Fluorinated copolyimides for microelectronics applications - Polyimides and Other High Temperature Polymers - page 449

PI-1(ODPA/ODA/TFmDA), PI-2(ODPA/ODA/TFDA), PI-3(ODPA/ODA
/TFB), PI-4(ODPA/ODA/TFPA), PI-5(ODPA/ODA/TFPB), PI-6(ODPA/ODA
/TFPPA) and PI-7(ODPA/ODA/DATF) were prepared at mole ratios of
ODPA:ODA: fluorinated diamine = 1:0.5:0.5 in the same manner as described
above.

3. RESULTS AND DISCUSSION

3.1. Copolymer synthesis
Copolyimides were prepared by thermal imidization of copoly(amic acid)s, which
were prepared by reacting ODPA with ODA and one of the fluorine-containing
diamines. The molar ratio of ODPA:ODA: diamine was 1:0.5:0.5, which ensured
that the polycondensation reaction proceeded completely to afford high molecular
weight copolymers. Scheme 1 shows the synthesis pathway of the copolyimides,
in which the trifluoromethyl groups are located at different positions in polymer
chains, either in the main chain (PI-1) or in the side phenyl group (PI-2 to PI-8).
The inherent viscosity of the copoly(amic acid)s ranged between 0.74 and 1.25
dL/g (Table 1), which was determined by Ubbelohde-viscometer with 0.5 g.dL -1
NMP solution at 30°C. It can be seen that PAA-6 showed the highest inherent
viscosity (1.25) and PAA-7 showed the lowest value (0.74), implying that the
polymer based on TFPPA possesses higher molecular weight than that derived
from DATF. Strong and flexible films could be prepared by casting copoly(amic
acid) solutions, followed by thermally baking using the following sequence:

Table 1.
Inherent viscosity of PAAs and film properties of copolyimides

T g ( o C) T d ( o C) a T 5% b

( o C)

T 10% b
( o C)

Rw c
(%)

W u d
(%)

PAA PI

η inh
(dL/g)

T d1 a d2 a

DSC DMA

PAA-1 1.21 PI-1 271.3 255.3 648.5 - 551.2 608.9 54 0.39
PAA-2 0.86 PI-2 255.9 240.5 456.2 596.1 493.1 533.7 55 0.56
PAA-3 1.02 PI-3 274.1 258.0 441.1 625.9 476.9 523.1 49 0.58
PAA-4 0.89 PI-4 248.5 233.1 463.3 663.6 504.0 578.2 58 0.52
PAA-5 0.96 PI-5 264.6 258.5 443.0 640.6 478.5 538.9 55 0.61
PAA-6 1.25 PI-6 232.4 215.1 598.7 - 534.1 583.6 46 0.42
PAA-7 0.74 PI-7 271.7 256.7 481.0 651.4 542.0 606.1 61 0.44
PAA-8 1.17 PI-8 288.9 273.6 590.0 - 579.9 621.0 60 0.46
a) T d : Onset decomposition temperature; T d1 : The first decomposition temperature; T d2 :
The second decomposition temperature
b) T 5% , T 10% : Temperatures for 5% and 10% weight loss, respectively
c) Residual weight retention (Rw %) at 700 o C
d) W u : Water uptake (%)