Solder Levelling an SMT Pad
and
Soldering SMT Components



To overcome the problem described in the SMT Components Page, commercial PCB manufacturers use a process called HOT SOLDER LEVELLING which produces a flatter solder joint thus:

 



 
 
 

If this process is not available there is an ALTERNATIVE TECHNIQUE using SOLDER BRAID to achieve the same result.


  • Scrub the pads with a small brush while applying IPA SOLVENT
  • Apply the solder (MUST use the 2% SILVER Type) to the SMT pad

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  • Place the solder braid on the pad NEAR to the track connecting the pad

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  • Apply the soldering iron to the top of the braid resting on the pad
  • While the solder is molten, SLOWLY DRAG the braid away from the pad in the OPPOSITE direction to the track connecting it

 
TAKE CARE when DRAGGING the solder braid. As stated previously, the pad is FLOATING on molten glue which is holding the pad on the board.

This is the reason for dragging the braid AWAY from the track that connects to the pad. The track prevents the pad from moving out of position.

 
 

Soldering a 2 Padded SMT Component
  • Tin BOTH Pads

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  • Solder Level only ONE of the 2 pads as described previously, leaving the other pad just TINNED

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  • Hold the sides of the component with tweezers so its terminals aren't OBSTRUCTED

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  • Apply solder and heat the TINNED pad

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  • While the solder is molten, move the component to align on BOTH pads

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  • If alignment is proving to be DIFFICULT then remove the iron OFTEN to prevent the pads from being DAMAGED by the excessive heat

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  • When the component is correctly ALIGNED on the pads then solder the LEVELLED PAD properly

  • Finally RESOLDER the first pad AGAIN as almost certainly that joint will be DRY from all the extra heating during the alignment procedure

 

Soldering a Multi Padded SMT Component
  • Tin ALL the component's pads

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  • Solder Level all pads EXCEPT one CORNER pad

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  • Hold the component with tweezers so that its terminals aren't OBSTRUCTED

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  • Apply solder and heat to the UNLEVELLED corner pad

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  • While the solder is molten, move the component to align on ALL its pads

    •  
  • If alignment is proving to be DIFFICULT then remove the iron OFTEN to prevent the pads from being DAMAGED by the excessive heat

    •  
  • When the component is correctly ALIGNED on ALL the pads then solder the DIAGONALLY OPPOSITE corner pad and RE-CHECK alignment

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  • REPEAT the task of soldering the corner pads until alignment is correct

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  • Now solder all the OTHER pads

  • Finally RESOLDER the ORIGINAL 2 corner pads AGAIN as almost certainly those joints will be DRY from all the extra heating during the alignment process