JP2015196160A - Laser processing auxiliary seat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processing auxiliary sheet which is arranged between a work table and a substrate, can prevent irregular reflection of a laser beam on the surface of the work table to suppress the variation of a bore diameter, has proper gas permeability, and enables washing and removal of the waste produced by laser beam irradiation by a strong alkaline solution.SOLUTION: A laser processing auxiliary seat 20 is arranged, when a through-hole is formed by irradiating a substrate 10 with a laser beam from one face side of the substrate 10, on the other face side of the substrate 10, and is formed of a woven fabric or a nonwoven fabric, or a laminate material composed of the woven fabric and the nonwoven fabric, which is formed of a material fiber mainly composed of a biodegradable fiber.

Description

  The present invention relates to an auxiliary sheet for laser processing used when forming a through hole in a base material such as a copper clad laminate by laser irradiation.

Recently, electronic devices such as personal computers, smartphones, and portable game machines have been handled more compactly while the amount of information handled has increased. For this reason, a substrate such as a substrate of an electronic device is required to have a high density and a multi-layer, and a thick three-dimensional shape is increasing.
In the case where a through hole for a through hole is formed on a substrate, a method using a drill has been conventionally used. However, with the above-described high density and multilayering, a method of opening a through hole by irradiating a laser such as a carbon dioxide laser has been adopted (see Patent Documents 1 and 2). When a through-hole is opened in a base material by laser irradiation, the base material to be drilled is placed on a work table, and laser is irradiated from one surface (upper surface) side of the base material. The mounting surface on which the base material is mounted on the work table is formed by a protective plate made of a metal such as copper. During laser irradiation, the substrate is sucked and held on the work table through a number of holes formed in the protective plate.

JP 11-342492 A JP 2004-230391 A

  However, when a through hole is formed by irradiating the laser from one surface side of the base material held on the workbench as described above, the penetration formed on the other surface (lower surface) side of the base material It was found that the variation in the hole diameters was large. As a result of studying the cause, such variation in the hole diameter is caused by the fact that the laser that has passed through the formed through-hole is irregularly reflected on the surface of the protective plate of the workbench and irradiated to the other surface side of the substrate. It was thought to be caused by unintentionally processing the periphery of the formed through-hole.

Therefore, in order to suppress such variations in the hole diameter, a sheet or the like that absorbs the laser that has passed through the through hole is disposed between the work table and the base material, and irregular reflection of the laser occurs on the surface of the protective plate. Considered not to.
However, for example, when a general-purpose resin sheet is disposed between the work table and the base material, the resin sheet does not have air permeability, so that the base material cannot be sucked and held on the work table as described above. Therefore, the use of a nonwoven fabric made of general-purpose polyolefin fiber or polyethylene terephthalate (PET) fiber as a sheet having air permeability was examined. However, when such a nonwoven fabric is disposed between the work table and the base material, the base material can be sucked and held, but the nonwoven fabric is melted by the laser passing through the through hole, and the residue generated by the melting is lost in the through hole. A new problem arises in that it adheres to the inside and the periphery of the substrate and contaminates the base material. It was difficult to remove the residue generated by melting such a nonwoven fabric even by a substrate cleaning process (desmear process) using a strong alkaline solution, which is usually performed after laser irradiation.

  The present invention has been made in view of the above circumstances, and is arranged between a workbench and a substrate, can prevent irregular reflection of laser on the surface of the workbench, and can suppress variation in the hole diameter, and has a suitable air permeability. An object of the present invention is to provide an auxiliary sheet for laser processing that can be cleaned and removed with a strong alkaline solution of residue generated by laser irradiation.

The present invention has the following configuration.
[1] A raw material mainly composed of biodegradable fibers, disposed on the other surface side of the base material when a through hole is formed by irradiating the base material with a laser from the one surface side of the base material An auxiliary sheet for laser processing comprising a woven or non-woven fabric formed from fibers or a laminate of a woven fabric and a non-woven fabric.
[2] The auxiliary sheet for laser processing according to [1], comprising a nonwoven fabric, wherein the biodegradable fiber contains a heat-fusible biodegradable fiber.
[3] The auxiliary sheet for laser processing according to [1] or [2], containing a flame retardant.
[4] The auxiliary sheet for laser processing according to [3], comprising at least two layers and containing a flame retardant in at least one of the two layers located on the outermost surface.
[5] The auxiliary sheet for laser processing according to [4], wherein the flame retardant contains a guanidine flame retardant.
[6] The biodegradable fiber according to any one of [1] to [5], wherein the biodegradable fiber includes a non-heat-fusible biodegradable fiber, and the non-heat-fusible biodegradable fiber includes a cellulose fiber. Auxiliary sheet for laser processing.

  According to the present invention, it is disposed between the work table and the base material, and can prevent irregular reflection of the laser on the surface of the work table, thereby suppressing variation in the hole diameter, having appropriate air permeability, and by laser irradiation. It is possible to provide an auxiliary sheet for laser processing that can be cleaned and removed with a strong alkaline solution of the generated residue.

It is explanatory drawing explaining the method to irradiate a base material with a laser and to form a through-hole.

Hereinafter, the present invention will be described in detail.
The auxiliary sheet for laser processing of the present invention is disposed on the other surface side of the substrate when the substrate is irradiated with laser from one surface side of the substrate to form a through hole.
When a through hole is opened in a substrate by laser irradiation, for example, as shown in FIG. 1, the substrate 10 to be drilled is placed on a work table 11, and one surface (upper surface) side of the substrate 10 is placed. Then, the laser beam L condensed by the condenser lens 12 is irradiated. The laser processing auxiliary sheet 20 is disposed on the other surface (lower surface) side of the substrate 10 during such laser irradiation. In the example of illustration, it arrange | positions between the mounting surface 11a in which the base material 10 is mounted in the worktable 11, and the base material 10. FIG. In addition, the mounting surface 11a of the work table 11 in this example is formed by a protective plate 13 made of a metal such as copper. The protection plate 13 is formed with a number of unillustrated suction holes penetrating from one surface to the other surface, and the substrate 10 is sucked and held on the work table 11 through these many suction holes during laser irradiation. Is done.
Examples of the laser L include a carbon dioxide laser and a YAG laser. The base material is not particularly limited as long as it is a base material in which through holes such as through holes are formed. For example, a copper clad laminate having a structure in which an epoxy resin layer is sandwiched between two copper foils, two or more layers are used. Examples include a copper clad laminate having a copper foil layer and one or more resin layers.

  The auxiliary sheet for laser processing (hereinafter also referred to as “auxiliary sheet”) 20 is arranged on the side opposite to the side irradiated with laser with respect to the substrate 10 as described above, and passes through the formed through hole. Absorbs the laser. Thereby, the laser that has passed through the formed through-hole is irregularly reflected on the surface of the article (in this example, the protective plate 13 that constitutes the placement surface 11a) located on the other surface side of the base material 10. Is suppressed. Therefore, the irregularly reflected laser is irradiated on the other surface side of the base material 10, and the peripheral edge of the already formed through hole can be prevented from being unintentionally processed, and a through hole having no variation in hole diameter can be formed.

The auxiliary sheet 20 is made of any one of a woven fabric, a nonwoven fabric, and a laminated material of a woven fabric and a nonwoven fabric formed from raw fibers mainly composed of biodegradable fibers.
The nonwoven fabric may be a laminate of a plurality of layers of nonwoven fabric, and the woven fabric may be a laminate of a plurality of layers of woven fabric. The laminated material of a woven fabric and a nonwoven fabric is a laminated material formed with one or more layers of woven fabric and one or more layers of nonwoven fabric. The number of layers is not particularly limited as long as each of the woven fabric and the nonwoven fabric has one or more layers. There are no particular restrictions on the order of lamination.
The woven fabric and the non-woven fabric have appropriate air permeability. Therefore, even if the auxiliary sheet 20 made of any one of a woven fabric, a nonwoven fabric, and a laminated material of the woven fabric and the nonwoven fabric is disposed between the mounting surface 11a of the work table 11 and the base material 10, Does not interfere with suction holding.

Moreover, when the main component of the raw material fiber forming the auxiliary sheet 20 is a biodegradable fiber, when the substrate 10 is irradiated with a laser to form a through hole, a residue derived from the auxiliary sheet 20 is generated, Even if adhering to the inside or the periphery of the formed through-hole, the residue dissolves in the strong alkaline solution. Therefore, it can be easily removed by a substrate cleaning process using a strong alkaline solution.
When the through hole is formed in the base material 10 by laser irradiation, the residue derived from the auxiliary sheet 20 reaches the auxiliary sheet 20 and melts a part of the auxiliary sheet 20 through the formed through hole. To generate. If such debris can be easily removed by a substrate cleaning process using a strong alkaline solution performed after laser irradiation, the generation itself is not a problem. The substrate cleaning step using the strong alkaline solution is a step for removing waste derived from the substrate, which is originally caused by the dissolution of components (for example, a resin such as an epoxy resin) contained in the substrate 10. It is. If the residue derived from the auxiliary sheet 20 can also be removed by an existing substrate cleaning step for removing the residue derived from the substrate, it is preferable that a step for removing the residue derived from the auxiliary sheet 20 does not need to be performed separately. Examples of the strong alkaline solution include an aqueous solution in which sodium permanganate and sodium hydroxide are dissolved.

  The raw material fibers constituting the auxiliary sheet 20 are mainly composed of biodegradable fibers. The main component is a component contained in excess of 50% by mass. In this case, the content of the biodegradable fiber in the raw fiber is preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass. % Is particularly preferred. If the content of the biodegradable fiber in the raw fiber is as described above, even if a residue derived from the auxiliary sheet 20 is generated by laser irradiation, the residue is easily removed by a substrate cleaning process using a strong alkaline solution. it can. When the raw material fibers include fibers other than biodegradable fibers, examples of the fibers include metal fibers, carbon fibers, glass fibers, aramid fibers, and the like, which are difficult to melt due to laser irradiation and thus are less likely to cause residue. .

Examples of the biodegradable fiber that is a main component of the raw fiber forming the auxiliary sheet 20 include polybutylene succinate, poly (hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly (caprolactone / butylene succinate), poly (Butylene succinate / adipate), poly (butylene succinate / carbonate), poly (butylene adipate / terephthalate), polyethylene succinate, polylactic acid, polyhydroxybutyrate, polyglycolic acid, cellulose, cellulose acetate, etc. Examples include fibers made of materials.
One or more biodegradable materials constituting the biodegradable fiber are used. When there are two or more kinds, the biodegradable fiber may be a mixture of two or more kinds of fibers made of different biodegradable materials, or a composite fiber obtained by combining two or more kinds of biodegradable materials. Good. Moreover, even if the kind is the same, the mixture of 2 or more types of materials from which molecular weight etc. differ, composite fiber, etc. may be sufficient.
Examples of the fiber form of the composite fiber include a side-by-side structure and a core-sheath structure. The core-sheath structure may be a concentric core-sheath structure or an eccentric core-sheath structure.

The biodegradable fiber is at least partly melted by heating and acts as a binder component for bonding the fibers, and at least one of the heat-fusible biodegradable fiber. It can be classified into non-heat-fusible biodegradable fibers that do not melt even when heated to a temperature at which the part melts.
The biodegradable fiber that is the main component of the raw material fiber forming the auxiliary sheet 20 may be composed of only the heat-fusible biodegradable fiber or only the non-heat-fusible biodegradable fiber. It may be composed of a heat-fusible biodegradable fiber and a non-heat-fusible biodegradable fiber, and can be selected according to the form of the auxiliary sheet 20.

  When the auxiliary sheet 20 is made of a non-woven fabric, any non-woven fabric manufactured by any manufacturing method can be used. For example, a non-woven fabric in which raw fibers are bonded by a thermal bond method can be used. In that case, the biodegradable fiber that is the main component of the raw fibers is at least a heat-fusible biodegradable fiber that acts as a binder component. It is necessary to contain. Further, as the auxiliary sheet 20, for example, a nonwoven fabric in which raw fibers are bonded by a method other than the thermal bond method such as a nonwoven fabric in which raw fibers are bonded by a hydroentanglement method (spun lace method) can be used. The biodegradable fiber, which is the main component of the raw fiber, does not need to contain the heat-fusible biodegradable fiber, and may be composed of only the non-heat-fusible biodegradable fiber. Specific examples include a nonwoven fabric in which raw material fibers mainly composed of rayon fibers, which are biodegradable fibers, are bonded by a hydroentanglement method (spun lace method), a nonwoven fabric bonded by a needle punch method, and the like.

  For example, even when the auxiliary sheet 20 is made of a woven fabric, the biodegradable fiber that is the main component of the raw material fiber does not need to contain the heat-fusible biodegradable fiber, and the non-heat-fusible biodegradable fiber. You may be comprised only from a degradable fiber. Examples of the woven fabric used as the auxiliary sheet 20 include woven fabrics such as plain weave, satin weave and twill weave manufactured by a method using a known loom.

Examples of the material constituting the heat-fusible biodegradable fiber include polybutylene succinate, poly (hydroxybutyrate / hydroxyhexanoate), polycaprolactone, poly (caprolactone / Butylene succinate), poly (butylene succinate / adipate), poly (butylene succinate / carbonate), poly (butylene adipate / terephthalate), polyethylene succinate, polylactic acid, polyhydroxybutyrate, polyglycolic acid, cellulose acetate, etc. The biodegradable resin is preferable.
One or more biodegradable resins constituting the heat-fusible biodegradable fiber are used. In the case of two or more types, the heat-fusible biodegradable fiber is a composite fiber in which two or more types of biodegradable resins are combined even if it is a mixture of two or more types of fibers made of different biodegradable resins. It may be. Moreover, even if the kind is the same, the mixture and composite fiber of 2 or more types of resin from which molecular weight etc. differ may be sufficient.
Examples of the fiber form of the composite fiber include a side-by-side structure and a core-sheath structure. The core-sheath structure may be a concentric core-sheath structure or an eccentric core-sheath structure.

  Especially, as a heat-fusible biodegradable fiber, it is preferable to use a composite fiber from the point etc. which are excellent in the shape retention of a nonwoven fabric. As the composite fiber, a core-sheath type polylactic acid (polylactic acid having a low melting point (for example, about 130 ° C.) disposed as a sheath outside the core made of polylactic acid having a high melting point (for example, about 170 ° C.) ( PLA / PBS composite fiber having a core-sheath structure in which polybutylene succinate (PBS) having a melting point lower than that of polylactic acid is arranged as a sheath on the outside of the core made of PLA) composite fiber and polylactic acid is preferable. In such a core-sheath type composite fiber, at least a part of the resin constituting the sheath melts by heating in the manufacturing process of the auxiliary sheet, thereby exhibiting a binder action.

A cellulose fiber is mentioned as a non-heat-bondable biodegradable fiber.
Examples of cellulose fiber include pulp fiber, rayon fiber, cupra fiber, and cotton fiber. Of these, pulp fibers are preferable from the viewpoint of cost. Rayon fibers are preferable in that a nonwoven fabric can be produced by a spunlace method or the like that is difficult to employ when pulp fibers having a short fiber length are used.

  Examples of the pulp fiber include wood pulp (conifers, hardwoods), rug pulp, linter pulp, linen pulp, non-wood pulp such as straw, miso and husk pulp, and raw pulp such as waste paper pulp. As the raw material pulp, any of mechanical pulp (GP, RGP, TMP, etc.) and chemical pulp (sulfite pulp, kraft pulp, etc.) can be used. Especially, as a pulp fiber, the low density fluff pulp which crushed raw material pulp is preferable.

  As described above, the auxiliary sheet 20 has a woven fabric, a non-woven fabric, and a laminated material of the woven fabric and the non-woven fabric. However, it is easy to adjust the manufacturing point, the bulk density, the thickness, and the like. The nonwoven fabric is preferable because it is easy to obtain an auxiliary sheet 20 that can effectively prevent irregular reflection of laser on the surface of the work table 11. In addition, as described above, the nonwoven fabric can be produced by any production method, but the raw fibers are made by a thermal bond method using biodegradable fibers including heat-fusible biodegradable fibers. The bonded nonwoven fabric is easy to manufacture, excellent in shape retention, easy to adjust bulk density, thickness, etc., and therefore has appropriate air permeability and diffuse reflection of laser on the surface of the work table 11. From the point that the auxiliary sheet 20 which can prevent effectively is easy to be obtained. Further, for example, a non-woven fabric in which non-heat-fusible biodegradable fibers such as rayon fibers are bonded by a hydroentanglement method is preferable because it is easy to manufacture. The auxiliary sheet 20 may be composed of one layer or may be composed of two or more layers. Examples of the auxiliary sheet 20 composed of a nonwoven fabric include a form composed of one layer of nonwoven fabric and a form composed of two or more layers of nonwoven fabric.

When the auxiliary sheet 20 is disposed between the mounting surface 11 a of the work table 11 and the base material 10, the auxiliary sheet 20 has air permeability enough to suck and hold the base material 10 on the mounting surface 11 a. The air permeability of the auxiliary sheet is preferably 0.5 to 30.0 (cc / cm ² · sec) as Frazier air permeability Q (cc / cm ² · sec) based on JIS L1096 method A, and is preferably 1.0 to 20.0 (cc / cm ² · sec) is more preferable. If the Frazier permeability Q is equal to or higher than the lower limit of the above range, the substrate 10 can be reliably sucked and held. If it is below the upper limit of the said range, the irregular reflection of the laser on the surface (mounting surface) of the worktable 11 can be prevented reliably, and the variation in the diameter of the through-hole formed can be suppressed.

The thickness of the auxiliary sheet 20 is appropriately set according to the number of service life required for the auxiliary sheet 20, laser irradiation conditions, air permeability, and the like. For example, when the auxiliary sheet is discarded after each use, the thickness of the auxiliary sheet 20 measured by calipers is preferably 0.1 mm or more. On the other hand, when the auxiliary sheet 20 is discarded after being used a plurality of times, for example, 1.0 mm or more is preferable, and 1.2 mm or more is more preferable. If the thickness is too large, the air permeability of the auxiliary sheet 20 is lowered. Therefore, when the auxiliary sheet 20 is disposed between the mounting surface 11 a of the work table 11 and the base material 10, the suction of the base material 10 is performed. There is a possibility of preventing retention. Therefore, the thickness of the auxiliary sheet 20 is preferably, for example, 5.0 mm or less, and more preferably 3.0 mm or less.
The basis weight of the auxiliary sheet 20 is preferably ^{100~1000g / m 3, 300~800g / m} 3 and more preferably.
The apparent density of the auxiliary sheet 20 is obtained by calculation from the measured thickness and basis weight.

  In addition, when an auxiliary sheet consists of one layer, the thickness of an auxiliary sheet is the thickness of this one layer, and when it consists of two or more layers, the thickness of an auxiliary sheet is the total thickness of all the layers. Moreover, when it consists of one layer, the basic weight of an auxiliary sheet is the basic weight of this 1 layer, and when it consists of two or more layers, the basic weight of an auxiliary sheet is a total basic weight of all the layers.

The auxiliary sheet 20 preferably contains a flame retardant. As the type of flame retardant, known flame retardants such as organic flame retardants (for example, chlorine and bromine) and inorganic flame retardants can be used. As the form of the flame retardant, any form such as powder or liquid can be used.
Specific examples of the flame retardant include phosphorus-nitrogen condensates such as guanidine phosphate, carbamate phosphate, ammonium phosphate, melamine phosphate, and phosphazene. In addition, guanidine-based flame retardants other than guanidine phosphate, such as guanidine sulfamate, are also included.

As a method for adding the powdery flame retardant, a method of mixing in advance with the raw material fibers forming the auxiliary sheet can be employed. For example, when adopting an airlaid method in which fibers are three-dimensionally laminated at random as a method of forming a web when manufacturing a nonwoven fabric, when forming a web by the airlaid method, raw fiber and powder The method of laminating | stacking the mixture which mixed these flame retardants is mentioned.
As the powdery flame retardant used in such an addition method, for example, a flame retardant comprising a phosphorus / nitrogen condensate is preferable. The flame retardant begins to dissolve phosphorus at the flame temperature, exerts a flame retardant action by a mechanism that promotes oxygen thinning with nitrogen gas by covering the fiber surface, and further with nitrogen gas.

In the case of using a liquid flame retardant, a method of spraying on the raw fiber, nonwoven fabric or woven fabric; a method of immersing the nonwoven fabric or woven fabric in a liquid flame retardant, and the like can be mentioned.
Examples of the liquid flame retardant used in such an addition method include a flame retardant solution containing a guanidine-based flame retardant described later.
Moreover, you may knead | mix a flame retardant beforehand to the fiber which comprises a nonwoven fabric.

  When the auxiliary sheet 20 contains a flame retardant, the auxiliary sheet 20 is disposed between the mounting surface 11a of the work table 11 and the base material 10 and the base material 10 is subjected to laser irradiation. Even if a fire breaks out due to this energy, it is possible to suppress the spread of fire to the auxiliary sheet 20. The auxiliary sheet 20 preferably has flame retardancy that passes, for example, UL94HBF (flame retardancy test).

The content of the flame retardant in the auxiliary sheet 20 can be appropriately set according to the type of the flame retardant, but is about 3 to 15% by mass, for example, when the mass of the auxiliary sheet 20 is 100% by mass.
In addition, when using the solution which the flame retardant melt | dissolved, content of a flame retardant is the net amount of a flame retardant.

  As described above, the auxiliary sheet 20 may be composed of one layer or two or more layers. For example, when the auxiliary sheet 20 contains a flame retardant, the amount of the flame retardant used is reduced. In view of effectively imparting flame retardancy, the auxiliary sheet is preferably composed of at least two layers. If it is an auxiliary sheet composed of a plurality of layers of non-woven fabric, it is possible to adopt a form in which at least one of the two layers located on the outermost surface contains a flame retardant, and the other layers do not contain a flame retardant. If the flame retardant is present at least on the surface side, it is possible to prevent the spread of fire from the surface side. Therefore, by including a flame retardant in at least one of the two layers located on the outermost surface, a small amount of the flame retardant used, for example, about 3 to 6% by mass as the content of the flame retardant in the auxiliary sheet , Flame retardancy can be obtained. Each of the plurality of layers is formed of raw fiber mainly composed of biodegradable fiber.

When the auxiliary sheet 20 is disposed between the mounting surface 11 a of the work table 11 and the base material 10, the auxiliary sheet 20 is disposed so that the layer containing the flame retardant contacts the base material 10. That is, when the flame retardant is contained in only one of the two layers located on the outermost surface, the auxiliary sheet 20 is disposed on the work table 11 so that the layer contacts the base material 10. When the flame retardant is contained in the two layers located on the outermost surface, the auxiliary sheet 20 may be disposed so that either layer contacts the base material 10.
In addition, when an auxiliary | assistant sheet | seat consists of two or more layers, it is not necessary to include a flame retardant in layers other than the layer located in the outermost surface, and it can select according to the flame retardance requested | required.

As a specific form when the auxiliary sheet 20 is composed of a plurality of layers of non-woven fabric, it has a non-woven fabric obtained by bonding an air laid web formed by an air laid method as a middle layer, and at least one surface side of the middle layer Further, a two-layer configuration or a three-layer configuration in which a surface layer made of a nonwoven fabric is provided is preferable. The surface layer preferably contains a flame retardant.
The airlaid method is easy to manufacture, and it is easy to adjust the bulk density and thickness of the nonwoven fabric to be manufactured. Therefore, it has appropriate air permeability and effectively prevents the irregular reflection of laser on the surface of the work table 11. The auxiliary sheet 20 that can be produced is easier to manufacture. The airlaid web constituting the middle layer may be composed only of heat-fusible biodegradable fibers, but from the standpoint that an auxiliary sheet having a sufficient thickness as an auxiliary sheet can be easily obtained. It is preferable to consist of a degradable fiber and a non-heat-fusible biodegradable fiber.

  As in this example, when the fibers are bonded by the thermal bond method, the content of the heat-fusible biodegradable fiber in the biodegradable fiber is 5% by mass or more from the viewpoint of sufficiently bonding the fibers. It is preferable that it is 8 mass% or more. The content of the heat-fusible biodegradable fiber in the biodegradable fiber may be 100% by mass, but as described above, the biodegradable fiber contains non-heat-fusible biodegradable fiber. It is preferable to do. When the biodegradable fiber is composed of a heat-fusible biodegradable fiber and a non-heat-fusible biodegradable fiber, the content of the heat-fusible biodegradable fiber in the biodegradable fiber is 90 masses. % Or less, and more preferably 80% by mass or less.

  That is, in the total amount of the heat-fusible biodegradable fiber and the non-heat-fusible biodegradable fiber, the content of the heat-fusible biodegradable fiber is preferably 5% by mass or more. More preferably, the content of non-heat-fusible biodegradable fiber is 95% by mass or less, and preferably 92% by mass or less. The content of the heat-fusible biodegradable fiber is preferably 90% by mass or less, more preferably 80% by mass or less, and the content of the non-heat-fusible biodegradable fiber is It is preferably 10% by mass or more, and more preferably 20% by mass or more.

The thickness of each surface layer is preferably 5 to 50% and more preferably 10 to 40% when the thickness of the auxiliary sheet 20 is 100%. If it is more than the lower limit of the said range, it will be easy to provide sufficient flame retardance to an auxiliary sheet by adding a flame retardant to a surface layer. If it is below the upper limit of the said range, addition of an excessive quantity of a flame retardant can be suppressed.
Although a flame retardant does not need to be added to the middle layer, a flame retardant may be added to the middle layer as needed when higher flame retardancy is required.
The basis weight of each surface layer is preferably 2 to 50% and more preferably 5 to 40% when the basis weight of the auxiliary sheet 20 is 100%.

Further, if the thickness of each surface layer is particularly preferably 30% or less of the thickness of the auxiliary sheet 20, the nonwoven fabric constituting the surface layer is thin, and therefore the binder resin latex in which the nonwoven fabric is not biodegradable is used. Even if the fibers are bonded by the chemical bond method used, the amount of these binder resins in the entire auxiliary sheet is small. Specifically, the proportion of the binder resin contained in the surface layer in 100% by mass of the auxiliary sheet is usually 5% by mass or less. Therefore, even when laser irradiation is performed using an auxiliary sheet in which these binder resins are included in the surface layer, the residue of the binder resin hardly adheres to the inside or the periphery of the through-hole of the base material. Can be easily removed by washing with a strong alkaline solution.
Examples of the binder resin latex having no biodegradability include ethylene / vinyl acetate copolymer latex and butadiene copolymer latex.

  As the nonwoven fabric constituting the surface layer, as described above, in addition to the nonwoven fabric in which fibers are bonded by a chemical bond method using a binder resin latex that does not have biodegradability, a spunlace nonwoven fabric in which fibers are bonded by a spunlace method, Nonwoven fabrics or the like in which fibers are entangled and bonded by the needle punch method can also be used.

  When the auxiliary sheet 20 has a two-layer structure or a three-layer structure in which a surface layer made of a nonwoven fabric to which a flame retardant is added is provided on at least one surface side of the middle layer, as a flame retardant to be added to the surface layer It is preferable to use at least a guanidine-based flame retardant such as guanidine phosphate exemplified as the phosphorus / nitrogen-based condensate or guanidine sulfamate. Guanidine-based flame retardant has the property of exhibiting tackiness by heat. Therefore, by including a guanidine-based flame retardant in the surface layer, the guanidine-based flame retardant contained in the surface layer is heated without using an adhesive for bonding the surface layer and the intermediate layer separately. By exhibiting, the surface layer and the middle layer can be adhered. If general polyolefin powder, PET powder, or the like is used as an adhesive, they generate scum that cannot be removed with a strong alkaline solution by laser irradiation. The guanidine-based flame retardant exhibits adhesiveness by heating when the binder component (heat-fusible biodegradable fiber) included in the middle layer is heated, for example.

  There is no restriction | limiting in particular as a method to provide a guanidine type flame retardant to the nonwoven fabric which makes a surface layer, According to the form (powder form, liquid state, etc.) of a flame retardant, the method illustrated previously etc. are employable. For example, when manufacturing a nonwoven fabric that forms a surface layer by spraying a binder resin latex to an airlaid web obtained by the airlaid method, a guanidine flame retardant is added to the binder resin latex and the binder resin is added. Examples thereof include a method of applying a guanidine flame retardant.

  In addition, when using a flame retardant other than a guanidine flame retardant as a flame retardant added to the surface layer, the surface layer is adhered to the middle layer by the action of the heat-fusible biodegradable fiber contained in the middle layer. Is also possible.

  A three-layer structure in which a non-woven fabric obtained by bonding an air-laid web formed by an air-laid method by a thermal bond method is used as an intermediate layer, and a surface layer made of a non-woven fabric added with a flame retardant is provided on both sides of the intermediate layer. The auxiliary sheet can be manufactured as follows, for example.

First, a nonwoven fabric forming a surface layer is manufactured.
When the non-woven fabric is obtained by bonding fibers to an air laid web by a chemical bond method, first, a biodegradable fiber (for example, non-heat-sealable biodegradable material) is applied to an air laid web forming machine. A fiber for forming a surface layer mainly composed of cellulose fibers such as pulp fibers). By adjusting the supply amount here, the basis weight of the nonwoven fabric forming the surface layer can be adjusted.
Next, the surface layer forming fibers are uniformly mixed and pulverized in the air, and are dropped along with the intake air flow onto the mesh conveyor that runs on the suction box to form an airlaid web. Next, a flame retardant such as a guanidine flame retardant was added to a binder resin latex having no biodegradability, such as ethylene / vinyl acetate copolymer latex and butadiene copolymer latex, on both surfaces of the airlaid web. Spray the liquid, apply the binder resin and the flame retardant, and dry. Thereby, the nonwoven fabric containing the flame retardant which makes a surface layer is obtained. The kind of binder resin latex may be the same or different on one side and the other side of the airlaid web.

  When the nonwoven fabric forming the surface layer is one in which fibers are bound by the spunlace method, the above-mentioned surface layer forming fibers are entangled with high-pressure water by a known spunlace nonwoven fabric manufacturing apparatus to form the nonwoven fabric. . Subsequently, the nonwoven fabric which makes a surface layer is obtained by spraying the liquid containing a flame retardant with respect to the formed nonwoven fabric, or impregnating the formed nonwoven fabric with the liquid containing a flame retardant. Alternatively, fibers such as rayon in which a flame retardant is kneaded in advance may be used, and the fibers may be bonded by a spunlace method.

Next, the nonwoven fabric forming the surface layer obtained as described above is fed out on a mesh conveyor that runs on the suction box. On the other hand, the airlaid web forming machine includes at least a heat-fusible biodegradable fiber, and preferably includes a biodegradable fiber (for example, a heat-fusible biodegradable fiber and a non-heat-fusible fiber). A mixture of a heat-fusible biodegradable fiber having a core-sheath structure and a non-heat-fusible biodegradable fiber made of cellulose fiber such as pulp fiber is provided. By adjusting the supply amount here, the basis weight of the nonwoven fabric forming the middle layer can be adjusted. Moreover, when adding a flame retardant to an intermediate | middle layer, a powdery flame retardant can be mixed in the fiber for intermediate | middle layer formation. Here, the content of the heat-fusible biodegradable fiber in the total amount of the heat-fusible biodegradable fiber and the non-heat-fusible biodegradable fiber is preferably in the range described above.
Next, the surface layer is formed by lowering together with the intake air flow onto the mesh conveyor and depositing it while uniformly mixing and pulverizing the intermediate layer forming fiber and the flame retardant added as necessary. An airlaid web is formed on the resulting nonwoven fabric. Next, a nonwoven fabric forming a surface layer is separately drawn and laminated on the air laid web.

And this 3 layer laminated body is led to dryers, such as a hot air dryer, and is heated. Thereby, at least a part of the heat-fusible biodegradable fiber used for the middle layer forming fiber is dissolved, and the middle layer fibers are bonded to each other. In addition, when a guanidine flame retardant is used as the flame retardant for the nonwoven fabric forming the surface layer, the guanidine flame retardant exhibits tackiness by heating in a dryer, and the middle layer and the surface layer are bonded by the tackiness. To do.
Thereby, the auxiliary | assistant sheet | seat of the 3 layer structure by which the surface layer which consists of a nonwoven fabric to which the flame retardant was added was provided in the both surface side of the nonwoven fabric which makes an intermediate | middle layer is obtained.
In addition, after heating with a dryer, it is preferable to pass the auxiliary sheet through a press roll to adjust the thickness, apparent density, and the like of the auxiliary sheet.

  In the case of producing an auxiliary sheet having a two-layer structure consisting of an intermediate layer and a single surface layer, the nonwoven fabric forming the surface layer was drawn out on the air laid web formed on the nonwoven fabric forming the surface layer. Instead, roll out a permeable carrier sheet such as tissue paper. And after guide | inducing sequentially to a dryer and a press roll, what is necessary is just to peel an air-permeable carrier sheet.

In the case of manufacturing an auxiliary sheet consisting of one layer, a gas-permeable carrier sheet such as tissue paper is fed out on a mesh conveyor that runs on a suction box. On the other hand, the airlaid web forming machine includes at least a heat-fusible biodegradable fiber, and preferably includes a biodegradable fiber (for example, a heat-fusible biodegradable fiber and a non-heat-fusible fiber). A mixture of heat-fusible biodegradable fibers having a core-sheath structure and non-heat-fusible biodegradable fibers made of cellulose fibers such as pulp fibers. By adjusting the supply amount here, the basis weight and the like of the auxiliary sheet can be adjusted. Moreover, when adding a flame retardant to an auxiliary | assistant sheet | seat, a powdery flame retardant can be mixed in raw material fiber. Here, the content of the heat-fusible biodegradable fiber in the total amount of the heat-fusible biodegradable fiber and the non-heat-fusible biodegradable fiber is preferably in the range described above.
Next, the raw fiber and the flame retardant added as necessary are uniformly mixed and crushed in the air, and then dropped onto the mesh conveyor along with the intake air flow and deposited on the air-permeable carrier sheet. An airlaid web is formed. Next, an air-permeable carrier sheet is separately drawn and laminated on the air laid web.

And this 3 layer laminated body is led to dryers, such as a hot air dryer, and is heated. Thereby, at least a part of the heat-fusible biodegradable fiber used for the raw material fiber is dissolved, and the raw material fibers are bonded to each other. Then, this is sequentially guided to a dryer and a press roll, and finally the two air-permeable carrier sheets are peeled off. Thereby, the auxiliary sheet which consists of a 1 layer nonwoven fabric is obtained.
In addition, the auxiliary sheet may further have a layer made of tissue paper or the like, for example, as long as it does not adversely affect the washing with the strong alkaline solution.

In the present invention, the fiber length of each fiber used for manufacturing the auxiliary sheet 20 can be appropriately selected according to the form of the auxiliary sheet, the manufacturing method, and the like. For example, when the auxiliary sheet 20 is a woven fabric, continuous fibers (long fibers) are used. In the case of a nonwoven fabric that employs the airlaid method as the web forming method, the fiber length is preferably 2 to 10 mm. In the case of the nonwoven fabric by the spunlace method, the fiber length is preferably 40 to 80 mm.
Further, the fineness of the fiber is not particularly limited, and may be a fineness of about 1.7 to 56 dtex. However, the fineness of the heat-fusible biodegradable fiber is preferably 2.2 to 3.3 dtex, and non-heat-melting. The fineness of the wearable biodegradable fiber is preferably 20 to 40 dtex.
In the present specification, the fiber length is an average value of lengths measured by observation with an electron microscope using 50 arbitrarily selected fibers as samples.
The fineness is expressed in the unit “dtex (decitex)”. 1 dtex is the thickness of a thread having a length of 10,000 m and a weight of 1 g.

  As described above, according to the auxiliary sheet of the present invention, it is disposed between the work table and the base material, and the irregular reflection of the laser beam on the surface of the work table can be prevented to suppress the variation in the hole diameter. Moreover, since it consists of a laminated material of a woven fabric, a nonwoven fabric, and a woven fabric and a nonwoven fabric, it has moderate air permeability, and does not prevent the holding | maintenance of the base material on the work bench. Moreover, since it is formed of raw material fibers mainly composed of biodegradable fibers, the residue generated by laser irradiation is dissolved in a strong alkaline solution and can be easily removed by an existing substrate cleaning process.

Hereinafter, the present invention will be specifically described with reference to examples.
<Example 1>
(Manufacture of nonwoven fabric for surface layer)
On a mesh conveyor that feeds pulp fibers, which are non-heat-bondable biodegradable fibers, to an airlaid web forming machine, crushes the pulp fibers while uniformly mixing them in the air, and runs on a suction box The airlaid web made of pulp fibers was formed by being dropped together with the intake air flow and falling and deposited.
Next, one surface of the air laid web was sprayed with an ethylene / vinyl acetate copolymer latex to which guanidine phosphate as a flame retardant (“Apinon 307 (trade name)” manufactured by Sanwa Chemical Co., Ltd.) was added. The butadiene copolymer latex added with the above-mentioned guanidine phosphate was sprayed on the surface. Then, this was dried with a hot air dryer.
In this way, a nonwoven fabric for flame-retardant surface layer (flame-retardant pulp fiber air-laid nonwoven fabric) having a thickness of 1.0 mm and a basis weight of 55 g / m ² , in which the fibers of the air-laid web are bonded by the chemical bond method. Obtained. The flame retardant content in the nonwoven fabric is 18.5% by mass, the pulp fiber content is 62.3% by mass, the ethylene / vinyl acetate copolymer content is 10.5% by mass, and the butadiene copolymer. The content of was 8.7% by mass.

(Manufacture of auxiliary sheets)
The nonwoven fabric for the surface layer obtained as described above was fed out on a mesh conveyor running on a suction box. On the other hand, the air-laid web forming machine has a pulp fiber, which is a non-heat-fusible biodegradable fiber, and a core-sheath-type polylactic acid (PLA) composite fiber (unitika), which is a heat-fusible biodegradable fiber. The mixing ratio shown in the middle column of Table 1 is “Terramac (trade name)”, fineness 2.2 dtex, fiber length 5 mm, melting point 170 ° C. of core (polylactic acid), melting point 130 ° C. of sheath (polylactic acid)) (Mass ratio) was supplied, mixed and defibrated uniformly in the air, lowered onto the mesh conveyor along with the intake air flow, and dropped and accumulated. Thereby, an airlaid web (middle layer) was formed on the nonwoven fabric for the surface layer. Further, a nonwoven fabric for the surface layer was drawn on the air laid web to obtain a three-layer laminate.
Next, this three-layer laminate was guided to a hot air dryer and heated to 130 ° C. or higher. Subsequently, this was passed through a press roll to produce a three-layer auxiliary sheet having a basis weight, thickness, and apparent density shown in Table 1. In addition, the thickness of the auxiliary | assistant sheet | seat of Table 1, and the thickness of each layer are all the values after a press roll. The non-woven fabric for the surface layer originally has a thickness of 1.0 mm, but is compressed to 0.3 mm after passing through a press roll to form an auxiliary sheet.

When the obtained auxiliary sheet was evaluated for flame retardancy, it passed UL94HBF (flame retardancy test). Further, Frazier air permeability Q (cc / cm ² · sec) based on A method of JIS L1096 of the auxiliary sheet was measured. The results are shown in Table 1.

Further, the obtained auxiliary sheet is arranged as shown in FIG. 1, and the substrate (a copper-clad laminate having a structure in which an epoxy resin layer having a thickness of 200 μm is sandwiched between two copper foils having a thickness of 8 μm). A carbon dioxide laser was irradiated to form a through hole. Many through-holes were formed in a 30 mm × 30 mm area of the substrate with a pitch of 0.5 mm and a pitch of 0.2 mm.
Subsequently, the base material washing process by a strong alkaline solution was performed with respect to the base material after a through-hole was formed. As the strong alkaline solution, a solution at 80 ° C. in which sodium permanganate (concentration 60 g / L) and sodium hydroxide (concentration 40 g / L) are dissolved is used. In the solution, the substrate is transported at a speed of 2 m / min. The substrate cleaning process was performed by horizontally transporting for 2 minutes (condition 1). As a result, adhesion of debris was not recognized in the inside and the periphery of all the through holes. In addition, in both cases where the conveyance speed of the base material is 1 m / min and is conveyed horizontally for 4 minutes (condition 2), and when a batch type immersed in a strong alkaline solution at 70 ° C. for 7 minutes is adopted (condition 3), There was no adhesion of debris inside or around the perforations.
Moreover, when the hole diameter of the through-hole formed in the base material was measured, the hole diameter of the through-hole (the hole diameter on the side in contact with the auxiliary sheet) was varied at both pitch 0.5 mm and pitch 0.2 mm. Was not recognized.

  In addition, the swelling process by the weak alkaline chemical | medical agent containing a butyl carbitol was performed before the base-material washing | cleaning process. Moreover, after the base-material washing | cleaning process, the neutralization process by a hydroxylamine sulfate and the etching process of the copper foil by sodium persulfate were performed.

<Example 2>
As a heat-fusible biodegradable fiber, a composite fiber having a core-sheath structure in which the core is made of polylactic acid and the sheath is made of polybutylene succinate instead of the polylactic acid composite fiber ("NFF (KK)-" manufactured by Daiwabo Polytech Co., Ltd.) “PL (trade name)”, fineness 3.3 dtex, fiber length 5 mm, core melting point 170 ° C., sheath melting point 110 ° C.), the basis weight and thickness shown in Table 1 are the same as in Example 1. Now, an auxiliary sheet having an apparent density was obtained, and the same measurement and evaluation as in Example 1 were performed.
As a result, the auxiliary sheet had flame retardancy that passed UL94HBF (flame retardancy test).
Table 1 shows the fragile air permeability Q (cc / cm ² · sec) based on JIS L1096 method A of the auxiliary sheet.
Moreover, when the base-material washing | cleaning process by a strong alkaline solution was performed with respect to the base material after a through-hole was formed, in any of the conditions 1, conditions 2, and conditions 3, it is the same as that of Example 1. In addition, no adhesion of debris was observed in the inside and the periphery of all the through holes. Moreover, when the hole diameter of the through-hole formed in the base material was measured, as in Example 1, the hole diameter of each through-hole (the surface in contact with the auxiliary sheet) at both pitch 0.5 mm and pitch 0.2 mm. No variation was observed in the side hole diameter.

<Example 3>
Non-woven fabric (flame retardant rayon fiber span) manufactured by the spunlace method using rayon fibers (manufactured by Daiwabo Rayon Co., Ltd., “DFG (trade name)”, fineness 1.7 dtex) as a nonwoven fabric for the surface layer. Except for using the lace nonwoven fabric, the auxiliary sheet having the basis weight, thickness, and apparent density shown in Table 1 was obtained in the same manner as in Example 1, and the same measurement and evaluation as in Example 1 were performed. The surface layer nonwoven fabric had a thickness of 1.0 mm, a basis weight of 200 g / m ² , and the content of the flame retardant in the nonwoven fabric was 25% by mass (a flame retardant: an organic phosphorus compound).
The auxiliary sheet had flame retardancy that passed UL94HBF (flame retardancy test).
Table 1 shows the fragile air permeability Q (cc / cm ² · sec) based on JIS L1096 method A of the auxiliary sheet.
Moreover, when the base-material washing | cleaning process by a strong alkaline solution was performed with respect to the base material after a through-hole was formed, in any of the conditions 1, conditions 2, and conditions 3, it is the same as that of Example 1. In addition, no adhesion of debris was observed in the inside and the periphery of all the through holes. Moreover, when the hole diameter of the through-hole formed in the base material was measured, as in Example 1, the hole diameter of each through-hole (the surface in contact with the auxiliary sheet) at both pitch 0.5 mm and pitch 0.2 mm. No variation was observed in the side hole diameter.

<Example 4>
Auxiliary sheet having the basis weight, thickness, and apparent density shown in Table 1 in the same manner as in Example 1 except that the mixing ratio of the fibers for forming the middle layer was changed to the mass ratio shown in the middle layer column of Table 1. The same measurement and evaluation as in Example 1 were performed.
As a result, the auxiliary sheet had flame retardancy that passed UL94HBF (flame retardancy test).
Table 1 shows the fragile air permeability Q (cc / cm ² · sec) based on JIS L1096 method A of the auxiliary sheet.
Moreover, when the base-material washing | cleaning process by a strong alkaline solution was performed with respect to the base material after a through-hole was formed, in any of the conditions 1, conditions 2, and conditions 3, it is the same as that of Example 1. In addition, no adhesion of debris was observed in the inside and the periphery of all the through holes. Moreover, when the hole diameter of the through-hole formed in the base material was measured, as in Example 1, the hole diameter of each through-hole (the surface in contact with the auxiliary sheet) at both pitch 0.5 mm and pitch 0.2 mm. No variation was observed in the side hole diameter.

<Example 5>
Change the mixing ratio of the fibers to form the middle layer to the mass ratio shown in the middle layer column of Table 1, add a flame retardant to the middle layer, and change to the basis weight, thickness, and apparent density shown in Table 1 Except that, an auxiliary sheet was obtained in the same manner as in Example 1, and the same measurement and evaluation as in Example 1 were performed. However, the addition of the flame retardant to the middle layer was performed by a method in which a powdery flame retardant was mixed with the middle layer forming fiber for forming the middle layer and laminated together with the fiber. As the flame retardant, “Nonen W-3 (trade name)” manufactured by Maruhishi Oil Chemical Co., Ltd., which is a nitrogen phosphate condensate (polyphosphate carbanate), was used.
The auxiliary sheet had flame retardancy that passed UL94HBF (flame retardancy test).
Table 1 shows the fragile air permeability Q (cc / cm ² · sec) based on JIS L1096 method A of the auxiliary sheet.
Moreover, when the base-material washing | cleaning process by a strong alkaline solution was performed with respect to the base material after a through-hole was formed, in any of the conditions 1, conditions 2, and conditions 3, it is the same as that of Example 1. In addition, no adhesion of debris was observed in the inside and the periphery of all the through holes. Moreover, when the hole diameter of the through-hole formed in the base material was measured, variation was not recognized in the hole diameter (hole diameter of the surface side which contacted the auxiliary sheet) of each through-hole similarly to Example 1.

<Comparative Example 1>
The same as Example 1 except that instead of the polylactic acid composite fiber, an intermediate layer was formed using a heat-fusible fiber made of polyethylene (manufactured by Mitsui Chemicals, “SWP (trade name)”, melting point 130 ° C.). Thus, an auxiliary sheet was obtained, and the same measurement and evaluation as in Example 1 were performed.
As a result, it had the flame retardance which passed UL94HBF (flame retardance test).
Table 1 shows the fragile air permeability Q (cc / cm ² · sec) based on JIS L1096 method A of the auxiliary sheet.
Moreover, when the base-material washing | cleaning process by a strong alkaline solution was performed with respect to the base material after a through-hole was formed, in any of the conditions 1, conditions 2, and conditions 3, the inside of many through-holes In addition, adhesion of debris was observed at the periphery. When the hole diameter of the through hole formed in the base material (the hole diameter on the surface side in contact with the auxiliary sheet) was measured, there was variation in the hole diameter of each through hole at both pitch 0.5 mm and pitch 0.2 mm. I was not able to admit.

The auxiliary sheet of each example had moderate air permeability and excellent flame retardancy. Moreover, the variation in the hole diameter of the through-hole formed can be suppressed by using the auxiliary sheet. Further, after the substrate cleaning process using a strong alkaline solution, no adhesion of debris was observed in the inside and the periphery of the through hole.
On the other hand, in the auxiliary sheet of the comparative example, adhesion of debris derived from the polyethylene fiber was observed in the inside and the periphery of the through hole even after the substrate cleaning step using the strong alkaline solution.

10: Base material 20: Auxiliary sheet for laser processing

Claims (6)

When forming a through-hole by irradiating a laser beam from one surface side of the substrate to the substrate, the substrate is disposed on the other surface side of the substrate,
An auxiliary sheet for laser processing comprising a woven or non-woven fabric or a laminate of a woven fabric and a non-woven fabric formed from raw fibers mainly composed of biodegradable fibers.   The auxiliary sheet for laser processing according to claim 1, wherein the biodegradable fiber is a nonwoven fabric, and the biodegradable fiber contains a heat-fusible biodegradable fiber.   The auxiliary sheet for laser processing according to claim 1 or 2, comprising a flame retardant.   The auxiliary sheet for laser processing according to claim 3, comprising a flame retardant in at least one of the two layers located on the outermost surface.   The auxiliary sheet for laser processing according to claim 4, wherein the flame retardant contains a guanidine-based flame retardant.   The laser processing according to any one of claims 1 to 5, wherein the biodegradable fiber contains non-heat-fusible biodegradable fiber, and the non-heat-fusible biodegradable fiber contains cellulose fiber. Auxiliary sheet.

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