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Questions relating to designing PCBs
By slide
#30483
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
By Azoore
#30485
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.
By jasonharper
#30486
slide wrote:but 10uF isnt available as 0402 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.

All of your other capacitance values should be readily available in 0402, I just hope you weren't planning on soldering them by hand...
By slide
#30487
whoops, 10uF should actually be 10nF! I'm going to build the example circuit for the nRF24L01.
By emf
#30488
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.
Last edited by emf on Thu May 24, 2007 8:36 pm, edited 1 time in total.
By rglenn
#30497
NleahciM wrote: Both are solderable by hand with just an iron.
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.

Also: order extras for when some tiny parts wind up lost on the floor. It will happen.
By RonnyM
#30507
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
By Philba
#30542
for those of us building cell phones or spy mics...
By tarun
#30578
rglenn wrote:
NleahciM wrote: Both are solderable by hand with just an iron.
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.

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.
By busonerd
#30579
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
By propellanttech
#30597
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
By mtwieg
#30599
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.
By busonerd
#30622
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
User avatar
By bigglez
#30625
propellanttech wrote: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.

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