TWI569704B - Method for pomoting adhesion between dielectric substrates and metal layers - Google Patents

Description

Method for improving adhesion between dielectric substrate and metal layer

This invention relates to a novel method of coating a surface of a dielectric substrate with a decane composition. The method produces a metallized surface that exhibits a high degree of adhesion between the substrate and the plated metal while preserving a smooth substrate surface integrity.

A variety of methods for metallizing dielectric substrate surfaces are known. In the wet chemical process, after appropriate pretreatment, the surface to be metallized is first catalyzed and then metallized in an electrodeless manner, and thereafter electrolytic metallization or direct electrolytic metallization if necessary.

In EP 0 616 053 A1, a method for directly metallizing the surface of a dielectric substrate is disclosed, wherein the surface is first treated with a detergent/regulator solution, and thereafter treated with an activator solution (for example a palladium gel solution), stabilized by a tin compound And then treated with a solution containing a compound which is more expensive than tin and an alkali metal hydroxide and a complex forming agent. Thereafter, the surface can be treated in a solution containing a reducing agent and finally electrolytically metallized.

WO 96/29452 relates to a method for selectively or partially electrolytically metallizing the surface of a substrate made of a non-conductive (i.e. dielectric material) for the purpose of coating a method for the safety of a plastic coated holding element. The proposed method comprises the steps of: a) pretreating the surface with an etching solution containing chromium (VI); then immediately b) treating the surface with a colloidal acidic solution of palladium/tin compound, carefully preventing the prior adsorption and adsorption promoting solution Contact; c) containing a compound capable of being reduced by a tin (II) compound, an alkali metal or alkaline earth metal hydroxide, and a complex forming agent The solution of the soluble metal compound treats the surface in an amount at least sufficient to prevent precipitation of the metal hydroxide; d) treating the surface with an electrolytic metallization solution. The method is particularly suitable for ABS (acrylic butadiene styrene) and ABS/PC (polycarbonate) based plastic substrates.

Alternatively, a conductive polymer can be formed on the surface of the dielectric substrate to provide a first conductive layer for subsequent metal plating of the surface.

US 2004/0112755 A1 describes direct electrolytic metallization of a surface of a non-conductive substrate comprising contacting a surface of the substrate with a water soluble polymer (eg thiophene); treating the surface of the substrate with a permanganate solution; containing at least one thiophene compound and at least An acidic aqueous solution of an alkane sulfonic acid comprising a group of methanesulfonic acid, ethanesulfonic acid and ethane disulfonic acid or an acidic microemulsion of an aqueous base to treat the surface of the substrate; electrolytically metallizing the surface of the substrate.

US 5,693,209 relates to a method for directly metallizing a circuit board having a non-conductor surface, comprising reacting a non-conductor surface with an alkaline permanganate solution to form manganese dioxide chemically adsorbed on a non-conductor surface; forming a weak acid and An aqueous solution of a pyrrole or pyrrole derivative and a soluble oligomer thereof; contacting an aqueous solution containing a pyrrole monomer and an oligomer thereof with a non-conductor surface on which a manganese dioxide is chemically adsorbed to deposit adhesion on a non-conductor surface a conductive, insoluble polymer product; and directly electrodepositing the metal on the non-conducting surface on which the insoluble, adherent polymer product is formed. The oligomer is advantageously formed in an aqueous solution containing from 0.1 to 200 g/l of a pyrrole monomer at a temperature between room temperature and the freezing point of the solution.

US 4,976,990 relates to the metallization of the surface of a dielectric substrate, in particular the electrodeless metallization of the surface of the through-hole of a double-sided or multilayer printed circuit board. The method includes roughening the surface and subsequently applying a decane composition to the treated surface. If the method is carried out in this sequential processing step, substantial roughening of the surface occurs. The method disclosed in this patent includes a microetching solution (lines 61 to 65) for removing an oxide film from a metal foil. However, this method is not suitable for obtaining good adhesion between the substrate material of the method of the invention and the subsequently plated metal layer.

A similar method is disclosed in WO 88/02412.

EP 0 322 233 A2 relates to a method for producing an ultrafine pattern of a silver metal film on a substrate by coating a polymerizable solution containing decane or diborane in a solution containing sodium hydroxide and hydrogen peroxide. The silver metal layer is etched and finally coated. This method is not suitable for producing an adhesive metal film for the substrate of the method of the present invention.

All of the methods described require substantial roughening of the surface of the non-conductive dielectric substrate prior to metallization to ensure adequate adhesion between the substrate and the plated metal layer. Roughening is generally considered essential as it is used to prepare the surface of a dielectric substrate. This is because it is believed that roughening is necessary to achieve good adhesion between the substrate and the metal layer.

However, rough surfaces impart metal plating surface functionality, for example as regards their use as wires in electronic applications.

The continued miniaturization of features of HDI printed circuit boards, IC substrates, and the like requires a more advanced manufacturing method than conventional methods such as forming circuits by printing and etching methods. These features only require that the surface of the substrate be roughened to a limited extent.

Accordingly, it is an object of the present invention to provide a method of metallizing a dielectric substrate surface without substantially roughening the surface while still achieving high adhesion between the substrate and the metal layer.

This object is achieved by a method of treating the surface of a dielectric substrate to prepare the surface for subsequent wet chemical metal plating, the method comprising the steps of: (i) using at least one organodecane compound; Treating the surface with a solution; (ii) treating the surface with a solution comprising an oxidizing agent selected from acidic or basic aqueous solutions of permanganate; and subsequently (iii) metallizing the substrate by wet chemical plating after step (ii) .

1‧‧‧Dielectric structural layer

2‧‧‧ Copper Area/Contact Area

3‧‧‧Second dielectric layer

4‧‧‧ openings

5a‧‧‧ top surface

5b‧‧‧ sidewall

6‧‧‧ Conductive layer / conductive seed layer

7‧‧‧ patterned resist layer

8‧‧‧Bronze/Electroplating Copper

Figure 1 shows a thin wire circuit for manufacturing a semi-additive method (SAP) known in the art. method.

2 shows the surface of the GX92 substrate material after permanganate treatment according to Example P12.

Figure 3 shows the surface of a GX92 substrate material after permanganate treatment with an alkaline permanganate solution, according to conditions known in the art.

According to the invention, the substrate is first treated with a composition comprising an organodecane compound in step (i).

The organic decane compound to be coated is in the form of a solution, preferably a solution having a high boiling point organic solvent, preferably having a boiling point in the range of 60 to 250 ° C and more preferably in the range of 80 to 200 ° C. The organic solvent within the meaning of the present invention is a polar organic solvent suitable for dissolving a decane compound.

Suitable organic solvents include alcohols, ethers, amines and acetates. Examples are ethanol, 2-propanol, tetrahydrofuran, ethylene glycol, diethylene glycol, 2-isopropoxyethanol (IPPE), di(propylene glycol) methyl ether acetate (DPGMEA), 2-ethyl-1 -hexanol, glycerol, dioxin, butyrolactone, N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, ethanolamine, propylene glycol methyl ether acetate (PMA) ), half ether and half ester of ethylene glycol.

The concentration of the organic decane varies widely depending on the coating method and the specific organodecane compound. Suitable concentrations can be obtained by routine experimentation. Suitable concentrations are generally varied between as low as 0.2 wt.% to 30 wt.%, preferably between 0.5 wt.% and 20 wt.%, even more preferably between 1 wt.% and 8 wt.%.

Contacting the dielectric substrate with the solution containing the organodecane according to method step (i) is carried out by dipping or immersing the substrate in the solution or by spraying the solution onto the substrate. According to method step (i), the substrate is contacted with the solution containing the organodecane at least once. Alternatively, the contacting can be carried out several times, preferably 2 to 10 times, more preferably 2 to 5 times, even more preferably 1 to 3 times. The best contact is once or twice.

According to method step (i), contacting the substrate with the solution containing the organodecane is carried out for a period of from 10 seconds to 20 minutes, preferably from 10 seconds to 10 minutes, and most preferably from 10 seconds to 5 minutes.

According to method step i, the substrate is contacted with the solution containing the organodecane at a temperature in the range of 15 to 100 ° C, preferably 20 to 50 ° C, and most preferably 23 to 35 ° C.

The organodecane compound is preferably selected from the group consisting of: A _(4-x) SiB _x

Wherein each A is independently a hydrolyzable group, x is from 1 to 3, and each B is independently selected from the group consisting of C ₁ -C ₂₀ alkyl, aryl, aminoaryl and represented by Functional group: C _n H _2n X, wherein n is from 0 to 15, preferably from 0 to 10, even more preferably from 1 to 8, most preferably 1, 2, 3, 4, and X is selected from the group consisting of Group: amine, decyl, hydroxy, alkoxy, halo, decyl, carboxy, carboxy ester, formamide, thioformamide, fluorenyl, vinyl, allyl, styryl, ring Oxygen, epoxycyclohexyl, glycidoxy, isocyanate, thiocyano, thioisocyanyl, ureido, thioureido, sulfhydryl, thiol, propylene methoxy, methacryloxy Or X is a residue of a carboxy ester; or X is Si(OR) ₃ , and wherein R is a C ₁ -C ₅ alkyl group.

The hydrolyzable group A is preferably selected from the group consisting of -OH, -OR ¹ , and wherein R ¹ is C ₁ -C ₅ alkyl, -(CH ₂ ) _y OR ² , and wherein y is 1, 2 or 3 And R ² is H or C ₁ -C ₅ alkyl, -OCOR ³ , and wherein R ³ is H or C ₁ -C ₅ alkyl.

If B is an alkyl group, it is preferably a C ₁ -C ₁₀ alkyl group, even more preferably a C ₁ -C ₅ alkyl group such as a methyl group, an ethyl group, a propyl group or an isopropyl group. The aryl group is preferably a substituted or unsubstituted phenyl group and a benzyl group. Preferred aryl is group -NH (C ₆ H _5).

The functional group X within the meaning of the present invention may be further functionalized. For example, the X = amine group comprises an amine substituted with an alkylamine or an arylamine, such as 3-(N-styrylmethyl-2-aminoethylamine).

With respect to the functional group X being Si(OR) ₃ , R is preferably a methyl group, an ethyl group, a propyl group or an isopropyl group.

Examples of specific classes of compounds in the above formula are vinyl decane, aminoalkyl decane, ureido alkyl decyl ester, epoxy alkyl decane and methacryl alkyl decyl ester, wherein the reactive organic functional groups are Vinyl, amine, ureido, epoxy and methacryloxy. Examples of vinyl decane are vinyl trichloromethane, vinyl triethoxy decane, vinyl trimethoxy decane, vinyl ginseng-(β(2)-methoxyethoxy) decane and vinyl three. Ethoxy decane. Examples of the aminoalkyldecane which is a preferred organic decane for use in the present invention are γ(3)-aminopropyltriethoxydecane, γ-aminopropyltrimethoxydecane, and N-β-. (Aminoethyl)-γ-aminopropyltrimethoxydecane and N'-(β-aminoethyl)-N-(β-aminoethyl)-γ-aminopropyltrimethoxy Decane. Suitable ureidoalkyl decyl esters are gamma ureidoalkyl triethoxy decanes, and suitable ethoxyalkyl decanes are β-(3,4-epoxycyclohexyl)-ethyltrimethoxy decane and Γglycidoxypropyltrimethoxydecane. Suitable methacryloxy decyl methacrylates are γ-methacryloxypropyltrimethoxydecane and γ-methylpropenyloxypropyl-para-(β-methoxyethoxy)decane.

The at least one organodecane compound may be a monomeric organodecane compound or an oligomeric organodecane compound obtained by (partial) hydrolysis and condensation of a monomeric organodecane compound according to the present invention prior to deposition on a surface of a dielectric substrate.

Hydrolysis and condensation of organodecane compounds are well known in the art. For example, a monomeric organodecane compound is reacted with an acidic catalyst such as acetic acid or dilute hydrochloric acid to produce a clear solution of the oligomeric organodecane compound derived from the monomeric organodecane compound.

Such oligodecane derived from the monomeric organodecane compound according to the present invention by hydrolysis should be included in the scope of the present invention.

Optionally, the substrate can be heat treated after method step (i). This treatment is usually carried out at a temperature between 60 and 200 ° C, more preferably between 80 and 150 ° C. The treatment time can vary, for example, between 1 and 30 minutes, preferably between 1 and 10 minutes.

Thereafter, the substrate is treated with a solution comprising an oxidizing agent selected from the group consisting of acidic or basic aqueous solutions of permanganate in step (ii).

It has been unexpectedly discovered that other oxidizing agents other than permanganate (e.g., a mixture of hydrogen peroxide and sulfuric acid or chromic acid) are not suitable for the process of the present invention because they do not produce sufficient adhesion between the substrate and the subsequently plated metal layer. This is unexpected because the prior art teaches that all oxidants essentially produce the same surface modification.

An alkaline solution of permanganate such as sodium permanganate or potassium permanganate is preferred. The solution preferably contains from 20 to 100 g/l of permanganate ion and from 10 to 40 g/l of hydroxide ion. Preferably, the source of hydroxide ions is sodium hydroxide or potassium hydroxide.

The contacting of the dielectric substrate with the solution containing the oxidizing agent according to method step (ii) is carried out by dipping or immersing the substrate in the solution or by spraying the solution onto the substrate.

The substrate is contacted with the solution containing the oxidizing agent according to method step (ii) for a period of time ranging from 30 seconds to 30 minutes, preferably from 30 seconds to 10 minutes.

The contacting of the substrate with the solution containing the oxidizing agent is carried out according to method step (ii) at a temperature in the range of from 20 to 95 ° C, preferably from 50 to 85 ° C.

In one embodiment of the invention, the method comprises the steps of: (i) treating the surface with a solution comprising at least one organodecane compound at a temperature between 15 and 50 ° C for a period of between 10 s and 10 min, ( Ii) treating the surface with a solution comprising an oxidizing agent selected from an alkaline aqueous solution of permanganate ions at a concentration of 20-100 g/l at a temperature between 20 and 95 ° C for a period of between 1 and 30 min, A roughened surface having an average surface roughness Ra of less than 150 nm was obtained.

The surface roughness Ra of less than 150 nm may be between 50 and 150 nm, preferably between 60 and 130 nm and even more preferably between 70 and 120 nm.

Various dielectric substrates can be metallized by the method of the present invention. Metallization is carried out by a wet chemical plating method. The plating method includes an electrodeless, immersion, and electrolytic plating method, usually performed in an aqueous solution.

The dielectric substrate to be metallized may be selected from the group consisting of plastic, plastic-glass, and plastic-ceramic composites.

The plastic may be selected from the group consisting of acrylonitrile-butadiene-styrene-copolymer (ABS copolymer); polyamine; a mixture of ABS copolymer and at least one other polymer different from the ABS copolymer; Carbonate (PC); ABS/PC blend; epoxy resin; bis-xenylenediamine-triazine resin (BT); cyanate resin; polyimine; Ester (PET); polybutylene terephthalate (PBT); polylactic acid (PLA); polypropylene (PP); and polyester.

In addition, a dielectric substrate for manufacturing a printed circuit board can be used. The material is typically composed of an epoxy-based material (eg, an epoxy blend such as an epoxy-benzotriazole blend, an epoxy-cyanate-blend, an epoxy-propylene blend, or an epoxy- Polyimine blend) composition.

With regard to step (iii), a number of methods are known to those skilled in the art for electroplating a metal onto a substrate by applying a wet chemical plating method. According to the present invention, the wet chemical plating method is preferably an electrolytic plating method, an immersion plating method or an electrodeless plating method.

The dielectric substrate (e.g., plastic article) can be subsequently metallized by activation using an electrodeless metallization process or by using a direct plating process (electrolytic plating process). The article is first cleaned, followed by, for example, a precious metal or a conductive polymer, and then finally metallized.

The usual activation of a dielectric substrate such as a printed circuit board for subsequent metal plating is performed as follows: The first conductive layer preferably comprises copper and is deposited by electroless electroplating. In this case, the substrate is preferably activated by, for example, depositing a colloid containing a noble metal or a solution containing a noble metal ion before electrodeless copper deposition. The best activation is by depositing palladium-tin colloid or palladium ions. These methods are well established in the art and are known to the skilled person.

The first conductive layer may comprise nickel instead of copper.

Exemplary and non-limiting pretreatment methods, particularly for printed circuit board laminates and other suitable substrates, can include the steps of: a) contacting the substrate with an activator solution that causes the surface of the substrate to become catalytic. a colloidal or ion-catalyzed metal, such as a noble metal, preferably palladium, and optionally, if the activator contains an ion-catalyzed metal, b) contacting the substrate with a reducing agent, wherein the metal ion of the ion activator is reduced to an element The metal, or, if the activator contains a colloidal catalytic metal, c) contacts the substrate with an accelerator wherein the components of the colloid, such as a protective colloid, are removed from the catalytic metal.

The method of the present invention is specifically adapted to fabricate thin wire circuits. This is shown in Figure 1.

One method of fabricating a thin wire circuit known in the art is a semi-additive process (SAP) which begins with a bare dielectric structure layer (1) having a copper region on at least a portion of the back side, which may be, for example, The contact region (2) is attached and the second dielectric layer (3) is attached to the back side of the dielectric construction layer (1). Such a substrate is shown in Figure 1a. At least one opening (4) is formed by, for example, laser drilling in the structural layer (1), such as a blind microwell extending through the substrate to a copper region (2) on the back side of the structural layer (1) (Fig. 1b) ). The dielectric surface of the structural layer (1) is subjected to a decontamination process in the next step, which results in a roughened surface of the roughened top surface (5a) of the structural layer (1) and the dielectric sidewall of at least one opening (4) (5b) (Fig. 1c).

It is desirable to further activate the roughened top surface (5a) and the roughened sidewall (5b) by, for example, depositing a noble metal-containing activator for continuous electroless copper plating. Next, a conductive seed layer (6) (usually made of copper) is deposited by electrodeless plating on the roughened top surface (5a) of the structural layer (1) and the roughened sidewall (5b) of the at least one opening (4) On (Figure 1d). The thickness of such a conductive layer (6) is typically from 0.8 μm to 1.5 μm, which a) is required to provide sufficient conductivity on the roughened top surface (5a) for continuous electroplating of copper and b) to ensure during electrodeless electroplating of copper Also The roughened sidewalls (5b) of the at least one opening (4) provide sufficient conductivity.

And then selectively plating the thick copper layer (8) to the patterned resist layer (7) on the roughened and activated top surface of the structural layer (1) and the roughened and activated dielectric walls of the at least one opening (4) In the opening (Fig. 1e to Fig. 1f). The patterned resist layer (7) is removed (Fig. 1g) and the portions of the conductive layer (6) that are not covered by the electroplated copper (8) are removed by differential etching (Fig. 1h). Such methods are disclosed, for example, in US 6,278,185 B1 and US 6,212,769 B1.

The method of fabricating a thin wire circuit on a printed circuit board comprises the steps of: (i) providing a bare dielectric structure layer (1) having a contact region (2) on at least a portion of the back side and attaching to the structure a substrate of the second dielectric layer (3) on the back side of the layer (1), (ii) forming at least one opening (4) extending through the substrate to the contact region (2) in the structural layer (1), (iii) Treating the surface with a solution comprising at least one organodecane compound, (iv) treating the surface with a solution comprising an oxidizing agent, (v) depositing a conductive seed layer (6) on the top surface of the dielectric structural layer (1) (5a) And at least one of the dielectric sidewalls (5b) of the opening (4), and (vi) selectively depositing the copper layer (8) into the opening of the patterned resist layer (7) by electroplating.

The dielectric substrate (e.g., plastic article) can be subsequently metallized by activation using an electrodeless metallization process or by using a direct plating process (electrolytic plating process). The article is first cleaned, followed by coating, for example, a precious metal or a conductive polymer and then finally metallizing.

The usual activation of a dielectric substrate for subsequent metal plating is performed by activating the plastic using an activator containing a noble metal for electrodeless metallization followed by electrodeless metallization. Thereafter, a thicker metal layer can then be electrolytically coated. In the case of a direct plating process, the etched surface is typically treated sequentially with a palladium colloidal solution and an alkaline solution containing copper ions that form a complex with the complexing agent. Thereafter, the article can then be directly electrolytically metallized (EP 1 054 081 B1).

The suitable metallization sequence in step (iii) will comprise the following steps: A) using a colloidal solution or compound (specifically, a salt of Group VIIIB or Group IB metal (noble metal) of the Periodic Table of the Elements), especially palladium/tin colloid And B) electrolytic metallization using a metallization solution, in one embodiment of the invention, the substrate is a dielectric substrate and the step is iii. applying a wet chemical plating method to metallize the substrate; comprising: iiia. making the substrate and the precious metal a colloid or a solution containing a noble metal ion; iiib. contacting the substrate with the electrodeless metal plating solution; and iic. contacting the substrate with the electrolytic metal plating solution.

In one embodiment of the invention, at least one of the following other method steps is performed in a total method step iii.

Iii1. immersing the article or substrate in the pre-dip solution; iiia1 rinsing the article or substrate in the rinsing solution; iiia2. treating the article or substrate in the accelerated solution or in the reducing agent solution; iiib1 rinsing the article in the rinsing solution or Substrate; and iic1. Rinse the article or substrate in the rinse solution.

In the preferred embodiment, these other method steps are performed when an electrodeless metallization method metallization or substrate is to be used, and the electrodeless metallization method means coating the first metal on the object or substrate using an electrodeless method. Floor.

The accelerating solution is preferably used to remove components of the colloidal solution according to method step iiia., such as a protective colloid. If the colloid of the colloidal solution according to method step iia. is palladium/tin colloid, it is preferred to use an acid (for example, sulfuric acid, hydrochloric acid, citric acid or tetrafluoroboric acid) solution as an accelerating solution to remove the protective colloid (tin compound). ).

If a solution of a noble metal ion is used in method step (ii) a., a reducing agent solution such as a hydrochloric acid solution of palladium chloride or an acid solution of a silver salt is used. In this case, the reducing agent solution is also a hydrochloric acid solution and contains, for example, tin (II) chloride or it contains another reducing agent such as NaH ₂ PO ₂ or borane or boron hydride, such as an alkali metal or alkaline earth metal borane or two. Methylaminoborane.

On the other hand, it is preferred that the article or substrate is directly metallized without electrode metallization but using an electrolytic metallization process (without electrodeless metallization).

In this embodiment of the invention, the substrate is a dielectric substrate and the step is iii. applying a wet chemical plating method to metal plating the substrate; comprising: iiia. contacting the substrate with the noble metal colloid; iiib. contacting the substrate with the conversion solution, Forming a sufficient conductive layer on the surface of the substrate for direct electrolytic metallization; and iic. contacting the substrate with the electrolytic metal plating solution.

Process steps iiid., iiie. and iiif. are carried out in the stated order, but it is not necessary to carry out another step immediately after one step. For example, after the method steps, a plurality of rinsing steps can be performed. In this embodiment, method steps iid. and iie. serve as an activation step.

The conversion solution is preferably used to form a sufficient conductive layer on the surface of the article or substrate to subsequently permit direct electrolytic metallization rather than the aforementioned electrodeless metallization. If the colloid of the colloidal solution according to the method step iid. is a palladium/tin colloid, it is preferred to use an alkaline solution containing copper ions which are mismatched with the complexing agent as a conversion solution. For example, the conversion solution may contain an organic complexing agent such as tartaric acid or one of ethylenediaminetetraacetic acid and/or a salt thereof, such as a copper salt, such as copper sulfate: the conversion solution may comprise: (i) Cu(II), Ag , Au or Ni soluble metal salt or a mixture thereof, (ii) 0.05 to 5 mol/l of Group IA metal hydroxide, and (iii) a metal ion intercalating agent of the metal salt.

The treatment liquid described below is preferably aqueous.

In a preferred embodiment of the invention, the colloidal solution of the Group VIIIB or Group IB noble metal of the Periodic Table of the Elements used in the activation step is an activator solution containing a palladium/tin colloid. The colloidal solution preferably contains palladium chloride, tin (II) chloride, and hydrochloric acid or sulfuric acid. The concentration of palladium chloride is preferably from 5 to 200 mg/l, more preferably from 20 to 100 mg/l and most preferably from 30 to 60 mg/l, based on Pd ²⁺ . The concentration of tin (II) chloride is preferably from 0.5 to 20 g/l, more preferably from 1 to 10 g/l and most preferably from 2 to 6 g/l, in terms of Sn ²⁺ . The concentration of hydrochloric acid is preferably from 100 to 300 ml/l (37% by weight of HCl). Further, the palladium/tin colloidal solution preferably also contains tin (IV) ions generated by oxidation of tin (II) ions. The temperature of the colloidal solution is preferably from 20 to 50 ° C and particularly preferably from 30 to 40 ° C. The treatment time is preferably from 0.5 to 10 min, more preferably from 2 to 5 min and most preferably from 3.5 to 4.5 min.

Alternatively, the colloidal solution may also contain another metal of Group VIIIB or Group IB of the Periodic Table of Elements, such as platinum, rhodium, ruthenium, gold or silver or a mixture of such metals. It is basically possible not to stabilize the colloid with tin ions as a protective colloid, but actually to use another protective colloid, such as an organic protective colloid such as polyvinyl alcohol.

If a solution of a noble metal ion is used in place of the colloidal solution in the activation step, a solution containing an acid (especially hydrochloric acid) and a noble metal salt is preferably used. The noble metal salt may, for example, be a palladium salt, preferably palladium chloride, palladium sulfate or palladium acetate; or a silver salt such as silver acetate. As an alternative, noble metal complexes such as palladium complex salts, such as salts of palladium-amine complexes, can also be used. The noble metal compound is present in the concentration of, for example, Pd ²⁺ based on the noble metal, for example, at a concentration of from 20 mg/l to 200 mg/l. The solution of the precious metal compound can be used at 25 ° C or at a temperature of 15 ° C to 70 ° C.

Before contacting the object or the substrate with the colloidal solution, it is preferred to first contact the object or the substrate with the pre-impregnation solution, the pre-impregnation solution having the same composition as the colloidal solution but not containing the colloid and the protective colloid thereof, meaning that the solution In the case of a palladium/tin colloidal solution, only hydrochloric acid is contained (if the colloidal solution also contains hydrochloric acid). After treatment in the pre-dip solution, the article or substrate is brought into direct contact with the colloidal solution without rinsing the article or substrate.

After treating the article or substrate with the colloidal solution, the articles or substrates are typically rinsed and then brought into contact with the accelerated solution to remove the protective colloid from the surface of the article or substrate.

If the solution of the noble metal ion is used in place of the colloidal solution to treat the article or substrate, it will be subjected to a reduction treatment after being first rinsed. The reducing agent solution used in these cases usually contains hydrochloric acid and tin (II) chloride. If the solution of the noble metal compound is a hydrochloric acid solution of palladium chloride. However, an aqueous solution of NaH ₂ PO _{2 is} preferably used. Further, if the solution of the noble metal compound is a neutral or alkaline solution of the composite stabilized lead sulfate or lead chloride, an aqueous solution of DMAB (dimethylamino borane) or sodium borohydride is preferably used in the reduction treatment.

For electrodeless metallization, the article or substrate may be rinsed first after being accelerated or treated with a reducing agent solution and then electrolessly plated, for example, with nickel. A conventional nickel bath will be used to carry out this step. The nickel bath, for example, contains a number of materials including nickel sulfate, hypophosphite (such as sodium hypophosphite as a reducing agent), and organic complexing agents and pH adjusting agents (such as buffers).

As an alternative, an electrodeless copper bath, which typically contains a copper salt, such as copper sulfate or copper hypophosphite, and a reducing agent such as formaldehyde or hypophosphite (such as an alkali metal or ammonium salt) or hypophosphorous acid, may be used. And one or more complexing agents such as tartaric acid; and pH adjusting agents such as sodium hydroxide.

Any metal deposition bath can be used for subsequent electrolytic metallization, for example for depositing nickel, copper, silver, gold, tin, zinc, iron, lead or alloys thereof. This type of deposition bath is well known to those skilled in the art. A Watt nickel bath is typically used as a bright nickel bath containing nickel sulfate, nickel chloride and boric acid, and saccharin as an additive. As the bright copper bath, for example, a composition containing copper sulfate, sulfuric acid, sodium chloride and an organic sulfur compound is used, wherein sulfur is present as an additive in the low oxidation stage, for example, in the form of an organic sulfide or a disulfide.

If a direct plating method is used, that is, the first metal layer is not electrodelessly deposited, but is electrolytically deposited after processing the article or substrate with the conversion solution and optionally after the subsequent rinsing treatment, an electrolytic metallization bath, such as a nickel impact, is used. Bath, which is preferably based on Watt Nickel Formed by bath. Baths of this type, for example, contain nickel sulfate, nickel chloride and boric acid, and saccharin as an additive.

The treatment of the article or substrate in accordance with the method of the present invention is preferably carried out by conventional impregnation methods in which the article or substrate is subsequently impregnated in a solution in a correspondingly treated vessel. In this case, the article or substrate can be fixed to the hanger or filled into the tub and immersed in the solution. It is preferred to be fixed to the rack because it is possible to transmit the ultrasonic energy to the object or substrate more directionally via the rack. Alternatively, the articles or substrates may be processed in a so-called conveyor processing apparatus in which the articles or substrates are, for example, arranged on a rack and continuously transported horizontally via the apparatus and subjected to ultrasonic processing as needed.

In another embodiment of the invention, direct metallization can be achieved by using a conductive polymer on the surface of the dielectric substrate as described in, for example, US 2004/0112755 A1, US 5,447,824, and WO 89/08375 A.

EP 0 457 180 A2 discloses a method of metallizing a dielectric substrate comprising first forming a manganese dioxide layer on a substrate and then treating the surface with an acidic solution containing pyrrole and methanesulfonic acid. The solution may also contain thiophene instead of pyrrole. Due to this treatment, a conductive polymer layer was formed. Finally, the conductive layer can be electrochemically metallized. Alternatively, thiophene and aniline may be coated in place of pyrrole. This method is suitable for use as an activation step and subsequently for metallization of a non-conductive substrate in accordance with the present invention.

In this embodiment of the invention, the substrate is a dielectric substrate and the following additional method steps are performed to metallize the substrate in step iii.: iic. contacting the substrate with a water soluble polymer; iiid. treating with a permanganate solution Substrate; iiie. treating the substrate with an acidic micro-emulsion comprising at least one thiophene compound and at least one alkane sulfonic acid selected from the group consisting of methanesulfonic acid, ethanesulfonic acid and ethane disulfonic acid; or an aqueous base; and step Iv. Applying a wet chemical plating method to a metal plated substrate; comprising: ivb. contacting the substrate with an electrolytic metal plating solution.

The water-soluble polymer used in the step ic. is preferably selected from the group consisting of polyvinylamine, polyethyleneimine, polyvinylimidazole, alkylamine ethylene oxide copolymer, polyethylene glycol, poly Propylene glycol, a copolymer of ethylene glycol and polypropylene glycol, polyvinyl alcohol, polyacrylate, polypropylene decylamine, polyvinylpyrrolidone, and mixtures thereof. The concentration of the water-soluble polymer is in the range of 20 mg/l to 10 g/l.

The solution of the water-soluble polymer may further contain a water-soluble organic solvent selected from the group consisting of ethanol, propanol, ethylene glycol, diethylene glycol, glycerin, dioxin, butyrolactone, N-methylpyrrolidone , dimethylformamide, dimethylacetamide, half ether and half ester of ethylene glycol. The water-soluble organic solvent can be used in pure form or diluted with water. The concentration of the water-soluble organic solvent is in the range of 10 ml/l to 200 ml/l. During step ic., the solution of the water soluble polymer is maintained at a temperature in the range of 25 ° C to 85 ° C and the dielectric substrate is immersed in the solution for 15 s to 15 min.

Next, the dielectric substrate is treated with a permanganate solution in step id. The source of the permanganate ion can be any water soluble permanganate compound. The source of permanganate ions is preferably selected from the group consisting of sodium permanganate and potassium permanganate. The concentration of permanganate ions is in the range of from 0.1 mol/l to 1.5 mol/l. The permanganate solution can be acidic or basic. The pH of the permanganate solution is preferably in the range of 2.5 to 7. A layer of MnO ₂ is formed on the sidewalls of the blind micropores (BMV) by means of step id.

Next, in step i. the substrate is contacted with a solution preferably comprising a thiophene compound and an alkanesulfonic acid.

The thiophene compound is preferably selected from the group consisting of a 3-heterosubstituted thiophene and a 3,4-heterosubstituted thiophene. The thiophene compound is most preferably selected from the group consisting of 3,4-ethylenedioxythiophene, 3-methoxythiophene, 3-methyl-4-methoxythiophene and derivatives thereof. The concentration of the thiophene compound is from 0.001 mol/l to It is in the range of 1 mol/l, more preferably 0.005 mol/l to 0.05 mol/l.

The alkane sulfonic acid is selected from the group consisting of methanesulfonic acid, ethanesulfonic acid, methane disulfonic acid, ethane disulfonic acid, and mixtures thereof. The concentration of the alkane sulfonic acid is set by adjusting the desired pH of the solution used in step IE. The pH of the solution is preferably set in the range of 0 to 3, more preferably in the range of 1.5 to 2.1.

For the purposes of the present invention, electroplated copper is preferred as the metal. In printed circuit board applications, the total thickness of the deposited copper layer (layer or layers) is typically in the range of between 1 and 50 μm, more preferably between 4 and 30 μm.

Instance

The following experiments are intended to illustrate the benefits of the invention without limiting its scope.

In the experiments, the different decane used were enumerated and identified in Table 1. The decane was dissolved using the following organic solvent: isopropanol (boiling point 82 ° C: hereinafter referred to as IPA) and 2-isopropoxyethanol (boiling point 142 ° C, hereinafter referred to as IPPE).

Sample numbers P1 , P6 to P9 and P11 to P20 were first treated with a decane composition and then treated in an aqueous solution containing MnO ₄ ions. For sample number P2 , the method sequence was changed: first treated in an aqueous solution containing MnO ₄ ions, and then treated in a decane composition (comparative example). For sample number P3 , the treatment in the aqueous solution containing MnO ₄ ions was omitted and only the decane composition was applied (also a comparative example). Sample No. P4 was processed only in an aqueous solution containing MnO ₄ ions without any decane treatment (Comparative Example). Sample Nos. P5 and P10 were first treated with a solvent base containing no decane compound and then treated in an aqueous solution containing MnO ₄ ions (Comparative Example). The permanganate treatment step then always removes the reducing agent step of manganese (IV) oxide. The corresponding method conditions are provided in Table 1.

The composition is provided in Table 1. The treatment time is 1 min at ambient temperature.

The substrate material used was epoxy resin ABF GX92 from Ajinomoto Co.; Inc. For the experiment, a sample (7.5 x 15 cm) was cut out from the laminate and pre-cured at a temperature of 100 ° C for 30 minutes, followed by pre-curing at a temperature of 180 ° C for 30 minutes.

All solutions were freshly prepared prior to spraying. The decane content is given in % by weight and is 3 wt.% for all experiments conducted.

Decane coating: The solution was sprayed onto the substrate using an Exacta Coat spray device manufactured by Sonotek (not including Example P4 ). For Examples P5 and P10 , the solvent contained no decane and was applied in the same manner. For all studies, set the following parameters: Flow rate: 1.4 ml/min. (6 ml/min.)

Nozzle distance: 4cm

Nozzle speed: 40mm/s

Overlap: 14.2mm

Nitrogen flow: 0.8-1.0mPa

One spray cycle

Thereafter, the panels were held for 10 minutes and then baked at 105 ° C for 5 min. The plates were allowed to cool to room temperature and transferred to the permanganate etchant (not including sample P3 ).

Sample P2 was first processed via a permanganate etchant and a reducing solution and then sprayed. The second MnO ₄ etching step is not included.

Other comparative examples P21 and P22 have been carried out in a solution containing sulfuric acid and hydrogen peroxide.

Example P21 was carried out sequentially according to the aforementioned method, wherein the solution containing the oxidizing agent contained concentrated sulfuric acid and 30 wt.% hydrogen peroxide in a volume ratio of 3 to 1. The treatment was carried out at a temperature of 60 ° C for 10 seconds. Although a relatively high roughness value is obtained, subsequent metal plating produces a very poor adhesion of the metal layer to the surface substrate, thus making this treatment method unsuitable for producing an adhesive metal layer as the object of the present invention. Longer processing times and/or higher temperatures result in complete removal of the resin layer and no adhesion of the subsequently plated metal layer. Example P22 was carried out sequentially according to the aforementioned method, wherein the solution containing the oxidizing agent contained 20 mL/L of concentrated sulfuric acid and 20 mL/L of 30 wt.% of hydrogen peroxide. The treatment was carried out at a temperature of 25 ° C for 5 minutes. The treated surface exhibits a low roughness and a very poor adhesion of the subsequently plated metal layer, such that the solution produces an adhesive metal layer that is the object of the present invention.

MnO4 represents MnO ₄ ^- ion

Figure 2 shows the surface of the G2092 substrate material after permanganate treatment according to Example P20. Measurements were carried out on a Zeiss Gemini SEM with a voltage of 5 kV and a magnification of 5000 x.

The roughness Ra measured by an Olympus LEXT 3000 confocal laser microscope was 109 nm.

Figure 3 shows an SEM image of the surface of the GX92 substrate material after permanganate treatment without prior application of decane. This corresponds to a method known in the art for water-based expansion agents followed by permanganate etching. The permanganate concentration was 60 g/l, the NaOH concentration was 45 g/l, the treatment time was 20 minutes and the temperature was 80 °C. The roughness Ra measured by the confocal laser microscope mentioned above was 200 nm. This roughness may be too high for manufacturing thin wire circuits.

Thereafter, the samples were electroplated according to the method parameters provided in Table 2. Table 2 contains the procedure sequence applied to the final deposition of 0.8 μm electrodeless copper and 30 μm electrodeposited copper on the GX92 substrate material.

The peel strength measurement of the plated metal layer on the substrate was carried out by laying the sample into strips of 1 cm width and 3 cm length after the final annealing. Exfoliation strength measurements were performed using an Erichsen Wuppertal 708 strain gauge using a Chatillon LTCM-6 pulling mechanism. The adhesion values of all samples are depicted in column 5 ("Exfoliation") of Table 1.

Field emission scanning electron microscopy (FE-SEM) was performed using a LEO 1530 with a 5 kV accelerating voltage and a chirp offset detector (Xmas 80, Oxford). Images were recorded at a magnification of 5000. In the sulfuric acid / hydrogen peroxide (50ml / L conc _{H 2 SO 4, 53ml / LH} 2 O 2 aqueous solution at 40 ℃) after the etching of copper plating, measuring the dielectric surface. The sample was sputtered with helium before measurement.

For commercial methods, such as flip-chip spherical lattice arrays, adhesion values greater than 4-5 N/cm are typically required. This depends on the type of coating.

The average roughness value (Ra) was measured on an Olympus LEXT 3000 confocal laser microscope. Roughness values were collected on a surface area of 120 μm × 120 μm. The average roughness value (Ra) of all the samples is depicted in the column 6 (average roughness Ra) of Table 1.

Adequate adhesion between the plated metal layer and the substrate can only be obtained by treating the sample by the method of the present invention, i.e., first the decyl treatment of the substrate surface followed by the permanganate treatment step. All other combinations of process sequences as shown in Table 1 result in very low adhesion of the plated metal layer, which is unacceptable for commercial applications.

The lowest adhesion value was measured for sample P3 which was only coated with decane (without any permanganate treatment) and then subsequently metallated. The initial adhesion was slightly increased when the permanganate treatment was applied before the metal plating step of the substrate (sample No. P4). This increase is caused by other surface roughening due to the permanganate step. However, all samples that were not subjected to manganate processing after decane coating showed bubbles on the surface after the final copper anneal. Therefore, permanganate rinsing is preferably carried out after decane coating.

By varying the first two major steps in the process sequence, it was confirmed that only a proper order (first decane treatment followed by permanganate detergent) caused a significant increase in adhesion (up to 5.5 N/cm). All other combinations (only decane, only MnO ₄ and first MnO ₄ followed by decane treatment) gave very low adhesion of <1.0 N/cm.

The low roughness values of the treated samples make the method suitable for making circuit traces of less than 10 [mu]m width. For these structures, surface roughness values in excess of 150 nm have so far been required to achieve sufficient adhesion between the substrate and the plated metal layer. However, an average roughness value higher than 150 nm may be too high for a circuit trace having a width of less than 10 μm.

Claims (15)

A method of treating a surface of a dielectric substrate to prepare the surface for subsequent wet chemical metal plating, the method comprising the steps of: (i) treating the surface with a solution comprising at least one organodecane compound; Ii) treating the surface with a solution comprising an oxidizing agent selected from acidic or basic aqueous solutions of permanganate. The method of claim 1, wherein the concentration of permanganate is in the range of 20 to 100 g/l. The method of claim 1, wherein the organodecane compound is selected from the group consisting of A _(4-x) SiB _x wherein each A is independently a hydrolyzable group, x is from 1 to 3, and each B is Independently selected from the group consisting of C ₁ -C ₂₀ alkyl, aryl, aminoaryl and a functional group represented by the formula: C _n H _2n X, wherein n is from 0 to 15, preferably 0. Up to 10, even more preferably from 1 to 8, most preferably 1, 2, 3, 4, and X is selected from the group consisting of amine groups, guanamine groups, hydroxyl groups, alkoxy groups, halo groups, sulfhydryl groups, Carboxyl, carboxy ester, formamide, thioformamide, mercapto, vinyl, allyl, styryl, epoxy, epoxycyclohexyl, glycidoxy, isocyanate, thiocyano, sulfur Isocyanato, ureido, thioureido, sulfhydryl, thiomethyl, acryloxy, methacryloxy; or X is a residue of a carboxylic ester; or X is Si(OR) ₃ , and wherein R is a C ₁ -C ₅ alkyl group. The method of claim 3, wherein the hydrolyzable group A is selected from the group consisting of -OH, -OR ¹ , and wherein R ¹ is C ₁ -C ₅ alkyl, -(CH ₂ ) _y OR ² , and Wherein y is 1, 2 or 3 and R ² is H or C ₁ -C ₅ alkyl, -OCOR ³ , and wherein R ³ is H or C ₁ -C ₅ alkyl. The method of claim 4, wherein R ¹ , R ² and R ³ are independently selected from the group consisting of methyl, ethyl, propyl and isopropyl. The method of any one of claims 1 to 5, wherein the organodecane compound is selected from the group consisting of vinyl decane, aminoalkyl decane, amino ureido alkyl decane, methacryloxy group Decane and epoxy alkyl decane. The method of any one of claims 1 to 5, wherein the organodecane is applied at a concentration between 0.5 wt.% and 20 wt.%. The method of any one of claims 1 to 5, wherein the organodecane is dissolved in a polar organic solvent having a boiling point in the range of from 60 to 250 °C. The method of any one of claims 1 to 5, wherein the organodecane is dissolved in a polar organic solvent selected from the group consisting of diethylene glycol, 2-isopropoxyethanol (IPPE), and di(propylene glycol) Ether acetate (DPGMEA) and 2-ethyl-1-hexanol. The method of any one of claims 1 to 5, wherein the oxidizing agent according to step (ii) is an alkaline aqueous solution of permanganate ions. The method of any one of claims 1 to 5, comprising (i) treating the surface with a solution comprising at least one organodecane compound at a temperature between 15 and 50 ° C for a period of between 10 s and 10 min, ( Ii) treating the surface with a solution comprising an oxidizing agent selected from an alkaline aqueous solution of permanganate ions at a concentration of 20-100 g/l at a temperature between 20 and 95 ° C for a period of between 1 and 30 min, A roughened surface having an average surface roughness Ra of less than 150 nm was obtained. The method of any one of claims 1 to 5, further comprising: (iii) metallizing the substrate by wet chemical plating after step (ii). The method of claim 12, wherein the metallization is copper metallization. The method of claim 12, wherein (iii) metallizing the substrate by wet chemical plating after step (ii) comprises the step of: causing the surface to conduct (iii a) contacting the substrate with an activator solution, the activation The agent solution contains a colloidal or ion-catalyzed metal such as a noble metal, preferably a palladium, and, as the case may be, when the activator contains an ion-catalyzed metal, (iii b) The substrate is contacted with a reducing agent, wherein the metal ion of the ion activator is reduced to an elemental metal, or, when the activator contains a colloidal catalytic metal, (iii c) contacting the substrate with an accelerator, wherein the composition of the colloid ( For example, a protective colloid) is removed from the catalytic metal. The method of any one of claims 1 to 5, wherein the dielectric substrate is a substrate comprising a bare dielectric structure layer (1) having a contact region (2) on at least a portion of the back surface and attached thereto a second dielectric layer (3) on the back side of the structural layer (1) having at least one opening (4) extending through the substrate to the contact area (2) in the structural layer (1), (i) Treating the surface with a solution comprising at least one organodecane compound as defined in any of the above claims, (ii) treating the surface with a solution comprising an oxidizing agent as defined in any of the above claims, (iii) depositing a conductive seed layer (6) on the top surface (5a) of the dielectric structure layer (1) and the dielectric sidewall (5b) of the at least one opening (4), and (iv) by electroplating The copper layer (8) is selectively deposited into the openings of the patterned resist layer (7).