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Methods for measuring the distribution of imperfections in semiconductors
382
WORLD
ABSTRACTS
ON
MICROELECTRONICS
AND
RELIABILITY
Methods for measuring the distribution of imperfections in semiconductors. H. AHLERS, Nachrichtentec. 19, No. 10 (1969), p. 385. (In G e r m a n . ) T h e f u n c t i o n a n d operation of s e m i c o n d u c t o r c o m p o n e n t s are m a i n l y based on a suitable a r r a n g e m e n t of imperfections in s e m i c o n d u c t o r crystals. It is therefore an i m p o r t a n t p r o b l e m of t h e t e c h n i q u e of m e a s u r e m e n t to k n o w the distribution of t h e s e imperfections. I n t h e p r e s e n t p a p e r m e t h o d s k n o w n a n d u s e d for t h e m e a s u r e m e n t are described a n d other possibilities are discussed. A v i e w of the reliability on solid tantalum capacitors. H. OKUDA,Y. NEGISHI a n d I. KAGEYAMA,N E C Res. Dev. Japan, No. 15, October (1969), p. 56. T h e failure rate of solid t a n t a l u m capacitors u s e d in the circuits of carrier t e l e p h o n e t r a n s m i s s i o n d u r i n g t h e course of 8 years in operation fields h a s been calculated to be five failures per 109 hr. 'Fhe failure rates of the capacitors in laboratory a n d operation fields have been c o m p a r e d . T h e laboratory test for failure rate was carried o u t d u r i n g 4½ years, a n d t h e result of 0"2 p e r cent p e r 103 h r was obtained. T h e failure rate in t h e fields d u r i n g the same period was calculated to be a b o u t two failures per 109 hr. T h e analysis of t h e results s h o w s that the failure rates in the laboratory a n d fields are in the ratio of 1000:1. T h e difference in t h e s e values d e p e n d s m a i n l y on the t e m p e r a t u r e a n d t h e voltage applied to t h e capacitors. It h a s been pointed o u t t h a t t h e recognition of the difference of failure in laboratory a n d operation field m i g h t contribute to clarify the discrepancy.
Failure creating and r e m o v i n g in solids. P. BARUCH. Onde Elect. 49, No. 10, N o v e m b e r (1969), p. 1092. ( I n French.) Properties of p u n c t u a l failures in solids are shortly reviewed creating at t h e r m o d y n a m i c stability, cinetic of v a n i s h i n g (recovery) r e m o v i n g by diffusion, creating by irradiation.
Determining m a x i m u m reliable load lines for power transistors. R. GREENBURG, Electron. Compon., D e c e m b e r (1969), p. 1447. O p e r a t i o n of p o w e r transistors w i t h i n their p o w e r - t e m p e r a t u r e ratings alone is n o t a sufficient safeguard to guarantee circuit reliability. A n additional consideration of t h e allowable collector-emitter voltage v. collector c u r r e n t m u s t be taken into account, otherwise a distinctive condition t e r m e d " s e c o n d a r y b r e a k d o w n " can occur. T o avoid this condition, it is necessary to m a i n t a i n the load line within safe voltage a n d c u r r e n t limits. Secondary b r e a k d o w n is a f u n c t i o n of t i m e in addition to voltage or c u r r e n t a n d reliable load line operation is specified by safe operating areas including time as a parameter.
Design of a reliable multiple contact for the coin telephone totalizer. J. P. ELLIS, I E E E Trans. Parts, Mater. Pekg P M P - 5 , No. 4, D e c e m b e r (1969), p. 161. T h e totalizer p e r f o r m s m a n y of t h e logic f u n c t i o n s in h a n d l i n g a call f r o m a public telephone set. It registers the d e n o m i n a t i o n of the coin deposited a n d pulses appropriate signals back to t h e central office by transferring four sets of contacts, w h i c h are operated by a falling coin. T h e e n e r g y available f r o m t h e coin is quite low, so contact force a n d cain rise of the switches m u s t be kept low. Satisfactory operation of the contacts is essential to reliable service f r o m t h e telephone. Public telephones are subjected to e x t r e m e e n v i r o n m e n t s , a n d early trials indicated contact c o n t a m i n a t i o n m i g h t cause t h e totalizer to fail to m e e t desired p e r f o r m a n c e levels. T h e contact design was reviewed f r o m three aspects: analysis of field failures, analytical investigation of design p a r a m e t e r s a n d laboratory testing to establish relative reliability figures. Considerations leading to t h e adoption of a b r u s h of four precious-metal wire contacts as t h e design to be u s e d in p r o d u c t i o n are s u m m a r i z e d .
High reliability resistors for use in s u b m e r g e d cable repeaters. S. OSBORNE, I E E Conf. Reliab. Electron., Conf. Publ. No. 60, 10-12 D e c e m b e r (1969), p. 35. T u r n i n g to t h e reliability r e q u i r e m e n t we f o u n d that in a certain cable a total 653 repeaters w o u l d be used, a n d each w o u l d contain 70 resistors of the n e w type, giving a total of 45,710. T h e lifetime envisaged was 20 years (160,000 hr), a n d therefore a r e q u i r e m e n t of s o m e 7"3 × 100 resistor h o u r s was involved. F o r a reasonable probability of success (i.e. a b o u t 90 per cent) t h e failure rate required is of the order of 10 -11 p e r hour, or three orders better t h a n t h e h i g h e s t level of reliability specified in the M I L . Established Reliability Specifications.
Specifications for electronic components of assessed quality: BS 9000. J. D. PLATT, I E E Conf. Reliab. Electron., Conf. Publ. No. 60, 10-12 D e c e m b e r (1969), p. 78. T h e BS 9000 s y s t e m is n o w in b e i n g a n d a n u m b e r of specifications have been issued. Very substantial progress has been m a d e in t h e appraisal of c o m p o n e n t m a n u facturers, test h o u s e s a n d stockists. A t r e m e n d o u s a m o u n t of work a n d goodwill h a s already gone into creating t h e s y s t e m a n d a l t h o u g h a lot remains to be done it m u s t surely rank as a specification s y s t e m u n i q u e t h r o u g h o u t t h e world. T h e final success of BS 9000 a n d its f u r t h e r evolution d e p e n d very m u c h on " t h e u s e r " . T h e r e is good reason to believe that engineers responsible for t h e design a n d m a n u f a c t u r e of reliable e q u i p m e n t n o w have a n e w tool to aid t h e m . If BS 9000 is to progress they m u s t u s e it.
The manufacture of highly reliable transistors for submarine cable systems. J. AUCHTERLONIE,D. BAKER, D. J. SARGENT a n d A. W. SEARLS, I E E Conf. Reliab. Electron., Conf. Publ. No. 60, 10-12 D e c e m b e r (1969), p. 103. A small p r o d u c t i o n u n i t h a s b e e n established at Dollis Hill to m a n u f a c t u r e t h e transistors required for use in s u b m a r i n e cable s y s t e m s w h e r e a g u a r a n t e e that less t h a n one in a total of 500 transistors will fail d u r i n g an operating life of 20 years is required. Failure is defined as a c h a n g e of -V10 per cent in c u r r e n t gain, a c h a n g e of greater t h a n 30 m V in a saturation voltage or an increase in t h e leakage c u r r e n t of either p - n j u n c t i o n to ~A.
WORLD
ABSTRACTS
ON
MICROELECTRONICS
AND
RELIABILITY
Methods for measuring the distribution of imperfections in semiconductors. H. AHLERS, Nachrichtentec. 19, No. 10 (1969), p. 385. (In G e r m a n . ) T h e f u n c t i o n a n d operation of s e m i c o n d u c t o r c o m p o n e n t s are m a i n l y based on a suitable a r r a n g e m e n t of imperfections in s e m i c o n d u c t o r crystals. It is therefore an i m p o r t a n t p r o b l e m of t h e t e c h n i q u e of m e a s u r e m e n t to k n o w the distribution of t h e s e imperfections. I n t h e p r e s e n t p a p e r m e t h o d s k n o w n a n d u s e d for t h e m e a s u r e m e n t are described a n d other possibilities are discussed. A v i e w of the reliability on solid tantalum capacitors. H. OKUDA,Y. NEGISHI a n d I. KAGEYAMA,N E C Res. Dev. Japan, No. 15, October (1969), p. 56. T h e failure rate of solid t a n t a l u m capacitors u s e d in the circuits of carrier t e l e p h o n e t r a n s m i s s i o n d u r i n g t h e course of 8 years in operation fields h a s been calculated to be five failures per 109 hr. 'Fhe failure rates of the capacitors in laboratory a n d operation fields have been c o m p a r e d . T h e laboratory test for failure rate was carried o u t d u r i n g 4½ years, a n d t h e result of 0"2 p e r cent p e r 103 h r was obtained. T h e failure rate in t h e fields d u r i n g the same period was calculated to be a b o u t two failures per 109 hr. T h e analysis of t h e results s h o w s that the failure rates in the laboratory a n d fields are in the ratio of 1000:1. T h e difference in t h e s e values d e p e n d s m a i n l y on the t e m p e r a t u r e a n d t h e voltage applied to t h e capacitors. It h a s been pointed o u t t h a t t h e recognition of the difference of failure in laboratory a n d operation field m i g h t contribute to clarify the discrepancy.
Failure creating and r e m o v i n g in solids. P. BARUCH. Onde Elect. 49, No. 10, N o v e m b e r (1969), p. 1092. ( I n French.) Properties of p u n c t u a l failures in solids are shortly reviewed creating at t h e r m o d y n a m i c stability, cinetic of v a n i s h i n g (recovery) r e m o v i n g by diffusion, creating by irradiation.
Determining m a x i m u m reliable load lines for power transistors. R. GREENBURG, Electron. Compon., D e c e m b e r (1969), p. 1447. O p e r a t i o n of p o w e r transistors w i t h i n their p o w e r - t e m p e r a t u r e ratings alone is n o t a sufficient safeguard to guarantee circuit reliability. A n additional consideration of t h e allowable collector-emitter voltage v. collector c u r r e n t m u s t be taken into account, otherwise a distinctive condition t e r m e d " s e c o n d a r y b r e a k d o w n " can occur. T o avoid this condition, it is necessary to m a i n t a i n the load line within safe voltage a n d c u r r e n t limits. Secondary b r e a k d o w n is a f u n c t i o n of t i m e in addition to voltage or c u r r e n t a n d reliable load line operation is specified by safe operating areas including time as a parameter.
Design of a reliable multiple contact for the coin telephone totalizer. J. P. ELLIS, I E E E Trans. Parts, Mater. Pekg P M P - 5 , No. 4, D e c e m b e r (1969), p. 161. T h e totalizer p e r f o r m s m a n y of t h e logic f u n c t i o n s in h a n d l i n g a call f r o m a public telephone set. It registers the d e n o m i n a t i o n of the coin deposited a n d pulses appropriate signals back to t h e central office by transferring four sets of contacts, w h i c h are operated by a falling coin. T h e e n e r g y available f r o m t h e coin is quite low, so contact force a n d cain rise of the switches m u s t be kept low. Satisfactory operation of the contacts is essential to reliable service f r o m t h e telephone. Public telephones are subjected to e x t r e m e e n v i r o n m e n t s , a n d early trials indicated contact c o n t a m i n a t i o n m i g h t cause t h e totalizer to fail to m e e t desired p e r f o r m a n c e levels. T h e contact design was reviewed f r o m three aspects: analysis of field failures, analytical investigation of design p a r a m e t e r s a n d laboratory testing to establish relative reliability figures. Considerations leading to t h e adoption of a b r u s h of four precious-metal wire contacts as t h e design to be u s e d in p r o d u c t i o n are s u m m a r i z e d .
High reliability resistors for use in s u b m e r g e d cable repeaters. S. OSBORNE, I E E Conf. Reliab. Electron., Conf. Publ. No. 60, 10-12 D e c e m b e r (1969), p. 35. T u r n i n g to t h e reliability r e q u i r e m e n t we f o u n d that in a certain cable a total 653 repeaters w o u l d be used, a n d each w o u l d contain 70 resistors of the n e w type, giving a total of 45,710. T h e lifetime envisaged was 20 years (160,000 hr), a n d therefore a r e q u i r e m e n t of s o m e 7"3 × 100 resistor h o u r s was involved. F o r a reasonable probability of success (i.e. a b o u t 90 per cent) t h e failure rate required is of the order of 10 -11 p e r hour, or three orders better t h a n t h e h i g h e s t level of reliability specified in the M I L . Established Reliability Specifications.
Specifications for electronic components of assessed quality: BS 9000. J. D. PLATT, I E E Conf. Reliab. Electron., Conf. Publ. No. 60, 10-12 D e c e m b e r (1969), p. 78. T h e BS 9000 s y s t e m is n o w in b e i n g a n d a n u m b e r of specifications have been issued. Very substantial progress has been m a d e in t h e appraisal of c o m p o n e n t m a n u facturers, test h o u s e s a n d stockists. A t r e m e n d o u s a m o u n t of work a n d goodwill h a s already gone into creating t h e s y s t e m a n d a l t h o u g h a lot remains to be done it m u s t surely rank as a specification s y s t e m u n i q u e t h r o u g h o u t t h e world. T h e final success of BS 9000 a n d its f u r t h e r evolution d e p e n d very m u c h on " t h e u s e r " . T h e r e is good reason to believe that engineers responsible for t h e design a n d m a n u f a c t u r e of reliable e q u i p m e n t n o w have a n e w tool to aid t h e m . If BS 9000 is to progress they m u s t u s e it.
The manufacture of highly reliable transistors for submarine cable systems. J. AUCHTERLONIE,D. BAKER, D. J. SARGENT a n d A. W. SEARLS, I E E Conf. Reliab. Electron., Conf. Publ. No. 60, 10-12 D e c e m b e r (1969), p. 103. A small p r o d u c t i o n u n i t h a s b e e n established at Dollis Hill to m a n u f a c t u r e t h e transistors required for use in s u b m a r i n e cable s y s t e m s w h e r e a g u a r a n t e e that less t h a n one in a total of 500 transistors will fail d u r i n g an operating life of 20 years is required. Failure is defined as a c h a n g e of -V10 per cent in c u r r e n t gain, a c h a n g e of greater t h a n 30 m V in a saturation voltage or an increase in t h e leakage c u r r e n t of either p - n j u n c t i o n to ~A.