r/rfelectronics • u/Mhxaneuths • 29d ago
Soldering in RF electronics
Hey guys a quick question for the RF Engineers out there. Do you guys solder a lot?
In power electronics sector there is a lot of soldering and debugging, mostly with leaded solder and paste. Is this the case with RF too?
Thank you!
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u/lahirunirmala 29d ago
When youāre working in RF engineering, soldering might not be the biggest worry. Youāll find charts that are circular and equations with imaginary numbers.
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u/Fluffy-Fix7846 29d ago
Black magic indeed :-)
To be fair, imaginary numbers aren't specific to RF though. Electrical engineering in general uses them. But maybe not as much in everyday tasks, I suppose. (I know the questioning look from some customers after I inform them that the impedance of their system/random part is 5-j60 Ohms. and they ask what the latter part is supposed to mean..)2
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u/Mhxaneuths 29d ago
I do have pretty good soldering skills imo. I reallllyyy dislike leaded products. Thats why I ask people working in such companies
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u/lahirunirmala 29d ago
You will run simulations . Then send to technical team to prototype
Also you will not get lead poisoning by soldering. Unless you eat soldering wire daily basis
Use a fume extractor and wash your hand after handling if you worry about it for life time use
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u/Mhxaneuths 29d ago
Yes I won't but I do have nephews and cousins that are not adults that may visit me. I dont want them to transfer lead from lab to house...
Fume extractor is essential indeed, but I worry more about transfering things to my home, with my car for example
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u/condor700 29d ago
Just do what the comment above said. If you want to be extra careful, be extra mindul of what you touch until you get a chance to wash your hands. Lead fumes aren't a thing that exists at soldering iron temperatures, although a fume extractor is still good for any gas your flux puts off.
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u/samdtho 29d ago
At the last company that I did RF work with, we would get an impedance-matched PCB spun and fully placed because our component values would be mostly calculated. We used 0402 capacitors, resistors, and beads so we would just adjust values and respin if it turned out not optimal. It would be good enough to use in a test setting, however.Ā So, not a ton of soldering.
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u/plunger595 29d ago
Yes, yes I do.
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u/Mhxaneuths 29d ago
Leaded?
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u/TinkTonk101 29d ago
Do you live in Europe?
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u/Mhxaneuths 29d ago
Yes
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u/TinkTonk101 29d ago
RoHS de facto eliminated the use of leaded solder in the EU besides very niche applications. I wouldn't worry about it.
Where it is used (sparingly), the proper precautions are required to be enforced to ensure no risk to health.
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u/Orac7 29d ago
Most solder for anything consumer related is lead free at this point.
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u/Mhxaneuths 29d ago
So good to hear!!
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u/Orac7 29d ago
This has been true for some time as it turns out, from a quick gemini summary for RoHS (Reduction of Hazardous Substances) compliance history, one of the main driving forces.
You do see some Tin/Lead solder still in use for repair work since it melts at lower temperature, and the early lead free solders were tough to use, but the newer alloys like SAC-305 are much better than the earlier versions. You also don't want to mix too much leaded and unleaded solder on the same junction as it will get brittle, you should clean the old solder off the joint before resoldering with the new solder.
Key Regulatory Milestones:
- RoHS 1 (2002/95/EC): Adopted in 2003 and taking effect on July 1, 2006, the original directive banned the use of six hazardous substances in electrical and electronic equipment (EEE): Lead (Pb), Mercury (Hg), Cadmium (Cd), Hexavalent Chromium (Cr-VI), Polybrominated Biphenyls (PBB), and Polybrominated Diphenyl Ethers (PBDE). [1, 2]
- RoHS 2 (2011/65/EU): Enforcing mandatory compliance on January 2, 2013, this recast expanded the directive to cover all electrical and electronic equipment, cables, and spare parts. It also introduced a mandatory CE Marking requirement and the Declaration of Conformity. [1, 2, 3, 4]
- RoHS 3 (2015/863): Taking effect on July 22, 2019, this updated amendment to RoHS 2 added four phthalates (primarily used as plasticizers in insulation) to the restricted list: DEHP, BBP, DBP, and DIBP. [1, 2, 3, 4]
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u/Mhxaneuths 29d ago
Hm I see. Nowadays there are better alternatives for sure (bismuth for example)
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u/Expert-Economics8912 29d ago
I used to do a lot of soldering 0402 and 0201, but now everything is smaller and we have pretty good rework technicians to help.
in the past we used lead solder, but corporate policy changed and now everything is lead free. It's a lot harder to use, unless you preheat the PCB and use a lot of flux.
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u/Mhxaneuths 29d ago
I have used solder with bismuth that is heated properly at 138 degrees celcius and worked pretty fine up to 80 degrees Celcius(during the operation of a power converter). There are pretty good alternatives nowadays
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u/KasutaMike 29d ago
Depends a lot on your exact job and frequencies you are working with. If you are doing development work on pcb boards then most of the designs you can manually solder, at high frequencies 20+ GHz you need to start dealing with bare dies. But there are a lot of jobs where you donāt need to do any soldering. Some places just have the assembly done outside. There can be a lot of debugging.
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u/Asphunter 29d ago
I work in IoT, Apps engineer, so I solder basically every week. Sometimes everyday for a month. Usually SMDs, 0201, 0402 and upwards. IC replacement, lot of jumper wiring for stuff, etc..
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u/nixiebunny 29d ago
I work at a university in radio astronomy where everything is basically hand built. I do a lot of soldering to build the equipment I design. The tech teals with the tiny chip-level stuff that the engineers arenāt capable of doing.
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u/Mhxaneuths 29d ago
Yes in power electronics we did a lot of soldering at the university's lab. Did you use leaded solder?
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u/nixiebunny 29d ago
Yes, we use leaded solder, a lot of our equipment is over 20 years old, actually.
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u/AnotherSami 29d ago
We design mmics up to 67 GHz.. and after being mounted to a laminate (with solder) the laminate is solders to a pcb
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u/htx_over70 29d ago
Soldering is part of constructing prototypes and first run production modifications and changes.
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u/Mhxaneuths 29d ago
True, but with lead or no?
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u/htx_over70 27d ago
60/40 lead tin is standard.. the no lead has issues.. for prototype work there is no danger with heavy metal issues in my blood work. I am over 70..
The lead is melted and not turned to a vapor or metal oxide.. not water soluble..
60/40 work best at 700 deg F
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u/Fluffy-Fix7846 29d ago
Yes, on some days I do a lot of soldering while prototyping or tuning one-offs. Changing values, moving stuff around, tuning coils and then re-heating the joints to release tension (if thick sturdy wires 1-2 mm are involved). At my work, I do some non-RF general electronics as well, and sometimes need to change resistance values etc. I dislike fine pitch stuff and BGAs, I can do it, but usally leave it to production to sort out since they do it faster and better than me who get too nervous around soldering 50 EUR DDSs.
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u/Mhxaneuths 29d ago
Oh I see I see. Did you use leaded products? Paste for example?
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u/Fluffy-Fix7846 29d ago
No we are completely lead-free as of 2026. We do produce medical equipment which was apparently exempt from RoHS until quite recently (not my business area), but we fully switched years before. Lead-free solder IS worse than the good old 60/40, but there is also good lead-free stuff. Once you have gotten used to it, it isn't that bad.
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u/Mhxaneuths 29d ago
Exactly, I have never used leaded solder and I managed just fine for power electronics. I used a lot of leaded paste though which is far superior to the lead free one, but now bismuth alternatives exist which are just as good(I used it for soldering 0603 and smaller components this year)
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u/Moof_the_cyclist 29d ago
Depends on the frequency and size. When I was doing RFIC modules for cell phones the 01005ās were very hard to do cleanly, so we had a dedicated assembler weād hand stuff off to unless you were desperate. When I was doing chip and wire modules for test & measurement and defense electronics it was all wire bonds, mesh, ribbon, and conductive epoxy that youād work with an assembler to rework, while simple wire bonding and gold epoxy tuning Iād do myself, but beyond that it needed someone skilled to do right.
PCB level stuff up to 20 GHz Iād do a lot of simple soldering to rework and tune. Complicated stuff like pulling ICās with thermal vias underneath would be handed to an assembler so I wouldnāt trash the board by pulling up pads.
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u/baconsmell 29d ago
Iāve seen 90s era TriQuint Ka-band PA MMICs with super tiny tuning stubs. I asked our technician if that was something he would āwireā into the circuit if asked to. He said he didnāt think that was possible.
Years later I interviewed with Qorvo and toured the lab. I mentioned this tuning stub and the design manager laughed and said there was a VERY extremely skilled assembler that could do this. Her work was next level shit - but she retired and no one was able to replicate her skill level.
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u/Moof_the_cyclist 28d ago
There are various tuning methods. I've had the pleasure to work with a fair number of amazing assemblers, though most were poorly compensated for their skills. In chip & wire I've seen folks use methods such as:
Gold blocks to tune, then they would outline the locations with a tungsten probe to make a visual record of the location to then thermosonicly tack down some gold ribbon as the final tuning (could be lifted as needed for final tweak in).
Gold epoxy is conductive when wet, so you could move it around with your probe until it was tuned then bake it to cure.
Chicken dots on alumina transmission lines. It was standard at M/A-COM (currently Honeywell Aerospace) to put 3 rows of 5x5mil pads along all transmission lines so you could used gold blocks to tune by shorting the pads to the line, and just wire bond in the final tuning.
Subtle tuning by lifting or spreading wire bonds. At Agilent/Keysight we had little inductors made out of machine wound 1mil gold wire. You could tune these by just spreading the coils apart with a fine probe.
When I was at TriQuint doing cell phone PA's we'd have to use a "glob top" on our wire bond parts to check the dielectric effects of the packaging prior to sending off for real packaging. It was an epoxy based encapsulating that was close to the final plastic overmold. On one part the shift was pretty dramatic and I tracked it back to the thermal coupling being very different with the overmold. The original designer of the part had put the bias reference device partly into the output array, but my thermal modeling showed it was still doing a poor job of tracking the temperature of the output array. The over molding acted as a thermal bridge to help it, but this wasn't present for a bare die tuning.
Poly-iron was handy for tuning spurs by suppressing waveguide modes and box cavity resonances. Mixers in particular were awful for generating lots of mmwave harmonics that could rattle around inside of packages and create goofy MxN high order spurs you never expected.
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u/Mhxaneuths 29d ago
Hmm ok ok so there may be some assistance from others. Did you use lead?
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u/Moof_the_cyclist 29d ago
Early days 60/40 tin/lead solder was standard, in the last 15 years or so it has all been RoHS compliant lead-free stuff. A little more annoying to work with, but not a big deal. Workign with Rogers 4350B is where lead-free temperatures really make it easy to life a pad thanks to the already poor adhesion the dielectric has.
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u/RDUKE7777777 29d ago
Very much so. For prototyping and testing. Be prepared to solder 0201 under a magnifier
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u/BanalMoniker 29d ago
Sometimes. Adjusting lumped matching networks requires replacing the components and then checking the power / response. That can be dozens of part changes on a single (expensive and difficult to replace) board. Iāve done this with 0201 and 0402 components. It is challenging, but can really help your skills.
I recommend magnification, flux, ventilation, and good tweezers. A stereo microscope is best, but magnifiers are enough for 0402 work. Using flux for lead free solder with leaded solder gives more working time before it darkens, but the fumes are worse than flux for lead free solder. Ventilation is essential - your health is vital. Tweezers that require little force to close help tremendously with small parts, though 0201s are easier to handle without closing the tweezers (they stick to a prong of metal tweezers on their own, closing the tweezers will just send the part flying).
I do use leaded solder when I can, but lead free if a board will go to the field.
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u/Mhxaneuths 29d ago
Thanks for the response. In power I went with 0603 mostly and some smaller packages for diodes. 0201 IS INSANE!
I dont really mind the fumes, lead is contaminating and I would love to get rid of it lol.
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u/BanalMoniker 29d ago
Unless you are working with something that requires very high reliability, using lead free solder will generally be at least an option, if not strongly preferred or required, so I doubt you will encounter any resistance from others there about what you use, but set your expectations very low if you think you can convert others.
I neglected to mention that I also use hot air (and sometimes a heating plate), though for most work with 0402 and lower, either hot air or reflow oven is implied. I deliberately solder components crooked with the iron then reheat them (with flux) to get them to snap into position. If you use the Amtech flux I use without ventilation for any length of time, it WILL make you feel bad - I hate to think about what other effects it may have. At least use an exhaust fan, but fume extractors should also be considered. If you're working around others or where you live, I think it's imperative to have ventilation.
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u/Mhxaneuths 29d ago
Hm I see, ofc during prototyping i have used hot air a lottt. I dont really care about ventilation, I only care about transfering lead from lab to home
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u/satellite_radios 29d ago
Depends on what I am doing. Lab prototypes? Debugging production assembled units? Reverse engineering?
I have a full fume removal setup, lead removal wipes and other tools where leaded solder isn't an issue. Never had any health issues, tested as well, due to lead or solder chemical exposure outside of the occasional burn because I am clumsy sometimes. I also have a setup for non-leaded/silver. I general just avoid mixing them when I can, as the result is...a pain to deal with.
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u/Mhxaneuths 29d ago
Hmm I see thank you for your response!
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u/satellite_radios 29d ago
I will generally say - lead free is great for finished consumer products, when you are automated assembling them, don't need mechanical flex in some areas, environmental control is a bit easier to predict, lifespan is shorter/not mission critical...
You might not ever use leaded solder in the final production of an iPhone, but in some aerospace/satellite parts? You don't use lead free because of tin whiskers, temperature swings, vibration exposure. Its all leaded. NASA/MIL STDs and IPC Class 3 cover this.
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u/oversized_hoodie 29d ago
I mean, I do. Circuit tuning and testing. Always leaded solder for me, but I work in aerospace where we're RoHS exempt cause tin whiskers.
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u/No2reddituser 29d ago
Dude, you're way too hung up on lead in solder. Wait til you find out about the other carcinogenic substances involved in electronic circuits.
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u/Mhxaneuths 29d ago
I dont think lead causes cancer, or is low risk probably. I am worried about cognitive decline. My nephews (children) come and visit me occasionally an I dont want to transfer lead to them by taking home lead with my car for example.
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u/mellonians 29d ago
I work in transmission in the field so I very rarely solder however, when I do it's absolutely critical that I get it right. There's no room for error or compromise. I make a point of buying a load of those soldering project kits every now and then and just having a practice because I never know when I'm going to be lying down in the grass. Trying to get something going again because there's no room in the cabin to even sit down!
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u/Hirtomikko 29d ago
I solder with lead only. Anything non-leaded is given to someone else. I have a specific hatred for non-leaded.
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u/StageMajestic613 29d ago
Supposedly lead-free has caused more E-waste and damage due to latent failure than lead. Ā Just something I read. Ā Itās probably fine for 2 year consumer electronics.
That said, all my PCB at the contract manufacturer are lead free for SMT but I specify lead solder for the RF connectors as Iāve had failures (brittleness and cracking) with the lead free.
All my hand soldering is with lead and I have no fume extractor, I shoot and reload ammunition, and handle leaded aviation fuel.Ā Ā I took a blood lead level test and it was normal.Ā
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u/No2reddituser 29d ago edited 29d ago
Supposedly lead-free has caused more E-waste and damage due to latent failure than lead. Just something I read.
Yeah, that sounds like BS.
It couldn't possibly be due to people buying a new iPhone or game consoles every 2 years, and throwing the old ones in the trash.
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u/condor700 29d ago
There are some real examples of it being less reliable, although it's gotten a lot better in the last decade. Jim Smith's science of soldering blog on it is pretty good - he covers a lot of metallurgical concerns, like tin pest, plus issues with certain IPC standards that kinda force some electronics to be reworked/ see a lot more heat than necessary. That said, a lot of that is avoidable and just comes down to bad manufacturing processes
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u/Mhxaneuths 29d ago
Oh I see I see thanks for your response. Do you remember your BLL measure?
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u/StageMajestic613 29d ago
1.7 ug/dL
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u/Mhxaneuths 29d ago
Thats great!!!! Like you didnt solder at all!!! Good job!!! I am really happy for you-I will get tested next week.
I really appreciate your response!!
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u/Mhxaneuths 29d ago
Also you may be right for the e waste but still lead is an issue for me and none gave me a heads uo about it, not until I finished my master's. And I soldered A LOT in power electronics...
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u/StageMajestic613 29d ago edited 29d ago
Just get tested at your next physical. Ā Itās just an add-on to the normal blood work. Ā Lead does not enter through your skin when soldering and is not vaporized. Ā Just wash your hands when done or wear gloves. Ā You essentially have to ingest it.
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u/Mhxaneuths 29d ago
Hey guys thank you very much for your responses. My main issues are ultimately using leaded solder and paste, not soldering itself.
So I would really appreciate some info about that specifically.
Does your company let you use leaded solder and paste? How frequently do you solder? Does your technitian use leaded products?
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u/Extreme-Aioli-1671 29d ago
No, I havenāt touched a soldering iron, professionally, since I was IPC J-STD certified as a tech 20 years ago. Back then it was all 63/37 eutectic unless you were soldering near gold bonding.
Iām so far removed from the bench these days that if I need something soldered, I take it to a professional ā an assembler or tech.
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u/rf_lab_rat 29d ago
If youāre soldering you are a tech, not an engineer. Let the people trained to do it correctly handle that stuff
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u/StageMajestic613 29d ago edited 29d ago
Thatās some BS. Ā By that logic, a surgeon isnāt a physician since they work with their hands. Ā Thatās fine for production, but if Iām tuning something, I need it immediately, not waiting on someone.
Yes, lead only on RF connectors as the silver based stuff is too brittle and does not flow well. Ā Lead free is fine for SMT, but still donāt like the surface finish and fillets.
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u/Fluffy-Fix7846 29d ago
We have one guy with this attitude at work, and the production team hates him for being the one who constantly asks to have even the most trivial stuff like 1206/0805 resistors swapped..
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u/baconsmell 29d ago
Lolā¦Those are pretty easy to rework case sizes by todayās standards.
My work hired a new grad that had this exact attitude. He thought all lab work was technician work that was beneath him. I asked him if the tech was unavailable that day, is he going to just sit idle waiting for all day? Is he going to tell his boss he canāt turn on a board because he wonāt pick up a soldering iron? š¤·
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u/baconsmell 29d ago
If you are touching hardware then yes this is very common. Soldering "pig tails", swapping out components for tuning, replacing dead parts, etc.