CN214757062U

CN214757062U - Pressing and stacking structure of flexible circuit board

Info

Publication number: CN214757062U
Application number: CN202120314138.4U
Authority: CN
Inventors: 吴金银; 卢苇; 郭小春
Original assignee: Suzhou Mflex Electronic Co ltd
Current assignee: Suzhou Mflex Electronic Co ltd
Priority date: 2021-02-03
Filing date: 2021-02-03
Publication date: 2021-11-16
Anticipated expiration: 2031-02-03

Abstract

The application discloses pressfitting stack structure of flexible circuit board, including gasbag (2), reinforcement layer group (4), flexible circuit board (5), packing membrane (60) and the iron plate (3) of baking that set gradually, flexible circuit board (5) include base plate (50) and set up in first copper layer (51) of base plate (50) one side, first copper layer (51) include this somatic part (511) and annular pad (510), flexible circuit board (5) still including set up in this somatic part (511) with ink layer (53) between packing membrane (60), ink layer (53) are provided with ink layer opening (530), during the pressfitting, packing membrane (60) flow after being heated to in ink layer opening (530) support annular pad (510), prevent that annular pad is crooked, sunken, effectual roughness that improves annular pad, the microphone is welded to the annular bonding pad, and the welding quality and the use reliability are guaranteed.

Description

Pressing and stacking structure of flexible circuit board

Technical Field

The application relates to the technical field of flexible circuit board fast pressing, in particular to a pressing and stacking structure of a flexible circuit board.

Background

A Flexible Printed Circuit (FPC) is a Printed Circuit board having high reliability and excellent flexibility, which is made of Polyimide (PI) or a polyester film as a base material. The flexible circuit board has the characteristics of high wiring density, light weight, thin thickness and good bending property.

With the development of the technology, various sensing components and functional components are more and more integrally welded on the flexible circuit board. In order to enable the soldering of components to the flexible circuit board, PADs (PAD) for soldering components are provided on the flexible circuit board. As shown in fig. 1, fig. 1 shows a flexible circuit board having a circular ring-shaped pad 100, the pad 100 is used for welding with a Microphone (MIC), a base layer 1 of the flexible circuit board is exposed to the inside of the pad 100, a sound transmission hole 1a is opened on the base layer, and the closed pad is welded with a corresponding pad on the microphone in a subsequent assembly process to form a closed sound absorption space.

In order to ensure the sound transmission effect, the conventional flexible circuit board generally includes a base layer 1, a pad layer 10 on one side of the base layer 1, a copper layer 11 on the other side of the base layer 1, and a protective film 12 attached to the surface of the copper layer 11, wherein the pad layer 10 is provided with an annular pad 100. In order to ensure the reliability of the annular pad 10 in the subsequent soldering and use processes, a pair of annular pads 10 on the flexible printed circuit board needs to be reinforced by pressing a support material, such as PI, FR4, onto the back surface of the annular pad through a pressing process. The press lamination during reinforcement in the prior art is shown in fig. 2, and includes, from top to bottom, an upper air bag 13 of the fast press, a first release film 14, a reinforcement layer 15, a reinforcement glue layer 16, a protective film 12, a copper layer 11, a base layer 1, a pad layer 10, an ink layer 17, a second release film 18, a rubber layer 19 of the lower chassis of the fast press, and a steel plate layer 190 of the lower chassis of the fast press.

In order to guarantee the sound transmission effect, the supporting material needs to be provided with the opening 150 corresponding to the sound transmission hole 1a, the annular bonding pad 100 is stressed and bent during pressing due to the suspension design, the flatness is poor, the problem of element floating height false welding occurs after the annular bonding pad is assembled in a furnace, and the reliability of welding the annular bonding pad 100 and the stability of using the annular bonding pad after welding are not guaranteed.

SUMMERY OF THE UTILITY MODEL

Aiming at the defects in the technology, the application provides the pressing and stacking structure of the flexible circuit board, which can improve the flatness of the annular bonding pad in pressing.

In order to solve the technical problem, the technical scheme adopted by the application is as follows: the utility model provides a pressfitting stack structure of flexible circuit board, is including the gasbag, the reinforcement layer group that set gradually, flexible circuit board, filling membrane and the iron plate of paying of baking, flexible circuit board include the base plate with set up in the first copper layer of base plate one side, first copper layer includes body portion and annular pad, flexible circuit board still including set up in body portion with fill the printing ink layer between the membrane, the printing ink layer is provided with printing ink layer opening, during the pressfitting, it flows to fill the membrane after being heated in the printing ink layer opening support annular pad.

Further, the thickness of the filling film is 80-120 mu m.

Further, a second release film is arranged on the surface, facing the ink layer, of the filling film.

Further, the thickness of the second release film is 10-20 μm.

Furthermore, the press-fit stacking structure of the flexible circuit board further comprises a buffer layer and a hard board which are sequentially arranged between the filling film and the baked iron plate.

Further, the buffer layer is glass fiber paper.

Further, the thickness of the buffer layer is 70-180 mu m.

Further, the hard plate is a steel plate.

Further, the surface of the filling film facing the buffer layer is provided with a third release film.

Further, the reinforcement layer group including set gradually in the gasbag with strengthening layer and glue film between the flexible circuit board, the strengthening layer opening has been seted up to the strengthening layer, the glue film has been seted up the size and is greater than strengthening layer open-ended glue film opening.

Compared with the prior art, the application has the beneficial effects that:

1. by arranging the filling film below the ink layer, the filling film can flow into the opening of the ink layer after being heated and is supported below the annular bonding pad in the pressing process, so that the annular bonding pad is prevented from being bent and sunken, the flatness of the annular bonding pad is effectively improved, a follow-up microphone is favorably welded to the annular bonding pad, and the welding quality and the use reliability are ensured;

2. by arranging the buffer layer and the hard plate which are positioned below the filling film, the filling film can be effectively ensured to flow into the opening of the ink layer in the pressing process, and the filling film is ensured to play a supporting role; meanwhile, the flexible circuit board can be kept flat in the pressing process, and the pressing quality is ensured;

3. through set up from the type membrane in filling membrane both sides, can conveniently get rid of after the pressfitting and fill the membrane, improve production efficiency and production quality.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts. Wherein:

fig. 1 is a schematic plan view of a prior art flexible circuit board.

Fig. 2 is a schematic diagram of a press-fit stack-up of a flexible circuit board in the prior art.

Fig. 3 is a schematic view of a press stack of the flexible circuit board of the present application.

FIG. 4 is a schematic representation of the structure of a composite membrane in the present application.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. It should be further noted that, for the convenience of description, only some of the structures related to the present application are shown in the drawings, not all of the structures. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terms "comprising" and "having," as well as any variations thereof, in this application are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

As shown in fig. 3, a press-fit stacking structure for improving the flatness of a circular pad of a flexible circuit board according to a preferred embodiment of the present invention includes an uppermost air bag 2, a lowermost baked iron plate 3, a reinforcing layer group 4 between the air bag 2 and the baked iron plate 3, a flexible circuit board 5, and a composite film 6.

The air bag 2 and the baking iron plate 3 are pressing parts of a vacuum fast press, the air bag 2 and the baking iron plate are matched to press the middle layers together, and meanwhile, the air bag 2 has a heating function. The baked iron plate 3 includes a rubber pad 30 and a steel plate 31 connected below the rubber pad 30, and the two are combined together by a sintering heat treatment. The baked iron plate 3 combines various advantages of the steel plate 31 and the rubber pad 30, has good smoothness and heat conduction buffering performance, and enables a product to be well formed and to have better filling performance and combining performance.

The flexible circuit board 5 includes a base layer 50 and first and

second copper layers

51 and 52 connected to both sides of the base layer 50, respectively.

The base layer 50 may be made of Polyimide (PI) or polyester film, and in this embodiment, the material is polyimide, and a center hole 500 is formed in the center of the base layer 50.

The first copper layer 51 includes a body portion 511 and an annular pad 510, and a gap 512 is formed between the annular pad 510 and the body portion 511. The annular pad 510 is preferably made of gold, and is provided with a first clearance hole 5100 coaxially disposed with the central hole 500.

The ink layer 53 is disposed on the surface of the body portion 511, and the ink layer 53 does not cover the annular pad 510, so that an ink layer opening 530 is formed on the ink layer 53.

The second copper layer 52 is provided with a second avoiding hole 520 coaxial with the central hole 500, and the sizes of the second avoiding hole 520 and the first avoiding hole 5100 are both larger than that of the central hole 500, so that sound can reliably enter from the central hole 500. In a preferred embodiment, the first clearance hole 5100 and the second clearance hole 520 have the same shape and size.

A protective film 54 is disposed on the surface of the second copper layer 52 for protecting the flexible circuit board, and has a protective film opening 540 disposed coaxially with the central hole 500 and having a size larger than that of the central hole 500.

In this embodiment, the ring-shaped bonding pad 510 is used for welding a microphone, and has a circular central hole 500, and the first avoiding hole 5100, the second avoiding hole 520, the ink layer opening 530, and the protection film opening 540 are also circular. In other embodiments, other components may be soldered to the annular pad 510, and the holes may have other shapes.

The reinforcement layer group 4 includes a reinforcement layer 40 and a glue layer 41 disposed on the reinforcement layer 40. In this embodiment, the reinforcing layer 40 is made of FR4, and has a reinforcing layer opening 400 coaxially disposed with the central hole 500, and the shape and size of the reinforcing layer opening 400 are the same as the first clearance hole 5100, so that the reinforcing layer 40 can provide support for the annular pad 510 more fully.

The glue layer 41 is used for connecting the reinforcing layer 40 and the protection film 54, and has a glue layer opening 410 similar to the protection film opening 540.

A first release film 9 is arranged between the reinforcing layer 40 and the air bag 2 to prevent the reinforcing layer 40 from being adhered to the air bag 2 after lamination, and the flexible circuit board after lamination can be conveniently separated from the air bag 2.

The composite film 6 is used for supporting the annular pad 510 in the ink layer opening 530 in the pressing process, so that the pressed annular pad 510 is more flat, as shown in fig. 4, the composite film 6 includes a filling film 60, and a second release film 61 and a third release film 62 respectively connected to two sides of the filling film 60.

The filling film 60 is transformed into a glass state after being heated (70-100 ℃), so that the filling film flows into the ink layer opening 530 and is supported at the bottom of the annular bonding pad 510, and the annular bonding pad 510 is prevented from being sunken and bent during pressing, and defects such as welding and poor use are avoided. The material of the filling film 60 may be, for example, one or more of PE, PVC, PP, or one or more of modified materials of the foregoing materials. The release films on both sides of the filling film 60 can prevent the filling film 60 from adhering to the annular pad 510 and other components, so that the composite film 6 can be conveniently removed after the pressing process is completed.

The thickness of the filling film 60 is 80-120 mu m, and preferably, the thickness of the filling film 60 is 90 mu m; the thickness of the second release film 61 and the third release film 62 is 10 to 20 μm, preferably 15 μm. The filling film 60 and the release film with the above thicknesses can effectively ensure that the composite film 6 reliably supports the annular pad 510 in the pressing process.

Still be provided with buffer layer 7 and hard board 8 between complex film 6 and baked iron plate 3, buffer layer 7 is located between complex film 6 and the hard board 8, plays the effect of buffering in the pressfitting process, and preferred, this buffer layer 7 is glass fiber paper, and thickness is 70 ~ 180 mu m, preferably 130 mu m, and the glass fiber paper of this thickness range can reliably play the cushioning effect.

The hard plate 8 is positioned between the buffer layer 7 and the baked iron plate 3, in the pressing process, the hard support of the hard plate 8 can ensure that the flexible circuit board 5 is kept flat in the pressing process, and due to the buffering effect of the buffer layer 7, even if slight defects exist on the surface of the hard plate 8, inferior-quality products cannot be generated, and the yield is effectively improved; simultaneously, the cooperation of the hard plate 8 and the buffer layer 7 can ensure that the composite film 6 can be filled into the ink layer opening 530 to be supported in the pressing process, so that the flatness of the annular bonding pad 510 is ensured.

In the present application, the material of the first release film 9, the second release film 61 and the third release film 62 is preferably teflon, wherein the thickness of the first release film 9 is preferably 25 μm.

The utility model provides a flexible circuit board's pressfitting stack structure possesses following advantage at least:

1. by arranging the filling film below the ink layer, the filling film can flow and fill into the opening of the ink layer after being heated in the pressing process and is supported below the annular bonding pad, so that the annular bonding pad is prevented from being bent and sunken, the flatness of the annular bonding pad is effectively improved, a subsequent microphone is favorably welded on the annular bonding pad, and the welding quality and the use reliability are ensured;

The above description is only for the purpose of illustrating embodiments of the present invention and is not intended to limit the scope of the present invention, and all modifications, equivalents, and equivalent structures or equivalent processes that can be used directly or indirectly in other related fields of technology shall be encompassed by the present invention.

Claims

1. The utility model provides a pressfitting stack structure of flexible circuit board, characterized in that, including gasbag (2), reinforcement layer group (4), flexible circuit board (5), filling membrane (60) and the iron plate (3) of baking that set gradually, flexible circuit board (5) include base plate (50) and set up in first copper layer (51) of base plate (50) one side, first copper layer (51) include body portion (511) and annular pad (510), flexible circuit board (5) still including set up in body portion (511) with ink layer (53) between filling membrane (60), ink layer (53) are provided with ink layer opening (530), during the pressfitting, filling membrane (60) flow after being heated to in ink layer opening (530) support annular pad (510).

2. The press stack of flexible circuit boards according to claim 1, wherein the thickness of the filling film (60) is 80 to 120 μm.

3. The press stack of flexible circuit boards according to claim 1, wherein the surface of the filling film (60) facing the ink layer (53) is provided with a second release film (61).

4. The press stack of flexible circuit boards according to claim 3, wherein the thickness of the second release film (61) is 10 to 20 μm.

5. A compression stack of flexible circuit boards according to any one of claims 1 to 4 further comprising a buffer layer (7) and a hard board (8) disposed in sequence between the filler film (60) and the bake iron plate (3).

6. A press stack of flexible circuit boards according to claim 5, characterised in that the cushioning layer (7) is a glassfibre paper.

7. A press stack of flexible circuit boards according to claim 6, wherein the thickness of the buffer layer (7) is 70-180 μm.

8. A press stack of flexible circuit boards according to claim 5, characterised in that the rigid board (8) is a steel plate.

9. A press stack of flexible circuit boards according to claim 5, characterised in that the surface of the filling film (60) facing the buffer layer (7) is provided with a third release film (62).

10. A press stack of flexible circuit boards according to any one of claims 1 to 4, wherein the set of reinforcement layers (4) comprises a reinforcement layer (40) and a glue layer (41) sequentially disposed between the bladder (2) and the flexible circuit board (5), the reinforcement layer (40) defines a reinforcement layer opening (400), and the glue layer (41) defines a glue layer opening (410) having a size larger than the reinforcement layer opening (400).