An anti surge chip resistor absorbs short, high-energy pulses that would destroy a
standard thick film part of the same size. The element is thicker and laid out to spread
current, so peak energy does not concentrate in one narrow track. Use one wherever a
resistor sits in a surge path, not just where average power is high.
What is an anti-surge chip resistor?
It is a thick film chip resistor with a modified element geometry and a heavier film, made
to survive energy delivered in microseconds rather than seconds. Continuous power rating is
only part of what it buys you. The real specification is pulse withstanding: how much
energy the part takes in a single short event without shifting value or opening.
The distinction matters because the two failure modes are different. Continuous overload
fails a resistor thermally — the whole element heats until the film or the substrate gives
way. A surge fails it locally. Current crowds into the narrowest, highest-current-density
part of the track, and that spot vaporises while the rest of the element is still cold.
Anti-surge construction attacks the second mechanism. A thicker film carries more current
per unit width, and a shorter, wider element geometry lowers peak current density. The
resistor ends up with more surge capability and, usually, a higher continuous rating as a
side effect.
Walsin Technology (Walsin) builds three families around this. Our catalogue extract holds
17,180 anti-surge and power-surge parts in total.
When will a standard thick film chip resistor fail under surge?
Sooner than the power rating suggests. A general purpose 0805 rated 1/8 W has a thin, laser
trimmed element with a deliberate current concentration at the trim notch. A single
kilovolt-class pulse through that notch can shift the resistance permanently or open the
part, even though average dissipation never approached 1/8 W.
The circuits where this bites are predictable. Series resistors on mains-referenced
discharge paths. Bleeder resistors across X capacitors. Gate resistors on a switching FET
that sees avalanche. Input series resistance ahead of an ESD or surge clamp. Current
limiting on a hot-swap connector. Anywhere an inductive load collapses into a resistive
path.
In all of these the energy arrives in microseconds. IEC 61000-4-5 surge testing uses an
8/20 µs current waveform; telecom work often uses 10/1000 µs. The resistor absorbs the whole
joule in that window, and the substrate has no time to conduct it away.
Why is a 0603 anti-surge part rated 1/4 W when an 0805 general purpose part is 1/8 W?
Because the film and the element geometry, not the footprint, set the rating. A 0603
anti-surge part with a heavier element dissipates more than a larger 0805 general purpose
part with a thin trimmed one. The anti-surge part is physically smaller and rated at twice
the power. That inversion is the whole point of the construction.
Here are eight real Walsin parts from our extract. Four are 0603 surge parts, four are
0805 general purpose parts at the same nominal resistance range. The reference is
MK06S1R00FTL. The right-hand column states field by field what matches and what does not.
| Walsin part number | Series | Case size | Resistance | Tolerance | TCR (ppm/°C) | Rated power | Match / mismatch vs MK06S1R00FTL |
|---|---|---|---|---|---|---|---|
| MK06S1R00FTL | Thick Flim Power Surge Chip Resistor (Automotive) | 0603 (1608) | 1.00 Ω | ±1% | ≤ ±200 | 1/4 W | reference part |
| MK06S1R02FTL | Thick Flim Power Surge Chip Resistor (Automotive) | 0603 (1608) | 1.02 Ω | ±1% | ≤ ±200 | 1/4 W | match: series, case size, tolerance, TCR, power, Sn-base lead-free termination · mismatch: 1.02 Ω not 1.00 Ω |
| MK06S1R10FTL | Thick Flim Power Surge Chip Resistor (Automotive) | 0603 (1608) | 1.10 Ω | ±1% | ≤ ±200 | 1/4 W | match: series, case size, tolerance, TCR, power, termination · mismatch: 1.10 Ω not 1.00 Ω |
| MK06S1R18FTL | Thick Flim Power Surge Chip Resistor (Automotive) | 0603 (1608) | 1.18 Ω | ±1% | ≤ ±200 | 1/4 W | match: series, case size, tolerance, TCR, power, termination · mismatch: 1.18 Ω not 1.00 Ω |
| WR08W1R00FTL | Thick Film General Purpose Chip Resistor | 0805 (2012) | 1.00 Ω | ±1% | −200 to +400 | 1/8 W | match: resistance 1.00 Ω, tolerance ±1%, Sn-base lead-free termination · mismatch: general purpose construction, 0805 footprint, half the rated power, asymmetric TCR band, no automotive qualification |
| WR08W1R02FTL | Thick Film General Purpose Chip Resistor | 0805 (2012) | 1.02 Ω | ±1% | −200 to +400 | 1/8 W | match: tolerance, termination · mismatch: general purpose construction, 0805 footprint, 1.02 Ω, 1/8 W, asymmetric TCR band |
| WR08W1R05FTL | Thick Film General Purpose Chip Resistor | 0805 (2012) | 1.05 Ω | ±1% | −200 to +400 | 1/8 W | match: tolerance, termination · mismatch: general purpose construction, 0805 footprint, 1.05 Ω, 1/8 W, asymmetric TCR band |
| MK06S1R05FTL | Thick Flim Power Surge Chip Resistor (Automotive) | 0603 (1608) | 1.05 Ω | ±1% | ≤ ±200 | 1/4 W | match: resistance 1.05 Ω with WR08W1R05FTL, tolerance, termination · mismatch: surge construction, 0603 footprint, twice the power, symmetric TCR |
Read the TCR column as carefully as the power column. The surge parts are a symmetric
≤ ±200 ppm/°C band. The general purpose parts are an asymmetric −200 to +400 ppm/°C band.
That is a 600 ppm/°C spread against a 400 ppm/°C spread.
The series name on the surge parts reads “Thick Flim” in Walsin’s own export. That is a
typographical error in the source data, reproduced verbatim here so the rows can be matched
against the catalogue.
Walsin’s resistor product index is at https://www.passivecomponent.com/products/ — the
product index page, not a direct link to any datasheet PDF. The thick film datasheets we
hold locally are Walsin_WR_General_Purpose_Chip_Resistor.pdf and
Walsin_MR_Automotive_Thick_Film_Chip_Resistor.pdf.
Which Walsin anti-surge series should I be looking at?
Three, and they split by qualification rather than by performance tier alone. Our extract
holds 8,340 parts in Thick Film Anti-Surge Chip Resistor, 5,810 in Thick Film Triple Power
Surge Chip Resistor (Automotive), and 3,030 in Thick Flim Power Surge Chip Resistor
(Automotive). Two of the three families are automotive-qualified lines.
That split is worth noticing before you start filtering. More than half the family sits in
automotive lines. An industrial or consumer design is choosing from the 8,340-part general
anti-surge line unless you are willing to specify an automotive part, which is allowed and
often sensible but carries different change-notification terms.
What case sizes and power ratings actually exist?
0805 is the deepest at 3,929 parts, then 0603 at 3,212 and 1206, 2010 and 2512 at 2,411
each. 1210 holds 1,976 and 0402 holds 830. On power, 1/4 W leads with 3,531 parts, then
1/3 W at 3,491 and 3/4 W at 2,806. The tails are 1/8 W and 1/10 W at 435 each.
| Case size | Parts in extract | Case size | Parts in extract |
|---|---|---|---|
| 0805 (2012) | 3,929 | 1210 (3225) | 1,976 |
| 0603 (1608) | 3,212 | 0402 (1005) | 830 |
| 1206 (3216) | 2,411 | — | — |
| 2010 (5025) | 2,411 | — | — |
| 2512 (6432) | 2,411 | — | — |
One fact from the power distribution is worth carrying away. 1/5 W is a rated power missing
from Walsin’s public filter dropdown entirely. If you filtered the public search tool by
rated power, those 830 parts never appeared in your results at all.
The reason this catalogue is hard to search
Walsin’s parametric export fails above roughly 10,000 rows. An anti-surge family of 17,180
parts cannot be pulled in one pass at all. To extract it we split by tolerance, then split
again by rated power, and reassemble.
That is why the counts in this article exist nowhere on Walsin’s site. Venatech Limited, an
authorised Walsin distributor in Hong Kong, holds the reassembled data and can filter it on
any field — including the rated powers the public dropdown omits.
How do I specify an anti-surge resistor properly?
Start with the pulse, not the average. Establish the surge waveform, peak voltage and
source impedance your circuit will see. Compute the energy the resistor absorbs. Then check
that against the single-pulse withstanding curve in the datasheet for the series and case
size you want, and only then check continuous dissipation.
Four things decide the part after that. Case size, because physical length sets the voltage
the part can stand across it. Resistance, because it sets the current and the energy split.
TCR, because a surge part that drifts after every event is not doing its job. And
qualification, because automotive families carry obligations a consumer programme may not
want.
One note on layout: a surge resistor needs its pad copper as a heatsink for the microseconds
after the event, so do not starve it with thermal reliefs.
Frequently asked questions
Is an anti-surge resistor the same as a high-power resistor?
No. High power describes continuous dissipation. Anti-surge describes single-pulse energy absorption over microseconds. The constructions overlap — a heavier film usually gives both — but a part with a high continuous rating is not automatically surge-rated. Check the pulse withstanding curve, not the wattage.
Can I use a larger general purpose resistor instead?
Sometimes, but not reliably. Increasing case size raises the voltage the part can stand and spreads the energy over more film, which helps. It does not remove the laser trim notch where current concentrates. Where a surge is a specified requirement rather than a possibility, use a part specified for it.
Does anti-surge construction change the TCR?
Yes, and usually for the better. The Walsin surge parts in our extract are specified at ≤ ±200 ppm/°C symmetric. The general purpose parts at the same resistance are −200 to +400 ppm/°C. That is a tighter spread on the surge part, which matters because surge resistors are often in circuits that also run warm.
How many anti-surge parts does Walsin actually list?
Our extract holds 17,180 across three series: 8,340 Thick Film Anti-Surge, 5,810 Thick Film Triple Power Surge (Automotive) and 3,030 Thick Flim Power Surge (Automotive). The family is too large for Walsin’s own parametric export to return in one request.
What is the smallest anti-surge case size available?
0402 (1005), with 830 parts in our extract. That is the smallest in the family and the shallowest by count. If your design needs surge capability at 0402, confirm availability early — the choice of resistance and tolerance at that size is much narrower than at 0805.
Do surge resistors need a different footprint?
No. Case sizes are standard, so a 0603 anti-surge part drops into a 0603 land pattern. What changes is the layout around it: generous pad copper, and clearance set by the peak surge voltage across the body rather than by the working voltage.
Next step
Send us the surge waveform, the peak voltage, the resistance and the footprint you can
afford. We will return the Walsin anti-surge candidates with case size, resistance,
tolerance, TCR, rated power and series stated field by field, including the rated powers
Walsin’s public filter does not show. We will not tell you a part is equivalent. We will
show you exactly where it differs.
Send us your BOM → ·
Browse Walsin chip resistors →
Related reading: Chip resistor power rating by case size ·
Low-ohm current sense resistors: thick film vs metal plate
Cross it yourself. The cross-reference tool takes a single part number or a whole BOM column and returns the Walsin candidates with every field that differs stated plainly — qualification stays with you. Ready stock shows what is held in Hong Kong today, with an RFQ against any line.