Introduction
Many of the parts we'll be dealing with in this challenge are surface mount. Therefore, it seems wise to me to blog about preparing for the surface mount board build. I have chosen a few items as part of the budget to prepare for this. Note, I am not endorsing these parts, as I have not used them yet. I will be purchasing them and I will comment on how I like them in a later blog post. Why talk about dealing with surface mount? Suppose you are working on this challenge and you've decided to use the TI HDC1000 temperature and humidity sensor, which looks like a good sensor at a great price. Sensirion modules are at least twice the price for the same resolution. I've shown the image of the HDC1000 from TI's website below in Figure 1.
Figure 1: Texas Instruments HDC1000.
This chip measures 2.04 mm x 1.67 mm. Grab a ruler and look at it, this chip is TINY. So, to deal with tiny stuff we will need the appropriate tools, which is why I started this blog series on surface mount soldering.
Parts
So, here are the basic parts I would choose considering we have a $500 budget. I prefer to work under a microscope, but we'll see how things turn out. C'est la vie.
A Heat Gun or Hot Air Station - TENMA 21-11410 HOT AIR DESOLDERING STATION TENMA 21-11410 HOT AIR DESOLDERING STATION
A Preheater - TENMA 21-10135 MINI SMD PREHEATER, 100-350 DEG C TENMA 21-10135 MINI SMD PREHEATER, 100-350 DEG C
Dental Picks - DURATOOL 21-13885 DENTAL STYLE PICKS DURATOOL 21-13885 DENTAL STYLE PICKS
Tweezers - AVEN 1340 PRECESSION TWEEZER, 120MM AVEN 1340 PRECESSION TWEEZER, 120MM
Solder Paste - CHIP QUIK SMD291AX10 SOLDER PASTE, 63/37 Sn/Pb, 35G CHIP QUIK SMD291AX10 SOLDER PASTE, 63/37 Sn/Pb, 35G
LED Lamp - DURATOOL 21-10255 LED MAG LAMP DURATOOL 21-10255 LED MAG LAMP
Precision Knife - XCELITE XN100 PRECISION KNIFE XCELITE XN100 PRECISION KNIFE
If your budget is running tight, you could exclude the preheater. The preheater just makes it easier to solder because it holds the board for you and provides heat from below while you use the hot air station above. If you have a stand that can take the heat, you could solder the board with just the hot air station. If your eyes are really good at focusing on small things you could exclude the lamp as well.
I've gathered the photos of the products from around the internet, but mostly Newark. I've also added a blurb about each piece and for which task it is used. Unless indicated these pictures come from the Newark website.
The Hot Air Station
This is the main tool. You definitely need this one or a heat gun. Something has to be used to heat up that solder paste for the QFN (Quad Flat No-Leads) and BGA (Ball Grid Array) packages. We could get away with an iron for SOIC (Small Outline Integrated Circuit) or QFP (Quad Flat Packs) but the QFN would be really, really tricky to do without hot air. You could use a toaster oven for the initial soldering, but you need the hot-air station to rework the board.
The LED Lamp (Picture from MCM Electronics, part supplied by Newark)
As I get older, my ability to see fine items gets worse. If you are young enough that this is not a problem, a simple desk lamp may suffice. Be wary though, some of these parts are quite small. When I do surface mount components, I use a microscope. These magnifiers are typically 2.5X magnification, so it's a bit of a gamble. At $26, it's not very risky though.
Solder Paste
You'll find two basic containers for solder paste. The syringe and the jar. If you are having a stencil made, you can get a jar. Try to get one that comes with a spatula or squeegee for applying solder. Most likely, since you're prototyping, you'll want the syringe. This allows you to deposit solder directly onto the pads of the PCB.
Dental Picks (Picture from MCM Electronics, part supplied by Newark)
These tools are for positioning the lCs and for scraping away any solder balls that do not liquify in the heating process. They're just really handy for surface mount work.
Tweezers
These are for placing the components onto the PCB and sometimes holding components while you hand solder something. You can use these for positioning as well if you don't want to use the dental picks.
The Preheater
You can see the board holder on the top of the preheater in the picture. The preheater heats the board from the bottom. You set the temperature just below the melting point and use the hot air to finish the job from the top. You can get away without the preheater, but you might not like the look of your board when you are done. Components like Tantalum capacitors and some ICs will "bake" without using the preheater.
Precision Knife (A.K.A. X-acto knife)
Who couldn't use a knife like this when prototyping?
Final Thoughts
That's it for this blog post. I'll be designing a board in this challenge, so the next blog posts will likely be about surface mount soldering techniques. Sometimes it's difficult to learn without doing. I've been working with RF and surface mount components for about eight years now and I'm still learning. If you're designing a board for this challenge, just consider how small the components are before deciding on a part.
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