CN115667592A

CN115667592A - Intermittent electroplating method

Info

Publication number: CN115667592A
Application number: CN202180039881.6A
Authority: CN
Inventors: 今井第造; 杉冈骏; 长尾敏光; 片山顺一
Original assignee: Okuno Chemical Industries Co Ltd
Current assignee: Okuno Chemical Industries Co Ltd
Priority date: 2020-06-02
Filing date: 2021-05-14
Publication date: 2023-01-31
Also published as: WO2021245766A9; WO2021245766A1; WO2021246133A1; KR20230018406A

Abstract

The invention provides a technique capable of improving filling property of a micro hole in intermittent plating. A batch plating method for a plating object having micropores includes a step of using a plating solution containing a polyvalent metal ion.

Description

Intermittent electroplating method

Technical Field

The present invention relates to an intermittent plating method and the like.

Background

In recent years, with the increase in functions and speed of electronic devices, printed circuit boards are also required to have higher densities. In the densification of printed circuit boards, a build-up process is indispensable, and among them, via (via) filling is an important plating technique. In such a build-up process, conventionally, a circuit is formed by uniformly plating a non-through via and then filling it with an insulating resin or a conductive paste. Therefore, in recent years, a process method of stacking wiring layers by filling via holes (via holes) with plating has been adopted.

On the other hand, from the viewpoint of efficiency of the plating process, particularly from the viewpoint of efficiently plating a long-sized object to be plated, a batch plating method is sometimes employed. This batch plating method is performed, for example, in a roll-to-roll production line using a plurality of plating tanks, as shown in fig. 1.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-058093

Disclosure of Invention

Technical problem to be solved by the invention

The inventors of the present invention have made studies and found that, when a plating object having minute holes such as via holes is subjected to batch plating, the degree of metal deposition (filling property) in the minute holes is remarkably low.

Accordingly, an object of the present invention is to provide a technique capable of improving the filling property of a fine hole in intermittent plating.

Technical solution for solving technical problem

The inventors of the present invention have further studied and found that the decrease in the filling property in the batch plating is caused by a phenomenon peculiar to the batch plating method, that is, a problem of low current density due to a small amount of plating solution (in the case of the embodiment shown in fig. 1, a small amount of plating solution leaking from the side surface of the plating tank) adhering to the object to be plated discharged from the plating tank and the object to be plated supplied to the plating tank. Further, the inventors of the present invention have found, in the course of further research, that the above-mentioned technical problems can be solved by using a plating solution containing polyvalent metal ions. The inventors of the present invention have further studied based on these findings, and as a result, have completed the present invention.

That is, the present invention includes the following aspects.

Item 1. A batch electroplating method to be carried out on a plated object having micropores, which comprises using a plating solution containing polyvalent metal ions.

The batch plating method according to item 1, wherein the polyvalent metal ion has a valence of 3 or more.

Item 3 the batch plating method according to item 1 or 2, wherein the polyvalent metal ion is selected from Fe ³⁺ 、V ⁵⁺ 、Mn ⁷ ⁺ 、Mo ⁶⁺ 、W ⁶⁺ 、Ce ⁴⁺ 、Cr ³⁺ 、Cr ⁶⁺ 、Ti ⁴⁺ 、Sn ⁴⁺ And Co ³⁺ At least 1 kind of (b).

The batch plating method according to any one of items 1 to 3, wherein the polyvalent metal ion is selected from Fe ³⁺ And V ⁵⁺ At least 1 kind of (1).

Item 5 the batch plating method according to any one of items 1 to 4, which continuously supplies a long-sized plated object to the plating tank on the production line, and repeats discharge of the plated object from the plating tank and supply of the plated object to the plating tank a plurality of times.

The batch plating method according to item 6, wherein the plating object is passed through a plurality of plating tanks.

An intermittent plating method according to item 5 or 6, wherein the discharging and the supplying are performed on a side surface of the plating tank.

Item 8. The intermittent plating method according to any one of items 5 to 7, which is performed on a reel-to-reel (reel-to-reel) production line.

The intermittent plating method according to any one of claims 1 to 8, wherein the micro holes are micro vias (microvia).

The batch plating method according to any one of claims 1 to 9, wherein the metal deposited on the plating object contains at least 1 selected from the group consisting of Cu, ni, and Sn.

The intermittent plating method according to any one of claims 1 to 10, wherein the plating solution further contains an additive for via filling.

Item 12. A plating solution used for the batch plating method described in any one of items 1 to 11, which contains a polyvalent metal ion.

Item 13. A batch electroplating method performed on an object to be plated having micro-pores, which includes a step of using a copper plating solution containing polyvalent metal ions and copper ions, and continuously supplies a long-sized object to be plated to a plating tank on a production line, and repeats discharge of the object to be plated from the plating tank and supply of the object to be plated to the plating tank a plurality of times, and is performed on a production line from roll to roll, and is performed under conditions that produce a low current density between the plating tanks, and includes a step of filling the micro-pores.

Effects of the invention

The present invention can provide a technique for improving filling properties of micro holes in intermittent plating, and specifically can provide an intermittent plating method, a micro hole filling method, a plating solution, and the like.

Drawings

FIG. 1 shows a schematic diagram of one embodiment of an intermittent plating process and the current pattern of the plating process.

FIG. 2 is a schematic cross-sectional view of the substrate used in test example 1-2.

FIG. 3 is a diagram showing an example of the plating cycle in test examples 1 to 3.

Fig. 4 is a cross-sectional view showing a via hole portion of an object to be plated after completion of plating of an object (a dent amount) to be measured in the evaluation of filling property.

Fig. 5 is a cross-sectional view of the via hole portion of the plated object after completion of the plating in example 2 and comparative example 3.

Detailed Description

In the present specification, expressions of "including" and "including" include concepts of "including", "substantially consisting of 8230; \8230; constitution" and "consisting of only 8230; \8230; constitution" and the like.

The present invention relates, in one aspect thereof, to a batch plating method (also referred to herein as "the batch plating method of the present invention") for plating an object to be plated having micropores, the method including a step of using a plating solution containing polyvalent metal ions.

In addition, the present invention relates, in one aspect thereof, to a plating solution used in the batch plating method of the present invention, which contains polyvalent metal ions.

Further, the present invention relates to a method for filling micropores (via filling) by intermittent plating of a plating object having micropores, which comprises a step of using a plating solution containing polyvalent metal ions.

These will be explained below.

The polyvalent metal ion is not particularly limited as long as it is a metal ion having a valence of 2 or more.

The valence number of the polyvalent metal ion is preferably 3 or more. By using a polyvalent metal ion having a valence of 3 or more, the filling property of micropores can be greatly improved. The upper limit of the valence number of the polyvalent metal ion is not particularly limited, and is, for example, 7, 6, 5 or 4.

Specific examples of the polyvalent metal ion include Fe ³⁺ 、V ⁵⁺ 、Mn ⁷⁺ 、Mo ⁶⁺ 、W ⁶⁺ 、Ce ⁴⁺ 、Cr ³⁺ 、Cr ⁶⁺ 、Ti ⁴ ⁺ 、Sn ⁴⁺ 、Co ³⁺ And the like. Among these, fe is preferably used from the viewpoint of filling property of the fine pores ³⁺ 、V ⁵⁺ 、Mn ⁷⁺ 、Mo ⁶⁺ 、W ⁶⁺ 、Ce ⁴⁺ 、Cr ³⁺ And the like. Among these, fe is particularly preferable from the viewpoint of filling property of the fine pores ³⁺ And V ⁵⁺ Particularly preferred is Fe ³⁺ 。

The polyvalent metal ion may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The plating solution containing the polyvalent metal ion can be obtained by adding a metal compound at the time of preparing the plating solution. The metal compound used is, for example, a compound obtained by obtaining a compound containing Fe ³⁺ In the case of the plating solution of (4), for example, iron (III) sulfate hydrate/anhydrate, iron (III) nitrate nonahydrate, anhydrous iron (III) bromide, iron ammonium citrate, iron (III) citrate hydrate, iron (III) oxide, iron (III) ammonium sulfate hydrate, and the like; in obtaining a compound containing V ⁵⁺ In the case of the plating solution of (4), for example, sodium metavanadate, potassium metavanadate, ammonium metavanadate and the like; to obtain a catalyst containing Mn ⁷⁺ In the case of the plating solution of (4), potassium permanganate, sodium permanganate, etc. can be mentioned, for example; to obtain a catalyst containing Mo ⁶⁺ In the case of the plating solution of (3), for example, sodium molybdate, potassium molybdate, lithium molybdate, hexaammonium heptamolybdate tetrahydrate, and the like; in order to obtain a compound containing W ⁶⁺ In the case of the plating solution of (4), for example, sodium tungstate (IV) dihydrate, sodium metatungstate, potassium tungstate, etc.; to obtain a catalyst containing Ce ⁴⁺ Examples of the plating solution of (3) include ammonium cerium (IV) nitrate, cerium (IV) sulfate hydrate/anhydrate, and tetraammonium cerium (IV) sulfate dihydrate; to obtain a material containing Cr ³⁺ In the case of the plating solution of (3), for example, chromium sulfate hydrate/anhydrate, chromium acetate, chromium potassium sulfate, and the like; to obtain a material containing Cr ⁶⁺ In the case of the plating solution of (4), for example, sodium dichromate, potassium dichromate and the like; to obtain a catalyst containing Ti ⁴⁺ In the case of the plating solution of (3), for example, titanyl sulfate and the like; to obtain a catalyst containing Sn ⁴⁺ In the case of the plating solution of (4), for example, sodium stannate trihydrate; to obtain a catalyst containing Co ³⁺ In the case of the plating solution of (3), for example, hexaammine cobalt (III) chloride and the like can be cited.

Among these metal compounds, iron (III) sulfate hydrate/anhydride, iron (III) nitrate nonahydrate, anhydrous iron (III) bromide, iron ammonium citrate, iron (III) citrate hydrate, iron (III) oxide, iron (III) sulfate hydrate, sodium metavanadate, potassium metavanadate, ammonium metavanadate, and the like are particularly preferred from the viewpoint of filling of micropores, and iron (III) sulfate hydrate/anhydride, iron (III) nitrate nonahydrate, anhydrous iron (III) bromide, iron ammonium citrate, iron (III) citrate hydrate, iron (III) oxide, ammonium iron (III) sulfate hydrate, and the like are further particularly preferred, and iron (III) sulfate hydrate/anhydride is particularly preferred.

The polyvalent metal ions contained in the plating solution may be ions whose valence number has been changed in the plating solution after addition of a metal compound (the above-mentioned metal compound or a metal compound other than the metal compound).

The metal compound may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The concentration of the polyvalent metal ion in the plating solution is not particularly limited, and is, for example, 0.01 to 20g/L. From the viewpoint of filling property of the micropores, the concentration is preferably 0.05 to 10g/L, more preferably 0.1 to 5g/L, still more preferably 0.2 to 3g/L, and still more preferably 0.5 to 3g/L. The concentration is particularly preferably 0.7 to 2.5g/L, and more preferably 0.9 to 2.2g/L, from the viewpoint of greatly improving the filling property of the fine pores.

In the batch plating method of the present invention, the metal deposited on the object to be plated is not particularly limited. Examples of the metal include Cu, ni, and Sn. Among these, cu is particularly preferable. The metal to be deposited on the plating object may be 1 kind alone or 2 or more kinds in combination.

Depending on the metal to be deposited, the plating solution contains ions of the metal to be deposited and other components such as components to be added as needed. The other components may be appropriately set according to or based on the composition of a known plating solution (e.g., a Cu plating solution (e.g., a copper sulfate bath, a copper fluoroborate bath, a copper cyanide bath, a copper pyrophosphate bath, etc.), a Ni plating solution (e.g., a double salt bath, a normal bath, a spin bath, a high sulfate salt bath, a watt bath, a perchloride bath, a sulfate-chloride bath, a total sulfate salt bath, a high quality bath, a strike nickel bath, a nickel sulfamate bath, a nickel fluoroborate bath, etc.), an Sn plating solution (e.g., an alkaline bath, a sulfuric acid bath, a sulfonic acid bath, a pyrophosphate bath, a fluoroborate bath, etc.), and the like).

Hereinafter, the Cu plating solution will be representatively explained. As the Cu plating solution, an acidic copper plating solution containing copper ions as other components and at least one acid component selected from organic acids and inorganic acids as essential components can be used.

The copper ion source in the acidic copper plating solution is not particularly limited as long as it is a copper compound soluble in the plating solution. Specific examples of such copper compounds include copper sulfate, copper oxide, copper chloride, copper carbonate, copper pyrophosphate, copper alkanesulfonate, and copper organic acid. The copper compound may be used alone or in combination of two or more. The concentration of the copper compound in the acidic copper plating solution is not particularly limited, and may be, for example, about 20 to 280 g/L. The concentration is preferably 100 to 250g/L, more preferably 150 to 230g/L.

As the acid component in the acidic copper plating solution, at least one selected from the group consisting of organic acids and inorganic acids can be used. Specific examples of the organic acid include alkanesulfonic acids such as methanesulfonic acid, alkylbenzenesulfonic acids, and the like; specific examples of the inorganic acid include sulfuric acid. These acid components may be used singly or in combination of two or more. The concentration of the acid component in the acidic copper plating solution is not particularly limited, and may be, for example, about 10 to 400 g/L. The concentration is preferably 40 to 200g/L, more preferably 70 to 150g/L.

The acidic copper plating solution preferably contains chloride ions. The concentration of the compound is usually about 10 to 200 mg/L. The concentration is preferably 25 to 100mg/L, more preferably 40 to 70mg/L. In order to fall within such a concentration range, the chloride ion concentration in the plating solution may be adjusted using hydrochloric acid, sodium chloride, or the like, as necessary.

The acidic copper plating solution may also contain various additives. Among the additives, the additive for via filling is preferable.

The plating object is not particularly limited as long as it can be plated with a fine pore. The plating object may be, for example, a substrate having a via hole.

The micro-holes are preferably micro-vias. The size of the micropores is, for example, 300 to 5 μm (preferably 150 to 30 μm) in diameter and 150 to 5 μm (preferably 100 to 20 μm) in depth. The intermittent plating method of the present invention can exhibit good filling properties even in the case of micro via holes.

In the batch plating method of the present invention, the plating object is preferably subjected to a pretreatment. The pretreatment method is not particularly limited, and a usual method may be used. For example, as the plating object, a plating object subjected to a conductive treatment (for example, electroless plating treatment, carbon treatment, sputtering treatment, sn — Pd colloidal catalyst treatment, conductive polymer treatment, or the like) may be used, for example, a plating object obtained by degreasing treatment, removal treatment of stains adhering in a previous step, removal of an oxide film by acid washing, or the like.

The plating target may be a substance on which a plating film has been formed by electroplating.

The intermittent plating method of the present invention is a method in which a current application cycle is intermittently repeated, and is not particularly limited as long as a problem of low current density due to a small amount of plating solution (in the case of the embodiment shown in fig. 1, a small amount of plating solution leaking from the side surface of the plating tank) adhering to the object to be plated discharged from the plating tank and the object to be plated supplied to the plating tank occurs.

When the current density in the plating tank is set to a high current density and the current density generated between the plating tanks is set to a low current density, the current density is high and the current density is low (both in units of A/dm) ² ) Preferably 1. Further, since the reduction in filling property is more significant, the time for generating a low current density (for example, the time for passing the object to be plated through the plating bath) is preferably 2 seconds or more, and preferably 3 seconds or more, from the viewpoint of being more suitable for the intermittent plating method of the present invention. The upper limit of the time is not particularly limited, and is, for example, 60 seconds, 30 seconds, 20 seconds, 10 seconds, or 5 seconds.

The batch plating method of the present invention is preferably a method of continuously supplying a long-sized plating object to a plating tank on a production line and repeating discharge of the plating object from the plating tank and supply of the plating object to the plating tank a plurality of times.

"continuously supplying a long-shaped plating object to a plating tank on a production line" means not sequentially supplying a plurality of divided plating objects to the plating tank, but means a method of supplying one long-shaped plating object to the plating tank from one end side of the plating object while conveying the plating object by a roller or the like.

The manner of discharging the plating object from the plating tank and supplying the plating object to the plating tank is not particularly limited. Preferably, the discharging and the supplying are performed at the side of the plating tank. In this case, when the plating object is discharged from the side wall of the plating tank, and when the plating object is supplied through the side wall of the plating tank, the plating solution inside the plating tank leaks out of the plating tank through the plating object, and the problem of the present invention (low current density) occurs.

The number of times of repeating the supply and discharge of the plating object to the plating tank is, for example, 2 to 30 times, preferably 5 to 25 times, and more preferably 10 to 20 times.

The batch plating method of the present invention is preferably a method in which the plating object is passed through a plurality of plating tanks. The number of plating tanks passed is, for example, 2 to 30, preferably 5 to 25, and more preferably 10 to 20.

The batch plating process of the present invention is preferably a process carried out on a roll-to-roll production line.

The stirring method of the plating solution is not particularly limited, and air stirring, jet stirring, mechanical stirring, and the like may be performed, or a combination of a plurality of stirring methods may be used.

In the plating treatment, any of a soluble anode and an insoluble anode can be used as the anode. For example, as the soluble anode, phosphorus-containing copper having a phosphorus content of about 0.02 to 0.06% can be used. As the insoluble anode, an anode formed by coating iridium oxide on titanium, an anode formed by plating platinum on titanium, or the like can be used. The shape of the anode is not particularly limited, and anodes having various shapes such as a rod, a sphere, a plate, and a mesh can be used.

In the plating treatment, a material to be plated can be used as a cathode.

The plating solution temperature may be generally about 10 to 50 ℃. The temperature is preferably 20 to 35 ℃.

The current density in the intermittent plating method of the present invention (current density in the plating bath) is, for example, 2 to 15A/dm ² Preferably 2 to 10A/dm ² 。

In the batch plating method of the present invention, the time for applying the current (the time for immersing a certain point of the object to be plated in the plating solution in the plating tank) per 1 time is, for example, 5 to 120 seconds, preferably 10 to 60 seconds, and more preferably 20 to 40 seconds.

The number of current application cycles in the intermittent plating method of the present invention is, for example, 2 to 30 times, preferably 5 to 25 times, and more preferably 10 to 20 times.

Examples

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Test example 1 intermittent plating test 1

< test example 1-1 preparation of electroplating solution >

Plating solutions having the compositions shown in table 1 below were prepared.

[ Table 1]

The Top Lucina series is a trade name manufactured by oha pharmaceutical industry co.

< test example 1-2 > pretreatment

A copper foil resin substrate having a thickness of 64 μm (layer constitution: copper foil 7 μm/resin (polyimide) layer 50 μm/copper foil 7 μm) was pretreated by immersing the substrate (FIG. 2) having a plurality of via holes of 100 μm diameter and 57 μm depth and maintaining conductivity on the inner wall of the via hole resin by a direct plating system of carbon in a degreasing solution (trade name: DP-320Clean, manufactured by Oneye pharmaceutical industries, ltd., 100ml/L aqueous solution) at 45 ℃ for 5 minutes, washing with water for 1 minute, and immersing in 100g/L dilute sulfuric acid for 1 minute.

< test examples 1 to 3. Electroplating >

The plating solution thus obtained was immersed in the pretreated plating object, and the plating was performed in the cycle shown in table 2. The plating conditions are shown in table 3. Low current density in Table 2Specific values of the degrees and the energization time thereof are shown in table 4. An example of such a cycle (low current density = 0.2A/dm) will be shown ² Power on time 5 seconds) is shown in fig. 3.

[ Table 2]

[ Table 3]

< test examples 1-4. Evaluation of filling Property >

After the completion of the plating, the via hole portion of the plated object was observed in cross section, and the amount of dishing in the via hole portion shown in fig. 4 was measured. Based on the measured values, the filling properties were evaluated according to the following evaluation criteria (circle: indentation amount 48 μm or less; delta: indentation amount 48 to 53 μm; and x: indentation amount 53 μm or more).

< test examples 1 to 5. Results >

The results are shown in Table 4. In table 4, the low current density indicates the low current density of the cycle in table 2, and the energization time indicates the energization time (X) of the low current density of the cycle in table 2.

[ Table 4]

As shown in table 4, when the plating was performed in a cycle in which a low current density was not generated (comparative example 1), the filling ratio was good. However, in the intermittent plating, particularly in the intermittent plating in which a long-sized object to be plated is continuously supplied to a plating tank on a production line and the discharge of the object to be plated from the plating tank and the supply of the object to be plated to the plating tank are repeated a plurality of times, it is not avoided that a low current density is generated due to a small amount of plating liquid adhering to the object to be plated discharged from the plating tank and the object to be plated supplied to the plating tank, and when this is expressed in a simulated manner (comparative examples 2 to 5), it is found that the filling property is seriously deteriorated.

Test example 2 intermittent plating test 2

Adding iron sulfate n-hydrate to the plating bath and adding Fe ³⁺ A plating liquid was prepared in the same manner as in test example 1-1 except that the concentrations were adjusted to the concentrations shown in Table 5. In addition, pretreatment, plating, and evaluation of filling property were performed in the same manner as in test example 1.

The results are shown in Table 5. In table 5, the low current density indicates the low current density in the cycle of table 2, and the energization time indicates the energization time (X) of the low current density in the cycle of table 2. Fig. 5 is a cross-sectional view of the via hole portion of the plated object after the completion of the plating in example 2 and comparative example 3.

[ Table 5]

As shown in Table 5, it is found that by using a catalyst containing Fe ³⁺ The plating solution (2) has a significantly improved filling property deterioration (comparison between comparative example 1 and comparative examples 2 to 5) due to the occurrence of a low current density.

Test example 3 intermittent plating test 3

A plating solution was prepared in the same manner as in test example 1-1, except that various metal compounds were added to the plating solution and the polyvalent metal ion concentration was adjusted to the concentration shown in table 6. In addition, pretreatment, plating, and evaluation of filling property were performed in the same manner as in test example 1. Here, the low current density in this test was 0.2A/dm ² The energization time was 5 seconds.

The results are shown in Table 6.

[ Table 6]

As shown in table 6, it is understood that the deterioration of the filling property due to the generation of a low current density (comparison of comparative example 1 and comparative examples 2 to 5) is significantly improved by using the plating solution containing the polyvalent metal ion.

Claims

1. A method of intermittent plating of a plating object having micro-pores, characterized in that: comprising the step of using a plating solution containing polyvalent metal ions.

2. An intermittent plating method according to claim 1, characterized in that:

the valence number of the polyvalent metal ion is 3 or more.

3. An intermittent plating method according to claim 1 or 2, characterized in that:

the polyvalent metal ion is selected from Fe ³⁺ 、V ⁵⁺ 、Mn ⁷⁺ 、Mo ⁶⁺ 、W ⁶⁺ 、Ce ⁴⁺ 、Cr ³⁺ 、Cr ⁶⁺ 、Ti ⁴⁺ 、Sn ⁴⁺ And Co ³⁺ At least 1 kind of (1).

4. An intermittent plating method according to any one of claims 1 to 3, characterized in that:

the polyvalent metal ion is selected from Fe ³⁺ And V ⁵⁺ At least 1 kind of (1).

5. An intermittent plating method according to any one of claims 1 to 4, characterized in that:

the long-sized plated object is continuously supplied to the plating tank on the production line, and the discharge of the plated object from the plating tank and the supply of the plated object to the plating tank are repeated a plurality of times.

6. An intermittent plating method according to claim 5, characterized in that:

the plating object passes through a plurality of plating tanks.

7. An intermittent plating method according to claim 5 or 6, characterized in that:

the discharging and the supplying are performed at the side of the plating tank.

8. An intermittent plating method according to any one of claims 5 to 7, characterized in that:

on a roll-to-roll production line.

9. An intermittent plating method according to any one of claims 1 to 8, characterized in that:

the micro holes are micro guide holes.

10. An intermittent plating method according to any one of claims 1 to 9, characterized in that:

the metal deposited on the plating object contains at least 1 kind selected from Cu, ni and Sn.

11. A batch plating method according to any one of claims 1 to 10, characterized in that:

the plating solution also contains an additive for via filling.

12. A plating solution used for the batch plating method according to any one of claims 1 to 11, characterized in that: contains polyvalent metal ions.