I’m having trouble finding the right packages for components i need. Apparently digikey doesn’t have some of the caps (havnt looked for em all, but 10uF isnt available as 0402 package) Could anyone recommend somewhere I can get the following devices with a 0402 footprint?
Caps: 1.0pF, 1.5pF, 12pF, 1.0nF, 2.2nF, 4.7nF, 33nF, 10uF
Inductors: 2.7nH, 3.9nH, 8.2nH
Digikey and Mouser have all of these except the 10uF cap. I don’t think you’re going to be able to find such a high capacitance in that small of a package.
Where did you get the idea that this is even physically possible? It's miraculous that they can make 10uF caps as small as 0603, which is over three times as much volume as a 0402.slide:
but 10uF isnt available as 0402 package
All of your other capacitance values should be readily available in 0402, I just hope you weren’t planning on soldering them by hand…
whoops, 10uF should actually be 10nF! I’m going to build the example circuit for the nRF24L01.
This got me flipping through my catalogs too. I’m trying to work my way through a DSP book and I’m hungry for diversions.
I know this isn’t what slide needed, but AVX actually makes a 10uF 0402 capacitor, but it’s only rated for 2V. Probably costs at least its own weight in gold too…
0402 is really really small. I hope I never meet an 0201.
Both are solderable by hand with just an iron.emf:
0402 is really really small. I hope I never meet an 0201.
I think that's only for people with *spectacular* motor control and vision. Beyond 0603, I want at least a magnifying glass, a nice set of tweezers, and preferably a stereo microscope. I really, REALLY don't want to touch 0201.NleahciM:
Both are solderable by hand with just an iron.
Also: order extras for when some tiny parts wind up lost on the floor. It will happen.
I use a Laser welder with a 20x microscope at work(Only 30K!). The 0201s are no problem to weld, it’s the holding in place that gets difficult!
Ron
for those of us building cell phones or spy mics…
rglenn:
I think that's only for people with *spectacular* motor control and vision. Beyond 0603, I want at least a magnifying glass, a nice set of tweezers, and preferably a stereo microscope. I really, REALLY don't want to touch 0201.NleahciM:
Both are solderable by hand with just an iron.Also: order extras for when some tiny parts wind up lost on the floor. It will happen.
0402 are absolutely no problem to solder by hand. The technique is identical whether its 0603, 0805, 1206, etc.
0201 are not the easiest thing, but more than do-able by hand as well (in small numbers ;-)). You do need a microscope though.
Let me also mention - the eagle 0402 footprints are not correct for reflow soldering! [Just to forewarn you if you’re doing something that will eventually go production]. They’re also far too big for the actual space required.
Cheers,
–David Carne
Dave,
I reflow and never have had a problem with 402’s footprint with reflow.
I saw a reply about tombstoning…but never had one to raise on reflow.
Could you point out the library of the suspect footprints?
Thanks,
James L
Even the less tiny footprints (0805s) are much bigger then necessary for reflow. Good to have some extra area for hand soldering. I think I’ll just shrink them all a bit when I move to reflow production.
it was the 0402 std resistor footprint in the rcl library. The issue came up at a pro production house.
I don’t know if its been fixed in a more recent vers of the library.
Cheers,
–David Carne
propellanttech:
I reflow and never have had a problem with 402’s footprint with reflow.I saw a reply about tombstoning…but never had one to raise on reflow.
Could you point out the library of the suspect footprints?
James, Dave, et al,
Can you bring me up to speed on ‘tombstoning’?
I assume it is where an SMT part tips up while the solder is liquid.
What causes it?
I’ve recently moved to hot air and solder paste assembly (very low volume, but better than soldering by hand with an iron).
The only problem part I have is a 1206 LED. I suspect I have applied too much paste, and the molten solder floats the part. This is only an issue when the LED dome doesn’t sit the right way after the solder sets.
In EAGLE there appears to be different footprints, can I assume these apply to different solder types or solder methods?
For example: C1206 and 1206K (Kemet?). R1206 and 1206W (wave?).
For some parts I’ve used straight from the EAGLE libs the pads seem too small to apply a soldering iron. Either the part boby covers the pads (SMT trimmer caps) or due to the bulk of the part (large can electrolytics, shielded inductors) they take a lot of hot air to solder at all. For these I prefer to ‘convert’ the solder paste with the MetCal and not over heat the board with hot air.
Comments Welcome!
the float, in conjunction with a solder mask makes for automatic alignment of parts. especially for ICs. This is an issue for home made boards with out a solder mask.
Peter,
Yes you are correct…tombstoning is the process that a capacitor, resistor, or other similar component either raises to one end, or rolls onto one side (although this is very rare…the side roll).
This is usually from them smt pad being larger than the component soldering location. The surface tension of the molten solder will pull harder on one end than the other…resulting in a tombstoned part. This usually happens from more solder than required to attach the component to the board. A smaller pad would require less solder…and the surface (smaller quantity) tension of the molted solder doesn’t lift the part.
This is not a total explaination…because a larger foot print usually extends past the component end(most hand solder pads are longer…but not much wider)…this added area is leverage for the molten solder to help raise the component as well.
You should know that when hot air soldering…turn the air volume down as low as you can get away with. The air flow will provide an addition lifting sorce for the parts. This could result in some very frustrating moments. I have done some rework to my boards…and have found out the hard way.
I can’t say about the footprints…I was asking to know if there were different ones for reflow or for hand soldering.
I’m batch reflowing…so I’ve not had any tombstoning while reflowing total boards.
I’m also very careful about placement…make sure your parts are pushed down into the solder…don’t go crazy…but make sure they are in contact with all their landings. This helps prevent one side lifting. (But this is theoretical…and my opinion)
James L
Philba:
the float, in conjunction with a solder mask makes for automatic alignment of parts. especially for ICs. This is an issue for home made boards with out a solder mask.
Greetings Philba,
Ah yes! I have seen the float when the paste converts. I’m “dotting” the pads with a hand syringe, so I’m not able to control the volume of paste. (I hope to add a pneumatic dispenser in the near future). For good soldering (i.e. no opens or shorts) it takes a very small amount of paste per pad!
If I use an iron, even a very small tip, the iron removes a little solder and can leave a spike. With hot air (and presumably also with IR reflow) the heat is by non-contact and the solder “puddles” around the contact and pad - assuming that a flux provides good surface wetting.
Comments Welcome!
propellanttech:
This is usually from them smt pad being larger than the component soldering location. The surface tension of the molten solder will pull harder on one end than the other…resulting in a tombstoned part. This usually happens from more solder than required to attach the component to the board. A smaller pad would require less solder…and the surface (smaller quantity) tension of the molted solder doesn’t lift the part.
Greetings James,
Good explanation. So to get controlled paste on the pad (and assuming the pad is the right size) we use a stencil?
propellanttech:
You should know that when hot air soldering…turn the air volume down as low as you can get away with. The air flow will provide an addition lifting sorce for the parts. This could result in some very frustrating moments. I have done some rework to my boards…and have found out the hard way.
My equipment is primative - a Weller 6966C heat gun that I bought (used) for applying heat shrink. I recently discovered it can melt solder, and use it by hand in small circles around three or four 1206 parts to do the conversion of paste solder. So far I’ve only used 1206 size, some other parts as noted earlier, and some SOIC28 or TQFP32 devices.
By manipulating the height of the nossel by hand I can direct the air down on the parts, and as you pointed out, the side blast can move the adjacent parts off their centres.
propellanttech:
I’m also very careful about placement…make sure your parts are pushed down into the solder…don’t go crazy…but make sure they are in contact with all their landings. This helps prevent one side lifting. (But this is theoretical…and my opinion)
I’m dotting all the pads with paste on one side of the PCB, then placing the parts with tweezers. I try to get them all lined up and seated on the pads. I was tacking pin 1 of the ICs but now I feel this is not needed (the entire IC can pull to the pad centres if solder on all pads is molten).
Thanks for sharing your experiences! I would never have imagined doing this level of assembly at home. The results have been very good so far, although I seldom make more than three or four of each design and can’t readily justify tooling or sub-contractor involvement.
Comments Welcome!
Peter,
I use stencils exclusively…I always have a huge number of parts on a board…and those boards will eventually be produced in large quantities.(by me)
I’ve not tried to place the solder by hand. I’m looking at a pick and place now…and will probably have one by the end of the year. I plan to have a dispenser on it…to do away with stencils all together.
I will probably offer assembly services for surface mount boards.
I’m not planning on wave though…so any through hole parts will be hand soldered.
At the moment I’m using plastic stencils…which tend to be thicker than needed…so more solder is being placed than needed…but it still works very well. I have also gone to the vacuum method of holding the stencil in place…which was a stroke of genius from someone else on the forum.
I actually heavily modified a very nice toaster oven for reflow. I hated to do the modification, it was a very nice toaster.
But it works perfectly. My boards come out perfect everytime. It even has a fan inside for hot air circulation. (hot air convection oven)
It has taken me some time…but I really have the method down to a science. I did have one board that was over “cooked” when I started. The traces change color slightly. The board worked ok…but you could tell it was just slightly raised too high in temp (or time).
I will warn you about the heat gun method. Becareful…heating just part of the board can cause it to bow or warp. This is not ususally a problem…but can be for some projects.
James L