The trend in commodity chip resistor sizes is to go smaller. Just like semiconductors, the smaller the resistor the more you can get from a single ceramic sheet during manufacturing. However, it is surprising that when some circuit designs are updated the resistors are just simply transferred to the new design.
The table below shows the trend in resistor sizes and shows that 0201 and 0402 sizes are now the most popular.
What the above means is that as the market continues to downsize, the availability for the higher case sizes of 0603 – 1206 will become more restricted in the future. To support this market trend, KOA is heavily investing in case sizes 0402 and below to support the conversion to smaller sizes. It is envisaged that the pricing trend for the larger chip sizes will be adjusted accordingly to support the changes in the market. While many designs can simply move to the smaller sizes in the next design iteration, some applications need the larger chip sizes due to higher power dissipation.
So, what to do if you need higher power, but want to migrate away from the larger chip sizes and future proof a design?
Replacing larger chip resistors with parts from the WK73 and SG73 ranges.
For higher power requirements there are two possible solutions: Wide terminal or pulse tolerant resistors.
Wide terminal resistors have an excellent power to size ratio as they dissipate much of their heat via the wide terminals on the device.
Pulse tolerant resistors are designed to have as much film material on the ceramic substrate as possible so while being able to handle higher pulse loads than standard resistors of similar size, their 'reduced hotspot design' also means that they can dissipate more power in the steady state.
The above graphic shows that a typical 0805 or 1206 resistor can be designed out in favour of a smaller pulse tolerant SG73 in an 0402 size, or a WK73 wide terminal part in 0204 size.
For the 0603 size it's a similar story except in many instances the standard 0603 part can be replaced by the standard 0402 device.
SG73P – Pulse proof high power thick film chip resistors
KOA’s SG73P -series has approx. 7 times pulse handling capability compared to standard flat chip resistors. Due to this outstanding pulse load capability this series is suitable for protection of electronic circuits against extreme pulses and surges good examples of which are IO lines and gate drive resistors. These devices are ideal for automotive, power control and smart meter applications.
Due to the special resistance trimming, it also allows a higher power rating than a standard chip resistor of the same size. An SG73P device can be dropped onto the pads of a similar sized conventional part, thus increasing the power capability. This retro fitting can be very useful if an existing design needs a higher power resistor as this can be done without changing the PCB layout. Equally in a new design a smaller SG73 device can be used saving valuable PCB space.
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WK73R – Wide terminal high power thick film chip resistors
High reliability and enhanced terminal strength are essential in many power applications. KOA’s WK73R -series has a 90° rotated design and this offers several advantages compared to standard resistor footprints. The 0612-chip size allows 6 x power rating compared to standard 1206 parts. This saves board space and is possible due to the improved heat dissipation via the solder joints. The large terminals also enhance terminal strength and the smaller distance between the terminals reduces expansion stress increasing the solder joint reliability. Finally, the inner resistive pattern is designed to minimize hotspots. These benefits combined, result in superior reliability compared to standard flat chip resistors in power applications.
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RN73H and RN73R – Highest precision metal film flat chip resistors with excellent long-term stability
KOA offers 2 families of thin film resistors with a T.C.R. down to 5 ppm/°C and a tolerance as low as 0.05%.
The RN73R -series is ideal for high-precision circuits in industrial and measuring applications. This series provides improved electrolytic corrosion resistance and higher stability compared to KOA’s legacy RN73 series which it replaces. The RN73R also has an ambient temperature rating of +85°C, as well as a moisture tolerance of 0.25% at 85% RH for 1000 hours at +85°C.
The RN73H -series is ideal for high precision circuits for automotive and aerospace applications. These thin film resistors have excellent moisture resistance due to an additional inner protective layer. The RN73H has a moisture resistance of 0.1% at 85 % RH for 1000 hours at +85°C.
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RS73 - High precision thick film resistors 25ppm, 0.1% with excellent long-term stability
The RS73 -series combines the accuracy of thin film with the ruggedness of thick film. With a T.C.R. down to ±25ppm and a tolerance as low as ±0.1%, the new RS73-series from KOA is ideal for precision designs such as high-accuracy sensing or voltage detection circuits in automotive, industrial, and measuring applications.
These new thick film resistors can also be used to replace thin film parts in applications where ESD sensibility is an issue, or higher (pulse) power is needed. The use of these parts in place of thin film devices, can reduce the need for protection components, such as varistors, thus reducing both component count and cost. The RS73 series also features a higher power rating per size and better short time overload performance than thin film.
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SG73P Series
WK73R – Wide terminal high power thick film chip resistors
RN73H Series
RN73R Series
RS73 Series
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