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The levels of miniaturization typically demanded by these end user groups place a premium
on every square millimeter of board space. Designers need to minimize the real estate devoted
to secondary over-current protection. Conventional wire fuses in SMD packages display a number
of strong features: they are robust, have high breaking capacity, are available in ratings up
to 10 A, and the technology also supports fast acting or time delay type fuse operation. They
can address a wide range of applications, including over-current protection of power lines. On
the other hand, package sizes are not likely to reduce below the industrystandard 2410 SMT
outline. In consumer applications where low rated currents and breaking capacities are
required, <a href="https://www.conquer-fuse.com/chip-fuse/">Chip Fuse</a>s are emerging to
satisfy designers’ demands for the next level of component miniaturization.
</p>
<p>
Chip fuses feature a conductive fuse element that is typically deposited as a thick-film,
electroplated, or thin-film layer onto a ceramic substrate. Using these basic technologies,
secondary over-current protection is able to migrate into smaller SMT packages including 1206,
0603, and even 0402. However, two further imperatives are the need for long-term stability of
the fusing characteristic and a low unit price to enable a cost-effective solution. Stability
is heavily dependent on the accuracy of the fabrication technique used to create the fuse
element. Traditionally, a thick-film element for a chip fuse is deposited using a screen
printing process, while most fuse elements are electroplated. Both of these techniques enable
quite accurate control over the dimensions of the fuse element in order to achieve the desired
fusing characteristic. However, the homogeneous crystal structure of the metal layer has an
important influence over the long-term stability, due to aging factors such as power
dissipation or external high temperatures in combination with thermal cycles. To
simultaneously improve control over the dimensions and crystal structure of the fuse element,
Vishay Beyschlag MFU-series chip fuses are created using a thin film sputtering process in
place of screen printing or electro-plating.
</p>
<p>
This process leverages precision chip resistor manufacturing knowledge and assembly
capacity. In addition, a special protective coating comprising layers of glass and epoxy
lacquer also now raises the capability of chip fuses to withstand harsh thermal shocks and
wide-ranging humidity requirements. Benchmark tests on MFU series chip fuses demonstrate
superior performance in this respect due to this special protective system.
</p>
<p>
<br/>
</p>
<p>
The thermally activated fuse is the oldest circuit protection device and is still in
widespread use. It is well understood, reliable, consistent, and approved by regulatory
standards. However, with end products increasing in complexity and shrinking in size,
designers need an alternative to the user-replaceable fuse and fuse holder in order to reduce
the form factor, simplify assembly, improve ruggedness, and further enhance safety.
</p>
<p>
Instead, designers can use surface mount devices (SMDs) without a performance compromise.
<a href="https://www.conquer-fuse.com/smd-mount-fuse/">SMD- Mount Fuse</a>s employ diverse
technologies to provide thermal-based fusing along with the full range of necessary fuse
characteristics, such as fast acting and slow blow.
</p>
<p>
<br/>
</p>
<p>
<strong>The Basics: How Does a Fuse Work?</strong>
</p>
<p>
A fuse is a simple and highly effective way to protect a device from dangerous levels of
current:
</p>
<ul class=" list-paddingleft-2">
<li>
<p>
Current flowing through a conductor’s nonzero resistance leads to power
dissipation.
</p>
</li>
<li>
<p>
Power is dissipated in the form of heat.
</p>
</li>
<li>
<p>
Heat raises the temperature of the conductor.
</p>
</li>
<li>
<p>
If the combination of current amplitude and duration is sufficient to raise the
temperature above the fuse’s melting point, the fuse becomes an open circuit and current flow
ceases.
</p>
</li>
</ul>
<p>
Though the fundamental operation of an <a href="https://www.conquer-fuse.com/axial-lead-
cartridge-fuse/">Axial Lead & Cartridge Fuse</a> is not complicated, there are subtle
points to keep in mind. The rest of this article will help you to understand some important
details related to the behavior and use of fuses.
</p>
<p>
</p>
<p>
<strong>How a Fuse Is Tripped: Heat, Not Current</strong>
</p>
<p>
A fuse is not tripped directly by current; rather, the current creates heat, and heat
trips the fuse. This is actually a rather important distinction because it means that the <a
href="https://www.conquer-fuse.com/automotive-fuse/">Automotive Fuse</a> operation is
influenced by ambient temperature and by the temporal characteristics of the current.
</p>
<p>
The specified current rating of a fuse is relevant only to a specific ambient temperature
(usually, or maybe always, 25°C), and consequently you need to adjust your fuse selection if
you’re designing a device that will operate outdoors in, say, Antarctica or Death Valley. The
following plot shows how ambient temperature affects the actual current rating—relative to
the nominal 25°C current rating—of three types of fuses.
</p>
<p>
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