JP2002353615A - Method of establishing continuity between wiring patterns on both faces of flexible printed wiring board, and flexible printed wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible wiring board which provides a reliable continuity between the upper and the lower surface even when only one through hole can be formed for a pair of wiring patterns formed on the upper and the lower surface. SOLUTION: From a first wiring pattern 13 formed on one surface 12 of the flexible printed wiring board 10a, a through hole 14 is formed using a needle-like member. A conductive paste 15 is supplied to the through hole from the first wiring pattern side to fill the through hole with the paste 15, forming a first end part 16 of the conductive paste on the first wiring pattern side and a second end part 18 of the conductive paste on the other surface 17 side opposite from the first one. Then, On the other surface side, a second wiring pattern 19 electrically connected to the second end part of the conductive paste is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed wiring board used for assembling an electronic device having an electronic element mounted thereon.

[0002]

2. Description of the Related Art A circuit board constituting an electronic device is formed by forming a wiring pattern on an insulating substrate by printing using a conductive paste, etc.
An electronic device such as an IC circuit is attached. recent years,
As electronic devices have become smaller and more sophisticated, and display devices such as liquid crystal panel devices (LCDs) and plasma displays (PDPs) have become smaller and more colorized, the pitch of wiring patterns formed on the circuit board has increased. Is getting finer. Accordingly, as the circuit board, a wiring pattern is formed on both surfaces of the flexible insulating film with a conductive paste, and electrical conduction is provided between the wiring patterns formed on the front and back surfaces of the flexible insulating film by through holes. Flexible printed wiring boards that are electrically connected are often used.

In a conventional flexible printed wiring board,
As shown in FIG. 3, a wiring pattern 33 is formed on the upper surface 32 of the flexible insulating film 31 by a conductive paste by screen printing or the like, and a through hole 34 is formed on the wiring pattern 33 by a needle or the like from the upper surface 32 side. Then, the wiring pattern 3 is formed on the lower surface 35 with a conductive paste by screen printing or the like.
6, and the wiring pattern 3 on the upper surface 32 and the lower surface 35 is formed.
3, 36 are electrically connected.

In the above-mentioned flexible printed wiring board, a plurality of through holes for conducting between wiring patterns formed on the upper and lower surfaces are provided for a pair of wiring patterns on the upper and lower surfaces. Therefore, it is sufficient that at least one of the plurality of through-holes contributes to conduction between the upper and lower wiring patterns. In the conventional flexible printed wiring board having a low wiring pattern density, the conduction is almost certain. Have been obtained.

[0005]

However, in recent years, the pitch of the wiring pattern of the flexible printed wiring board has been reduced and the wiring pattern density has been increased, and one set of wiring patterns provided on the upper and lower surfaces of the flexible printed wiring board has been developed. On the other hand, only one through hole may be provided, and in such a case, there is a problem that conduction between the wiring patterns on the upper and lower surfaces cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. Even when only one through hole is provided for a set of wiring patterns on the upper and lower surfaces, the upper and lower surfaces can be reliably formed. An object of the present invention is to provide a flexible printed wiring board capable of obtaining conduction.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method of conducting between wiring patterns on both sides of a flexible printed wiring board on which wiring patterns for mounting electronic elements and the like are formed,
From the first wiring pattern formed on one surface of the flexible printed wiring board, a through hole is formed by piercing with a needle-like member, and the through hole is filled with a conductive paste from the first wiring pattern side. Forming a first end portion of the conductive paste on the first wiring pattern side, and forming a second end portion of the conductive paste on the other surface side opposite to the one surface; A second wiring pattern electrically connected to the second end.

The diameter d of the first end (unit: m)
m), and the distance between adjacent wiring patterns is L (unit: m).
m) is preferably formed in the range of 0.3 ≦ d ≦ 0.9 × L.

The present invention also relates to a flexible printed wiring board on which a wiring pattern for attaching an electronic element or the like is formed, wherein a needle-like member is formed on a first wiring pattern formed on one surface of the flexible printed wiring board. Forming a through-hole, filling the through-hole with a conductive paste from the first wiring pattern side, and forming a first conductive paste on the first wiring pattern side.
A second wiring that forms an end, forms a second end of the conductive paste on the other surface opposite to the one surface, and is electrically connected to the second end on the other surface. It has the first wiring pattern and the second wiring pattern, which are formed and made conductive.

The diameter d of the first end (unit: m)
m) is the distance between adjacent wiring patterns L (unit: m)
As m), those satisfying 0.3 ≦ d ≦ 0.9 × L are preferable.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B show an embodiment of a method for conducting wiring patterns on both sides of a flexible printed wiring board according to the present invention, wherein FIG. 1A is a cross-sectional view of a flexible insulating film, and FIG. FIG. 3C is a cross-sectional view of a flexible printed wiring board having a first wiring pattern formed thereon, FIG. 4C is a cross-sectional view showing a state where a through hole is formed by piercing the first wiring pattern of FIG.
(D) is a cross-sectional view showing a state where the conductive paste is filled in the through hole of (c), and (e) forms a second wiring pattern on the lower surface side second end of the conductive paste of (d). It is sectional drawing which shows the place where it did. 2A and 2B show an embodiment of a flexible printed wiring board formed by using the method of FIG. 1, wherein FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line AA of FIG.

As shown in FIG. 1, a method of conducting between wiring patterns on both sides of a flexible printed wiring board according to an embodiment of the present invention is a flexible printed wiring board, for example, an upper surface 12 which is one surface of a single-sided flexible printed wiring board 10a. A through-hole 14 is formed by piercing a needle-shaped member, for example, a needle, from above the first wiring pattern 13 formed on the first wiring pattern 13, and the through-hole 14 is filled with a conductive paste 15 from the first wiring pattern 13 side. Thus, the first end 16 of the conductive paste 15 is formed on the first wiring pattern 13 side, and the second end 18 of the conductive paste 15 is formed on the lower surface 17 which is the other surface opposite to the upper surface 12. And a second wiring pattern 1 electrically connected to the second end 18 on the lower surface 17 side.
9 are formed.

The flexible printed wiring board formed by using the method for conducting wiring patterns on both sides of the flexible printed wiring board according to the embodiment of the present invention is a flexible printed wiring board 10 shown in FIG.

Single-sided flexible printed wiring board 1
Oa may be formed by forming the first wiring pattern 13 on the flexible insulating film 11 by screen printing using a conductive paste.

The flexible insulating film 11 is made of, for example, polyester such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycarbonate, polyphenylene sulfide, etc. However, a polyester film is preferable in terms of bending resistance, temperature change, dimensional stability against external force, and adhesion of the conductive paste, and the thickness is preferably 10 to 50 μm.

The conductive paste 15 is made of carbon, gold,
A binder such as polyester resin, polyurethane resin, epoxy resin and acrylic resin contains 40 to 95% by weight of a conventionally known conductivity-imparting powder such as silver, copper, and nickel,
Those having a volume resistivity of 0.05 to 10 Ω · cm are preferred.

It should be noted that the first wiring pattern 13 or the second
The conductive paste used to form the wiring pattern 19 and the conductive paste 15 filled in the through holes 14 are:
Although they may be the same or different, they are preferably the same from the viewpoint of conduction stability due to compatibility.

When the diameter of the through hole 14 on the upper surface 12 side is smaller than 0.1 mm, the needle used for forming the through hole 14 is liable to be bent due to insufficient strength, and the diameter is smaller than 0.5 mm. If the size is large, the density of the wiring patterns on the single-sided flexible printed wiring board 10a is high, so that the needles also pierce the adjacent wiring patterns to make holes. Therefore, the diameter of the through hole 14 is preferably 0.1 mm to 0.5 mm, and the number of the through hole 14 is not particularly limited as long as it is one or more.

The planar shape of the first end 16 of the conductive paste 15 filled in the through hole 14 is not particularly limited, but is preferably a circular shape in consideration of printability and displacement.
When the number of the through holes 14 is one and the diameter of the first end 16 having a circular planar shape is d (unit: mm), the diameter d (unit: mm) of the first end 16 is: Considering shrinkage of the flexible insulating film 11 and displacement during printing, d ≧
0.3 (unit: mm) is preferable. The first end 16
Functions as a reservoir for the conductive paste 15.

The distance between adjacent wiring patterns is L
(Unit: mm), the diameter d of the first end portion 16 (unit: mm) in order to prevent the first end portion 16 from contacting the adjacent wiring pattern or the first end portion and conducting therewith. mm) is preferably d ≦ 0.9 × L (unit: mm). That is, the diameter of the first end 16 is 0.3 ≦ d ≦
0.9 × L (unit: mm) is preferable. The same applies to the case where the number of through holes 14 is plural.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given of embodiments of a method for conducting wiring patterns on both sides of a flexible printed wiring board according to the present invention and a flexible printed wiring board formed by using the method.

The thickness of the flexible insulating film is 25 μm.
m, PET of 250 mm square is used, and DW-250H-5 (product name, manufactured by Toyobo Co., Ltd.) is used as the conductive paste. As shown in FIG. 2, the first wiring pattern 2 having a width of 0.3 mm, a length of 100 mm, an interval of 0.6 mm, and a number of 300 is formed on the upper surface 22 of the PET 21.
3 is formed by screen printing using a conductive paste and then drying.

Next, at a position 5 mm on the right side of the drawing from the end 24 of the wiring pattern 23, at an intermediate position in the short direction,
A hole is punched from the upper surface 22 side of the PET 22 using a needle to form a through hole having a diameter of about 0.2 mm. The through-hole is filled with a conductive paste by screen printing to form a circular first end 25 having a diameter of about 0.5 mm on the upper surface 22 and a second end 27 on the lower surface 26. After drying.

Next, a second wiring pattern 28 is formed by screen printing using the same conductive paste and a screen plate as described above so as to overlap the second end 27 of the conductive paste filled in the through hole. Is dried after printing.

As described above, the first wiring pattern 23 on the upper surface 22 and the second wiring pattern 28 on the lower surface 26 are formed by the through holes filled with the conductive paste.
The flexible printed wiring board 20 with conduction therebetween is formed.

Next, a continuity test was performed between the first wiring pattern 23 on the upper surface 22 side of the flexible printed wiring board 20 and the second wiring pattern 28 on the lower surface 26 side.

After drilling on the through hole, the first end 2
When 5 is not provided, five conduction defects are detected,
In the case where the first end portion 25 was provided when the conductive paste was filled on the through-hole, no conduction failure was detected. By providing the first end portion 25, that is, the pool portion of the conductive paste, the through-hole is sufficiently filled with the conductive paste, and the second wiring pattern 28 is formed in the second end portion 2.
The reason for this is that it has come into sufficient contact with 7.

As described above, when the method of conducting between the wiring patterns on both sides of the flexible printed wiring board according to the embodiment of the present invention is used, the wiring pattern density is high. Even when only one through hole can be formed in the flexible printed wiring board, it is possible to reliably conduct between the wiring patterns on both sides of the single-sided flexible printed wiring board, and to provide a flexible printed wiring having a conductive pattern between the two sides on the both sides. A plate can be formed.

[0029]

According to the present invention, since the wiring patterns on both sides of the flexible printed wiring board can be reliably conducted, both surfaces of the flexible printed wiring board formed by the method of the present invention are electrically connected. It is not necessary to check whether or not the productivity is higher, and the productivity is improved.

[Brief description of the drawings]

1A and 1B show an embodiment of a method for conducting wiring patterns on both sides of a flexible printed wiring board according to the present invention, wherein FIG. 1A is a cross-sectional view of a flexible insulating film, and FIG. 1B is a flexible insulating film of FIG. FIG. 3C is a cross-sectional view of a flexible printed wiring board having a first wiring pattern formed thereon, FIG.
(D) is a cross-sectional view showing a state where a conductive paste is filled in the through-hole (c), and (e) is a cross-sectional view showing a state where a through-hole is formed by piercing the wiring pattern with a needle.
FIG. 3D is a cross-sectional view showing a state where a second wiring pattern is formed on the lower surface side second end of the conductive paste of FIG.

FIGS. 2A and 2B show an embodiment of a flexible printed wiring board formed by using the method of FIG. 1, wherein FIG. 2A is a plan view and FIG.
FIG. 3 is a sectional view taken along line AA of FIG.

3A and 3B show a conventional method of conducting between wiring patterns on both sides of a flexible printed wiring board, wherein FIG. 3A is a sectional view of a flexible insulating film, and FIG. FIG. 3C is a cross-sectional view of the flexible printed wiring board on which the wiring pattern is formed. FIG.
(D) is a cross-sectional view showing a state where a wiring pattern is formed on the end of the through hole on the side opposite to the wiring pattern of (c).

[Explanation of symbols]

 10, 20 flexible printed wiring board 10a single-sided flexible printed wiring board 11, 21, 31 flexible insulating film 12, 22, 32 upper surface 13, 23 first wiring pattern 14, 34 through hole 15 conductive paste 16, 25 First end 17, 26, 35 Lower surface 18, 27 Second end 19, 28 Second wiring pattern 24 End 33, 36 Wiring pattern

Claims (4)

[Claims] 1. A method of conducting a wiring pattern between both wiring patterns on both sides of a flexible printed wiring board on which a wiring pattern for mounting an electronic element or the like is formed, comprising: a first wiring pattern formed on one surface of the flexible printed wiring board; A through hole is formed by piercing with a needle-like member, and the through hole is filled with a conductive paste from the first wiring pattern side, and a first end of the conductive paste is filled on the first wiring pattern side. Forming a second end portion of the conductive paste on the other surface side opposite to the one surface, and forming a second wiring pattern electrically connected to the second end portion on the other surface side A method of conducting between wiring patterns on both surfaces of a flexible printed wiring board. 2. The diameter d of the first end (unit: mm).
Is the distance between adjacent wiring patterns is L (unit: mm)
2. The method according to claim 1, wherein the wiring pattern is formed in a range of 0.3 ≦ d ≦ 0.9 × L. 3. A flexible printed wiring board on which a wiring pattern for mounting an electronic element or the like is formed, wherein the first wiring pattern formed on one surface of the flexible printed wiring board is pierced by a needle-like member. Forming a through hole, filling the through hole with a conductive paste from the first wiring pattern side, forming a first end of the conductive paste on the first wiring pattern side, The second end of the conductive paste is formed on the other side of the opposite side, and the second wiring pattern electrically connected to the second end is formed on the other side of the conductive paste to conduct the first. A flexible printed wiring board comprising the wiring pattern of (1) and the second wiring pattern. 4. The diameter d of the first end (unit: mm).
Is the distance between adjacent wiring patterns L (unit: mm)
4. The flexible printed wiring board according to claim 3, wherein 0.3 ≦ d ≦ 0.9 × L.