Electronic articles containing a fluorinated poly(arylene ether) dielectric

An electronic article such as a multichip module or an integrated circuit chip has a multilayer interconnect with multiple layers of conductive material and a dielectric material made of a fluorinated poly(arylene ether) having a repeat unit such as ##STR1##

BACKGROUND OF THE INVENTION 
This invention relates to electronic articles having a fluorinated 
poly(arylene ether) dielectric. 
Polymer films and coatings are often used in the electronic industry as 
insulating materials and passivation layers, especially in integrated 
circuit devices such as multichip modules. Polymers having a low 
dielectric constant .epsilon. are preferred, because components insulated 
with them can be designed with higher circuit densities and can operate at 
higher speeds and with less signal broadening. The effect of .epsilon. on 
the performance of multilayer integrated circuit articles is discussed in 
"Microelectronics Packaging Handbook," Tummala et al. (eds.), pp. 687-692 
(van Nostrand Reinhold); Watari et al., U.S. Pat. No. 4,744,007 (1988); 
and Budde et al., U.S. Pat. No. 4,732,843 (1988). 
Polyimide is an insulator of choice for many electronic applications, 
because of its superior mechanical and thermal properties and its 
fabricability into thin films and coatings. However, polyimide has a 
relatively high .epsilon., a limitation accentuated by polyimide's 
tendency to absorb water (up to 3-4%) in humid environments. Water 
absorption causes .epsilon. to rise, compromising performance. One 
commercially available polyimide has an .epsilon. of about 3.2 at 0% 
relative humidity (% RH), which rises to about 3.8 at 60 % RH. As noted by 
Denton et al. in J. Electronic Mater. 14(2), 119(1985), polyimide moisture 
absorption can also adversely affect performance through increased 
insulator conductivity, loss of adhesion, or corrosion. Further, some 
polyimides are susceptible to hydrolysis and/or attack by solvents (often 
manifested by crazing or cracking upon exposure to a solvent). 
It has been proposed, in Mercer, U.S. Pat. No. 4,835,197 (1989), to improve 
the solvent resistance of polyimide by curing with an acetylene, 
maleimide, or vinyl terminated curing agent. However, a polyimide so cured 
would still have the relatively high dielectric constant of polyimides and 
their tendency to absorb moisture. 
Mercer, in copending commonly assigned application Ser. No. 07/447,771, 
filed Dec. 8, 1989, proposes using fluorinated polymers having a 
binaphthyl moiety as dielectric materials. 
Polyquinoxalines, polyquinozalones, polybenzoxazoles, and copolymers 
thereof with polyimides have also been proposed as polymers for 
microelectronic applications by Labadie et al., in SAMPE J. vol. 25, pp. 
18-22 (Nov./Dec. 1989). 
Kellman et al., ACS Symp. Ser. 326, Phase Transfer Catalysis, p. 128 (1987) 
discloses the preparation of polyethers from diphenols and 
hexafluorobenzene and decafluorobiphenyl, although no particular utility 
is disclosed for the polymers so prepared. Similar disclosures are made in 
Kellman et al., Polym. Prepr. 22(2), 383 (1981) and Gerbi et al., J. 
Polym. Sci. Polym. Letters Ed. 23, 551 (1985). 
This invention provides electronic articles having a fluorinated 
poly(arylene ether) dielectric material. This dielectric material has a 
low dielectric constant which is little affected by increases in the 
ambient humidity, can be made solvent resistant, and exhibits excellent 
adhesion to itself and other adherends. 
SUMMARY OF THE INVENTION 
This invention provides an electronic article having a dielectric material 
comprising a fluorinated poly(arylene ether) comprising a repeat unit of 
the structure 
##STR2## 
wherein each --A is independently --F, --Cl, --Br, --CF.sub.3, --CH.sub.3, 
--CH.sub.2 CH.dbd.CH.sub.2, or --C.sub.6 H.sub.5 ; p is 0, 1, or 2; --Z-- 
is a direct bond, --C(CH.sub.3).sub.2 --, --C(CF.sub.3).sub.2 --, --O--, 
--S--, --SO.sub.2 --, --CO--, --P(C.sub.6 H.sub.5)--, C(CH.sub.3)(C.sub.6 
H.sub.5), --C(C.sub.6 H.sub.5).sub.2 --, --(CF.sub.2).sub.1-6 --, or 
##STR3## 
wherein --Y-- is --O-- or a direct bond; and m is 0, 1, or 2; each --X is 
independently --H, --Cl, --Br, --CF.sub.3, --CH.sub.3, --CH.sub.2 
CH.dbd.CH.sub.2, or --C.sub.6 H.sub.5 ; q is 0, 1, or 2; and n is 1 or 2. 
Preferably, --W-- is 
##STR4## 
corresponding to a fluorinated poly(arylene ether) having the repeat unit 
##STR5## 
wherein --A, p, --Z--, m, --X, q, and n are as previously defined. 
Further, the group --Z-- is preferably para-bonded to each ether oxygen in 
the benzene rings. 
In one embodiment, the electronic article is a multichip module comprising 
a substrate, a plurality of semiconductor chips carried on the substrate, 
and a multilayer interconnect connecting the semiconductor chips; the 
multilayer interconnect comprising plural layers of conductive material 
and plural layers of a dielectric material made of a fluorinated 
poly(arylene ether) as aforesaid. 
In another embodiment, the electronic article is an integrated circuit chip 
having thereon a multilayer interconnect comprising plural layers of 
conductive material and plural layers of a dielectric material made of a 
fluorinated poly(arylene ether) as aforesaid. 
In yet another embodiment, the electronic article is an integrated circuit 
chip having thereon a protective coating comprising a fluorinated 
poly(arylene ether) as aforesaid. In still another embodiment, the 
electronic article is a circuit board in which the substrate is a 
fluorinated poly(arylene ether).

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The fluorinated poly(arylene ethers) of this invention can be made by the 
condensation polymerization of a diphenol (I) with a fluorinated monomer 
(II): 
##STR6## 
In the equation above, --W--, --X, q, and n have the same meaning as 
defined earlier. Suitable diphenols (I) include 
4,4'-(hexafluoroisopropylidene)-diphenol, 
4,4'-isopropylidene-di(2,6-dimethylphenol), 4,4'-(1-phenylethylidene) 
bisphenol, 4,4'-isopropylidenediphenol, 9,9'-bis(4-hydroxyphenyl)fluorene, 
1,5-dihydroxynapthalene, 2,7-dihydroxynapthalene, resorcinol, and 
4,6-dichlororesorcinol, corresponding to fluorinated poly(arylene ether) 
repeat units in which --W-- is: 
##STR7## 
Preferred diphenols (I) include 4,4'-(hexafluoroisopropylidene)diphenol, 
9,9'-bis(4-hydroxyphenyl)fluorene, and 1,5-dihydroxynaphthalene. 
Suitable fluorinated monomers (II) include hexafluorobenzene, 
decafluorobiphenyl, pentafluorobenzene, octafluorotoluene, 
1,4-dibromotetrafluorobenzene, chloropentafluorobenzene, 
allylpentafluorobenzene, and 2,2',3,3',5,5',6,6'-octafluorobiphenyl, 
corresponding to fluorinated poly(arylene ether) repeat units in which 
##STR8## 
Preferred fluorinated monomers includes hexafluorobenzene and 
decafluorobiphenyl. 
Contrary to what has been taught in the art, it has been discovered that 
complete fluorine substitution of the aromatic ring in monomers (II) is 
not necessary for effective polymerization, monomers such as 
pentafluorobenzene, octafluorotoluene, 1,4-dibromotetrafluorobenzene, and 
chloropentafluorobenzene being suitable. 
The two monomers are used in substantially stoichiometric amounts if high 
molecular weight polymer is desired. Alternatively, if lower molecular 
weight material is desired, for example to facilitate the preparation of 
solutions for spin or other solvent coating operations, a slight 
stoichiometric excess of either monomer can be used to control the 
molecular weight. 
A base such as an alkali metal carbonate, bicarbonate, or hydroxide is 
added to the polymerization mixture to convert the phenoxy groups to the 
corresponding phenoxides. Sodium and potassium carbonate are preferred. A 
polar aprotic solvent, such as N,N-dimethylacetamide, 
N,N-dimethylformamide, or 1-methyl-2-pyrrolidinone is used. The use of 
such solvents is advantageous compared to other solvents such as 
nitrobenzene, which are more toxic and which are not soluble in water, 
thereby requiring work-up of the polymerization mixture in an organic 
solvent as opposed to water. The reaction is carried out at an elevated 
temperature, although such temperature should not be excessively high. A 
temperature between about 50.degree. C. and about 125.degree. C. is 
generally suitable, with a temperature between about 60.degree. and about 
90.degree. C. being especially preferred. Reaction times are typically 
between about 10 and about 72 hours. 
The following repeat units are preferred: 
##STR9## 
The polymers can be homopolymers, consisting essentially of a single repeat 
unit such as one of the aforementioned ones. Or, they can be copolymers 
comprising a repeat unit of this invention in combination with another 
repeat unit of this invention or with a different type of repeat unit. 
Fluorinated poly(arylene ether) copolymers can be made for example by 
using two different diphenols (I) as comonomers, or two different 
fluorinated monomers (II) as comonomers. A preferred copolymer comprises 
repeat units (A) and (N): 
##STR10## 
Another preferred copolymer comprises the repeat units (A) and (D). Yet 
another preferred copolymer comprises repeat units (A) and (O) 
##STR11## 
Still other preferred copolymers comprise repeat unit (A) and either 
repeat unit (P) or (Q) or repeat unit (D) with repeat unit (Q): 
##STR12## 
In a copolymer where a repeat unit of this invention is combined with a 
repeat unit of another type of polymer, it is preferred that at least 60 
mole %, more preferably at least 80 mole %, of the repeat units are a 
fluorinated aromatic ether repeat unit according to this invention. A 
copolymer can be alternating, random, or block. 
The preparation and properties of the above fluorinated poly(arylene 
ethers) is also described in copending commonly assigned application Ser. 
No. 07/510,386, entitled "Fluorinated Poly(arylene Ethers)," filed Apr. 
17, 1990, the disclosure of which is incorporated herein by reference. 
FIG. 1a shows a multichip module 1 of this invention. Substrate 2, 
typically made of silicon, glass, or ceramic, supports high density 
multilayer interconnect 3 in which the dielectric material providing 
insulation between the various layers is a fluorinated poly(arylene 
ether). On interconnect 3 are mounted semiconductor chips 4a-d, which are 
connected to each other by electrical conductors in interconnect 3. 
Substrate 1 may also contain electrical conductors, for example for power 
and ground. Lead frames 5 (only one labeled for simplicity) provide 
connections to external circuitry. 
FIG. 1b shows a partial cross-section of multilayer interconnect 3 
supported on substrate 2. Layers of electrical connections 10a-c are 
separated from each other by a fluorinated poly(arylene ether) dielectric 
12. Via 11 provides connections between the various layers as necessary. 
Interconnect 3 is connected to an integrated circuit chip (not shown) by 
bond pad 13. Via 11 is shown here in the stacked pillar design, although 
it is to be understood that other designs conventional in the art, such as 
the stair-stepped or nested via designs, can be used. Other multichip 
module designs in which the fluorinated poly(arylene ethers) of this 
invention can be used as interlayer dielectrics is disclosed in Balde, 
"Overview of Multichip Technology", Electronic Materials Handbook, vol. 1, 
Packaging ASM International, p. 297-312 (1989), the disclosure of which is 
incorporated herein by reference. 
The fluorinated poly(arylene ethers) can also be used as interlayer 
dielectrics in an interconnect associated with a single integrated circuit 
chip. FIG. 2 shows this embodiment in cross-section. Integrated circuit 
chip 15 has on a surface thereof plural layers 16 of poly(arylene ether) 
dielectric and multiple layers of metal conductors 17. 
The fluorinated poly(arylene ethers) of this invention can further be used 
as protective coatings on integrated circuit chips, for protection against 
alpha particles. Semiconductor devices are susceptible to soft errors when 
alpha particles emitted from radioactive trace contaminants in the 
packaging or other nearby materials strike the active surface. FIG. 3 
shows schematically an integrated circuit having a protective coating of 
fluorinated poly(arylene ether). Integrated circuit chip 25 is mounted on 
substrate 26 and held in place with the assistance of adhesive 27. A 
coating of fluorinated poly(arylene ether) 28 provides an alpha particle 
protection layer for the active surface of chip 25. Optionally, additional 
protection is provided by encapsulant 29, made of for example epoxy or 
silicone. Conductor 30 provides connections between chip 25 and conductors 
(not shown) on substrate 26 and thence to external circuitry. 
The fluorinated poly(arylene ethers) can also be used as a substrate 
(dielectric material) in circuit boards (also referred to as printed 
wiring boards or PWB's). FIG. 3a shows in cross-section a circuit board 35 
made of a substrate 36 having on a surface thereof a pattern of conductors 
37. Substrate 36 is made of a fluorinated poly(arylene ether) of this 
invention. Substrate 36 may be reinforced with woven nonconducting fibers, 
such as glass cloth. Although in FIG. 3a the circuit board is shown as 
single sided, those skilled in the art will appreciate that other 
constructions, such as double sided or multilayer, can also be made with a 
fluorinated poly(arylene ether) substrate. 
Films or coatings of fluorinated poly(arylene ethers) can be formed by 
solution techniques such as spraying, spin coating, or casting, with spin 
coating being preferred. Preferred solvents are 2-ethoxyethyl ether, 
cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, methyl 
isobutyl ketone, 2-methoxyethyl ether, 5-methyl-2-hexanone, 
.gamma.-butyrolactone, and mixtures thereof. Typically the coating 
thickness is between about 3 to about 15.mu.. 
Additives can be used to enhance or impart particular target properties, as 
is conventionally known in the polymer art, including stabilizers, flame 
retardants, pigments, plasticizers, surfactants, and the like. Compatible 
or non-compatible polymers can be blended in to give a desired property. 
Polymers for electronic applications desirably contain low levels 
(generally less than 20 ppm) of ionic impurities. If a polymer is made by 
a synthetic route which requires the use of a transition metal reagent or 
catalyst, the effective removal of transition metal residues may be a 
difficult task. An advantage of the instant polymers is that they can be 
made by a route which does not involve transition metal species, and the 
potassium (or sodium) carbonate reagent and potassium (or sodium) fluoride 
by-product can be easily removed. 
The fluorinated poly(arylene ethers) show good high temperature stability. 
For example, polymer (A) shows by TGA an initial weight loss in air at 
500.degree. C. However, they also unexpectedly crosslink when heated in 
air at temperatures above 300.degree. C., as shown by the formation of 
large amounts of gelled material. Preferably, the crosslinking temperature 
is between about 300.degree. and about 425.degree. C. It appears that the 
presence of oxygen is required for the crosslinking reaction to take 
place, as similar heating cycles in nitrogen do not lead to the formation 
of gel. This characteristic makes the fluorinated poly(arylene ethers) 
particularly useful in the hereindescribed electronic applications, 
because they can be readily applied from solution, and then be converted 
into a solvent resistant coating by heating in air. 
The fluorinated poly(arylene ethers) can also be crosslinked by bistriazene 
compounds of the formula 
##STR13## 
wherein --R.sub.1, --R.sub.2, --R.sub.3, and --R.sub.4 are independently 
--H, --C.sub.6 H.sub.5, --C.sub.6 H.sub.4 Y', or C.sub.1 -C.sub.4 alkyl; 
--R.sub.5 -- is --O--, --SO.sub.2 --, 
##STR14## 
--B is --F, --Cl, --Br, --CH.sub.3, or --CF.sub.3 ; r is 0, 1, 2, 3, or 4; 
and --Y' is halogen, --NO.sub.2, --C.sub.6 H.sub.5, or C.sub.1 -C.sub.4 
alkyl. 
Preferably, each of --R.sub.1, --R.sub.2, --R.sub.3 and --R.sub.4 is methyl 
and r is 0. Also preferably, --R.sub.5 -- is 
##STR15## 
It is also preferred that the bistriazene groups be located para- to the 
--R.sub.5 -- group. 
Particularly preferred bistriazene crosslinking agents are 
##STR16## 
These bistriazene crosslinking agents can be prepared by treating a 
solution (in a solvent such as tetrahydrofuran or methanol) of a diamine 
of the formula 
##STR17## 
wherein --R.sub.5 --, --B, and r are as defined hereinabove, with 
hydrochloric acid (added gradually, with stirring). Then a solution of 
sodium nitrite is added gradually, with cooling. After a reaction perior 
of about 1 hour, the solvent is removed under reduced pressure. The 
residue is neutralized to pH 6-7 and treated with the dihydrochloride of a 
diamine such as dimethylamine. The preparation of these bistriazene 
compounds is further disclosed in copending, commonly assigned application 
U.S. Pat. No. 07/447,750, filed Dec. 8, 1989, the disclosure of which is 
incorporated herein by reference. 
The bistriazene crosslinking agent is used in an amount effective to 
crosslink the fluorinated polymer, preferably between about 10 and about 
40, more preferably between about 15 and about 30 weight %, based on the 
combined weights of the polymer and bistriazene compound. The fluorinated 
poly(arylene ether) and the bistriazene compound are intimately mixed, 
preferably by solution mixing. A film of the mixture is formed, for 
example by spin coating, and the solvent is removed. Crosslinking is 
effected by heating to a temperature above the decomposition temperature 
of the bistriazene compound, typically between 300.degree. and 400.degree. 
C., optionally with a stepped or stagewise heating profile, typically for 
between about 15 and 90 minutes total time. 
It is believed that, when heated up to or above a threshold temperature, 
the triazene groups decompose to form phenyl radicals. These then insert 
into aromatic groups in the fluorinated poly(arylene ether) to form 
aryl-aryl crosslinkages, as illustrated by the following equations: 
##STR18## 
As a matter of convenience, in the equations the triazene groups have been 
depicted as decomposing simultaneously to give a diradical. It is 
possible, if not likely, that the decomposition is not entirely 
simultaneous, so that monoradicals are also formed, which, however, would 
react in a similar fashion, albeit sequentially. A noteworthy aspect is 
that the crosslinks are via aryl-aryl bonds. Compared to their aliphatic 
counterparts, these are much less vulnerable to thermooxidative or other 
chemical attack and hence stabler. 
Another method of crosslinking fluorinated poly(arylene ethers) is with a 
peroxydic compound, such as dicumyl peroxide, cumene hydroperoxide, or 
benzoyl peroxide. An initimate mixture of the polymer and the peroxydic 
compound is heated to a temperature of between about 350.degree. C. and 
about 425.degree. C., preferably about 400.degree. C., under nitrogen. 
Typically, the peroxydic compound is used in an amount of between about 5 
and about 20% by weight, based on the combined amounts of polymer and 
peroxydic compound, with about 10 wt. % being preferred. In some 
fluorinated poly(arylene ethers), peroxide crosslinking may be facilitated 
by their possessing reactive side chains, such as the allyl groups in 
polymer (J), although the presence of such functionalities is not required 
for effective peroxide crosslinking. 
Fluorinated poly(arylene ethers) are also useful as adhesives and matrix 
resins for composite applications. Further, they are also useful as 
solvent resistant, crosslinked films for a variety of applications, such 
as wires having a wrapped insulation, especially after crosslinking. 
The practice of our invention can be further understood by reference to the 
following examples, which are provided by means of illustration, not 
limitation. 
EXAMPLE 1 
This example describes the preparation of a polymer having repeat unit (A): 
To a 500 mL round bottom flask was added 15.01 g (0.0447 mole) of 
4,4'-(hexafluoroisopropylidene)diphenol ("6F-diphenol"), 15.29 g (0.0458 
mole) of decafluorobiphenyl, 240 g of dimethylacetamide ("DMAc"), and 
16.85 g (0.125 mole) of potassium carbonate. The mixture was heated with 
stirring under nitrogen at about 80.degree. C. for 23 hours. The mixture 
was filtered hot to remove the unreacted potassium carbonate and potassium 
fluoride by-product. About 75 mL of DMAc was removed by rotary 
evaporation. The solution was cooled to room temperature and poured into 
water to precipitate the polymer. The polymer was filtered, washed three 
times with water, suspended in 200 mL of ethanol for 2 hours, filtered, 
and dried at 100.degree. C. for 2 hours to yield a white powder. A 
solution of 2 grams of polymer in 8 grams of a 50/50 mixture of 2-ethoxy 
ethyl ether and cyclohexanone was spin coated onto a ceramic substrate and 
dried 15 minutes at 100.degree. C., 20 minutes at 180.degree. C., and 45 
minutes at 400.degree. C. The resulting polymer film was tough and 
flexible, insoluble in 2-ethoxy ethyl ether, and had a T.sub.g of 
189.degree. C. by DSC (192.degree. C. by TMA). 
EXAMPLE 2 
This example describes the preparation of a polymer having repeat unit (B); 
To a 100 mL round bottom flask was added 2.20 g (0.0118 mole) of 
hexafluorobenzene, 3.90 g (0.0116 mole) of 6F-diphenol, 4.0 g (0.030 mole) 
of potassium carbonate, and 50 g of DMAc. The mixture was heated with 
stirring under nitrogen at about 70.degree. C. for 48 hours. The mixture 
was then worked up as described in Example 1 to yield a white powder. A 
film of the polymer obtained was tough and flexible, insoluble in 2-ethoxy 
ethyl ether, and had a T.sub.g of about 185.degree. C. by DSC. 
EXAMPLE 3 
This example describes the preparation of a polymer having repeat unit (C): 
The reaction of Example 1 was repeated except that 12.7 g of 
4,4-isopropylidene bis(2,6-dimethylphenol) ("tetramethyl Bisphenol A") was 
used in place of the 6F-diphenol and the reaction was heated to 80.degree. 
C. for 72 hours. 22.3 g of polymer was obtained. A film of the polymer had 
a moisture absorption of 0.15% after immersion in 50.degree. C. water for 
16 hours. 
EXAMPLE 4 
This example describes the preparation of the copolymer having repeat units 
(A) and (N): The reaction of Example 1 was repeated except that a mixture 
of 7.51 g of 6F-diphenol and 2.458 g of resorcinol was used in place of 
the 6F-diphenol. 19.8 g of polymer was obtained. A film of the polymer had 
a moisture absorption of 0.10% after immersion in 50.degree. C. water for 
16 hours. 
EXAMPLE 5 
The polymer having the repeat unit (D) was prepared as follows: To a 250 mL 
round bottom flask was added 10.15 g (0.029 mole) of 
9,9-bis(4-hydroxyphenyl)fluorene, 9.97 g (0.0298 mole) of 
decafluorobiphenyl, 115 g of DMAc, and 10.0 g (0.074 mole) of potassium 
carbonate. The mixture was heated with stirring under nitrogen at 
75.degree. C. for 16 hours. The mixture was cooled to room temperature, 
poured into rapidly stirring water to precipitate the polymer, filtered, 
washed twice with water, filtered and dried. A white fluffy powder was 
obtained. Two grams of the white polymer powder were dissolved in 8 grams 
of a 50/50 mixture of cyclohexanone and 2-ethoxy ethyl ether. About 1.5 mL 
of the polymer solution was spin coated onto a glass substrate and dried 
10 min at 100.degree. C., 15 min at 200.degree. C., and 30 min at 
400.degree. C. The resulting polymer film was released from the glass 
substrate by immersion in water to yield a tough, flexible, transparent 
film. The film had a dielectric constant of 2.62 at 0% RH and a dielectric 
constant of 2.68 at 58% RH. The polymer had a T.sub.g of about 258.degree. 
C. by DSC. 
EXAMPLE 6 
This example describes the preparation of the polymer having the repeat 
unit (E): The procedure of Example 5 was repeated, except that 5.54 g 
(0.0298 mole) of hexafluorobenzene was used in place of the 
decafluorobiphenyl and the reaction was allowed to run for 42 hours. The 
resulting polymer film had a dielectric constant of 2.65 at 0% RH and of 
2.73 at 58% RH. 
EXAMPLE 7 
This example describes the preparation of the copolymer having repeat units 
(A) and (D): To a 250 mL round bottom flask was added 5.07 g (0.0145 mole) 
of 9,9-bis(4-hydroxyphenyl)fluorene, 4.87 g (0.0145 mole) of 6F-diphenol, 
9.97 g (0.0298 mole) of decafluorobiphenyl, 115 g of DMAc, and 10.0 g 
(0.074 mole) of potassium carbonate. The mixture was heated with stirring 
under nitrogen at 75.degree. C. for 16 hours. The mixture was cooled to 
room temperature, poured into rapidly stirring water to precipitate the 
polymer, filtered, washed twice in 300 mL of water, filtered and dried. A 
white fluffy powder was obtained. Two grams of the white polymer powder 
were dissolved in 8 grams of a 50/50 mixture of cyclohexanone and 2-ethoxy 
ethyl ether. About 1.5 mL of the polymer solution was spin coated onto a 
glass substrate and dried 10 min. at 100.degree. C., 15 min. at 
200.degree. C., and 30 min. at 400.degree. C. The resulting polymer film 
was released from the glass substrate by immersion in water to yield a 
tough, flexible, transparent film. The film had a dielectric constant of 
2.60 at 0% RH and 2.66 at 58% RH. 
EXAMPLE 8 
This Example describes the preparation of a polymer having repeat unit (F). 
To a 100 mL round bottom flask was added 3.50 g (0.0208 mol) of 
pentafluorobenzene, 7.00 g (0.0208 mol) of 6F-diphenol, 4.2 g of potassium 
carbonate, and 50 g of DMAc. The mixture was heated to 80.degree. C. for 
24 hours under nitrogen with stirring, then heated to 120.degree. C. for 
an additional 36 hours. The mixture was allowed to cool to room 
temperature and poured into water precipitate the polymer as a lightly 
colored powder. The polymer was washed three times with water and dried at 
room temperature for 18 hours and at 100.degree. C. for 4 hours. One gram 
of polymer was dissolved in 4 grams of a 1:1:1 mixture of DMAc, 2-ethoxy 
ethyl ether, and cyclohexanone. The mixture was spin coated on to a glass 
substrate and cured 15 min at 100.degree. C., 15 min at 200.degree. C., 
and 15 min at 400.degree. C. to yield an amber film. The polymer had a 
moisture absorption of 0.15%. Based on model studies with similar 
fluorinated benzenes, discussed in more detail below, and the expected 
mechanism for the polymerization reaction, it is believed that in the 
pentafluorobenzene two fluorines are displaced, with the hydrogen being 
retained. Polymer (F) had a Tg of 120.degree. C. by DSC. 
EXAMPLE 9 
This example describes the preparation of a polymer having repeat unit (G). 
The procedure in Example 8 was repeated except that 4.99 g (0.0211 mol) of 
octafluorotoluene was used in place of pentafluorobenzene and 7.38 g 
(0.0211 mol) of 9,9-bis(4-hydroxyphenyl)fluorene was used instead of the 
6F-diphenol. The reaction was run at 80.degree. C. for 24 hours and then 
at 120.degree. C. for an additional 24 hours. A white powder was obtained. 
Again, it is believed that two ring fluorines are displaced, with the 
trifluoromethyl group remaining intact. The polymer had a T.sub.g of 
260.degree. C. by DSC. 
EXAMPLE 10 
This Example describes the preparation of a polymer having repeat unit (H). 
The procedure in Example 9 was repeated except that 6.40 g (0.0208 mol) of 
1,4-dibromotetrafluorobenzene was used in place of octafluorotoluene. A 
white powder was obtained. One gram of the powder was dissolved in 4 grams 
of DMAc and spin coated on to glass substrate and cured as described in 
Example 8 to yield an amber film. The polymer had a dielectric constant of 
2.6 and a moisture absorption of 0.15%. Its T.sub.g was 199.degree. C. as 
measured by DSC. 
GC-MS analysis of the products from the model reaction between phenol (2 
equivalents) and 1,4-dibromotetrafluorobenzene showed that two fluorines 
were displaced, with the two bromines being retained and a mixture of 
isomeric products being obtained. Thus, it is believed that in polymer 
(H), the two bromines were also retained. 
EXAMPLE 11 
This Example describes the preparation of a polymer with repeat unit (I). 
To a 100 mL round bottom flask was added 5.05 g (0.0249 mol) of 
chloropentafluorobenzene, 9.10 g (0.0260 mol) of 
9,9-bis(4-hydroxyphenyl)fluorene, 65 g of DMAc, and 11.5 g of potassium 
carbonate. The mixture was heated to 100.degree. C. for 27 hours under 
nitrogen with stirring. The mixture was allowed to cool to room 
temperature and poured into water with stirring to precipitate the 
polymer. The polymer was washed with three times with water and dried at 
room temperature for 18 hours and at 100.degree. C. for 5 hours to yield a 
white powder. Two grams of the polymer were dissolved in 8 mL of a 1:1 
mixture of 2-ethoxy ethyl ether and cyclohexanone, spin coated onto a 
glass substrate, and dried as described in Example 8. An amber film was 
obtained. The polymer had a moisture absorption of 0.1%. 
GC-MS analysis of the product from the model reaction between phenol (2 
equivalents) and chloropentafluorobenzene showed that two fluorines were 
displaced, with the chlorine being retained and a mixture of isomeric 
products being obtained. Thus, it is believed that, in polymer (I), the 
chlorine was also retained. 
EXAMPLE 12 
This Example describes the preparation of a polymer with repeat unit (J). 
To a 100 mL round bottom flask was added 4.20 g (0.0202 mol) of 
allylpentafluorobenzene, 6.85 g (0.0204 mol) of 6F-diphenol, 45 mL of 
DMAc, and 8.0 g of potassium carbonate. The mixture was heated to 
110.degree. C. under nitrogen with stirring for 72 hours. The mixture was 
allowed to cool to room temperature and was poured into water to 
precipitate the polymer. The polymer was washed with 100 mL of deionized 
water and 100 mL of denatured ethanol and dried in air for 3 days to yield 
a light yellow powder. Three grams of the powder and 0.15 g of t-butyl 
peroxybenzoate were dissolved in 8.5 mL of DMAc and spin coated onto a 
glass substrate and dried 10 min at 110.degree. C. and 20 min at 
200.degree. C. to yield an amber film that was insoluble in DMAc. 
GC-MS analysis of the product from the reaction between phenol (2 
equivalents) and allylpentafluorobenzene showed that two fluorines were 
displaced, with the allyl group being retained and a mixture of isomeric 
products being obtained. Thus, it is believed that, in the polymer 
described above, the allyl group was also retained. 
EXAMPLE 13 
This example describes the preparation of a polymer with repeat unit (K): 
To a 100 ml round bottom flask was added 1.25 g (0.0042 mol) 
2,2',3,3',5,5',6,6'-octafluorobiphenyl ("OFB"), 1.41 g (0.0042 mol) of 
6F-diphenol, 19 g of DMAc, and 2 g of potassium carbonate. The mixture was 
heated to 120.degree. C. for 72 hours under nitrogen with stirring. The 
mixture was allowed to cool to room temperature and poured into water to 
precipitate the polymer. The polymer was collected by filtration, washed 
with 75 ml of a 50/50 mixture of ethanol and water, and dried over night 
at room temperature, followed by 1 hour at 100.degree. C. to yield a white 
powder. The polymer had a T.sub.g of 147.degree. C. by DSC. 
GC/MS analysis of the product from the reaction between 4-methoxyphenol (2 
equivalents) and OFB showed that two fluorines were displaced, with 
retention of the two hydrogens, and a mixture of isomeric products being 
obtained. Thus, it is believed that, in the polymer described above, the 
two hydrogens were also retained. 
EXAMPLE 14 
This example describes the preparation of a polymer with repeat unit (L). 
The procedure of Example 12 was repeated with the exception that 6.22 g 
(0.0202 mol) of 1,4-dibromotetrafluorobenzene, 7.07 g (0.0202 mol) of 
9,9-bis(4-hydroxyphenyl)fluorene, 10 g potassium carbonate, and 55 mL of 
DMAc were used. The polymer was obtained as a white powder, T.sub.g 
291.degree. C. by DSC. 
EXAMPLE 15 
This example describes the preparation of a polymer with repeat unit (M). 
To a 250 ml round bottom flask was added 10.2 g (0.0354 mol) of 
4,4'-(1-phenylethylidene) bisphenol, 11.6 g (0.0347 mol) of 
decafluorobiphenyl, 12 g of potassium carbonate, and 135 g of DMAc. The 
mixture was heated to 80.degree. C. under nitrogen with stirring for 16 
hours. The mixture was allowed to cool to room temperature and poured into 
water to precipitate the polymer. The polymer was filtered, washed with 
water, and dried. Two grams of the polymer were dissolved in 8 g of a 
mixture of 2-ethoxy ethyl ether and cyclohexanone (ratio 8:2, 
respectively) and spin coated onto a glass substrate, and dried 15 min at 
100.degree. C., 15 min at 200.degree. C., and 15 min at 400.degree. C. to 
yield a flexible, transparent film. The polymer had a T.sub.g of 
208.degree. C. by DSC and a dielectric constant of 2.64 at 0% RH. 
EXAMPLE 16 
This example describes the preparation of a copolymer having repeat units 
(A) and (O), in a molar ratio of 1:4. To a 100 mL round bottom flask was 
added 3.75 g (0.021 mol) of 4,6-dichlororesorcinol, 1.76 g (0.0053 mol) of 
6F-diphenol, 8.80 g (0.026 mol) of decafluorobiphenyl, 62 g of DMAc, and 
10 g of potassium carbonate. The mixture was heated under nitrogen for 8 
hours at 110.degree. C. The mixture was poured without cooling into water 
to precipitate the polymer. The polymer was collected by filtration, 
washed with water, and dried to yield a light pink powder. The polymer had 
a T.sub.g of 149.degree. C. by DSC. 
EXAMPLE 17 
This example describes the preparation of a polymer (referred to 
hereinafter as BPA-DFB) from 4,4'-isopropylidenediphenol and 
decafluorobiphenyl: The reaction of Example 1 was repeated except that 
10.20 g of 4,4'-isopropylidenediphenol ("Bisphenol A") was used in place 
of the 6F-diphenol. 21.5 g of polymer was obtained from the reaction. A 
film of the polymer had a bulk moisture absorption of 0.2% after immersion 
in 50.degree. C. water for 16 hours. 
EXAMPLE 18 
This is a comparative example in which a polymer not according to this 
invention, having the repeat unit 
##STR19## 
is prepared and compared against the polymers of this invention. 
To a 100 mL round bottom flask was added 1.80 (0.009 moles) g of 
4,4'-oxydianiline ("ODA") and 30 mL of dry 1-methyl-2-pyrrolidinone 
("NMP"). The solution was cooled in an ice bath and 2.006 g (0.0092 moles) 
of pyromellitic dianhydride (PMDA) was added with stirring under nitrogen. 
A viscous, amber solution resulted. The polymer solution was spin coated 
onto a 4 by 4 inch (ca. 10 by 10 cm) glass substrate and dried for 10 min 
at 100.degree. C., 15 min at 200.degree. C., and 30 min at 350.degree. C. 
to yield an amber film. The film showed a bulk moisture absorption of 
2.55% after immersion in 50.degree. C. water for 16 hours. 
EXAMPLE 19 
This is another comparative example in which another prior art polyimide, 
referred to herein as PI7, is prepared and compared against the polymers 
of this invention. 
##STR20## 
To a 100 mL round bottom flask was added 3.35 g (0.009 mole) of 
4,4'-bis(4-aminophenoxy)biphenyl and 17 g of NMP. After stirring at room 
temperature under nitrogen for 45 minutes, a solution of 4.00 g (0.009 
mole) of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride 
("6FDA") in 14 g of NMP was added dropwise with stirring over 10 minutes. 
After stirring an additional 24 hours at room temperature a viscous 
solution (2650 cps) resulted. The solution was spin coated on to a 4 by 4 
inch (ca. 10 by 10 cm) glass substrate at 2000 rpm and dried 30 min at 
100.degree. C., 20 min at 200.degree. C., and 30 min at 350.degree. C. to 
yield an amber film. This polyimide film showed a bulk moisture absorption 
of 0.85% after immersion in 50.degree. C. water for 16 hours. The 
properties of PI7 are compared against those of polymers of this invention 
in Table I, below. 
Table I compares the dielectric properties of the polymers of this 
invention against the properties of the comparative polymers. The 
dielectric constants were measured at 25.degree. C. and 10 KHz by the 
method described in the aforementioned copending commonly assigned 
application of Mercer, Ser. No. 07/447,771. It can be seen from Table I 
that the polymers of this invention have significantly lower dielectric 
constants (.epsilon.), below 2.80 at 0% RH and as low as 2.50, compared to 
.epsilon.'s above 2.80, up to 3.16, for the comparison polymers. Further, 
the .epsilon.'s of my polymers are less sensitive to variations in the 
ambient humidity. At about 60% RH, their .epsilon.'s increase only 
slightly, as evidenced by a small slope of between about 10 and about 30, 
while the comparison polymers have a slope of between about 60 and about 
100. In a microelectronic article, it is very important that the 
dielectric material have a low .epsilon., preferably below 3 in both dry 
and wet environments. These differences between my polymers and the 
comparison polymers are shown graphically in FIG. 4. 
TABLE I 
______________________________________ 
Dielectric Constant of Polymers 
Dielectric Constant (.epsilon.) at 
25.degree. C. and 10 KHz 
Ex. Polymer .epsilon..sub.dry (@ 0% RH) 
.epsilon..sub.wet (% RH) 
Slope* 
______________________________________ 
1 A 2.504 2.62 (65.3) 
17.8 
2 B 2.50 2.63 (72.3) 
18.0 
3 C 2.78 2.89 (65.1) 
16.9 
4 A/N copolymer 
2.62 2.68 (54.1) 
11.1 
5 D 2.62 2.68 (58) 
10.3 
6 E 2.65 2.73 (58) 
13.8 
7 A/D copolymer 
2.60 2.66 (58) 
10.3 
8 BPA-DFB 2.617 2.787 (65.3) 
26.1 
9 PMDA-ODA 3.16 3.76 (58.2) 
103.2 
10 PI-7 2.85 3.223 (59.4) 
63.0 
______________________________________ 
##STR21## 
EXAMPLE 20 
This example describes the preparation of a multilayer high density 
interconnect article suitable for use in a multichip module or in 
combination with a single integrated circuit chip. 
A solution of 22.5 g of polymer (A) in 77.5 g of a 50/50 mixture of 
2-ethoxy ethyl ether and cyclohexanone was prepared. A polymeric 
insulating layer was applied to a ceramic substrate in the following 
manner: (1) a 5 mL aliquot of the polymer solution was spin coated onto a 
clean 125 mm diameter ceramic substrate. (2) The coating was dried at 
100.degree. C. for 15 min and at 200.degree. C. for another 15 min. (3) A 
second 5 mL aliquot was applied and cured as above with an additional cure 
for 60 min at 400.degree. C. A conductive material was formed by blanket 
sputtering 200 .ANG. of chromium followed by 5 microns of copper, and 
finally another 500 .ANG. of chromium. The metal was photolithographically 
patterned. 
A second polymeric insulating layer was applied over the patterned metal 
layer by the three-step process described above. An aluminum metal layer 
was blanket sputtered onto the dielectric, photolithographically 
patterned, and vias were generated in the second dielectric layer so that 
electrical contact could be made with the first metal layer. The aluminum 
layer was removed. A second metal layer of chromium-copper-chromium was 
applied as described above and electrical contact was made with the first 
layer by means of the vias. The second metal layer was then also 
photolithographically patterned. 
All metal layers in the device showed excellent adhesion to the 
fluoropolymer and there was no observable delamination of metal to polymer 
or polymer to polymer. 
EXAMPLE 21 
A sample of polymer (A) was crosslinked by curing in air, for the times and 
at the temperature indicated in Table II, below, to produce the indicated 
gel contents (determined by Sohxlet extraction with DMAc for 24 hrs): 
TABLE II 
______________________________________ 
Crosslinking of Polymer (A) 
Cure Temperature (.degree.C.) 
Cure Time (min) 
Gel (%) 
______________________________________ 
300 30 55 
400 15 79 
400 30 80 
400 60 86 
400 105 92 
______________________________________ 
However, when polymer (A) was cured in nitrogen for 13 min at 300.degree. 
C. and then 27 min at 400.degree. C., no gel was detected. 
EXAMPLE 22 
This comparative example demonstrates the preference for fluorination in 
the bisphenol moiety for the preparation of fluorinated poly(arylene 
ethers) having enhanced thermal stability. The thermal stability of 
polymer (A) (derived from 6F-diphenol and having two --CF.sub.3 groups) 
was compared to that of the polymer BPA-DFB (derived from Bisphenol-A and 
consequently having two --CH.sub.3 's in the corresponding position) by 
thermogravimetric analysis (TGA), under isothermal conditions in air. The 
results are provided in Table III. 
TABLE III 
______________________________________ 
Comparison of Thermal Stability 
After 3 hr at Weight loss (%) by TMA 
temperature (.degree.C.) 
Polymer (A) 
Polymer BPA-DFB 
______________________________________ 
@ 400.degree. C. 
2.5 3.0 
@ 425.degree. C. 
5.0 20.0 
@ 450.degree. C. 
19.8 55.0 
______________________________________ 
EXAMPLE 23 
This example describes the deposition of layers of polymer (D), crosslinked 
with a bistriazene crosslinking agent. A solution of polymer (D) (about 23 
weight percent solids) in a solvent system of 1:1:1 bis(2-ethoxy 
ethyl)ether, DMAc, and 5-methyl-2-hexanone (W/W/W) was prepared. To this 
was added 16.7 weight % of the bistriazene (1) 
##STR22## 
This solution was then coated onto a substrate (ceramic or silicon) by 
spin coating. The coated substrate was heated in a nitrogen purged oven 
having a conveyor belt which ran the substrate through the oven according 
to a temperature profile of 300.degree. C. for 6.5 min, 400.degree. C. for 
13.5 min, and then cooling to room temperature over 20 min. This procedure 
produced a clear coating of crosslinked polymer (D) which did not crack 
upon subsequent processing (e.g., during the deposition of additional 
polymer layers) and did not cause oxidation of metal conductors thereon. 
It was found that, to improve the adhesion of the crosslinked polymer (D) 
to the substrate, it is desirable to use a thin layer (about 1.mu. thick) 
comprising acetylene terminated polyimide (Thermid IP-615) and 
.gamma.-aminopropyltrimethoxysilane coupling agent, between polymer (D) 
and the substrate as an adhesion promoting interlayer. The 
polyimide/coupling agent layer is deposited onto the substrate and cured 
at 150.degree. C. for 10 min and then 200.degree. C. for 15 min. The 
polymer (D) layer is then coated on top and cured as described above. 
EXAMPLE 24 
This example describes the various steps of metallization, patterning, 
etching, and via formation on a substrate coated with polymer (D) as 
described in the previous example. 
Metal conductor traces were deposited on a cured polymer (D) coating by 
sputtering. The conductor was a chromium-copper-chromium sandwich, with 
200 .ANG. thick layers of chromium acting as tie-down layers for the 
copper (5.mu. thick). This conductor construction is preferable to the 
more conventional aluminum, which does not adhere as well to crosslinked 
polymer (D). 
The metal was covered with a photoresist, which was then covered with a 
mask and exposed to ultraviolet light. The exposed portions of the 
photoresist were removed by washing with sodium hydroxide solution, 
leaving portions of the metal exposed. The exposed metal was removed by 
etching with CRE-473 (tradename for a hydrochloric acid etchant, available 
from Transene) and ferric chloride to remove respectively the top chromium 
layer and the copper layer. The bottom chromium layer was etched away with 
CE 8001-N (tradename for a ceric ammonium nitrate-nitric acid etchant, 
available from Chemtech Industries). Laser ablation can also be used for 
removing the bottom chromium layer, but CE 8001-N is preferred because it 
is faster and less harsh on the polymer. 
After etching of the metal, the unexposed photoresist was removed by 
flooding the entire substrate wafer with ultraviolet light and developing 
off the remaining photoresist with sodium hydroxide. An alternative method 
is to strip off undeveloped photoresist with a 7:3:1 (V/V/V) mixture of 
NMP, deionized water, and methanol. 
The patterned metal is overcoated with more crosslinked polymer (D). A 
metal layer or via mask about 3.mu. thick is sputtered onto the polymer 
coating and photolithographically patterned as described above, to form 
holes in the metal where vias are desired. The entire wafer was ablated 
with a 308 nm laser, with polymer being removed wherever there was a hole 
in the metal until bottom metal was reached. The mask was then removed by 
etching. (To avoid etching the metal conductors along with the via mask, 
the via mask should be made of different, selectively etchable metal, such 
as aluminum). 
Using the above procedures, a substrate wafer carrying a plurality of 
multilayer units was prepared. This substrate and the units thereon is 
shown schematically in FIG. 5 (where like numerals depict like elements). 
Substrate 40 has thereon a plurality of multilayer units 41 (also shown in 
magnified overhead and crosssection views in FIG. 5a and 5b). Each unit 41 
has layers of metal conductors 43a and 43b isolated by a dielectric 42 of 
crosslinked polymer (D). Vias 44a and 44b provide interlayer connectivity. 
Each unit 41 can be viewed as a parallel plate capacitor. Twenty units 41 
were tested by measuring their capacitances. Each had a capacitance which 
agreed with that predicted by the equation 
EQU C=D.epsilon..sub.O A/L 
where C is the capacitance, D is the dielectric constant of the polymer 
interlayer, .epsilon..sub.O is the permittivity of free space, A is the 
area of the capacitor plates, and L is the distance separating the 
capacitor plates. (The distance between the capacitor plates (i.e., the 
layers of conductors) was determined to be 35.mu. by scanning electron 
microscopy.) 
EXAMPLE 25 
In this example, the dielectric properties of polymer (D) crosslinked with 
a bistriazene in the manner of Example 23 are compared with those of a 
benzocyclobutene ("BCB") resin (XU13005.02L available from Dow Chemical 
Company), proposed as a dielectric for electronic packaging applications. 
Capacitors were made from crosslinked polymer (D) and the BCB resin 
according to the procedure of Example 24. The capacitances of strips of 
five capacitors of made from each polymer were measured as a function of % 
RH, before and after aging. The results are provided in Table IV. 
TABLE IV 
______________________________________ 
Comparison of Aging Effects on Dielectric Constant 
of BCB XU13005.02L and Bistriazene Crosslinked Polymer (D) 
BCB Polymer (D) 
Aging in air Dielectric Dielectric 
@ 200.degree. C. (hrs) 
% RH Constant % RH Constant 
______________________________________ 
0 0 2.485 0 2.656 
21 2.494 30 2.690 
42 2.503 -- -- 
78 2.522 69 2.734 
24 0 2.747 0 2.623 
34 2.817 34 2.662 
71 2.897 71 2.702 
96 0 2.891 0 2.649 
33 3.008 33 2.687 
76 3.152 76 2.737 
336 0 3.198 0 2.614 
28 3.401 30 2.635 
62 3.603 73 2.673 
______________________________________ 
These results show that the dielectric properties of crosslinked polymer 
(D) compare favorably to those of the BCB resin. Although the BCB resin 
has a lower initial dielectric constant, upon exposure to elevated 
temperatures, as might occur in the course of the normal service life of 
an electronic article, the BCB resin's dielectric constant increases at a 
fairly sharp rate, with the increase being particularly noticeable at high 
% RH's. In contrast, the dielectric constant of polymer (D) remains low, 
below 2.8 at all aging time-relative humidity combinations. 
EXAMPLE 26 
In this example, the crosslinking of a variety of fluorinated poly-(arylene 
ethers) by a variety of bistriazene crosslinking agents is illustrated. 
A sample of fluorinated poly(arylene ether) (2 g) was combined in a 30 mL 
vial with cyclohexanone (4 g), .gamma.-butyrolactone (4 g), bistriazene 
compound (ca. 0.4 g) and a surfactant (Fluorad FC-431 from 3M, 2 drops). 
The mixture was stirred until all the solids had dissolved. The solution 
was allowed to sit until all bubbles formed by agitation had dispersed. A 
majority of the solution was deposited on a ceramic substrate and spin 
coated at 250 rpm to form a thick coating. The sample was soft-baked at 
100.degree. C. for 15 min, then at 200.degree. C. for another 15 min. The 
sample was then baked in a nitrogen-purged zone furnace according to the 
following cycle: 300.degree. C. for 6.5 min, 400.degree. C. for 13.5 min, 
and room temperature for 20 min, to yield a sample of approximately 1.5 g. 
This cured sample was removed from the ceramic substrate and divided into 
three equal sections. Each section was cut into small pieces and placed 
inside a pre-weighed gauze tube. The gauze tube was sealed and re-weighed. 
All three sections were placed inside a Soxhlet extraction apparatus and 
extracted with DMAc for 24 hr. After drying in a vacuum oven at 
100.degree. C. overnight, the samples were cooled and weighed again to 
determine the gel content. The results provided in Table V show that 
bistriazene compounds are generally effective crosslinking agents for 
fluorinated poly(arylene ethers): 
TABLE V 
__________________________________________________________________________ 
Crosslinking of Fluorinated Poly(arylene Ethers) 
by Bistriazine Compounds 
##STR23## 
Fluorinated poly- Wt. % 
(arylene ether) 
R.sub.5 Bistriazine 
Percent Gel 
__________________________________________________________________________ 
D control 0.00 3.3 .+-. 0.2 
##STR24## 4.76 64.1 .+-. 0.8 
D " 9.1 78.8 .+-. 1.0 
D " 13.04 86.4 .+-. 2.7 
D " 16.67 93.7 .+-. 2.2 
D 
##STR25## 4.76 46.6 .+-. 2.4 
D " 9.1 62.5 .+-. 2.4 
D " 13.04 68.6 .+-. 1.6 
D " 16.67 86.6 .+-. 2.6 
D 
##STR26## 9.1 87.1 .+-. 5.8 
D " 16.67 94.9 .+-. 0.7 
D 
##STR27## 16.67 81.2 .+-. 2.1 
D 
##STR28## 16.67 85.7 .+-. 0.5 
D m,m'- SO.sub.2 16.67 52.9 .+-. 2.2 
A control 0.00 0.8 .+-. 0.8 
A 
##STR29## 16.67 65.3 .+-. 2.9 
__________________________________________________________________________ 
EXAMPLE 27 
In this example, fluorinated poly(arylene ether) D is crosslinked with a 
peroxydic compound. Samples of polymer D containing 10% of dicumyl 
peroxide or cumene hydroperoxide were heated at 300.degree. C. for 6.5 min 
and then at 400.degree. C. for 13.5 min under nitrogen in an infra-red 
oven to produce crosslinked polymer having gel content of 94.0% and 81.4%, 
respectively. In comparison, a sample of polymer D similarly heated in the 
absence of any peroxide had a gel content of only 3.3%. The crosslinked 
polymers retained their low moisture absorption and dielectric constant 
characteristics. The sample crosslinked with dicumyl peroxide had a 
moisture absorption of 0.2% and a dielectric constant of 2.6 at 0% RH. 
In additional peroxide crosslinking experiments, polymers (A) and (D) were 
each crosslinked with 10 wt. % benzoyl peroxide to produce crosslinked 
polymers having gel content of about 51 and 49%, respectively. Polymer (A) 
was also crosslinked with 10 wt. % dicumyl peroxide to a gel content of 
69%. In comparison, a control sample of polymer (A), similarly heated in 
the absence of any peroxide, had a gel content of about 0.8%. 
EXAMPLE 28 
This example describes the preparation of a polymer with the repeat unit 
(M'). To a 100 mL round bottom flask was added 3.21 g (0.0093 mol) 
Bisphenol P, 3.12 g (0.00934 mol) decafluorobiphenyl, 4.2 g of potassium 
carbonate, and 22 g DMAc. The reaction mixture was heated at 100.degree. 
C. for 6 hours under nitrogen with stirring. The polymer was isolated as 
described in Example 5 to yield a white powder. The polymer had a T.sub.g 
of 162.degree. C. by DSC. A film of the polymer had a dielectric constant 
of 2.58 at 0% RH and 2.71 at 66.45% RH. 
EXAMPLE 29 
This example describes the preparation of the copolymer having repeat units 
(A) and (O). To a 100 mL round bottom flask was added 3.75 g (0.026 mol) 
of 4,6-dichlororesorcinol, 1.76 g (0.0052 mol) of 6F-diphenol, 10.45 g 
(0.031 mol) of decafluorobiphenyl, 12 g potassium carbonate, and 39 g of 
DMAc. The reaction mixture was heated to 110.degree. C. for 8 hours under 
nitrogen with stirring. The gelled reaction mixture was allowed to cool to 
room temperature and added to water and digested in a blender to isolate 
an off-white powder. The powder was washed with water and dried. The 
polymer had a T.sub.g of 149.degree. C. by DSC. 
EXAMPLE 30 
This example describes the preparation of the copolymer having repeat units 
(A) and (P). To a 100 mL round bottom flask was added 5.70 g (0.017 mol) 
of decafluorobiphenyl, 1.34 g (0.0083 mol) of 2,7-dihydroxynaphthalene, 
2.82 g (0.0083 mol) of 6F-diphenol. The reaction mixture was heated to 
90.degree. C. for 18 hours under nitrogen with stirring and allowed to 
cool to room temperature. The polymer was isolated by the procedure 
described in Example 5 to yield a white powder. The polymer had a T.sub.g 
of 190.degree. C. by DSC. A film of the polymer had a dielectric constant 
of 2.54 at 0% RH and 2.64 at 65.4% RH. 
EXAMPLE 31 
This example describes the preparation of the copolymer having repeat units 
(A) and (Q). The procedure described in the Example immediately above was 
repeated except that 1.34 g (0.0083 mol) of 1,5-dihydroxynaphthalene was 
used instead of 2,7-dihydroxynaphthalene. An off white powder was 
obtained. The polymer had a T.sub.g of 203.degree. C. by DSC. 
EXAMPLE 32 
This example describes the preparation of a copolymer having repeat units 
(D) and (Q) and its subsequent crosslinking with a peroxide. To a 250 mL 
round bottom flask was added 3.32 g (0.0207 mol) of 
1,5-dihydroxynaphthalene, 7.26 g (0.0207 mol) of 
9,9-bis(4-hydroxyphenyl)fluorene, 14.22 g (0.0427 mol) of 
decafluorobiphenyl, 17 g of potassium carbonate, and 127 g of DMAc. The 
mixture was heated to 85.degree. C. for 16 hr under nitrogen with stirring 
and then poured while still hot into a blender containing 300 mL of water 
to precipitate the polymer. The polymer was collected by filtration and 
washed twice more with 300 mL of water and dried. Two grams of polymer and 
0.22 g of dicumyl peroxide were dissolved in 8.5 g of a 1:1 mixture of 
.gamma.-butyrolactone and cyclohexanone. The solution was spin coated onto 
a ceramic substrate and cured as follows: 30 min at 130.degree. C., heat 
to 400.degree. C. at a rate of 5.degree. C./min, hold at 400.degree. C. 
for 15 min, and cool to room temperature at a rate of 3.degree. C./min. An 
amber film was obtained, which did not stress crack or dissolve when 
exposed to the aforementioned .gamma.-butyrolactone-cyclohexanone mixture. 
A control film of the copolymer, similarly heated under nitrogen but 
without the added of dicumyl peroxide, showed solvent induced stress 
cracking when exposed to the same solvent mixture.