Research and Development of a New Type of Crystal - The FC Cut

Abstract

a r e : 1. 2. .The a d v a n t a g e s o f t h e FC t y p e c r y s t a l T e m p e r a t u r e b e h a v i o r c h a r a c t e r i s t i c s s u p e r i o r t o an AT c r y s t a l a t e l e v a t e d e x a m p l e , t h e " f l a t n e s s " o f t h e t u r n i n g t e m p e r a t u r e s a n d t u r n i n g p o i n t s . F o r p o i n t o f a n FC a t 80° C is e q u i v a l e n t t o t h e " f l a t n e s s " o f t h e t u r n i n g p o i n t of an AT i n the r e g i o n o f 40° C. A h i g h e r i n t r i n s i c Q , by some 25 t o 30 % o v e r a comparable AT d e s i g n i n h i g h -r e l i a b i l i t y a p p l i c a t i o n s . An a p p a r e n t " f a s t warm up" because of e x t r e m e l y s m a l l t e m p e r a t u r e d e v i a t i o n t u r n i n g p o i n t . F o r e x a m p l e , a t a from room t e m p e r a t u r e t o a n e l e v a t e d t u r n i n g p o i n t o f 80° C , the t o t a l d e v i a t i o n d o e s n o t e x c e e d 3 PPM from room temperature, compared with 25 PPM f o r a n AT. The p a p e r p r e s e n t s d a t a o n , and d i s c u s s e s , t h e f o l l o w i n g : 1. A h i s t o r y o f FC development. 2 . G e n e r a l o r i e n t a t i o n i n f o r m a t i o n . 3 . The first, s e c o n d , a n d t h i r d o r d e r t e m p e r a t u r e c o e f f i c i e n t s o b t a i n e d t o d a t e . 4 . P r o b l e m e n c o u n t e r e d i n the d e s i g n , m a n u f a c t u r e a n d u s e o f t h e s e c r y s t a l s . Key Word;; FC c r y s t a l , f a s t warm-up, h i g h Q c r y s t a h i g h e r temperature o p e r a t i o n , h i g h -r e l i a b i l i t y c r y s t a l , FC crystal e v a l u a t i o n . I n t r o d u c t i o n F o r s e v e r a l s p e c i f i c a p p l i c a t i o n s , c r y s t a l s w i t h improved frequency-temperature c o e f f i c i e n t s were needed t o advance the " S t a t e -o f -t h e -A r t " . The f i r s t o f t h e s e n e e d s were f o r a h i g h p r e c i s i o n c r y s t a l t o be o p e r a t e d a t h i g h e l e v a t e d t e m p e r a t u r e s , s u c h as 900 C b u t w i t h a f l a t t e r t u r n o v e r r e g i o n . Another need w a s f o r a c r y s t a l t o meet TCXO t e m p e r a t u r e r a n g e s t h a t were n o t c o m p a t i b l e w i t h t h e optimum t e m p e r a t u r e -f r e q u e n c y r a n g e of an AT c u t c r y s t a l . O t h e r n e e d s were f o r f a s t warm-up d e v i c e s , a n d d e v i c e s w i t h t o t a l u n i t t e m p e r a t u r e c o e f f i c i e n t s o f 5 x 10-13 p e r C Maximum a n d e x h i b i t i n g v e r y g o o d a g e i n g r e q u i r e m e n t s . A s u p e r i o r s u b s t i t u t e t o t h e AT c u t c r y s t a l was c l e a r l y n e e d e d a n d i n F e b r u a r y o f 1 9 6 7 , p r a c t i c a l r e s e a r c h w a s i n i t i a t e d . T h i s r e s e a r c h was s p o n s o r e d e n t i r e l y by F r e q u e n c y E l e c t r o n i c s . Improved Crystals "The FC C u t " The r e s e a r c h was begun by f a b r i c a t i n g d o u b l e o r i e n t ...