(SANITIZED)UNCLASSIFIED HUNGARIAN PAPER ON INFLUENCE OF NON-UNIFORM BASE WIDTH ON TRANSISTOR FAILURE(SANITIZED)

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A018600710001-7
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 4
• Document Creation Date: December 22, 2016
• Document Release Date: January 12, 2012
• Sequence Number: 1
• Publication Date: October 29, 1962
• Content Type: REPORT

Declassified in Part - Sanitized Copy Approved for Release 2012/01/12 : CIA-RDP80T00246AO18600710001-7
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Declassified in Part - Sanitized Copy Approved for Release 2012/01/12 : CIA-RDP80T00246AO18600710001-7
 Declassified in Part - Sanitized Copy Approved for Release 2012/01/12 : CIA-RDP80T00246AO18600710001-7
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M. Kocsis
`Industrial Research Institute for Telecommunication Technique.
width. The computations have shown, that only a few/usecs are neec.
reach a temperature of more hundred centigrades in the minimum width base
region. ;era; -
To characterize the transistors from the point of view of thermal stabilil
the ratio= of equivalent base width ?which may be computed from the cutoff
frequency of the common--base-connected transistor) to minimum b;i , "ridth
wase introduced. The minimum base width may be determined by mer., r r.
ance; with the aurnor's.;o,DservaTiuns - .u 611@ LAU[1-UU11v4111 VCL:.11j, YYia 1.
the, t,7ransistor.
With a. =transistor base width considerably.reduced ata certain.
current density will rise locally owing to an.'increase in hole der,--,.jr.
The elevated current' density results in a growth of temperature at the
corresponding emitter and collector points, respectively. The overheating
. .
of the emitter points gives rise to the increase -of .the: hole density in
the minimum--base-width region. Thus the gradient of hole density is urthe
increased, resulting in an even higher current density.-It is obvious that
this process is regenerative, involving a thermal feedback loop,
The effects desoribed are of importance especially during the
times, because a considerable momentary power is dissipated 'duy':.rr
transition period in the transistor. If the transistor is drive..
current generator the emitter current is concentrated to-, ar^d t, 3f
minimum base widti. If no provisions are made to limit thou oolle
current, an alloying process starts, and in the minimum-width bas.
a p-type channel develops, resulting in a lasting collector-emitter sI.ort.
A mathematical analysis has been carried out in terms of a unidimensioned
model. It was'assumed that base width of the transistor is reduced con-
siderably but at one spot. In one concrete case the temperature hays been
determined numerically in a minimum-width base region as a fu-not.'.. n of
v time. The minimum base width was assumed to be 1/5 of the nomina: b
"Myter1ous"failures are often-encountered, when transistors are 'rerated
in .ew aching oirouA.t+, in spite of ,provisions made to prevent, av :i load.
Collector--to-'emitter shorts may-suddenly develop although ;.re- em _'. 3r-base
and collect or-base diodes are still good. This phenomenon may be ..x.-lained
by the supposition .,that. 'inside the transistor a p-type channel interconneo
ing the emitter and the collector appears in-the n-type base region, 'these
considerations hold for p-n-p transistors/.) .
The narrow channels, causing shorts, have been microscopically dc,;ected
`inside the damaged transistors.
Thw 'nhsa.ringi is the result of localized 'heating phenomena,. due - in F .J -.rd-
the punch-through and avalanche--breakdown voltage.
The value, characteristic for the non-uniformity of transistor '?ase width
may be expressed as follows: We
f /V!e = equivalent base width, wm = minimum base width.
Transistors of the same type.,having different 11 -factors, have been
operated in pulse circuits and the case temperature has been measured.
As a result of increasing the average power across the transistor, the
case .einperature has been successively elevated. In each case the
'temperature has been determined, at which thermal instability of the
transistor took p]Lace. The transistor was preserved from damag? means
Declassified in Part - Sanitized Copy Approved for Release 2012/01/12 CIA-RDP80T00246AO18600710001-7
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Declassified in Part - Sanitized Copy Approved for Release 2012/01/12 : CIA-RDP80T00246A018600710001-7
'
o ep on a
ti this static, o.pera.tin&,_point for a ~Ijong -time; -stably at 85 C.t',
some transistors snowed a behaviour similar to that of gaseous discharge
tube'. They, pos3.esse.d?.~ _ 4.2, i.ee an. extremely high non-uniformity of
The results of the measurements are shown in the figure.
'Subsequent' to" the, u~ se' examination's alb .t.he transistors have been placed
i"n thermostats and heated up to 85 C.''Do'volta es'
equal to those , r?nen'
,
_i in pulse operation-during "off" condition, have been applied, to the>
!)",terminals' of the, transistors. The :trabs,ister s; run without
exc ti t
Conclusionrs
'The examinations reported were carried 'out'on _alloy type. fun'ction',
transistors. -
The factor which, can be measured without. damaging.,ther,trans.istor se: is
to be '.n important characteristic. of 'tran_sistor' reliability. The "mys tari-
.11
ous" o`auses"of t r a ' ~sidtbr'~failure, ~e etofore inexplioa'ble, m a y be' under-
etoody~!apart from st 'faoe phenomena o ba I of the above 4 4 1 4 0 ,
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