Re: SMD Group Build

Ken KM4NFQ <km4nfq@...>

Hello Jack, W8TEE,

The Revolving LED SMD Practice Kit was my introduction to soldering SMDs.
So it was also my introduction to a Solder Paste Syringe, and application needles.
I have a heavy thumb (ham-fisted, I am).
A gentle squeeze on the syringe produced an on-going stream of solder paste.
I thought it would never stop coming out!
Another thing is, the needle was a mess to clean up afterwards.
I used a Q-Tip and a wire to clean it up as best as I could.
So my first experience kind of soured me on using the needle applicator.
I wanted more control over how much solder paste came out of the syringe.
So what I did was to make a screw-controlled applicator.
I don't use the needles at all. The solder paste comes out very slowly.
As it comes out, I use a pointed dental tool to get a small gob on the point.
Then I apply it to a pad with the dental tool.
Every once in awhile I give the screw a slight twist.
This works great for ME. YMMV.

There is a cap that screws over the end of the syringe, which I replace when I finish applying solder paste.
The scrap-wood prototype worked so well, I never made a finished product.
I call this tool my Solder Paster Extruder.

I found my 'Reflow Oven' at the Goodwill Store (re-purposed Toaster Oven).

I calibrated it with an old kitchen oven thermometer which is accurate.
I made marks on the dial, then checked the temperature for each mark.
In actual use, I turn it to my 3rd mark and wait for the temperature to get to 200degF.
Then I turn it to my 6th mark, and the temperature goes to 350degF.
I turn the oven off, open the door, and let the PCB cool down.

I got my SMD Tweezers, and Hot Air Gun, from eBay, as well as the SMD Practice Kit.
Since then, I have sourced 0805 SMD resistors, capacitors, and ICs from Mouser.
Most of the other tools I already had in my studio.


On Thu, Jan 25, 2018 at 9:57 AM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:
Mornin' Ken:

You're right, and I may have glossed over this idea too quickly. This might be a great way to get them to try at low expense and without insulting their fabrication abilities. I do have everything you suggested except the skillet. That might be the club's next project after the frequency counter.

Jack, W8TEE

From: Ken KM4NFQ <km4nfq@...>
Sent: Thursday, January 25, 2018 6:24 AM
Subject: Re: [BITX20] SMD Group Build

Hello Jack, W8TEE,

The SMD components are not the only thing that you might need.
Also look into:
Solder paste in a syringe with application needles (~ $20+ for 35gm)
Toaster Oven or Electric Skillet for melting the solder onto the PCB (find in a thrift store)
Tweezers (for manually placing the components)
Hot Air Gun (for removing parts)
Magnifying Loupe (for inspecting your work)
Desoldering wick (removing solder bridges from ICs)
Soldering Iron with fine tip (rework tombstoned parts)

The revolving LED kit is a challenge to build for beginners.
$3 - $4 per person in the group. All the components are in the kit.
The circuit itself is in the middle of the PCB.
But there are three columns of practice components on each side.
1206, 0805, 0805, 0603, 0603, and 0402 sizes are included, so you get an idea.
The practice columns are not connected to the revolving LED circuit.
The revolving LED circuit has a 555 and a CMOS 4017, as well as
transistors, diodes, and LEDs, so you get a variety of SMDs to work with.

In my recent and limited experience, making an SMD project consists of:
Identifying the components.
Applying solder paste evenly to the pads.
Placing the SMD components on the solder paste.
All the components are soldered at once.
Clean the flux from around the components (Isopropyl Alcohol & toothbrush)
Smoke test.
Only part of my circuit worked, but I got some SMD soldering practice for $3 - $4.


On Wed, Jan 24, 2018 at 8:27 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:

We have a small group of local hams who enjoy building stuff, yet most are scared to death of SMD parts. Our last build had 29 do the build which is about half of our group. What I'd like to do is put together a small SMD project and have 30 or so boards made. (I have no idea what a good starter project would be.) If anyone has done this, are the board costs less than thru-holes boards? Also, are Mouser and Digikey the likely source for large (e.g., 1206) parts or do you know of a better source.


Jack, W8TEE

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