SMT Component Questions

Comments

• Newzed Posts: 2,503

  2005-09-13 17:04 edited 2005-09-13 17:04

  Use SOIC .050 pitch for the chips.· SSOP chips are very difficult to solder.
  
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• Bean Posts: 8,129

  2005-09-13 17:17 edited 2005-09-13 17:17

  Nick,
  I have settled on 0805 for resistors and caps (anything I can get in that size). They are fairly small but can still be hand soldered if needed.
  Bean.
  
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• SN96 Posts: 318

  2005-09-13 20:36 edited 2005-09-13 20:36

  I agree, 0805's if you can get them in that package size or 1206's are·even better in my opinion if you have room and the part is available in that package size.
  
  I work at a company that hand solders smt components that are not machine able and I have hand soldered literally·thousands of 0603's, 0805's & 1206 components using SN96, SN63, and even some HMP solder alloys.
  
  I can even hand solder fine pitch leads found on QFP components. Solder is very easy to work with if you have the right tip.
  
  Mike
• Guenther Daubach Posts: 1,321

  2005-09-13 20:53 edited 2005-09-13 20:53

  ... and a calm hand
  
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  Greetings from Germany,
  
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• nick bernard Posts: 329

  2005-09-14 13:19 edited 2005-09-14 13:19

  can you reflow 0603-1206 w/ hot air?
  
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• Paul Baker Posts: 6,351

  2005-09-14 14:59 edited 2005-09-14 14:59

  Ive hand done 0603 and 0402, though I dont think Ill get 0402s again. Personally I really like 0603, with a nice pair of tweezers (fine tip, not too stiff) they are pretty simple and quick to solder with a fine tip iron.
  
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• Electronegativity Posts: 311

  2005-09-23 05:28 edited 2005-09-23 05:28

  www.mouser.com
  
  Has a great selection of the 1206 packaged components, which seem to be the biggest SMD devices available.
  
  I ordered a bunch of them on the "bigger is better (easier)" premise.
  
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  I wonder if this wire is hot...
• Paul Baker Posts: 6,351

  2005-09-23 11:52 edited 2005-09-23 11:52

  I used 0 Ω 1206 resistors as ground bridges of the backside floodplane, they were 10x more difficult to solder than 0603, though I suspect that the large surface area each terminal was attached to had a significant effect on the difficulty.
  
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  ·1+1=10
• Electronegativity Posts: 311

  2005-09-23 14:04 edited 2005-09-23 14:04

  That's a good trick to make bridges, I have been pondering a circuit layout and might incorporate your technique.
  
  I have no experience with these components so I figured that the bigger ones would be better to start with.
  
  What was it that made them harder to solder?
  
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  I wonder if this wire is hot...
• Paul Baker Posts: 6,351

  2005-09-23 15:32 edited 2005-09-23 15:32

  The fact that the resistors were quite large and each terminal was connected to large copper areas, the resultant heat capacity was very large. As a result it was difficult to make the joint hot enough for the solder to flow because as much as I would heat it, that heat would be wicked away. And I was using low tempurature solder, it would have been more difficult with regular solder. Turning up the iron helped somewhat, but I was afaid to turn it up too much because I could feel the floodplane copper eminating a fair amount of heat from underneath the solder mask.
  
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  ·1+1=10
• Dave Paton Posts: 285

  2005-09-23 18:02 edited 2005-09-23 18:02

  Like Paul, I've done a lot of time hand soldering SMT resistors, and if you think 0603s are bad, try 0402s or the impossibly small 0201s (!). My hands aren't all that steady either, so I've rigged up some additional supports around my Panavise and my work area to give me a place to rest my forearm while I twiddle the tweezers with my fingers (which are thankfully still tremor free). Avter a morning filled with 100+ lead QFNs, let me drop a little SMT tip style knowledge upon the group, also known as dave's $0.02:
  
  *Get the finest tips you can.
  *Tiny diameter wire solder works, but with things smaller than 0603s it becomes very difficult to control the fillets on the components.
  *Solderpaste is better, especially if you have a hot air gun to work with. It's the only way to do large micropitch ICs like DRAMs and FPGAs, not that most folks here will be hand-building boards containing things like that, but even an SX52 is tough on old eyes, which can benefit from a modified reflow technique.
  *Use a fume extractor. Those little parts and their little balls of solder still fry flux, and the more of that stuff you get in your face, the harder it is to see, especially if you're squinting.
  *Plan on making mistakes. Practice is the only way to get good.
  *Use a magnifier. I'm 26, I'm corrected to 30/20 at less than 10', and I go blind after a few hours of rework without magnification. Yes, my prescription is for close work, and yes, I can still read the labels on 0603s without squinting.
  *Practice. Start big and work down. 1206s should be easy for anyone with tweezers that can hand-solder DIPs. 0805s fall into that category for most folks.0603s require some practice and a deft touch. Keep away from snaything smaller (0402s, SC70-5s, etc) unless you absolutely need to use it. It's not worth the hassle.
  
  Hmm..that sounded more like a rant, but it's based on close to a decade of SMT rework time. As always, it's only worth what you paid for it
  
  -dave
  
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