the ultrasonic power may be at the moment when the jig touches the dome sheet, but it is also possible to apply the ultrasonic power just before the touch. The power level, time, and pressure for the ultrasonic output may vary depending on the material to be fused, so no specific numerical value is mentioned.

Ultrasonic fusion is made evenly so that the dome switch is well sealed by peripheral fusion of each dome switch so that the flatness of the material placement side and the thickness of the dome sheet and the FPCB, which are the materials, are evenly made.

Working with ultrasonic fusion keeps the material very clean and reduces the need to clean and remove any oil film or dirt separately. This is because at the moment of ultrasonic fusion, the removal work on them is performed together. In addition, a separate adhesive layer, adhesive material, adhesive tape is not required, so the process can be simplified and material can be saved. In addition, mass mechanization is much easier than for individual tape windings.

When fusion is performed, the base film is usually thick and the dome sheet is thin so that they cannot be melted to the same extent, but at the interface, the two layers are at least partially melted so that the resin molecules forming the two layers are recombined to exhibit bonding strength. It should be done.

After the fusion time, the jig bonded to the horn is spaced apart from the fusion sheet dome sheet and FPCB, so the molten or partially melted portion (outside of the outer contact) is immediately cooled to a firm and stable state. do.

Then, when a plurality of side key FPCBs are ultrasonically fused at the same time, the separation (following) is followed because each FPCB must be separated in order to be used in a mobile phone or the like.

Ultrasonic welding is not only fusion but also capable of cutting functions, so the shape of the jig can be adjusted together with the ultrasonic melting cutting to separate the individual FPCB with fusion. In this case, since the ultrasonic welding part is hardened and the stress is concentrated, it may also serve to prevent a problem in a subsequent separation operation.

Ultrasonic cutting may be made in part in the form of forming a broken line in advance without reaching complete separation. In this case, the separation operation can be completed by cutting at the remaining bonding point without being completely cut in a subsequent process.

In the above, the present invention has been described through a limited embodiment related to a side key FPCB of a mobile phone, but the present invention has been described by way of example only for better understanding of the present invention, and the present invention is not limited to these specific embodiments. That is, one of ordinary skill in the art to which the present invention pertains may make various modifications or applications based on the present invention, and such modifications and applications belong to the appended claims.

10: base film 20: contact
30: metal dome 40: dome sheet
50: fusing layer 100: FPCB
110: auxiliary die

Claims (4)

In the FPCB for the portable terminal button having the conductive pattern formed on the base film, the center contact point and the peripheral contact point of the dome switch are exposed in a spaced state.
The periphery of the metal dome of the convex shape upwards on the center contact and the peripheral contact is installed in contact with the peripheral contact,
A dome switch for covering the metal dome, and a dome sheet having a peripheral portion forming an ultrasonic welding layer at an interface with the base film at an outer portion of the peripheral contact point in the FPCB is installed. The method of claim 1,
The base film and the dome sheet is made of a polymer resin,
The polymer resin is selected from the group consisting of thermoplastic polymers, thermosetting polymers, polyurethanes, polyolefins, polyvinyl alcohols, polyethylene terephthalates, polyimides, copolymers of two or more of the polymer resins and mixtures of two or more of the polymer resins. Dome switch for a portable terminal button, characterized in that. An FPCB forming step of forming an FPCB exposing two contacts for a dome switch,
The metal dome and the dome sheet is aligned with the FPCB, and the dome sheet covers the metal dome and the metal dome is placed so that the dome sheet and the base film included in the FPCB are in contact with each other outside the peripheral contact points of the two contacts. And dome sheet alignment step,
Ultrasonic welding step of making a jig connected to the main horn of the ultrasonic welding machine outside the peripheral contact point to make the dome sheet and the base film melt or partially melt in the contact area with the jig,
And a cooling step of removing the jig from the dome sheet and cooling the fused portion. The method of claim 3, wherein
After the forming of the FPCB, the plurality of FPCBs are arranged in a matrix form on the guide,
In the ultrasonic welding step, the ultrasonic welding is performed simultaneously on all of the plurality of FPCB by the coupling jig formed together with the fusion processing unit for each of the plurality of FPCB.

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