Lead Free Assembly

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Lead Free Assembly
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• The biggest impact of the RoHS Directive for
  most companies will be the removal of lead from
  most electrical and electronic products

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Why are there Concerns?

• Lead is widely used in electronics assembly
• New alloys behave differently to conventional
  solders
• Materials and processes used will have to change
• Products will need to be retested and requalified
• Designs may need to change
• Older equipment may have to be upgraded or
  replaced
• Training
• Component availability and identification

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What are the Alternatives?

• Replace conventional solder with conductive
  adhesives only possible in limited applications
• Use alternative lead-free materials for
• PCB etch resists
• solderable finishes on circuit boards
• metallisation on components
• device assembly
• soldering

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Alternative Lead Free Solders

• Many alternative alloys have already been
  proposed and evaluated
• None offer all the processing benefits of
  tin-lead solder
• But viable alternatives are available
• Alloys proposed for widespread use have melting
  points above tin-lead e.g. SnAgCu and SnCu

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Alternatives to Tin Lead Solder
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Areas of Concern due to Higher Temperatures

• Substrate stability mechanical and thermal
• Component degradation/malfunctioning
• Fluxes and cleaning
• Effects on other organic materials
• Equipment capabilities - reflow profiles,
  inerting etc
• Inspection - different criteria
• Rework - which alloy to use
• Longer term reliability related issues
• Design implications

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PCB Laminates and Substrates

• A wide range of laminate types is used, from
  paper-filled phenolics to high Tg materials
• Laminates are organic materials and could be
  susceptible to
• warping
• degradation and thermolysis
• delamination
• failure of interconnects in multilayer plated
  through holes

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PCB Solderable Finishes

• Tin-lead HASL board finishes will not be possible
• Alternatives are well established and include
  tin, nickel-gold, silver, OSP etc
• Some issues e.g.lead-free solders do not wet OSP
  coated copper as well as tin-lead
• Possible to use lead-free HASL

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Lead Free Component Finishes

• Component leads need to be lead-free
• Recent shortage of such components but the
  situation is now improving
• There are several possible lead finishes
• Concerns over tin whiskering - suppliers working
  to develop whisker free matte tin processes

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Possible Problems with Lead Free
Tin Whiskering
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Possible Problems with Lead Free
Fillet lifting
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Possible Problems with Lead Free
Tombstoning
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Possible Problems with Lead Free
Solder balling
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Possible Problems with Lead Free
Other heat related issues
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Reflow Soldering

• Higher melting point solders require increased
  reflow temperatures
• Peak reflow temperatures for tin-lead solder
  exceed the melting point by 30 - 40C
• Typical peak reflow temperatures for alloys
  melting around 215C may be 230 - 240C
• Reflow temperatures may only exceed melting point
  by 10 - 25C

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Soldering Equipment

• Capability of existing equipment older reflow
  ovens may not have as good temperature control as
  modern ones
• Replacing equipment may be a significant cost to
  SMEs
• Safety issues running at higher reflow
  temperatures
• Higher temperatures mean higher energy costs

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Rework and Repair

• Concerns over component rework due to higher
  temperatures
• Important issue for complex components such as
  BGAs where a larger energy input is required
• How will the alloy used be identified by the
  repairer?
• There can be incompatibilities between alloys
  leading to reliability issues

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Lead Free is already Established

• Successful commercialisation of many products
• Lead-free telephones, televisions and keyboards
  are all now available in Europe
• Japanese committed to lead-free
• with or without legislation
• Matsushita made all electronic components
• completely lead-free by April 2003

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Possible Cost Implications
SourceFabfile Online Report 10th October 2004
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Summary

• Lead-free alloys require elevated soldering
  temperatures
• The influence of higher temperatures needs to be
  understood and allowances made
• Many of the identified issues are not as serious
  as initially anticipated
• It takes time and effort to develop new robust
  lead-free assembly processes!

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Questions?