Etching a PCB with Ammonium Persulphate

[ljcox]

The Ammonium Persulphate bottle I bought from JayCar states that you dissolve 1 part of AP in 5 parts water.
But it does not give any info about how much AP is needed per square cm of copper.
Obviously, you need more for a larger PCB than a small one.
Does anyone know? Any assistance will be appreciated. Happy New Year to all.

 

[augustinetez]

The description for the 250g bottles says:-

The alternative to Ferric Chloride. Mix one part etchant with 5 parts hot water to etch copper board. Contents will etch about 300sq/cm.

So that's about 1.25 litres for 300sq/cm (or a 100 x 3cm pcb), you should be able to scale it from there.

Also, find a local chemical supply company if you are going to do a lot of etching, it id about 1/10th the price Jaycar are selling it for.

 

[augustinetez]

Oh, forgot, keep water temp around 50C and watch the fumes.

 

[ljcox]

Thanks Terry,
Yes, I'll be able to scale it from your info. I normally buy electronic stuff from Semtronics in Mitcham as they are closer & cheaper than JayCar. But they are closed for their summer break. They can also source things from JayCar for me when necessary for a significantly lower price. And they are a reseller for Altronics. According to the Ammonium Persulphate container, they recommend 70C. Elsewhere I've seen 30C quoted. So I'll start with 70C - it will cool a bit while etching. I do it outside on the back lawn to avoid the fumes & wifely anger. Thanks again, Len

 

[augustinetez]

I used to do pcb's commercially many years ago, above 55C the fumes start getting bad so make sure you have plenty of ventilation - one of the byproducts is ammonia.

 

[ljcox]

Thanks Terry, I'll do it on the lawn when it's hot day with a breeze. Today would have been perfect as it's about 39C with a slight breeze, but I'm not ready to do it yet.

 

[Pommie]

When I made my own PCBs (a long time ago) I used Ammonium persulphate without any problem. I used hot water to prepare it so it was probably used at ~50°C. Didn't have any gassing problems. After use I figured it was mainly copper sulphate solution and just threw it in the pool (70,000 L). If you want to dispose without a pool then mix sodium bicarb with it and the copper will be precipitated as copper sulphate which can be thrown in the trash.

BTW, back then Jaycar sold 500g jars for the same price they now sell 250g.

Mike.
Edit, anyone ever tried sodium percarbonate? I can but that at $5/kg.

 

[augustinetez]

I was going to give it whirl after we moved out here to the middle of nowhere, but it was cheaper to just get them made in China.

Think there is still about 5kg of Ammonium Persulphate in the back shed.

 

[ljcox]

When I made my own PCBs (a long time ago) I used Ammonium persulphate without any problem. I used hot water to prepare it so it was probably used at ~50°C. Didn't have any gassing problems. After use I figured it was mainly copper sulphate solution and just threw it in the pool (70,000 L). If you want to dispose without a pool then mix sodium bicarb with it and the copper will be precipitated as copper sulphate which can be thrown in the trash.

Thanks Mike, I don't have a pool so I'll try the sodium bicarb trick you mentioned.
Len

 

[ljcox]

I was going to give it whirl after we moved out here to the middle of nowhere, but it was cheaper to just get them made in China.

Think there is still about 5kg of Ammonium Persulphate in the back shed.

Thanks Terry,
I want to make a prototype before I have several made professionally. I would prefer to avoid China given their stuffing around with our exports, etc. I've seen an ad for an Australian PCB manufacturer in the Silicon Chip magazine, so I'll ask them for a quote. Len

 

[Pommie]

Len, I'm going to guess you'll not beet China. I've had boards made for stupid cheap. And populated for a price I can't comprehend. Just use it.

Mike.

 

[augustinetez]

I've seen an ad for an Australian PCB manufacturer in the Silicon Chip magazine, so I'll ask them for a quote. Len

Yeah, I think you'll find all they do is aggregate orders and get them done in China anyway.

 

[Nigel Goodwin]

Yeah, I think you'll find all they do is aggregate orders and get them done in China anyway.

Even if they don't, it's likely to be a lot more expensive, and a lot slower.

When I started working where I do now one of the first things I did was redesign the PCB for one of our products, I had originally done a rough version at home with the premise that they would 'tweak it' as I didn't even know the display they were using - they hadn't altered it, and I wasn't prepared to waste the extra time building using those PCB's

Anyway, I redesigned the board (I've since done a few more upgrades to it as well, including changing to a different PIC) and asked my boss where he got the boards from - he eventually found the UK company he had used, gave me their email address and suggested I send the file for a quote, which I did. This was Monday.

I then mentioned I'd seen adverts for JLCPCB, with cheap prices and fast service, so he suggested we might try those as well - so I sent off to JLCPCB and paid for DHL delivery., this was Monday afternoon.

The UK company didn't even send us a quote until Wednesday, which was MUCH higher than the JLCPCB price, and JLCPCB had already manufactured the boards and dispatched them by then. We received the boards early Friday morning, and the quality was excellent, as all the boards we've had since have been.

The only slightly annoying thing is the cost of carriage, but it's coming from the other side of the world (and actually comes via Germany to get to the UK), but it's worth the high cost for the speed of delivery. Once you order higher quantities it's less of an issue, and when we order boards for our small scale production we order at least 100 at a time, and with some boards 600-800 at a time.

So unless Australia has some real issues with China, I would suggest ordering from there - it's a LOT more work making your own, and going to be a vastly inferior product.

 

[Pommie]

I second JLCPCB. I got 20 boards assembled but due to them now wanting me to sign in I can't access my previous orders. I used EasyEDA to design the (all smd) boards using 0402 resistors etc that were assembled by JLCPCB. From memory it took less than a week from ordering to delivery. Excellent company to work with.

Mike.

 

[ljcox]

Thanks for the replies. I'll do the prototype myself & then consider the options.
Len

 

[Nigel Goodwin]

I second JLCPCB. I got 20 boards assembled but due to them now wanting me to sign in I can't access my previous orders.

Mike.

Bit bemused by that?, you must have signed in to make the original order - and obviously you can't access orders without signing in, how would it know what orders were yours?.

Just checked, and I was able to log-in from home OK, even though I haven't done so for three months - still, back to work tomorrow, see how I cope.

 

[Pommie]

It's weird, I always allow google to store login details but for some reason JLC isn't stored.

Mike.

 

[augustinetez]

Pcbway are the same, only seem to store it for a few days and then have to do it again.

 

[Nigel Goodwin]

It's weird, I always allow google to store login details but for some reason JLC isn't stored.

Mike.

I use Firefox, it stores log-in details just fine. At JLCPCB every board I've ever ordered is listed and available to reorder.

 

[Pommie]

Just did password recovery and the 20 board I got assembled (including a 16F18854) cost AU$98 including postage ($20).
The boards,

The two items above the LEDs (D0 to D7) are resistor arrays - four times 0402 resistors in a single package. No way could I have soldered these boards myself.
The 3 pin chip is a DS2411 one wire device so each board has an individual serial number.

Mike.
Edit, I think I must have been in Brave (browser) which is why password wasn't stored.
Edit2, JLCPCB will now do through hole components also.