Honda CB160 Shop Manual page 97

5. 4 POWER SOURCE CIRCUIT
The rectifying performance of the silicon rectifier
is as shown in the figure and is conducted by the
silicon rectifying element (arrow marked section} coupled
to the terminal plate. The fact that the terminal plate
is large in comparison to the rectifying element is
due to the increase in heat dissipation and cooling,
in order to protect the rectifying element. The ter-
minal plates coupled to the rectifying elements are
arranged in shape in the rectifying circuits of various
systems.
{Refer to Fig. 5. 47)
In the silicon rectifier, as shown in the figure, high
melting point solder is used to position the silicon
rectifier body through a base plate on the cooling
plate (a). Additional high melting point solder {bl
and conduction terminal (fl are coupled by low melting
point solder
(cl
and wrapped by enclosure resin {h)
and a protective ring ( i
l.
A protective coating is
applied to the exterior surface.
(Refer to Fig. 5. 48}
The silicon rectifying element consists of three layers,
N
+,
N, and P
+,
N
+
consists of pure silicon with
an extremely small impurity (such as boron aluminum
and gallium} added. P
+
consists of one layer mixed
with an extremely small quantity of phosphorus. arsenic
and antimony.
Due to the electrical characteristic of the impurities
in each layer of
N
+
and P
+,
larger current flows
from N
+
to ,P
+.
Due to this, current flow from
P
+
to N
+
is difficult. This characteristic causes
rectifying performance.
(Refer to Fig . . 5. 49)
In order to remove the rectified current by utilizing
the rectifying performance of the silicon rectifying
element, both surfaces of the silicon rectifying element
are employed as electrodes. Hence,
if
the ambient
conditions of the silicon rectifying element are not
satisfactory, rectifier defects (reduced life, etc.} occur.
Therefore, both surfaces of the rectifying element
require protection, the electrode surface which is
wrapped by solder with a high melting paint and the
cut surface of the circumference which is covered by
a prote,:;tive coating for added performance.
Fig. 5. 47 Silicon rectifier
~'""NC
®
PROTEC TYE
PAINT
(0
FEED TERMINAL
CD
OUTER COVER
½
Cb)
SEALED RESIN
@
LOW MELTING
. POINT SOLDER
@
SILICON
RECTIFIER
@ @ @
HIGH MEL TING
COOLING PLATE BASE PLATE POINT SOLDER
Fig. 5. 48 Silicon rectifying element
+D--
N-c-
+ N - -
Fig.
5. 49
Rectifier of silcon wafer.
93