Application Note

Application Note
Vishay General Semiconductor
SUPERECTIFIER® Design Brings New Level of
Reliability to Surface Mount Components
By Joseph M. Beck, Senior Applications Engineer
Surface Mount technology is here to stay. After years of
plodding through cautious experimentation, many
manufacturers now have fully automated production lines in
place. These production lines place circuit components at
speeds that until recently would have been unthinkable.
Finally being realized are the benefits of what was once
considered a “Voo Doo” manufacturing technology.
Component manufacturers have learned a great deal over
the past several years as well. Initially most surface mount
components were nothing more than retrofit, lead formed
versions of their conventional leaded, through-hole
counterparts. For most manufacturers this was the quickest
and least costly method of “developing” a line of surface
mountable components.
It was soon discovered, however, that this approach to
component assembly would be unacceptable. Surface
mount technology placed new demands upon circuit
components. Electrically, the same power was being
required from smaller and smaller packages. Package
geometries and dimensions became critical in relation to pick
and place equipment and circuit board mounting. In addition,
the construction of these devices needed to be such that they
would suffer no ill effects when subjected to the rigors of the
new assembly environment that surface mount technology
presented. Encountered in this environment was extremely
high-speed pick and place equipment, component adhesive
attachment, immersion in molten solder and rapid
temperature changes associated with reflow soldering
processes. All this meant that component manufacturers
would have to re-think their approach to device fabrication.
Yes, components needed to be smaller; but they also
needed to be more reliable.
At Vishay General Semiconductor, the development of new
surface mount components is not something that is taken
lightly. It is realized that in order to produce a truly reliable
surface mount product one must first consider all relevant
aspects of the technology. Only when this process has been
completed can a product be developed which is surface
mountable, and inherently reliable.
Solderable
Copper Ends
Cavity-Free
Opague
Glass-Passivated
Junction
Solderable
Copper Ends
Solid Brazing, Low Resistance,
Excellent Surge Capabilities
(Brazed-Temperature) 600 °C
Figure 1. SUPERECTIFIER Construction
The construction of the SUPERECTIFIER does not internally
utilize any soft solders. All interconnects are accomplished
by the use of a high temperature brazing process (600 °C).
Hence, any chances of solder void occurrence or internal
solder reflow during circuit board processing are eliminated.
In addition, the silicon rectifier junction is completely
encapsulated by a cavity-free glass. This glass
encapsulation ensures that the rectifier junction is
hermetically isolated from humidity and other harmful
environmental intrusions.
The resultant sub-assembly could be considered to be a fully
functional surface mount rectifier. In fact, many component
manufacturers offer MELF devices which have this
appearance; namely, an oblong glass bead with two
protruding metal end terminations. However, in order that the
device have a uniform shape, the General Semiconductor
sub-assembly is over molded with epoxy. The result is a
smooth, perfectly cylindrical package.
TWO SIZES
Two different size SUPERECTIFIER MELF packages are
available. Vishay General Semiconductor designation GL34
and GL41 are for 0.5 A and 1.0 A rectifier types, respectively.
JEDEC mechanical specifications DO-213AA and
DO-213AB detail the dimensions of the GL34 and GL41,
respectively. Figure 2 gives these package dimensions.
SURFACE MOUNT SUPERECTIFIER®
Vishay General Semiconductor manufactures surface mount
rectifiers in the popular MELF (metalized electro-face)
package style. These devices, denoted as SUPERECTIFIERS,
are available with a wide variety of electrical characteristics.
The main difference, however, between these rectifiers and
other MELF style devices lies in the area of device
construction. Figure 1 shows the unique construction
employed in the manufacture of the SUPERECTIFIER.
www.vishay.com
1474
UL Recognized
Flame Retardant
Molding
Compound
(UL 94-V0)
Completely
Encapsulated
Brazed Construction
B
C
A
Figure 2. Dimensional Outline
DIMENSIONAL OUTLINE in inches
DIMENSION
A
B
C
GL34 DO-213AA
MIN.
MAX.
0.130
0.146
0.063
0.067
0.016
0.022
For technical questions within your region, please contact:
[email protected], [email protected], [email protected]
GL41 DO-213AB
MIN.
MAX.
0.189
0.205
0.094
0.105
0.016
0.022
Document Number: 88841
Revision: 23-Jul-08
Application Note
Vishay General Semiconductor
MANUFACTURING CONSIDERATIONS
Pick and Place-Surface mount SUPERECTIFIERS are supplied
on tape and reel in accordance with JEDEC standard
RS-481A. Removal of the devices from the embossed carrier
tape is easily accomplished by all vacuum pick-up
mechanisms which utilize a compliant tip. The compliant tip
will form a tight seal around the cylindrical MELF design once
contact with the device has been made. This is not always
the case, however, when MELF devices with a non-uniform
package outline are used. Figure 3 shows two such MELF
outlines. Figure 3A is a device with a concave package
outline. This type of package is difficult to consistently
remove from the carrier tape as the exact position of pick-up
on the component body is critical. Figure 3B is that of the
most common form of MELF packaging. This type of
construction utilizes a nontransparent glass body which is
often characterized by pitting and surface irregularities. The
irregularities make it difficult for a vacuum pick-up to form a
tight seal around the device body. The result is that
components are often dropped onto the production room
floor instead of being placed on the targeted circuit
board.Vishay General Semiconductor solves these
problems with a smooth surface and perfectly cylindrical
package outline.
Pick-Up
Pick-Up
• Component adhesive attachment allows the package to
shift slightly from its original placement position prior to
adhesive curing. In addition, most adhesives tend to
spread during the curing process which also may allow
package
misalignment. The
geometry
of
the
recommended pad layouts will tend to minimize such
movements.This assumes, of course, that the package
was originally positioned correctly.
• During reflow soldering, solder surface tension can have a
significant effect on the movement and final position of
components in relations to their bonding pads. The
recommended pad layouts will actually make use of the
solder surfacetensions to bring MELF devices into
alignment with the two bonding pad land areas.
This means that MELF devices which are initially placed in
slight misalignment on their bonding pads will reposition
themselves during solder reflow until a position of alignment
is reached.
Soldering - Surface mount SUPERECTIFIERS are capable of
withstanding all present forms of wave and reflow soldering.
The following guidelines should be followed, however, in
order to ensure overall package integrity:
• GL34-Maximum temperature at device and terminations
not to exceed 400 °C for 5 s. Complete device submersible
temperature not to exceed 260 °C for 10 s in solder bath.
• GL41-Maximum temperature at device end terminations
not to exceed 450 °C for 5 s. Complete device submersible
temperature not to exceed 265 °C for 10 s in solder bath.
A
B
Figure 3. Non-Uniform Melf Outlines
Bonding Pads - The geometries and dimensions of bonding
pads are critical to the proper mounting, soldering and
overall performance of all surface mount components.
Figure 4 gives the recommended pad layouts for GL34 and
GL41 MELF outlines. Use of these pad layouts will be
primary assistance in the following three areas:
• Surface mount technology by nature dictates that smaller
component packages dissipate the same power as their
larger through-hole counterparts. Hence, adequate
bonding pad land area is required in order to aid the
component package in the dissipation of this power.The
recommended pad layouts provide the needed land area
for GL34 and GL41 devices to operate safely at their
maximum ratings.
Document Number: 88841
Revision: 23-Jul-08
Vishay
General
Semiconductor’s
surface
mount
SUPERECTIFIERS combine superb electrical performance with
unmatched levels of reliability. The construction of the
SUPERECTIFIER virtually eliminates all problems associated
with high-speed pick and place of MELF components. In
addition, SUPERECTIFIER construction ensures that
performance and reliability are never compromised when the
device is subjected to the demands of surface mount
assembly techniques or when other seemingly harmful
environments are encountered. Quite simply, no other
surface mount rectifier comes close to offering all the
advantages of the SUPERECTIFIER MELF.
All surface mount components are small and save space.
However, performance and reliability should never be
considered necessary trade-offs in order to utilize surface
mount technology. Use of Vishay General Semiconductor
surface mount SUPERECTIFIERS requires no such sacrifices;
no trade-offs.
For technical questions within your region, please contact:
[email protected], [email protected], [email protected]
www.vishay.com
1475
Application Note
Vishay General Semiconductor
A
F-Slot Width
B
Optimum Pad Size
C
D
E
G
I
Optimum Pad Size
For Large Buss Attachement
Use a Solder Mask to
Reduce Effective Pad Size
H
Where Possible Make
Connecting Circuitry
Smaller than the
Component Pads to
Reduce Flashing or
Miscueing
Figure 4. Recommended Pad Layout
RECOMMENDED PAD LAYOUT in inches
DIMENSION
GL34
GL41
A
0.069
0.100
B
0.63
0.100
C
0.69
0.100
D
0.138
0.200
E
0.207
0.300
F
0.016
0.025
G
0.138
0.200
H
0.035 to 0.80
0.050 to 0.125
I
0.048 min.
0.075 min.
PART NUMBER
CURRENT (A)
VOLTAGE (V)
trr (ns)
PACKAGING
0.5
50 to 600
-
GL34
GENERAL PURPOSE
GL34-J
1N6478-84
1.0
50 to 1000
-
GL41
GL41A-Y
1.0
50 to 1600
-
GL41
FAST RECOVERY
RGL34A-J
0.5
50 to 600
150 to 250
GL34
RGL41A-M
1.0
50 to 1000
150 to 500
GL41
EGL34A-G
0.5
50 to 400
50.0
GL34
EGL41A-G
1.0
50 to 400
50.0
GL41
ULTRA FAST RECOVERY
www.vishay.com
1476
For technical questions within your region, please contact:
[email protected], [email protected], [email protected]
Document Number: 88841
Revision: 23-Jul-08
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