Surface Mount Soldering Kits

Evil Mad Scientist The 741SE Discrete 741 Op-Amp

Assemble and ready to go

In my previous post I wrote about the QRP-Labs QCX-mini amateur radio kit which only has through-the-hole components to be soldered by the enthusiast but had problems with some of the surface mounted op-amps and my desire to learn how to remove those surface mounted devices (SMD) and install new ones. To learn how to do that I bought a handful of kits to practice on.

First up is the Gikfun DIY SMD SMT Welding Practice Soldering Skill Training Board Ek7028 which was a pretty great kit to assemble, when finished it isn’t much to share as it just blinks some lights in the middle of the circuit board, but it comes with 124 LEDs, capacitors, and resistors and 2 ICs to solder to the board. I even practiced correcting “tombstoning” and removing then replacing components. The 1206 and 805 sized components were pretty easy, I did those with my Hakko 888 fine tipped soldering iron, but the 603 and 402 components I used the hot-air rework station.

The Gikfun kit was a challenge but it also gave me a lot of confidence to get the fancier SMD kits assembled.

I purchased 2 kits from Evil Mad Scientist, The 555SE Discrete 555 Timer and The 741SE Discrete 741 Op-Amp which when finished make great desk toys/conversation starters and can even be used to make working circuits.

I actually assembled the 555 Timer first, I followed the provided instructions by installing components as they were stored in their packaging a few at a time. I applied a dab of Chip Quik SMD291AX REWORK SOLDER PASTE 5CC 63/37 NO CLEAN SOLDER on each pad and then used the hot-air rework station to melt the solder. It worked really well and by the end of the kit I was full of confidence.

At the top of the page is the completed Op-Amp and below you can follow along with the steps I used to assemble it. Unlike with the 555 Timer I applied paste to the entire board by hand, a solder mask is not supplied with the kit.

solder paste on a circuit board

Solder Paste Applied

Then I placed each component. The solder paste did a decent job holding the components in place, I developed a rhythm of getting the component onto the board with a bit of it stuck in the paste then maneuvering it into its correct position followed by a tap on the top to set it down into the paste.

components in paste

Components in the Paste

And finally, I moved the hot-air rework station’s wand across the entire board moving quickly at first to warm up the entire board then more slowly and finally concentrating on each component until the solder flowed.

soldered components

Soldered Components

The finished kit puts a big smile on my face, I am very excited to do more SMD kits.

Soldered Components Close-Up

Soldered Components Close-Up

The only thing that bothers me about using the hot-air rework station and soldering paste is that the soldering paste has an expiration date. I have been told that it is good for about 6 months and if refrigerated can be used up to a year, but after that it doesn’t work as expected. I have solder wire that is 30 plus years old and works as well today as it did the day I bought, that won’t be the case with solder paste.

QRP Labs QCX-mini

QRP-Labs QCX-mini

Assembled QRP-Labs QCX-mini with dummy load and replacement op-amps.

The QCX-mini is a continuous wave (CW), think Morse Code, ham radio kit that transmits and receives on one band only at around 5 watts. I had been waiting for the release of the QCX-mini kits for a while and was able to order one as soon as it was released. I also bought the aluminum case and the 50-ohm dummy load.

The kit was pretty straight-forward to assemble, I am very proud of my soldering on this kit, it is the best I have ever done, but…

When I was done and went through the alignment process it didn’t work. I went off to the QCX forums to see what I could do. Turns out there is an issue with the pre-installed surface mount op-amps used in some of the early kits. The solution is to check the voltages of each op-amp, there are quite a few of them, and then replace the ones that aren’t working as designed. Also using an oscilloscope is recommended to collect more troubleshooting information.

I bought a 10 pack of op-amps directly from China on eBay, they arrived a lot faster than I expected.

I bought an inexpensive scope for Ali Express, the DSO FNIRSI-150 Digital Oscilloscope full assembled with P6020 BNC standard probe, along with an extra probe. I’ve turned it on but haven’t learned how to use it yet. I am hesitant to use the scope as some members of the forums have shorted out their radios breaking a lot of components in the process, the surface mount components are so small I can see myself doing that.

This also led me to buy a hot air rework station. After a lot of research I bought the Sparkfun Hot-Air Rework Station – 303D. I chose this unit because I trust Sparkfun and they stock replacement heating elements for it.

But I have never soldered surface mount components or used a hot-air rework station so I bought a handful of SMD kits to practice on, there will be blog posts in the future about those.

As of right now I have a non-working QCX-mini which I am pretty bummed about. QRP-Labs is in the process of making some design changes to the radio and my plan is to buy one of the new kits when they are available instead of trying to fix the one I have. Even though the radio doesn’t work I am not upset about it, I believe they are pushing limits and doing their best to create a great kit experience and a great radio for us.

I look forward to getting my hands on the next version of the QCX-mini and using it to make a lot of contacts with it.

Nikki and Bob Series by Jerry Boyd

After finishing all of the books Nathan Lowell has written so far I tried some books recommended by my Kindle, or more correctly “Advertised” on my Kindle, and what a total waste of time. I find it hard to describe just how BAD those books were. But then I found Bob’s Saucer Repair by Jerry Boyd.

There are currently 14 books in the series, I am on book 9 and reading through a book every other day or so. These stories are science-fiction light with lots of humor, a fast pace, not a lot of depth, and a ton of characters.

I highly recommend these books to anyone looking for some fun and light science fiction.