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 FAQ's

  . COMPONENTS (8 questions)
  . HAND SOLDERING AND DE-SOLDERING (3 questions)
  . INSPECTION (3 questions)
  . PRINTED BOARD DESIGN (3 questions)
  . PRINTED CIRCUIT BOARDS (6 questions)
  . REFLOW SOLDERING (5 questions)
  . REWORK (1 questions)
  . SCREEN PRINTING (2 questions)
  . WAVE SOLDERING (4 questions)
  . X-RAY INSPECTION (1 questions)





WAVE SOLDERING

1 . After wave soldering with tin/silver/copper we have seen micro solder balls stuck to the surface of some SMT components, is this a problem?
2 . Our production department has problems wave soldering 0.050" connector pins in our lead-free process. The connector is positioned in the centre of the board.
3 . We currently suffer solder shorts on SOIC devices during wave soldering. Our pad width is 0.028" is this OK? If we reduce the pad width will the joint strength drop.
4 . What temperatures will be used for lead-free hand and wave soldering?

 

After wave soldering with tin/silver/copper we have seen micro solder balls stuck to the surface of some SMT components, is this a problem?
Well its not desirable but its probably not a problem if it is just the occasional ball. Its not just associated with any one alloy. Just like with solder resist surfaces solder can adhere to the surface of plastic and ceramic parts. Generally as you decrease the amount of flux applied during spray fluxing the balls can be seen. On components its normally random balls spitting back from the surface of the wave.

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Our production department has problems wave soldering 0.050" connector pins in our lead-free process. The connector is positioned in the centre of the board.
When changing from 0.1" pitch connectors to 0.050" and below there are often an increase in shorts. This is also the case when changing your design to lead-free. The use of this type of connector should be avoided unless absolutely necessary. Factors which effect yield are pin length, pad and resist aperture size.
A simple change in the pad shape on alternative pins can aid drainage when the connector is mounted across the board. Elongating alternative pads increases the separation points during wave soldering. In the other direction if shorts are present add solder thieves at the end of the connector.

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We currently suffer solder shorts on SOIC devices during wave soldering. Our pad width is 0.028" is this OK? If we reduce the pad width will the joint strength drop.
Reduce the pad width to 0.020" this will significantly reduce solder shorts. There will not be any significant drop in joint strength. If you do a pull test on these leads the pull strength will typically be 900-1200grams.

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What temperatures will be used for lead-free hand and wave soldering?
Really it’s impossible to answer the question as the solder alloy that is to be used is not provided. However let’s take as an example the use of tin/silver/copper SnAgCu for both hand and wave soldering.
In the case of wave soldering most applications should be possible with the temperature of the solder bath at 260degC. This is higher than the temperature of 245-250degC used currently for tin/lead.
In the case of hand soldering it will depend on the soldering iron, type and size of bit and the components and PCB to be soldered. In the case of a soldering iron which has a set-point 360-380degC should be suitable. When we have measured soldering and de-soldering operations being undertaken the actual temperature the joint sees is around 280-310degC.

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