CA2033934C - Method for treating polyetherimide substrates and articles obtained therefrom - Google Patents

Abstract

The method is provided for treating the surface of a polyetherimide substrate to improve its adhesion characteristics for electrolessly deposited metal, such as copper. There is employed a series of surface treatments including the initial immersion of the polyetherimide substrate in sulfuric acid, contact with aqueous base, such as potassium hydroxide, followed by oxidation with an alkali metal permanganate such as potassium permanganate, and surface treatment with a reducing agent, such as a hydroxylamine salt. Polyetherimide metal composites are also provided.

Description

RD-18,355 METHOD FOR TREATING POLYETHERIMIDE
SUBSTRATES AND ARTICLES OBTAINED THEREFROM
Cross Reference To Related ADDlication Reference is made to co-pending Canadian application Serial No,. 598,048, filed April 27, 1989, now Canadian Patent 1,331,,541 for Method For Treating A
Polyimide Surface To 7Cmprove The Adhesion Of Metal s Deposited Thereon And Articles Produced Thereby and copending Canadian application Serial No. 600,122, filed May 18, 1989, now Canadian Patent 1,331,542, for Improved Method For Preparing 1?olymer Surfaces For Subsequent Plating Thereon, And :Cmproved Metal Plated Plastic Articles io Made Therefrom, which are assigned to the same assignee as the present invention..
Background Of The Invention The present invention relates to a method for treating polyetherimide surfaces to improve their adhesion 15 characteristics to metal, such as copper, after the metal has been electrolessly deposited onto such molded or extruded polyetherimide surfaces.
Prior to this present invention, as shown by Canadian Patent 1,331,541, improved adhesion was achieved 20 on a polyetherimide surface by treating the polyetherimide surface with an adhesion promoter such as thiourea.
However, it has been found that thiourea can discolor copper inserts in a molded polyetherimide circuit board resulting in poor bonding between the copper insert and 2s the electrolessly plated copper. In Canadian patent 1,331,542, improved adhesion of the polyetherimide surface is achieved by initially modifying the surface of the polyetherimide with a mild etchant, such as sulfuric acid, contacting the modified surface with a basic solution RD-18,355 followed by contacting the treated surface with a cationic surfactant which effects the removal of a residual film formed on the surface after the sulfuric acid step. Removal of the residual film or white residue i.s essential to optimize the adhesion of any subsequently applied electrolessly deposited metal onto the plastic substrate.
Although effective results have been achieved by the employment of a cationic surfactant, it has been found that the concentration of the white residue resulting from sulfuric acid immersion followed by a water rinse, can actually increase in the solubilizing bath, since the white residue is merely solubilized not chemically altered. As a result, treatment of the polyetherimide surface with the aqueous cationic surfactant can eventually result in reduced adhesion of the electrolessly deposited metal on the polyetherimide surface.
It would be desirable to provide a procedure to treat the surface of an extruded or molded polyetherimide to allow for the producticn of metal-plastic composites. More particularly, it would be desirable to provide a method for making metal-plastic composites by electroless metal deposition to achieve superior adhesion between the electrolessly deposited metal and the plastic substrate. It also would be desirable to avoid discoloration between copper inserts in molded or extruded polyetherimide plastic substrates resulting from the employment of adhesion promoters, such as thiourea.
The present invention is based on the discovery that the non-adherent white film formed on the surface of a molded or extruded polyetherimide resulting from sulfuric acid immersion can be chemically modified by rinsing the RD-18,355 treated polyetherimide substrate with water and an aqueous basic solution, such as alkali metal hydroxide solution, followed by immersing the resulting treated plastic substrate into an aqueous alkali metal permanganate solution. The resulting treated substrate, after it has been subjected to a water rinse is found to be completely free of the white residue, normally formed from the sulfuric acid treatment.
However, a brown manganese residue remains on the plastic surface. The brown manganese residue is readily removed by immersing the polyetherimide substrate into an aqueous solution of a reducing agent, such as hydroxylamine hydrochloride. Surprisingly, the resulting treated polyetherimide substrate provides excellent adhesion between electrolessly deposited metal, such as copper, and the polyetherimide substrate without the use of an adhesion promoter, such as thiourea.
Statement of the Inven -~"~n~
There is provided by the present invention, a method for modifying the surface of a polyetherimide substrate to improve its adhesion characteristics toward electrolessly deposited metal, which comprises, (A) treating the surface of the polyetherimide substrate with a degreasing agent, (B) modifying the degreased polyetherimide surface with concentrated sulfuric acid, (C) treating the modified polyetherimide surface with an aqueous base having a pH of 14 or greater, (D) oxidizing the resulting polyetherimide surface with an alkali metal permanganate resulting in the production of a manganese oxide residue, and (E) effecting the removal of the manganese oxide residue from the polyetherimide surface by treating the polyetherimide surface with a reducing agent.

RD-18,355 In a further aspect of the present invention there is provided a molded or extruded polyetherimide substrate having at least a portion of its surface initially degreased, modified in sulfuric acid, treated s with an aqueous base having a pH of 14 or greater, oxidized with an aqueous Mn04- source material, and thereafter treated with a reducing agent.
In an additional aspect of the present invention, there is provided a me~tallized polyetherimide substrate or to polyetherim:ide printed circuit board, comprising a polyetherimide substrate and electrolessly deposited metal applied thereon in a patterned or unpatterned manner, where the polyetherimide substrate has been initially degreased, modified in sulfuric acid, treated with an aqueous base having 15 a pH of 14 or greater, oxidized with an aqueous Mn04- source material, and thereafter treated with a reducing agent.
As used the~reinafter, the terms "degreased" means a polyetherimide subsitrate having its surface free of oil, molding compounds, finger prints or extraneous material.
zo As used thex-einafter the expression "modified with sulfuric acid" means treating the surface of the polyetherimide, by immersion, spraying, painting, or other forms of surface treatment with an aqueous solution of hydrogen sulfate having a concentration of from 80~ to 99~, at a temperature of 0°C
z5 to 85°C for from 10 seconds to 30 minutes.
Among the polyetherimides which can be employed in the practice of t;he present invention are polymers shown by Heath et al U.S. Patent 3,847,867 assigned to the same assignee as the present invention. Additional 3o polyetherimides which can be used in the practice of the present invention are shown by Takekoshi et al U.S.
Patent 3,803,085 assigned to the same assignee as RD-18,355 the present invention,. The preferred polyetherimide used in the practice of the: method of the present invention can be made by condensing 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl] propane dianhydride with metaphenylene diamine in s an extruder reactor under neat conditions. The resulting polyetherimide can be readily injection molded to a variety of complex shapes inc:Luding substrates for circuit boards or extruded and cut to size in the form of film having a thickness of 0.5 to 25 mil. The polyetherimides may to contain various amouni~s of fillers or reinforcing agents such as talc, mica, aluminum silicate, zinc oxide, titanium dioxide, carbon black" glass fibers, glass spheres, carbon fibers and mixtures thereof. Polyetherimides also can be melt blended with sil:LCOne-polyimide polymers. In addition 15 to the aforementioned fillers, the polyetherimides also can contain additional additives such as pigments, ultraviolet radiation absorbing agents, impact modifiers, plasticizers, microwave absorbing agents, stabilizers, processing aids, and anti static agents.
2o The polyetherimide substrate of the present invention can be in tlZe form of a printed circuit board having flat: or curved surfaces, which can include cavities, copper inserts such ass pins or heat sinks, raised and recessed regions and through-holes. In addition, the 2s polyetherimide can be in the form of a multi-level circuit board. Further, the polyetherimide can be shaped in specific designs such as coffee pots, thin films to provide flexible circuitry, o:r thin films adaptable to being incorporated as part of other molded shapes.
3o The polyetherimide can be initially degreased with a degreasing agent such as detergent, or a suitable organic solvent, such as a ha7Lo hydrocarbon for example a Freon RD-18,355 solvent, such as 1,1,2-trichlorotrifluoroethane. After the initial degreasing step, the polyetherimide can be modified with concentrated sulfuric acid as previously defined.
A residual film of varying thicknesses can be formed on the polyetherimide surface during the sulfuric acid treatment step. The film may remain on the surface of the polyetherimide even after rinsing. The film can be treated with an aqueous base of pH greater than 14, such as an aqueous basic solution of O.1M to about lOM of an alkali metal hydroxide, such as sodium hydroxide, potassium hydroxide, In addition to alkali metal hydroxide, there is included tetramethylammonium hydroxide. The aqueous base hydroxide treatment preferably is effected at room temperature. A water rinse can be used if desired.
The surface of the resulting polyetherimide can then be immersed into an aqueous solution of an alkali metal hydroxide and alkali metal permanganate at a temperature of 25°C to 85°C for a period of 2 to 20 minutes. The use of an alkali metal hydroxide, as previously defined, with the alkali metal permanganate is optional. The permanganate oxidizing solution can contain from 1 to 75 grams of the alkali metal permanganate, per liter of solution for effective results the substrate can then be removed from the bath for a water rinse. The rinse can be effected by immersing the treated substrate in water, or by spraying or brushing. The alkali metal permanganate preferably includes potassium or sodium permanganate.
Following the water rinse, a brown manganese containing film can be present on the surface of the rinsed polyetherimide substrate. It has been found effective at this time to treat the polyetherimide with a reducing agent such as an aqueous solution of hydroxylamine hydrochloride by immersing the polyetherimide substrate into the reducing bath. Additional reducing agents which can be used are for _ ., _ RD-18,355 example solution of 1 to 10~ of stannous chloride in S~ HC1, an aqueous solution of 1 to 30~ by weight of hydrogen peroxide, Shipley Circuposit MLB Neutralizer 216, a 1 to 300 solution of sodium bisulfite, etc. The resulting polyetherimide substrate can then be rinsed and allowed to dry to form a polyetherimide substrate having a chemically altered surface rendering it hydrophilic. In addition, it has been found to have a slightly higher =C-O- content possibly indicating increased formation of carboxylic acid, ether, and/or alcohol groups. Its modified surface is capable of being activated even after an extended period of time with a tin-palladium colloid in a standard manner and metallized with a electrolessly deposited metal such as copper.
Superior adhesion between the deposited metal and the 1S polyetherimide surface can be achieved.
It is often useful to begin the activation of the substrate by treatment with an additive which aids in absorption of the plating catalyst. Such additives are well-known in the art. Exemplary aids to catalyst absorption include Shipley 1175A, a product of the Shipley Company, and Metex 9420, a product of the MacDermid Corporation.
Immersion in about 0.1$ to about 5~ by volume of either of these agents in water for about 1 minute to about 10 minutes at a temperature of from about 40°C to about 80~C is usually sufficient. Although such a treatment is not deemed critical to the present invention, its use often enhances the uniform deposition of electrolessly-applied metals onto the substrate.
Activation of the polyetherimide substrate for plating purposes can be achieved by well known methods of the art. For example, the substrate may be contacted with an acid solution of a precious metal, such as palladium chloride in hydrochloric acid, for a period of time sufficient to cause catalytic activation of the substrate surface.

RD-18,355 _ g _ One illustrative activation technique involves immersing the substrate in a solution of Shipley Cataprep°
404, a product of the Shipley Company. This solution provides a protecting agent for the plating catalyst s subsequently applied, and comprises sodium bisulfate and various surfactants. The substrate may then be immersed in a solution of Shipley Cataposit ° 44, which contains the Cataprep~ 404 ingredients, tin, and palladium, which is the electroless plating c<~talyst. After a water rinse, the to substrates may then be. immersed in a solution of Shipley Cuposit° Accelerator :L9, a fluoroboric acid-containing formulation used to separate tin from the plating catalyst.
Activation and plating processes suitable for the present invention are also described in U.S.
15 Patents 3,011,920 and 3,841,881, issued to Shipley and Feldstein et al, respectively. A water rinse generally follows t:he activation step.
After surface activation and rinsing, electroless plating can be undertaken. Illustrative 2o metals used to form the metallization layer include copper, palladium, :nickel, cobalt, and gold. Copper is usually the metal of choice when forming a printed circuit. Electroless baths are well-known in the art and are generally described in the Kirk-Othmer 2s Encyclopedia of Chemical Technology, 3rd Edition, Volume 8. The selection of a particular bath or electroless plating process is not critical to the present invention. The contents of the bath and the particular plating parameters, e.g., temperature, pH, 3o and immersion time, will of course depend on the particular polyetherimide serving as the substrate, and also upon the particular metal being deposited RD-18,355 thereon. Suitable copper plating baths include the Shipley Cuposit~ 250 system and the Enthone~ 406 system. Immersion times, bath temperatures, and other operating parameters can be determined and controlled according to manufacturers' suggestions. Those having ordinary skill in the plating arts will be able to determine the most appropriate plating procedure for a particular situation.
The polyetherimide surface can be subjected to a heat treatment after electroless deposition of the metal.
Oven heating of the entire article, i.e., substrate with metal thereon, is sufficient, although any heating method is suitable. Typically, this heat treatment is carried out at a temperature ranging from about 50~C to about 170pC for about 5 minutes to about 120 minutes, with higher temperatures within the above range generally compensating for shorter duration, and vice versa. Although the mechanism is not understood, the heat treatment appears to reduce the time required to attain optimal adhesion.
If another layer of metal is to be applied on the surface, e.g., by electroplating, the above-described heat treatment can in some instances be omitted if a heat treatment is employed after the plating of more of the metal, as described below. However, preferred embodiments include the heat treatment prior to deposition of more of the metal.
Most preferred embodiments include a heat treatment prior to the deposition of more of the metal (i.e., after the electroless deposition), along with another heat treatment after the final layer of metal has been applied, as described below.
Electroplating is the preferred application method for the second metal layer. The substrate is usually cleaned prior to immersion in the electroplating bath. The cleaning can be performed by rinsing the substrate with a dilute RD-18,355 solution of a strong acid, such as 10~ by weight sulfuric acid in water.
Electroplating baths are well-known in the art and are described, for exai~le, in U.S. Patent 4,555,315, although the particular electroplating bath used is not critical to the present invention. The choice of course depends in part on the particular metal being deposited. Suitable metals include those described for the electroless deposition.
Furthermore, those skilled in the art appreciate that the to particular bath contents will depend upon some of the factors considered for the electroless deposition of metal described above. Typically, the electroplating bath for copper is operated at a temperature ranging from about 16°C to about 38°C, with a cathode current density in the range of about 1 is amps/sq.ft.(ASF) to about 80 ASF. A description of baths for plating copper or various other metals is given in the Kirk-Othmer reference described above, in Vol. 8, beginning on page 826. Baths used to apply a layer typically include an aqueous acidic copper electrolyte such as those of the acidic 2o copper sulfate or acidic copper fluoroborate type; halide ions, such as chloride and/or bromide ions; and various other components well-known in the art. The thickness of this second metal layer will of course depend upon the desired end use of the metal-coated substrate.
z5 The metal applied onto the polyetherimide substrate may be in tlhe form of a pattern. Exemplary patterning methods are also described in U.S. Patent 3,562,005, issued to lDeAngelo et al.
The electrolytic layer applied on top of the 3o electrolessly-applied layer can be substantially free of chemical additives normally present in an electrolytic layer, such as leveling agents and brighteners. The electrolytic plating bath used for this deposition is thus sometimes RD-18,355 referred to herein as a "nonadditive" bath and more particularly discussed in Canadian patent 1,331,542. It has been found that the omission of these additives result in a high level of adhesion between the polyetherimide s surface and the electrolessly-applied metal layer.
A heat treai:ment may be utilized at this stage.
A typical heating reg:Lmen would be about 1 hour to about 24 hours at about 50°C to about 150°C.
The metallization layer applied from a solution io without chemical addii~ives usually has a nodular, somewhat rough appearance. While such a surface may be suitable for some end uses, a smooi~h, level surface is desired for others. A smooth sur:Eace can be achieved by the deposition of a second electrolytic layer, which contains chemical 15 additives, on top of ithe first electrolytic layer. The bath used to apply this layer is sometimes referred to herein as an "additivia" bath.
An etching agent is often used prior to the deposition of this second electrolytic layer. Examples of zo etching agents include=_ ammonium or sodium persulfate, and a mixture of hydrogen peroxide and sulfuric acid. A water rinse usually follows the etching step. The surface is then rinsed again witlh a dilute solution of a strong acid in order to remove residual oxides of the plated metal. An 2s example of this last-mentioned step would be an immersion of the substrate in a l~ of weight to about 10~ by weight aqueous sulfuric acid solution for about 10 seconds to about 120 seconds. The substrate is now ready for further plating.
The electro:Lytic bath for the second electrolytic 30 layer can be one of the conventional baths known in the art.
These baths contain ei°fective amounts of brighteners and leveling agents, as well as other additives, all of which are known in the art and are described, for example, in RD-18,355 DecoratinqPlast,'-cs, edited by James M. Margolis, Hanser Publishers, 1986; by J.D. Reid and A.P. David in P~~-j~p and SLrface F.~,ni~h~,ncs, January 1987, pp. 66-70; in Modern ~ro~latincr, edited by Frederick A. Lowenheim, Third Edition, John Wiley and Sons, Inc.; and in the United Kingdom Patent application of D. Morrissey et al, GB2123036A.
Examples of other chemical additives are stress relievers, depolarizers, plating suppressors, and wetting agents, as well as agents used for hardening, grain refining, reducing trees, and limiting current density. Thus, the term "chemical additives" as used herein is meant to include any of the above-mentioned agents.
After deposition of the second electrolytic layer, the substrate is rinsed again with water and then heat-treated to further enhance adhesion of the metal layers to the substrate. A typical heat treatment for this step can involve temperatures ranging from about 50°C to about 150°C
for a time period ranging from about 1 hour to about 24 hours. This heat treatment obviates the heat treatment used after the first electrolytic deposition.
The result of the second electrolytic deposition can be a smooth, bright metal layers characterized by a high level of adhesion of the polyetherimide substrate.
In preferred embodiments, an article prepared by the method of this invention usually has an electroless metallization layer which is about 0.25 micron to about 2 microns thick; a first electrolytically-applied layer of at least about 5 microns; and a second electrolytically-applied layer having a thickness of at least about 5 microns.
Articles of various embodiments of this invention are suitable as printed circuit boards which would contain metallic layers as described herein in a printed circuit pattern or "trace".

RD-18,355 Adhesion of the metal to the substrate was evaluated by measuring the force necessary to peel strips of the metal from the substrate surface. In the test, the metal surface of each plated sample is etched into 1/8 inch strips.
An end of each strip is clipped to an Ametek digital force measuring gauge which is connected to a computer processor.
Force values required to lift the metal strips from the substrate are converted by the computer into pounds per inch peel values. Multiple peel values for each strip are obtained and then averaged.
In order that those skilled in the art will be better able to practice the present invention, the following examples are given by way of illustration and not by way of limitation.
A I inch by 6 inch by 0.062 inch molded polyetherimide slab having a specific gravity of 1.27 was treated as follows:
2 minutes in 1,1,2-trichloratrifluoroethane Dry 0.5 minute in concentrated sulfuric acid, 23°C
2 minute water rinse 5,minutes in KOH(5M), 23°C
5 minutes in KMnOq(15/g/L),KOH(1.2N), 75°C
2 minute water rinse 5 minutes in NHZOH~HC1(2.5~), 23°C
2 minute water rinse The polyetherimide slab was examined by X-ray photoelectron spectroscopy to a depth of about 50 ~ as shown by the following table:

_ 14 _ RD-18,355 Table I
X-Ray Photoelectron Spectroscopy Data Treatment C N O S Mn Theoretical untreated 82.4 4.4 13.3 -- --After H2SOq 79.5 4.0 14.3 1.4 --After KOH 78.6 3.8 15.0 0.8 --After KMn04 45.2 0.9 40.1 -- 8.8 After NH20HHC1 80.8 3.5 15.2 -- --The polyetherimide slab was then immersed for 5 minutes in Shipley 1175A at a temperature of 65°C. There was utilized about 2 1/2~ by volume of the agent in the conditioning mixture. The substrate was then rinsed for 2 minutes in water, then immersed for 1 minute in a bath containing 270 grams of Shipley Cataprep~ 404, per liter of water. The substrate was then immersed in a bath for 3 minutes at 44°C containing 1.5 volumes of Shipley Cataposit~
44, per 100 volumes of Shipley CatapositC~? 404 solution. The substrate was then rinsed for 2 minutes.
The treated substrate was then immersed for 3 minutes in a bath of 20 volumes of Shipley Cuposit~
Accelerator 19, per 100 volumes of water. The substrate was then rinsed for 2 minutes. The substrate was then immersed in a bath at 48°C for 30 minutes of Shipley Cuposit~ 250 which consists of distilled or deionized water - 81.2 by volume, CUPOSIT 250i~ - 12.0 by volume, CUPOSZT 250A - 3.0~
by volume, CUPOSIT Z - 2.3~ by volume, and CUPOSIT Y - 1.5$
by volua:-a . There was obtained a composite of the polyetherimide substrate and electrolessly deposited copper having an average thickness of about 0.05 mils.
The composite was then removed from the electroless plating bath and rinsed in water for 2 minutes and then heated in water 95°C for 2 hours. The same procedure was RD-18,355 repeated to produce additional composites of various polyetherimide and ele:ctrolessly deposited copper. The polyetherimide slabs were reinforced with various filler.
The different composites were then separately immersed in s an electroplating bath for 1 hour at 25°C. The electroplating bath consisted of an aqueous solution of 125 g/liter of CuS04~5Hz0, 60 g/liter of HZS04 and 50 ppm of chloride in the form of HCl. It was run at a current density of 36A/sq.ft. The resulting composites had about l0 1.67 mil of electrolyt:ically deposited copper. The composites were then heat treated for 16 hours at 95°C.
Adhesion of the copper metal to the substrate was evaluated by measuring the force necessary to peel 1/8th inch strips of metal from the sub~atrate surface. The 1/8th inch strips 15 were prepared by a paitterning technique using nitric acid as an etchant. The end of each metal strip was clipped to an AMETEK digital force measuring gauge connected to a computer processor. 'The force values to lift the metal strips from the polyetherimide substrate were converted by 2o the computer to pounds per inch peel values. Multiple peel values were obtained :for each strip. In Table II below, there is shown average adhesion values for the respective polyetherimides blended with various fillers.

RD-18,355 Table II
Adhesion Data Average Filler (Wt.~) Adhesion (lblin?
8.1 20~ glass 9.7 30~ glass g 30~ glassll5~ Ti02 7.7 30~ glassll.5~ carbon black7,2 20~ Mica 6,8 15~ Silicone-polyimide 9.6 Example 2 The procedure of Example 1 was repeated using a polyetherimide reinforced with 30~ by weight of glass fiber.
Prior to the electroless deposition of copper to form the polyetherimide-copper composite, a variety of reducing agents were used to effect the removal of the brown manganese containing film after the potassium permanganate oxidation step. The following results were obtained with the polyetherimide-copper composite using the same adhesion measuring procedure as Example 1:

RD-18,355 Table III
Adhesion Data For Various Manganese Removers Compound Average Adhesion (lb/in) None 8.0*

5~ SnCl2/5~HC1 9.8 5$ H202 12.8 Shipley Circuposit 12.2 MLB Neutralizer 218**

5~ NHZOHHC1 12.6 Shipley Circuposit MhB~ 11.4 Neutralizer 216***

5~ NaHS03 10.6 Shipley Neutraclean 68**** 11.3 * Manganese not removed until immersion in the palladium/tin colloid ** Peroxide based *** Hydroxlamine based **** Sodium bisulfate based The above results show that a variety of reducing agents can be used in addition to the hydroxlamine hydrochloride to achieve optimum adhesion results.
Polyetherimide composites made in accordance with example 2, using the NH20H~HC1 manganese remover were initially rinsed with a 10$ by weight solution of sulfuric ~~t~ ~~~- ~t RD-18,355 acid in water. The polyetherimide composites were then electroplated.
The composites were initially immersed in an electrolytic copper bath as described in example l, (Non Additives) at 25°C far a period of up to 60 minutes (Additives). A current density of 36 ASF was used.
Composites were also electroplated following the same procedure in an electrolytic copper bath containing Lea Ronal Copper Gleam PCM Plus, a brightener, for a total electroplating time of 60 minutes.. The following adhesion results were obtained following the same adhesion test procedure of example 1:
TABLE IV
Effect of Electrolytic Copper Overlayer on Polyetherimide/Electroless Copper Adhesion Thickness of Thickness of Average Adhesion Non Additive Additive (lb/in) Electrolyte Copper* Electrolytic Copper**
Immersion (mil) Immersion (mil) (mil) Time (hr) Time (hr) 0.0 1 1.67 6.6 1/12 0.14 11/12 1.53 12,4 1/6 0.28 5/6 1.39 12.5 1/4 0.42 3/4 1.25 11.0 1/2 0.83 1/2 0.83 11.2 1 1.67 0 0.0 11.1 *115 g/LCuSOq~5H20,60g/LHZSOq,50 ppm chloride.
**Lea Ronal Copper Gleam PCM Plus.

_ 19 _ RD-18,355 Although the above examples are directed to only a few of the very many variables which can be used in the practice of the method of the present invention, it should be understood that the present invention is directed to the use of a much broader variety of polyetherimides, fillers for such polyetherimides, reducing agents and conditions used in the formation of the treated polyetherimide substrates and composites made therefrom as set forth in the description preceding these examples.

Claims (11)

1. A method for modifying the surface of a polyethermide substrate to improve its adhesion characteristics for electrolessly deposited metal without the use of an adhesion promoter which consists essentially of:
(A) treating the polyetherimide surface with a degreasing agent, (B) modifying the degreased polyetherimide surface with concentrated sulfuric acid having a concentration from 80% to 99%, (C) treating the modified polyetherimide surface with an aqueous base to provide a pH of 14 or above, (D) oxidizing the resulting polyetherimide surface of (C) with alkali metal permanganate resulting in the production of a manganese oxide residue, and (E) effecting the removal of the manganese oxide residue from the polyetherimide surface by treating the polyetherimide surface with a reducing agent.

2. A method in accordance with claim 1, where the polyetherimide is reinforced with glass fiber.

3. A method in accordance with claim 1, where the reducing agent is hydroxylamine hydrochloride.

4. A method in accordance with claim 1, where the alkali metal permanganate is potassium permanganate.

5. A method in accordance with claim 1, where the degreasing agent is 1,1-2-trichlorotrifluoroethane.

6. Metallized polyetherimide composite comprising a polyetherimide substrate having electrolessly deposited metal patterned thereon, where the polyetherimide substrate has been treated in accordance with claim 1.

7. A polyetherimide substrate having a thickness of 0.5 to 25 mils treated in accordance with the method of claim 1.

8. A composite in accordance with claim 6 having metal electrolytically deposited on the surface of the electrolessly deposited metal.

9. A composite in accordance with claim 6 having electrolytically deposited copper on electrolessly deposited copper.

10. A circuit board in accordance with claim 6.

11. A coffee pot in accordance with claim 6 have electrolessly deposited metal on its base.