Patent Application
20250142726
This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2023-184004 filed Oct. 26, 2023, the description of which is incorporated herein by reference.
The present disclosure relates to a film-type circuit such as an FPC (Flexible Printed Circuit) and an FFC (Flexible Flat Cable) and connection of the film-type circuit to an PCB (Printed Circuit Board), and in particular, to how the film-type circuit is connected between two PCBs for connection of the two PCBs.
A film-type circuit is known as an FPC and an FFC, which have a thin flat and flexible electronic circuit including electronic wirings. For example, such a film-type circuit is known by a patent reference 1 disclosed by JP-A 2012-49297.
This patent reference 1 exemplifies an FFC functioning as a film-type circuit, in which multiple conductors arranged in parallel in the width direction of the conductors are bonded and covered with an insulating film in the thickness direction of the conductors to form a single wiring device. In addition, exposed portions where the conductors are partly exposed from the insulating film are formed at both ends of the conductor in the longitudinal direction. Each of the exposed portions on both end sides is bonded to a corresponding electrode provided on each printed circuit board (PCB), thus mutually connecting the two printed circuit boards via the film-type circuit.
In the connection structure shown in Patent Document 1, the electrodes (wiring patterns) of the two printed circuit boards are connected by an FFC (film-type circuit).
In such a structure, the FFC is frequently entirely warped or curved to delineate a gentle arc when viewed from a side thereof even before assembly with the printed circuit boards. Hence, if the FFC is warped, it becomes difficult to mate the foregoing positioning conductors with the foregoing holes on both the printed circuit boards, i.e., it becomes difficult to accurately position the FFC with respect to both the printed circuit boards. In particular, when the printed circuit boards and the film-type circuit are automatically positioned by a positioning device, such difficulties are unacceptable.
It is thus desired to accurately align a film-type circuit to both printed circuit boards when the film-type circuit connecting the wiring patterns of the two printed circuit boards is warped.
As an exemplary embodiment, there is provided a film-type circuit to be connected with two printed circuit boards, comprising:
In this configuration, the film-type circuit is warped such that the partial connection side of each of the connection parts is directed inward in a warped curve and the connection parts positioned to be closer in the predetermined direction compared to a state where the film-type circuit is flat. Moreover, the film-type circuit has at least two through-holes formed at designated positions in the film-type circuit, the designated positions being set to have no overlapping between the insulation layer and the wiring patterns, to be located in a center portion in the predetermined direction, and to be separated from each other in a direction orthogonal to the predetermined direction.
It is preferred that the film-type circuit comprises a plurality of reinforcing terminals made of an electrically conductive material, each formed to have a width larger than a width of the respective wiring patterns, and positioned restrictively at end portions of the film-type circuit in both a direction orthogonal to the predetermined direction and the predetermined direction, wherein the designated positions of the through-holes are set in end areas of the film-type circuit in the direction orthogonal to the predetermined direction, each of the designated positions in the respective end areas being located between two of the reinforcing terminals opposed to each other on the film-type circuit in the predetermined direction.
It is also preferred that the film-type circuit the through-holes are two in number. The through-holes may be equal in sizes thereof to each other or different in sizes thereof from each other.
Another exemplary embodiment of the present disclosure relates to a method of mutually connecting the two printed circuit boards via a film-type circuit, comprising preparing, fixing, bringing and guiding steps. Of these steps, the preparation step prepares a film-type circuit, comprising:
In the fixing step, the two printed circuit boards fixed onto a positioning jig provided with at least two positioning pins. In a joining step, the film-type circuit and the positioning pin are brought close together such that the positioning pins are inserted into the through-holes, respectively, from the connection sides of the connection parts of the film-type circuit. Further, the film-type circuit is guided on and along the warpage such that the positioning pins are closer to the through-holes located at the center in the predetermined direction.
When mounting a film-type circuit on printed circuit substrates according to a conventional technique, positioning accuracy of the film-type circuit to the substrates may be reduced due to a warpage of the film-type circuit, of which whole portion is curved in its length, i.e., in its predetermined direction. If it is desired to use the component with no such warpage, yield and part costs for producing such a component are confronted with difficulties.
In contrast, the foregoing exemplified embodiments basically feature that, when the film-type circuit is loaded between two printed circuit boards for mutual electrical connection, the film-type circuit is given a curved shape in its length, i.e., a warpage in advance in a side view. How the warpage (or the curved surface in a side view) is generated positionally and in size can be controlled by adjustably adding through-holes to the film-type circuit. Hene, by using an inexpensive film-type circuit and positively utilizing the warpage (curve) generated on such an inexpensive film-type circuit, it is possible to improve yield and reduce costs during manufacturing.
Other various advantageous operations and effects derived from the foregoing exemplary embodiments will be described later together with explanations of the accompanying drawings.
In the accompanying drawings:
With reference to the accompanying drawings, an embodiment of a film-type circuit will now be described.
The film-type circuit can be provided as a film-type circuit such as an FPC (Flexible Printed Circuit) and an FFC (Flexible Flat Cable). In the present embodiment, the film-type (shaped) circuit will be explained as an FFC provided with a plurality of liner wiring patterns (composing a wiring area) in a designated direction thereof. The FFC is shaped into a thin flexible rectangular flat plate, but as being flexible, the FFC can easily be warped in a substantially controllable manner of its curvature, as will be described later, such that the FFC itself is bent to an arc over its length in a side view. In the present embodiment, the warpage of the FFC plays a key role in positioning the FFC between the two printed circuit boards for connecting such two printed circuit boards in series via the FFC.
In the present embodiment, the FFC is formed into a rectangular shape in a plan view thereof, but instead of such rectangular shape, a trapezoidal shape is also applicable to the FFC. In the FFC according to the present disclosure, an electric circuit is provided as a plurality of electrical wiring patterns (arranged in a wiring area) which run in a layer laminated between insulation layers, whereby both ends of the wiring patterns are connected to electric connection terminals of each of the two printed circuit boards for electrically serial connection of the two printed circuit boards installed into, for example, a programmable logic controller (PLC). The film-type circuit can also be realized by an FPC.
In the present embodiment, how the FFC is positioned between the printed circuit boards, then the FFC is moved to fix the positions of the three elements: the first printed circuit board, the FFC, and the second printed circuit board, and finally fixing the positions will be explained.
The present embodiment will now be detailed.
As shown in
In addition, the printed circuit board 20 (see
The FFC 40 (film-type circuit) includes wiring patterns 43, an adhesive layer 42, an insulation layer 41, and a solder layer 45.
First, when the FFC 40 maintains a flat plate shape, the shape of the FFC 40 can be used to define the orientation necessary to explain the structure of the FFC and the electric interconnection of the two printed circuit boards 10 and 20. As shown in
The plurality of electrical wiring patterns 43 are made of an electrically conductive material (e.g., copper) of constant thickness and are linear, but when viewed from the direction along a plane along both the directions SD and LD, the wiring patterns 43 are formed in a layer (see
If explained more specifically, an area left between mutually adjacent two wiring patterns, for example, a narrow-angle area SA in
In detail, the plurality of wiring patterns 43 have predetermined portions at each end in the short direction SD thereof formed as connection parts 43a (see
The electric connection between the printed circuit board 10 and the FFC 40 is generally performed as follows. The position corresponding to the solder layer 15 of the plurality of wiring patterns 13 of the printed circuit board 10 is preheated by the heating tool H1 of a preheater from the opposite side of the solder layer 15 (see
Then, in a similar manner as the foregoing, the solder layer 15 of each wiring pattern 13 of the printed circuit board 20 and the solder layer 45 of the connection part 43a of each wiring pattern 43 of the FFC 40 are aligned with each other. In this aligned state, the FFC 40 is thermo-compressed to printed circuit board 20 by the heating tool H2 of the heater. As a result, the solder layer 15 of each wiring pattern 13 of the printed circuit board 20 and the solder layer 45 of the connection part 43a of each wiring pattern 43 of the FFC 40 are melted and connected with each other.
The first fixing member 91 is formed in a shape corresponding to the printed circuit board 10 and is able to position and fix the printed circuit board 10. For example, the printed circuit board 10 has a plurality of positioning through-holes (not shown). The first fixing member 91 is provided with insertion pins (not shown) each of which can be inserted into a corresponding one of the positioning through-holes of the printed circuit board 10. The insertion pins of the first fixing member 91 are inserted into the multiple positioning through-holes of the printed circuit board 10. This enables the printed circuit board 10 to position and fix to the first fixing member 91. The second fixing member 92 is formed in the same structure as that of the first fixing member 91, and is able to position and fix the printed circuit board 20. The printed circuit board 10 is fixed to the first fixing member 91, while the printed circuit board 20 is fixed to the second fixing member 92. In these fixed states, an edge with the foregoing solder layer 15 on the printed circuit board 10 and an edge with the foregoing solder layer 15 on the printed circuit board 20 are opposed to each other.
As shown in
In the printed circuit board 20, suction holes 26 are formed at a position on the side of printed circuit board 10 rather than the solder layer 15 is, in the connecting direction CD. A vacuum pump (not shown) is connected to the suction holes 26 via air intake tubes. When the vacuum pump is driven, negative pressure is supplied to the suction holes 26 via the air intake tubes.
As shown in
The respective wiring patterns 43 extend linearly in the short direction SD (i.e., the predetermined direction) of both the insulation layer 41 and the FFC 40. The plurality of wiring patterns 43 are aligned in the longitudinal direction LD (orthogonal to the predetermined direction) of both the insulation layer 41 and FFC 40. The through-holes 46 and 47 are formed at the portions of the insulation layer 41 which do not overlap the wiring patterns 43, specifically at both end portions of the insulation layer 41 in the longitudinal direction LD. The through-holes 46, 47 are circularly formed. The diameter of the through-hole 46 is larger than that of the through-hole 47. In other words, as one of preferred examples, the through-holes 46 and 47 are different in size from each other. The respective centers 46a and 47a of the through-holes 46 and 47 are located on the center line C1 of the insulation layer 41 and FFC 40 in the short direction SD. In other words, at least two through-holes are formed at the parts of the insulation layer 41 that does not overlap with the wiring patterns 43. These through-holes pass through the center of the insulation layer 41 in the short direction SD and are separated from each other in the longitudinal direction LD of the insulation layer 41.
The FFC 40 has reinforcing terminals 48 formed of an electrically conductive material (e.g., copper). The reinforcing terminals 48 are formed with a width wider than the width of each of the wiring patterns 43. The reinforcing terminals 48 are located at the four corners (i.e., at both ends of the respective non-wired end areas NL and NR in the longitudinal direction LD and at both ends in the short direction SR) of the surface 40a of the FFC 40, which exists on the connection side (the side where the solder layer 45 is exposed) of the connection part 43a (refer to
As shown in
On the printed circuit boards 10 and 20, connection terminals 18 (i.e., terminal 18 to be connected) are formed by an electrically conductive material (e.g., copper) at positions which positionally corresponds to the reinforcing terminals 48 of the FFC 40, respectively (see
As an alternative example, the connection terminals 18 may also be provided with a solder layer 15.
The cross-sectional structure of the FFC 40 is as shown in
By way of example, the rectangular sizes of the FFC 40 are 36 mm and 43 mm in the short and longitudinal directions SL and DL, and the height HT from a line passing both ends EP to the top TP ranges from a few millimeters to a few centimeters, depending on how deeply the warpage WP is made.
On the other hand, the inventor has noticed that the FFC 40 tends to occur a warpage starting from the through-holes in the insulation layer 41 because the strength of the part where the through-holes are formed is lower than that of other parts. In other words, by adjusting the positions of through-holes formed though the insulation layer 41, the warpage of the FFC 40 (i.e., substantially corresponding to the curvature of the FFC 40) can be controlled with high reproducibility even if the FFC 40 becomes larger. In the present embodiment, the through holes 46 and 47, which are separated from each other in the longitudinal direction LD of the insulation layer 41, are formed to pass through the center of the insulation layer 41 in the short direction SD. This allows the FFC 40 to be warped so that the area including the center in the short direction SD becomes a vertex caused in the FFC 40.
Furthermore, the through-holes 46 and 47 are formed at both ends of the insulation layer 41 in the longitudinal direction LD. As a result, the starting points for the warping of FFC 40 can be set at both ends of the insulation layer 41 in the longitudinal direction LD. This makes it easier to warp the entire FFC 40 so that the range including the center in the short direction SD becomes the apex. In addition, the respective centers 46a and 47a of the through-holes 46 and 47 are positioned in the center of the insulation layer 41 in the short direction SD. This makes it easier to warp the entire FFC 40 so that the center in the short direction SD becomes the apex.
The serial connection of the printed circuit boards 10 and 20 and the FFC 40 is carried out as follows. The following process may be carried out automatically by the equipment or manually by the operator.
First, as shown in
Then, as shown in
In this connection work, as shown in
As described, the FFC 40 is warped such that the central part thereof has a smoothly bent curved apex, i.e., a smoothly curved warp in the short direction SD (left and right directions in
When the ends of the through-holes 46 and 47 reach the tips of the positioning pins 96 and 97, the positioning pins 96 and 97 are inserted, so as to be pulled in, into the through-holes 46 and 47, respectively, as shown in
Then, an area which covers the solder layer 15 of the multiple wiring patterns 13 of the printed circuit board 10 is preheated by the heating tool H1 of the preheater, from the opposite side of the solder layer 15.
Then, with the positioning pins 96 and 97 inserted into the through-holes 46 and 47, a total of four blank portions 48b of the two reinforcing terminals 48 of the FFC 40 facing the printed circuit board 10 are aligned with the four circular portions 18d of the two connection terminals 18 facing the printed circuit board 10, respectively, as shown in
In the same way, a total of four blank portions 48b of the two reinforcing terminals 48 of the FFC 40 facing the printed circuit board 20 are aligned with the four circular portions 18d of the two connection terminals 18 facing the printed circuit board 20, respectively, in the same manner as that shown in
The process of aligning the center of each of the circular portions 18d with the center of corresponding each of the blank portions 48b may be performed automatically based on image recognition with use of imaging devices such as an optical camera, or it may be performed manually by the operator using a magnifying glass or the like. In such an alignment process, the FFC 40 may be moved, the printed circuit boards 10 and 20 (i.e., the fixed portions 91, 92) may be moved, or both the FFC 40 and the printed circuit boards 10, 20 may be moved in combination.
The negative pressure from the suction holes 26 is then used to enable the printed circuit board 20 to suction the FFC 40 thereto. Specifically, a vacuum pump is driven to supply negative pressure to the adsorption holes 26 through the intake tubes.
As shown in
Then, the heating tool H2 of the heater is raised (away from the FFC 40) and moved to the edge of the FFC 40 which faces the printed circuit board 20. Then, in the same manner as the foregoing, the edge of the FFC 40, which faces the printed circuit board 20, is pressed downward (in the direction to the printed circuit board 20) over its entire length. Specifically, the heating tool H2 presses and heats the connection part 43a (i.e., the solder layer 45) and the reinforcing terminals 48 at both ends of the FFC 40 collectively, resulting in thermo-compression being performed between the wiring patterns 13 of the printed circuit board 20 and the solder layer 15 of the connection terminals 18. This thermo-compression melts not only the solder layer 45 of connection part 43a and the reinforcing terminals 48 but also the solder layer 15 of the wiring patterns 13 and the connection terminal 18, thus being connected to each other.
As shown in
The foregoing embodiment provides the following various advantageous operations and effects.
The through-holes 46, 47 are formed through the FFC 40, i.e., specifically in the insulation layer 41 of the FFC 40 that does not overlap with the plurality of electrical wiring patterns 43 (composing the electrical wiring part), and are spaced apart from each other. Therefore, the two printed circuit boards 10 and 20 are fixed to the positioning jig 90 equipped with the positioning pins 96 and 97. In this fixed state, the positioning pins 96, 97 are inserted into the through holes 46, 47 of the insulation layer 41 of the FFC 40, respectively. This allows the FFC 40 to be aligned with both printed circuit boards 10 and 20. Furthermore, by inserting the positioning pins 96 and 97 into the two through holes 46 and 47 which are separated from each other, the rotation of the FFC 40 with respect to both the printed circuit boards 10 and 20 can be restricted. Thus, the connection parts 43a near both ends of the plurality of wiring patterns 43 can be precisely aligned with the wiring patterns 13 of both the printed circuit boards 10 and 20, respectively.
The FFC 40 itself is curved in its length, i.e., warped such that the connection sides of the connection part 43a (the side where the solder layer 45 is provided) are directed inward (i.e., come closer to each other in the short direction SR). The inventor has studied that the parts where the through-holes 46 and 47 are formed in the insulation layer 41 of the FFC 40 are weaker in strength than the other parts, so that the FFC 40 tends to warp easily starting from the through-holes 46 and 47. In other words, by adjusting the positions of the through-holes 46 and 47 in the insulation layer 41, the warpage of the FFC 40 can be controlled with high reproducibility. The two-through holes 46 and 47, which are separated from each other, are passed by the virtual center line in the short direction SR. This geometry allows the FFC 40 to be warped so that the central part in the short direction SR becomes a vertex from which the entire part are gradually rounded. Thus, a force which pushes the FFC 40 and positioning pins 96 and 97 acts in a state where there is some misalignment between the positioning pins 96 and 97 and the through holes 46 and 47 of the insulation layer 41. When this pushing force is applied, the FFC 40 is automatically guided by the warpage so that the positioning pins 96 and 97 approach the central part of the FFC 40 in the short direction SR. Therefore, even when the printed circuit boards 10 and 20 and the FFC 40 are automatically aligned by an assembly device, it is easier for the device to accurately align the FFC40 to both the printed circuit boards 10 and 20.
The positioning of the FFC 40 is based on its warpage, i.e., the flat cable of which whole portion is curved in its length in the short direction SR, so it is possible to assume that the FFC 40 is warped before the positioning. Therefore, an inexpensive FFC 40 with a deeper curve (i.e., warpage), i.e., its curvature radius is larger, which has been difficult to adopt as the FFC in the past, can be used in the present embodiment. In addition, the FFC 40 can also be made larger in size.
The through-holes 46 and 47 are formed at both ends of the longitudinal direction LD (which is orthogonal to the predetermined short direction SD) in the insulation layer 41. According to this configuration, the starting points for producing the warped (curved) FFC 40 can be set at both ends of the FFC 40 in the longitudinal direction LD. This makes it easier to warp or curve the entire FFC40 so that the central part including the center becomes the apex in the short direction SR.
The through-holes 46, 47 are circularly formed. In addition, the centers 46a and 47a of the through holes 46 and 47 are located on the virtually drawn center line C1 passing the insulation layer 41 in the short direction SR. According to such a configuration, it is easier to warp or curve the entire FFC 40 so that the center in the short direction SR becomes the apex.
The reinforcing terminals 48 are made of an electrically conductive material with a width wider than the width of the electrical wiring patterns 43, and are located at both ends in the longitudinal direction LD and both ends in the short direction SD on the FFC 40. Hence, the connection terminals 18 are formed at positions corresponding to the reinforcing terminals 48 of the FFC 40 on each of the printed circuit boards 10 and 20. The connection terminals 18 of each of the printed circuit boards 10 and 20 are thus connected to the reinforcing terminals 48 of the FFC 40. This connection construction can improve the connection strength between the printed circuit board 10 and 20 and the FFC 40.
The through holes 46 are 47 are formed at both end portions, i.e, the non-wired areas NL and NR of the insulation layer 41 (i.e. the FFC 40) in the longitudinal direction LD and between the two reinforcing terminals 48 in the short direction SR. Thus, the through holes 46 and 47 can be formed using the end portions that do not overlap with the reinforcing terminals 48 in both end portions of the insulation layer 41 in the longitudinal direction LD. Therefore, it is possible to suppress the lengthening of the longitudinal direction of the FFC 40, on and through which the reinforcing terminals 48 and through holes 46, 47 are formed. The through-holes 46, 47 formed at both end portions of the insulation layer 41 in the longitudinal direction LD may be different in size from each other. According to this size configuration, when connecting the FFC 40 to each of the two printed circuit boards 10 and 20, it is possible to reduce or avoid errors such as misrecognizing the front and rear surfaces of the FFC 40 or the back and front directions of the FFC 40.
Meanwhile, the positioning jig 90 has the first fixing member 91 that fixes the printed circuit board 10 and the second fixing member 92 that fixes the printed circuit board 20. Each of the positioning pins 96 and 97 is positioned between the first fixing member 91 and the second fixing member 92. To this configuration, there can be applied a method of connecting the printed circuit board 10 and 20 and the FFC 40. The method includes the process of fixing the printed circuit board 10 to the first fixing member 91 and fixing the printed circuit board 20 to the second fixing member 92. According to this process, the FFC 40 can be easily aligned with the printed circuit board 10 fixed to the first fixing member 91 and the printed circuit board 20 fixed to the second fixing member 92.
In the present embodiment, the positioning pins 96 and 97 are first inserted into the through holes 46, 47, and then the center of the blank portions 48b and the center of the circular portion 18d are aligned. Hence, the FFC40 is aligned to both the printed circuit boards 10 and 20 by the positioning pins 96 and 97. The position of the FFC 40 with respect to the printed circuit boards 10 and 20 can then be fine-tuned using the blank portions 48b and the circular portion 18d. The blank portions 48b are included in the reinforcing terminals 48 of the FFC 40. Thus, when the reinforcing terminals 48 are formed on the FFC 40, the blank portions 48b can also be formed together. In addition, the circular portion 18d is included in the connection terminal 18 of each of the printed circuit boards 10 and 20. Thus, when forming the respective connection terminals 18 on the printed circuit boards 10 and 20, the circular portion 18d can be formed together. In addition, the connection terminals 18 of the printed circuit boards 10 and 20 are connected to the reinforcing terminals 48 of the FFC 40. This can enhance a connection strength provided between the printed circuit board 10 and 20 and the FFC 40.
The connection part 43a and the reinforcing terminals 48 of the FFC 40 are pressed together and heated by heater tool H2. As a result, the wiring patterns 13 of the printed circuit boards 10 and 20 are connected to the connection sides of the connection parts 43a of the FFC 40, and at the same time, the connection terminals 18 of the printed circuit boards 10 and 20 are connected to the reinforcing terminals 48 of the FFC 40. Thus, the connection between the printed circuit boards 10 and 20 and the FFC 40 can be executed efficiently. Furthe, the through holes 46 and 47 are formed through the insulation layer 41 in its portions that do not overlap with the plurality of wiring patterns 43. Therefore, even if the heat from the heater tool H2 is transferred along the plurality of wiring patterns 43, the through holes 46 and 47 can be suppressed from being deformed by the heat. Therefore, when the wiring patterns 13 of the printed circuit board 10 and the connection sides of connection parts 43a of the FFC40 are connected by the heater tool H2, it is possible to prevent the FFC40 from positionally shifting with respect to the printed circuit board 20 on the opposite side of the heater tool H2.
The foregoing embodiment may be implemented with the following modifications. The same elements or structures as those described in the foregoing embodiment will be referred to by the same reference numerals or symbols.
The blank portions 48b (i.e., the first positioning marks) and circular portions 18d (i.e., the second positioning marks) can be omitted in the configurations described in the first embodiment.
The heating tool H2 may be separated into a heating tool that presses all the connection parts 43a (i.e., the solder layer 45) of the FFC 40 and a heating tool that presses the respective reinforcing terminals 48. The timing of pressing all the connection part 43a (i.e., the solder layer 45) and the timing of pressing the respective reinforcing terminals 48 may be different from each other.
In the foregoing embodiment and modifications, the reinforcing terminals 48 and connection terminals 18 can be omitted.
In the foregoing embodiment and modifications, instead of employing the solder layers 15 and 45, anisotropic conductive films (ACF: Anisotropic Conductive Film) can be employed to establish mutual connection between the printed circuit boards 10 and 20 and the FFC 40.
In the foregoing embodiment and modifications, the through-holes 46 and 47 may be shaped to be the same size. The through-holes 46 and 47 are not limited to a circular shape, but may be oval, square, rectangular, triangular, or other polygonal shapes. Even in these various other shapes, the cross-sectional lateral shape of the positioning pins 96 and 97 should be matched to the shape of the through holes 46 and 47.
Another modification is provided in
Alternatively, the through-hole 47 may additionally be formed at a non-wired end area NR of the insulation layer 41 in the longitudinal direction LD, resulting in that the through-hole 46 and the two through-holes 47 may be formed through the insulation layer 41. In other words, at least two through-holes that pass through the center in the short direction SR (corresponding to the predetermined direction) and are separated from each other should be formed in parts of the insulation layer 41 that does not overlap with the wiring patterns 43 arranged in the wiring area PA.
Another modification is provided in
The center points 46a and 47a of the through-holes 46 and 47 may not always be located on the center line C1 vertically set in the short direction DT. For example, as shown in
Even in the case of the configuration shown in
Therefore, in order to provide the insulation layer 41 with a properly curvature for a reliable and smooth positioning guidance thereof, it is sufficient that at least two through-holes are formed in the insulation layer 41, which intersect with the center line C1 in the short direction SR and are separated from each other.
In this way, the foregoing exemplified embodiments basically feature that, when the film-type circuit is loaded between two printed circuit boards for mutual electrical connection, the film-type circuit is given a curved shape in its length, i.e., a warpage in advance. How the warpage (or the curved surface in a side view) is generated positionally and in size can be controlled by adjustably adding through-holes to the film-type circuit. Hene, by using an inexpensive film-type circuit and positively utilizing the warpage (curve) generated on such an inexpensive film-type circuit, it is possible to improve yield and reduce costs during manufacturing.
Alternatively to the FFC employed in the foregoing embodiments modifications, a FPC (Flexible Printed Circuit) can be used as a film-type circuit instead of the FFC. In this case, an electric circuit (wiring patterns) should be formed by electrically conductive materials such as copper foil on a thin, soft, insulating base film made of insulating materials including polyimide. Even in this configuration, warpage may occur in the FPC due to the fact that there is an asymmetry in the components layered in the thickness direction of the FPC (film-type circuit).
In this modification, the base film (i.e., the insulation part) may cover both sides of an electrical circuit or only one side of the electrical circuit in order to expose the connection part of the electrical circuit.
The printed circuit boards 10 and 20 and film-type circuits (the foregoing FFC 40, an FPC, or other flexible connecting circuits) may be mounted on devices other than PLCs. In short, the film-type circuits of the foregoing embodiment and its modified examples can be applied to any film-type circuit that connects the wires of two printed circuit boards, regardless of the types of devices in which the circuits are mounted.
The plan-viewed shape of the FFC or FPC is not limited to a rectangle shape as described in the foregoing embodiment. In place of such rectangular FFC and FPC shown in for example
The foregoing embodiment and its modifications may be combined to the extent possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-184004 | Oct 2023 | JP | national |
