The effects of stabilizing additives on the microstructure and properties of electroless copper deposits
- PDF / 5,586,036 Bytes
- 9 Pages / 612 x 783.28 pts Page_size
- 49 Downloads / 228 Views
E L E C T R O L E S S plating, a p r o c e s s in which m e t a l d e p o s i t i o n o c c u r s on c a t a l y t i c s u r f a c e s b y the c h e m i c a l r e d u c t i o n of m e t a l ions f r o m solution, is an a t t r a c t i v e and useful p r o c e s s in the m a n u f a c t u r e of p r i n t e d c i r c u i t s . R e c e n t d e v e l o p m e n t s of s e l e c t i v e p a t t e r n g e n e r a t i o n on s e n s i t i z e d s u b s t r a t e s b y u l t r a v i o l e t r a d i a tion 1 and s p e c i a l p r i n t i n g methods 2 have made it p o s s i b l e to b u i l d c o m p l e t e c i r c u i t s b y e l e c t r o l e s s p l a t i n g alone. The m a j o r a d v a n t a g e s of this p r o c e s s include deposit u n i f o r m i t y , and the p l a t i n g of u n c o n n e c t e d p a t t e r n s not p o s s i b l e b y c o n v e n t i o n a l e l e c t r o p l a t i n g t e c h n i q u e s . However, the effects of v a r i o u s additives upon e l e c t r o l e s s copper d e p o s i t s have yet to be fully e s t a b lished. The p r i m a r y d e v e l o p m e n t s in e l e c t r o l e s s copper s o l u t i o n s have b e e n d e s i g n e d to i n c r e a s e bath s t a b i l i t y . F i l t r a t i o n , agitation, and a d d i t i v e s such as cyanides, p o l y m e r s , methanol, and s u l f u r compounds have b e e n used to s t a b i l i z e e l e c t r o l e s s b a t h s , s'4,s'6,7 Bath i n s t a b i l i t y m a y be caused by p a r t i c u l a t e i m p u r i t y nuclei, the C a n n i z z a r o r e a c t i o n , 2HCHO + OH- ~
CHaOH + HCOO-
[1]
and the d i s p r o p o r t i o n a t i o n of Cu20. A c c o r d i n g to S a u b e s t r e , 8 Cu20 is p r o d u c e d b y the r e a c t i o n 2Cu ++ (complexing agent) + HCHO + 5OHCuaO + HCOO- + 3H20 + 2 (complexing agent)
[2] T. k AYCOCKis with Western Electric, Richmond, Va. 2323 l, N. C. HUIE is Member of Research Staff, Western Electric Engineering Research Center, Princeton, N. J. 08540, and G.KRAUSS is Professor, Department of Metallurgy and Materials Science, Lehigh University, Bethlehem, Pc. 18015. Manuscript submitted June 27, 1973. METALLURGICALTRANSACTIONS
and u n d e r g o e s d i s p r o p o r t i o n a t i o n a c c o r d i n g to the equation Cu20 + H20 + (complexing agent) - - Cu ~ + Cu ++ (complexing agent) + 2OH-
[3]
The copper p a r t i c l e s f o r m e d by this r e a c t i o n a r e d i s p e r s e d throughout the solution and s e r v e as d i s c r e t e c a t a l y t i c s i t e s for f u r t h e r plating. This is by f a r the m a j o r s o u r c e of bath i n s t a b i l i t y and effective s t a b i l i z ing agents e i t h e r f o r m c h e l a t e s with the Cu ยง ions, or r e d u c e the a c t i v i t y of the Cu ~ nuclei by b e h a v i n g as catalytic p o i s o n s . Cyanides and s u l f u r compounds a r e widely used s t a b i l i z i n g c h e l a t e s , w h e r e a s v a n a d i u m pentoxide and c e r t a i n p o l y m e r s r e d u c e the c a t a l y t i c b e h a v i o r of the Cu ~ p a r t i c
Data Loading...
