Resistor Downsizing - PCB Space Saving - High Reliability

22. März 2022, 8:00 Uhr | Simone Schiller
Resistor Downsizing - PCB Space Saving - High Reliability

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.

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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.

Ersatz von größeren Chip-Widerständen durch kleinere aus den Baureihen WK73 und  SG73

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.

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 requested.

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.

The newest updated datasheets of these special flat chip resistors can always be found on the supplier website of KOA Corporation.

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KOA Europe GmbH