JP7606865B2 - Drilling backing plate - Google Patents

Description

The present invention relates to a drilling backing plate used when drilling holes in printed wiring boards, etc.

Printed circuit boards (hereafter simply referred to as "circuit boards") are used in devices such as communication devices, batteries, office automation equipment, and home appliances, and the demand for circuit boards has increased significantly in recent years.

It is necessary to provide through holes in the board, and a drill is used to make holes. At this time, a backing plate for drilling, such as aluminum, is used to prevent scratches and burrs on the board. From the viewpoint of productivity, it is common to stack several boards, place a backing plate for drilling (hereinafter sometimes simply called a "backing plate") on top of them, and then perform drilling on all the boards at once.
In this case, a lubricating layer is formed on the surface of a backing plate made of aluminum or the like to prevent the drill from breaking, smooth the inner wall of the hole, and improve the positional accuracy of the hole.

Various proposals have been made regarding the lubricating layer on the surface of the backing plate. For example, Patent Document 1 discloses a water-soluble lubricant sheet formed from a mixture of 20-90% by weight of polyethylene glycol having a molecular weight of 10,000 or more and 80-10% by weight of a water-soluble lubricant. Patent Document 2 discloses a water-soluble lubricant sheet formed from a mixture of 20-90% by weight of polyether ester and 80-10% by weight of a water-soluble lubricant. Patent Document 3 discloses a lubricating resin composition composed of a matrix resin made of modified polyamide and an inorganic powder filler.

However, these lubricating layers do not have sufficient adhesion to the backing plate, which causes problems such as partial peeling off of the lubricating layer from the substrate, resulting in uneven thickness, and unevenness during drilling, which can lead to drill breakage and reduced hole positioning accuracy.

In the invention described in Patent Document 4, in order to solve the problems caused by the lack of adhesion between the backing plate and the lubricating layer, a lubricating layer is formed on the backing plate via an undercoat layer made of a specific partially saponified polyvinyl acetate, resulting in a lubricating layer with few abnormalities.

Patent Document 5 discloses a backing plate in which a lubricating layer containing a polyurethane resin, which is a copolymer having constituent units derived from alicyclic diisocyanate and constituent units derived from aliphatic polyol, and a water-soluble resin in a specific ratio is formed on a metal foil without an adhesive layer (undercoat layer). Patent Document 5 claims that by not providing an adhesive layer (undercoat layer), it has solved the problems of poor hole position accuracy and inner wall roughness due to a decrease in the lubricating effect.

In recent years, with the increasing performance of devices, wiring patterns on printed circuit boards have become finer, denser, and more multi-layered, and there is an increasing demand for small through holes. To create small through holes, it is necessary to use a small-diameter drill, but if the drill diameter is small, problems such as drill breakage and reduced hole position accuracy are likely to occur.

For this reason, there is a need to develop technology that can accurately process small through holes in circuit boards.

Japanese Patent Application Publication No. 4-092494 Japanese Patent Application Publication No. 6-344297 JP 2001-146600 A Patent No. 4793358 International Publication No. 2017/155060

The present invention has been made in consideration of the above-mentioned background art, and its objective is to provide a backing plate that is less likely to break when a small-diameter drill is used to drill a small-diameter through hole in a substrate, and that allows for drilling with high hole position accuracy.

As a result of extensive research into solving the above problems, the inventors discovered that by incorporating a specific polyurethane resin into the lubricating layer, even when a small-diameter drill is used, the drill is less likely to break and holes can be drilled with high hole position accuracy, thus completing the present invention.

That is, the present invention provides a drilling backing plate having a lubricating layer formed on at least one surface of a metal plate via an undercoat layer, the lubricating layer containing a polyurethane resin having a carbonate structure.

The present invention also provides a method of drilling, which comprises placing the above-mentioned backing plate on a printed circuit board and using a drill to drill holes with a diameter of 0.05 mm to 0.12 mm in the backing plate and the printed circuit board from above the backing plate.

The drilling backing plate of the present invention makes it possible to drill holes with high hole position accuracy without causing drill breakage, even when a small-diameter drill is used to create small-diameter through holes in a printed circuit board. As a result, the productivity and yield of the drilling process are improved.

1 is a schematic cross-sectional view showing the structure of a drilling backing plate of the present invention.

The present invention will be described below, but it is not limited to the following embodiments and can be modified in any way.

The drilling backing plate of the present invention is used when drilling holes using a drill to create through holes in a printed circuit board.

Figure 1 shows the structure of the drilling backing plate 1 of the present invention. In the backing plate 1 of the present invention, a lubricating layer 4 is formed on at least one surface of a metal plate 2 via an undercoat layer 3. Figure 1 shows an example in which the undercoat layer 3 and the lubricating layer 4 are formed only on one surface of the metal plate 2.

When using the backing plate 1 of the present invention, the backing plate 1 is placed on a printed circuit board (not shown), and a drill (not shown) is used to form holes in the backing plate 1 and the printed circuit board from above the backing plate 1 (i.e., from the side of the lubricating layer 4 in FIG. 1).

When drilling holes, problems such as the drill breaking or holes being misaligned can occur, and these problems are more likely to occur when the drill diameter is small (in other words, when the diameter of the holes to be formed in the printed circuit board is small).

The backing plate 1 of the present invention is particularly effective in preventing such problems when the drill diameter is small. Specifically, the backing plate 1 for drilling of the present invention is suitable for forming holes with diameters of 0.05 mm to 0.12 mm in a printed circuit board (for drilling using a drill with a diameter of 0.05 mm to 0.12 mm). However, the use of the backing plate 1 for drilling to form holes with diameters outside the above range does not fall outside the scope of the present invention.

There are no particular limitations on the metal plate 2, but an aluminum plate such as a soft aluminum plate, a semi-hard aluminum plate, or a hard aluminum plate is preferred because it is soft and suitable for drilling, and is low cost (note that in this specification, "metal plate" includes "metal foil", and "aluminum plate" includes "aluminum foil").
The aluminum plate may be made of pure aluminum or an aluminum alloy.

The thickness of the metal plate 2 is preferably 30 μm or more, and particularly preferably 50 μm or more, and is preferably 500 μm or less, and particularly preferably 300 μm or less.
When the thickness is equal to or greater than the lower limit, the generation of burrs can be prevented, whereas when the thickness is equal to or less than the upper limit, the discharge of chips generated during production is improved.

The undercoat layer 3 serves to improve the adhesion between the metal plate 2 and the lubricating layer 4 (making the lubricating layer 4 less likely to peel off from the metal plate 2). By making the lubricating layer 4 less likely to peel off from the metal plate 2, it becomes easier to prevent defects such as misalignment of holes and breakage of the drill.

Examples of the compound that is the main component of the undercoat layer 3 (hereinafter sometimes referred to as "undercoat layer compound") include partially saponified polyvinyl acetate, vinyl acetate-vinyl chloride copolymer, partially saponified vinyl acetate-vinyl chloride copolymer, vinyl acetate-vinyl chloride-maleic acid (anhydride) copolymer, and partially saponified vinyl acetate-vinyl chloride-maleic acid (anhydride) copolymer.
Incidentally, "maleic acid (anhydride)" refers to "maleic acid and/or maleic anhydride".
These undercoat layer compounds may be used alone or in combination of two or more.

Among the above-mentioned compounds for the undercoat layer, "partially saponified polyvinyl acetate", "partially saponified vinyl acetate-vinyl chloride copolymer", and "partially saponified vinyl acetate-vinyl chloride-maleic acid (anhydride) copolymer" refer to compounds in which some of the vinyl acetate structural units in "polyvinyl acetate", "vinyl acetate-vinyl chloride copolymer", and "vinyl acetate-vinyl chloride-maleic acid (anhydride) copolymer" have been converted to vinyl alcohol structural units by hydrolysis, respectively.

The saponification degree of these compounds is preferably 15% or more, more preferably 20% or more, and particularly preferably 30% or more, and is preferably 95% or less, more preferably 80% or less, and particularly preferably 60% or less.
The "saponification degree" is expressed as [number of vinyl alcohol structural units/(number of vinyl acetate structural units+number of vinyl alcohol structural units)]×100.
When the saponification degree is within the above range, the adhesion between the metal plate 2 and the lubricating layer 4 tends to be good.

The degree of polymerization of the undercoat layer compound is preferably 200 or more, more preferably 250 or more, and particularly preferably 300 or more. Also, it is preferably 1000 or less, more preferably 900 or less, and particularly preferably 700 or less.
Within the above range, the adhesion between the metal plate 2 and the lubricating layer 4 tends to be good.

In addition to the above-mentioned compounds for the undercoat layer, the undercoat layer 3 may contain polyacrylic acid derivatives, cellulose derivatives, etc.

The lubricating layer 4 prevents the drill from sliding sideways on the surface of the backing plate during drilling, which could lead to misalignment of the hole or breakage of the drill due to friction.

The lubricating layer 4 of the drilling backing plate 1 of the present invention contains a polyurethane resin having a carbonate structure.

"Polyurethane resin" refers to a resin that has a urethane bond (-NH-C(=O)-O-), and is usually produced by a polycondensation reaction between a compound (polyisocyanate compound) that has two or more isocyanate groups (-N=C=O) and a compound (polyol compound) that has two or more hydroxyl groups (-OH).

The polyurethane resin contained in the lubricating layer 4 of the contact plate 1 of the present invention has a carbonate structure (-O-C(=O)-O-). Usually, the carbonate structure is contained in the part of the polyurethane resin derived from a polyol compound.
That is, a "polyurethane resin having a carbonate structure" is produced by reacting a "polyol compound having a carbonate structure" with a "polyisocyanate compound".

An example of a polyol compound having a carbonate structure is a diol compound having a carbonate structure represented by the following formula (1).

In formula (1), R ¹ is a divalent hydrocarbon group, and n is any natural number.

R ¹ may be an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group.
In addition, when R ¹ is an aliphatic hydrocarbon group, it may be linear or branched. When R ¹ is an aliphatic hydrocarbon group or an alicyclic hydrocarbon group, it may be saturated or unsaturated.

The number of carbon atoms in ^R1 is preferably 2 or more, more preferably 3 or more, and particularly preferably 4 or more. Also, the number of carbon atoms in R1 is preferably 40 or less, more preferably 30 or less, and particularly preferably 20 or less.

The diol compound having a carbonate structure represented by formula (1) can be obtained, for example, by (A) a method of transesterification between a diol monomer represented by the following formula (2) and a carbonate ester, or (B) a method of reacting a diol monomer represented by the following formula (2) with phosgene in the presence of an alkali.

The above method (A) can be carried out, for example, by melt polymerization, and the carbonate ester that can be used is dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, etc.

Specific examples of diol monomers represented by formula (2) include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,2-propanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-pentanediol, 2-methyl-1,4-butanediol, neopentyl glycol, 1,5-hexanediol, 2-methyl-1, Examples include aliphatic diol monomers such as 5-pentanediol, 3-methyl-1,5-pentanediol, and 2-methyl-1,8-octanediol; alicyclic diol monomers such as 1,3-cyclopentanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; and aromatic diol monomers such as catechol, hydroquinone, resorcinol, 1,3-benzenedimethanol, 1,4-benzenedimethanol, bisphenol A, bisphenol B, bisphenol AP, bisphenol C, and bisphenol Z.

The "polyurethane resin having a carbonate structure" contained in the lubricating layer 4 of the contact plate 1 of the present invention can be produced by reacting the above-mentioned "polyol compound having a carbonate structure" with a polyisocyanate compound.
In this case, the "polyol compound having a carbonate structure" may be used alone or in combination of two or more kinds.

In addition, the polyol compounds reacted when producing the "polyurethane resin having a carbonate structure" do not all have to be "polyol compounds having a carbonate structure", and a "polyol compound having a carbonate structure" and a "polyol compound not having a carbonate structure" may be used in combination. In other words, the "polyurethane resin having a carbonate structure" may have polyol units (a) derived from the "polyol compound having a carbonate structure" and polyol units (b) derived from the "polyol compound not having a carbonate structure".
In this case, the ratio of the polyol unit (a) to the total polyol units is preferably 10 mol% or more, more preferably 20 mol% or more, and particularly preferably 30 mol% or more, and is preferably 99 mol% or less, more preferably 90 mol% or less, and particularly preferably 80 mol% or less.

As polyol compounds that do not have a carbonate structure, diol monomers, polyether polyols, polyester polyols, etc. can be used as appropriate.

Examples of diol monomers include the diol monomers described above.

Examples of polyether polyols include polymers or copolymers of ethylene glycol, propylene glycol, tetrahydrofuran, etc.

Examples of polyester polyols include those obtained by dehydration condensation of saturated or unsaturated low molecular weight diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, and dipropylene glycol, and dicarboxylic acids such as adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid, or anhydrides thereof.

The above-mentioned "polyol compounds not having a carbonate structure" may be used alone or in combination of two or more kinds.

The polyisocyanate compounds that are reacted to produce the "polyurethane resin having a carbonate structure" include aliphatic diisocyanates such as butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate; cyclohexane-1,4-diisocyanate, isophorone diisocyanate, norbornane diisocyanate methyl, bis(4-isocyanatocyclohexyl)methane, 1,3-bis(isocyanatomethyl)cyclohexane, and methylcyclohexane diisocyanate. Examples include alicyclic diisocyanates such as diphenyl diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-benzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, triphenyl diisocyanate, tolylene diisocyanate, and xylylene diisocyanate.

These polyisocyanate compounds may be used alone or in combination of two or more.

The lubricating layer 4 of the drilling backing plate 1 of the present invention may contain a "polyurethane resin having no carbonate structure" in addition to the above-mentioned "polyurethane resin having a carbonate structure". That is, the lubricating layer 4 may contain both a "polyurethane resin having a carbonate structure" and a "polyurethane resin having no carbonate structure".
The "polyurethane resin having no carbonate structure" can be produced by reacting the above-mentioned "polyol compound having no carbonate structure" with a polyisocyanate compound.

The lubricating layer 4 may contain both a "polyurethane resin having a carbonate structure" and a "polyurethane resin not having a carbonate structure".
In this case, the content of the "polyurethane resin having a carbonate structure" in the total polyurethane resin is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 30% by mass or more. Also, it is preferably 99% by mass or less, more preferably 90% by mass or less, and particularly preferably 80% by mass or less.

The content of the "polyurethane resin having a carbonate structure" in the lubricating layer 4 (total content when two or more types are used in combination) is preferably 5% by mass or more, more preferably 7% by mass or more, and particularly preferably 10% by mass or more. Also, it is preferably 70% by mass or less, more preferably 60% by mass or less, and particularly preferably 50% by mass or less.
Within the above range, breakage of the drill is unlikely to occur, and hole position accuracy is likely to be good.

The lubricating layer 4 of the drilling backing plate 1 of the present invention usually contains a water-soluble resin in addition to the aforementioned "polyurethane resin having a carbonate structure" and "polyurethane resin without a carbonate structure."

Examples of such water-soluble resins include polyalkylene oxides, polyalkylene oxide derivatives, polyglycerin fatty acid esters, sorbitan fatty acid esters, sodium polyacrylate, cellulose derivatives, water-soluble polyesters, etc.

Examples of polyalkylene oxides include polyethylene oxide, polypropylene oxide, polybutylene oxide, polyethylene oxide-polypropylene oxide copolymers, polypropylene oxide-polybutylene oxide copolymers, and the like.
Among these, polyethylene oxide or a polyethylene oxide-polypropylene oxide copolymer is preferred from the viewpoints of water solubility, stability of the lubricating layer, and lubricating performance.

The number average molecular weight of the polyalkylene oxide is preferably 1,000 or more, more preferably 5,000 or more, and particularly preferably 10,000 or more. Also, it is preferably 300,000 or less, more preferably 200,000 or less, and particularly preferably 100,000 or less.
A plurality of polyalkylene oxides having different molecular weights may be used in combination.

Examples of polyalkylene oxide derivatives include polyoxyethylene ethers such as polyoxyethylene methyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polysorbates such as polyoxyethylene coconut oil fatty acid sorbitan, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan isostearate, polyoxyethylene sorbitan monostearate, and polyoxyethylene sorbitan trioleate; and the like.

Examples of polyglycerol fatty acid esters include polyglycerol monocaprate, polyglycerol monomyristate, polyglycerol monolaurate, polyglycerol monostearate, and polyglycerol monooleate.

Examples of sorbitan fatty acid esters include sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, and sorbitan tribehenate.

Examples of cellulose derivatives include methylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, and carboxymethylcellulose.

These water-soluble resins may be used alone or in combination of two or more.

The content of the water-soluble resin in the lubricating layer 4 (total content when two or more types are used in combination) is preferably 20% by mass or more, more preferably 30% by mass or more, and particularly preferably 50% by mass or more. Also, it is preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 80% by mass or less.
Within the above range, application can be performed smoothly, the lubricating layer will be of good quality, and problems are unlikely to occur during drilling.

The lubricating layer 4 of the drilling backing plate 1 of the present invention may contain an emulsion stabilizer. The term "emulsion stabilizer" refers to a substance that has the effect of increasing the viscosity of the liquid phase to stabilize the dispersion of particles, chemically bonding with particles to prevent the particles from agglomerating together, and the like.
By adding an emulsion stabilizer to the lubricating layer 4, aggregation of the particles of the water-soluble resin to be blended can be prevented.

Examples of emulsion stabilizers include polyvinyl alcohol, isobutylene maleic anhydride copolymers, ethylene oxide propylene oxide block copolymers, ethylene oxide propylene oxide phenyl copolymers, propylene glycol fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, sorbitan fatty acid esters, etc.

These emulsion stabilizers may be used alone or in combination of two or more.

The content of the emulsion stabilizer in the lubricating layer 4 (total content when two or more types are used in combination) is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and particularly preferably 0.05% by mass or more. Also, it is preferably 1% by mass or less, more preferably 0.7% by mass or less, and particularly preferably 0.5% by mass or less.
Within the above range, aggregation, sedimentation and gelation of particles are unlikely to occur, which is also advantageous in terms of cost.

The lubricating layer 4 of the drilling backing plate 1 of the present invention may contain a penetrating agent. The term "penetrating agent" refers to a substance that has the effect of lowering the surface tension of a liquid.
By adding a penetrating agent to the lubricating layer 4, the coating liquid can be spread evenly over the coating surface.

Examples of penetrating agents include polyoxyethylene polyoxypropylene hexyl ether, polyoxyethylene polyoxypropylene decyl ether, polyoxyethylene polyoxypropylene isodecyl ether, polyoxyethylene polyoxypropylene glycol, perfluoroalkylene compounds, perfluorophenyl compounds, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, etc.

These penetrating agents may be used alone or in combination of two or more.

The content of the penetrant in the lubricating layer 4 (total content when two or more kinds are used in combination) is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and particularly preferably 0.05% by mass or more. Also, it is preferably 1% by mass or less, more preferably 0.7% by mass or less, and particularly preferably 0.5% by mass or less.
When the amount is within the above range, the coating liquid can be spread uniformly while suppressing foaming, and this is also advantageous in terms of cost.

The lubricating layer 4 of the drilling backing plate 1 of the present invention may contain a crystal nucleating agent.
Adding a crystal nucleating agent to the lubricating layer 4 can prevent cracking of the lubricating layer 4 due to crystal refinement. In addition, adding a crystal nucleating agent can prevent blocking (tack) caused by stickiness of the water-soluble resin when drying the lubricating layer 4 after it is formed.

Examples of crystal nucleating agents include amino acids, fatty acid esters, alkali metal salts, dicarboxylic acids, etc.

Examples of amino acids include glycine, alanine, valine, leucine, isoleucine, serine, threonine, cysteine, cystine, methionine, phenylalanine, tyrosine, tryptophan, proline, asparagine, glutamine, aspartic acid, glutamic acid, lysine, and histidine.
Among these, aspartic acid, alanine, arginine, phenylalanine, glycine, and leucine are particularly preferred because they are highly effective in preventing blocking and cracking of the lubricating layer.

Examples of fatty acid esters include sorbitan stearate, polyoxyethylene stearate, diacylglycerol, monoacylglycerol, triacylglycerol, etc.

Examples of alkali metal salts include sodium sulfate, sodium chloride, sodium silicate, sodium phosphate, sodium citrate, sodium hydroxide, potassium sulfate, potassium chloride, potassium silicate, potassium phosphate, potassium citrate, potassium hydroxide, etc.

Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid.

These crystal nucleating agents may be used alone or in combination of two or more.

The content of the crystal nucleating agent in the lubricating layer 4 (total content when two or more types are used in combination) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more. Also, it is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 1% by mass or less.
Within the above range, the effects of preventing blocking and cracking of the lubricating layer 4 are easily exerted sufficiently.

The lubricating layer 4 of the drilling backing plate 1 of the present invention may contain a water resistance imparting agent.
The water-resistance imparting agent provides the lubricating layer with an appropriate water resistance, i.e., the water-resistance imparting agent prevents the components of the lubricating layer 4 from being dissolved by moisture in the air, causing the lubricating layer 4 to peel off from the surface of the metal sheet.

Examples of water resistance agents include modified polyvinyl, polyester, polyamide, rosin, etc.

Examples of modified polyvinyls include styrene-vinyl acetate block copolymers, ethylene-vinyl acetate copolymer resins, methyl vinyl ether-maleic acid (anhydride) copolymers, anion-modified polyvinyl alcohol, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl isobutyl ether, polyvinyl acetate, polyvinylpyrrolidone vinyl acetate, polyvinylpyrrolidone, etc.

Examples of the polyester include polyester resin and vinyl ester resin.
The polyester resin preferably has a glass transition point (Tg) of about 5 to 50°C.

Examples of polyamides include polymerized fatty acid-based polyamides and polymerized petroleum-based polyamides.
The term "polymerized fatty acid polyamide" refers to a condensation product of a polymerized fatty acid (a polymer of an unsaturated fatty acid) and a diamine. Examples of unsaturated fatty acids include linoleic acid, oleic acid, ricinoleic acid, and unsaturated fatty acids contained in castor oil, soybean oil, linseed oil, etc.
"Petroleum-based polymerized polyamide" is a common polyamide made from raw materials such as ethylene, propylene, butadiene, and styrene.

Examples of rosin include WW rosin, hydrogenated rosin, rosin modified phenolic resin, maleated rosin, maleic acid modified rosin resin, ester gum, hardened rosin, rosin alkali soap, acrylated rosin, polymerized rosin, etc.

These water resistance agents may be used alone or in combination of two or more.

The content of the water resistance imparting agent in the lubricating layer 4 (total content when two or more types are used in combination) is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and particularly preferably 0.05% by mass or more. Also, it is preferably 1% by mass or less, more preferably 0.7% by mass or less, and particularly preferably 0.5% by mass or less.
Within the above range, the effect of imparting water resistance is easily achieved, and peeling of the lubricating layer 4 is unlikely to occur.

The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples as long as it does not depart from the gist of the present invention.
Details of the chemicals used in the examples and comparative examples are as follows.

"Polyurethane resin A"
A polyurethane resin having a carbonate structure and further having an aromatic hydrocarbon group in a portion derived from a polyol compound.

"Polyurethane resin B"
A polyurethane resin that does not have a carbonate structure.

"Polyethylene glycol"
Polyethylene glycol having a number average molecular weight of 1,000 or more and less than 50,000.

"Partially saponified polyvinyl acetate"
A partially saponified product of polyvinyl acetate having a degree of polymerization of 600 and a degree of saponification of 45%.

Example 1
A partially saponified polyvinyl acetate was applied to one surface of an aluminum plate having a thickness of 75 μm to a film thickness of 1.5 μm to form an undercoat layer.

Next, coating solution 1 having the following composition was applied onto the undercoat layer and dried to form a lubricating layer with a thickness of 25 μm, thereby producing a backing plate for drilling.

(Coating Solution 1 Composition)
Polyurethane resin A 13.40 parts by weight Polyethylene glycol 33.00 parts by weight Emulsion stabilizer 0.10 parts by weight Penetrating agent 0.05 parts by weight Water 47.80 parts by weight Amino acid 0.15 parts by weight Methanol 4.50 parts by weight

[Hole drilling]
A printed circuit board having a thickness of 0.8 mm was used as a sample. Four printed circuit boards were stacked, and the prepared aluminum backing plate was placed on the top printed circuit board with the lubricating layer facing upwards, and then holes were drilled using a drill.
The drill diameters used were 0.2 mm, 0.12 mm, or 0.05 mm.

Example 2
In Example 1, when forming the lubricating layer, coating liquid 2 having the following composition was used instead of coating liquid 1. In the same manner as in Example 1, a backing plate for drilling was prepared and drilling was performed using a drill.

(Composition of Coating Solution 2)
Polyurethane resin A 13.40 parts by weight Polyethylene glycol 33.00 parts by weight Water 47.80 parts by weight Amino acid 0.15 parts by weight Methanol 4.50 parts by weight

Comparative Example 1
In Example 1, when forming the lubricating layer, a backing plate for drilling was prepared in the same manner as in Example 1, except that coating liquid 3 having the following composition was used instead of coating liquid 1, and drilling was performed using a drill.

(Coating Solution 3 Composition)
Polyurethane resin B 13.40 parts by weight Polyethylene glycol 33.00 parts by weight Emulsion stabilizer 0.10 parts by weight Penetrating agent 0.05 parts by weight Water 47.80 parts by weight Amino acid 0.15 parts by weight Methanol 4.50 parts by weight

The following items were evaluated for each Example and Comparative Example. The results are shown in Table 1.

<Breakage>
The breakage of the drill was visually confirmed and evaluated according to the following criteria.

○: No breakage was observed.
△: Almost no breakage was observed.
×: Breakage was confirmed.

<Hole position>
The hole positions of the printed circuit board were evaluated according to the following criteria.

A: All were good products.
×: Many defective products were found.

<Stability>
The product stability over time was evaluated according to the following criteria:

◯: When the coating solution for forming the lubricating layer was stored at 4° C. and then stirred, no aggregates of the blended resin were generated.
×: After the coating solution for forming the lubricating layer was stored at 4° C., agglomerates of the blended resin were generated when the solution was stirred.

When the lubricating layer 4 contained polyurethane resin with a carbonate structure, no breakage occurred even when the drill diameter was small.

The drilling backing plate of the present invention is suitable for creating small through holes in printed circuit boards, and is therefore widely used in the processing of printed circuit boards used in communication devices, batteries, office automation equipment, home appliances, etc.

1 Drilling backing plate 2 Metal plate 3 Undercoat layer 4 Lubricating layer

Claims (5)

A drilling backing plate having a lubricating layer formed on at least one surface of a metal plate via an undercoat layer, the lubricating layer having a carbonate structure and further containing a polyurethane resin having an aromatic hydrocarbon group in a portion derived from a polyol compound , polyethylene glycol, an emulsion stabilizer, a penetrating agent and an amino acid (excluding the case where the lubricating layer contains a solid lubricant) . The drilling backing plate according to claim 1, wherein the content of the polyurethane resin in the lubricating layer is 10% by mass or more and 50% by mass or less. A backing plate for drilling according to claim 1 or claim 2, wherein the compound which is the main component of the undercoat layer is a partially saponified product of polyvinyl acetate having a degree of polymerization of 200 or more and 1000 or less and a degree of saponification of 15% or more and 95% or less . A coating liquid for forming a lubricating layer on the drilling backing plate described in any one of claims 1 to 3, characterized in that the coating liquid contains a polyurethane resin having a carbonate structure and further having an aromatic hydrocarbon group in a portion derived from a polyol compound, polyethylene glycol, an emulsion stabilizer, a penetrating agent, an amino acid, water and methanol. A drilling method comprising the steps of: placing a drilling backing plate according to any one of claims 1 to 3 on a printed circuit board; and using a drill to form holes having a diameter of 0.05 mm or more and 0.12 mm or less in the drilling backing plate and the printed circuit board from above the drilling backing plate.

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