How to solder a piezo?

That is the question :)

I use simple soldering station with thermal control, Sn60/Pb40 solder - one with flux core, another with silver addition, flux, soldering paste.

The layer in center is covered with some white film that adheres solder so good it's impossible to get off without braking the disk. But what the base metal this is? Whatever I do the solder just rolls off. It is even worse with flux - solder sometimes sticks to the flux, but never penetrates it. Until it evaporates completely there's always a film of flux between solder and disk and then again it's like water and wax. I tried temperature that barely melts solder - if the disk stays cold there is a chance of some solder sticking, but it falls off the next moment.

Is there any trick?

I'm not sure how to solder them, but I think the metal they're on is usually brass(I'm like 60% sure.)

Try increasing the temperature and hold the iron a little longer than usual. You will notice the solder go from a blob to more of a pool that spreads a little. Once this happens you can remove the iron.

Thanks for replies.

war_spigot: I'm not sure how to solder them, but I think the metal they're on is usually brass(I'm like 60% sure.)

hmm.. mine is white metal.

thegeekway: Try increasing the temperature and hold the iron a little longer than usual. You will notice the solder go from a blob to more of a pool that spreads a little. Once this happens you can remove the iron.

That's what I did at first. While the disc is cold solder sticks at least for a bit. Once it gets hotter the solder does not form a pool at all. I watched how to do it on youtube ( http://www.youtube.com/watch?v=AI3tTF3hv2c ) and it seems like magic, because the only way how I can get solder off the iron onto the disk is by dripping it or dragging fast, while disc is still cold. But as soon as the iron get's close to that solder it jumps right back to iron, even if there's so much of it that it falls on the floor under it's own weight. I tried to heat the disc from the other side to melt solder directly onto, but if forms a drop and rolls off (even if it stays it falls off when become solid). Something mystical :)

used to solder millions of these years ago when i worked for pision, you have to be very quick on the centre bit, else you will damage it

kivig: Thanks for replies.

war_spigot: I'm not sure how to solder them, but I think the metal they're on is usually brass(I'm like 60% sure.)

hmm.. mine is white metal.

The back part is white? Or are you talking about the center part(i.e. does it look like the one in the video)? Again, I've never soldered these, but rolling off and jumping back to the iron sounds like it's not hot enough. I'm getting a new iron in a couple of days, and if you're not successful by then, maybe I'll take a crack at it. If jonisonvespa has soldered millions of them though, I'd ask him for help.

jonisonvespa: used to solder millions of these years ago when i worked for pision, you have to be very quick on the centre bit, else you will damage it

I understand and there's no problem with it - it is covered with some film, that sucks most of solder from the iron in a split second. The base metal however is exactly opposite.

war_spigot: The back part is white? Or are you talking about the center part(i.e. does it look like the one in the video)? Again, I've never soldered these, but rolling off and jumping back to the iron sounds like it's not hot enough. I'm getting a new iron in a couple of days, and if you're not successful by then, maybe I'll take a crack at it. If jonisonvespa has soldered millions of them though, I'd ask him for help.

The base metal is white (like stainless steel). I cranked my iron to 450-460c and the result was the same, plus the solder started to cover with oxide film and flux just burned black on touch :) That piezo is dead for sure now (hint - buy a lot of 'em) :)

Edit: Ok! Still need too many tries to get it done while it's alive, but at least there's hope, so guess it's matter of practice from now. The recepie is to set iron to 240-270c and drag quickly across disc. If the temperature is less the solder seems to solidify too quickly and not adhere at all. The higher the temperature the shorter is the moment you can drag, as if the disc gets above solder melting point it starts repelling solder like wax&water. Piezo should be clean, so better don't touch it too much. After some bit of solder is stuck to piezo there's a chance of sticking the lead to it in the same manner. It's harder to stick the lead directly as slight movement while solidifying tears it off. Tried "yellow" piezos - they seem to adhere solder about twice as good. But maybe it's just me.

Thanks for replies! Hope someone will find this useful :)

kivig, OK, it's been 50+ years since my first soldering instructions in a book ( paper thing with words, no videos), but I do remember the first step is: "Scrape or sand surfaces to solder to remove oxidation and protective films". I noticed no one mentioned that. Usually works for me, then tin both surface and wire, just a touch of heat will connect them. The white metal may be aluminum? Whole other can of worms, I think you need special solder and flux. TomJ

Tumbleweed: "Scrape or sand surfaces to solder to remove oxidation and protective films"

Thanks! Scraping didn't help much, but filing the surface with fine file worked like charm. Solder sticks almost like to copper. On "yellow" disks that is. For white ones - no difference. So guess you're right about other kind of solder too.

I place a drop of soldering flux with a Q-tip or brush where I’ll be soldering. Works like magic.

The White Metal is silver plating for the second electrode contact, the piezo material is ''sputtered' onto the brass plate which is the second electrode and, YES soldering is an ART, one that neeeeds to be practiced and practiced long and well, soldering to a Piezo device is double the art... The method described as 'Dragging', Using a lower temp soldering iron and 'pre-fluxing' the work area is good advice. I use a Hakko temp controlled soldering station w/ an Antistatic iron and don't, unless the job demands (Many Pins) it, operate the iron at more that 500 - 550 deg F. Extended time/high heat or multiple uses of a soldered/re soldered joint WILL damage (De-Laminate) the PCB, remove copper plating and ruin PTH boards. A good teacher and a lot of experience are requirements for learning the "Art of Soldering". This is in my direct experience... I am 66 years old, I had my first job in a TV shop (Yes they Used to Repair TV's) when I was 14 years old and I was capable of doing Military Grade soldering when I was 15 years old (at both Librascope and Gonset). Electronics from Vacuum Tubes (all there was when I was young) to "Quantum" devices has been my hobby and profession since then. It was my 'hobby' from about age 7 or 8 years old until I was 14... Something NEW virtually every day... WOW

Doc

The soldering temperature and soldering time of the buzzer will directly affect the deformation coefficient of the buzzer, thus affecting the buzzer sound. May cause the buzzer sound to become small, no sound, hoarseness, etc.
In order to avoid the above problems, we hope that customers can refer to the soldering process parameter table to ensure the production quality of your company

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First time poster adding a seemingly useless addition to a 7 year old necrothread - shameless self promotion?