ECE%20Projects%20Lab

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ECE Projects Lab

• Surface Mount Technology

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What is SMT?

• Surface Mount Technology
• Used primarily in industry
• Same circuitry with much smaller components
• Was not intended for individual soldering, but
  gaining popularity

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SMT Components
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Reflow

• a thermal process in which solder paste is used
  to electrically connect components to their
  attachment pads. It is the most common means to
  attach a surface mounted component to a circuit
  board
• Reflow temperature is the temperature at which
  the solder paste changes state from solid to
  liquid

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SMT Board
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Why SMT (advantages)?

• Much smaller size
• Components on both sides of board
• Leads can be much shorter reducing inductance and
  resistance thereby increasing performance
• Prototyping is more indicative of the final
  product

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How to SMT solder (techniques)

• Fine tip soldering
• Uses conventional soldering techniques on a much
  smaller scale
• Hot plate reflow
• Useful for single ICs with limited footprint
• Oven reflow
• Uses soldering paste and reflows entire board

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How to SMT rework

• Solder wick
• Uses fine mesh conductive Copper braid. Heat and
  capillary action pulls excess solder away
• Hot air reflow
• Uses hot air to reflow the solder with components
  present
• De-Solder vacuum plunger/sucker
• Uses small negative pressure to suck up excess
  solder

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Fine Tip SolderingConventional Equipment

• Useful for Larger components
• Causes eye strain
• Requires a steady hand

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Fine Tip SolderingSpecialized Fine-tip tools

• Hot-Air Rework Station AM6500 by JBC
• Fine tip solder tools
• Desoldering tools
• Hot tweezers
• Hot air gun

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Hot plate reflow

• useful for smaller boards as heat distribution on
  a hotplate is far less uniform than a convection
  oven
• end point is monitored visually

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Oven reflow

• Typical Reflow oven
• Large and bulky
• Expensive ?
• Cuisinart TOB 165
• Just as good
• A small fraction of the cost

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Oven Reflow Overview

• After applying solder paste and setting
  components, the board is inserted to be cooked
• End result is a perfectly soldered board for a
  fraction of the cost (no eye strain either)

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Reflow Profile

• The temperature of the reflow process must
• be precise enough to not damage ICs through
  excess heat
• be sufficient for reflow of solder

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Oven Reflow Steps

• Set ICs and components

• Apply soldering paste

• Touch up (here using solder wick)

• Cook!

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Industrial SMT Movie

• Silicon Run II

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Copper Solder Wick (rework)

• useful for removing excess solder
• braided copper mesh is used to remove solder via
  capillary action
• Fine-tip or conventional soldering iron is used
  for heating braid and solder

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Hot air reflow (rework)

• Hot-Air Rework Station AM6500 by JBC
• Fine tip solder tools
• Desoldering tools
• Hot tweezers
• Hot air gun

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How hot air reflow works

• Hot air used to desolder IC
• Vacuum extractor pulls IC after solder flows

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De-Solder vacuum plunger/sucker(rework)

• Uses small vacuum to pull solder away from board
• Hand-held manual version
• Heated tip vacuum combined on SMT rework
  station

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Summary

• Fine tip soldering is hard, but essential
  sometimes
• Hotplate or Oven reflow are great for creating a
  whole board at once
• Rework techniques include Copper wick, Hot-air
  reflow, and de-solder vacuuming
• ECE Projects Lab can do it all

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Credits/Work cited

• http//en.wikipedia.org/wiki/Surface-mount_technol
  ogy
• General SMT info
• http//www.heinc.com/jbc/repair.html
• Hot air reflow station website
• http//www.bidservice.com/Browses/NF_Detailed_Item
  _View_new.asp?ProductID20069
• Place to purchase typical reflow oven
• http//www.seattlerobotics.org/encoder/200006/oven
  _art.htm
• Another group that has done a similar project
  with a toaster oven
• http//www.circuitcellar.com/library/print/0704/La
  coste_168/
• Thermal profile for a toaster oven

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Design Lab Website

• Presentations available
• Online Reflow Tutorial
• http//www.ee.duke.edu/DesignLab/

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Thanks!