Hey guys, I haven’t use SMD component yet. Currently, I started my design with DIP Components. So, I am not having enough knowledge about SMD Packages but as per instructions from my guide, they suggest me to use 0804 SMD Packages. But still one doubt in my mind why to prefer 0804 packages instead of others. Can someone clarify my doubt??
0805 is the smallest SMT resistor that is still easy to solder.
0603 is also still quite doable for most people, but it’s getting a bit smallish, and therefore more difficult.
0402 and smaller gets hard without very good equipment such as stereo microscopes. (10x magnification is enough)
The bigger packages such as 1206 are also easy to solder, and sometimes have the advantage that you can route 2 unrelated tracks under them. Sometimes these bigger packages are needed because of power dissipation, for example with low value shunt resistors.
0805 also has the benefit that it fits quite well on vero board, or on anything with a “standard” 100mil distance. 1206 is hard to fit on vero board because it’s too small.
A good way to start is to buy a “SMD sample book” from Ebay / Ali / China. You can get books with complete E12 range, and 50 or 100 pieces of cut tape in each size you want for around EUR25.
You can also buy these books with an transistor or diode assortment. Each shop has different transistors in them, so search for the datasheets to get an idea of the spread of the components.
Then there is technique and tools.
For hand soldering I prefer to first put a dab of solder on all the right pads, then exchange solder for tweezers in my left hand, place all components and solder them with the solder already on the PCB, and then solder the left side. Good tweezers are mandatory. With bad quality tweezers you can not pick up components reliably.
MikesElectricStuff has a nice overview with tips for SMT soldering, but there are also many other tutorials on youtube.
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0804 (it’s 0805!) are large enough to easily hand solder and lets you route a 10 mill track between its pads
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BTW the numbers are the dimensions in 1/100 th of an inch, i.e. 0805 = 0.08 x 0.05 in. In metric the profile is 2012. So you can see that it’s smaller than a grain of rice. I once dropped one on the floor and it’s a miracle I found it.
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0805 is my go to if other people may have to assemble them, I’m personally very comfortable with 0603, passable on 0402’s and mainly struggle with 0201’s,
Key points are keep the spacing to the default courtyards at minimum, and increase based on how well you can handle precision,
I use gel flux to cheat quite a lot, pre tin the pads, put a small dot of gel flux on the package locations, put the part in place, the flux mostly keeps it held in place, then heat with low airflow with the hot air gun and in most cases it will self align onto the pads, occasionally needing a nudge to get the second pad to stick,
I would say for a beginner, work off at least a 2mm gap between fab layer outlines on SMD components, I work off a 1mm, and its just on the edge where sometimes long rows of components will be a little annoying to separate from there neighbor. If your really not confident that 3mm,
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It’s certainly easier than 100 x 0402. Trust me, I know 
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thank you so much for detail information @paulvdh.Its helpful.
Imperial size 0805 are easy for most people to hand-solder, in my experience. You can use the hand-soldering footprints in the Kicad library to make things even easier. Nearly all parts are available in 0805 size, unless you are laying out high frequency radio stuff you’re probably ok.
I’m now going to 0603 because I find they’re still fairly hand-solderable, but slightly more difficult.
You can use a mix of sizes, and use bigger sizes for some things if it makes it easier, e.g. 1206 for capacitors or led.
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I find 0402 too fiddly even with a stereo microscope, so 0603 and 0.4mm pitch pqfp is my limit
0603 is the smallest size resistor with the value on it too
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thanks for response @MarkR.Its helpful.
I have had unsteady hands all of my life; mild “essential tremor”. I am 68. When SMT was introduced, I was intimidated by it. But nowadays I can hand solder 0603 chips routinely. One recommendation is that I like to use a relatively small 0805 footprint for my 0603 chips.This provides more room on the pad for the soldering iron tip.
0402’s? No. I have done them, but half the time I lose the chip in the drop of solder on the end of the soldering iron.
In my opinion, SMT is often easier than thru hole because you do not need to worry about holes filling with solder. I think it is much easier to change values of an 0603 chip on the board than to change values of a 0.25W thru hole resistor. So dive into it with courage. I do recommend a desolder tweezer. Two soldering irons can also work to heat both pads at the same time.
In my lab I stock 0603 and 1206 resistors but not 0805s, with a few exceptions for milliohm values. If you have a small 0805 footprint, it might be easier to solder an 0603 chip onto those pads than an 0805.
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I would say once you get comfortable with hot air, you start looking at your PCB’s with a twisted sense of size, everything just ends up looking stupidly large, and you may get into a habit of packing things into smaller and smaller sizes
Makes for some fun, but annoying when you then realize the PCB needs to be 5x bigger for the mounting holes
E.g. 0201 10nF capacitors just so perfectly fit across 0.5mm QFP package pins, but it is not an easy task to place them or rework them if you ignore the courtyards, if you follow them, in most cases things will be easy to assemble with sharp tweezers,
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That usually requires a paste stencil, too. I have experience only with steel stencils, but I know it can be frustrating to learn to use it. 0402 can be soldered with an iron and the stencil isn’t needed. 0201 may barely be possible with an iron, too, but only with a good microscope (and good component placement as you said), and I don’t recommend it. Additionally it may be surprising that going to 0201 from 0402 saves relatively little space. With those sizes the tracks and especially vias take quite much of the space in the board and 0201 is worth it only if you can go for really thin tracks and smaller than standard vias – and actually really need all the space you can get.
As for the original question – why not just go after their recommendation. I think the opinions in this thread confirm that suggestion. The question of 0402 vs. 0201 is interesting in its own right, but not relevant for that.
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Not really, just a lot of stubbornness,
Pre-tin pads, add a dot of gel flux and poke stuff when it doesn’t self align correctly,
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I used to use for it one 110W trafo soldering iron and one soldering iron with sharp tip. When I have the element (typically 0603) taken out of PCB and between then I switch off the trafo soldering iron and the element stays at it and it is cold at once. Then I take tweezers to my second hand and take the element off the iron (by switching it on for a second).
In past (when I didn’t had those iron with sharp tip) I have also done special shaped wires used with trafo iron to heat both ends of elements like 0603 (I had also special shapes (with one leg bigger) for SOT23 and SOT323).
We switched from TH elements to 1206 and than to 0805 and then to 0603 and we finished that process in previous century. Now we use mainly 0603 and some 0402 (mainly 100n blocking capaciotors to place them close to IC pin pairs (VCC+GND) and to not block tracks from next pads.
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Many KiCad libraries have alternate hand solder footprints with bigger pads that allow the iron to touch the pad
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But that way I don’t get to re-invent the wheel! Seriously I have dimensions that I have used previously with other pcb layout software, and it is not a big deal to make my own footprints for these SMT parts. I only need to make each one once. Another footprint will fit anything from 0603 up to 1210 for hand soldering.
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