JP2016001666A - Jig for desmear treatment, printed wiring board and method for manufacturing printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a jig for a desmear treatment which makes possible to prevent the thickness of a base film from being partially reduced in a desmear treatment by plasma.SOLUTION: A jig for a desmear treatment is a jig for a desmear treatment on at least one aperture for interstitial via-hole use in a substrate for printed wiring board use, which has a circuit pattern and the at least one aperture for interstitial via-hole use. The jig comprises: a surface-cover board to be superposed on a surface of the substrate for printed wiring board use, in which a hole is formed in only a region surrounding the at least one aperture for interstitial via-hole use is opened; and a mechanism for positioning the surface-cover board, and the substrate for printed wiring board use to each other. The jig further comprises: a backside-cover board to be superposed on the backside of the substrate for printed wiring board use. In the jig, the substrate for printed wiring board use is held between and by the surface-cover board and the backside-cover board. The positioning mechanism may be arranged to perform the positioning of the backside-cover board in addition to the surface-cover board and the substrate for printed wiring board use.

Description

  The present invention relates to a desmear processing jig, a printed wiring board, and a printed wiring board manufacturing method.

  As a printed wiring board, a flexible printed wiring board in which circuit patterns are arranged on the front and back surfaces of a flexible substrate, a rigid printed wiring board using a rigid substrate, and a rigid flexible printed wiring in which a rigid substrate and a flexible substrate are laminated. Plates and the like are known.

  As shown in FIG. 6, in the flexible printed wiring board 101, circuit patterns 103 and 104 are laminated on the front and back surfaces of the base film 102, and the circuit patterns 103 and 104 have land portions 105 at opposing positions. A blind via hole 108 is formed in the laminate of the base film 102 and the land portion 105 on the surface side. The blind via hole 108 is filled with a conductive paste by printing, and the conductive paste is cured to form a blind via hole 107 and electrically connect the land portions 105 on the front and back surfaces (special feature). (See Kaisho 62-120096).

Japanese Patent Laid-Open No. 62-120096

  In such a conventional printed wiring board such as the flexible printed wiring board 101, smear (resin residue) generated when the blind via hole 108 is formed causes a failure such as poor conduction and insufficient adhesion. Therefore, after the formation of the blind via hole 108, before the conductive paste is filled into the blind via hole 108, the blind via hole 108 is subjected to a desmear process using plasma in order to remove the smear. . However, during this desmear process, since the base film 102 is exposed in an area where the circuit pattern 103 of the base film 102 is not laminated, the base film 102 is directly irradiated with plasma in this area. Since the base film 102 is formed of a resin such as polyimide, the thickness of the base film 102 is reduced in this region irradiated with plasma. As a result, the strength and insulation of the flexible printed wiring board 101 may be reduced.

  The present invention has been made based on the above circumstances, and provides a desmear processing jig and a method for manufacturing a printed wiring board that can prevent a reduction in the thickness of a part of a base film during plasma desmear processing. An object of the present invention is to provide a printed wiring board excellent in strength and insulation.

  A desmear processing jig according to an aspect of the present invention, which has been made to solve the above-described problems, is a printed wiring board substrate having a circuit pattern and one or more interstitial via holes. A hole desmearing jig, which is superimposed on the surface of the printed wiring board substrate and has a surface covering plate in which only a region surrounding the hole for the interstitial via hole is opened, and the surface covering plate and the above It is a desmear processing jig provided with an alignment mechanism with a printed wiring board substrate.

  Another method for manufacturing a printed wiring board according to an aspect of the present invention includes an insulating base film, a circuit pattern laminated on the front surface and / or the back surface of the base film, and one or more land portions of the circuit pattern. Forming a printed wiring board substrate having interstitial via hole holes formed on the surface, and a surface on the surface of the printed wiring board substrate where only the region surrounding the interstitial via hole holes is opened Printed wiring comprising a step of superimposing a covering plate, a step of desmearing an interstitial via hole through the opening of the surface covering plate, and a step of filling the interstitial via hole with a conductive paste It is a manufacturing method of a board.

  Still another printed wiring board according to one embodiment of the present invention is formed on an insulating base film, a circuit pattern laminated on the front surface and / or the back surface of the base film, and one or more land portions of the circuit pattern. A printed wiring board having interstitial via holes, wherein the interstitial via holes are formed of a conductive paste, and an average thickness of the base film in a region where the circuit patterns are laminated and a circuit pattern are laminated. This is a printed wiring board having a difference from the average thickness of the base film in a region that is not 3 μm or less.

  The desmear processing jig and the printed wiring board manufacturing method of the present invention can prevent a decrease in the thickness of a part of the base film during the desmear processing by plasma. Moreover, the printed wiring board of this invention is excellent in intensity | strength and insulation.

It is a typical end view at the time of use of the jig for a desmear processing concerning an embodiment of the present invention (a cut surface is a plane perpendicular to a substrate for printed wiring boards). FIG. 2 is a schematic plan view of a surface covering plate of the desmear processing jig of FIG. 1. FIG. 2 is a schematic plan view of the printed wiring board substrate of FIG. 1. FIG. 2 is a schematic plan view of a back surface coating plate of the desmear processing jig of FIG. 1. FIG. 2 is a schematic plan view of a support plate of the desmear processing jig of FIG. 1. It is typical sectional drawing which shows the printed wiring board manufactured using the jig | tool for a desmear process of FIG. It is a typical fragmentary end view explaining the manufacturing method of the printed wiring board using the jig | tool for a desmear process of FIG. FIG. 4B is a schematic partial end view illustrating the next step of FIG. 4A in the method for manufacturing a printed wiring board using the desmear processing jig of FIG. 1. It is a typical fragmentary end view explaining the next process of FIG. 4B of the manufacturing method of the printed wiring board using the jig | tool for a desmear process of FIG. It is a typical partial end view explaining the next process of FIG. 4C of the manufacturing method of the printed wiring board using the jig | tool for a desmear process of FIG. It is a typical partial end view explaining the next process of FIG. 4D of the manufacturing method of a printed wiring board using the jig for desmear processing of FIG. FIG. 2 is a schematic end view corresponding to FIG. 1 when a desmear process is performed on a printed wiring board substrate different from FIG. 1. It is a typical end view (a cut surface is a base film and a perpendicular surface) which shows the conventional printed wiring board.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

  A desmear processing jig according to an aspect of the present invention is a desmear processing jig for a hole for an interstitial via hole in a printed wiring board substrate having a circuit pattern and one or a plurality of interstitial via hole holes. A surface covering plate that is superimposed on the surface of the printed wiring board substrate and is open only in a region surrounding the interstitial via hole, and alignment between the surface covering plate and the printed wiring board substrate It is a jig for desmear processing provided with a mechanism.

  The desmear processing jig is disposed so as to overlap the surface of the printed wiring board substrate, and is a surface covering plate in which only an area surrounding the hole for the interstitial via hole is opened, and the surface covering plate and the printed wiring board And a mechanism for aligning the working substrate. Thereby, since the plasma irradiation to the region where the interstitial via hole is not formed can be prevented, the desmear processing jig can reliably prevent a reduction in the thickness of a part of the base film during the desmear processing.

  A back cover plate that is superimposed on the back surface of the printed wiring board substrate and sandwiches the printed wiring board substrate with the front cover plate; and the alignment mechanism is provided on the front cover plate and the printed wiring board substrate. In addition, alignment with the back cover plate may be performed. Thus, by sandwiching the printed wiring board substrate between the front surface coating plate and the back surface coating plate, the position of the printed wiring board substrate can be easily and reliably fixed with a simple configuration.

  A support plate superimposed on the back surface of the back surface coating plate is further provided, and the alignment mechanism includes pins protruding from the surface of the support plate on the front surface coating plate, the printed wiring board substrate, and the back surface coating plate. The alignment may be performed by inserting into each through-hole. In this way, printed wiring can be achieved by inserting the pins protruding from the surface of the support plate into the through holes formed in the surface covering plate, the printed wiring board substrate and the back surface covering plate. The position where the interstitial via hole of the board substrate is formed can be easily and reliably aligned with a simple configuration.

  One of the surface coating plate and the back coating plate may have a magnet, and the other may have a magnetic material or a magnet that is attracted to the magnet. Thus, one of the surface covering plate and the back surface covering plate has a magnet, and the other has a magnetic material or magnet that is attracted to the magnet, so that the surface covering plate and the back surface covering plate attracted by magnetic force A printed wiring board substrate is sandwiched between them. As a result, the position of the printed wiring board substrate can be reliably fixed, and the positional deviation of the printed wiring board substrate with respect to the position where the surface covering plate is opened can be made difficult to occur. As a result, it is possible to more reliably prevent plasma irradiation to a region where the interstitial via hole of the base film is not formed. Here, the “magnet” means a permanent magnet or an electromagnet having a magnetic force by supplying electric power.

  A printed wiring board manufacturing method according to an aspect of the present invention includes an insulating base film, a circuit pattern laminated on the front and / or back surface of the base film, and one or a plurality of land portions of the circuit pattern. Forming a printed wiring board substrate having interstitial via hole holes, and a surface covering plate in which only a region surrounding the interstitial via hole holes is opened on the surface of the printed wiring board substrate A printed wiring board comprising: a step of superimposing, a step of desmearing an interstitial via hole hole through an opening of the surface covering plate, and a step of filling the interstitial via hole hole with a conductive paste. It is a manufacturing method.

  The method for manufacturing the printed wiring board includes a step of superimposing a surface covering plate in which only a region surrounding the hole for interstitial via holes is opened on the surface of the printed wiring board substrate having holes for interstitial via holes; And a step of desmearing the interstitial via hole hole through the opening of the surface covering plate. As a result, it is possible to prevent the plasma irradiation to the region where the interstitial via hole is not formed, and therefore, by the method for manufacturing the printed wiring board, it is possible to reliably prevent a reduction in the thickness of a part of the base film during the desmear treatment, A printed wiring board having excellent insulation can be manufactured. Moreover, since the method for manufacturing the printed wiring board fills the interstitial via hole with the conductive paste to form the interstitial via hole, the interstitial via hole hole is densely filled with metal particles, A printed wiring board having excellent conductivity can be manufactured.

  A printed wiring board according to one aspect of the present invention includes an insulating base film, a circuit pattern laminated on the front surface and / or the back surface of the base film, and an interface formed on one or a plurality of land portions of the circuit pattern. A printed wiring board having a stitched via hole, wherein the interstitial via hole is formed of a conductive paste, and an area where the circuit pattern is laminated and an average thickness of the base film and a circuit pattern are not laminated A printed wiring board having a difference from the average thickness of the base film of 3 μm or less.

  Thus, the printed wiring board has a strength that is not more than the above upper limit because the difference between the average thickness of the region where the circuit pattern of the base film is laminated and the average thickness of the region where the circuit pattern is not laminated is less than or equal to the above upper limit. It is almost uniform and has excellent insulation. Here, the difference in average thickness means the absolute value of the difference between the two. In the printed wiring board, since the interstitial via hole is formed of a conductive paste, the interstitial via hole is densely filled with metal particles and has excellent conductivity.

  The arithmetic average roughness (Ra) of the inner wall of the circuit pattern connected to the side wall of the interstitial via hole is preferably 0.05 μm or more and 0.2 μm or less. As described above, the arithmetic average roughness (Ra) of the inner wall of the circuit pattern connected to the side wall of the interstitial via hole is within the above range, so that the connection surface between the interstitial via hole and the circuit pattern is appropriately smoothed. In addition, the connection strength and conductivity between the two can be reliably improved. In addition, arithmetic mean roughness (Ra) is measured based on JIS-B0601 (2001).

[Details of the embodiment of the present invention]
Hereinafter, a desmear processing jig, a printed wiring board, and a printed wiring board manufacturing method according to embodiments of the present invention will be described with reference to the drawings.

[Desmear processing jig]
The desmear processing jig of FIG. 1 includes the blind via hole in the printed circuit board substrate 10 having the first circuit pattern 13, the second circuit pattern 14, and a plurality of blind via hole holes 18 (interstitial via hole). It is a jig used when the desmear process of the hole 18 is performed. The desmear processing jig is superimposed on the surface of the printed wiring board substrate 10, and the surface covering plate 1 in which only the region surrounding the plurality of blind via hole holes 18 is opened, and the printed wiring board substrate 10. And a support plate 3 superimposed on the back surface of the back surface coating plate 2. In addition, the desmear processing jig includes an alignment mechanism that aligns the front cover plate 1, the printed wiring board substrate 10, and the back cover plate 2. Here, the “surface” of the printed wiring board substrate 10 means the surface on the side where the blind via hole 18 is opened, and does not mean the surface of the printed wiring board in use. The printed wiring board substrate 10 shown in FIG. 1 is in a state before the blind via hole 17 (interstitial via hole) is formed, that is, in a state before the conductive paste is filled in the blind via hole 18. It is a printed wiring board.

(Surface coated plate)
The surface covering plate 1 is superimposed on the surface of the printed wiring board substrate 10 when a desmear process is performed. As shown in FIG. 2A, the surface covering plate 1 is formed with a plurality of openings 4 penetrating on both sides only in a region surrounding the plurality of blind via hole holes 18 formed in the printed wiring board substrate 10. ing. Note that the printed wiring board substrate 10 shown in FIG. 2B is blinded so that the positional relationship between the opening 4 of the surface covering plate 1 and the blind via hole 18 formed in the printed wiring board substrate 10 can be easily understood. Only the first land portion 15 in which the via hole 18 is formed is illustrated, and other wiring patterns and the like formed on the surface side are not shown.

The surface covering plate 1 contains a magnetic material that is attracted to the magnet. That is, the surface covering plate 1 contains, for example, iron, nickel, cobalt, chromium, or an alloy thereof. Among these, magnetic stainless steel is preferable in terms of cost and durability.
Note that the entire surface covering plate 1 may be formed of these magnetic materials.

  Moreover, it is preferable that the surface (surface on the opposite side to the surface on the printed wiring board substrate 10 side) of the surface covering plate 1 is formed of metal. When the surface of the surface covering plate 1 is made of metal, the surface covering plate 1 is hardly affected by the plasma during the desmear treatment by plasma.

  As a minimum of average thickness of surface covering board 1, 30 micrometers is preferred and 40 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the surface covering plate 1 is preferably 100 μm, and more preferably 80 μm. If the average thickness of the surface covering plate 1 is less than the above lower limit, the surface covering plate 1 is likely to be deformed, which may make it difficult to handle. Conversely, if the average thickness of the surface covering plate 1 exceeds the upper limit, the pressure applied to the printed wiring board substrate 10 by the surface covering plate 1 may increase and the printed wiring board substrate 10 may be easily damaged. The surface covering plate 1 may be difficult to handle.

  The plurality of openings 4 of the surface covering plate 1 can be formed by cutting or etching. In order to form the opening 4 with high accuracy, it is preferably formed by etching.

  The average diameter (opening diameter) of the opening 4 is set to a size corresponding to the average diameter (diameter W1 described later) of the blind via hole 17 subjected to desmear processing. The average diameter of the opening 4 is preferably at least twice the average diameter of the blind via hole 17, more preferably at least 2.2 times. On the other hand, the average diameter of the opening 4 is preferably not more than 3 times the average diameter of the blind via hole 17, and more preferably not more than 2.8 times. If the average diameter of the openings 4 is less than the lower limit, the positional deviation in the printed wiring board manufacturing process cannot be absorbed, and the desmear treatment to the blind via hole 18 may be insufficient. On the contrary, if the average diameter of the opening 4 exceeds the upper limit, the positional deviation in the manufacturing process of the printed wiring board leads to the region of the base film 12 where the first land portion 15 of the printed wiring board substrate 10 is not formed. There is a possibility that the plasma irradiation cannot be sufficiently prevented.

(Back cover plate)
The said back surface coating | coated board 2 is superimposed on the back surface of the said board | substrate 10 for printed wiring boards, when performing a desmear process. And the back surface coating board 2 pinches | interposes the board | substrate 10 for printed wiring boards between the surface coating boards 1 superimposed on the surface of the board | substrate 10 for printed wiring boards.

  As shown in FIG. 2C, the back surface covering plate 2 has a plurality of magnets 6 on the front surface side, and sucks the surface covering plate 1 superimposed on the surface of the printed wiring board substrate 10. Thereby, the printed wiring board substrate 10 sandwiched between the front surface covering plate 1 and the back surface covering plate 2 is fixed.

  The magnets 6 of the back cover plate 2 may be arranged in any way as long as the front cover plate 1 can be attracted. However, from the viewpoint of improving the average adhesion, they are arranged in a plan view as shown in FIG. 2C. It is preferable to install.

When a magnet having a substantially circular shape in plan view is used as the magnet 6, the average diameter of the magnet 6 in plan view is preferably 3 mm or more and 10 mm or less. Moreover, the proportion of disposing the magnet 6 on the back cover plate 2, one or more preferably 10 or less per 100 cm ^2, it is preferable to arrange so that the arrangement density becomes uniform. Further, from the viewpoint of generating a uniform attracting force on the entire back cover plate 2, the entire back cover plate 2 may be a magnet. The material of the back cover plate 2 other than the magnet 6 is preferably a non-magnetic metal material such as aluminum.

  The magnet 6 is preferably a permanent magnet in terms of easy handling, but may be an electromagnet having magnetic force by supplying electric power. Of the permanent magnets, samarium cobalt magnets are preferred.

(Support plate)
The support plate 3 is superimposed on the back surface of the back surface coating plate 2 when the desmear process is performed. Therefore, when the desmear process is performed, the back surface coating plate 2, the printed wiring board substrate 10, and the front surface coating plate 1 are superimposed on the surface of the support plate 3 in this order from the side closer to the support plate 3.

  As shown in FIGS. 1 and 2D, the support plate 3 has a plurality of pins 5 that protrude in a direction perpendicular to the surface. The plurality of pins 5 are made of metal or hard resin.

(Positioning mechanism)
The positioning mechanism of the desmear processing jig includes a plurality of pins 5 projecting from the support plate 3 and a plurality of through holes drilled in the front surface coating plate 1 and the rear surface coating plate 2 as follows. Consists of.

  That is, when the surface covering plate 1 is superimposed on the surface side of the support plate 3, a plurality of first through holes 7 are formed at positions corresponding to the plurality of pins 5 protruding from the support plate 3. . In addition, a plurality of second through holes 8 are formed in the back surface covering plate 2 at positions corresponding to the plurality of pins 5 protruding from the support plate 3 when superimposed on the front surface side of the support plate 3. Yes. The printed wiring board substrate 10 also has a plurality of third through holes 11 formed at positions corresponding to the plurality of pins 5 projecting from the support plate 3 when superimposed on the surface side of the support plate 3. Has been. Therefore, when the back surface coating plate 2, the printed wiring board substrate 10 and the front surface coating plate 1 are superimposed on the surface of the support plate 3, as shown in FIG. 1, each pin 5 has the second through hole 8 and the third through hole. Inserted into the hole 11 and the first through hole 7, the back surface coating plate 2, the printed wiring board substrate 10 and the front surface coating plate 1 are aligned in the horizontal direction.

  Furthermore, when the back surface covering plate 2 attracts the front surface covering plate 1 by a magnetic force, the printed wiring board substrate 10 sandwiched between the front surface covering plate 1 and the back surface covering plate 2 becomes difficult to move in the horizontal direction, and the positional shift is caused. Is prevented.

[Printed wiring board]
Next, the printed wiring board manufactured using the desmear processing jig will be described. The printed wiring board in FIG. 3 is a so-called double-sided board and a flexible board, and is laminated on the base film 12 having insulation, the first circuit pattern 13 laminated on the surface of the base film 12, and the back surface of the base film 12. The second circuit pattern 14 is provided. The first circuit pattern 13 has a plurality of first land portions 15, and the second circuit pattern 14 has a plurality of second land portions 16 that face the first land portions 15. Further, the printed wiring board includes a plurality of blind via holes 17 (interstitial via holes) that penetrate the first land portion 15 and the base film 12 and are connected to the second land portion 16.

(Base film)
The base film 12 is composed of a sheet-like member having insulating properties and flexibility. Specifically, a resin film can be employed as the base film 12. As a material for this resin film, for example, polyimide, polyethylene terephthalate or the like is preferably used.

  The average thickness of the base film 12 is not particularly limited, but the lower limit of the average thickness of the base film 12 is preferably 5 μm and more preferably 10 μm. On the other hand, the upper limit of the average thickness of the base film 12 is preferably 100 μm, and more preferably 50 μm. There exists a possibility that the intensity | strength of the base film 12 may become inadequate that the average thickness of the said base film 12 is less than the said minimum. On the other hand, if the average thickness of the base film 12 exceeds the upper limit, there is a risk that the request for thinning may be violated.

  As an upper limit of the difference (absolute value) between the average thickness t1 of the base film 12 in the region where the first circuit pattern 13 is laminated and the average thickness t2 of the base film 12 in the region where the first circuit pattern 13 is not laminated 3 μm, more preferably 1.5 μm. On the other hand, the lower limit of the difference between the average thickness t1 and the average thickness t2 is preferably 0.1 μm, and more preferably 0.2 μm. When the difference in the average thickness exceeds the above upper limit, the insulation properties are lowered, and the strength of the printed wiring board is not uniform, and the durability may be impaired. On the other hand, if the difference in the average thickness is less than the lower limit, it is difficult to ensure the thickness accuracy of the base film, which may increase the cost.

(First circuit pattern)
The first circuit pattern 13 is formed in a desired planar shape (pattern) by etching a metal layer laminated on the surface of the base film 12. The first circuit pattern 13 can be formed of a conductive material, but is generally formed of copper, for example.

  The average thickness of the first circuit pattern 13 is not particularly limited, but the lower limit of the average thickness of the first circuit pattern 13 is preferably 2 μm and more preferably 5 μm. On the other hand, the upper limit of the average thickness of the first circuit pattern 13 is preferably 30 μm, and more preferably 20 μm. There exists a possibility that electroconductivity may become inadequate that the average thickness of the said 1st circuit pattern 13 is less than the said minimum. Conversely, when the average thickness of the first circuit pattern 13 exceeds the upper limit, flexibility may be impaired.

  The first land portion 15 of the first circuit pattern 13 has an outer shape (outer peripheral edge) formed in a substantially circular shape, and has a blind via hole 18 having a substantially circular shape in plan view in the center, and has a circular shape in plan view as a whole. Is provided. The outer peripheral edge and the inner peripheral edge of the first land portion 15 are formed concentrically. The blind via hole 18 is also continuous with the base film 12. Note that “substantially circular” means that the outer edge is an arc of 85% or more, and the ratio of the average distance from the center of the arc (average radius) to the radius at each arc-shaped point is 85% or more and 115% or less. It means that.

  The upper limit of the arithmetic average roughness (Ra) of the inner wall 15a connected to the side wall of the blind via hole 17 of the first land portion 15 is preferably 0.2 μm, and more preferably 0.15 μm. On the other hand, the lower limit of the arithmetic average roughness (Ra) of the inner wall 15a is preferably 0.05 μm, and more preferably 0.08 μm. When the arithmetic average roughness (Ra) of the inner wall 15a exceeds the upper limit, the filling property of the conductive paste into the blind via hole 18 may be lowered. Conversely, when the arithmetic average roughness (Ra) of the inner wall 15a is less than the lower limit, it may be difficult to manufacture the printed wiring board.

  The arithmetic average roughness (Ra) of the inner wall 15a of the first land portion 15 can be set to the above range by removing the smear of the blind via hole 18 by plasma desmear processing as will be described later.

  Note that the outer diameter W2 of the first land portion 15 (average diameter of the outer shape) and the diameter W1 of the blind via hole 18 (average diameter of the blind via hole 17) will be described later.

(Second circuit pattern)
Similar to the first circuit pattern 13, the second circuit pattern 14 is formed in a desired planar shape (pattern) by etching a metal layer laminated on the back surface of the base film 12. Similar to the first circuit pattern 13, the second circuit pattern 14 is formed of, for example, copper. The average thickness of the second circuit pattern 14 is not particularly limited, but the lower limit of the average thickness of the second circuit pattern 14 is preferably 2 μm and more preferably 5 μm. On the other hand, the upper limit of the average thickness of the second circuit pattern 14 is preferably 30 μm, and more preferably 20 μm. There exists a possibility that electroconductivity may become inadequate that the average thickness of the said 2nd circuit pattern 14 is less than the said minimum. Conversely, if the average thickness of the second circuit pattern 14 exceeds the upper limit, flexibility may be impaired.

  The second land portion 16 of the second circuit pattern 14 has a larger outer diameter than the blind via hole 18 and is disposed so as to close the opening on the back surface side of the base film 12. The second land portion 16 has a substantially circular outer shape. Specifically, the second land portion 16 is disposed concentrically with the first land portion 15 and the blind via hole 18.

  In addition, the outer diameter W3 (average outer diameter) of the second land portion 16 will be described later.

(Blind via hole)
The blind via hole 17 is intended to electrically connect the first land portion 15 and the second land portion 16 and has a conductor filled in the blind via hole 18. The blind via hole 17 has a substantially cylindrical shape, and is formed by curing after a conductive paste containing conductive particles is supplied into the blind via hole 18. Specifically, the conductive paste is supplied from the surface side into the blind via hole 18 by printing. For this reason, the bottom portion of the blind via hole 17 is in contact with the second land portion 16, whereby the blind via hole 17 and the second land portion 16 are electrically connected. Further, the side wall of the blind via hole 17 is in contact with the first land portion 15, whereby the blind via hole 17 and the first land portion 15 are electrically connected. The conductive paste overflows from the blind via hole 18 and covers a part of the surface of the first land portion 15. In addition, “substantially cylindrical” means a columnar body in which the upper surface and the lower surface are substantially circular, and the ratio of the average radius between the upper surface and the lower surface is 85% or more and 115% or less.

  The blind via hole 17 is formed by curing after a predetermined time has elapsed after the conductive paste is supplied. Since the conductive paste flows between the supply and the curing, the blind via hole 17 has a recess 17a near the center.

  The conductive paste contains conductive particles and a binder resin thereof. Metal particles are preferably used as the conductive particles, and silver, copper, nickel and the like are preferably used as the material of the metal particles.

  The conductive paste preferably includes conductive particles having a flat spherical shape (a shape obtained by flattening a sphere), whereby the conductive particles and the conductive particles easily contact the second land portion 16 or the first land portion 15. Excellent electrical conductivity. In the flat spherical shape, the length of the short axis is preferably 0.2 times or more and less than 1 time of the length of the long axis in the cross section including the short axis and the long axis. More preferably, it is less than 8 times. When the ratio of the length between the minor axis and the major axis is in the above range, a conductor having excellent conductivity can be obtained. As the flat conductive particles, those having an average particle diameter (average value of length of major axis) of 0.5 μm or more and 3 μm or less are preferably used. When the average particle diameter is in the above range, a conductor having excellent conductivity can be obtained. The conductive paste can also include a plurality of types of conductive particles having different average particle diameters.

  Further, when the conductive paste is cured, the conductive paste is heated. As a heating temperature of the conductive paste, a temperature at which conductive particles are bonded to each other is employed. For this reason, the conductive particles are bonded (melt bonded or sintered bonded) at the contact portion. That is, the conductor has a combination of conductive particles. In some cases, conductive particles that are not bonded exist.

  As the binder resin, epoxy resin, phenol resin, polyester, acrylic resin, melamine resin, polyimide, polyamideimide, phenoxy resin, or the like can be used. As the binder resin, a thermosetting resin is preferably used.

  Although the kind of epoxy resin is not specifically limited, For example, the bisphenol-type epoxy resin which uses bisphenol A, bisphenol S, bisphenol AD etc. as a raw material can be used. Further, naphthalene type epoxy resin, novolac type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, or the like can be used. Moreover, it is possible to use either a one-component epoxy resin or a two-component epoxy resin. Further, as the resin binder, it is also possible to use a one-component epoxy resin in which a microcapsule type curing agent is dispersed in an epoxy resin. In the conductive paste, butyl carbitol acetate or ethyl carbitol acetate can be used as a solvent in order to uniformly disperse the microcapsule type curing agent.

(About the diameter of each member)
The average diameter (diameter W1) of the blind via hole 17 is not particularly limited, but the lower limit of the diameter W1 of the blind via hole 17 is preferably 20 μm, more preferably 30 μm, and even more preferably 40 μm. On the other hand, the upper limit of the diameter W1 of the blind via hole 17 is preferably 150 μm, more preferably 120 μm, and even more preferably 100 μm. If the diameter W1 of the blind via hole 17 is less than the lower limit, it may be difficult to fill the conductor, or the connection strength between the blind via hole 17 and the second land portion 16 may not be sufficiently obtained. On the other hand, if the diameter W1 of the blind via hole 17 exceeds the upper limit, the blind via hole 17 becomes large, and there is a possibility that the outer diameter W3 of the second land portion 16 described later becomes too large. The average diameter of the blind via hole 17 means the average diameter of the cross section of the blind via hole 17 in a virtual plane including the laminated surface of the base film 12 and the second land portion 16.

  It is preferable that the first land portion 15 has an inner diameter that is substantially the same as the outer diameter of the blind via hole 18, and the outer diameter W <b> 2 (the average outer diameter) is larger than the outer diameter W <b> 3 of the second land portion 16. The outer diameter W2 of the first land portion 15 preferably has the following relationship with the diameter W1 of the blind via hole 17. That is, the outer diameter W2 of the first land portion 15 is preferably at least twice the diameter W1 of the blind via hole 17, more preferably at least 2.3 times, and even more preferably at least 2.5 times. Thereby, the printing yield of the conductive paste can be improved. On the other hand, the outer diameter W2 of the first land portion 15 is preferably 6 times or less, more preferably 5.5 times or less, and even more preferably 5 times or less the diameter W1 of the blind via hole 17. If the outer diameter W2 of the first land portion 15 exceeds the above upper limit, the first land portion 15 becomes unnecessarily too large, and the design of the first circuit pattern 13 may be difficult. The “outer shape” means the maximum outer shape in a planar projection shape parallel to the base film 12, and the “average diameter” means the maximum width of the outer shape and the width of the outer shape orthogonal to the maximum width direction. Mean value of

  Moreover, as a minimum of the radial direction width | variety (width | variety ((W2-W1) / 2) of an inner periphery and an outer periphery) of the 1st land part 15, 40 micrometers is preferable and 45 micrometers is more preferable. On the other hand, the upper limit of the radial width of the first land portion 15 is preferably 150 μm, and more preferably 125 μm. If the width in the radial direction of the first land portion 15 is less than the lower limit, the printing yield of the conductive paste may not be improved. On the contrary, if the radial width of the first land portion 15 exceeds the upper limit, the design of the first circuit pattern 13 may be difficult.

  Moreover, as a minimum of the outer diameter W2 of the 1st land part 15, 100 micrometers is preferable, 130 micrometers is more preferable, and 150 micrometers is further more preferable. On the other hand, the upper limit of the outer diameter W2 of the first land portion 15 is preferably 400 μm, more preferably 380 μm, and further preferably 350 μm. If the outer diameter W2 of the first land portion 15 is less than the lower limit, the printing yield of the conductive paste may be reduced. Conversely, if the outer diameter W2 of the first land portion 15 exceeds the upper limit, the design of the first circuit pattern 13 may be difficult.

  The outer diameter W3 (the average outer diameter) of the second land portion 16 is preferably not more than 4 times the diameter W1 of the blind via hole 17, and more preferably not more than 3 times. On the other hand, the outer diameter W3 of the second land portion 16 is preferably 1.2 times or more, and more preferably 1.5 times or more the diameter W1 of the blind via hole 17. If the outer diameter W3 of the second land portion 16 exceeds the above upper limit, it may be difficult to dispose the second land portion 16 at a narrow pitch. On the other hand, if the outer diameter W3 of the second land portion 16 is less than the lower limit, the adhesive force between the second circuit pattern 14 and the base film 12 in the second land portion 16 and the second land portion 16 and the blind via hole 17 There is a risk that the continuity of is insufficient.

  Further, the outer diameter W3 of the second land portion 16 is preferably 5/6 or less, more preferably 5/7 or less, of the outer diameter W2 of the first land portion 15. On the other hand, the outer diameter W3 of the second land portion 16 is preferably 1/6 or more of the outer diameter W2 of the first land portion 15, and more preferably 1/3 or more. By setting the ratio of the outer diameter W3 of the second land portion 16 and the outer diameter W2 of the first land portion 15 within the above range, the printing yield of the conductive paste can be improved and the pitch of the second land portion 16 can be reduced. .

  Moreover, as a minimum of the outer diameter W3 of the 2nd land part 16, 50 micrometers is preferable, 70 micrometers is more preferable, and 90 micrometers is further more preferable. On the other hand, the upper limit of the outer diameter W3 of the second land portion 16 is preferably 300 μm, more preferably 280 μm, and further preferably 250 μm. If the outer diameter W3 of the second land portion 16 is less than the lower limit, the adhesive force between the second circuit pattern 14 and the base film 12 in the second land portion 16 may be insufficient. Conversely, if the outer diameter W3 of the second land portion 16 exceeds the upper limit, it may be difficult to dispose the second land portion 16 at a narrow pitch.

  Further, as a lower limit of the ratio of the area of the first land portion 15 (the area of the annular plan view excluding the opening area of the blind via hole 18) to the area of the blind via hole 17 (the opening area of the blind via hole 18). Is preferably 4, and more preferably 5. On the other hand, the upper limit of the area ratio is preferably 50, and more preferably 25. By setting the area ratio within the above range, the printing yield of the conductive paste can be improved and the design of the first circuit pattern 13 can be facilitated.

  The lower limit of the ratio of the area of the first land portion 15 to the area of the second land portion 16 (the area in an annular plan view excluding the opening area of the blind via hole 18) is preferably 1.3, 1.8 is more preferable. On the other hand, the upper limit of the area ratio is preferably 5, and more preferably 4. By making the ratio of the areas in the above range, it is possible to improve both the printing yield of the conductive paste and the narrow pitch of the second land portions 16.

  The lower limit of the ratio of the area of the second land portion 16 (area in plan view) to the area of the blind via hole 17 (opening area of the blind via hole 18) is preferably 2.5 and more preferably 2.7. . On the other hand, the upper limit of the area ratio is preferably 20, and more preferably 7. If the area ratio is less than the lower limit, the adhesive force between the second circuit pattern 14 and the base film 12 in the second land portion 16 may be insufficient. On the contrary, if the area ratio exceeds the upper limit, it may be difficult to dispose the second land portions 16 at a narrow pitch.

[Method of manufacturing printed wiring board]
Next, a method for manufacturing the printed wiring board will be described with reference to FIG. The printed wiring board manufacturing method includes an insulating base film 12, a first circuit pattern 13 laminated on the surface of the base film 12, a second circuit pattern 14 laminated on the back surface of the base film 12, and Step of forming printed wiring board substrate 10 having blind via hole 18 (interstitial via hole) formed in a plurality of first lands 15 of one circuit pattern 13 (printed wiring board substrate forming step) A step of superimposing the surface covering plate 1 in which only the region surrounding the blind via hole 18 is opened on the surface of the printed wiring board substrate 10 (surface covering plate superimposing step), and the surface covering plate 1 A process of desmearing the blind via hole 18 through the opening 4 (desmear process), and And a step (conductive paste filling step) of filling the conductive paste de holes for via holes 18.

(PCB formation process for printed wiring boards)
In the printed wiring board substrate forming step, a metal film 19 is laminated on the front and back surfaces of the base film 12 as shown in FIG. 4A, and the metal layer 19 is processed as shown in FIG. A pattern 13 and a second circuit pattern 14 are formed.

  The method for laminating the metal layer 19 on the front and back surfaces of the base film 12 is not particularly limited. For example, an adhesion method in which a metal foil is bonded with an adhesive, a resin composition that is a material of the base film 12 on the metal foil. Casting method to be applied, sputtering / plating method in which a metal layer 19 is formed by electrolytic plating on a thin conductive layer (seed layer) having a thickness of several nanometers formed on the base film 12 by sputtering or vapor deposition, and the metal foil is heated. A laminating method or the like attached by a press can be used.

  When the first circuit pattern 13 and the second circuit pattern 14 are formed, the second land portion 16 of the second circuit pattern 14 and the first land portion 15 of the first circuit pattern 13 are formed at positions facing each other. Note that the shapes and the like of the second land portion 16 and the first land portion 15 are the same as described in the above-described printed wiring board, and thus the description thereof is omitted here. The formation of the first circuit pattern 13 and the formation of the second circuit pattern 14 can be performed simultaneously or separately.

  In the printed wiring board substrate forming step, the blind via hole 18 is then drilled as shown in FIG. 4C by irradiating the base film 12 with laser light using the annular first land portion 15 as a mask pattern. Thereby, the printed wiring board substrate 10 is formed.

(Surface coating board superposition process)
In the surface covering plate superimposing step, as shown in FIG. 4D, the printed wiring board substrate 10 is placed on the surface of the back surface covering plate 2, and the surface covering plate 1 is placed on the surface of the printed wiring board substrate 10. To do. At this time, the surface covering plate 1 is placed so that the opening 4 formed in the surface covering plate 1 surrounds the blind via hole 18 formed in the printed wiring board substrate 10.

(Desmear treatment process)
In the desmear process, plasma is irradiated from the surface side of the surface covering plate 1 superimposed on the printed wiring board substrate 10. At this time, the plasma reaches the blind via hole 18 through the opening 4 of the surface covering plate 1, and the residue in the blind via hole 18 is removed (desmeared). As a result, the inner wall 15a of the first land portion 15 and the bottom of the blind via hole 18 (the connecting surface connected to the blind via hole 18 in the surface of the second land portion 16) are smoothed. At this time, the region of the base film 12 exposed on the surface side of the printed wiring board substrate 10 has the surface coating plate 1 superimposed on the surface of the printed wiring board substrate 10, so that the plasma reaches Is prevented. Therefore, since the area of the base film 12 is not affected by the plasma, the thickness of the base film 12 in this area does not change. Note that a part of the inner wall of the base film 12 is also removed by the desmear treatment by the plasma, but the diameter of the portion of the blind via hole 18 surrounded by the base film 12 is thereby surrounded by the first land portion 15. Therefore, the anchor effect for the blind via hole 17 is aroused, and the blind via hole 17 becomes difficult to peel off.

(Conductive paste filling process)
In the conductive paste filling step, as shown in FIG. 4E, the conductive paste containing conductive particles is filled into the blind via hole hole 18 subjected to desmear treatment. After the conductive paste is filled, the blind via hole 17 is formed by allowing the conductive paste to flow for a certain period of time and then heating and curing the flowed conductive paste.

The conductive paste filled in the blind via hole 18 is preferably prepared so that the thixotropy index is preferably 0.40 or less, more preferably 0.25 or less. The thixotropy index is a value calculated by the following formula (1). Here, d1 and d2 mean shear rates, and d1 = 2s ⁻¹ and d2 = 20s ⁻¹ . η1 means the viscosity of the conductive paste at the shear rate d1, and η2 means the viscosity of the conductive paste at the shear rate d2.
Thixotropic index = log (η1 / η2) / log (d2 / d1) (1)

  Moreover, η1 is preferably 20 Pa · s or more and 300 Pa · s or less, and more preferably 40 Pa · s or more and 150 Pa · s or less. When η1 is in the above range, the conductive paste can be easily and surely filled into the blind via hole 18 to form a suitable blind via hole 17. Moreover, since the filling property to the surface of the 2nd land part 16 improves, the connection strength and electroconductivity of the blind via hole 17 and the 2nd land part 16 can be improved easily and reliably.

  As a method of filling the conductive paste into the hole 18 for the blind via hole, a conventionally known method can be adopted, for example, a screen printing method or an ink jet printing method can be adopted.

[advantage]
The desmear processing jig is disposed so as to overlap with the surface of the printed wiring board substrate 10, and the surface covering plate 1, the surface covering plate 1, and the printed circuit board in which only a region surrounding the blind via hole 18 is opened. And a mechanism for aligning the wiring board substrate 10. Thereby, the plasma irradiation to the area | region of the base film 12 in which the 1st land part 15 of the board | substrate 10 for printed wiring boards is not formed is prevented reliably, and the thickness reduction of a part of the base film 12 at the time of a desmear process is carried out. Is prevented.

  In addition, the desmear processing jig projects from the support plate 3 in the through-holes 8, 11, 7 provided in the back surface coating plate 2, the printed wiring board substrate 10, and the front surface coating plate 1, which overlap the support plate 3. The printed wiring board substrate 10 is aligned by inserting the pin 5 to be used and further attracting the front surface coating plate 1 and the rear surface coating plate 2 by magnetic force. Thereby, the position of the printed wiring board substrate 10 can be accurately adjusted with a low cost and simple configuration, and the blind via hole is prevented while preventing the plasma irradiation to the region where the first land portion 15 of the base film 12 is not formed. The desmear process of the hole 18 can be performed reliably.

  Further, the printed wiring board manufactured using the desmear processing jig has a small difference in thickness for each region of the base film 12, and is excellent in strength and insulation.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  That is, in the above-described embodiment, the front cover plate and the back cover plate are attracted by magnetic force, and the front cover plate is formed of a material attracted by magnetic force and the magnet is disposed on the back cover plate. Although the configuration has been described, it is not limited to this configuration. For example, the back cover plate may have a magnetic material that is attracted to the magnet and the magnet may be disposed on the front cover plate, or the magnet may be disposed on both the front cover plate and the back cover plate. It is good also as a structure.

  Moreover, in the said embodiment, although the structure which attracts | sucks a surface coating board and a back surface coating board by magnetic force was demonstrated as a structure which prevents the position shift of the board | substrate for printed wiring boards, it is not limited to this structure. Absent. For example, it is good also as a mechanical structure which the pressure which approaches a surface coating board to the back coating board side is added. Specifically, for example, a screw thread is provided at the tip of the pin protruding from the support plate, and after the back cover plate, the printed wiring board substrate and the surface cover plate are superimposed on the surface of the support plate, the tip portion of the pin The nut is fitted and tightened. From the viewpoint of preventing damage to the printed wiring board substrate, it is preferable to apply a pressure for bringing the front surface covering plate closer to the back surface covering plate through an elastic body such as a spring or rubber.

  Moreover, in the said embodiment, although the structure for which the pin for horizontal alignment was protrudingly provided in the support plate was demonstrated, the structure which performs horizontal alignment is not limited to this structure. . For example, a pin for horizontal alignment protrudes from the back cover plate, and this pin is inserted into each through hole of the front cover plate and printed circuit board substrate, so that the horizontal alignment is achieved. It may be performed.

  In addition, the desmear processing jig of the above embodiment uses the back surface coating plate and the support plate to align the front surface coating plate and the printed wiring board substrate, but there is no back surface coating plate and support plate. As long as the surface covering plate and the printed wiring board substrate can be aligned, the desmear processing jig does not need to include the back surface covering plate and the support plate. For example, a configuration in which the surface covering plate and the printed wiring board substrate are fixed by screws, or a configuration in which a pin is protruded at a position of the surface covering plate corresponding to the third through hole formed in the printed wiring board substrate. By doing so, it is possible to align the front surface covering plate and the printed wiring board substrate without the back surface covering plate and the supporting plate.

  Moreover, in the said embodiment, although demonstrated taking the case of the printed wiring board which has flexibility as an example of a printed wiring board, the scope of the present invention is a multilayer of a 1st circuit pattern, a base film, and a 2nd circuit pattern. The wiring board having a structure is not limited to this. A rigid printed wiring board can also be adopted as the printed wiring board. The printed wiring board can also be employed in a rigid flexible printed wiring board in which a flexible printed wiring board and a rigid printed wiring board are integrated, a build-up board having a multilayer structure, or the like.

  In the above embodiment, the printed wiring board having the blind via hole that conducts the land portion of the first circuit pattern and the second circuit pattern has been described. However, the interstitial via hole in the present invention conducts between the inner layers. A buried via hole or the like may be used.

  Further, the blind via hole is preferably formed in a substantially cylindrical shape as in the above embodiment, but in the manufacturing process, the blind via hole has a shape or constriction in which the blind via hole expands or contracts from the lower surface to the upper surface by desmear or the like. It may have a shape. The cross-sectional shape is not limited to a substantially circular shape, and may be a polygonal shape.

  Moreover, in the said embodiment, although the average diameter of the external shape of a 1st land part was demonstrated that is larger than the average diameter of the external shape of a 2nd land part, the magnitude | size of the external shape of a 1st land part and a 2nd land part is It is not particularly limited. For example, the average diameter of the outer diameter of the first land portion is smaller than the average diameter of the outer diameter of the second land portion, and the average diameter of the both outer diameters are also within the intended range of the present invention. . Further, the outer diameters of the first land portion and the second land portion are not limited to a substantially circular shape, and the outer shape is not particularly limited.

  Moreover, in the said embodiment, although the example which desmears the hole for blind via holes of the board | substrate for printed wiring boards by which a circuit pattern is laminated | stacked on the surface and back surface of a base film was demonstrated, the said desmear process jig | tool is a base It can also be used for a printed wiring board substrate in which a circuit pattern is laminated only on one side of the film. The printed wiring board shown in FIG. 5 is a multilayer printed wiring board composed of a first printed wiring board substrate 20 and a second printed wiring board substrate 21. In the first printed wiring board substrate 20, the first circuit pattern 23 is laminated on the surface of the base film 22, and the second circuit pattern 24 is laminated on the back surface. On the other hand, in the second printed wiring board substrate 21, the first circuit pattern 26 is laminated on the surface of the base film 23, but the circuit pattern is not laminated on the back surface of the base film 23. Also for the second printed wiring board substrate 21 on which the circuit pattern is laminated only on one side, the first land portion 27 and the base film 23 are penetrated by arranging the desmear processing jig as shown in FIG. The desmear process can be performed on the blind via hole 28 to be performed.

  The desmear processing jig and the printed wiring board manufacturing method of the present invention can prevent a decrease in the thickness of a part of the base film during the desmearing treatment by plasma, and the printed wiring board of the present invention is excellent in strength and insulation. For example, it can be suitably used for a flexible printed wiring board and the like.

DESCRIPTION OF SYMBOLS 1 Surface coating plate 2 Back surface coating plate 3 Support plate 4 Opening 5 Pin 6 Magnet 7 1st through-hole 8 2nd through-hole 10 Printed wiring board board | substrate 11 3rd through-hole 12, 22, 23 Base film 13, 24, 26 First circuit pattern 14, 25 Second circuit pattern 15, 27 First land portion 15a Inner wall 16 Second land portion 17 Blind via hole 17a Recess 18, 28 Blind via hole hole 19 Metal layer 20 First printed wiring board substrate 21 First 2 Printed wiring board substrate 101 Flexible printed wiring board 102 Base film 103, 104 Circuit pattern 105 Land portion 107 Blind via hole 108 Blind via hole

Claims (7)

A desmearing jig for the interstitial via hole in a printed circuit board substrate having a circuit pattern and one or more interstitial via hole;
A surface covering plate that is superimposed on the surface of the printed wiring board substrate and in which only a region surrounding the interstitial via hole is opened;
A desmear processing jig provided with an alignment mechanism between the surface covering plate and the printed wiring board substrate. A back cover plate that is superimposed on the back surface of the printed wiring board substrate and sandwiches the printed wiring board substrate with the surface coating plate;
The desmear processing jig according to claim 1, wherein the alignment mechanism performs alignment with a back surface coating plate in addition to the surface coating plate and the printed wiring board substrate. Further comprising a support plate superimposed on the back surface of the back cover plate,
The alignment mechanism performs the alignment by inserting a pin protruding from the surface of the support plate into a through-hole formed in each of the surface covering plate, the printed wiring board substrate and the back surface covering plate. The desmear processing jig according to claim 2 to be performed. One of the surface coating plate and the back coating plate has a magnet,
The desmear processing jig according to claim 2 or 3, wherein the other has a magnetic material or a magnet attracted to the magnet. Printed wiring board substrate having an insulating base film, a circuit pattern laminated on the front and / or back of the base film, and interstitial via hole holes formed in one or a plurality of land portions of the circuit pattern Forming a step;
A step of superimposing a surface covering plate on which only the region surrounding the hole for the interstitial via hole is opened on the surface of the printed wiring board substrate;
A step of desmearing the hole for the interstitial via hole through the opening of the surface covering plate;
And a step of filling the interstitial via hole with a conductive paste. A printed wiring board having an insulating base film, a circuit pattern laminated on the front and / or back surface of the base film, and interstitial via holes formed in one or a plurality of land portions of the circuit pattern,
The interstitial via hole is formed of a conductive paste,
The printed wiring board whose difference of the average thickness of the said base film of the area | region where the said circuit pattern is laminated | stacked and the average thickness of the said base film of the area | region where the circuit pattern is not laminated | stacked is 3 micrometers or less.   The printed wiring board according to claim 6, wherein the arithmetic average roughness (Ra) of the inner wall of the circuit pattern connected to the side wall of the interstitial via hole is 0.05 μm or more and 0.2 μm or less.

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