Hello! Reflow soldering?

[Jeremiah Rose]

Hi everyone, I just found this group while looking online for a community workshop in Melbourne. I'm impressed!

I have a bit of a project for which I'm getting a PCB manufactured - I'm wondering if I could come in as a once off to do the soldering for it?

Do you guys have the tools for reflow soldering of SMD components? I'm assuming you would. I've only really done hand soldering of through hole components, but this new design has a SMD micro-usb socket with a hidden pad (underneath the socket) that I think I would need to use solder paste and a reflow oven to solder. Does that sound right?

Would love to come check out the workshop either way. :)

Regards,

Jerry

[Andy Gelme]

hi Jeremiah,

On 2015-07-10 17:11 , Jeremiah Rose wrote:
> I have a bit of a project for which I'm getting a PCB manufactured -
> I'm wondering if I could come in as a once off to do the soldering for
> it ?

Yes, visitors and newcomers are welcome ... especially to the group
sessions on Tuesday evenings or Saturdays.

If you intend using the tools a lot, then you might like to consider the
casual rate (which helps keep the space going) ...
http://www.hackmelbourne.org/about-cchs/fees

> Do you guys have the tools for reflow soldering of SMD components? I'm
> assuming you would.

To some degree ...

> I would need to use solder paste and a reflow oven to solder.

There may be some solder paste in the fridge (just need to check that it
doesn't belong to someone else). There are reasonable soldering tools,
a sterieo-microscope and a toaster oven (YMMV).

> Would love to come check out the workshop either way. :)

Please do. I'd recommend aiming to tee-up a time with members who have
good reflow experience and find out what times they are likely to be around.

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[Robert Powers]

There should be paste and flux in the fridge that belongs to me. Anyone is welcome to use them, although both might be getting a little old.

Cheers,

Bob

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[tubular]

There's also a hot air gun and a pre-heater platform if you want to try the hot air method

[Ajax Ozy]

Hi Jeremiah,

Yes reflow oven is best for a SMD micro-usb and is best for nearly all SMD soldering.
But not something readily available.

You can solder them with a hot air soldering iron like what is at the CCHS. But there are a few tricks that you need to do to get it to solder right, with out damaging the board and or component/s.

First issue is not getting pins and pads hot enough to solder
next is the flux dries up before reflow,
then not getting the pins and or pads to hot and damaging the board.

amongst some other issues.

to much solder paste
not enough solder paste
lifting pins
warped pcb

then there is the lovely issue of "Lead Free Solder."

If you can find some. get leaded solder paste. that will help a lot with reducing problems that can occur.

I will be in on Monday if you would like to have a chat about it.

regards
Ajax

[Steve Hodges]

Hi,

I run workshops on SMD soldering at the Perth Artifactory.  I agree with pretty much everything that Ajax has said.

My recommendation is that you get a toaster oven and build a temperature controller for it.  If you want to be really fancy you can try to make it follow a temperature profile, but most ovens on their own heat up at about the correct rate anyway and if you open the door a little they will ramp down in temperature pretty well.

Even without a temperature controller you can do it just by watching when the solder paste starts to melt.

I would recommend either standard tin/lead solder or (if you want a lower temperature) one of the tin/lead/bismuth solders which have a lower melting point.

The best way to dispense solder paste is with a pneumatic dispenser.  Surprisingly enough, this is really cheap and remarkably effective.

Get yourself one of these: http://www.ebay.com/itm/270906861147

And some of these: http://www.ebay.com/itm/301390673552

Get solder paste in a syringe, place the tip on the syringe and push the solder in until the needle is full (it's about 0.3cc).  Then place the solder filled tip on the pickup tool and press the button to dispense.  The size of tip (different colours are different sizes) determines the rate of dispensing.  Lower viscosity paste works better with finer tips (I tend to use the grey tips with the cheaper but more viscous Chinese paste).

0.3cc should be enough for over 100 pads, and due to the small tip it can remain usable for several days.  There is no pressure relief in the vacuum tool, so you may have to remove and reattach the tip every so often if the plunger stops coming up.

I have done some tests and too little paste is rarely going to be a problem as long as your contacts are not bent and your board not warped.  However I recommend you place enough solder on the pads to create a "nice" looking joint.  It is worth making up a test board to evaluate for yourself how much solder is required.

One other issue with toaster ovens is that parts inside them will expand and contract with the cycling heat.  Do not use a metal tray because they can suddenly deform, throwing your board in the air and your components off the board :-(

You guys also have a laser cutter.  You should investigate using it to make printed circuit boards.  It can be really tricky to get it working right, but when you do it's pretty amazing.  Read here: http://www.electronicspoint.com/threads/laser-ablation-of-pcb-resist.267381/page-3#post-1643996

Hope some of this is useful.

Steve

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[Ajax Ozy]

nothing like a good toaster oven reflow.

that is an option. Just need to watch the heating ramp speed.

I have always thought about making one and see how good it can be.
been slack. I use to have access to a vapor phase oven.

[Jeremiah Rose]

Thanks Bob, that's great.

I will drop in as soon as I get my boards printed.

Do you guys have a hot air station as well? For hot air soldering?

Jeremiah
0422 384 063

[Robert Powers]

We have one of these:

http://au.element14.com/tenma/21-10130-uk-eu/rework-station-900w-220v-uk-eu/dp/2062633

And one of these:

https://www.google.com.au/search?q=atten858d

Either works well for smaller boards on their own with a little practice and good luck.

I'm not sure about the pre-heater Lachlan was talking about, but couple one of the above with anything even remotely functional in that area, and you'll have a good long time before you run in to any technically unfeasible reflow job.

Cheers,

Bob

[tubular]

Pre-heater is this one (no longer mfrd?) 

http://uk.farnell.com/tenma/21-10135-uk/pre-heater-540w-350c-uk/dp/2064552?ost=2064552

[Jeremiah Rose]

Hey guys,

It's been a long time since I first posted but I'm finally ready to actually do some soldering now.

I have 3 tiny SOT23 hall sensors to solder to a board. Hoping your pre-heater will do the job.

Unfortunately I can't make it to the Tuesday soldering night (away working every week) but is there another night when I could come in?

Thanks,
Jeremiah

Jeremiah
0422 384 063

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[Adric Landman]

Hello Jeremiah,

We are open one Sat a month. This is usually the last Sat of the month.

Adric

[tubular]

SOT-23 isn't too bad with a standard soldering tip, if you use some gel or liquid flux.   I'm assuming you have 5 or 6 pin variants?   Start with locking down a corner pin and getting the alignment right.  Then go around the other pins.   

Don't worry too much if you bridge the pins, use some solder braid at the end to remove the connecting blob (if needed) 

Also might be of interest - we're getting a batch of "soldering challenge" boards together.   These have 8 exercises moving from simple through-hole soldering up to TSSOP-8 surface mount.   Should have the parts for a batch of at least 50 on Friday.  More details here:-

http://hackaday.com/2016/06/19/soldering-challenge-to-challenge-you/

[Adric Landman]

Also sorry to say but we are not going to be on on Sat this month as we have a Mini Make Fair on Sunday.

[Steve Hodges]

Hi,

The simple technique is to place a small blob of solder on one pad, then use a pair of tweezers to hold the part in place while you use a soldering iron on the lead to "push" it into the solder.  This forms a slightly dodgy join which will hold the part in place while you solder the other leads.  Then come back and re-solder the first lead.

The key is to use a dry iron (i.e.one with no excess solder on it) and fine solder applied VERY SPARINGLY.

It's not that hard :-)

Steve

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