Converting a design from using 0402 resistors to 1206? - Page 1
Forum section: electronics / projects

author: incf
author_rank: Frequent Contributor
timestamp: June 14, 2025, 05:57:04 pm
content: At one time in the past I implemented some design changes on someone else's design where they exclusively used 1206 resistors for everything.At the time, I thought it was absurd. 1206 resistors are very large compared to 0402 resistors.Can anyone weigh in on the pro's and con's of using bigger resistors?Bigger resistors are slightly more expensive. And they certainly are bigger.But possibly they might be easier to manufacture and rework.

author: wraper
author_rank: Unknown
timestamp: June 14, 2025, 06:04:35 pm
content: QuotePro's of using 1206 in 2025? - none whatsoever. Cons - poor reliability because they crack very easily in presence of PCB deformation.

author: incf
author_rank: Frequent Contributor
timestamp: June 14, 2025, 06:06:54 pm
content: Quote from: wraper on June 14, 2025, 06:04:35 pmCan you speculate about the relative fragility of 0805s and 0603s with respect to 1206s and 0402s?Ceramic is brittle, and I suppose PCBs flex by a certain amount, relatively unimpeded by the components. It probably could be calculated given a certain thickness of ceramic.

author: brumbarchris
author_rank: Regular Contributor
timestamp: June 14, 2025, 06:23:00 pm
content: Generally speaking (but not always true): the bigger resistor have a higher power rating.

author: MarkF
author_rank: Super Contributor
timestamp: June 14, 2025, 06:25:44 pm
content: I use 1206 and 0805 sizes because:- I'm old- My hands shake- I can't see wellmaking soldering a challenge for me.... Not so funny though.If I'm not mistaken, the larger parts have a higher power rating.Probably doesn't impact most designs.

author: ajb
author_rank: Super Contributor
timestamp: June 14, 2025, 06:45:36 pm
content: Yeah, there's really no particular benefit to 1206 over smaller sizes unless you need the larger physical size (ie, if you're using them as jumpers, like on a single-layer board, or need more clearance between terminals) or generally higher power capacity. If rework is a concern, then it's down to your preference there -- I would say 0603 is the sweet spot for me, but 0402 isn't that bad with a microscope and good tweezers and YMMV.Quote from: brumbarchris on June 14, 2025, 06:23:00 pmAside from the power rating, larger thermal mass and larger surface area can result in improved temperature stability / power dissipation if that's a particular concern -- but you probably aren't concerned about that unless it's a current sense resistor, which you're probably picking for its power rating and tempco anyway.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 14, 2025, 06:52:04 pm
content: There usually is a sweet spot (or sweet range) for everything. For SMD passive size it depends on if you are hand-assembling or getting them professionally manufactured; and in former case, it depends a lot onyourpreferences, and in latter case it depends on the capability of the CM (possibly affecting either cost, or minimum order size, or ease of discussions).Ignoring obvious use of 1206 size (power dissipation, voltage withstand specs etc), it makes very little sense. Shaky hands are mostly managed by other means than using huge components: finding good ways to rest your hands against table, good tools, etc. Poor vision is managed by a decent stereo microscope (under which it is comfortable to work for prolonged time). If 0805 feels too small, then the process needs to be fixed, not part size increased; 0805 is already "huge", and assembly won't get significantly easier by increase of size anymore.For most people, 0603 is very manageable for hand assembly and presents the sweet spot between not wasting board area, and being able to easily prototype. If that's too small, then 0805. 1206 "by default" is just going too far for no reason whatsoever.For professional assembly, 0402 is a good tradeoff because it enables you to useanymanufacturer without any special procedures, extra costs etc., including those with ancient or semi-hobby level equipment (any CM worth their salt in year 2025 can do 0201 just fine, so 0402 is one step bigger as a "safety margin"). And 0402 is still large enough that you can do some board level fixes, even if it feels a bit more tedious than the larger 0603.

author: wraper
author_rank: Unknown
timestamp: June 14, 2025, 06:57:51 pm
content: Quote from: incf on June 14, 2025, 06:06:54 pmIt regards of resistors, 0603 and smaller very rarely fail due to cracking. MLCC are a more sensitive but unless you place them right next to the mounting holes 0603 and smaller rarely fail too. 1206 MLCC are almost guaranteed to fail in significant percentage of devices when placed next to the mounting holes.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 14, 2025, 07:07:11 pm
content: Power rating and, clearance ( for voltage or physical jumper) are the only reason to use 1206.0805 is no harder to hand-work.

author: MarkL
author_rank: Unknown
timestamp: June 14, 2025, 07:08:36 pm
content: 0603 resistors and larger are usually marked with the value. 0402 and smaller are usually not.Useful for debugging and assembly verification.

author: tooki
author_rank: Super Contributor
timestamp: June 14, 2025, 07:25:32 pm
content: Quote from: MarkL on June 14, 2025, 07:08:36 pmSadly, more and more 0603s are being transitioned to no markings.(And how come ceramic caps never have values printed on them? Some did in the very earliest days of SMD, but the printing vanished quickly. It’s annoying.)

author: TimFox
author_rank: Super Contributor
timestamp: June 14, 2025, 08:12:34 pm
content: One uncommon case I encountered during my career where 1206 was required:With very high resistance values, such as 50 M\$\Omega\$, I found that the specified voltage co-efficient of resistance was too high (even at 10 V max voltage) for commercial resistors in small SMT sizes.Specifically, the only ones I could find commercially (from two vendors) that met the specification of < 0.1% for 10 V (100 ppm/V) were 1206 or larger.(Most vendors do not specify this co-efficient, but it was important for that design.)Thin-film resistors are not available at such high resistance, and thick-film resistors normally have much worse voltage co-efficient.This is far less of a problem with THT, but that was not practicable for that analog design.At the material level, the voltage co-efficient depends on the physical voltage gradient (V/mm) along the resistive path, which path length is longer for larger packages.

author: mariush
author_rank: Super Contributor
timestamp: June 14, 2025, 08:45:13 pm
content: where to use 1206 .... if you need to have a bunch of traces running under the resistor. Maybe if you do something high voltage (have a cutout in the pcb under the resistor)... maybe for current shunts for less variation due to heating and cooling.0805 makes sense because it's 2mm long, fits right across a 0.1" pitch (2.54 mm between two holes), you can easily convert a through hole design to smd using 0805 resistors and capacitors instead of through hole parts. Big enough to use with shaky hands.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 16, 2025, 10:44:59 pm
content: I've got a bunch of 1206 resistors and capacitors. Probably around 200.000 in total. No cut tape, just in little containers and I'm not going to count them. I got them for free after they were left over at my work because the last product that used them went out of production. I find them a bit cumbersome to use. They take up a lot of space when you design a PCB, nobody else wants to reproduce a PCB with those huge ancient parts, and they also don't fit well on matrix board. The're too big to fit on two adjacent islands, and they are just a bit too small to skip an island. 0805 or 0603 is much easier to use. And I do indeed find them quite fragile too.I think I've got them for close to 20 years now. It's hard to make a dent in such numbers for DIY.I also bought a bunch of 0805 parts. Just the chinese booklets with cut tape. I intend to use those for self designed PCB's that may also be of interest to others. I don't know anymore why I made that choice. 0603 would have been fine too. For DIY, it does not make much sense to go smaller then 0603. You still need room for the copper tracks, unless you go to > 4 layers and that's not often done for DIY.I did buy a JDS6600 DDS based function generator. It uses two ladder DAC's and I was not happy with it's linearity. I planned to replace the resistors with hand sorted versions, but they are so abysmally small that I gave up on this.

author: peter-h
author_rank: Super Contributor
timestamp: June 17, 2025, 07:33:05 am
content: 1206 was used in the early days of SMT, 35 years ago.Today, 0805 is nice because the markings are very visible and hand assembly is easy. I use 0805 everywhere. 0603 also has visible markings (on resistors) and I am slowly changing over to it for new values, because the space saving is useful.The smaller stuff is too small - unless you need it, and hand assembly is very hard.

author: xvr
author_rank: Frequent Contributor
timestamp: June 17, 2025, 09:52:42 am
content: You can use 1206 SMD parts to create some art (sculpture may be)Using them in PCB is a quite useless (as already said)

author: Whales
author_rank: Super Contributor
timestamp: June 17, 2025, 10:41:06 am
content: +1 for 1206 being good for unaided eyesight. They're also great for home-etched PCBs (more tolerant to bad etching, can fit a thick trace under them). Almost the size of 1/4W through-hole resistors, but a lot more convenient to place and bulk solder with no board flipping and no lead clipping.0805 is my preferred size because I can fit a via under it (leaving space next to the part for silkscreen text not marred by a via). You can easily get 10nF & 1nF linear (C0G/NP0) capacitors in 0805, but sadly 100nf linears only really come in bigger sizes.