Long time schematic reader, first time schematic writer. I have a prototype of several adafruit boards wired together with lots of 3.3V and gnd jumper wires all over the place, and I would like to combine those into a single PCB and have JLCPCB assemble a few for me, as a hobbiest exercise. Not really optimizing for size or cost. So bringing up the adafruit EAGLE schematics and attempting to replicate them in a new kicad 9.0 schematic. Haven’t gotten to the PCB part yet.
For the more complex components I am using the part numbers from the eagle schematic and most of those so far seem to be in the kicad global symbol library. But my question is simple components like resistors and capacitors. I can add resistors but I don’t know what footprint to select. Is there a standard “normal” footprint to select for resistors and capacitors? Do I need to specify a part number for these or just let JLCPCB use whatever is on hand that matches the value?
adding to this: if it should be SMD and handsoldered: 0805 is the default
if not, you have to decide how small you can go and still hit the voltage/current rating. I always use 0402 for the 100nF caps for example
Just to add to the confusion: I think I agree with many others in that I do not like to use 0402 or smaller for hand soldering.
For resistors I try to standardize on 0603 and 1206. Higher power or higher voltage can require larger packages. I will also use 1206 where I want to jumper over a track. ( I am conservative with this. A 1206 can probably jumper over 2 or 3 tracks and an 0603 can probably jumper over one track.) There is nothing wrong with 0805 resistors, but for keeping parts in my lab I don’t see the need for the extra size between 0603 and 1206.
For capacitors, the minimum size is dictated by capacitance, voltage, and dielectric stability. NP0 capacitors are the most stable with voltage, time and temperature but they also provide the smallest amount of capacitance in a package. Typically I will also use X7R and X5R “high K” dielectric capacitors.
Capacitor dielectric stability is a big deal. You can get something like a 22 uF 25V X5R capacitor in a 1210 chip. But when that capacitor has 25V applied, the actual capacitance might be 5 or 8 uF… Similarly on these “High K” dielectrics the capacitance falls off with age (after soldering into the board) and with variations in temperature.
Not really. ESR and ESL are a bit bigger for larger capacitor packages, but that will probably not matter to you. I used 0805 for years until my boards got that many components on them that they started to get too large
Adding to this: If you use X5R/X7R it is best to make sure that the voltage rating is way higher than the applied voltage. A 10V rated cap with 10V applied to it loses more than half of its capacitance!
Also 0603 is still fine to solder by hand, I agree with you. I personally started with 0805 because they were available everywhere and therefore sticked to that single size
In 90s we moved from THT to 1206 (were hard to buy). When 1206 were easy to buy we moved to 0805 (were hard to buy). When 0805 were easy to buy we moved to 0603 (you know - were hard to buy ). All that before 2000. Then for years we stop moving.
Some of our PCBs are hand soldered. I see no problem with hand soldering 0603 (on standard footprint (not special for hand soldering)) even since 15 years I need glasses to read and magnifying glass to solder them.
When (around 2010) we started to use AtXmegas that have many VCC/GND pin pairs around their case we decided to use 100n 0402.
So my current standard is 0603 with only 100n 0402.
Hand soldering 0402 is for for me rather hard but possible.
You should expect some bugs (even crashing) in V9.0.0.
For play with all new possibilities V9 is correct choice. To make and order PCB with no problems I would use V8.0.9.
Yes I lose about half of them! They can disappear in the solder at the end of the solder tip.
Unfortunately there is no easy answer to standardizing on chip size. With some ICs the bypass capacitor needs to be placed in very close to the IC in order to minimize stray inductance (ESL) and have it work correctly. But that small size will not provide more capacitance at voltage in a capacitor or power in a resistor.
You do not want to drive a school bus to go grocery shopping or use a compact car to carry 30 people.
If you ever saw the movie “Jaws”, “You will need a bigger boat.” But that bigger boat will not fit in your garage.
If you’ve got the room to use 1206/1210, do so. It’s really nice not having to use a microscope to probe or solder things.
Once those don’t cut it, suck it up and make the jump to 0402. 2.4GHz+ RF pretty much requires 0402 (0603 mostly works–until it doesn’t and it will do so intermittently). Hi-density IC packages all basically expect 0402 capacitors for bypass.
I used to work with a company that “standardized” on 0805 and it wasn’t worth it. We either had tons of room and could have used 1206/1210 which would make things easier, or we wound up with lots of 0603/0402 exceptions and had to use a microscope anyway.
This seems like an “all or nothing” approach which does not sound good to me. There also may be some price penalties if all you need is 1 nF 50V and you get it in a 1206 or 1210 chip.
I suppose there is a lot of room for difference of opinion here. My hands have never been very steady, and I am 73 and have worn bifocal eyeglasses for years now. I routinely place 0603s on a minimum sized 0805 footprint using only my bifocals and a good light over my bench. I think that going with 1206s or 1210s for all of those will often make life more difficult.
Very often you have a bunch of passives crowded around an IC. Think of a dozen cattle feeding out of one shoebox. It will be easiest if they are rats, but even sheep will fit a bit better than the cattle.
Sometimes it may well be necessary to use 0402 or 0201. But I would minimize the first and absolutely refuse to work with the second.
There are other considerations too. If you are getting it assembled, eyesight is the JLCPCB’s PNP machine’s problem (don’t know why they discriminate against NPN machines ). But taking say a 1k resistor, here are the voltage ratings, power capacities, and prices, all basic parts:
If the difference between 0.2 cents and 0.02 cents per part is important, I don’t think the designer needs our advice anymore.
If someone is assembling the board in volume, the size probably matters and I’ll use 0402. And, sure, there are chips where you need 0402 for breakout or sufficient bypass.
However, if it’s a low-volume board (<100 units) with a high probability of rework, 1206/1210 is hard to beat. Most test point loops for grabbers are around the size of 1210 footprint. Stripping a 30 AWG wire for too small a pad requires a really good wire stripper that hasn’t been used too much–1206 is nowhere near that finicky. “Tenting” two 1206 resistors is pretty easy–doing the same thing with smaller footprints requires quite a bit of experience and a really good soldering iron. Air gunning a small component may send it or a neighbor flying while that will never happen with 1206s. It’s a lot harder to burn a 1206 LED with an iron than something smaller. 1206/1210 is a lot more forgiving of “bad” soldering joints. And so forth.
And while it’s true that there are no “right” answers here, I have found that recommending and using 1206/1210 simply sets beginners up for a lot less frustration.
Your mileage may vary. Offer void where prohibited. This advice is worth what you paid for it. etc. etc.
Another way to look at this is… What do you use.
It’s less footprint and more the part. Keeping local stock of 1000 0603,100nF, 10V is easier than 100off of subtle differences
Flattening tour BOM across all your designs is well worth it in your stock management.
Otherwise I agree with what is said here… 0402 is great for automation and 0603 is the comfortable limit for hand mod. Typically my packages follow the voltage and that is why I still use 1206 resistors
If you let assemble the board, you need to specify the size. 0603 is one of the very common sizes. You won’t have problems with your assembler.
If you want to assemble the boards by yourself: Well, as you have already read, it depends. On your soldering skills, your soldering equpment and your eyesight. You won’t have fun with your $3.99 30 W iron from Alibaba trying to solder 0603. And you won’t be able to make fixes to your board (I NEVER EVER make ANY errors!)
Personally, I feel comfortable with 0603 and that’s what I have here. And some 1206 for more power or higher voltages.
When it comes to the price of passive chips, I was more focused on capacitors. This is a comparison of 100 pieces (cheapest part at DigiKey of 100 nF X7R, any voltage and tolerance that pops up):
So the price of the 100 pieces on tape is $0.48 versus $7.15 I think that difference is enough to persuade most of us to use the 0603 where it is adequate.
NOTE: I have not looked at twisted chips for warped boards (or warped minds.)
If $1.50 matters that much to you, sure. I just find that other considerations normally apply that are worth more than the $1.50.
(Side note: One of those considerations used to be that the voltage rating on 1206/1210 was vastly better than small footprints at the same price. New technology, however, seems to have rendered the DC Bias differences moot–a capacitor now has the same DC Bias characteristics at the same voltage rating regardless of footprint.)
). All that before 2000. Then for years we stop moving.
). But taking say a 1k resistor, here are the voltage ratings, power capacities, and prices, all basic parts:
