PRINTED  BOARD  HANDLING  AND  STORAGE  GUIDELINES  

An  introduction  by  IPC  D-­‐35  subcommittee  member,  Bob  Lazzara  

To  preserve  the  quality  and  reliability  of  PCBs  during  shipment  and  storage,  military  specifications  and  guidelines  defined  packaging  methods  

Prior to the IPC-1601

Many  documents  were    •  obsolete  •  incomplete  •  did  not  address  lead-­‐free  assembly  processes  

•  did  not  cover  newer  laminates  or  final  surface  finishes  

Prior to the IPC-1601

Alternative  surface  finishes  added  concerns/requirements  for  PCB  packaging  &  handling  to  preserve  surface  finish  and  assure  solderability.  

Prior to the IPC-1601

The  IPC-­‐1601  provides  suggestions  for  proper:  •  handling  •  packaging  materials  and  methods  

•  environmental  conditions  

•  storage  for  PCBs  

Scope and Intent

The  1601  intends  to  protect  PCBs  from:  •  contamination  •  physical  damage  •  solderability  degradation  

•  electrostatic  discharge  (ESD)  

•  moisture  uptake  

Scope and Intent

Moisture  absorbed  by  PCBs  will  expand  at  soldering  temperatures.      The  resulting  vapor  pressure  can  lead  to:  •  internal  delamination  •  excessive  strain  on  plated-­‐hole  walls  (e.g.,  post  separation)  

Scope and Intent

The  1601  covers:  •  Fabrication  of  the  PCB  •  Delivery  to  Assembler  

•  Receiving  the  PCB  •  Stocking  the  PCB  •  Assembly  &  soldering  

Scope and Intent

Targets  these  functions  involving  PCB…  

•  DESIGNERS  •  MANUFACTURING  •  ASSEMBLY  •  SHIPPING  •  STORAGE  •  WARRANTY  

Information  was  supplied  by  individual  serving  all  of  these  functions,  as  well  as  material  and  equipment  suppliers.  

Scope and Collaboration

PCB  Raw  Material  Handling  &  Storage  guidelines  include:  •  Laminates  •  Handling  and  Foreign  Object  Concerns  

•  Environmental  Concerns  

•  Inner  Layer  Production  right:  foreign  object  between  inner  layers,  Drilling  operation.  

Guidelines for Fabricators: Raw Materials

Core  Materials,  Prepreg  and  Resin  Coated  Foils  are  sensitive  to  damage.  Guidelines  for  handling  &  storage  of  prepregs  and  resin  coated  foils  include:    •  Handle  prepreg  by  the  edges  

using  clean  latex  or  nitrile  gloves.  

Guidelines for Fabricators: Raw Material Examples

•  Store  prepreg  flat  in  a  cool,  dry  environment  (<  23  °C  [73  °F],  <50%  RH).  

•  Reseal  opened  bags  of  unused  prepreg.  

•  In  cases  where  storage  temperature  is  significantly  below  room  temperature,  allow  prepreg  to  acclimate  to  ambient  conditions  prior  to  layup.  Keep  prepreg  in  a  sealed  package  during  the  stabilization  period  to  prevent  moisture  condensation.  

•  Do  not  fold  prepreg.  

Because  moisture  control  is  critical  prior  to  inner  layer  lamination,  key  recommendations  are  made  for  the  following:  •  Storage  Conditions  •  Pre-­‐lamination  •  Subcomposite  Cores  

(Sequential  Lamination)  right:  edge-­‐view  of  PCB,  pre-­‐press,  

depicting  two  “cores”  (green)  

 

Guidelines for Fabricators: Etched Cores & Subcomposites

After  the  layers  are  pressed  together,  the  1601  continues  with  guidelines  for  the  following  areas  and  processes:  •  Processing  Validation  &  

Control  •  Handling  &  Transport  of  

Product  •  Environment  •  Test  •  Inspection  •  Recommended  Moisture  

Levels  Prior  to  Packaging  

Guidelines for Fabricators: Post Lamination

Non-­‐PCB  Issues:  •  Phototooling  •  Temperature  and  Humidity  

•  Handling  and  Storage  •  Process  Equipment  •  Capability  

right:  automatic  solder  mask  coating  system  

Guidelines for Fabricators: Non-Product Issues

Temperature  and  humidity  levels  where  photo  tools  are  used  &  stored  should  be  the  same  as  where  the  photo  tools  were  manufactured.  Variation  between  areas  can  cause  growth  (moisture  gain)  or  shrinkage  (moisture  loss).  

right:  light  passes  through  photo-­‐tool  (black)  casting  the  circuit  image  onto  photo-­‐polymer  (blue)  

Guidelines for Fabricators: Non-Product Example

PCB  moisture  sensitivity  will  depend  on…  •  the  resin  system  •  details  of  design  and  construction  

•  assembly  processes  •  soldering  temperatures    

…that  the  PCB  will  be  exposed  to  by  the  Assembler.  

Moisture  Levels  Prior  to  Packaging  

Because  verification  may  affect  cost  and  schedule,  limitations  on  moisture  content  prior  to  packaging  should  be  as  agreed  between  user  and  supplier  (i.e.,  Assembler  and  Board  House).  

Moisture Content: Verification Agreement

Baking  may  be  necessary  to  remove  residual  moisture  absorbed  into  the  PCB  during  the  time  between  completion  of  the  fabrication  process  and  exposure  to  the  assembly  soldering  .  

Guidelines  for  Assemblers:  Baking  for  Moisture  Removal  

If  process  controls  are  in-­‐effective,  the  most  practical  remedy  is  baking.  However,  baking:  •  increases  cost  &  cycle  time  •  can  degrade  solderability  •  increase  the  likelihood  of  

handling  damage  or  contamination  

Problems  Caused  By  Baking  

Recommendations  for  PCB  Baking  Profiles

Packaging  should  include  moisture  barrier  bags,  desiccant  to  absorb  any  moisture  that  enters  the  bag,  Humidity  Indicator  Cards  to  provide  a  visual  indication  of  moisture  level,  and  heat-­‐sealing  of  the  bag.  

Recommendations  for  PCB  Packaging

WVTR  is  the  rate  that  water  vapor  passes  through  a  specific  area  of  barrier  material.  The  WVTR  for  dry  packaging  PCBs  should  meet  requirements  of  IPC-­‐J-­‐STD-­‐033  (a  WVTR  of  <  0.002  gm/100  in2/24  hrs.)  A  lower  WVTR  value  may  increase  shelf  life  of  the  PCB,  or  reduce  the  amount  of  desiccant  required.  

Water  Vapor  Transmission  Rate  (WVTR)  

The  quantity  and  quality  of  the  desiccant  material  selected  should  be  in  accordance  with  IPC-­‐J-­‐STD-­‐033  and  should  be  sulfur  free.    

About  Desiccant  

After  going  through  the  effort  to  prevent,  mitigate  and  eliminate  moisture,  don’t  keep  moisture  sensitivity  a  secret.    Before  you  let  it  go,  let  the  next  person  know.  

Moisture-­‐Sensitive  Marking

Thank  you  for  watching  Introduction  to  the  IPC-­‐1601:  Printed  Board  Handling  and  Storage  Guidelines.    Bob Lazzara VP,  Technology  BobL@Circuit-­‐Connect.com  (800)  560-­‐9457,  ext.  1  Circuit  Connect,  Inc.  

Thank  You.