SMT and an old dog stymied by new tricks!

Having watched the many videos on SMT technique on YouTube, I am tempted to give it a go but taking a circuit designed for through hole technology and trying to produce an SMD PCB I find that it is not so easy to source the larger 1206 package SMT resistors which I would prefer to use. No supplier I have come across so far offers a range similar to E24. Am I missing something?

What is E24?

http://www.jameco.com/shop/StoreCatalogDrillDownView?langId=-1&storeId=10001&catalogId=10001&freeText=smd%20resistor%201206&search_type=jamecoall

http://www.banggood.com/search/1206-smd.html
.

Or: http://uk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&langId=44&storeId=10151&categoryId=700000005450&showResults=true&pf=111629309 and select from resistor case style on the left hand search options

E24? http://www.resistorguide.com/resistor-values/ but then you know that LarryD.

I have used through hole resistors for several decades having built up quite a stock over the years. I had expected to see just a list of values on suppliers websites but not so, that's too easy I suppose. Then I had a look on Ebay and the sellers there use drop-down menus - much easier!

Now all I need is a new pair of eyes and steady hands!

E24, Yes but others don’t.

Like me you need a microscope and one of these:
2017-02-07_13-24-39.jpg

Sounds like you would be a good candidate to add some stuff here:

.

Adrifran39:
No supplier I have come across so far offers a range similar to E24. Am I missing something?

What suppliers were you looking at?

Where do you live?

1206, 0805, 0603...etc are all commonly available everywhere I have ever looked.

What components are you looking for in those footprints that arent available?

As an alternative, to manually soldering all SMT parts..

What I do is the following:

1.) I have a vinyl cutter/plotter (used for stickers..etc) that I also use to cut solder masks/stencils from my gerber files

  • thread about it floating around here somewhere

2.) take my newly cut mask, lay it over my designed/order pcb's....smear/squeegee some solder paster over the stencil, remove stencil,

3.) Populate board with parts

4.) Throw it into my $17 Wal-mart toaster oven (stock, no heating profiles, not controlled by some arduino..etc just plain jane stock toaster oven) at around 250 degrees.. for like 3-5 minutes.. once I see the solder dry... it will 'shine up' (melt) in a few more seconds... once I see that, I wait maybe another 20-30 seconds.. and turn it off.

Let them cool down and start playing with my new toys I just made! :slight_smile:

I understand a vinyl plotter may be a bigger investment, but its worth its weight in gold for just being able to make your own solder masks, instead of paying $25 a pop for them elsewhere!

I use a Silhouette Cameo to be clear.

Oh, your heating profile just kills me! Get a meter with thermocouple probe and do it properly, such as
http://www.extech.com/display/?id=14823
Ramp up temperature to 100-125C, hold for 90 seconds. That activates the flux in the solder paste.
Ramp up the temperature to 185-200C, never exceed 205C, that reflows the solder in between 80-90 seconds.
Cool down by slowly opening the door, once below ~183C the solder will have solidified.

Don't damage parts with overly long heating times.
250F should not be melting solder, that's only 121C. Not nearly hot enough.
I use an ancient Sears Kenmore toaster oven with 4 heating elements, 1500W. Smaller ones are only 1000-1200W and do not ramp up the temperatures fast enough.

I use Kester EP256 solder from https://www.cmlsupply.com/search.php?Search=&search_query=ep256, 35g syringe will last you a while, they a good price on it.
I bought a 500g tub and refill my syringe (I bought a few to start, and then the tub). Keep it refrigerated to last longer. Let it warm up before use.

The problem with a thermocouple is that it measures the temperature of the thermocouple, not the board, and
in environments with strong radiant heat the temperature is not uniform unless you use long soak times. I go by
eye and it works well - you can see the melting front moving across the board, especially if there are big
components with significant thermal mass like large inductors.

My converted cheapo oven has both elements mounted at the top, I moved the bottom one, and a bimetaliic
strip crude temperature control, but works nicely once you get used to it! I've done double sided SMT and
never had a part fall off the bottom (although I place the board on a few layers of Al foil to help prevent this).

CrossRoads:
Oh, your heating profile just kills me! Get a meter with thermocouple probe and do it properly, such as
EX330: 12 Function Mini MultiMeter + Non-Contact Voltage Detector | Extech Instruments
Ramp up temperature to 100-125C, hold for 90 seconds. That activates the flux in the solder paste.
Ramp up the temperature to 185-200C, never exceed 205C, that reflows the solder in between 80-90 seconds.
Cool down by slowly opening the door, once below ~183C the solder will have solidified.

Don't damage parts with overly long heating times.
250F should not be melting solder, that's only 121C. Not nearly hot enough.
I use an ancient Sears Kenmore toaster oven with 4 heating elements, 1500W. Smaller ones are only 1000-1200W and do not ramp up the temperatures fast enough.

I use Kester EP256 solder from https://www.cmlsupply.com/search.php?Search=&search_query=ep256, 35g syringe will last you a while, they a good price on it.
I bought a 500g tub and refill my syringe (I bought a few to start, and then the tub). Keep it refrigerated to last longer. Let it warm up before use.

Fair enough. I dont know what the actual 'temp' is inside (as I dont have it automated by any sense of the word, all visual!) LOL..

I know I just turn my 'dial' to between 200-250. (whatever it 'truly' equates to.. YMMV)

The point is that "I" feel there is a better approach when attempting SMT/SMD soldering by hand... and was just sharing how easy a basic set-up could be thrown together.

Have never lost a board, caused faulty part/component failure, and have done two sided boards as well.

  • (knock on wood)

People who do ceramics use a ‘cone’ for temperature/firing.

Just thinking out load, wonder if a visible technique using solder could be put together to do something similar at different locations in the oven.

https://www.google.ca/search?q=ceramic+cone+chart&rlz=1C9BKJA_enCA713CA713&hl=en-US&prmd=isvn&tbm=isch&tbo=u&source=univ&fir=8QfSWC-tx_jKCM%3A%2C82XVOYGTAFGmnM%2C_%3BzizBVVczQDYZfM%3A%2CEDaBbje-cNHXNM%2C_%3BJKnATJk16WWVtM%3A%2CGYzy0t0VQXx2NM%2C_%3BCfyX0OspUHMkdM%3A%2Cawa_dTph9LcbpM%2C_%3BIjoJvpXqVBTreM%3A%2CddbgpvvN2Vm25M%2C_%3BIRnRI875i_C0MM%3A%2C0AwJ3gNZE7_INM%2C_%3BsUCTs_IX0YwAaM%3A%2C5pPJqnFxu7fk_M%2C_%3BTRmAdR2jn49OQM%3A%2Ccczot0tuNfvm7M%2C_%3B0dpEhF-RM6_4YM%3A%2CnL5BJflykSq0wM%2C_%3BqrdJzmBHUtrQ5M%3A%2C1jzFb7XWgvMldM%2C_&usg=__frUVq7VztHYVProiWS5QqZccstA%3D&sa=X&ved=0ahUKEwjGvbzTzKLSAhUmxlQKHVkvAIYQsAQIGQ&biw=1024&bih=653

Edit:
Maybe something like a solder fuse when melted, a car horn :wink: goes off or other.

Maybe a young Boston man could make small boards that have 1206 pads connected to the outside world.
You place a zero ohm SMD resistor with solder paste on the pads.
Perhaps at several locations in the oven.
When connections are all made, stop the cycle or start a timer . . . then stop the cycle.

Edit:
OK, I just tried the zero ohm SMD resistor with solder paste.
Result, solder paste can be ohms without melting therfore no go. :frowning:

But perhaps the melting fuse might work.

.

Really need temperature measuring to ensure the never exceed temperature is not exceeded, that can damage parts.
The solder needs two temperature ranges ideally - one to activate the flux, one to melt the solder. See the temperature profile for EP256 solder paste in the attachment.
Compare to the profile for an 0805 LED, which is based on lead-free solder.
http://www.osram-os.com/Graphics/XPic9/00078860_0.pdf

I think there are things similar to what you suggest that will indicate when the temperatures are reached. I’m looking now for a paint or tape or something similar.

Kester_EP256_Data_Sheet.pdf (54.9 KB)

Maybe a couple of these, for the low & high range
http://www.dkr.co.il/COLOTEMP---The-color-change-crayon.htm

Yup, LarryD. I'm getting new corneas in a few weeks, then the mists might clear. Next is a new or reconditioned brain, can't find such on Ebay though!!

I think the detail of replies has gone beyond my original point. All that was bugging me was that the method of obtaining resistors through suppliers seemed to me to have changed but on reflection it is more than twenty years since I actually PURCHASED them if you see what I mean. I’m 78 and the fact is that the frequency of my designing and producing PCBs has vastly diminished so I have relied on my stocks of resistors built up around the time the world began (30 years ago that is!). It’s my aching brain that’s the problem I think!

Now SMD has crept up on my awareness which I find intriguing but the topic of reflow ovens is really suited to another thread isn’t it?