JP2007234826A - Flexible printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible printed wiring board in which a test coupon for measurement having high measuring reliability of characteristic impedance is arranged. <P>SOLUTION: In the flexible printed wiring board, a circuit pattern 30 is arranged on one surface. Further, the wiring board is provided with an insulation substrate 10 having flexibility, and test coupons for measurement 20a-20f arranged in a vertical direction against the moving direction of the insulation substrate 10 when etching the circuit pattern 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed wiring board, and more particularly to a flexible printed wiring board having a test coupon for measurement for measuring the impedance of the printed wiring board.

  In order to maintain the quality of the printed wiring board, it is necessary to measure the characteristic impedance of the conductor circuit. Conventionally, the characteristic impedance of a conductor circuit is measured by transmitting and receiving an electrical signal by bringing a probe connected to an impedance measuring machine into contact with a test coupon for measurement on a printed wiring board.

  In recent years, with an increase in processing speed of computers and the like, requirements for the performance of a printed wiring board through which signals flow have become stricter. For this reason, in order to accurately grasp the characteristic impedance that can occur in the printed wiring board, an invention is disclosed in which the conductor circuit width and the circuit width of the test coupon are matched to increase the measurement reliability of the characteristic impedance (for example, patents) Reference 1).

However, printed wiring boards using flexible flexible boards that have been increasingly used in response to demands for smaller, lighter, and thinner electronic devices have a thinner board thickness than rigid rigid boards. For this reason, when a pattern is formed by the subtra etching method, a difference in impedance may occur depending on the circuit direction in which the test coupon is arranged, the arrangement position of the circuit, and the front and back of the substrate.
JP 2005-197556 A

  An object of this invention is to provide the flexible printed wiring board which has arrange | positioned the test coupon for a measurement with high measurement reliability of characteristic impedance.

  According to one aspect of the present invention, a circuit pattern is disposed on one surface, a flexible insulating substrate, and a measurement test coupon disposed in a direction perpendicular to the direction of movement of the insulating substrate during etching of the circuit pattern And a flexible printed wiring board comprising:

  According to another aspect of the present invention, a circuit pattern is arranged on one surface, a flexible insulating substrate, and a test coupon for measurement arranged in a direction parallel to the moving direction of the insulating substrate during etching. And a flexible printed wiring board that is etched so that an etching solution does not collect on the surface of the insulating substrate on which the test coupon for measurement is disposed.

  ADVANTAGE OF THE INVENTION According to this invention, the flexible printed wiring board which has arrange | positioned the test coupon for a measurement with high measurement reliability of characteristic impedance can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in light of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  As shown in FIG. 1, a flexible printed wiring board according to an embodiment of the present invention has a circuit pattern 30 disposed on one surface, a flexible insulating substrate 10, and an insulating substrate 10 when the circuit pattern 30 is etched. Measuring test coupons 20a to 20f arranged in a direction perpendicular to the moving direction. The flexible printed wiring board according to the embodiment also includes test coupons for measurement 20g to 20o arranged in a direction parallel to the moving direction of the insulating substrate during etching.

  As shown in FIG. 2, the insulating substrate 10 has a circuit pattern 30 disposed on one surface and a ground 32 disposed on the other surface via an adhesive 40. A coverlay or resist protective layer 50 based on an insulating polyimide film or the like having excellent flexibility after bonding is bonded to the ground pattern 32 except for the connection terminal portion of the circuit pattern 30. It arrange | positions through the agent 42. FIG. The exposed conductors such as the connection terminals of the circuit pattern 30 that are not protected by the protective layer 50 are subjected to surface treatment by preflux treatment, hot air leveler (HAL), electrolytic solder plating, electroless solder plating, or the like. Is called.

  As the insulating substrate 10, a flexible substrate having flexibility such as a polyimide substrate, a polyethylene terephthalate (PET) substrate, a polyethylene naphthalate (PEN) substrate, or the like can be used. The thickness of the insulating substrate 10 can be 25 μm, 12.5 μm, 8 μm, 6 μm, or the like.

  The circuit pattern 30 is formed by patterning a rolled copper foil or an electrolytic copper foil on the insulating substrate 10. For the circuit pattern 30, a metal foil other than copper foil can be used as a conductor. The circuit pattern 30 may have a pattern width of 10 to 500 μm, preferably 50 to 300 μm, and more preferably 70 to 150 μm. The thickness of the circuit pattern 30 can be 33 μm, 18 μm, 12 μm, 9 μm, or the like. The pitch width of the circuit pattern 30 may be 10 to 500 μm, preferably 70 to 250 μm, and more preferably 100 to 200 μm. An auxiliary conductor (not shown) may be wired between the circuit patterns 30. The auxiliary conducting wire is connected to the ground 32 on the back surface through a through hole to prevent noise between the circuit patterns 30.

  The ground 32 is provided to prevent noise generated in the circuit pattern 30. The ground 32 preferably has a mesh structure so as not to impair the flexibility of the flexible printed wiring board. The pattern width of the ground 32 can employ 10 to 500 μm, preferably 70 to 250 μm, and more preferably 100 to 200 μm. The thickness of the ground 32 can be 33 μm, 18 μm, 12 μm, 9 μm, or the like.

  As shown in FIG. 3, the measurement test coupons 20a to 20o are a conductor measurement pad 22 that is in contact with a measuring instrument for measuring impedance, and a measurement circuit 24 that is connected to the measurement pad 22 and is a single signal line. The dummy pattern 26 is provided so as to sandwich the measurement circuit 24. The dummy pattern 26 is not grounded, and is arranged in order to obtain a finish equivalent to the circuit pattern 30 of the measurement circuit 24. The line width of the dummy pattern 26 is preferably matched to the line width of the circuit pattern 30.

  Measurement test coupons 20a to 20f arranged in a direction (TD direction) perpendicular to the moving direction of the insulating substrate 10 at the time of etching by the subtra etching method, and a direction parallel to the moving direction of the insulating substrate 10 at the time of etching ( The measurement test coupons 20g to 20o arranged in the (MD direction) have different formation conditions. The test coupons 20a to 20f for measurement may be oriented upward or downward on the circuit surface during etching. On the other hand, the test coupons for measurement 20g to 20o are formed with the direction of the circuit surface at the time of etching downward. The measurement test coupons 20g to 20o are etched with the circuit surface facing downward in order to prevent the etching liquid from being excessively etched due to accumulation of the etchant on the circuit surface. As an etchant, aqueous solutions of cupric chloride, ferric chloride, persulfates, hydrogen peroxide / sulfuric acid, alkali etchant, and the like can be used.

Example 1
The reason why the formation conditions of the measurement test coupons 20a to 20f and the measurement test coupons 20g to 20o are changed will be described based on the first embodiment. First, a flexible printed wiring board on which a measurement test coupon having a circuit width of the measurement circuit 24 of 75 μm is arranged is prepared. Specific numerical values of the configuration of the flexible printed wiring board will be described with reference to FIG. 2. A polyimide substrate having a thickness of 25 μm as the insulating substrate 10, a test coupon for measurement 20 a to 20 o and a thickness of 10 μm of the adhesive 40 as the ground 32. A copper foil having a thickness of 33 μm and a polyimide film having a thickness of 12.5 μm bonded to the protective layer 50 with a thickness of 20 μm of the adhesive 42 are used.

  The test coupons 20a to 20o for measurement are formed in the direction (TD direction or MD direction) with respect to the moving direction of the insulating substrate 10 at the time of etching by the subtra etching method, and by the etching solution addition method (circuit surface) at the time of etching. Upward or circuit surface downward). The reason for adding the etching solution at the time of etching is that the circuit surface is directed upward or the circuit surface is directed downward in order to compare whether the etching results of the measurement test coupons 20a to 20o are different when etching is performed with an etching machine. is there.

  FIG. 4 shows a graph showing the relationship between the circuit width and impedance of a test coupon for measurement formed by changing the above formation conditions. From the results shown in FIG. 4, when the test coupon for measurement is arranged in the MD direction with respect to the moving direction of the insulating substrate 10 at the time of etching, the circuit width is 50 to 60 μm, and the circuit width of other formation conditions Is significantly different from 75 μm ± 10 μm. Similarly, the impedance also shows a high value compared to other formation conditions, and is greatly different. That is, when the measurement test coupon is arranged in the MD direction with respect to the moving direction of the insulating substrate 10, the etching circuit accumulates when etching is performed with the circuit surface facing upward, whereby the measurement circuit 24 of the measurement test coupon is excessively etched. Impedance increases.

  Therefore, when the test coupon for measurement is arranged in the TD direction with respect to the moving direction of the insulating substrate 10, the circuit width tends to be the same and the impedance is the same regardless of whether the circuit surface during etching is upward or downward. In addition, when the test coupon for measurement is arranged in the MD direction with respect to the moving direction of the insulating substrate 10, the circuit width coincides with the case where the arrangement is in the TD direction by performing the circuit surface at the time of etching downward. The impedance also matches.

(Example 2)
The circuit width of the measurement circuit 24 of the test coupon for measurement is designed to be 70 μm so that the characteristic impedance is 55Ω, and the impedance is measured by changing the circuit pitch width from 60 μm to 250 μm.

  Specific numerical values of the configuration of the flexible printed wiring board to be used will be described with reference to FIG. 2. A polyimide substrate having a thickness of 25 μm as the insulating substrate 10, a test coupon for measurement 20 a to 20 o and a thickness of the adhesive 40 as the ground 32. A copper foil with a thickness of 18 μm bonded at a thickness of 10 μm and a polyimide film with a thickness of 12.5 μm bonded as a protective layer 50 with a thickness of 25 μm of an adhesive 42 are used.

  As a result of the example, a graph showing the relationship between the characteristic impedance and the circuit pitch width is shown in FIG. From the results shown in FIG. 5, when the circuit pitch width is smaller than 100 μm, the impedance tends to be smaller. On the other hand, even if the circuit pitch width is larger than 100 μm, the impedance does not change.

  Therefore, if the pitch width of the measurement circuit 24 and the dummy pattern 26 of the measurement test coupons 20a to 20o is 100 μm or more and the circuit pitch width of the circuit pattern 30 is 100 μm or more, the measurement test coupons 20a to 20o and the circuit pattern 30 are set. The impedances of these are matched. The pitch width of the measurement circuit 24 and the dummy pattern 26 and the pitch width of the circuit pattern 30 are preferably set to 250 μm as an upper limit and 200 μm as an upper limit in order to reduce the occupied area of the test coupons 20a to 20o for measurement. Is more preferable.

  According to the flexible printed wiring board according to the embodiment of the present invention, by arranging the measurement test coupon in the TD direction with respect to the moving direction of the insulating substrate 10, the impedance of the circuit pattern 30 and the measurement test coupon 20a are measured. Since the impedance of ˜20f matches, the impedance of the circuit pattern 30 can be managed by managing the impedance of the test coupons for measurement 20a to 20f.

  Further, according to the flexible printed wiring board according to the embodiment of the present invention, when the measurement test coupon is arranged in the MD direction with respect to the moving direction of the insulating substrate 10, the circuit surface is prevented from accumulating an etching solution during etching. Since the impedance of the circuit pattern 30 and the impedance of the measurement test coupons 20g to 20o coincide with each other by performing the etching downward, the impedance of the circuit pattern 30 is also managed by managing the impedance of the measurement test coupons 20g to 20o. It becomes possible to manage.

  Furthermore, according to the flexible printed wiring board according to the embodiment, the pitch width of the measurement circuit 24 and the dummy pattern 26 of the measurement test coupons 20a to 20o is set to 100 μm or more, and the circuit pitch width of the circuit pattern 30 is also set to 100 μm or more. For example, since the measured values of the impedances coincide with each other, the reliability of the impedance measurement by the measurement test coupons 20a to 20o can be increased.

(Other embodiments)
As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques should be apparent to those skilled in the art.

  For example, the test coupons 20a to 20o for measurement in the embodiment are all described in the same size, but the size may be appropriately changed according to the pattern width or pitch width of the nearby circuit pattern 30.

  In addition, the measurement test coupons 20g to 20o in the embodiment are described to be formed with the circuit surface at the time of etching facing downward, but if the etching solution does not accumulate on the circuit surface, the circuit surface is vertical. It does not matter if the circuit surface is not completely downward but inclined.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

It is a typical top view of the flexible printed wiring board concerning an embodiment of the invention. It is a typical sectional view of a flexible printed wiring board concerning an embodiment of the invention. It is a schematic diagram which shows the test coupon for a measurement which concerns on embodiment of this invention. It is a graph which shows the relationship between the circuit width and impedance of the test coupon for a measurement which concerns on embodiment of this invention. It is a graph which shows the relationship between the characteristic impedance and circuit pitch width of the test coupon for a measurement which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Insulating substrate 20a-20o ... Test coupon for measurement 22 ... Measurement pad 24 ... Measurement circuit 26 ... Dummy pattern 30 ... Circuit pattern 32 ... Ground 40, 42 ... Adhesive 50 ... Protective layer

Claims (5)

A circuit pattern is disposed on one surface, and a flexible insulating substrate;
A flexible printed wiring board, comprising: a test coupon for measurement arranged in a direction perpendicular to a moving direction of the insulating substrate during etching of the circuit pattern. A circuit pattern is disposed on one surface, and a flexible insulating substrate;
A test coupon for measurement arranged in a direction parallel to the direction of movement of the insulating substrate during etching, and etching is performed so that no etching solution accumulates on the surface of the insulating substrate on which the test coupon for measurement is arranged. A flexible printed wiring board characterized by the above. The measurement test coupon is:
A measuring pad of a conductor that contacts a measuring instrument for measuring impedance; and
A measurement circuit connected to the measurement pad and being a single signal line;
The flexible printed wiring board according to claim 1, further comprising: a non-grounded dummy pattern arranged so as to sandwich the measurement circuit.   The flexible printed wiring board according to claim 1, wherein a pitch width between the measurement circuit and the dummy pattern is 100 μm or more and 250 μm or less.   The flexible printed wiring board according to claim 1, wherein a pitch width of the circuit pattern is 100 μm or more and 250 μm or less.

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