PRINTED BOARD HANDLING AND STORAGE GUIDELINES An introduction by IPC D-­‐35 subcommittee member, Bob Lazzara Prior to the IPC-1601
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. Scope and Intent
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 Collaboration
Targets these functions involving PCB… •
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DESIGNERS MANUFACTURING ASSEMBLY SHIPPING STORAGE WARRANTY Information was supplied by individual serving all of these functions, as well as material and equipment suppliers. Guidelines for Fabricators:
Raw Materials
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 Material Examples
Core Materials, Prepreg and Resin Coated Foils are sensitive to damage. Guidelines for handling & storage of prepregs and resin coated foils include: •
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Handle prepreg by the edges using clean latex or nitrile gloves. •
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. Guidelines for Fabricators:
Etched Cores & Subcomposites
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:
Post Lamination
After the layers are pressed together, the 1601 continues with guidelines for the following areas and processes: •
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Processing Validation & Control Handling & Transport of Product Environment Test Inspection Recommended Moisture Levels Prior to Packaging Guidelines for Fabricators:
Non-Product Issues
Non-­‐PCB Issues: •  Phototooling •  Temperature and Humidity •  Handling and Storage •  Process Equipment •  Capability right: automatic solder mask coating system Guidelines for Fabricators:
Non-Product Example
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) Moisture Levels Prior to Packaging 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 Content:
Verification Agreement
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). Guidelines for Assemblers: Baking for Moisture Removal 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 . Problems Caused By Baking If process controls are in-­‐
effective, the most practical remedy is baking. However, baking: •
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increases cost & cycle time can degrade solderability increase the likelihood of handling damage or contamination Recommendations for PCB Baking Profiles
Recommendations for PCB Packaging
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. Water Vapor Transmission Rate (WVTR) 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. About Desiccant The quantity and quality of the desiccant material selected should be in accordance with IPC-­‐J-­‐
STD-­‐033 and should be sulfur free. Moisture-­‐Sensitive Marking
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. Thank You.
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.