JP4105601B2 - Bending test method and bending test apparatus for flexible printed wiring board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bending test method and a bending test apparatus for a flexible printed wiring board in which a flexible printed wiring board is repeatedly bent and a disconnection due to the bending is detected.
[0002]
[Prior art]
In a foldable mobile phone, for example, as shown in FIG. 6, a flip 2 is configured to be openable and closable around a hinge portion 3 with respect to a main body 1, and an input key portion is provided on the main body 1. An information display screen made of liquid crystal is provided on the surface facing the main body 1.
[0003]
In order to connect the connector 5a on the board 5 on the main body 1 side and the connector 6a on the board 6 on the flip 2 side, the hinge part 3 of the foldable mobile phone has a substantially crank shape as shown in FIG. The flexible printed wiring board 10 is arranged in a looped state. In this case, the flexible printed wiring board 10 is formed by a hinge cover (not shown) that restricts the curvature radius of the flexible printed wiring board 10 to a certain value or a sponge (not shown) that keeps the curvature radius of the flexible printed wiring board 10 at a certain value or more. In the state where the deformation is restricted, the bending operation is repeatedly performed. Since the folding fatigue life of the flexible printed wiring board 10 changes due to such a difference in constraint conditions, a test method and apparatus capable of evaluating the influence are necessary.
[0004]
IPC (American Society of Printed Circuits) and MIT (JIS-P-8115) methods are known as bending test methods for flexible printed wiring boards (see, for example, Patent Document 1). In the IPC method, as described in FIG. 7 of Patent Document 1, a flexible printed wiring board is fixed between a fixed plate and a moving plate arranged in parallel, and the moving plate is reciprocally translated and bent. Perform the test. This bending test is a free bending form, and the radius of curvature of the flexible printed wiring board is set by the distance between the fixed plate and the moving plate.
[0005]
On the other hand, in the MIT method, as shown in FIG. 8 of Patent Document 1, a flexible printed wiring board is sandwiched between two fixed dies having a rounded corner formed at the end of a triangular prism, and a certain amount is fixed. A bending test is performed by swinging two fixed dies while holding the flexible printed wiring board in a state where the flexible printed wiring board is wound around one fixed die with tension.
[0006]
In the above two test methods, the test is conducted with a minute current flowing in the internal wiring of the flexible printed wiring board where bending is applied, and the number of times of bending until the wire breaks due to repeated bending is counted to predict the life. .
[0007]
[Patent Document 1]
JP-A-63-290938 (FIGS. 7 and 8)
[0008]
[Problems to be solved by the invention]
Since all of the existing test methods described above are tests using a flexible printed wiring board alone, the flexible printed wiring board used in the hinge part of the folding cellular phone is restricted by a hinge cover or the like. In the case of a flexible printed wiring board bent in a state, since an appropriate bending test cannot be performed, there has been a problem that the bending life of the flexible printed wiring board cannot be accurately evaluated.
[0009]
The present invention is intended to solve this problem, and to realize a bending test method and a bending test apparatus capable of accurately predicting the life of a flexible printed wiring board used in a state where an intermediate portion is looped in an annular shape. It is intended.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 is a flexible printed wiring board bending test method for repeatedly bending a flexible printed wiring board and detecting disconnection due to the bending, in a state where the flexible printed wiring board is looped in an annular shape, In addition, while flexibly bending the flexible printed wiring board in a state where the variation range of the curvature radius of the loop portion is regulated, the bending operation of the flexible printed wiring board is intermittently performed while the flexible printed wiring board is stopped at the bending position for a certain period of time. It repeats automatically.
[0011]
In the present invention, the flexible printed wiring board used in a state where the intermediate portion is looped in an annular shape is bent in a state where the variation range of the radius of curvature of the loop portion is regulated, so that it is used in a foldable mobile phone. Can be tested in a situation close to. For this reason, it is possible to accurately predict the lifetime of this type of flexible printed wiring board.
[0012]
In a foldable mobile phone, the flexible printed wiring board is often bent and held in the folded state (the state in which the flexible printed wiring board is in a bent position) that is most stressed for a long time. As a variation factor of the fatigue life in such a flexible printed wiring board, there is a time factor to which stress is applied. For this reason, a test method capable of simulating the bending holding time is desired. However, the present invention is optimal for such a test because the flexible printed wiring board is repeatedly bent while stopping at a bending position for a certain period of time. , Accurate life prediction becomes possible.
[0013]
The invention according to claim 2 is the invention according to claim 1, wherein a regulating member is disposed on at least one of the inside and the outside of the loop portion of the flexible printed wiring board, and the loop portion of the flexible printed wiring board is applied to the regulating member. By making contact, the fluctuation range of the radius of curvature of the loop portion is regulated. In this way, the fluctuation range of the radius of curvature of the loop portion can be easily regulated.
[0014]
In the invention according to claim 3, the flexible printed wiring board is repeatedly bent by turning one end of the flexible printed wiring board with respect to the other end, and the disconnection on the internal wiring of the flexible printed wiring board due to the bending is detected. The present invention relates to a flexible printed wiring board bending test apparatus, and supports both ends of a flexible printed wiring board so that an annular loop portion is formed at an intermediate portion of the flexible printed wiring board, and one end of the flexible printed wiring board is the other end. The bending portion of the flexible printed wiring board can be bent repeatedly by swiveling with respect to the bending portion of the flexible printed wiring board, and the curvature of the loop portion during the bending operation of the flexible printed wiring board A regulating member that regulates the range of variation of the radius; A bending control section that drives the bending support section to reciprocate the flexible printed wiring board between the bending position and the open position, and at the bending position, stops one end of the flexible printed wiring board at that position for a certain period of time. It is characterized by having.
[0015]
Even in the present invention, a flexible printed wiring board that is used in a state where the intermediate portion is looped in an annular shape can be tested in a state close to the state of use, so accurate life prediction is possible, and the flexibility of a foldable mobile phone It is most suitable for the life test of the wiring board. In addition, the restricting member can easily restrict the fluctuation range of the curvature radius of the loop portion while having a simple configuration.
[0016]
According to a fourth aspect of the invention, in addition to the configuration of the third aspect of the invention, a calculation means for calculating a strain amplitude at a portion where the maximum stress of the internal wiring of the flexible printed wiring board is applied during bending, and the flexible printed wiring From a plurality of data showing the relationship between the measured value of the cumulative number of bendings when the disconnection on the internal wiring of the plate is detected and the calculated value by the calculation means of the strain amplitude received during the bending operation of the disconnected internal wiring, It is characterized by having a life prediction unit for creating a life prediction formula showing the relationship of the life of the internal wiring to the strain amplitude received by the internal wiring.
[0017]
In the present invention, by calculating the distortion amplitude of the internal wiring at the bending angle assumed to be used and substituting it into the life prediction formula, the life of the internal wiring at the bending angle can be accurately predicted. In addition, as long as the flexible printed wiring board is made of the same material, even if the pattern of the flexible printed wiring board is changed, the life can be predicted by using the same life prediction formula as it is, and it is easy to respond to design changes it can.
[0018]
Embodiment
(First embodiment)
A first embodiment of the present invention (which is a bending test apparatus according to the present invention and an apparatus for performing the method of the present invention) will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is an exploded perspective view of the present embodiment example, and FIG. 2 is a configuration and operation explanatory diagram showing the present embodiment example (main configuration diagram viewed from the side). In this embodiment, as shown in FIG. 5, a substantially crank-shaped flexible printed wiring board 10 including straight portions 10 m and 10 n that are shifted to the left and right and an intermediate portion 10 k that obliquely connects these is used as an object of the bending test. Use.
[0019]
The flexible printed wiring board 10 is set in a bending test apparatus in a looped state. That is, the flexible printed wiring board 10 has one end portion 10b fixed to the fixed base 12 via the mounting member 11 so that an annular loop portion 10a is formed in the intermediate portion 10k, and the other The end 10 c is fixed to the moving base 14 via the attachment member 13.
[0020]
The moving base 14 is configured to be able to turn with respect to the fixed base 12, and the end portion 10 c of the flexible printed wiring board 10 can be reciprocated with respect to the end portion 10 b. That is, the flexible printed wiring board 10 can be bent repeatedly. The mounting members 11, 13, the fixed base 12, and the moving base 14 constitute a bending support portion 15 that supports the flexible printed wiring board 10 so that it can be bent.
[0021]
In addition, since the intermediate part 10k of the flexible printed wiring board 10 is formed obliquely, the loop part 10a is wound in a spiral shape, and the loop part 10a does not overlap. Further, the central axis of the loop portion 10 a of the flexible printed wiring board 10 and the turning center axis (rotation center axis) O of the moving base 14 substantially coincide with each other.
[0022]
The attachment members 11 and 13 may be any members as long as they can fix the end portions 10b and 10c of the flexible printed wiring board 10 to the fixed base 12 and the movable base 14, respectively. If the connectors 5a and 6a are replaced with the attachment members 11 and 13 and the connectors 5a and 6a are fixed to the fixed base 12 and the movable base 14, respectively, the attachment members 11 and 13 can be easily configured.
[0023]
The regulating member 20 is fixed to the fixed base 12 using a fixing screw or the like (not shown). The regulating member 20 is in contact with the loop portion 10a of the flexible printed wiring board 10 from the outside, and regulates the variation range of the curvature radius of the loop portion 10a during the bending operation of the flexible printed wiring board 10 to a certain value or less.
[0024]
In this embodiment, the restricting member 20 has an arcuate abutting portion 20a, and this abutting portion 20a is located at the lower left in FIG. 5 in order to avoid interference with the straight portion 10n of the flexible printed wiring board 10. It contacts only the right half (the right half of the intermediate portion 10k or the straight portion 10m). Another regulating member may be provided so as to contact the left half of the flexible printed wiring board 10 (the left half of the intermediate portion 10k or the straight portion 10n), but the flexible printed wiring board 10 shown in FIG. Because of the symmetrical shape, the regulating member 20 is also in contact with a position near the center of the flexible printed wiring board 10, and it is sufficient to contact the right half.
[0025]
The bending control unit 30 drives the bending support unit 15 by using a motor (not shown) to move the flexible printed wiring board 10 in the bending position (the closed state in FIG. 2B) and the open position (the opening in FIG. 2A). And at least at the bent position, the flexible printed wiring board 10 is stopped at that position for a certain period of time.
[0026]
In the case of the flexible printed wiring board 10 used in a foldable mobile phone, the open position is a state opened about 160 ° from the bent position, so the bending angle θ (range) of the moving base 14 is set to 160 °. Set to degree. The stop time at the bent position of the flexible printed wiring board 10 is, for example, the stop time at the open position and the bent position so as to match the ratio between the use time and non-use time of the mobile phone by a general user. Set the ratio to the stop time at. These settings are made by the operator for the bending control unit 30.
[0027]
When performing a bending test using the bending test apparatus, the flexible printed wiring board 10 and the bending support portion 15 are placed in a thermostatic oven or the like, and the test is performed in an environment of constant temperature and constant humidity. In the test, the flexible printed wiring board 10 is repeatedly bent, a disconnection due to this bending is detected, and the total number of bendings until the disconnection is obtained. For example, the following values are used as the data of the cumulative number of flexing times.
(1) When an experimental method for confirming the presence or absence of disconnection of the internal wiring every time a predetermined number of bending operations is performed, if a disconnection is found, the cumulative number of bending operations so far (or the presence or absence of the most recent disconnection) The cumulative number of flexures is the cumulative number of times at the time of confirmation that there is no disconnection.
{Circle around (2)} When an experimental method is employed in which a bending test is performed while constantly monitoring a disconnection by passing a weak current through the internal wiring, the cumulative number of bending operations at the time when the occurrence of the disconnection is detected is taken as the cumulative number of bendings.
[0028]
According to the bending test using this embodiment, the fluctuation range of the radius of curvature of the loop portion 10a of the flexible printed wiring board 10 used in a state where the intermediate portion 10k is looped in an annular shape is regulated by the regulating member 20. Since it is bent in the state, the test can be performed in a state close to the state of use in a foldable mobile phone, so that it is possible to accurately predict the life of this type of flexible printed wiring board 10.
[0029]
Further, the foldable mobile phone is in a folded state where the flexible printed wiring board 10 is most bent and stressed most (the flexible printed wiring board 10 is in a bent position as shown in FIG. 2B) for a long time. Often retained. As a variation factor of the fatigue life of the flexible printed wiring board 10, there is a time factor to which stress is applied. In the bending test using the present embodiment, the flexible printed wiring board 10 is stopped at the bending position for a certain time. Since the bending is repeated intermittently, the bending holding time can be simulated and the life prediction can be performed accurately.
(Second Embodiment)
A second embodiment of the present invention (bending test apparatus) will be described with reference to FIG. 3, parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals, and description of the configuration is omitted. This embodiment is different from the first embodiment in that a columnar regulating member 21 made of sponge or the like is arranged inside the loop portion 10a of the flexible printed wiring board 10, and the flexible printing is attached to the regulating member 21. The point is that the radius of curvature of the loop portion 10a is regulated to a predetermined value or more by bringing the loop portion 10a of the wiring board 10 into contact.
[0030]
In a foldable mobile phone, there may be a hinge portion inside the loop portion 10a of the flexible printed wiring board 10, and when performing a life prediction of the flexible printed wiring board 10 used in such a usage state, Providing the regulating member 21 as in the present embodiment is effective for accurate life prediction.
[0031]
In this embodiment, the regulating member 21 is used instead of the regulating member 20, but both the regulating member 20 and the regulating member 21 may be used. If this restricting member 21 or restricting member 20 is used, the fluctuation range of the curvature radius of the loop portion can be easily restricted.
(Third embodiment)
A third embodiment of the present invention (bending test apparatus) will be described with reference to FIG. 4, portions corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals, and description of the configuration is omitted. This embodiment differs from the first embodiment in that a plurality (five examples are shown in FIG. 4) of flexible printed wiring boards 10 are connected between the fixed base 12 and the movable base 14 of the bending support portion 15. The regulating member 20 is brought into contact with the loop portion 10a of each flexible printed wiring board 10 from the outside, and the fluctuation range of the radius of curvature of the loop portion 10a during the bending operation of the flexible printed wiring board 10 is regulated to a certain value or less. It is a thing.
[0032]
The moving base 14 of the bending support portion 15 is supported at both ends by bearings 31 and 32 so as to be rotatable, and the rotational driving force of the motor 33 is received from the bearing 32 side via the reduction gear train 34 and the clutch mechanism 35. It is configured to be transmitted to the moving base 14. The bearing 32 is provided with an encoder 36 for detecting the amount of rotation (angle) of the moving base 14. Based on this output, the bending control unit 30 drives the bending support unit 15 with the motor 33. The flexible printed wiring board 10 is reciprocated between a bent position (closed state in FIG. 2B) and an open position (open state in FIG. 2A). The wiring board 10 is stopped at that position for a certain period of time.
[0033]
In this embodiment, since a plurality of flexible printed wiring boards 10 can be subjected to a bending test at the same time, it is possible to acquire a large amount of data on the number of integrated bending until a disconnection occurs at a time, thereby saving test time and variation in the number of integrated bending. This makes it possible to know the life of the flexible printed wiring board 10 accurately.
(Fourth embodiment)
In this embodiment, the bending test apparatus is provided with a life prediction unit (not shown) that performs life prediction of the flexible printed wiring board 10. This life prediction unit includes a plurality of data indicating the relationship between the measured value of the cumulative number of bendings when a disconnection on the internal wiring is detected and the calculated value of the strain amplitude that the disconnected internal wiring has undergone during the bending operation. Is input by the operator (or automatically from the bending control unit 30 or the like). In addition, data on the shape, structure, material, and movement of the flexible printed wiring board 10 is also input to the life prediction unit.
[0034]
The life prediction unit first receives data on the shape, structure, material, and movement of the flexible printed wiring board 10, performs analysis by the finite element method, and calculates the distortion of each part. The distortion generated in the internal wiring at the time of bending is not necessarily simply increased or decreased in accordance with the bending angle due to the presence of the regulating members 20 and 21. Even if a distortion characteristic curve with respect to the bending angle is drawn by paying attention to a single distortion, the distortion changes depending on the positional relationship between the loop portion 10a and the regulating member 20 or the like.
[0035]
From the distortion of each part obtained by the above calculation, the life prediction part determines which internal wiring of the flexible printed wiring board 10 has the maximum distortion amplitude. Here, the strain amplitude is a variation range of strain in one cycle of bending (one cycle of opening and closing), and is proportional to the variation range of stress applied to the flexible printed wiring board 10. Therefore, this data can be regarded as a fluctuation range of stress.
[0036]
Next, the relationship between the measured value of the cumulative number of bendings when the disconnection on the internal wiring of the flexible printed wiring board 10 is detected and the calculated value of the distortion amplitude that the disconnected internal wiring has undergone during the bending operation is obtained. Even with the same strain amplitude, the cumulative number of flexing cycles (life cycle number) varies, and for example, a Weibull process is performed to obtain an average value (average life cycle number).
[0037]
For example, in the case of an internal wiring in which the calculated distortion amplitude when the bending angle θ (range) is 160 ° is 0.0462 (mm / mm), the average life cycle number based on actual measurement is 81567, In the case of an internal wiring in which the calculated strain amplitude when the bending angle θ (range) is 80 ° is 0.022 (mm / mm), the average life cycle number based on actual measurement was 565243. Ask for.
[0038]
From this relationship, the life prediction unit creates a fatigue life prediction formula. An example of this life prediction formula is as follows.
[0039]
Nf = 27 × Δε ⁻ⁿ
Where Nf: number of fatigue life cycles (predicted value)
Δε: Distortion amplitude of internal wiring (calculated value)
n: Numerical value determined to some extent by the material of the internal wiring In the case of the numerical example of the strain amplitude and the average life cycle number exemplified earlier, n = 2.6, and the life prediction formula is Nf = 27 × Δε ^−2.6 .
[0040]
Therefore, by calculating the distortion amplitude at the bending angle assumed to be used and substituting this distortion amplitude (calculated value) into Δε of this life prediction formula, the life of the internal wiring at that bending angle can be accurately predicted. . In addition, as long as the flexible printed wiring board 10 is made of the same material, even if the pattern of the flexible printed wiring board 10 is changed, the life can be predicted using the same life prediction formula as it is, and the design can be easily changed. It can correspond to.
[0041]
When obtaining strain using the finite element method, in order to reduce the amount of calculation, first, a rough finite element analysis is performed using the analysis model of the entire flexible printed wiring board shown in FIG. The stress generation position is obtained, and then the distortion of the internal wiring is obtained by a narrow detailed model analysis around this position, and the distortion amplitude is obtained using this.
(Other embodiments)
The present invention is not limited to the first to fourth embodiments. For example, in the above embodiment, a flexible printed wiring board used for a foldable mobile phone is used as a test object, but the present invention is not limited to this.
[0042]
【The invention's effect】
As described above, in the invention according to claim 1, the flexible printed wiring board used in a state where the intermediate portion is looped in an annular shape is bent in a state where the variation range of the radius of curvature of the loop portion is regulated. The test can be performed in a state close to the state of use in a foldable mobile phone, and the life expectancy of this type of flexible printed wiring board can be accurately predicted.
[0043]
In a foldable mobile phone, the flexible printed wiring board is often held in the most bent state for a long period of time. However, in the present invention, since the flexible printed wiring board is bent repeatedly intermittently while being stopped at the bending position for a certain period of time, it is optimal for such a test and enables accurate life prediction.
[0044]
According to the invention which concerns on Claim 2, the fluctuation range of the curvature radius of the loop part of a flexible printed wiring board can be easily controlled with a control member.
[0045]
Also in the invention according to claim 3, since it is possible to test the flexible printed wiring board used in a state where the intermediate portion is looped in an annular shape in a state close to the usage state, it is possible to accurately predict the life, and the folding type It is ideal for testing the life of flexible wiring boards in mobile phones. In addition, the restricting member can easily restrict the fluctuation range of the curvature radius of the loop portion while having a simple configuration.
[0046]
According to the invention of claim 4, by calculating the distortion amplitude of the internal wiring at the bending angle assumed to be used and substituting this into the life prediction formula, the life of the internal wiring at the bending angle is accurately determined. Predictable. In addition, as long as the flexible printed wiring board is made of the same material, even if the pattern of the flexible printed wiring board is changed, the life can be predicted by using the same life prediction formula as it is, and it is easy to respond to design changes it can.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a first embodiment of the present invention.
FIG. 2 is a configuration and operation explanatory diagram showing a first embodiment.
FIG. 3 is a configuration and operation explanatory diagram showing a second embodiment.
FIG. 4 is a diagram illustrating a third exemplary embodiment.
FIG. 5 is a diagram showing a flexible printed wiring board.
FIG. 6 is a diagram illustrating an example of a usage state of a flexible printed wiring board.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Flexible printed wiring board 10a Loop part 10b, 10c End part 10k Intermediate part 10m Straight line part 10m, 10n Straight line part 11, 13 Mounting member 12 Fixed base 14 Movement base 15 Bending support part 20, 21 Restriction member 30 Bending control part 33 Motor 34 Reduction gear train 35 Clutch mechanism 36 Encoder

Claims (4)

A flexible printed wiring board bending test method for repeatedly bending a flexible printed wiring board and detecting disconnection due to the bending,
In a state where the flexible printed wiring board is looped in an annular shape and the fluctuation range of the radius of curvature of the loop portion is restricted, the flexible printed wiring board is repeatedly bent and the bending operation of the flexible printed wiring board is performed. A bending test method for a flexible printed wiring board in which the flexible printed wiring board is intermittently repeated while being stopped at a bending position for a certain period of time. A restricting member is disposed on at least one of the inside and the outside of the loop portion of the flexible printed wiring board, and the fluctuation portion of the curvature radius of the loop portion is restricted by bringing the loop portion of the flexible printed wiring board into contact with the restricting member. The bending test method for a flexible printed wiring board according to claim 1. A flexible printed wiring board bending test apparatus for repeatedly bending a flexible printed wiring board by turning one end of the flexible printed wiring board with respect to the other end, and detecting disconnection on the internal wiring of the flexible printed wiring board due to the bending. Because
The flexible printed wiring board is supported by supporting both ends of the flexible printed wiring board so that an annular loop portion is formed in the middle of the flexible printed wiring board, and turning one end of the flexible printed wiring board with respect to the other end. A bending support that can be bent repeatedly;
A regulating member that regulates the variation range of the radius of curvature of the loop portion during the bending operation of the flexible printed wiring board by contacting the loop portion of the flexible printed wiring board,
A bending control unit that drives the bending support unit to reciprocate the flexible printed wiring board between a bending position and an open position, and in the bending position, stops one end of the flexible printed wiring board at that position for a certain period of time;
Bending test apparatus for flexible printed wiring board. From a plurality of data showing the relationship between the measured value of the cumulative number of bendings when the disconnection on the internal wiring of the flexible printed wiring board is detected and the calculated value of the distortion amplitude that the disconnected internal wiring received during the bending operation, 4. The bending test apparatus for a flexible printed wiring board according to claim 3, further comprising a life prediction unit that creates a life prediction formula indicating a relationship between a life of the internal wiring and a strain amplitude received by the internal wiring.

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