JP2006220590A - Electrical inspection device for flexible printed board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a minute crack developing in a conductor pattern even if the crack is on the lower side of a mounted component without damaging a flexible printed board. <P>SOLUTION: This electrical inspection device 10 is structured by being equipped with upper and lower bases 11 and 12 for interposing the flexible printed board 30 between them, recessedly providing a carved part 13 in the upper base 11, for example, between the upper and lower bases 11 and 12, providing a pressure adjustment means 14 in the carved part 13, and being equipped with a resistance value detection means 19 for measuring the electric resistance value of the conductor pattern provided on the printed board 30. When actuating a suction pump 17 of the adjustment means 14 to deform the printed board 30 so that it swells out toward the carved part 13, it is found that the minute crack has developed since the resistance value measured by the detection means 19 increases if a minute crack develops in this portion to widen the gap of the minute crack by pressure deformation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrical inspection apparatus for a flexible printed circuit board used in electronic equipment, and more particularly to an electrical inspection apparatus for detecting microcracks generated in a conductor pattern of a flexible printed circuit board.

  The flexible printed circuit board is made of a thin material because of its characteristics, and is configured to be easily bent. In the configuration of the flexible printed board, the surface of the conductor pattern is subjected to insulation treatment with an insulating film or an insulating resin depending on the application. Moreover, a film, a glass epoxy laminated board, a metal plate, etc. are added for the reinforcement to the place which needs to increase hardness and thickness.

  Differences in bending strength occur due to such differences in configuration. When bending stress or tensile stress is applied near the boundary where the difference in bending ease occurs, micro cracks are generated in the conductor pattern due to this stress. Sometimes.

  In order to inspect a microcrack, a circuit board is provided in which a continuous resistance having two end portions is provided in close contact with the outer peripheral portion of at least one side of the alumina substrate, and both ends of the resistance are formed. It is known that the presence or absence of microcracks in the portion where the resistance is located can be detected by conducting an alternating current to the first electrode and inspecting the third harmonic distortion (for example, Patent Document 1). reference).

  There is also known a method of detecting a crack by disposing a conductive liquid on at least one surface of a ceramic substrate and measuring an electrical property value of the substrate (for example, see Patent Document 2).

In addition, the flexible printed circuit board is sandwiched between the upper plate member and the lower plate member to fix the mounting component mounted on the substrate, and a force is applied in a direction to separate the substrate from the mounting component to An apparatus for inspecting a soldering state by performing a continuity test between the two is also known (see, for example, Patent Document 3).
JP-A-7-66520 JP-A-9-304324 JP 2004-273726 A

  In the invention described in Patent Document 1, it is necessary to provide a resistance for measurement in advance on an alumina substrate, and extra parts are mounted on the circuit. In the invention described in Patent Document 2, since the conductive liquid is disposed on at least one surface of the ceramic substrate, the apparatus becomes large and the inspection is complicated.

  The invention described in Patent Document 3 is an apparatus for confirming the quality of soldering of mounted components, and it is difficult to detect minute cracks in the conductor pattern. Further, excessive stress is applied to the soldered portion and the flexible printed circuit board, and there is a risk of damaging normal products.

  In addition, in the case of a flexible printed circuit board on which a component is mounted, if it is an outer part of the mounted part, a certain amount of microcracks can be detected by bending the flexible printed circuit board, even in the past with an enlarged inspection using a microscope or the like. Although it was possible, the micro crack on the lower side of the mounted component could not be expanded using a microscope.

  Therefore, the present invention has a technical problem to be solved in order to detect a micro crack generated in the conductor pattern without damaging the flexible printed circuit board and even on the lower side of the mounted component. The present invention aims to solve this problem.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 comprises an upper base and a lower base for sandwiching a flexible printed circuit board, and at least of the upper base and the lower base. A carved portion is provided in any one of the bases, pressure adjusting means is provided in the carved portion, and resistance value detecting means for measuring the electrical resistance value of the conductor pattern provided on the flexible printed circuit board is provided. An electrical inspection apparatus for a flexible printed circuit board is provided.

  According to this configuration, the flexible printed circuit board is sandwiched between the upper base and the lower base, and the pressure of the engraved part is adjusted by the pressure adjusting means, thereby being positioned at the engraved part of the flexible printed circuit board. The part where it is deformed slightly. If a micro crack is generated in the conductor pattern of this portion and the gap of the micro crack is widened by pressure deformation, the electrical resistance value measured by the resistance value measuring means is increased, and thus the micro crack is generated. I understand that.

  According to a second aspect of the present invention, the lower base is provided with a guide plate for positioning a flexible printed circuit board, and includes a connection terminal for conducting electricity to the conductor pattern, and an upper base detection sensor. An electrical inspection apparatus for a flexible printed circuit board according to claim 1 is provided.

  According to this configuration, the positioning guide is positioned so that the specific portion of the flexible printed board comes to the engraved portion. And the location which should make electricity penetrate to the conductor pattern of a flexible printed circuit board is positioned in the place where the connection terminal is installed. When the upper base pushes the lower base down to a predetermined position, the upper base detection sensor detects this, and the pressure adjusting means is activated and electricity is conducted from the connection terminal to the conductor pattern of the flexible printed circuit board. Then, the resistance value measuring means measures the electrical resistance value of the conductor pattern.

  According to a third aspect of the present invention, the positioning guide plate is provided such that a portion where a microcrack is likely to occur in the conductor pattern of the flexible printed circuit board is located in any one of the engraved portions. Item 3. An electrical inspection apparatus for a flexible printed circuit board according to Item 1 or 2.

  According to this configuration, a portion where a microcrack is likely to occur in the conductor pattern of the flexible printed circuit board is, for example, near a boundary having a different thickness or hardness by applying a cover film or a glass epoxy laminated board, or on a mounting component. It can be assumed that it is in the vicinity of soldering, and positioning is performed with a positioning guide so that the back side of the location where such a microcrack is supposed to occur comes to the engraved portion.

  According to a fourth aspect of the present invention, the pressure adjusting means is provided so that the back side of the flexible printed circuit board where a microcrack is likely to occur is bulged and curved in the engraved portion of the base. An electric inspection apparatus for a flexible printed circuit board according to claim 1, 2 or 3.

  According to this configuration, when the pressure adjusting means is actuated, the back side of the flexible printed circuit board is curved so as to bulge into the engraved portion, so that if a micro crack is generated on the surface of the conductor pattern, Since the gap between the microcracks widens and the electrical resistance value increases, the occurrence of microcracks can be detected.

  According to a fifth aspect of the present invention, when the flexible printed circuit board is sandwiched between the upper base and the lower base and a portion where a microcrack is likely to occur is deformed, the change in the electric resistance value of the conductor pattern is measured by the four-terminal method. 5. The flexible printed circuit board electrical inspection apparatus according to claim 1, wherein the resistance value detecting means is provided so as to detect the presence or absence of a microcrack by measurement.

  According to this configuration, the change in the electrical resistance value of the conductor pattern is measured by the four-terminal method. When measured by the two-terminal method, the contact resistance from the inspection target part to the contact point of the inspection device becomes an error, and an accurate resistance value cannot be measured. However, if measured by the four-terminal method, the voltage measuring terminal and the current measuring terminal are Since they are separate, the influence of contact resistance can be removed, and an accurate resistance value can be measured.

  In the present invention, as described above, the engraved portion is provided on the back side of the portion where the micro crack is likely to occur in the conductor pattern of the flexible printed circuit board, and the flexible printed circuit board is moved to the engraved portion side by the operation of the pressure adjusting means. When the conductor pattern is deformed so as to be bent, a gap is generated in the minute crack when the conductor pattern has a minute crack, and the electrical resistance value is increased. For this reason, it is possible to reliably detect a microcrack without damaging the flexible printed circuit board by applying an excessive stress and even on the lower side of the mounted component.

  Hereinafter, a flexible printed circuit board electrical inspection apparatus according to the present invention will be described with reference to preferred embodiments. The purpose of detecting minute cracks occurring in the conductor pattern without damaging the flexible printed circuit board, for example, the engraved part on the back side of the part where the minute cracks are likely to occur in the conductor pattern of the flexible printed circuit board The flexible printed circuit board is deformed so as to bend toward the engraved part by the operation of the pressure adjusting means, and if there are minute cracks in the conductor pattern, a gap occurs in the minute cracks and the electric resistance value changes. It was realized by reading what to do.

  FIG. 1 is a conceptual diagram of an electrical inspection apparatus 10, wherein an upper base 11 and a lower base 12 are provided so as to be openable and closable, and a carved portion 13 is recessed in at least one of the upper base 11 and the lower base 12. The engraving portion 13 is provided with pressure adjusting means 14. In the figure, as an example, a pipe connection portion 15 is attached to a carved portion 13 recessed in the upper base 11, and a suction pump 17 with a switching valve is connected to the pipe connection portion 15 via a suction pipe 16. Thus, the pressure adjusting means 14 is configured.

  The lower base 12 is provided with a guide plate 18 for positioning the flexible printed circuit board 30, a connection terminal 19 for conducting electricity to the conductor pattern of the flexible printed circuit board 30, and the upper base 11. And an upper base detection sensor 20 for detecting that the sensor has been lowered to a predetermined position. As will be described later, a resistance value measuring unit is configured to energize the conductor pattern from the connection terminal 19 and measure the electrical resistance value of the conductor pattern.

  Although not shown, the positioning guide plate 18 is provided with guide pins for positioning the flexible printed board 30 at predetermined positions and through holes for the connection terminals 19. In addition to the proximity sensor, a switch such as a limit switch can be used as the upper base detection sensor 20, and the upper base detection sensor 20 is not the lower base 12 but the upper base 11. You may mount | wear with an outer peripheral part or a vertical movement mechanism part.

  Next, the operation of the electrical inspection apparatus 10 will be described. If the flexible printed circuit board 30 to be inspected is placed on the positioning guide plate 18 of the lower base 12, the flexible printed circuit board 30 is set so that a portion where micro cracks are likely to occur is located in the engraved portion 13. The connection terminal 19 contacts the conductor pattern.

  When the upper base 11 is pushed down to a predetermined position, the upper base detection sensor 20 is turned on, the switching valve is switched, the suction pump 17 is turned on, and the pressure adjusting means 14 is operated. Therefore, air suction starts from the pipe connection portion 15 attached to the engraved portion 13, and the flexible printed circuit board 30 is pulled by this suction, so that the portion of the engraved portion 13 is slightly deformed.

  When the micro crack is generated in the conductor pattern of the flexible printed circuit board 30, the gap of the micro crack is widened by the deformation of the flexible printed circuit board 30, and the electric resistance value of the conductor pattern measured by the resistance value measuring means. Therefore, it can be detected that microcracks have occurred. At this time, the increase in the electric resistance value is several tens of milliΩ or more.

  Also, the electrical resistance value of the conductor pattern is stored as an initial value when the flexible printed circuit board is in a flat state in advance, and then the electrical resistance value of the conductor pattern is measured when the suction pump 17 is turned on and sucked. To do. If the difference between the measured value at this time and the initial value is calculated to detect the occurrence of a microcrack, more accurate detection can be performed. In any measurement method, it is desirable to measure the electric resistance value by a four-terminal method.

Here, the 4-terminal method will be briefly described. FIG. 2 (1) shows a circuit diagram by the two-terminal method, and the resistance value is detected to be higher than the actual value due to the influence of the contact resistance between both terminals T ₁ and T ₂ and the measured object R _x . Fig. 2 (2) shows a circuit diagram using the four-terminal method. By separating the current application terminals T ₁ and T ₂ from the voltage application terminals T ₃ and T ₄ , the influence of contact resistance is eliminated. And high-precision measurement is possible.

  Next, the principle of detecting minute cracks occurring in the conductor pattern will be described. As shown in FIG. 3, a flexible printed circuit board 30 is provided with a conductor pattern 33 on the surface of a base film 31 via an adhesive 32, and a minute crack as indicated by a broken line A occurs in the conductor pattern 33. It shall be.

  Since these micro cracks are cracks generated between the crystals of the conductor metal, in the flat state or bending deformation in which the conductor pattern 33 is inward, the conductors in the micro crack portions are in close contact with each other. No change occurs in the electrical resistance value measured by the detecting means, and a microcrack cannot be detected. Further, even when cracks are generated in the entire thickness direction of the conductor pattern 33, there are a large number of contact points, so that the increase in the electrical resistance value is small, and the error of the measuring apparatus and the error of the conductor resistance are added up. In addition, the increase in the electrical resistance value becomes an error range, and cracks cannot be detected.

  Therefore, in the present invention, as shown in FIG. 4, by utilizing the characteristics of the flexible printed circuit board 30, the base film 31 is bent and deformed so as to be on the inside, so that a microcrack is shown as indicated by a broken line B. Will open and the number of contact points in the crack will be greatly reduced. Therefore, since the electrical resistance value of the conductor pattern 33 increases due to the decrease in the contact point, as described above, the presence or absence of microcracks can be easily and reliably measured by measuring the change in the electrical resistance value with the resistance value detecting means. It becomes possible to detect. Note that the deformation amount of the flexible printed circuit board 30 is such that the minute crack portion only needs to move by several microns, so that the normal flexible printed circuit board 30 does not generate a minute crack.

  Generally, in a flexible printed circuit board, there is a difference in bending strength between a portion having a cover film and a portion having no cover film, and particularly, bending stress is concentrated near the boundary of the cover film, and microcracks are likely to occur. In order to detect this micro crack, it is necessary to deform the conductor pattern in the direction in which the micro crack spreads. That is, by sucking from the base film side of the flexible printed circuit board, minute cracks generated in the conductor pattern spread and the electric resistance value changes, so that the presence or absence of a crack can be detected. According to this method, even when a reinforcing film or a glass epoxy laminate is bonded to the back surface of the base film, it is possible to detect microcracks.

  FIG. 5 shows a configuration in which the engraved portion 13 is recessed in the lower base 12 and the suction through hole 21 is provided in the engraved portion 13, and an adhesive 34 is partially applied to the conductor pattern 33 of the flexible printed circuit board 30. The cover film 35 is stuck through. As described above, since microcracks are likely to occur near the boundary of the cover film 35 indicated by the broken line C, the base film 31 is flexible in a state where the base film 31 is on the lower side in order to be deformed so that this portion is outside. The printed board 30 is placed on the lower base 12.

  The positioning guide plate 18 and the connection terminal 19 described in FIG. 1 are set so that the inspection location of the flexible printed circuit board 30 comes to the engraved portion 13 shown in FIG. When pushed down to the position, the upper base detection sensor is turned on, the switching valve is switched, and air suction starts from the suction through hole 21 of the lower base 12. As shown in FIG. 6, the flexible printed circuit board 30 is pulled by this suction, and the base film 31 side is bent so as to bulge into the engraved portion 13.

  Therefore, if there is a microcrack in the inspection location indicated by the broken line C, the microcrack generated in the flexible printed circuit board 30 (the broken line B portion in FIG. 4) spreads as described in FIG. Thus, the presence or absence of a crack can be detected by changing the electric resistance value of the conductor pattern 33.

  As pressure adjusting means other than suction, there is a method of applying pressure from the component mounting surface of the flexible printed circuit board 30. For example, as shown in FIG. 7, the upper base 11 is provided with an upper engraved portion 13 a and a pressurizing through hole 22, and the lower base 12 is provided with a lower engraved portion 13 b and a through hole 23. A discharge port of a pressurizing pump (not shown) is connected to the pressurizing through hole 22 of the upper base 11.

  As in the case of FIG. 5 and FIG. 6, the flexible printed circuit board 30 is positioned so that the inspection location is at the engraved portion 13 b shown in FIG. 7. In this state, if the upper base 11 is pushed down to a predetermined position, The upper base detection sensor is turned on and the switching valve is switched, and compressed air is injected from the pressurizing through hole 22 of the upper base 11. As shown in FIG. When pressed, the base film 31 is curved so that the engraved portion 13 bulges out.

  Although illustration is omitted, the same effect can be obtained by pressing the component mounting surface of the flexible printed circuit board 30 with a solid object such as foamed urethane instead of the above-described pressurization with air. is there. Solid objects such as foamed urethane can be used repeatedly, which can contribute to cost reduction of the inspection apparatus.

  In general, when mounting a component on a flexible printed circuit board, soldering is performed by solder reflow or solder-free, and the flexible printed circuit board and the mounted component are heated to a temperature higher than the solder melting temperature. The mounting component is fixed to the flexible printed board when the following occurs. The flexible printed circuit board and the mounted component both expand due to heating, and contract together due to subsequent cooling.

  In many cases, the linear expansion coefficient differs greatly between the mounted component and the flexible printed circuit board. For example, in a ceramic part, the linear expansion coefficient is about 7 ppm / ° C., whereas the linear expansion coefficient of copper used as a conductive pattern of a flexible printed circuit board is about 17 ppm / ° C., which is a considerable difference. . Therefore, at the time of lead-free soldering, the shrinkage difference between the ceramic component and copper is as follows. [17 (ppm) -7 (ppm)] × 240 (° C.) = 2400 (ppm).

  As shown in FIG. 9, when the mounting component 36 is soldered to the flexible printed board 30, the boundary portion between the cover film 35 and the solder 37 indicated by broken lines D and E has the weakest strength, and stress is applied to this portion. Concentrates and tends to generate microcracks.

  Therefore, as shown in FIG. 10, the engraving portion 13 is recessed in the lower base 12, and the through hole 21 for suction is provided in the engraving portion 13. For example, the inspection location indicated by the broken line D in FIG. If the flexible printed circuit board 30 is positioned so as to come to the engraving portion 13 and the upper base is pushed down to a predetermined position in this state, the switching valve is switched, and air is sucked from the suction through hole 21 of the lower base 12. Begins. As shown in FIG. 11, the flexible printed circuit board 30 is pulled by this suction, and the base film 31 side is bent so as to bulge into the engraved portion 13.

  Therefore, if a micro crack exists in the inspection location indicated by the broken line D, the micro crack generated in the flexible printed circuit board 30 spreads and the electric resistance value of the conductor pattern 33 changes, so that the crack The presence or absence can be detected. As described above, even if the inspection of the microcrack is impossible under the mounting component 36 in the past, the base film 31 side of the flexible printed circuit board 30 can be sucked into the engraved portion 13 easily and reliably. It is possible to detect the presence or absence of microcracks.

  Further, it may be deformed by applying pressure from the component mounting surface of the flexible printed circuit board 30. For example, as shown in FIG. 12, the upper base 11 is provided with an upper engraved portion 13 a and a pressurizing through hole 22, and the lower base 12 is provided with a lower engraved portion 13 b and a through hole 23. Then, if compressed air or compressed gas is injected from the pressurizing through hole 22 of the upper base 11, as shown in FIG. 13, the flexible printed circuit board 30 is pressed by the pressurization, and the base film 31 side is the engraved portion. Curved to bulge to 13b.

  In the present embodiment, the base film 31 of the flexible printed circuit board 30 is deformed into the engraved portion of the lower base with the lower base 12 side. On the contrary, the base film 31 is deformed into the upper base 11. You may make it deform | transform into the engraving part of the upper base 11 on the side. In addition, the flexible printed circuit board may be sandwiched by installing the upper base and the lower base in a vertical state or an inclined state instead of installing them in a horizontal state.

  Thus, the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

The conceptual diagram of Example 1 which shows Example 1. FIG. (1) Circuit diagram of the two-terminal method, (2) is a circuit diagram of the four-terminal method. Sectional drawing of a state with a flexible printed circuit board in explanatory drawing about the principle which detects a microcrack. Sectional drawing of the state which the explanatory view about the principle which detects a microcrack, and the flexible printed circuit board deform | transformed. Sectional drawing which shows Example 2 and a flexible printed circuit board is a flat state. Sectional drawing of the state which the flexible printed circuit board shown in FIG. 5 deform | transformed. Sectional drawing which shows the modification of Example 2 and a flexible printed circuit board is flat. Sectional drawing of the state which the flexible printed circuit board shown in FIG. 7 deform | transformed. Sectional drawing of the flexible printed circuit board which shows Example 3 and in which components were mounted. Sectional drawing of a state with the flexible printed circuit board shown in FIG. 9 flat. Sectional drawing of the state which the flexible printed circuit board shown in FIG. 9 deform | transformed. Sectional drawing of the state in which the modification of Example 3 is shown and a flexible printed circuit board is flat. Sectional drawing of the state which the flexible printed circuit board shown in FIG. 12 deform | transformed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electrical inspection apparatus 11 Upper base 12 Lower base 13 Carved part 13a Upper carved part 13b Lower carved part 14 Pressure adjusting means 15 Pipe connection part 16 Piping for suction 17 Suction pump 18 Positioning guide plate 19 Connection terminal 20 Upper base detection sensor 21 Through-hole for suction 21 Through-hole for pressurization 23 Through-hole 30 Flexible printed circuit board 31 Base film 32 Adhesive 33 Conductive pattern 34 Adhesive 35 Cover film 36 Mounting component 37 Solder

Claims (5)

  An upper base and a lower base for sandwiching the flexible printed circuit board, and a carved portion is provided in at least one of the upper base and the lower base, and a pressure adjusting means is provided in the carved portion; An electrical inspection apparatus for a flexible printed circuit board, comprising resistance value detection means for measuring an electrical resistance value of a conductor pattern provided on the flexible printed circuit board.   The flexible structure according to claim 1, wherein the lower base is provided with a guide plate for positioning a flexible printed circuit board, and further includes a connection terminal for conducting electricity to the conductor pattern and an upper base detection sensor. Testing equipment for printed circuit boards.   The flexible guide plate according to claim 1 or 2, wherein the positioning guide plate is provided so that a portion where a micro crack is likely to occur in the conductor pattern of the flexible printed circuit board is located in any one of the engraved portions. Testing equipment for printed circuit boards.   The pressure adjusting means is provided such that the back side of the flexible printed circuit board where a microcrack is likely to occur bulges into the engraved portion of either one of the bases and curves. 3. The electrical inspection apparatus for a flexible printed circuit board according to 3. When the flexible printed circuit board is sandwiched between the upper base and the lower base and a portion where a microcrack is likely to occur is deformed, the change in the electric resistance value of the conductor pattern is measured by the four-terminal method to detect the microcrack. 5. The electrical inspection apparatus for a flexible printed circuit board according to claim 1, wherein the resistance value detecting means is provided so as to detect presence or absence.

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