JP2020094237A - Intermittent electroplating method - Google Patents

Abstract

To provide a technique of improving filling property of micropores in intermittent electroplating.SOLUTION: The intermittent electroplating method for plating a plating object comprising micropores, includes using a plating solution containing a polyvalent metal ion.SELECTED DRAWING: None

Description

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

2. Description of the Related Art In recent years, as electronic devices have become more functional and faster, there has been a demand for higher density in printed wiring boards. A build-up process is indispensable for increasing the density of printed wiring boards, and via filling is an important plating technology. In such a build-up process, conventionally, non-penetrating vias were uniformly plated and then filled with insulating resin or conductive paste to form a circuit. It cannot be formed, and the degree of freedom in circuit design is lost. Therefore, in recent years, a method of stacking wiring layers by performing via filling to fill the via holes with plating has been adopted.

On the other hand, the intermittent electroplating method may be adopted from the viewpoint of improving the efficiency of the electroplating process, particularly from the viewpoint of efficiently electroplating a long object to be plated. This intermittent plating method is performed using a plurality of plating tanks on a reel-to-reel line as shown in FIG. 1, for example.

JP, 2011-058093, A

In the course of research, the present inventor shows that when intermittent electroplating is performed on an object to be plated having micropores such as via holes, the degree of metal deposition (filling property) in the micropores is significantly low. Found.

Therefore, an object of the present invention is to provide a technique for improving the filling property of micropores in intermittent electroplating.

While the present inventor is proceeding with further research, the deterioration of the filling property in the intermittent electroplating is a phenomenon peculiar to the intermittent plating method, that is, the plated object discharged from the plating tank and the plated object supplied to the plating tank. It has been found that the problem is caused by the problem of low current density due to the plating solution slightly adhering to the object (in the case of the embodiment shown in FIG. 1, the plating solution slightly leaking from the side surface of the plating tank). Then, the present inventor has found that the above problems can be solved by using a plating solution containing a polyvalent metal ion while further researching. The present inventor has completed the present invention as a result of further research based on these findings.

That is, the present invention includes the following aspects.

Item 1. An intermittent electroplating method for an object to be plated having micropores, which comprises using a plating solution containing a polyvalent metal ion.

Item 2. Item 2. The intermittent electroplating method according to Item 1, wherein the valence of the polyvalent metal ion is 3 or more.

Item 3. The polyvalent metal ion is at least one selected from the group consisting of Fe ³⁺ , V ⁵⁺ , Mn ⁷⁺ , Mo ⁶⁺ , W ⁶⁺ , Ce ⁴⁺ , Cr ³⁺ , Cr ⁶⁺ , Ti ⁴⁺ , Sn ⁴⁺ , and Co ^3+. The intermittent electroplating method according to Item 1 or 2, wherein

Item 4. Item 4. The intermittent electroplating method according to any one of Items 1 to 3, wherein the polyvalent metal ion is at least one selected from the group consisting of Fe ³⁺ and V ⁵⁺ .

Item 5. Item 1, wherein a long object to be plated is continuously supplied to the plating tank on the line, and discharge of the object to be plated from the plating tank and supply of the object to be plated to the plating tank are repeated a plurality of times. 4. The intermittent electroplating method according to any one of 4 above.

Item 6. Item 6. The intermittent electroplating method according to Item 5, wherein the object to be plated passes through a plurality of plating baths.

Item 7. Item 7. The intermittent electroplating method according to Item 5 or 6, wherein the discharging and the supplying are performed on a side surface of a plating tank.

Item 8. Item 8. The intermittent electroplating method according to any one of Items 5 to 7, which is performed on a reel-to-reel line.

Item 9. Item 9. The intermittent electroplating method according to any one of Items 1 to 8, wherein the micropores are microvias.

Item 10. Item 10. The intermittent electroplating method according to any one of Items 1 to 9, wherein the metal to be deposited on the object to be plated contains at least one selected from the group consisting of Cu, Ni, and Sn.

Item 11. Item 11. The intermittent electroplating method according to any one of Items 1 to 10, wherein the plating solution further contains a via-filling additive.

Item 12. A plating solution containing a polyvalent metal ion for use in the intermittent electroplating method according to any one of Items 1 to 11.

According to the present invention, it is possible to provide a technique for improving the filling property of micropores in intermittent electroplating, specifically, an intermittent electroplating method, a micropore filling method, a plating solution and the like.

The schematic diagram showing one Embodiment of an intermittent electroplating method, and the electric current pattern in this electroplating method are shown. It is a cross-sectional schematic diagram of the board|substrate used in Test example 1-2. It is a graph showing an example of the electroplating cycle of Test Example 1-3. FIG. 6 is a cross-sectional observation view of a via portion of an object to be plated after completion of electroplating, showing an object (amount of depression) to be measured in evaluation of filling property. 5 is a cross-sectional observation view of a via portion of an object to be plated after completion of electroplating in Example 2 and Comparative Example 3. FIG.

In this specification, the expressions "containing" and "including" include the concepts of "containing", "including", "consisting essentially of" and "consisting solely of".

In one aspect thereof, the present invention provides an intermittent electroplating method for a plated object having micropores, which comprises using a plating solution containing a polyvalent metal ion (in the present specification, "intermittent of the present invention. "Electroplating method").

The present invention also relates, in one aspect thereof, to a plating solution containing a polyvalent metal ion for use in the intermittent electroplating method of the present invention.

Furthermore, the present invention relates to a method for filling micropores (via filling) by intermittent electroplating on an object to be plated having micropores, which comprises using a plating solution containing polyvalent metal ions.

These will be described below.

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

The valence 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 the micropores can be significantly improved. The upper limit of the valence of the polyvalent metal ion is not particularly limited and is, for example, 7, 6, 5, 4.

Specific examples of polyvalent metal ions include Fe ³⁺ , V ⁵⁺ , Mn ⁷⁺ , Mo ⁶⁺ , W ⁶⁺ , Ce ⁴⁺ , Cr ³⁺ , Cr ⁶⁺ , Ti ⁴⁺ , Sn ⁴⁺ , Co ³⁺ . Of these, Fe ³⁺ , V ⁵⁺ , Mn ⁷⁺ , Mo ⁶⁺ , W ⁶⁺ , Ce ⁴⁺ , Cr ^{3+ and the} like are preferable from the viewpoint of the filling property of the micropores. Among them, Fe ³⁺ and V ⁵⁺ are particularly preferable, and Fe ³⁺ is particularly preferable, from the viewpoint of the filling property of the micropores.

The polyvalent metal ions may be used alone or in combination of two or more.

The plating solution containing polyvalent metal ions can be obtained by adding a metal compound when the plating solution is prepared. As a metal compound used, for example, when a plating solution containing Fe ³⁺ is to be obtained, for example, iron (III) sulfate hydrate/anhydrous, iron nitrate (III) nonahydrate, iron bromide (III) ) Anhydrous, ammonium iron citrate, iron(III) citrate hydrate, iron(III) oxide, iron(III) ammonium sulfate hydrate, etc. may be mentioned; if a plating solution containing V ⁵⁺ is obtained, for example: sodium metavanadate, potassium metavanadate, cited and ammonium metavanadate; Mn potassium Invite example permanganic acid in the case of obtaining a plating ^{solution 7+} containing, sodium permanganate and the like can be mentioned are: a plating solution Mo ⁶⁺ containing If it is obtained, for example, sodium molybdate, potassium molybdate, lithium molybdate, ^{hexaammonium heptamolybdate} tetrahydrate, etc. may be mentioned; if a plating solution containing W ⁶⁺ is to be obtained, for example, tungsten (IV) acid Sodium dihydrate, sodium metatungstate, potassium tungstate, etc. may be mentioned; if a plating solution containing Ce ⁴⁺ is to be obtained, for example, cerium (IV) ammonium nitrate, cerium (IV) sulfate hydrate/anhydrate , Tetraammonium cerium (IV) sulfate dihydrate and the like; when a plating solution containing Cr ³⁺ is obtained, for example, chromium sulfate hydrate/anhydride, chromium acetate, potassium sulfate potassium, etc. may be mentioned; When a plating solution containing Cr ⁶⁺ is obtained, for example, sodium dichromate, potassium dichromate and the like are included; when a plating solution containing Ti ⁴⁺ is obtained, for example, titanyl sulfate is included; Sn ^{4+ is included} In the case of obtaining a plating solution to be used, for example, sodium stannate trihydrate and the like can be mentioned; in the case of obtaining a plating solution containing Co ^3+, for example, hexaamminecobalt (III) chloride and the like can be mentioned.

Among these metal compounds, iron(III) hydrate/anhydrous, iron(III) nitrate nonahydrate, iron(III) bromide anhydrous, and citric acid are particularly preferable from the viewpoint of micropore filling properties. Examples thereof include ammonium iron acidate, iron(III) citrate hydrate, iron(III) oxide, iron(III) ammonium sulfate hydrate, sodium metavanadate, potassium metavanadate, ammonium metavanadate, and the like, and particularly preferably sulfuric acid. Iron(III) hydrate/anhydrate, Iron(III) nitrate nonahydrate, Iron(III) bromide anhydrous, Ammonium iron citrate, Iron(III) citrate hydrate, Iron(III) oxide, Ammonium iron(III) sulfate hydrate and the like are mentioned, and particularly preferable is iron(III) sulfate hydrate/anhydrate.

The polyvalent metal ion contained in the plating solution may be one whose valence has changed in the plating solution after the addition of the metal compound (the above metal compound or another metal compound).

The metal compounds may be used alone or in combination of two or more.

The concentration of the polyvalent metal ion in the plating solution is not particularly limited, but is, for example, 0.01 to 20 g/L. The concentration is preferably 0.05 to 10 g/L, more preferably 0.1 to 5 g/L, still more preferably 0.2 to 3 g/L, and even more preferably 0 from the viewpoint of the filling property of the micropores. It is 0.5 to 3 g/L. The concentration is particularly preferably 0.7 to 2.5 g/L (more preferably 0.9 to 2.2 g/L) from the viewpoint that the filling property of the micropores can be greatly improved.

In the intermittent 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, Sn and the like. Among these, Cu is particularly preferable. The metal to be deposited on the object to be plated may be a single type or a combination of two or more types.

In accordance with the metal to be deposited, the plating solution contains ions of the metal to be deposited and other components such as components to be blended if necessary. Other components are known electroplating solutions (eg, Cu plating solution (eg, copper sulfate bath, copper bromide bath, copper cyanide bath, copper pyrophosphate bath, etc.), Ni plating solution (eg, double salt bath, ordinary bath). , Rotating bath, high sulfate bath, Watt bath, total chloride bath, sulfate-chloride bath, total sulfate bath, high quality bath, strike nickel bath, nickel sulfamate bath, nickel bromide bath, etc.), It can be appropriately set according to or in accordance with the composition of the Sn plating solution (for example, an alkaline bath, a sulfuric acid bath, a sulfonic acid bath, a pyrophosphoric acid bath, a fluorinated bath, etc.).

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

As the copper ion source in the acidic copper plating solution, any copper compound soluble in the plating solution can be used without particular limitation. Specific examples of such a copper compound include copper sulfate, copper oxide, copper chloride, copper carbonate, copper pyrophosphate, copper alkane sulfonate, copper alkanol sulfonate, and organic acid copper. The copper compounds may be used alone or in combination of two or more. The copper compound concentration in the acidic copper plating solution is not particularly limited, but may be in the range of about 20 to 280 g/L, for example. The concentration is preferably 100 to 250 g/L, more preferably 150 to 230 g/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 alkane sulfonic acid such as methane sulfonic acid, alkanol sulfonic acid and the like, and specific examples of the inorganic acid include sulfuric acid and the like. These acid components can be used alone or in combination of two or more. The concentration of the acid component in the acidic copper plating solution is not particularly limited, but may be, for example, about 10 to 400 g/L. The concentration is preferably 40 to 200 g/L, more preferably 70 to 150 g/L.

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

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

The object to be plated is not particularly limited as long as it is an object to be plated having micropores and can be electroplated. Examples of the object to be plated include a substrate having a via hole.

The micropores are preferably microvias. The size of the micropores is, for example, a diameter of 300 to 5 μm (preferably 150 to 30 μm) and a depth of 150 to 5 μm (preferably 100 to 20 μm). According to the intermittent electroplating method of the present invention, good filling properties can be exhibited even for microvias.

In the intermittent electroplating method of the present invention, the object to be plated is preferably pretreated. The pretreatment method is not particularly limited and may be a conventional method. For example, for the object to be plated that has been made conductive (for example, electroless plating, carbon treatment, sputtering treatment, Sn-Pd colloidal catalyst treatment, conductive polymer treatment, etc.), for example, degreasing treatment, dirt attached in the previous step The material obtained through the removal treatment of 1), the removal of the oxide film by pickling, etc. can be used as the object to be plated.

The object to be plated may already have a plated film formed by electroplating.

The intermittent electroplating method of the present invention is a method in which a current addition cycle is repeated intermittently, and a plating solution slightly attached to the object to be plated discharged from the plating tank and the object to be supplied to the plating tank. In the case of the embodiment shown in FIG. 1, the method is not particularly limited as long as it is a method that causes a problem of low current density due to the plating solution slightly leaking from the side surface of the plating tank.

The intermittent electroplating method of the present invention is preferably such that a long object to be plated is continuously supplied to a plating tank on a line, and discharge of the object to be plated from the plating tank and the object to be plated to the plating tank are performed. Is a method in which the supply of is repeated multiple times.

"Long-sized objects to be plated are continuously supplied to the plating tank on the line" does not mean that a plurality of mutually separated objects to be plated are sequentially supplied to the plating tank, but one long object It means a mode in which the object to be plated is fed to the plating tank from one end side of the object to be plated while being transported by a roller or the like.

The mode of discharging the object to be plated from the plating tank and supplying the object to be plated to the plating tank is not particularly limited. It is preferable that the discharging and the supplying are performed on the side surface of the plating tank. In this case, when the object to be plated is discharged from the side wall of the plating tank and when the object to be plated is supplied through the side wall of the plating tank, the plating solution inside the plating tank passes through the object to be plated. And then leaks out of the plating tank, causing a problem in the present invention (occurrence of low current density).

The number of times that the material to be plated is supplied to and discharged from the plating tank is, for example, 2 to 30 times, preferably 5 to 25 times, and more preferably 10 to 20 times.

The intermittent electroplating method of the present invention is preferably a method in which an object to be plated passes through a plurality of plating tanks. The number of plating baths to pass is, for example, 2 to 30, preferably 5 to 25, and more preferably 10 to 20.

The intermittent electroplating method of the present invention is preferably a method performed on a reel-to-reel line.

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

When performing the plating treatment, both a soluble anode and an insoluble anode can be used as the anode. For example, as the soluble anode, for example, phosphorus-containing copper having a phosphorus content of about 0.02 to 0.06% can be used. The insoluble anode may be titanium coated with iridium oxide, titanium plated with platinum, or the like. The shape of the anode is also not particularly limited, and various shapes such as rod-shaped, spherical, plate-shaped, and mesh-shaped anodes can be used.

An object to be plated can be used as the cathode when performing the plating treatment.

The liquid temperature of the plating solution may be usually about 10 to 50°C. The temperature is preferably 20 to 35°C.

The current density (current density in the plating tank) in the intermittent electroplating method of the present invention is, for example, ^{2 to} 15 A/dm ² , and preferably ² to 10 A/dm ² .

In the intermittent electroplating method of the present invention, the time per current addition (time when one point in the object to be plated is immersed in the plating solution in the plating tank) is, for example, 5 to 120 seconds, preferably 10 It is 60 seconds, more preferably 20-40 seconds.

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

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

Test Example 1. Intermittent electroplating test 1
<Test Example 1-1. Preparation of electroplating solution>
An electroplating solution having the composition shown in Table 1 below was prepared.

<Test Example 1-2. Pretreatment>
A copper foil resin substrate having a thickness of 64 μm (layer structure: copper foil 7 μm/resin (polyimide) layer 50 μm/copper foil 7 μm) has a large number of via holes with a diameter of 100 μm and a depth of 57 μm, and carbon direct play on the inner wall of the via hole resin. A substrate (FIG. 2) made conductive by a coating system is used as an object to be plated, and this is added to a degreasing liquid (trade name: DP-320 Clean, Okuno Chemical Industries Co., Ltd., 100 ml/L aqueous solution) at 45° C. After soaking for 1 minute, it was washed with water for 1 minute and then immersed in 100 g/L of dilute sulfuric acid for 1 minute for pretreatment.

<Test Example 1-3. Electroplating>
The object to be plated after pretreatment was immersed in the electroplating solution obtained above, and electroplating was performed in the cycle shown in Table 2. The plating conditions are as shown in Table 3. Table 4 shows specific values of the low current density and the energization time in Table 2. A graph showing an example of this cycle (low current density=0.2 A/dm ² , energization time 5 seconds) is shown in FIG.

<Test Example 1-4. Filling evaluation>
After completion of the electroplating, the cross section of the via portion of the object to be plated was observed, and the amount of depression of the via portion shown in FIG. 4 was measured. Based on the measured values, the filling property was evaluated according to the following evaluation criteria (◯: dent amount 48 μm or less, Δ: dent amount: 48 to 53 μm, x: dent amount 53 μm or more).

<Test Example 1-5. Result>
The results are shown in Table 4. In Table 4, the low current density represents the low current density in the cycle of Table 2, and the energization time represents the energization time (X) of the low current density in the cycle of Table 2.

As shown in Table 4, when electroplating was performed in a cycle in which a low current density was not generated (Comparative Example 1), the filling property was relatively good. However, intermittent electroplating, particularly long-sized objects to be plated are continuously supplied to the plating tank on the line, and the objects to be plated from the plating tank and the objects to be plated are supplied to the plating tank. In intermittent electroplating that is repeated multiple times, where a low current density is inevitable due to the plating solution discharged from the plating tank and the plating solution slightly attached to the plating object supplied to the plating tank, It was found that when these cases were simulated (Comparative Examples 2 to 5), the filling property was significantly deteriorated.

Test example 2. Intermittent electroplating test 2
An electroplating solution was prepared in the same manner as in Test Example 1-1, except that ferric sulfate n-hydrate was added to the electroplating solution to adjust the Fe ³⁺ concentration to the concentration shown in Table 5. Others were the same as in Test Example 1, and pretreatment, electroplating, and filling property evaluation were performed.

The results are shown in Table 5. In Table 5, the low current density represents the low current density in the cycle of Table 2, and the energization time represents the energization time (X) of the low current density in the cycle of Table 2. Further, FIG. 5 shows a cross-sectional observation view of the via portion of the object to be plated after completion of electroplating in Example 2 and Comparative Example 3.

As shown in Table 5, the deterioration of the filling property due to the occurrence of low current density (comparison between Comparative Example 1 and Comparative Examples 2 to 5) is significantly improved by using the plating solution containing Fe ^3+. I found out.

Test example 3. Intermittent electroplating test 3
An electroplating solution was prepared in the same manner as in Test Example 1-1, except that the polyvalent metal ion concentration was adjusted to the concentration shown in Table 6 by adding various metal compounds to the electroplating solution. Others were the same as in Test Example 1, and pretreatment, electroplating, and filling property evaluation were performed. The low current density in this test is 0.2 A/dm ² , and the energization time is 5 seconds.

The results are shown in Table 6.

As shown in Table 6, the deterioration of the filling property due to the generation of the low current density (comparison between Comparative Example 1 and Comparative Examples 2 to 5) is significantly caused by using the plating solution containing polyvalent metal ions. It turned out to improve.

Claims (12)

An intermittent electroplating method for an object to be plated having micropores, which comprises using a plating solution containing a polyvalent metal ion. The intermittent electroplating method according to claim 1, wherein the valence of the polyvalent metal ion is 3 or more. The polyvalent metal ion is at least one selected from the group consisting of Fe ³⁺ , V ⁵⁺ , Mn ⁷⁺ , Mo ⁶⁺ , W ⁶⁺ , Ce ⁴⁺ , Cr ³⁺ , Cr ⁶⁺ , Ti ⁴⁺ , Sn ⁴⁺ , and Co ^3+. The intermittent electroplating method according to claim 1 or 2, wherein The intermittent electroplating method according to claim 1, wherein the polyvalent metal ion is at least one selected from the group consisting of Fe ³⁺ and V ⁵⁺ . The long-shaped object to be plated is continuously supplied to the plating tank on the line, and discharging the object to be plated from the plating tank and supplying the object to be plated to the plating tank are repeated a plurality of times. 4. The intermittent electroplating method according to any one of 4 to 4. The intermittent electroplating method according to claim 5, wherein the object to be plated passes through a plurality of plating baths. The intermittent electroplating method according to claim 5 or 6, wherein the discharging and the supplying are performed on a side surface of a plating tank. The intermittent electroplating method according to claim 5, which is performed on a reel-to-reel line. The intermittent electroplating method according to claim 1, wherein the micropores are microvias. The intermittent electroplating method according to any one of claims 1 to 9, wherein the metal to be deposited on the object to be plated contains at least one selected from the group consisting of Cu, Ni, and Sn. The intermittent electroplating method according to claim 1, wherein the plating solution further contains an additive for via filling. A plating solution containing a polyvalent metal ion for use in the intermittent electroplating method according to claim 1.