JP7294769B2 - Manufacturing method, inspection method and inspection apparatus for flexible printed wiring board - Google Patents

Description

The present invention relates to a manufacturing method, an inspection method, and an inspection apparatus for flexible printed wiring boards.

2. Description of the Related Art In hard disk drives, it is known that electronic components such as a head IC are mounted on a flexible printed wiring board (hereinafter sometimes simply referred to as FPC) (see, for example, Patent Document 1). The electronic components described above may generate heat at high temperatures, and therefore the FPC is required to have heat resistance.

Therefore, for example, in order to evaluate the heat resistance of an FPC, a method of immersing the FPC in a high-temperature oil bath and then evaluating the FPC has been proposed (see, for example, Non-Patent Document 1). Also, a method has been proposed in which an FPC is put into a heating furnace, then the set temperature of the heating furnace is increased stepwise, and then the FPC is evaluated (see, for example, Non-Patent Document 2).

JP 2015-108819 A IPC-TM-650 TEST METHODS MANUAL Number2.6.7, Date 8/97 IPC-TM-650 TEST METHODS MANUAL Number2.6.6, Date 4/73

However, electronic components are mounted only on one side of the FPC in the thickness direction. On the other hand, the environments tested in Non-Patent Documents 1 and 2 are heated from both one side and the other side in the thickness direction of the FPC. Therefore, the environment around the FPC in a hard disk drive is different. As a result, there is a problem that the heat resistance of the FPC cannot be evaluated accurately.

The present invention provides an FPC manufacturing method, an inspection method, and an inspection apparatus capable of accurately evaluating the heat resistance of an FPC in accordance with the environment in which electronic components are mounted.

The present invention (1) comprises an insulating layer having a through hole penetrating in the thickness direction, a first conductor layer arranged on one side of the insulating layer in the thickness direction, and a conductor layer arranged on the other side of the insulating layer in the thickness direction. a first step of preparing a flexible printed wiring board including a second conductor layer disposed within the through hole and electrically conducting the first conductor layer and the second conductor layer; and a second step of evaluating the electrical characteristics of the flexible printed wiring board by bringing a body into contact with the first conductor layer only from one side in the thickness direction of the flexible printed wiring board. including methods.

According to this manufacturing method, in the second step, the heating element is brought into contact with the first conductor layer only from one side in the thickness direction of the flexible printed wiring board to evaluate the electrical characteristics of the flexible printed wiring board. The heat resistance of the flexible printed wiring board can be evaluated in an environment that is the same as or similar to the environment in which electronic components that generate heat are mounted on the wiring board. Therefore, it is possible to accurately evaluate the heat resistance of the flexible printed wiring board. As a result, it is possible to manufacture a flexible printed wiring board whose heat resistance is accurately evaluated.

In the present invention (2), in the first step, the flexible printed wiring board including the first conductor layer having a flat first contact surface along a direction orthogonal to the thickness direction is prepared, and the second The step includes the method of manufacturing a flexible printed wiring board according to (1), wherein the second contact surface of the heating element having a flat second contact surface is brought into surface contact with the first contact surface.

According to this manufacturing method, in the second step, the second contact surface of the heating element having the flat second contact surface is brought into surface contact with the first contact surface. The same can be done, and the heat resistance of the flexible printed wiring board can be evaluated more accurately.

The present invention (3) is the flexible printed wiring board according to (2), wherein in the first step, the conductive portion is arranged so as to be included in the first contact surface when projected in the thickness direction. including the manufacturing method of

According to this manufacturing method, in the first step, the conductive portion is arranged so as to be included in the first contact surface when projected in the thickness direction, so that heat from the heater is transferred through the first conductor layer. It can be made to conduct to the conduction part rapidly. Therefore, it is possible to accurately evaluate the heat resistance of the flexible printed wiring board. As a result, it is possible to manufacture a flexible printed wiring board whose heat resistance is accurately evaluated.

The present invention (4) includes the method for manufacturing a flexible printed wiring board according to any one of (1) to (3), wherein a plurality of conductive portions are arranged in the first step.

According to this manufacturing method, since a plurality of conductive portions are arranged in the first step, the electrical characteristics of the flexible printed wiring board can be evaluated more accurately by evaluating the electrical characteristics of the plurality of conductive portions in the second step. be able to.

In the present invention (5), in the first step, a flexible printed wiring board assembly including a plurality of the flexible printed wiring boards is prepared, and the plurality of flexible printed wiring boards are a product flexible printed wiring board to be a product; and a test flexible printed wiring board, and in the second step, the heating body is brought into contact with the first conductor layer of the test flexible printed wiring board, according to any one of (1) to (4). including a method for manufacturing a flexible printed wiring board.

According to this manufacturing method, in the second step, the heating element is brought into contact with the first conductor layer of the test flexible printed wiring board, so that the product flexible printed wiring board can be prevented from being damaged by heat.

The present invention (6) includes the method for producing a flexible printed wiring board according to any one of (1) to (5), wherein changes in electrical resistance of the flexible printed wiring board are continuously measured.

According to the methods of Non-Patent Documents 1 and 2, the flexible printed wiring board is evaluated after being heated in an oil bath and a heating furnace and then taken out.

On the other hand, according to this manufacturing method, the change in electrical resistance of the flexible printed wiring board is continuously measured while the flexible printed wiring board is being heated. It is possible to accurately evaluate the heat resistance of printed wiring boards.

In the present invention (7), the second step includes at least one of a heating step of heating the heating body, a maintaining step of maintaining the temperature of the heating body, and a cooling step of cooling the heating body. The method for manufacturing a flexible printed wiring board according to any one of (1) to (6), comprising:

In this manufacturing method, the second step includes at least one of the heating step of heating the heating element, the maintaining step of maintaining the temperature of the heating element, and the cooling step of cooling the heating element. The second step can be set and performed according to the environment around the flexible printed wiring board.

The present invention (8) includes the method for manufacturing a flexible printed wiring board according to (7), wherein the second step includes the heating step, and the heating steps are set to different temperatures.

In the heating process of this manufacturing method, the temperatures of the heaters are set to different temperatures, so that the heating process can be carried out in accordance with the actual surrounding environment of the flexible printed wiring board.

The present invention (9) comprises an insulating layer having a through hole penetrating in the thickness direction, a first conductor layer arranged on one side of the insulating layer in the thickness direction, and arranged on the other side of the insulating layer in the thickness direction. a first step of preparing the flexible printed wiring board including a second conductor layer disposed in the through hole and a conductive portion electrically conducting the first conductor layer and the second conductor layer; and a second step of contacting a heating element with the first conductor layer only from one side in the thickness direction of the flexible printed wiring board to evaluate the electrical characteristics of the flexible printed wiring board. Including inspection method.

In this flexible printed wiring board inspection method, in the second step, the heating element is brought into contact with the first conductor layer only from one side in the thickness direction of the flexible printed wiring board to evaluate the electrical characteristics of the flexible printed wiring board. , the heat resistance of the flexible printed wiring board can be evaluated in an environment that is the same as or similar to the environment in which the flexible printed wiring board is mounted. Therefore, the heat resistance of the flexible printed wiring board can be accurately evaluated in accordance with the environment in which electronic components are mounted.

The present invention (10) is a flexible printed wiring board inspection apparatus used in the flexible printed wiring board inspection method according to (9), wherein the heating body and an evaluation for evaluating electrical characteristics of the flexible printed wiring board and an inspection apparatus for flexible printed wiring boards.

This inspection apparatus for flexible printed wiring boards can accurately evaluate the heat resistance of flexible printed wiring boards in accordance with the environment in which electronic components are mounted.

The present invention (11) includes the flexible printed wiring board inspection apparatus according to (10), wherein the heater has a flat contact surface.

In this inspection apparatus for flexible printed wiring boards, since the heating element has a flat contact surface, the heating element can be brought into surface contact with the first conductor layer. Therefore, the flexible printed wiring board can be made to have the same environment as that in which electronic components are mounted on a plane, and the heat resistance of the flexible printed wiring board can be evaluated more accurately.

The present invention (12) includes the flexible printed wiring board inspection apparatus according to (10) or (11), wherein the heater can be continuously heated and cooled.

Since the heating element can be continuously heated and cooled, the flexible printed wiring board is provided with a heat history suitable for the environment in which electronic components are mounted, thereby improving the heat resistance of the flexible printed wiring board. can be evaluated accurately.

The present invention (13) is according to any one of (10) to (12), wherein the evaluation device is a resistance measuring instrument capable of continuously measuring changes in electrical resistance of the flexible printed wiring board. It includes an inspection apparatus for flexible printed wiring boards as described.

According to this inspection device, since the resistance measuring device continuously measures changes in the electrical resistance of the flexible printed wiring board, the heat resistance of the flexible printed wiring board can be measured in accordance with the heat history actually received by the flexible printed wiring board. can be accurately evaluated.

According to the method for manufacturing a flexible printed wiring board of the present invention, a flexible printed wiring board whose heat resistance has been accurately evaluated can be manufactured.

According to the inspection method and inspection apparatus of the present invention, the heat resistance of a flexible printed wiring board can be accurately evaluated in accordance with the environment in which electronic components are mounted.

FIG. 1 shows a plan view of an FPC assembly used in one embodiment of the manufacturing method of the present invention. 2A to 2C show test FPCs provided in the FPC assembly shown in FIG. 1, FIG. 2A being a plan view, FIG. 4 shows a plan view of the second conductor layer and the conducting portion, with the first conductor layer and the insulating layer omitted; FIG. FIG. 3 shows a cross-sectional view taken along line XX of the test FPC shown in FIGS. 2A-2C. 4A to 4C are manufacturing process diagrams of the test FPC shown in FIG. , forming insulating through-holes and conductor through-holes, and FIG. 4C shows forming a fourth conductor layer. FIG. 5 shows a diagram explaining the second step using the test FPC shown in FIG. 6A to 6E are temperature programs of the heating element in the second step, where FIG. 6A is the first program, FIG. 6B is the second program, FIG. 6C is the third program, and FIG. 6D is the second program. A fourth program, FIG. 6E, which is a variation of , shows a fifth program that repeats the first program. 7A to 7C show a modification of the test FPC, FIG. 7A is a plan view, FIG. 7B is a plan view of the first conductor layer, the conductive portion and the insulating layer, and FIG. 7C omits the first conductor layer. FIG. 10 is a plan view of the second conductor layer and the conducting portion, respectively. 8A to 8C show a modification of the test FPC, FIG. 8A is a plan view, FIG. 8B is a plan view of the first conductor layer, the conductive portion and the insulating layer, and FIG. 8C omits the first conductor layer. FIG. 10 is a plan view of the second conductor layer and the conducting portion, respectively. 9A to 9C show a modified example of the test FPC, FIG. 9A is a plan view, FIG. 9B is a plan view of the first conductor layer, the conductive part and the insulating layer, and FIG. 9C omits the first conductor layer. , a plan view of the second conductor layer and the conducting portion; FIG.

In FIGS. 3 to 5, the vertical direction of the paper is the vertical direction as an example of the thickness direction, the upper side of the paper is the upper side (an example of one side in the thickness direction), and the lower side of the paper is the lower side (an example of the other side in the thickness direction). An example. In FIGS. 3 to 5, the horizontal direction of the paper surface is the surface direction (longitudinal direction), which is an example of a direction orthogonal to the thickness direction.

Specifically, the directions conform to the directional arrows described in each drawing.

These orientation definitions are not intended to limit the orientation of the test FPC 2 and FPC assembly 1 (described later) during manufacture, inspection and use.

As shown in FIG. 1, one embodiment of the method for manufacturing an FPC of the present invention is a method for manufacturing an FPC assembly 1. As shown in FIG. The manufacturing method of the FPC assembly 1 includes a first step of preparing the FPC assembly 1 and a second step of evaluating electrical characteristics of a test FPC 2 (described later) included in the FPC assembly 1 .

The FPC aggregate 1 is, for example, a sheet obtained by cutting a long sheet 3 along its width direction, which is manufactured by being drawn out along the conveying direction by a roll-to-roll method. The FPC assembly 1 has a substantially rectangular sheet shape elongated in the width direction of the long sheet 3 in plan view. The FPC aggregate 1 comprises a product FPC 4 and a test FPC 2.

A plurality of product FPCs 4 are arranged at intervals in the FPC assembly 1 . Each of the plurality of product FPCs 4 has conductive portions 14, first conductor layers 15, and second conductor layers 16 (described later) provided on the test FPC 2 in appropriate patterns.

A plurality (two) of test FPCs 2 are arranged outside the plurality of product FPCs 4 .

Next, one test FPC2 of the two test FPC2 will be described. The other test FPC2 has the same configuration as the one test FPC2.

As shown in FIGS. 2A-3, the test FPC 2 has a substantially sheet shape extending in the longitudinal direction. The longitudinal direction of the test FPC 2 corresponds to the longitudinal direction of the long sheet 3 (see FIG. 1). The test FPC 2 comprises an insulating layer 5 and conductor patterns 6 .

The insulating layer 5 has a sheet shape extending in the longitudinal direction. The insulating layer 5 has an insulating upper surface 9 and an insulating lower surface 10 which are parallel to each other. Each of the insulating top surface 9 and the insulating bottom surface 10 is planar. In addition, as shown in the enlarged view of FIG. 3, the insulating layer 5 has an insulating through hole 7 as an example of a through hole penetrating in the thickness direction. A plurality of insulating through-holes 7 are arranged at intervals in the plane direction (longitudinal direction and width direction). Each of the plurality of insulating through-holes 7 has, for example, a generally circular shape in plan view. An insulating inner side surface 8 of the insulating layer 5 facing the plurality of insulating through-holes 7 is a tapered surface that slopes downward and outward in the plane direction. In other words, the insulating inner side surface 8 corresponds to a truncated conical slope (conical surface) in which the cross-sectional area of the opening gradually increases toward the lower side.

As a material of the insulating layer 5, for example, a resin that is durable and flexible in the second step described later can be used. Specifically, examples of materials for the insulating layer 5 include polyimide resin, polyamideimide resin, acrylic resin, polyether resin, nitrile resin, polyethersulfone resin, polyethylene terephthalate resin, polyethylene naphthalate resin, and polychloride. Synthetic resins such as vinyl resins, preferably polyimide resins. The thickness of the insulating layer 5 is, for example, 1 μm or more, preferably 3 μm or more, and for example, 25 μm or less, preferably 15 μm or less. The inner diameter (minimum diameter, minimum value of the distance between the opposing insulating inner surfaces 8) of the insulating through hole 7 is, for example, 10 μm or more, preferably 50 μm or more, and for example, 2000 μm or less, preferably 1500 μm or less. is. The pitch of the plurality of insulating through-holes 7 (the sum of the inner diameter of the insulating through-holes 7 and the distance between adjacent insulating through-holes 7) is, for example, 100 μm or more, preferably 150 μm or more, and, for example, 500 μm or less. , preferably 300 μm or less.

As shown in FIG. 2A, the conductor pattern 6 integrally includes a pattern to be inspected 11, a terminal portion 12, and a connecting portion 13. As shown in FIG.

The pattern to be inspected 11 is arranged substantially in the longitudinal center of the test FPC 2 . The pattern 11 to be inspected has a substantially meandering shape (a zigzag shape or a serpentine shape) in plan view. As a result, the pattern to be inspected 11 forms a meandering conductive path P in plan view, as indicated by the thick line in FIG. 2A. As shown in FIG. 3, the pattern to be inspected 11, which will be described later, is also a meandering pattern that alternately progresses on the insulating upper surface 9 and the insulating lower surface 10 of the insulating layer 5 when viewed in cross section.

As shown in FIGS. 2A and 2B, a plurality (four) of terminal portions 12 are arranged on both sides of the pattern to be inspected 11 in the longitudinal direction at intervals.

The connecting portion 13 has, for example, a substantially linear shape in plan view, and connects the pattern to be inspected 11 and the terminal portion 12 .

Moreover, as shown in FIGS. 2A to 3, the conductor pattern 6 includes a conducting portion 14, a first conductor layer 15, and a second conductor layer 16. FIG.

A plurality of conductive portions 14 are provided corresponding to the plurality of insulating through holes 7 . Specifically, a plurality of (30) conductive portions 14 are arranged at intervals along the meandering pattern of the pattern to be inspected 11 . Each of the plurality of conducting portions 14 is filled in each of the plurality of insulating through holes 7 . Specifically, the conducting portion 14 overlaps the insulating layer 5 when projected in the planar direction, and more specifically, is located between the insulating upper surface 9 and the insulating lower surface 10 . The conductive portion 14 includes an insulating inner surface 8, a lower surface of a first conductor layer 15 (described later) positioned above the insulating through hole 7, and a second conductor layer 16 positioned below the insulating through hole 7 (described later). is in contact with the top surface of the Thereby, the conducting portion 15 electrically conducts the first conductor layer 15 (described later) and the second conductor layer 16 (described later).

Examples of the material of the conducting portion 14 include conductors such as copper, nickel, gold, or alloys thereof, preferably copper. The thickness of the conducting portion 14 is the same as the thickness of the insulating layer 5 .

The first conductor layer 15 is arranged on the insulating upper surface 9 of the insulating layer 5 and has a pattern (it is a patterned sheet) that closes the upper edges of the insulating through-holes 7 . The first conductor layer 15 is arranged above the insulating upper surface 9 . The first conductor layer 15 has a first conductor upper surface 26 and a first conductor lower surface 27 parallel to each other. The first conductor upper surface 26 and the first conductor lower surface 27 are flat. The first conductor upper surface 26 is exposed upward. The first conductor lower surface 27 is in contact with the insulating upper surface 9 and the upper surface of the conductive portion 14 .

Also, the first conductor layer 15 forms a pattern to be inspected 11 , a terminal portion 12 and a connecting portion 13 .

The pattern to be inspected 11 is formed of the conductive portion 14, the first conductor layer 15, and the second conductor layer 16 (described later).

The first conductor layer 15 forming the pattern to be inspected 11 includes a plurality of first connecting patterns 17 including two conductive portions 14 adjacent along the conductive path P of the pattern to be inspected 11, It independently has two isolated patterns 18 each including a conductive portion 14 . Each first connection pattern 17 includes two conductive portions 14 adjacent along the conductive path P, but is arranged so as not to include the two conductive portions 14 and the conductive portion 14 adjacent along the conductive path P. ing. Therefore, adjacent first connection patterns 17 are independent of each other. Also, the first conductor layer 15 is in surface contact with all upper surfaces of the plurality of conductive portions 14 .

The first conductor upper surface 26 in the pattern to be inspected 11 is an example of a first contact surface. In other words, the first conductor upper surface 26 in the pattern to be inspected 11 forms the upper surface of each of the plurality of first connecting patterns 17 and the upper surface of each of the two isolated patterns 18, and these upper surfaces extend in the plane direction. are independent of each other but form the same plane. Specifically, the first conductor upper surfaces 26 of the plurality of first connecting patterns 17 and the first conductor upper surfaces of the two isolated patterns 18 can form a virtual plane along them, and this virtual plane is the test FPC 2. along the surface direction. Therefore, the first conductor upper surface 26 in the pattern to be inspected 11 is a surface that can come into surface contact with the plate lower surface 35 (described later) of the heater 30 in the second step.

Examples of the material of the first conductor layer 16 include materials having a relatively high rigidity, and more specifically, the conductors described above. The thickness of the first conductor layer 16 is, for example, 3 μm or more, preferably 5 μm or more, and for example, 50 μm or less, preferably 20 μm or less.

The second conductor layer 16 is arranged on the insulating lower surface 10 of the insulating layer 5 and has a second connecting pattern 25 that shields the peripheral edge of the lower edge of the insulating through-hole 7 . The second conductor layer 16 partially overlaps the first conductor layer 15 in plan view.

The second connected pattern 25 forms the pattern to be inspected 11 together with the first connected pattern 17 and the isolated pattern 18 described above. A plurality of second connection patterns 25 are arranged so as to include two conductive portions 14 adjacent to the conductive path P. As shown in FIG. Each of the second connection patterns 25 includes two adjacent conductive portions 14 in a plan view, while being shifted from the first connection pattern 25 by one conductive portion 14 along the conductive path P. It is Each second connection pattern 25 includes two conductive portions 14 adjacent along the conductive path P, but does not include the two conductive portions 14 and the conductive portion 14 adjacent along the conductive path P. are placed. Therefore, adjacent second connection patterns 25 are independent of each other.

Further, the second conductor layer 16 has, for example, a third conductor layer 19 and a fourth conductor layer 20 arranged downward in this order.

The third conductor layer 19 contacts the insulating bottom surface 10 of the insulating layer 5 . That is, the third conductor layer 19 is arranged below the insulating bottom surface 10 . Both the upper surface and the lower surface of the third conductor layer 19 are flat. In addition, the third conductor layer 19 has a conductor inner surface 21 flush with the insulating inner surface 8 of the insulating layer 5 . The third conductor layer 19 serves as a base (seed film) when forming the fourth conductor layer 20 by plating (see FIG. 4C).

The fourth conductor layer 20 is arranged on the lower surface and conductor inner surface 21 of the third conductor layer 19 . The fourth conductor layer 20 arranged on the conductor inner surface 21 is continuous with the conductive portion 14 that contacts the insulating inner surface 8 . Specifically, the fourth conductor layer 20 extends upward along the conductor inner side surface 21 of the third conductor layer 19 as it extends from the edge of the lower surface of the third conductor layer 19 toward the inside of the insulation through-hole 7 . , and has a substantially L shape in cross section that is continuous with the lower portion of the peripheral end portion of the conductive portion 14 . Also, the fourth conductor layer 20 is in surface contact with all the lower surfaces of the plurality of conducting portions 14 .

Materials for the second conductor layer 16 (the third conductor layer 19 and the fourth conductor layer 20) include the conductors described above. The thickness of the second conductor layer 16 is the total thickness of the third conductor layer 19 and the fourth conductor layer 20, and is 5 μm or more, preferably 10 μm or more, for example, 100 μm or less, preferably 40 μm or less. The thickness of each of the third conductor layer 19 and the fourth conductor layer 20 is, for example, 3 μm or more, preferably 5 μm or more, and is, for example, 50 μm or less, preferably 20 μm or less.

In this conductor pattern 6, it passes from one terminal portion 12 through the corresponding connection portion 13 along the conductive path P in the pattern to be inspected 11, and passes through the other terminal portion 12 through the corresponding connection portion 13. electricity will flow. Electricity flows along the conductive path P in the pattern to be inspected 11 in plan view. In the pattern to be inspected 11 , in a cross-sectional view along the conductive path P, electricity flows through the first conductor layer 15 and the second conductor layer 16 arranged on both upper and lower surfaces of the insulating layer 5 through the conducting portion 14 . , proceeding alternately. For example, electricity flows along the first connecting pattern 17 of the first conductor layer 15 on the upper surface of the insulating layer 5, travels downward through the conductive portion 14 on the upper side of the insulating through-hole 7, and then On the lower surface of the insulating layer 5 , proceed along the second connection pattern 25 of the second conductor layer 16 , on the lower side of the insulating through-hole 7 , proceed upward via the conductive portion 14 , and again on the upper surface of the insulating layer 5 . , it flows along the first connection pattern 17 of the first conductor layer 15, and these are repeated.

Of the four terminals 12, two terminal portions 12 input/output electricity from both ends of the conductive path P, and the remaining two terminal portions 12 input/output electricity from the middle of the conductive path P. .

In the first step, the FPC assembly 1 described above is manufactured (prepared).

As shown in FIG. 4A, to manufacture (preparate) the FPC assembly 1, first, the insulating layer 5, the first conductor layer 15 and the third conductor disposed on the insulating upper surface 9 and the insulating lower surface 10, respectively. A three-layer substrate 22 comprising layer 19 is provided. That is, the three-layer base material 22 includes the third conductor layer 19, the insulating layer 5, and the first conductor layer 15 in this order toward the upper side. In the three-layer base material 22, the third conductor layer 19 is arranged over the entire insulating lower surface 10 of the insulating layer 5, and the first conductor layer 15 is arranged over the entire insulating upper surface 9 of the insulating layer 5. .

As shown in FIG. 4B, insulating through-holes 7 are then formed in the insulating layer 5 . Specifically, the insulating through-holes 7 are formed in the insulating layer 5 and the conductor through-holes 23 are formed in the third conductor layer 19 . The insulating through-holes 7 and the conductor through-holes 23 communicate in the thickness direction. Simultaneously with the formation of the insulating through-holes 7 and the conductor through-holes 23, the portions (both left and right ends in FIG. Remove.

Methods for forming the insulating through-holes 7 and the conductor through-holes 23 include, for example, laser processing and etching, preferably laser processing.

As shown in FIG. 4C, a fourth conductor layer 20 and a conducting portion 14 are then provided.

For example, first, a plating resist (not shown) is placed on a portion where the fourth conductor layer 20 and the conductive portion 14 are not formed, and then plating is performed using the third conductor layer 19 as a seed film (power supply layer), After forming the fourth conductor layer 20 and the conductive portion 14, the plating resist is removed.

As a result, a continuous layer 24 is formed as a plated layer in which the fourth conductor layer 20 and the conductive portion 14 are continuous with each other. As a result, the second conductor layer 16 including the third conductor layer 19 and the fourth conductor layer 20 is formed, and the conductive portion 14 that electrically connects the first conductor layer 15 and the second conductor layer 16 is formed.

As a result, the long sheet 3 including the product FPC 4 (see FIG. 1) and the test FPC 2 including the conducting portion 14, the first conductor layer 15 and the second conductor layer 16 is obtained.

After that, as shown in FIG. 1, the long sheet 3 is cut along the width direction to obtain the FPC assembly 1 . Thus, the FPC assembly 1 is prepared.

Next, as shown in FIG. 5, a second step of evaluating electrical characteristics of the test FPC 2 is performed.

To perform the second step, first, an inspection device (an example of an FPC inspection device) 28 is prepared. The inspection device 28 includes, for example, a power source 29, a heating element 30, and a resistance measuring device 31 as an example of an evaluation device. The inspection device 28 can also be equipped with a cooling device (not shown) such as a Peltier device or an air blower, if necessary.

The power supply 29 can continuously apply a voltage to the heater 30 .

The heating element 30 is electrically connected to the power supply 29 via power supply wiring 32 . The material of the heater 30 is, for example, an electrothermal material (a material that generates heat by electrical energy). The heating element 30 has a plate portion 33 and bent portions 34 that are continuous with both ends of the plate portion 33 and bent upward.

The plate portion 33 has a sheet shape extending in the plane direction, and has a plate lower surface 35 and a plate upper surface 38 that are examples of a second contact surface (contact surface). The plate lower surface 35 and the plate upper surface 38 are parallel to each other and both are flat. In addition, the plate portion 33 has a plan view shape and dimensions that overlap with the pattern to be inspected 11 but do not overlap with the terminal portion 12 and the connecting portion 13 when the plate portion 33 is brought into contact with the test FPC 2 .

Examples of the resistance measuring device 31 include a four-terminal resistance measuring device.
The resistance measuring device 31 is connected to the measurement wiring 33 . A computing device (not shown) including a CPU (not shown) is connected to the resistance measuring device 31 .

A cooling device (not shown) is provided in the vicinity of the heating element 30 and can contact the plate top surface 38 of the heating element 30 when in use.

Thereby, the heating element 30 can be continuously heated and cooled in the inspection device 28 .

Subsequently, solder 37 is provided on the upper surface of the terminal portion 12 (first conductor upper surface 26) of the test FPC 2, and the pattern to be inspected 11 is connected to the connecting portion 13 and the terminal portion 12 as shown by the phantom lines in FIG. 2A. , solder 37 and measurement wiring 33 to electrically connect to the resistance measuring instrument 31 .

Subsequently, the resistance measuring device 31 preliminarily measures changes in the electrical characteristics (resistance change rate, resistance change amount, etc.) of the pattern to be inspected 11 based on the processing of a computing device (not shown). At this time, the pattern to be inspected 11 is not yet contacted with a heater 30, which will be described later, so that an abnormality in the change in electrical characteristics of the pattern to be inspected 11 is not normally detected.

Subsequently, with the plate lower surface 35 facing the upper surface of the test FPC 2 , the heater 30 is lowered to bring the plate lower surface 35 into contact only with the first conductor upper surface 26 of the pattern 11 to be inspected. That is, the plate portion 33 is brought into contact with the first conductor layer 15 only from above the test FPC 2 . Specifically, the plate lower surface 35 is brought into surface contact only with the first conductor upper surface 26 of the pattern 11 to be inspected. At this time, the plate lower surface 35 includes all of the plurality of conducting portions 14 in plan view. Also, at this time, the lower surface of the test FPC 2 may be supported by a support (not shown). The support base is set at room temperature (specifically, 25° C.). Alternatively, the lower surface of the test FPC2 may not be supported. In this case, the lower surface of the test FPC2 is exposed to room temperature (25° C.) air.

Subsequently, the heating body 30 is heated (heating process), the temperature of the heating body 30 is maintained (maintenance process), and the heating body 30 is cooled (cooling process) by a predetermined temperature program.

In the heating process, in order to heat the heating body 30, a predetermined voltage is applied from the power supply 29 to the heating body 30 to cause the heating body 30 to generate heat.

Then, the heat of the heating element 30 is conducted from the plate lower surface 35 to the first conductor upper surface 26 . Further, the heat is conducted downward from the first conductor upper surface 26 of the first conductor layer 15 and then conducted to the conductive portion 14 and the second conductor layer 16 in order.

In the maintenance step, to maintain the temperature of the heating element 30, the voltage applied by the power supply 29 is adjusted so that the temperature of the already heated (or cooled) heating element 30 does not rise or fall.

In the cooling process, in order to cool the heating body 30, the application of the voltage in the power source 20 is canceled, and the heating body 30 heated or maintained at the temperature is allowed to cool (slow cooling). Alternatively, if necessary, a cooling device (not shown) is brought into contact with or close to the plate upper surface 38 to rapidly cool the heating element 30 .

The temperature program may include, for example, any one of the heating step S1, the maintaining step S2, and the cooling step S3, and is not particularly limited. program. The first to third programs will be described below in order.

As shown in FIG. 6A, the first program sequentially includes one heating step S1, one maintaining step S2, and one cooling step S3. The heating rate in the heating step S1 is, for example, 0.1° C./second or more, preferably 1° C./second or more, and is, for example, 100° C./second or less, preferably 10° C./second or less. . The temperature rise time t1 in the heating step S1 is appropriately set according to the temperature rise rate described above and the temperature T1 in the maintenance step described below. The maintenance temperature T1 in the maintenance step is the final temperature rise in the heating step S1, and is, for example, 90° C. or higher, preferably 130° C. or higher, and, for example, 300° C. or lower, preferably 180° C. or lower. be. A maintenance time t2 in the maintenance step is, for example, 1 second or more, preferably 10 seconds or more, and is, for example, 1000 seconds or less, preferably 100 seconds or less. The cooling rate and time in the cooling step are not particularly limited.

As shown in FIG. 6B, steps and conditions not specifically described in the second program are the same as those in the first program, and their description is omitted. The second program is set to heat the heating element 30 to temperatures different from each other in the heating step S1. Specifically, in the second program, the heating element 30 is heated stepwise. The heating step S1 sequentially includes a first heating step S4 and a second heating step S5. Moreover, the maintenance step S2 includes a first maintenance step S6 and a second maintenance step S7 in this order. Specifically, the second program includes, in order, a first heating step S4, a first maintaining step S6, a second heating step S5, a second maintaining step S7, and a cooling step S3.

The heating rate and time in the first heating step S4 and the second heating step S5 are appropriately selected from the heating step S1 in the first program.

The maintaining temperature T2 in the first maintaining step S6 is, for example, 10° C. or more lower, preferably 20° C. or more lower, more preferably 30° C. or more lower than the maintaining temperature T3 in the second maintaining step S7, and For example, lower than 100°C. The maintenance temperature T2 in the first maintenance step S6 is, for example, 70° C. or higher, preferably 110° C. or higher, and is, for example, 200° C. or lower, preferably 150° C. or lower.
The maintaining temperature T3 in the second maintaining step S7 is the same as the temperature in the maintaining step S2 in the first program.

As shown in FIG. 6C, steps and conditions not specifically described in the third program are the same as those in the first and second programs, and their description is omitted. The third program is set to cool the heating element 30 to temperatures different from each other in the cooling step. Specifically, in the third program, the heating element 30 is cooled stepwise. The cooling step S3 includes a first cooling step S8 and a second cooling step S9. Moreover, the maintenance step S2 includes a second maintenance step S7 and a first maintenance step S6 in this order. Specifically, the third program includes, in order, a heating step S1, a second maintaining step S7, a first cooling step S8, a first maintaining step S6, and a second cooling step S9. The temperature decrease rate in the first cooling step S8 is, for example, the same as the temperature increase rate in the second heating step S5 in the second program.

On the other hand, while the above-described temperature program is being executed for the heating element 30, changes in electrical characteristics (resistance change rate and resistance change amount) of the pattern to be inspected 11 are continuously measured.

Then, during execution of the temperature program for the heating element 30, for example, if the contact between the conductive portion 14 and the first conductor lower surface 27 of the first conductor layer 15 is released (partially released), As a result, the resistance of the pattern to be inspected 11 increases. Then, a change in the electrical characteristics (resistance change rate or resistance change amount) of the pattern to be inspected 11 is detected. As a result, the FPC assembly 1 including the test FPC 2 is determined to be defective because it is unsuitable for mounting the electronic components described below. After that, the FPC assembly 1 determined as a defective product is sorted and discarded.

On the other hand, during execution of the temperature program for the heating element 30, for example, if the contact between the conductive portion 14 and the first conductor lower surface 27 of the first conductor layer 15 continues, the resistance of the pattern to be inspected 11 does not increase. , the change in electrical characteristics (resistance change rate and resistance change amount) of the pattern to be inspected 11 is not detected. Therefore, the FPC assembly 1 including this test FPC 2 is suitable for mounting electronic components, and thus is determined as a non-defective product.

On the other hand, the plurality of product FPCs 4 in the FPC assembly 1 determined as non-defective products are separated into individual pieces, and electronic components such as head ICs (specifically, heat-generating components that generate heat when driven) are mounted on the upper surfaces of the product FPCs 4. do. Along with this, the product FPC 4 is installed in, for example, a hard disk drive.

According to this manufacturing method, in the second step, the heating element 30 is brought into contact with the first conductor layer 15 only from above the test FPC 2 to evaluate the electrical characteristics of the test FPC 2, so that the product FPC 4 generates heat. The heat resistance of the test FPC 2 can be evaluated in an environment that is the same as or similar to the environment in which the resulting electronic component is mounted. Therefore, the heat resistance of the test FPC 2 can be evaluated accurately. As a result, it is possible to manufacture the FPC assembly 1 including the test FPC 2 whose heat resistance has been accurately evaluated.

According to this manufacturing method, in the second step, the flat plate lower surface 35 of the plate portion 33 is brought into surface contact with the first conductor upper surface 26 of the pattern 11 to be inspected. The environment can be the same as that in which the product FPC 4 is surface-mounted, and the heat resistance of the test FPC 2 can be evaluated more accurately.

According to this manufacturing method, in the first step, the conducting portion 14 is arranged so as to be included in the first conductor upper surface 26 when projected in the thickness direction. 15 to the conduction portion 14 can be rapidly conducted. Therefore, the heat resistance of the test FPC 2 can be evaluated accurately. As a result, it is possible to manufacture the FPC assembly 1 including the test FPC 2 whose heat resistance has been accurately evaluated.

Further, according to this manufacturing method, in the first step, the pattern to be inspected 11 is provided with a plurality (30 pieces) of conductive portions 14, and in the second step, the electrical characteristics of the pattern to be inspected 11 are evaluated. The electrical properties of the FPC 2 can be evaluated more accurately.

According to this manufacturing method, since the heater 30 is brought into contact with the first conductor layer 15 of the test FPC 2 in the second step, the product FPC 4 can be prevented from being damaged by heat.

In the methods of Non-Patent Documents 1 and 2, the FPC is evaluated after being heated in an oil bath and a heating furnace and then taken out.

On the other hand, according to this manufacturing method, the change in electrical resistance of the test FPC 2 is continuously measured while the test FPC 2 is being heated. can be evaluated accurately.

Further, in the second step of this manufacturing method, the temperature program includes a heating step S1 for heating the heating element 30, a maintaining step S2 for maintaining the temperature of the heating element 30, and a cooling step S3 for cooling the heating element 30. , the second step can be set and executed according to the environment around the actual product FPC4.

In particular, the second program and the third program set the temperature of the heating element 30 to different temperatures, so that the heating step S2 can be performed in accordance with the actual surrounding environment of the FPC.

In this FPC inspection method, in the second step, the heating element 30 is brought into contact with the first conductor layer 15 only from above the test FPC 2 to evaluate the electrical characteristics of the test FPC 2. Therefore, the product FPC 4 is an electronic component (Fig. (not shown)) can be evaluated for heat resistance of the test FPC 2 in an environment that is the same as or similar to the environment in which the test FPC 2 is implemented. Therefore, the heat resistance of the test FPC 2 can be accurately evaluated in accordance with the environment in which the product FPC 4 mounts electronic components.

This FPC inspection apparatus 28 can accurately evaluate the heat resistance of the test FPC 2 in accordance with the environment in which electronic components are mounted on the product FPC 4 .

In this inspection device 28 , the heating body 30 has a flat plate lower surface 35 , so that the heating body 30 can be brought into surface contact with the first conductor layer 15 . Therefore, the product FPC 4 can be made to have the same environment as that in which electronic components are planarly mounted, and the heat resistance of the test FPC 2 can be evaluated more accurately.

Since the heating element 30 can heat and cool continuously, the test FPC 2 is provided with a heat history suitable for the environment where the electronic parts are mounted on the product FPC 4, and the heat resistance of the test FPC 2 can be accurately evaluated. can be done.

Since the resistance measuring device 31 can continuously measure the change in electrical resistance of the test FPC 2, it is possible to accurately evaluate the heat resistance of the test FPC 2 corresponding to the heat history actually received by the product FPC 4. .
[Modification]
In the following modified examples, the same reference numerals are given to the same members and steps as in the above-described embodiment, and detailed description thereof will be omitted. In addition, each modification can be combined as appropriate. Furthermore, each modification can have the same effects as the one embodiment, unless otherwise specified.

The number of terminal portions 12 is not particularly limited, and may be two, for example, as shown in FIGS. 7A to 9C.

As shown in FIGS. 7A to 7C, the two terminal portions 12 are arranged on both longitudinal sides of the pattern 11 to be inspected. One terminal portion 12 is electrically connected to the isolated pattern 18 via the connecting portion 13 . The other terminal portion 12 is electrically connected to the first connection pattern 17 via the connection portion 13 . The pattern to be inspected 11 has an S shape in plan view. Fifteen conductive portions 14 are provided along the S-shaped pattern of the pattern to be inspected 11 .

As shown in FIGS. 8A to 8C, the two terminal portions 12 are both arranged on one longitudinal side of the pattern 11 to be inspected. The pattern 11 to be inspected has a U-shape in plan view that opens toward one side in the longitudinal direction. Twenty conductive portions 14 are provided along the U-shaped pattern of the pattern 11 to be inspected.

The shape of each of the first connection pattern 17 and the second connection pattern 25 is not particularly limited. For example, as shown in FIGS. There may be.

Moreover, although not shown, the insulating inner side surface 8 of the insulating layer 5 may be a straight surface extending along the thickness direction.

Moreover, although not shown, the number of the conducting portions 14 may be one.

Moreover, in one embodiment, the second conductor layer 16 is formed of two layers, the third conductor layer 19 and the fourth conductor layer 20. However, for example, although not shown, it can be formed of a single layer.

Also, as shown in FIG. 3, the boundary between the third conductor layer 19 and the fourth conductor layer 20 in the second conductor layer 16 is clearly drawn, but the boundary between them is unclear and harmoniously integrated. may be

Moreover, although not shown, the thickness of the conductive portion 14 may be thinner than the thickness of the insulating layer 5 as long as the first conductor layer 15 and the second conductor layer 16 are electrically connected.

Also, in the second step of one embodiment, the electrical characteristics of the test FPC 2 were evaluated. However, it is also possible to evaluate the electrical characteristics of the product FPC4 itself. In this case, only the product FPC 4 can be arranged in the FPC assembly 1 in the first step. Therefore, it is not necessary to secure a space for providing the test FPC 2 in the FPC assembly 1, and as a result, the yield of the product FPC 4 in the FPC assembly 1 can be improved.

On the other hand, in one embodiment, instead of actually evaluating the heat resistance of the product FPC4, the test FPC2 is evaluated, so that damage to the product FPC4 due to heat can be suppressed.

In the second step of one embodiment, the electrical characteristics of the test FPC 2 are evaluated in advance while the test FPC 2 is attached to the FPC assembly 1. For example, the test FPC 2 is separated from the FPC assembly 1 and , the electrical properties of the test FPC2 can be evaluated.

In one embodiment, changes in the electrical properties of the pattern under test 11 were measured before the plate bottom surface 35 contacted the first conductor top surface 26, but for example, at the same time as the plate bottom surface 35 contacted the first conductor top surface 26 ( or immediately after), the change in the electrical characteristics of the pattern to be inspected 11 can also be measured.

Also, the temperature program in the second step is not limited to the above. For example, in the third program, the heater 30 is heated in two stages, but it may be heated in three stages or more. As shown in FIG. 6D, for example, in the fourth program for heating the heating element 30 in three stages, the heating step S1 includes a first heating step S4, a second heating step S5, and a third heating step S10 in this order. . Moreover, the maintenance step S2 includes a first maintenance step S6, a second maintenance step S7, and a third maintenance step S11 in this order. Specifically, the fourth program performs a first heating step S4, a first maintaining step S6, a second heating step S5, a second maintaining step S7, a third heating step S10, a third maintaining step S11, and a cooling step S3. , prepare in order.

Also, the number of times each program is performed is not particularly limited, and as shown in FIG. 6E, a fifth program that performs the first program a plurality of times (for example, three times) may be used.

Specific numerical values such as the mixing ratio (content ratio), physical property values, and parameters used in the following description are described in the above "Mode for Carrying Out the Invention", the corresponding mixing ratio (content ratio ), physical properties, parameters, etc. can.

Example 1
As shown in FIG. 1, the long sheet 3 comprising the product FPC 4 and the test FPC 2 was cut to manufacture the FPC assembly 1 comprising the product FPC 4 and the test FPC 2, and the first step was performed. As shown in FIG. 3, the test FPC 2 includes an insulating layer 5 made of polyimide resin, a conductive portion 15 made of copper, a first conductor layer 15 made of copper, and a second conductor layer 19 made of copper. Prepare. The number of conducting portions 14 is thirty. In addition, the pattern to be inspected 11 includes the entire conductive portion 14 in plan view.

Next, as shown in FIG. 5, an inspection device 28 was prepared. The inspection device 28 includes a power source 29, a heating element 30, a resistance measuring device 31, and a cooling device.

Then, solder 37 was applied to each of the four terminal portions 12 , and the four terminal portions 12 were electrically connected to the resistance measuring instrument 31 via the measurement wiring 33 .

Subsequently, the plate lower surface 35 of the heating element 30 was brought into surface contact with the first conductor upper surface 26 of the pattern 11 to be inspected. Subsequently, the temperature program shown in Table 1 was executed, and the rate of change in resistance and the amount of change in resistance of the pattern 11 to be inspected were continuously measured. Thus, the electrical characteristics of the test FPC2 were evaluated, and the second step was performed (inspected).

Examples 2 to 5
Except for changing the temperature program in the second step according to Table 1, the same processing as in Example 1 was performed, and the electrical characteristics of the test FPC 2 were evaluated in the second step.

1 FPC assembly 2 Test FPC
4 Product FPC
5 Insulating layer 7 Insulating through-hole 15 First conductor layer 19 Second conductor layer 26 First conductor upper surface 28 Inspection device 30 Heating body 31 Resistance measuring device 35 Board lower surface S1 Heating process S2 Maintaining process S3 Cooling process

Claims (12)

an insulating layer having a through hole penetrating in the thickness direction;
a first conductor layer arranged on one side in the thickness direction of the insulating layer;
a second conductor layer arranged on the other side of the insulating layer in the thickness direction;
A flexible printed wiring board provided with a plurality of conducting portions arranged in the through hole and electrically conducting the first conductor layer and the second conductor layer, wherein the first conductor layer has a plurality of a pattern to be inspected forming a conductive path in which the conductive portions are arranged, wherein the pattern to be inspected includes a plurality of first connecting patterns each including two of the conductive portions adjacent to each other along the conductive path; a first step of preparing the flexible printed wiring board independently having isolated patterns including the conductive portions at both ends of the conductive path;
A heating body is brought into surface contact with the entire pattern to be inspected of the first conductor layer from only one side in the thickness direction of the flexible printed wiring board so that the heating body includes all of the plurality of conductive portions. and a second step of evaluating electrical characteristics of the flexible printed wiring board. In the first step, preparing the flexible printed wiring board including the first conductor layer having a flat first contact surface along a direction orthogonal to the thickness direction,
2. The flexible printed wiring according to claim 1, wherein in said second step, said second contact surface of said heating element having a flat second contact surface is brought into surface contact with said first contact surface. Board manufacturing method. 3. Manufacturing the flexible printed wiring board according to claim 2, wherein in the first step, the conductive portion is arranged so as to be included in the first contact surface when projected in the thickness direction. Method. In the first step, a flexible printed wiring board assembly including a plurality of the flexible printed wiring boards is prepared,
The plurality of flexible printed wiring boards includes a product flexible printed wiring board to be a product and a test flexible printed wiring board,
The flexible printed wiring board according to any one of claims 1 to 3, wherein in the second step, the heating body is brought into contact with the first conductor layer of the test flexible printed wiring board. Production method. 5. The method for manufacturing a flexible printed wiring board according to claim 1, wherein a change in electrical resistance of said flexible printed wiring board is continuously measured. The second step is
a heating step of heating the heating body;
a maintaining step of maintaining the temperature of the heating element;
a cooling step of cooling the heating body ;
The method for manufacturing a flexible printed wiring board according to any one of claims 1 to 5, comprising: 7. The method of manufacturing a flexible printed wiring board according to claim 6, wherein different temperatures are set in said heating step. an insulating layer having a through hole penetrating in the thickness direction;
a first conductor layer arranged on one side in the thickness direction of the insulating layer;
a second conductor layer arranged on the other side of the insulating layer in the thickness direction;
A flexible printed wiring board provided with a plurality of conductive portions arranged in the through holes and electrically conducting the first conductor layer and the second conductor layer, wherein the first conductor layer is: The pattern to be inspected has a pattern to be inspected that forms a conductive path in which a plurality of the conductive portions are arranged in a plane view, and the pattern to be inspected includes a plurality of first conductive portions each including two of the conductive portions adjacent to each other along the conductive path. a first step of preparing the flexible printed wiring board having, independently of each other, a connection pattern and an isolated pattern including the conductive portions at both ends of the conductive path;
A heating body is brought into surface contact with the entire pattern to be inspected of the first conductor layer from only one side in the thickness direction of the flexible printed wiring board so that the heating body includes all of the plurality of conductive portions. and a second step of evaluating electrical characteristics of the flexible printed wiring board. A flexible printed wiring board inspection apparatus used in the flexible printed wiring board inspection method according to claim 8,
the heating body;
An inspection apparatus for a flexible printed wiring board, comprising: an evaluation apparatus for evaluating electrical characteristics of the flexible printed wiring board. 10. The flexible printed wiring board inspection apparatus according to claim 9, wherein the heating member has a flat contact surface. 11. The flexible printed wiring board inspection apparatus according to claim 9, wherein said heating element can be continuously heated and cooled. The flexible print according to any one of claims 9 to 11, wherein the evaluation device is a resistance measuring instrument capable of continuously measuring changes in electrical resistance of the flexible printed wiring board. Wiring board inspection equipment.

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