Soldering on the pure copper - Page 1
Forum section: electronics / beginners

author: glatocha
author_rank: Regular Contributor
timestamp: October 29, 2014, 09:52:07 pm
content: Hi,I have order few boards, but as I was saving costs I didn't go for the golden surface. Instead I have pure copper.I have a lot of problems soldering this boards. The solder is not sticking to the board. Instead it is sticking to my soldering iron.I am using the normal standard solder with Lead. Have the Iron on 420 degC, tried 370 also. heating up the pin and pad. Applying to solder to the other side. Have so much troubles with this. I am using quite a lot of flux also.Have cleaned the board with the alcohol. But maybe something else you can recommend.I think my problem is the board preparation, maybe the copper is oxidized already.I've got many golden covered boards before and solder them without any problems and much much faster.Thank for any advices.

author: 8086
author_rank: Super Contributor
timestamp: October 29, 2014, 09:54:36 pm
content: Bare copper?You didn't even get HASL?

author: jeremy
author_rank: Super Contributor
timestamp: October 29, 2014, 09:58:57 pm
content: Try an abrasive on some pads (very lightly!). If it starts to solder after that, you likely have an oxidation problem.

author: Psi
author_rank: Super Contributor
timestamp: October 29, 2014, 10:04:57 pm
content: At 420C the solder should melt and smoke vigioursly when it touches the iron.If its not them you have a temp problem.99% of the time 330 to 380C is all thats neededA quick scrub of the tracks with a mild abrasive will tell you if its a oxide issue.

author: wiss
author_rank: Frequent Contributor
timestamp: October 29, 2014, 10:13:25 pm
content: I have never had problems soldering on pure copper, either you have too low temp, or maybe photoresist still on the board? That is not easy to solder

author: glatocha
author_rank: Regular Contributor
timestamp: October 29, 2014, 10:29:52 pm
content: I will scrub the board tomorrow with a sandpapaer and give it a try.I also heard to mix flux with the alcohol and clean the board with a brush.But probably I will just order golden coated boards. As you know, I wanted to be cheap so I will pay twice

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 29, 2014, 10:38:52 pm
content: Your copper is either not hot enough or dirty. Pure copper is very easy to solder to, if it's clean, fluxed, and the right temperature.It doesn't have to be super-clean, flux can help with minor surface oxidation. But a little polishing with steel wool or another fine abrasive can remove the issue of corrosion from the list of possible causes. I'd be careful with sandpaper -- use a very fine sandpaper with very light pressure if you use sandpaper at all.I wonder if you're getting good heat transfer between the iron and the pads? Do you start by putting a bit of molten solder on the iron? That allows heat transfer that can warm up the pad to the right temperature. If you start with a clean, dry iron that has very little solder on it, it can be hard to get enough thermal contact between the iron and the pads to get effective heat transfer.If you don't want to practice on your custom boards, you can try soldering junk parts to plain unetched copper clad board. Google "Manhattan style construction" for many examples of what is possible with soldering to pure copper. For soldering practice, you don't necessarily have to start with functional circuits -- just soldering resistors to bare copper should help practice the technique. Here's an illustration:http://www.njqrp.org/islanderamp/

author: sleemanj
author_rank: Super Contributor
timestamp: October 29, 2014, 10:42:36 pm
content: Quote from: glatocha on October 29, 2014, 09:52:07 pmIs there a large ground plane by any chance?Perhaps a photo of one of these problem boards would help matters.

author: wiss
author_rank: Frequent Contributor
timestamp: October 29, 2014, 10:46:30 pm
content: I use steel wool on my home etched boards.

author: wraper
author_rank: Unknown
timestamp: October 29, 2014, 11:04:48 pm
content: You need to chemically clean oxide layer. IIRC weak hydrochloric acid solution should do the job. I have a chemical tinning solution which removes oxide layer by itself before tin deposits.

author: a210210200
author_rank: Regular Contributor
timestamp: October 30, 2014, 04:38:52 am
content: Use an acid flux but make sure you wash it off after properly. Acid fluxes will ensure the oxide layer is removed while your soldering. But if you don't wash off an aggressive acid flux it will then corrode everything.Don't use plumbers flux probably but that stuff can solder oxidized copper pipes with ease not sure if of their composition.For example I dipped a corroded copper heat sink into ~40% hydrochloric acid and the tarnish was instantly removed. Note acid fluxes and the fumes themselves are toxic, dangerous, ... (Read the MSDS first)

author: a210210200
author_rank: Regular Contributor
timestamp: October 30, 2014, 04:49:20 am
content: Be careful when using hydrochloric acid or acid fluxes which do contain strong acids and the fumes are not nice. (Actually most solder flux fumes are bad anyways but acid fumes are not nice)Also never ever mix water into the acids. When working with acids mixing water into the concentrated acid solution can cause an potentially dangerous exothermic reaction. (Spill control is different)Always pour the acid into water it is the only safe way to dilute acids.But pre-made acid fluxes should work as well.

author: pickle9000
author_rank: Super Contributor
timestamp: October 30, 2014, 04:59:13 am
content: Don't forget the basics- Iron hot enough- leaded solder with flux- clean copperAssuming you are soldering to clean copper, old solder can also be an issue. Liquid flux can help, many stained glass stores carry it (they sell copper foil tape as well very handy). If not go to a music store and get a small brick of rosin, smash it up with a hammer and place it in a cup of ISO for a few days. Strain the liquid and there you go poor mans liquid flux.Good luck

author: coppice
author_rank: Super Contributor
timestamp: October 30, 2014, 05:46:37 am
content: Hydrochloric acid? Steel wool? Sandpaper? What's wrong with going to the kitchen and getting the pot scourer? You need exactly the level of surface scrubbing those things are designed to achieve.

author: IconicPCB
author_rank: Super Contributor
timestamp: October 30, 2014, 06:42:37 am
content: Go to your local supermarket and get some tartaric acid ( food additive to make it sour ) it will disolve the tarnish off the cooper.Rinse iin clean water and dry with a towel. Do not dry in an oven.It should solder provided the other two components are right ( heat and solder wire ).

author: pyromaniac4382
author_rank: Contributor
timestamp: October 30, 2014, 01:41:48 pm
content: When I used to do the toner transfer method at home I told a friend at work that I was having problems getting the toner to adhere to the copper. His suggestion for preparing the copper was to add a small amount of dish washing soap to the etchant.Apparently a long time ago in the wafer fab where I work (before all of the restrictions) they use to add Dawn to a certain etchant. Of course he was not sure what the etchant they were using or what was being etched, and this was in the days of put your gloves on and stick your hands in to get the product out of the deadly chemicals...I used 3 parts hydrogen peroxide 1 part muriatic acid plus a drop or two of Dawn. This is a quick process. Depending on the acid strength and the copper clad thickness times may vary. You end up with a prepared board removing the oxidation without using all those abrasives that scratch up the board.

author: SeanB
author_rank: Super Contributor
timestamp: October 30, 2014, 07:58:08 pm
content: Best cleaner is a green Scotchbrite kitchen scouring pad, brand new out of the plastic wrapper, used on the soft side with some household scouring powder ( around a 1/4 teaspoon on the wet sponge) to clean the board. Wash afterwards with cold water and dry with paper towel, then apply some liquid flux to the bare board to keep it clean and oxide free. Spray flux ( SK10) will last decades in this role.

author: urlkrueger
author_rank: Contributor
timestamp: October 30, 2014, 11:35:47 pm
content: When I was a tech I would keep an eraser designed for erasing ballpoint pen ink in my tool box. There is just enough abrasive in them to clean copper traces for soldering or board connecter contact pads without damage. Don't know if they still make them but try an office supply store.earl...

author: G7PSK
author_rank: Super Contributor
timestamp: October 31, 2014, 03:20:45 pm
content: I often use a glass fiber pen to clean locally, they are sold in most good stationers as draftsmen use them to erase pencil or ink.