JP2006324605A - Flexible printed wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a relative position between a land and an application region of solder from being shifted, and to prevent a land area from being changed, even if a bonding position of a coverlay shifts. <P>SOLUTION: In a flexible printed wiring board 1 to which a coverlay 3 is bonded while a land 4 is formed, the land 4 is composed of a principal plane 7 on which cream solder is printed and an enlargement 8 whose width is formed to be narrower than the width of the principal plane 7. With respect to the coverlay 3, there is formed an opening 9 for outwardly turning each of the principal planes 7 and the enlargement 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flexible printed wiring board on which an electronic component or an electronic circuit component is mounted, and more particularly to a flexible printed wiring board having a coverlay for protecting a conductor pattern and a method for manufacturing the flexible printed wiring board.

  Conventionally, in a flexible printed wiring board, a conductor pattern is formed on a plastic film having flexibility and insulation, such as polyimide and polyester, using a printing technique, and then a coverlay is used to protect the conductor pattern. It is stuck. The cover lay is formed with an opening that allows the electronic component connecting land to face outward. After the solder is printed on the land facing outward from the opening, the electrode terminal of the electronic component is mounted and reflow soldering is performed.

  Specifically, in the flexible printed wiring board 100, as shown in FIG. 4, in order to prevent the land 101 from being peeled off, the upper and lower end portions 101a and 101b of the land 101 are stuck on the coverlay 102 by about 0.2 mm, for example. I wear it. Further, in the flexible printed wiring board 110, as shown in FIG. 5, the wiring pattern 112 is connected to the upper and lower end portions 111a and 111b of the land 111 in order to prevent the land 111 from being peeled off. About 0.2 to 0.3 mm is exposed and covered by the coverlay 113.

  However, in the flexible printed wiring board 100 shown in FIG. 4, since the position of the land 101 to which the solder is applied is shifted when the cover lay 102 is stuck, the outer shape of the plastic film or the reference formed on the plastic film is changed. The land 101 is displaced from the hole. For this reason, since the relative position between the land 101 and the cream solder application region is also shifted, a printing shift occurs, and a soldering failure is induced. In addition, since the land 101 and the cream solder application area are shifted, the mounting position of the electronic component also shifts.

  Further, in the flexible printed wiring board 110 shown in FIG. 5, the land 111 connected to the wiring pattern 112 does not cause a problem of land peeling, but the land 114 that is not connected to the wiring pattern easily causes land peeling. . Further, since the wiring pattern 115 is formed with substantially the same width in the land 116, the wiring pattern 115 not covered by the cover lay 113 performs the same function as the land, so that the land area is substantially enlarged, The amount of solder applied to the land is reduced, causing poor soldering. Further, if the sticking displacement of the cover lay 113 occurs, similarly to the flexible printed wiring board 100 shown in FIG. 4, the relative positions of the lands 111, 114, and 116 and the solder application region shift, and the solder printing misalignment and electronic This will cause a shift in the mounting position of the component.

JP 2002-368349 A

  Therefore, the present invention provides a flexible printed wiring board and a flexible printed wiring that can prevent relative positional deviation between the land and the solder application region and increase / decrease in the land area even when the coverlay attaching position is shifted. It aims at providing the manufacturing method of a board.

  In order to solve the above-described problems, a flexible printed wiring board according to the present invention has a land on which a main surface portion on which cream solder is printed in the flexible printed wiring board on which a coverlay is attached. And an extended portion formed narrower than the main surface portion, and the cover lay is formed with an opening that faces a part of the main surface portion and the extended portion outward. It is what.

  In addition, the method for manufacturing a flexible printed wiring board according to the present invention includes a step of forming a land including a main surface portion on which cream solder is printed and an extending portion formed narrower than the main surface portion, and the extension And a step of attaching a cover lay in which an opening for facing the base end of the main surface portion and the extension portion on the main surface portion side is formed. .

  According to such a flexible printed wiring board and a method for manufacturing the flexible printed wiring board, the length of the extended portion exposed from the opening functions as a margin for the coverlay sticking misalignment, so that the cream solder is printed. The main surface is not covered by the coverlay. Therefore, it is possible to prevent a variation in the area of the main surface portion and a shift between the printing position of the cream solder and the mounting position of the electrode terminal of the surface mount component.

  Hereinafter, a flexible printed wiring board to which the present invention is applied and a method for manufacturing the flexible printed wiring board will be described in detail with reference to the drawings. A flexible printed wiring board 1 to which the present invention is applied is obtained by forming a conductor pattern 2 on a plastic film having flexibility and insulation, such as polyimide and polyester, using a printing technique. In order to protect 2, a coverlay 3 is attached.

  As shown in FIG. 1, the conductor pattern 2 is formed with a footprint 4 serving as a land for mounting electronic components for constituting a circuit, and a wiring pattern 5 connected to the footprint 4. . Footprint 4 is printed with cream solder, and then lead terminals of surface mount components such as QFP (Quad Flat Package) and SOP (Small Outline Package) are positioned and mounted by soldering in a reflow process. Electrical connection with the wiring pattern 5 formed on the flexible printed wiring board 1 is performed.

  As shown in FIG. 1, a plurality of footprints 4 on which such surface mount component lead terminals are mounted are arranged in accordance with the lead terminals. Each footprint 4 includes a substantially rectangular main surface portion 7 on which cream solder is printed and lead terminals are mounted, and an extending portion 8 extending from both ends of the main surface portion 7 in the longitudinal direction.

  The extending portion 8 is extended from substantially the middle of the side surface which is both ends in the longitudinal direction of the main surface portion 7, and ends without being connected to the pattern formed on the surface of the wiring board according to the circuit pattern, or the tip The wiring pattern 5 is connected at the part. The extended portion 8 is formed narrower than the main surface portion 7. When the width of the main surface portion 7 is 1.0 mm or more, the extended portion 8 is formed with a width of about 40% to 70% of the width of the main surface portion 7. When the width of the main surface portion 7 is less than 1.0 mm, the main surface portion 7 is formed with a width of about 20% to 40% of the width of the main surface portion 7.

  The wiring pattern 5 connected at the tip of the extended portion 8 is formed with a width that is substantially the same as or slightly larger than the width of the extended portion 8.

  The flexible printed wiring board 1 has a coverlay 3 attached to protect the wiring pattern 5 and expose the footprint 4 to the outside. As shown in FIG. 1, the cover lay 3 has an opening 9 that exposes the footprint 4 to the outside. The opening 9 can expose a part of the main surface portion 7 of the footprint 4 and the main surface portion 7 side of the extended portion 8 to the outside by attaching the coverlay 3 to the flexible printed wiring board 1. It has a size. That is, the extended portion 8 is exposed at the base end portion on the main surface portion 7 side from the opening 9 by the cover lay 3 and is connected to the wiring pattern 5 or to a pattern formed on the surface of the wiring board. The tip which is terminated without being covered is covered. For example, the extended portion 8 is exposed from the opening 9 by approximately 0.15 mm to 0.3 mm at the base end portion by being covered with the cover lay 3.

  The flexible printed wiring board 1 as described above includes a footprint 4 including a main surface portion 7 and an extending portion 8 formed narrower than the main surface portion 7, and a part of the main surface portion 7 and the extending portion 8. By attaching the cover lay 3 so as to expose the cover lay 3, even when the cover lay 3 is misaligned, the relative displacement between the main surface portion 7 and the cream solder application region, and the increase or decrease in the area of the main surface portion 7. Can be prevented.

  That is, as shown in FIG. 2, even when the cover lay 3 is misaligned, the base end of the extended portion 8 that extends from both side surfaces of the main surface portion 7 and is exposed from the opening 9 of the cover lay 3. Since the length of the portion becomes a margin of misalignment, the cover lay 3 does not cover the main surface portion 7. Accordingly, since the main surface portion 7 of the footprint 4 is reliably exposed to the outside through the opening 9 of the cover lay 3, the main surface portion 7 can be removed from the outer shape of the flexible printed wiring board 1 and the reference holes formed in the flexible printed wiring board 1. The position up to the surface portion 7 does not shift. Accordingly, the relative displacement between the main surface portion 7 and the cream solder application region does not occur, and the cream solder can be printed on the main surface portion 7. In addition, since the solder paste can be printed on the main surface portion 7 without any misalignment between the main surface portion 7 and the cream solder printing region, the lead terminals of the surface mount component can be reliably soldered (FIG. 3). .

  Moreover, since the extended part 8 is formed narrower than the main surface part 7, the flexible printed wiring board 1 does not fulfill the same function as the main surface part 7, and suppresses the area change of the main surface part 7. Can do. Therefore, the application amount of the cream solder with respect to the area of the main surface portion 7 does not decrease, and the generation of an unsoldered area and insufficient printed thickness of the solder are not caused.

  Furthermore, by forming the extending portion 8 narrower than the main surface portion 7, the cream solder can be reliably collected on the main surface portion 7, and the cream solder can be printed thickly. Therefore, even if slight floating occurs in the lead terminals of the surface mount component, the soldering can be reliably performed.

  In addition, the footprint 4 is connected to the wiring pattern 5 because the front end side of the extended portion 8 is covered by the cover lay 3 regardless of whether the cover lay 3 is attached or not. Even when it is terminated, it does not peel off. Further, the footprint 4 does not need to be connected to the wiring pattern 5 for preventing peeling.

  The flexible printed wiring board 1 as described above is formed by etching the copper foil adhered to a plastic film having flexibility and insulation, such as polyimide and polyester, so that the footprint 4 and the wiring pattern 5 are formed. After the formation, the coverlay 3 is formed by bonding.

  At this time, the flexible printed wiring board 1 is composed of the main surface portion 7 and the extending portion 8 formed narrower than the main surface portion 7, and the opening 9 of the cover lay 3 includes the main surface portion 7 and the main surface portion 7. Since the opening 9 having a size that exposes the base end portion of the extending portion 8 by a predetermined amount is provided, the length of the extending portion 8 exposed from the opening 9 serves as a margin for the sticking deviation of the cover lay 3. Since it functions, the main surface portion 7 on which the cream solder is printed is not covered by the cover lay 3. Accordingly, it is possible to prevent a variation in the area of the main surface portion 7 and a shift between the printing position of the cream solder and the mounting position of the electrode terminal of the surface mount component.

  In addition, the footprint 4 is connected to the wiring pattern 5 because the front end side of the extended portion 8 is covered by the cover lay 3 regardless of whether the cover lay 3 is attached or not. Even when it is terminated, it does not peel off. Further, the footprint 4 does not need to be connected to the wiring pattern 5 for preventing peeling.

  As described above, the size of the opening 9 is set so that the extended portion 8 is exposed to about 0.15 mm to 0.3 mm as a margin for the misalignment of the cover lay 3. The exposed length of the part 8 can be appropriately changed according to the sticking accuracy of the coverlay 3.

  After the cover lay 3 is adhered, cream solder is supplied onto the main surface portion 7 of the footprint 4 by a known method such as screen printing or a dispensing method. At this time, since the area of the main surface portion 7 of the footprint 4 does not vary even when the coverlay 3 is stuck, cream solder can be printed as necessary and sufficiently. Further, since the extended portion 8 is formed narrower than the main surface portion 7 in the footprint 4, the cream solder does not flow into the extended portion 8, and the cream solder is concentrated on the main surface portion 7, and Cream solder can be printed thickly. Therefore, even if slight floating occurs in the lead terminals of the surface mount component, the soldering can be reliably performed.

  Next, the electrode terminals of the surface mount components are mounted on the footprint 4 on which the cream solder is printed, and soldered by a reflow process. Also at this time, since the positional deviation between the main surface portion 7 of the footprint 4 and the printing position of the cream solder does not occur, it is possible to reliably mount the electrode terminals of the surface mount component on the main surface portion 7 on which the cream solder is printed. It is possible to improve the mounting accuracy of electronic components.

It is a top view which shows the flexible printed wiring board to which this invention was applied. It is a top view which shows the flexible printed wiring board in which the sticking shift | offset | difference of coverlay occurred. It is a side view which shows the footprint in which the lead terminal of surface mount components was mounted. It is a top view which shows the footprint of the conventional flexible printed wiring board. It is a top view which shows the footprint of the conventional flexible printed wiring board.

Explanation of symbols

1 Flexible Printed Wiring Plate, 2 Conductor Pattern, 3 Coverlay, 4 Footprint, 5 Wiring Pattern, 7 Main Surface, 8 Extension, 9 Opening

Claims (7)

In the flexible printed wiring board where the land is formed and the coverlay is attached,
The land is composed of a main surface portion on which cream solder is printed and an extending portion formed narrower than the main surface portion.
The coverlay is formed with an opening that allows a part of the main surface portion and the extended portion to face outward.
A flexible printed wiring board characterized by that.   The flexible printed wiring board according to claim 1, wherein the extending portion is drawn from both end portions in the longitudinal direction of the main surface portion.   The flexible printed wiring board according to claim 1, wherein the extended portion extends to a region below the area covered by the cover lay.   4. The flexible printed wiring according to claim 3, wherein the extended portion is connected to a wiring pattern formed to have substantially the same width as the extended portion under the region covered with the cover lay. Board. Forming a land comprising a main surface portion on which cream solder is printed and an extending portion formed narrower than the main surface portion;
A step of covering a distal end portion of the extending portion, and affixing a cover lay in which an opening portion is formed to face the main surface portion and the base end portion of the extending portion on the main surface portion side; and
The manufacturing method of the flexible printed wiring board which has this.   6. The method of manufacturing a flexible printed wiring board according to claim 5, wherein the extended portion is drawn out from both end portions in the longitudinal direction of the main surface portion. 8. The flexible printed wiring according to claim 7, wherein the extended portion is connected to a wiring pattern formed to have substantially the same width as the extended portion under a region covered with the cover lay. A manufacturing method of a board.

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