JP2001135903A - Flexible wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible wiring board realizing inexpensive and reliable connection between through-holes corresponding to a conductor pattern of fine pitch, while decreasing the number of production steps. SOLUTION: A conductor patter 12 is formed at a pitch of P1 or less on the main surface of a thin flexible backing material 11. A conductor pattern 13 is formed at a pitch larger than P1 on the rear surface of the backing material. A through-hole 14 is made to be surrounded by the partial regions (land region at the end part) of the conductive patterns 12, 13 and shared on the surface and rear of the backing material. In the through-hole 14, a conductive material 15 having high viscosity screen printed from the major surface side of the flexible backing material 11 and a conductive material 16 having low viscosity screen printed from the rear surface side touch each other, thus constituting a via contact structure VIA 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a COF (Chip On Flexibl) in which a plurality of semiconductor chips are mounted on a substrate having a conductive pattern provided on a flexible thin insulating film.
e) The present invention relates to a flexible wiring board which is applied to a module, in particular, the conductive pattern is provided on both sides of a film and can be mounted at a high density.

[0002]

2. Description of the Related Art A flexible wiring board has an advantage that it is soft and deformable unlike a rigid wiring board. This is advantageous for high-density mounting of ICs and downsizing of modules. Flexible wiring boards are indispensable especially for miniaturization of various portable devices.

[0003] Many flexible substrates have conductive patterns printed on both surfaces, and a connection configuration using through holes is common. That is, a through hole is formed in the through hole land with a drill or the like, and through hole plating (copper plating) or the like is performed. Thereby, the predetermined conductive patterns on both sides of the substrate are connected.

[0004]

However, in the case of a conventional flexible substrate, there is a step (button plating) in which, when performing through-hole plating, plating is performed by removing only the through-hole lands by resist (button plating). On top is expensive. Further, if the plating step is performed without performing such a resist coating step, the width of the conductive pattern on the substrate becomes large, and it is difficult to form a fine pitch pattern.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to realize an inexpensive and reliable connection between through-holes which can cope with a fine pitch conductive pattern, has a small number of steps, and has a small number of steps. It is to provide a flexible wiring board.

[0006]

According to the flexible wiring board of the present invention, a first conductive pattern is formed on a main surface at a first pitch or less, and a second conductive pattern is formed on a back surface at a pitch larger than the first pitch. A flexible base material on which a pattern is formed, and the first and second conductive patterns are printed from the main surface side of the base material in a through hole of the base material shared so as to be surrounded by a partial region of each of the first and second conductive patterns. A via connection structure in which a first conductive material and a second conductive material printed from the back side are in contact with each other, wherein the second conductive material is compared with the first conductive material. It is characterized in that the material is formed of a material having a lower viscosity.

According to the above-mentioned flexible wiring board of the present invention, a via connection structure can be achieved only by printing on both sides using a thin and flexible base material. The main surface and the back surface are conductive patterns having different pitches, and have a configuration in which the viscosity of the conductive material is changed so as to be able to cope with this and to realize a reliable via connection structure.

Further, the flexible wiring board of the present invention comprises:
A first conductive pattern is formed on a main surface at a pitch equal to or less than a first pitch, and a second conductive pattern is formed on a back surface at a pitch larger than the first pitch.
The flexible substrate on which the conductive pattern is formed, and from the main surface side of the substrate in the through hole of the substrate shared so as to be surrounded by a partial region of each of the first and second conductive patterns. A via connection structure in which a printed first conductive material and a second conductive material printed from the back side are in contact with each other, wherein the first conductive material is a first conductive material;
The second conductive material has a second diameter larger than the first diameter and extends around a partial area of the first conductive pattern. It is characterized in that it extends around the partial area of the pattern.

According to the above-mentioned flexible wiring board of the present invention, a via connection structure is achieved by printing on both sides only by using a thin flexible base material. The conductive patterns have different pitches between the main surface and the rear surface, and have a configuration in which the diameter of the conductive material is changed so as to be able to cope with this and to realize a reliable via connection structure.

[0010] Further, the flexible wiring board of the present invention comprises:
A first conductive pattern is formed on a main surface at a pitch equal to or less than a first pitch, and a second conductive pattern is formed on a back surface at a pitch larger than the first pitch.
The flexible substrate on which the conductive pattern is formed, and from the main surface side of the substrate in the through hole of the substrate shared so as to be surrounded by a partial region of each of the first and second conductive patterns. A via connection structure in which a printed first conductive material and a second conductive material printed from the back side are in contact with each other, wherein the first conductive material is the second conductive pattern Is characterized.

According to the flexible wiring board of the present invention,
Utilizing a thin and flexible base material, the via connection structure is achieved only by printing on both sides. The conductive pattern has a different pitch between the main surface and the back surface, and the back surface side where the pitch is relatively not severe realizes a reliable via connection structure accompanying the formation of the conductive pattern.

[0012]

1 (a) and 1 (b) show a main structure of a flexible wiring board according to a first embodiment of the present invention, wherein FIG. 1 (a) is a plan view and FIG. 2) is a sectional view taken along line 1B-1B.

A conductive pattern 12 is formed on a main surface of a thin flexible substrate 11 of, for example, about 25 μm made of polyimide or the like. The conductive pattern 12 has an etching pattern of a copper foil having a pitch P1 or less for mounting a plurality of IC chips. Further, a conductive pattern 13 is formed on the back surface of the substrate 11. The conductive pattern 13 is required for applications such as connection between chips and has a copper foil etching pattern having a pitch larger than the pitch P1.

The thickness of the conductive patterns 12 and 13 is about 10 μm if it is a copper foil etching pattern using the above-described photolithography technique. Others
When a conductive pattern is formed by a printing technique such as a conductive paste, the thickness is about 30 μm.

A through hole, a so-called through hole 14, is formed in the flexible substrate 11 using a drill, a punch or the like. The through hole 14 is formed in the conductive pattern 1
Partial area of each of 2 and 13 (mainly land area at the end)
It is formed so as to be surrounded by, and is shared on the front and back of the substrate. The through hole 14 has a diameter of, for example, 0.2 to 0.3 mm.

In the through hole 14, a high-viscosity conductive material 15 screen-printed from the main surface side of the flexible base material 11 and a low-viscosity conductive material 16 screen-printed from the back side contact each other. I'm happy Thus, a via connection structure VIA1 is configured.

The conductive material 15 has a diameter of φA1 and extends around a portion of the conductive pattern 12. The conductive material 16 has a diameter of φB1 and extends around a portion of the conductive pattern 13. Here, φA1 and φB1
Are formed substantially equally. ΦA1 <φB due to viscosity
It may be 1, but it does not come outside the conductive pattern 13.

The conductive materials 15 and 16 may be a member mainly composed of Cu or a member mainly composed of Ag. If the amount of the organic solvent mixed in these members is small, the conductive material 15 having a high viscosity can be produced, and if the solvent is large, the conductive material 16 having a low viscosity can be produced.

The highly viscous conductive material 15 is formed of a fine pitch main surface conductive pattern 12 having a narrow pattern interval.
And high reliability. In addition, the conductive material 16 having low viscosity does not impair the reliability of forming the conductive pattern 13 on the back surface having a sufficient pattern pitch.

That is, since the conductive material 16 has a low viscosity, even if the printing bleeding is slightly larger than that of the conductive material 15, there is no danger of short-circuiting on the conductive pattern 13 on the back surface having a sufficient pattern pitch. It can be said that there are few.
Rather, by lowering the viscosity, the conductive material 16 surely enters the through hole 14 and combines with the conductive material 15, thereby contributing to the formation of the highly reliable via connection structure VIA1.

The diameter φD1 of the inner edge of each of the land regions of the conductive patterns 12 and 13 surrounding the through hole 14 is larger than the diameter φC1 of the through hole 14 of the flexible base material 11. Thereby, the conductive material 15
And 16 improve the filling and adhesion of the through hole 14 during printing.

According to the above configuration, the via connection structure VIA1
Can easily handle fine-pitch conductive patterns by screen printing on both sides. That is, inexpensive and highly reliable connection between the through holes 14 can be achieved without a step of forming and removing a resist.

FIGS. 2A and 2B show a main structure of a flexible wiring board according to a second embodiment of the present invention.
2A is a plan view, and FIG. 2B is a cross-sectional view taken along line 2B-2B in FIG. The same parts as those in FIG. 1 are denoted by the same reference numerals.

The second embodiment is different from the first embodiment in that the diameter φC2 of the through hole 14 of the flexible substrate 11 and the land regions of the conductive patterns 12 and 13 surrounding the through hole 14 are different from each other. That is, the diameters φD2 of the inner edges substantially match. That is, the through hole 14 is formed in the conductive pattern 12, 1.
3 are opened together with the conductive pattern by using a drill, a punch or the like in a partial area (mainly, an end land area).

The above configuration is an embodiment in the case where the pitch of the conductive patterns 12 on the main surface of the flexible base material 11 is stricter than in the first embodiment. Through hole 14
Must be opened as large as possible, and there is no room for forming a low step around the through hole 14 provided only by the main surface of the flexible base material 11. However, if the thicknesses of the flexible base material 11 and the conductive patterns 12 and 13 are reduced, the via connection structure VIA2 can be realized. That is, the via connection structure VIA2 is realized while maintaining reliability by screen-printing the highly viscous conductive material 15 and the low-viscosity conductive material 16 from the front and back of the flexible base material 11, respectively.

According to the above configuration, the via connection structure VIA2
Can easily handle fine-pitch conductive patterns by screen printing on both sides. That is, inexpensive and highly reliable connection between the through holes 14 can be achieved without a step of forming and removing a resist.

FIGS. 3A and 3B show a main structure of a flexible wiring board according to a third embodiment of the present invention.
FIG. 3A is a plan view, and FIG. 3B is a cross-sectional view taken along line 3B-3B in FIG.

A conductive pattern 32 is formed on the main surface of a thin flexible substrate 31 of, for example, about 25 μm made of polyimide or the like. The conductive pattern 32 has a copper foil etching pattern of a pitch P3 or less for mounting a plurality of IC chips. Further, a conductive pattern 33 is formed on the back surface of the base material 31. The conductive pattern 33 is required for applications such as connection between chips and has a copper foil etching pattern having a pitch larger than the pitch P3.

The thickness of the conductive patterns 32 and 33 is about 10 μm if it is a copper foil etching pattern using the above-described photolithography technique. Others
When a conductive pattern is formed by a printing technique such as a conductive paste, the thickness is about 30 μm.

A through hole, a so-called through hole 34, is formed in the flexible substrate 31 using a drill, a punch or the like. The through hole 34 is formed in the conductive pattern 3
Partial area of each of 2, 33 (mainly land area at the end)
It is formed so as to be surrounded by, and is shared on the front and back of the substrate. The through hole 34 has a diameter of, for example, 0.2 to 0.3 mm.

In the through hole 34, the conductive material 35 screen-printed from the main surface side of the flexible base material 31 and the conductive material 36 screen-printed from the back surface side are in contact with each other. This allows
A via connection structure VIA3 is configured.

The conductive material 35 has a diameter of φA 3 and extends around a part of the conductive pattern 32. The conductive material 36 has a diameter of φB3 larger than φA3 and extends around a partial region of the conductive pattern 33. The conductive material 35 or 36 is made of a member containing Cu as a main component or A
Members having g as a main component are conceivable, and these members are mixed with an organic solvent and applied to printing.

The conductive material 35 has a diameter of φA3 so as to cope with the formation of the fine pattern main surface having a narrow pattern interval on the conductive pattern 32. Since the conductive material 36 is formed on the conductive pattern 33 on the back surface having a sufficient pattern pitch, φB3 larger than φA3
The reliability is not impaired even if it is formed by the method.

That is, even if the conductive material 36 has a diameter of φB3 and the printing bleeding is slightly increased, the risk of a short circuit is small because the conductive material 36 is on the conductive pattern 33 on the back surface with a sufficient pattern pitch. I can say. Rather, since the conductive material 36 has a diameter of φB3, a larger matching margin is provided, and the conductive material 36 surely enters the through-hole 34 and combines with the conductive material 35 to form the highly reliable via connection structure VIA3. To contribute.

The diameter φD3 of the inner edge of each land area of the conductive patterns 32 and 33 surrounding the through hole 34 is larger than the diameter φC3 of the through hole 34 of the flexible base material 31. Thereby, the conductive material 35
And 36 improve the filling and adhesion into the through hole 34 during printing.

According to the above configuration, the via connection structure VIA3
Can easily handle fine-pitch conductive patterns by screen printing on both sides. That is, the connection between the through holes 34 at low cost and high reliability can be achieved without a step of forming and removing the resist. In the third embodiment, similarly to the first embodiment, the conductive material 35 may have a higher viscosity, and the conductive material 36 may have a lower viscosity as long as printing bleeding is allowable. .

FIGS. 4A and 4B show a main structure of a flexible wiring board according to a fourth embodiment of the present invention.
(A) is a plan view, and (b) is a cross-sectional view along line 4B-4B in (a). The same parts as those in FIG. 3 are denoted by the same reference numerals.

The fourth embodiment is different from the third embodiment in that the diameter φC4 of the through hole 34 of the flexible substrate 31 and the land areas of the conductive patterns 32 and 33 surrounding the through hole 34 are different. That is, the diameters φD4 of the inner edges substantially match. That is, the through holes 34 are formed in the conductive patterns 32 and 3.
3 are opened together with the conductive pattern by using a drill, a punch or the like in a partial area (mainly, an end land area).

The above configuration is an embodiment in the case where the pitch of the conductive patterns 32 on the main surface of the flexible base material 31 is stricter than in the first embodiment. Through hole 34
Must be opened as large as possible, and there is no room for creating a low step provided only by the main surface of the flexible base material 31 around the through hole 34. However, if the thicknesses of the flexible base material 31 and the conductive patterns 32 and 33 are reduced, the via connection structure VIA4 can be realized. That is, the conductive material 35 having a diameter from the front and back of the flexible base material 31 and the conductive material 36 having a diameter φB4 larger than φA4 are screen-printed, respectively.
A via connection structure VIA4 is realized while maintaining reliability.

According to the above configuration, the via connection structure VIA4
Can easily handle fine-pitch conductive patterns by screen printing on both sides. That is, the connection between the through holes 34 at low cost and high reliability can be achieved without a step of forming and removing the resist.

FIGS. 5A and 5B show a main structure of a flexible wiring board according to a fifth embodiment of the present invention.
(A) is a plan view, and (b) is a cross-sectional view along line 5B-5B in (a).

A conductive pattern 52 is formed on the main surface of a thin flexible substrate 51 of, for example, about 25 μm made of polyimide or the like. The conductive pattern 52 has a copper foil etching pattern of a pitch P5 or less for mounting a plurality of IC chips. Further, a conductive pattern 53 is formed on the back surface of the base material 51. The conductive pattern 53 is necessary for applications such as connection between chips and has a pattern with a pitch larger than the pitch P5.

The thickness of the conductive pattern 52 is about 10 μm if it is a copper foil etching pattern using the above-described photolithography technique. In addition, when forming a conductive pattern by printing technology such as conductive paste,
Its thickness is about 30 μm.

A through hole, a so-called through hole 54, is formed in the flexible substrate 51 by using a drill, a punch or the like. The through hole 54 is formed in the conductive pattern 5.
Partial area of each of 2 and 53 (mainly land area at the end)
It is formed so as to be surrounded by, and is shared on the front and back of the substrate. The through hole 54 has a diameter of, for example, 0.2 to 0.3 mm.

In the through hole 54, the conductive material 55 screen-printed from the main surface side of the flexible base material 51 and the conductive material 56 also serving as the conductive pattern 53 on the back surface are in contact with each other. This allows
A via connection structure VIA5 is formed.

The conductive material 55 has a predetermined diameter and extends around a part of the conductive pattern 12. The conductive material 56 also forms the conductive pattern 53. That is, the via connection structure VIA5 is formed simultaneously with the formation of the conductive pattern 53 by printing.

As the conductive materials 55 and 56, a member mainly composed of Cu or a member mainly composed of Ag can be considered. An organic solvent is mixed with these members to form a conductive material having a predetermined viscosity. Here, the same material is used for the conductive materials 55 and 56.

According to the above configuration, the conductive material 55 has a predetermined diameter and can cope with the formation of the fine pattern main surface having a narrow pattern interval on the conductive pattern 52, thereby providing high reliability. The conductive material 56 forms the conductive pattern 53 on the back surface having a sufficient pattern pitch and completes the via connection structure VIA5.

The diameter φD5 of the inner edge of the land area of the conductive pattern 52 surrounding the through hole 54 is larger than the diameter φC5 of the through hole 54 of the flexible base material 51.
Is big. Thereby, the conductive material 55 is filled into the through hole 54 at the time of printing and has good adhesion.

According to the above configuration, the via connection structure VIA5
Can easily handle fine pitch conductive patterns by printing on both sides of the flexible substrate 51. Moreover, the conductive material 56 simultaneously completes the formation of the conductive pattern 53 on the back surface with a sufficient pattern pitch and the via connection structure VIA5. As a result, the connection between the through holes 54 can be achieved with a small number of steps and at low cost and high reliability.

FIGS. 6A and 6B show a main structure of a flexible wiring board according to a sixth embodiment of the present invention.
(A) is a plan view, and (b) is a cross-sectional view along line 6B-6B in (a). The same parts as those in FIG. 5 are denoted by the same reference numerals.

The sixth embodiment is different from the fifth embodiment in that the diameter φC6 of the through hole 54 of the flexible substrate 51 and the diameter of the inner edge of the land area of the conductive pattern 52 surrounding the through hole 54 are different. φD6 is substantially the same. That is, the through-hole 54 is opened along with the conductive pattern using a drill, a punch, or the like in a partial area (mainly, an end land area) of the conductive pattern 52.

The above configuration is an embodiment in the case where the pitch of the conductive patterns 52 on the main surface of the flexible base material 51 is stricter than in the fifth embodiment. Through hole 54
Must be opened as much as possible, and there is no room for creating a low step provided around the main surface of the flexible base material 51 only around the through hole 54. However, if the thicknesses of the flexible base material 51 and the conductive pattern 52 are reduced, the via connection structure VIA6 can be realized. That is, the conductive material 55 from the front and back of the flexible base material 51,
56 are screen-printed, so that the conductive pattern 53 and the via connection structure VIA6 can be maintained while maintaining reliability.
To achieve.

According to each of the above embodiments, the via connection structure can easily cope with a fine pitch conductive pattern by screen printing on both sides. That is, an inexpensive and highly reliable connection between the through holes can be achieved without a step of forming and removing a resist.

[0055]

As described above, according to the flexible wiring board of the present invention, a via connection structure is achieved only by printing on both sides by using an extremely thin flexible base material. The conductive patterns have different pitches on the main surface and the back surface, and a via connection structure capable of coping with the conductive patterns is realized. That is, devising the viscosity of the conductive material, changing the diameter,
In order to further shorten the process, a via connection structure is realized together with the formation of the conductive pattern on the back surface side where the pitch is not strict.
This makes it possible to provide a flexible wiring board that can be used for fine pitch conductive patterns, has a small number of steps, and realizes inexpensive and reliable connection between through holes.

[Brief description of the drawings]

FIGS. 1A and 1B show a configuration of a main part of a flexible wiring board according to a first embodiment of the present invention, wherein FIG. 1A is a plan view and FIG. 1B is 1B-1B of FIG. It is sectional drawing which follows a line.

FIGS. 2A and 2B show a configuration of a main part of a flexible wiring board according to a second embodiment of the present invention, wherein FIG. 2A is a plan view and FIG. 2B is 2B-2B of FIG. It is sectional drawing which follows a line.

3 (a) and 3 (b) show a configuration of a main part of a flexible wiring board according to a third embodiment of the present invention, where (a) is a plan view and (b) is 3B-3B of (a). It is sectional drawing which follows a line.

FIGS. 4A and 4B show a configuration of a main part of a flexible wiring board according to a fourth embodiment of the present invention, wherein FIG. 4A is a plan view and FIG. 4B is 4B-4B of FIG. It is sectional drawing which follows a line.

FIGS. 5A and 5B show a configuration of a main part of a flexible wiring board according to a fifth embodiment of the present invention, wherein FIG. 5A is a plan view and FIG. 5B is 5B-5B of FIG. It is sectional drawing which follows a line.

FIGS. 6A and 6B show a configuration of a main part of a flexible wiring board according to a sixth embodiment of the present invention, wherein FIG. 6A is a plan view, and FIG. It is sectional drawing which follows a line.

[Explanation of symbols]

11, 31, 51 ... flexible base material 12, 13, 32, 33, 52, 53 ... conductive pattern 14, 34, 54 ... through hole 15 ... highly viscous conductive material 16 ... low viscous conductive material 35, 36 , 55, 56 ... conductive materials VIA1, VIA2, VIA3, VIA4, VIA5
VIA6: Via connection structure

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E351 AA04 BB01 BB30 BB31 BB49 CC13 DD04 DD05 DD52 DD54 EE03 GG11 5E317 AA24 BB03 BB12 BB14 CC22 CC25 CD27 CD32 GG16 5E338 AA02 AA12 BB13 BB25 CC01 CD11 EE23 EE

Claims (12)

[Claims] 1. A flexible base material having a first conductive pattern formed on a main surface at a pitch equal to or less than a first pitch, and a second conductive pattern formed on a back surface at a pitch larger than the first pitch, First conductive material printed from the main surface side of the base material and printed from the back surface side in the through hole of the base material shared so as to be surrounded by a partial region of each of the first and second conductive patterns A via connection structure in which the formed second conductive materials are in contact with each other, wherein the second conductive material is formed of a material having a lower viscosity than the first conductive material. A flexible wiring board. 2. The first conductive material has a first diameter and extends around a partial area of the first conductive pattern, and the second conductive material has a first diameter. The flexible wiring board according to claim 1, wherein the flexible wiring board has a larger second diameter and extends around a partial area of the second conductive pattern. 3. A diameter of an inner edge of a part of each of the first and second conductive patterns surrounding the through hole is larger than a diameter of the through hole of the base material. 2. The flexible wiring board according to 2. 4. The method according to claim 1, wherein the diameter of the through hole of the base material and the diameter of the inner edge of each of the first and second conductive patterns surrounding the through hole substantially match. The flexible wiring board according to claim 1 or 2, wherein: 5. A flexible base material having a first conductive pattern formed on a main surface at a pitch equal to or less than a first pitch, and a second conductive pattern formed on a back surface at a pitch larger than the first pitch, First conductive material printed from the main surface side of the base material and printed from the back surface side in the through hole of the base material shared so as to be surrounded by a partial region of each of the first and second conductive patterns And a via connection structure in which the formed second conductive materials are in contact with each other. The first conductive material has a first diameter and is provided around a partial region of the first conductive pattern. A flexible wiring board, wherein the second conductive material has a second diameter larger than the first diameter and extends around a partial area of the second conductive pattern. . 6. The second conductive material as compared with the first conductive material.
6. The flexible wiring board according to claim 5, wherein the conductive material is formed of a material having a lower viscosity. 7. A diameter of an inner edge of each of the first and second conductive patterns surrounding the through hole is larger than a diameter of the through hole of the base material. 6. The flexible wiring board according to 6. 8. The method according to claim 1, wherein a diameter of the through hole of the base material and a diameter of an inner edge in a partial region of each of the first and second conductive patterns surrounding the through hole substantially match. The flexible wiring board according to claim 5, wherein 9. A flexible base material having a first conductive pattern formed on a main surface at a pitch equal to or less than a first pitch, and a second conductive pattern formed on a back surface at a pitch larger than the first pitch; First conductive material printed from the main surface side of the base material and printed from the back surface side in the through hole of the base material shared so as to be surrounded by a partial region of each of the first and second conductive patterns A via connection structure in which the formed second conductive materials are in contact with each other, and the first conductive material constitutes the second conductive pattern. 10. The method according to claim 9, wherein the first conductive material and the second conductive material are made of the same substance.
The flexible wiring board as described. 11. A diameter of an inner edge of a partial region of the first conductive pattern surrounding the through hole is larger than a diameter of a through hole of the base material.
The flexible wiring board as described. 12. The method according to claim 9, wherein a diameter of the through hole of the base material and a diameter of an inner edge of a partial region of the first conductive pattern surrounding the through hole substantially match.
Or the flexible wiring board according to 10.