Corporate Improvement

Wave  Solder  Defect  Reduc1on  Chris  Ballou  

January 24, 2013

Business  Case  •  Since  the  beginning  of  Q3  in  2011,  the  PCB  team  has  seen  an  increase  in  

assembly  solder  joint  defects  stemming  from  the  wave  soldering  process.    

Business  Case  

•  PCB  Team  uses  two  soldering  techniques  –  Wave  Soldering  –  Hand  Soldering    

 

Advantages Disadvantages Advantages DisadvantagesAllows  for  mass  soldering  of  assemblies  in  a  very  short  period  of  time.

Equipment  and  materials  are  expensive.

Better  control  of  soldering  process  at  specific  solder  joints.

Solder  joint  quality  can  be  inconsistent  due  to  human  factor.

Quality  of  a  joint  is  very  consistent  from  board  to  board.

Process  consumes  a  sizeable  footprint  within  production  space.

Can  consume  a  much  smaller  production  footprint.

Generally  requires  a  large  number  of  human  resources  and  is  very  inefficient  (labor  intensive).

Wave  Soldering Hand  Soldering

Business  Case  •  Based  on  the  complexity  of  our  board  designs,  the  wide  range  of  components  

used  in  each  design,  and  the  size  of  many  of  our  assemblies,  wave  soldering  is  a  highly  complex  process.  Due  to  the  complexity  of  this  process,  many  of  our  assemblies  require  addi1onal  hand  soldering  rework  to  correct  soldering  defects  caused  by  wave  soldering.  

 •  By  reducing  the  amount  of  defects  present  on  our  assemblies,  improvements  

will  be  made  in  the  following  areas:  –  Reduc1on  in  Opera1ng  Cost  

•  Less  rework  on  each  assembly  will  decrease  resource  requirements  and  cycle  1me.  

–  Reduc1on/Elimina1on  of  3  of  the  7  Wastes  •  Inventory  –  With  less  rework  being  required,  assemblies  will  travel  through  our  value  

stream  faster  thus  reducing  the  amount  of  WIP  on  the  floor.  •  Over  Processing  –  Addi1onal  rework  leads  to  over  processing  of  assemblies.  In  regards  to  

soldering,  over  processing  assemblies  will  decrease  the  overall  quality  and  integrity  of  our  product.  

•  Defects  –  Reducing  the  amount  of  rework  required  on  our  assemblies  is  directly  related  to  a  reduc1on  of  the  number  of  defects  present  on  each  assembly.  This  reduc1on  will  improve  the  overall  efficiency  of  our  process.  

 

A good Problem Statement contains:

q  What? q  Where? q  When? q  To What Extent? q  How Do I Know?

Problem Statement (remove/hide for presentation)

Problem  Statement  

•  “In  April,  May,  and  June  of  2012,  an  analysis  of  Pareto  data  collected  at  Post  Wave  shows  excessive  soldering  defects  being  generated  at  the  Wave  Soldering  Machines.  An  average  of  nearly  385  recorded  defects  per  week  are  resul1ng  in  excessive  assembly  rework  and  an  average  weekly  DPMO  of  2471.”  

Business  Case  •  Nearly  385  defects  per  week  is  very  good  considering  our  average  

opportuni1es  for  defects  per  week  are  in  the  range  of  163,000!  Despite  this,  the  PCB  team  strives  to  minimize  non-­‐value  added  ac1vity.    

•  Many  contract  manufacturers  (CMs)  accept  a  certain  amount  of  touch  up  and  rework  for  several  reasons:  –  CMs  produce  assemblies  for  mul1ple  customers,  not  just  one.      –  There  is  addi1onal  costs  to  dedica1ng  resources  to  op1mize  processes.    

Touch  Up  and  Rework  =  Non  Value  Added  

A good Project Objective is:

q  Specific q  Measurable q  Achievable q  Relevant q  Time Bound

Project Objectives (remove/hide for presentation)

Project  Objec;ve  

•  “Reduce  the  weekly  DPMO  of  2471  by  50%  at  Wave  Soldering  on  the  assemblies  that  make  up  “the  top  90%”  by  October  2012.”  

Value  Stream  Map  

Wave  Soldering  Process  

Assembly Travels into the Wave Machine

Flux the Assembly

Preheat the Assembly

Wave Solder the Assembly

Assembly Travels out of the

Wave Machine

Wave  Solder  Fishbone  Diagram  

•  Used  to  iden1fy  where  process  gaps  may  be  present  within  the  Wave  Soldering  Process.  

 

Wave  Recipe  Op;miza;on  

•  Op1mizing  tools  used  to  refine  wave  recipes.    

•  Assemblies  that  had  low  or  no  DPMO  average  during  the  data  collec1on  phase  were  not  op1mized.  

 •  Eliminates  the  gap  of  incorrectly  wrijen  wave  recipes.    

Wave  Recipe  Op;miza;on  Observa;ons  

•  Many  recipes  had  conveyor  speeds  that  were  far  too  slow.    

•  Wave  height  levels  were  not  within  specifica1ons.    

•  Several  recipes  had  preheat  temperatures  that  were  too  warm.  

 

Wave  Recipe  Op;miza;on  Results  

•  10  of  15  wave  solder  recipes  were  op1mized.    •  Many  of  the  new  recipe  parameters  are  iden1cal  or  very  

close  to  one  another.  

Transfer  of  Automa;c  Solder  Feeder  

•  Automa1c  Solder  Feeder  is  used  to  fill  the  solder  pot.    

•  Eliminates  two  separate  gaps  iden1fied  in  the  Fishbone:  –   Solder  pot  not  filled  to  required  level.  –  Not  filling  the  solder  pot  when  required.    

Transfer  of  Automa;c  Solder  Feeder  Observa;ons  

•  ECO  was  required  to  convert  all  material  to  required  bar  stock  sizes.    

•  Aler  the  transfer,  it  was  observed  that  the  Automa1c  Solder  Feeder  was  not  being  lel  on  during  opera1on.  

Transfer  of  Automa;c  Solder  Feeder  Results  

•  The  Lead-­‐Free  solder  pot  now  stays  at  the  op1mal  level  whenever  the  wave  soldering  machine  is  in  use.  

 •  The  Automa1c  Solder  Feeder  has  been  password  

protected  in  the  “ON”  state.    

Defect  Iden;fica;on  Training  

•  Eliminate  the  gap  of  improper  training.    •  Can  reduce  the  amount  of  over  processing  that  is  

occurring.    •  Can  reduce  the  number  of  falsely  iden1fied  defects  at  

inspec1on.    •  Increases  the  quality  of  our  assemblies  by  minimizing  the  

effects  of  thermal  cycling  on  solder  joints  which  occurs  during  rework.  

Defect  Iden;fica;on  Training  Observa;ons  

•  Many  assemblers  were  not  following  the  IPC  guidelines  for  iden1fying  defects  in  regards  to  solder  joint  forma1on.  

•  Most  assemblies  require  only  class  2  requirements  be  met.  

 

 •  Many  assemblers  were  building  to  class  3  requirements.  

 

Defect  Iden;fica;on  Training  Results  

•  Assemblers  are  now  aware  of  the  appropriate  IPC  requirements.  

•  Assemblers  know  where  to  find  any  informa1on  if  they  have  ques1ons.  

•  Assemblers  have  shown  they  can  correctly  describe  IPC  requirements  for  par1cular  classes  during  random  audi1ng.  

 

ECO  Work  

•  Revisions  to  bare  boards  helped  reduce  defects  –  Increased  lead  pitch  to  minimize/eliminate  shorts  –  More  components  now  machine  placed.  This  minimizes  component  movement  which  will  affect  soldering.  

Results  

•  Aler  op1mizing  wave  solder  recipes,  transferring  the  automa1c  solder  feeder,  providing  addi1onal  training  to  our  assemblers,  and  ECO  work,  our  DPMO  has  improved  from  the  baseline  by  75.93%!  

1st Eight Week Period 2nd Eight Week Period

Results  

•  The  improvement  in  DPMO  translate  directly  to  a  reduc1on  in  rework  1me.  This  reduc1on  also  translates  to  an  average  annual  cost  savings.    

Nearly Two (2) full weeks of continuous rework eliminated!