WO2005032223A1

WO2005032223A1 - Integrated structure for a flexible printed circuit boards and manufacturing method for the same

Info

Publication number: WO2005032223A1
Application number: PCT/KR2004/000809
Authority: WO
Inventors: Byung-Jae Yoon
Original assignee: Sanyang Electro Mechanics Co., Ltd.
Priority date: 2003-09-29
Filing date: 2004-04-07
Publication date: 2005-04-07
Also published as: KR20050031288A

Abstract

Disclosed herein are an integrated structure of flexible printed circuit boards, and a manufacturing method for the same. The integrated structure comprises a single base sheet (11), and a plurality of flexible printed circuit boards (12) arranged on the base sheet. Thee outline of each of the flexible printed circuit boards is formed with perforated slits (13) for dividing the flexible printed circuit boards individually as well as connection bridges (14) for connecting the flexible printed circuit boards with the base sheet. The integrated structure further comprises a reinforcing plate (17) made of an epoxy-based resin, and formed with cutting holes (18) at positions corresponding to the connection bridges. After components are mounted on the flexible printed circuit boards in a state wherein the base sheet is bonded to the reinforcing plate, as cutters (33) cut the connection bridges by penetrating through the cutting holes, it is possible to achieve individual flexible printed circuit boards.

Description

Description INTEGRATED STRUCTURE FOR A FLEXIBLE PRINTED CIRCUIT BOARDS AND MANUFACTURING METHOD FOR THE SAME Technical Field

[1] The present invention relates to an integrated structure for flexible printed circuit boards and a manufacturing method for the same, the method comprising the steps of forming a single base sheet so that a plurality of flexible printed circuit boards are arranged thereon, the outline of the respective flexible printed circuit boards being partially formed with perforated slits while the remaining connection bridges are used in the connection and fixing between the flexible printed circuit boards and the base sheet, forming a reinforcing plate made of an epoxy-based resin so that cutting holes are formed at positions corresponding to the connection bridges of the base sheet, printing a paint on portions of the reinforcing plate where the flexible printed circuit boards will be seated, bonding the base sheet to the reinforcing plate through thermo compression, mounting components on the flexible printed circuit boards, and cutting the connection bridges between the flexible printed circuit boards and the base sheet, thereby enabling production of individual flexible printed circuit boards, improving reliability of the products and overall productivity by reducing manufacturing costs. Background Art

[2] In general, printed circuit boards are manufactured by closely mounting many different kinds of components on a flat plate made of a phenol resin or epoxy resin, and further closely fixing circuits for use in the connection of the components to the surface of the flat resin plate. More particularly, after a copper foil or the like is bonded to one surface of a phenol resin or epoxy resin insulation plate and the like, etching is performed along wiring patterns of circuits so as to remove a part of the cooper foil except for linear circuits through corrosion, thereby producing desired circuit patterns, and then holes for use in the bonding and mounting of various components are punched.

[3] In the past, rigid printed circuit boards, which are manufactured by bonding a copper foil to an epoxy or phenol plate, were mainly used, but in recent years, flexible printed circuit boards have been developed and used. In case of flexible printed circuit boards, a copper foil is in close contact with or bonded to a base film made of flexible polyimide. [4] The flexible printed circuit boards are lighter than the epoxy or phenol based rigid printed circuit boards, and enable high-density packaging.

[5] Considering the manufacturing process of such a flexible printed circuit board, first, the flexible printed circuit board is obtained through a circuit printing process of printing circuits on a raw material, and a protective shield material and a surface treatment are applied to the flexible printed circuit board. In this case, the remaining exposed portion of the flexible printed circuit board is plated, and then cut along the outline thereof. After completing such a protective treatment process and outline process, the flexible printed circuit board is bonded to a reinforcing plate. In this reinforced state, desired components are mounted on the surface of the flexible printed circuit board, and the flexible printed circuit board is packaged after wire bonding and tap bonding of the mounted components being performed.

[6] In explaining why the flexible printed circuit board must be bonded to the reinforcing plate, since the flexible printed circuit board is too flexible and has a low shock resistance, thus being liable to cause elastic deformation thereof, the reinforcing plate serves to provide the component mounting surface of the flexible printed circuit board with the required flatness, and to fix and support the flexible printed circuit board.

[7] Therefore, before mounting the components on the flexible printed circuit board, the reinforcing plate, which is flat and has a certain rigidity, should be bonded and fixed under the component-mounting surface of the flexible printed circuit board.

[8] The flexible printed circuit board as stated above, however, when it is to be separated from the reinforcing plate after the mounting of the components is completed, has a problem in that it cannot be easily separated from the reinforcing plate due to the bonding properties of the adhesive.

[9] If the flexible printed circuit board bonded to the reinforcing plate is forcibly separated from the reinforcing plate by applying an excessive force, the flexible printed circuit board extends too far due to the properties of the raw material, resulting in a deterioration of reliability of the microcircuits.

[10] Meanwhile, the flexible printed circuit boards may be manufactured, without using a reinforcing plate, by seating the flexible printed circuit boards on specific mold dies and mounting desired components on each of the flexible printed circuit boards in a state wherein the flexible printed circuit boards are fixed through vacuum compression.

[11] In this case, there is a need for many different molds suitable for various kinds of the flexible printed circuit boards in order to achieve accurate molding. This results in several problems including an increase in manufacturing costs, and a reduction in productivity. Further, even if the flexible printed circuit board moves only a little, the reliability of products is seriously damaged. Disclosure

[12] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an integrated structure of flexible printed circuit boards, and a manufacturing method for the same, for allowing a single base sheet arranged thereon with a plurality of flexible printed circuit boards to be bonded to a reinforcing plate so that, after desired components are mounted on the flexible printed circuit boards, the flexible printed circuit boards can be blanked from the base sheet so as to complete individual products in a state wherein the base sheet is still bonded to the reinforcing plate, thereby improving productivity and reducing the chance of producing inferior products due to manual construction.

[13] It is another object of the present invention to provide an integrated structure of flexible printed circuit boards, and a manufacturing method for the same, for allowing a plurality of flexible printed circuit board arranged on a base sheet to be individually blanked so as to complete products by simply cutting specific portions of the base bonded to a reinforcing plate without damaging the reinforcing plate, thereby enabling semi-permanent use of the reinforcing plate, resulting in a reduction of material costs and processing costs.

[14] It is yet another object of the present invention to provide an integrated structure of flexible printed circuit boards, and a manufacturing method for the same, for preventing a plurality of flexible printed circuit boards arranged on a base sheet from being bonded to a reinforcing plate made of an epoxy-based resin even in a state where the base sheet is firmly bonded to the reinforcing plate through thermo compression by printing a paint on certain portions of the reinforcing plate where the flexible printed circuit board will be seated, thereby eliminating damage to the flexible printed circuit boards when they are separated from the reinforcing plate.

[15] In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of an integrated structure of flexible printed circuit boards, comprising: a single base sheet; a plurality of flexible printed circuit boards arranged on the base sheet; perforated slits formed at the base sheet for dividing the flexible printed circuit boards individually; connection bridges formed at the base sheet for connecting the flexible printed circuit boards with the base sheet; a re- inforcing plate bonded to the opposite side of component mounting surface; and cutting holes formed at the reinforcing plate, and positioned under the connection bridges, the cutting holes allowing penetration ofthe cutters there through, the cutters being used to cut the connection bridges.

[16] Preferably, the reinforcing plate may be made of an epoxy-based resin.

[17] Also, preferably, the reinforcing plate may be bonded to the base sheet through a thermo compression process.

[18] Preferably, the reinforcing plate may be printed with paint, the paint serving to prevent the flexible printed circuit boards from being bonded to the reinforcing plate.

[19] In accordance with another aspect of the present invention, there is provided a method of manufacturing flexible printed circuit boards, comprising the steps of: a) forming a singe base sheet so that a plurality of flexible printed circuit boards are arranged thereon, and perforate slits for dividing the flexible printed circuit boards individually, and connection bridges for connecting the flexible printed circuit boards with the base sheet are formed thereat; b) forming a reinforcing plate, to be bonded to the base sheet, so that cutting holes are formed at positions corresponding to the connection bridges of the base sheet; c) printing a paint on portions of the reinforcing plate where the flexible printed circuit boards will be seated; d) position fixing the base sheet with the reinforcing plate; e) firmly bonding the base sheet to the reinforcing plate through a thermo compression process; f) mounting components on the flexible printed circuit boards arranged on the base sheet, in a state wherein the base sheet is bonded to the reinforcing plate; g) cutting the flexible printed circuit boards from the base sheet by penetrating cutters through the cutting holes formed at the reinforcing plate until they cut the connection bridges formed at the base sheet; and h) separating the individually cut flexible printed circuit boards from the reinforcing plate.

[20] According to the integrated structure of the flexible printed circuit boards and manufacturing method for the same as stated above, after the single base sheet arranged thereon with a plurality of the flexible printed circuit boards is bonded to the reinforcing plate, and the desired components are mounted on the flexible printed circuit boards, the flexible printed circuit boards can be individually cut from the base sheet, thereby enabling a plurality of the flexible printed circuit boards to be manufactured with only one process, resulting in an increase of productivity and reduction in manufacturing costs. Description Of Drawings

[21] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjoining with the accompanying drawings, in which:

[22] Fig. 1 is a perspective view illustrating a base sheet and a reinforcing plate in accordance with the present invention;

[23] Fig. 2 is a flow chart showing a method of manufacturing flexible printed circuit boards in accordance with the present invention; and

[24] Fig. 3 is a schematic sectional view illustrating a cutting process of connection bridges in a state wherein the base sheet and reinforcing plate shown in Fig. 1 are bonded to each other. Best Mode

[25] As shown in Fig. 1, a plurality of flexible printed circuit boards 12 are arranged on a single base sheet 11.

[26] In this case, these flexible printed circuit boards 12 are separated from the base sheet 11 by perforated slits 13, which are formed at the base sheet 11 along the outline of each of the flexible printed circuit boards 12. The flexible printed circuit boards 12, however, are normally connected to the base sheet 11 without being completely separated therefrom under the influence of a plurality of connection bridges 14 extending partially along the outline of each of the flexible printed circuit boards 12. Alternately, the connection bridges 14 may extend throughout the outline of the respective flexible printed circuit boards 12 when there are no perforated slits.

[27] The base sheet 11 is adapted to be bonded to a reinforcing plate 17, and the reinforcing plate 17 is formed with cutting holes 18 at positions corresponding to the connection bridges 14 of the base sheet 11. That is, in a state wherein the base sheet 11 is bonded to the reinforcing plate 17, the cutting holes 18 are positioned under the connection bridges 14.

[28] Certain portions of the reinforcing plate 17, where the flexible printed circuit boards 12 will be seated, are printed with a paint 15, and then a curing or curing process of the paint 15 is followed. The paint 15 serves to prevent the flexible printed circuit boards 12 from becoming bonded to the reinforcing plate 17.

[29] When the reinforcing plate 17 made of an epoxy-based resin as a main material and the base sheet 11 are bonded and thermally compressed to each other, the base sheet 11 can be firmly bonded to the reinforcing plate 17 due to thermosetting components contained in the epoxy resin reinforcing plate 17, thereby achieving proper flatness and rigidity required to mount the desired components to the flexible printed circuit boards 12. Meanwhile, the UV curable or IR curable paint 15 serves to prevent the flexible printed circuit boards 12 from bonding to the reinforcing plate 17. As a result, when the flexible printed circuit boards 12 are processed to form individual products, the paint 15 serves to prevent deformation or loss of products.

[30] In this way, with the base sheet 11 and reinforcing plate 17 configured as stated above, a plurality of the flexible printed circuit boards 12 can be obtained from the single base sheet 11, resulting in an improvement in productivity.

[31] The base sheet 11 and reinforcing plate 17 are formed with a plurality of guide holes 19. The guide holes 19 can be divided into first, second, and third guide holes.

[32] The first guide holes are punched only on the base sheet 11, and adapted to allow position setting pins, provided in a primary mold set, to penetrate there through, thereby being used to fix the base sheet 11. In this fixed state, the base sheet 11 is formed at accurate positions with the connection bridges 14 and perforated slits 13 by making use of the primary mold set, and the flexible printed circuit boards 12 can secure dimensional accuracy.

[33] The second glide holes serve to allow the base sheet 11 and reinforcing plate 17 to be position fixed to each other at accurate positions. For this, the second guide holes are formed at the same positions of the base sheet 11 and reinforcing plate 17, so that position setting pins simultaneously penetrate there through during a position fixing process, thereby enabling the position fixing process to prcgress without requiring any dimensional correction.

[34] The second lide holes are preferably formed at corner regions of the base sheet 11 and reinforcing plate 17 since they serve to correctly fix the base sheet 11 and reinforcing plate 17.

[35] The third glide holes serve to set positions of cutters 33 relative to the base sheet 11 for enabling the cutters 33 to correctly cut the connection bridges 14 of the base sheet 11. Smilar to the second glide holes, the third glide holes are preferably formed at the same positions of the base sheet 11 and reinforcing plate 17.

[36] The reason why the guide holes are divided into the first, second, and third glide holes is that, since a material constituting the flexible printed circuit boards 12 is thin and weak, as the position setting pins penetrate through the glide holes, the glide holes inevitably experience deformation, for example, expanding up to an undesirable point. Further, as the position setting pins repeatedly penetrate through the guide holes, the glide holes suffer deterioration of positioning accuracy, thereby positioning the base sheet 11 and reinforcing plate 17 inaccurately.

[37] The number, position, size, and other factors of the first, second, and third guide holes are not fixed, and can be selectively adjusted during manufacturing.

[38] Now, a method of manufacturing the flexible printed circuit board 12 using the base sheet 11 will be explained with reference to Fig. 2.

[39] A plurality of flexible printed circuit boards 12 are arranged on the single base sheet 11 (step 10). The base sheet 11 is appropriately selected from among ones applicable for the formation of such flexible printed circuit boards.

[40] That is, in the step 10, after having a designed size of base sheet prepared with CCL (Copper Clad Laminate) made of copper and polyimide, a plurality of the flexible printed circuit boards 12 are formed on the base sheet 11.

[41] Although the flexible printed circuit boards 12 can be separated from the base sheet 11 by virtue of the perforated slits 13, they are normally connected and fixed to the base sheet 11 by making use of a plurality of the connection bridges 14, which partially extend along the outline of each of the flexible printed circuit boards 12.

[42] Considering the step 10 in detail, in a state wherein the base sheet 11 is punched with the first and second guide holes, and the position setting pins of the primary mold set penetrate through the first glide holes, the perforated slits 13 and connection bridges 14 are formed at the base sheet 11 by making use of the primary mold set. Through such a primary process, a plurality of the flexible printed circuit boards 12 are arranged on the base sheet 11.

[43] In this case, preferably, the mold set is further used to punch the third glide holes. The third glide holes are used for the correction of position in a secondary process. That is, during the secondary process, the cutters 33 of the mold set are used to accurately cut the connection bridges 14 of the base sheet 11. The cutters 33 will be explained later.

[44] After forming the base sheet 11 as stated above, the reinforcing plate 17 is formed in such a fashion that, when it is bonded to the opposite side of component mounting surface, the cutting holes 18 are positioned under the connection bridges 14 formed at the base sheet 11 (step 20).

[45] The reinforcing plate 17 is made of an epoxy-based thermosetting resin, and is punched with the second and third guide holes as stated above. The punching of these guide holes is performed at the same time as the punching of the cutting holes 18.

[46] Successive to the step 20, the reinforcing plate 17 is printed with paint 15 (step 30).

[47] The paint 15 is printed on certain portions of the reinforcing plate 17 where the flexible printed circuit boards 12 will be seated, thereby serving to prevent the flexible printed circuit boards 12 from bonding to the reinforcing plate 17. [48] By using the paint 15, even though the epoxy-based reinforcing plate 17 and base sheet 11 are firmly bonded to each other through thermo compression, it is possible to prevent the flexible printed circuit boards 12 arranged on the base sheet 11 from being bonded to the reinforcing plate 17. As stated above, the UV curable or IR curable paint 15 is suitable, but any other paints are acceptable if they have a function of preventing the flexible printed circuit boards 12 from being bonded to the reinforcing plate 17.

[49] After the printing step 30, the base sheet 11 and reinforcing plate 17 are position fixed to each other (step 40).

[50] Considering such position fixing, first, a doubled-sided tape is bonded to the edge of the base sheet 11, the position setting pins of the mold set penetrate through the second glide holes formed at the base sheet 11 and reinforcing plate 17 so as to allow the base sheet 11 and reinforcing plate 17 to be accurately positioned relative to each other, and then the base sheet 11 and reinforcing plate 17 are bonded to each other.

[51] Basically, the flexible printed circuit boards 12 have to have a certain flatness of the component mounting surface thereof, and have to be fixed and supported so as not to move vertically and horizontally, but the flexible printed circuit boards 12 are flexible, and are liable to be deformed due to shock. Therefore, the reinforcing plate 17, which is flat and has a high rigidity, should be bonded to the opposite side of component mounting surface.

[52] Meanwhile, between the paint printing step 30 and the position fixing step 40, there may be added step 90 of curing the paint printed reinforcing plate 17.

[53] The curing of the reinforcing plate 17 is for optimizing physical properties of the paint 15 printed thereon, so as not to bond to the flexible printed circuit boards 12. A curing temperature in the range of 60 °C to 200 °C is preferable, and a curing time in the range of 5min to 90min is preferable

[54] After the position fixing step 40, the base sheet 11 and reinforcing plate 17 are further firmly bonded to each other through thermo compression (step 50). As a result, when desired components are mounted on the flexible printed circuit boards 12 arranged on the base sheet 11, it is possible to prevent the base sheet 11 from being pushed on the reinforcing plate 17.

[55] That is, since the reinforcing plate 17 contains thermosetting components in its epoxy material itself, it can be bonded to the base sheet 11 by a certain bonding strength when it is thermally compressed.

[56] In this case, because the paint 15 is printed on the certain portions of the reinforcing plate 17 in the step 30, the flexible printed circuit boards 12 arranged on the base sheet 11 are not bonded to the reinforcing plate 17 in spite of such thermo compression.

[57] After that, the flexible printed circuit boards 12 are mounted with various kinds of desired components (step 60), and then a plurality of the flexible printed circuit boards 12 arranged on the base sheet 11 are cut respectively (step 70).

[58] In the cutting step 70, as shown in Fig. 3, as the cutters 33 vertically move, they penetrate through the cutting holes 18 positioned under a plurality of the connection bridges 14 in order to cut the connection bridges 14, thereby causing the flexible printed circuit boards 12 to be separated from the base sheet 11.

[59] In this step 70, the third glide holes formed at the base sheet 11 and reinforcing plate 17 serve as a guiding means for allowing the cutters 33 to accurately cut the connection bridges 14.

[60] In this way, finally, the flexible printed circuit boards 12 are separated from the reinforcing plate 17 (step 80).

[61] Since the flexible printed circuit boards 12 are not bonded to the reinforcing plate 17 due to the paint 15 printed on the corresponding portions of the reinforcing plate 17, each of the flexible printed circuit boards 12 can be safely separated from the reinforcing plate 17 without any loss.

[62] The resulting flexible printed circuit boards 12 can be packaged as individual products after completing an inspection course. Industrial Applicability

[63] As apparent from the above description, according to an integrated structure of flexible printed circuit boards and manufacturing method of the same of the present invention, a plurality of flexible printed circuit boards are arranged on a single base sheet so that, in a state wherein the flexible printed circuit boards come into separable contact with a reinforcing plate, various kinds of components are mounted on the flexible printed circuit boards, thereby reducing manual labor and consequently improving productivity.

[64] In contrast to the prior art wherein each of the flexible printed circuit boards are bonded to the reinforcing plate, according to the present invention, the single base sheet arranged thereon with a plurality of the flexible printed circuit boards is bonded to the reinforcing plate, resulting in optimal efficiency.

[65] Further, according to the present invention, the flexible printed circuit boards in contact with the reinforcing plate are not bonded to the reinforcing plate due to paint printed on the reinforcing plate even if the reinforcing plate is firmly bonded to the base sheet through thermo compression. Therefore, when the reinforcing plate is separated from the base sheet after the desired components are mounted on the flexible printed circuit boards, there is no deformation or malfunction of the flexible printed circuit boards.

[66] Furthermore, the reinforcing plate can maintain its required bonding properties even after a thermo compression process is repeatedly performed, by virtue of its epoxy resin properties and by controlling factors of the thermo compression process. Therefore, the reinforcing plate can be used semi-permanently.

[67] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[1] An integrated structure of flexible printed circuit boards, comprising: a single base sheet; a plurality of flexible printed circuit boards arranged on the base sheet; perforated slits formed at the base sheet for dividing the flexible printed circuit boards individually; connection bridges formed at the base sheet for connecting the flexible printed circuit boards with the base sheet; a reinforcing plate bonded to the opposite side of component mounting surface; and cutting holes formed at the reinforcing plate, and positioned under the connection bridges, the cutting holes allowing penetration of cutters there through, the cutters being used to cut the connection bridges. [2] The structure as set forth in claim 1, wherein the reinforcing plate is made of an epoxy-based resin. [3] The structure as set forth in claim 1, wherein the reinforcing plate is bonded to the base sheet through a thermo compression process. [4] The structure as set forth in claim 1, wherein the reinforcing plate is printed with paint, the paint serving to prevent the flexible printed circuit boards from bonding to the reinforcing plate. [5] The structure as set forth in claim 1, wherein both the base sheet and reinforcing plate are formed with a plurality of guide holes. [6] A method of manufacturing flexible printed circuit boards, comprising the steps of: a) forming a singe base sheet so that a plurality of flexible printed circuit boards are arranged thereon, and perforated slits for dividing the flexible printed circuit boards individually, and connection bridges for connecting the flexible printed circuit boards with the base sheet are formed at the singe base sheet; b) forming a reinforcing plate, to be bonded to the base sheet, so that cutting holes are formed at positions corresponding to the connection bridges of the base sheet; c) printing a paint on portions of the reinforcing plate where the flexible printed circuit boards will be seated; d) position fixing the base sheet to the reinforcing plate; e) firmly bonding the base sheet to the reinforcing plate through a thermo compression process; f) mounting components on the flexible printed circuit boards arranged on the base sheet, in a state wherein the base sheet is bonded to the reinforcing plate; g) cutting the flexible printed circuit boards from the base sheet by penetrating cutters through the cutting holes formed at the reinforcing plate until they cut the connection bridges formed at the base sheet; and h) separating the individually cut flexible printed circuit boards from the reinforcing plate. [7] The method as set forth in claim 6, wherein, during the step a) and b), the base sheet and reinforcing plate are punched with a plurality of guide holes for correction of the relative position there between. [8] The method as set forth in claim 6, between the step c) and the step d), further comprising the step of: i) curing the reinforcing plate. [9] The method as set forth in claim 8, wherein, in the step i), the curing temperature is in the range of 60 °C to 200 °C , and curing time is 5min to 90min.