100% SMD project with domestic Iron reflow

[invzim]

Just a Hi to all, stumbled across the eevblog while searching for something on the Internet and found it highly entertaining and informative.

I'm very new to electronics design/making stuff, and although I always wanted to learn it, just making stuff blink&beep wasn't enough of a motivation for me to actually do something.

A couple of years ago I needed a little gizmo for an arcade machine, that simply wasn't available.  I saw no logical reason why it couldn't be done, so went down the route I guess many have gone before me.

1 - breadboarding, swearing a lot at development tools, and coming to the conclusion that yes, it actually works
2 - prototype on veroboard, more swearing
3 - all hole-through design made using eagle, weeks and weeks of routing, resulting in what I now regard as really really bad layout, PCB made in china, self assembled.  Improved my soldering skills a lot    I made 50 of these boards, sold them all and had to make more.  An excuse to move into SMD.
4 - Better layout in eagle, most parts SMD, hand soldered and coming to the conclusion that hole through is neither easier, faster or cheaper.  Made a 100 of these, sold them all, and had to make more.,
5 - 100% SMD, using a stencil for solder paste, and reflowed with a domestic iron.  1 dot is pre-heat, 2 dots are ramp-up and 3 dots is the reflow.  I also made my first youtube,  I hope it can contributes to other newbies moving into SMD and reflowing:



The projects homepage is here, http://jvspac.kirurg.org/ explaining what it does.

[GeoffS]

Neat. I'm a bit more confident to try some SMD stuff myself.

BTW, your link doesn't work, there's a /. on the end that shouldn't be there.

[mikeselectricstuff]

For manual pick/place, it's a lot quicker if you stick down all the componant strips to a small sheet of wood or PCB with thin double-sided tape, and then pick with a vacuum pen (real vacuum/fishtank pump or tube-in-mouth-suck, not the manual button ones, which are useless).

[Simon]

so basically you just "cook" the board ?didn't know the boards could take all that heat, neat, I'm starting to think more and more SMD, if anything I don't mind soldering the larger parts by hand although through hole is probably still going to be my main method for a while

[djsb]

What paste do you use,how do you make the stencil and how is the iron held in the correct position? I'd never thought of using an iron before,nice simple idea.

[TheWelly888]

Awesomely simple idea! How did you create the stencil?

[Simon]

What paste do you use,how do you make the stencil and how is the iron held in the correct position? I'd never thought of using an iron before,nice simple idea.

yea same questions here, I think hotplates are also used ?

[GeoffS]

Making stencils would seem to be the difficult bit. Is this a DIY option?
I've seen several places that will produce mylar or kapton stencils for about $25

[invzim]

Thanks for replies, good tip about the manual vacuum pens being rubbish.

I got the stencils from http://www.ohararp.com/Stencils.html - 25 usd + shipping, and since my design is very small, I got 4 stencils for that price.  And they accepted my eagle file which is a big plus, because I'm always scared that I screw up generating the gerbers.  Made 50 boards so far, and the stencil does not show any signs of wear - also it doesn't seem to mind being wiped off with alcohol after a session.

The paste is just something I got cheap off ebay, since I don't need a pound or more (and don't want to pay for it).  I use the leaded variety to keep things simple.

At first I got an electric skillet many people write about, but found that the heat was not very uniform, and got worryingly high in some spots, over 400C - so ditched that one.  For the domestic iron I already had, the temperature was pretty much uniform across the whole surface.  It's probably a good idea to use an IR thermometer to check the skillet/iron you're going to use to see if it's up to snuff.

I don't hold the iron at all, I just flip it upside down on my ironing stand and support it with books on each side 

[Simon]

yea the hot plate will have a spiral element set in iron that will conduct heat poorly giving a bad uniformity of temperature, the iron has a nice thick aluminium base that will heat up more uniformly.

[GeoffS]

Seem to recall someone using the hotplate option who recommended that thick aluminium plate be used in the pan to distribute the heat.
Has anyone built the toaster oven reflow device?

[johnmx]

It's probably a good idea to use an IR thermometer to check the skillet/iron you're going to use to see if it's up to snuff.

I will bring an IR thermometer from work to measure the temperature of my iron (Rowenta - Focus 2400W) in several positions. Then I post the results here. It should not be so different from other irons…I think.

[FreeThinker]

invzim how did you make the stencil? Nice vid

[dengorius]

invzim how did you make the stencil? Nice vid

Ehm I don't want to be a smart ass, but the answer is 4 posts above https://www.eevblog.com/forum/index.php?topic=1847.msg25609#msg25609

[FreeThinker]

invzim how did you make the stencil? Nice vid

I can only blame my increasing years.... sigh!

[johnmx]

I took some temperature readings with a piece of FR4 PCB on top of my flat iron. The temperature was measured with a FLIR i50. The emissivity of FR4 material can be something between 0.8 and 0.9, so I selected 0.85 in the i50 (selecting a lower value gives a higher temperature). The flat iron is a domestic Rowenta - Focus 2400W.

Thermostat position	Maximum temperature
*	122ºC
**	166ºC
***	215ºC
MAX	222ºC

Conclusion: Sure I can solder a PCB using this apparatus, but 222ºC is not always high enough to guarantee a good soldering, especially with Pb free solder paste.

[FreeThinker]

I took some temperature readings with a piece of FR4 PCB on top of my flat iron. The temperature was measured with a FLIR i50. The emissivity of FR4 material can be something between 0.8 and 0.9, so I selected 0.85 in the i50 (selecting a lower value gives a higher temperature). The flat iron is a domestic Rowenta - Focus 2400W.

Thermostat position	Maximum temperature
*	122ºC
**	166ºC
***	215ºC
MAX	222ºC

Conclusion: Sure I can solder a PCB using this apparatus, but 222ºC is not always high enough to guarantee a good soldering, especially with Pb free solder paste.

You can probably alter the stats set points if you dismantle the iron.Removing the stop/tang should allow enough adjustment http://www.diy-spares.com/cgi-bin/product.pl?PID=703173&query=Rowenta%20DE92%2e1C%20Steam%20Iron&model=DE92%2e1C%20Steam%20Iron&path=290104# check out pic.
NOTE!!! keep the wifey away from your modded iron if you value your life.

[GeoffS]

I took some temperature readings with a piece of FR4 PCB on top of my flat iron. The temperature was measured with a FLIR i50. The emissivity of FR4 material can be something between 0.8 and 0.9, so I selected 0.85 in the i50 (selecting a lower value gives a higher temperature).

From the image you included in your post, you can see the temperature differential where the steam holes are in the iron.
Something is needed to distribute the heat more evenly.

[House91320]

invzim how did you make the stencil? Nice vid

I can only blame my increasing years.... sigh!

lol

[johnmx]

Something is needed to distribute the heat more evenly.

A peace of aluminum with at least 1cm thick can do the job.
There are some cheap flat irons that work without water and doesn't have holes in the surface.

[dengorius]

maybe you can use some thermo conductive paste, like the one used for the CPU heathsinks

[Simon]

use the paste for what ?

[dengorius]

Well if you're putting a piece of metal like aluminum on top of the iron to even out the heat loss caused by the steam holes, you might as well add some paste between the iron and the piece of metal

[Simon]

well it would help transfer heat but the thickness of the plate will diffuse the heat evenly