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Quote: Email your PCB files to Sales@pcbsync.com (Preferred for large files) or submit online. We will contact you promptly. Please ensure your email is correct.
Notes: For PCB fabrication, we require PCB design file in Gerber RS-274X format (most preferred), *.PCB/DDB (Protel, inform your program version) format or *.BRD (Eagle) format. For PCB assembly, we require PCB design file in above mentioned format, drilling file and BOM. Click to download BOM template To avoid file missing, please include all files into one folder and compress it into .zip or .rar format.
Nothing ruins a production run faster than pulling boards out of stock only to watch them delaminate during reflow. The white spots, blistering, and blown barrels that result from moisture-damaged PCBs cost the electronics industry millions annually—yet these failures are entirely preventable with proper storage and handling practices.
That’s exactly whatIPC-1601 addresses. As the industry’s sole guideline for printed board handling and storage, this standard provides the practical procedures needed to protect PCBs from moisture absorption, contamination, and physical damage throughout their lifecycle. After dealing with countless moisture-related assembly failures, I’ve learned that following IPC-1601 isn’t optional—it’s essential for reliable electronics manufacturing.
IPC-1601, officially titled “Printed Board Handling and Storage Guidelines,” establishes requirements for protecting bare printed circuit boards from contamination, physical damage, solderability degradation, electrostatic discharge (ESD), and moisture uptake. Originally released in August 2010, the current revision is IPC-1601A (June 2016), consisting of 36 pages of practical guidance.
The standard covers all phases from bare board manufacture through delivery, receiving, stocking, assembly, and soldering. It provides specific guidance on packaging materials, environmental conditions, baking procedures, and handling practices that preserve PCB quality and reliability.
IPC-1601 Revision History
Revision
Release Date
Key Content
IPC-1601
August 2010
Original release, basic handling and storage guidelines
Note: While IPC-1602 has officially superseded IPC-1601A, many organizations continue referencing IPC-1601 in their quality systems and procurement documents. The core principles remain consistent between versions.
Why Moisture Protection Matters for PCBs
Printed circuit boards are hygroscopic—they absorb moisture from the environment. The epoxy resin in FR-4 and other laminates readily takes up water vapor, which becomes trapped within the material structure. This absorbed moisture creates serious problems during high-temperature assembly processes.
What Happens During Reflow
Temperature
Moisture Behavior
Potential Damage
Room temperature
Moisture stable within laminate
No immediate effect
100°C (212°F)
Moisture begins mobilizing
Stress buildup begins
150°C (302°F)
Water vaporization accelerates
Internal pressure increases
200°C+ (392°F+)
Rapid steam expansion
Delamination, barrel cracking
260°C (500°F)
Maximum lead-free reflow
Catastrophic failure if wet
When moisture-laden boards hit lead-free reflow temperatures (typically 245-260°C peak), the trapped water instantly vaporizes. The resulting steam pressure can exceed the bond strength between laminate layers, causing delamination, measling, and blown plated-through holes—defects commonly called “popcorning.”
The Lead-Free Challenge
Lead-free assembly has dramatically increased moisture sensitivity concerns. The higher reflow temperatures required for SAC alloys (30-40°C higher than tin-lead) generate significantly more steam pressure from absorbed moisture.
Solder Type
Peak Reflow Temperature
Moisture Sensitivity
Sn-Pb (eutectic)
215-225°C
Moderate
SAC305
245-255°C
High
SAC387
250-260°C
Very High
IPC-1601 specifically addresses lead-free assembly requirements, recognizing that moisture control practices adequate for tin-lead processes may be insufficient for lead-free manufacturing.
IPC-1601 Storage Environment Requirements
IPC-1601 establishes environmental parameters for PCB storage areas to minimize moisture absorption during warehousing.
Recommended Storage Conditions
Parameter
Requirement
Notes
Temperature
15°C to 30°C (59°F to 86°F)
Stable, avoid fluctuations
Relative Humidity
40% to 65% RH
Lower is better for long-term storage
Maximum RH
≤85% RH
Never exceed
Light exposure
Minimize direct sunlight
UV degrades some finishes
Cleanliness
Dust-free environment
Contamination affects solderability
Shelf Life Guidelines by Surface Finish
Different surface finishes have varying susceptibilities to degradation during storage. IPC-1601 provides guidance aligned with the IPC-4550 series specifications for final finishes.
Boards stored beyond these periods may require solderability testing before use or baking to remove absorbed moisture.
Moisture Barrier Bags (MBB) Requirements
Moisture barrier bags are the primary defense against moisture absorption during storage and shipment. IPC-1601 provides detailed guidance on MBB selection and use.
MBB Performance Specifications
Parameter
Requirement
Test Method
Water Vapor Transmission Rate (WVTR)
≤0.02 g/100 in²/24 hrs
ASTM F1249
Seal strength
Adequate for shipping
Visual inspection
ESD protection
Per ANSI/ESD S541
Surface resistivity test
Puncture resistance
No holes or tears
Visual inspection
Higher-performance bags with WVTR ≤0.002 g/100 in²/24 hrs provide superior protection for extended storage or humid shipping conditions.
Proper MBB Sealing Procedures
Step
Procedure
Purpose
1
Verify boards are dry (bake if necessary)
Don’t seal in moisture
2
Include appropriate desiccant quantity
Absorb residual moisture
3
Include humidity indicator card (HIC)
Monitor internal humidity
4
Remove excess air
Reduce moisture volume
5
Heat seal with minimum 6mm seal width
Ensure barrier integrity
6
Label with seal date and shelf life
Enable FIFO management
What to Do When Opening an MBB
IPC-1601 provides specific guidance for handling boards after opening moisture barrier bags:
HIC Reading
Condition
Required Action
≤10% RH
Acceptable
Use within floor life or reseal
10-20% RH
Caution
Evaluate moisture content, consider baking
>20% RH
Excessive moisture
Baking required before use
30%+ RH or pink color
Severely compromised
Extended baking, solderability test
Once opened, boards should be assembled within their floor life or resealed in a fresh MBB with new desiccant.
Desiccant and Humidity Indicator Card Requirements
Desiccants absorb moisture inside the MBB, while humidity indicator cards (HICs) provide visual confirmation of the internal environment.
Desiccant Quantity Guidelines
IPC-1601 provides formulas for calculating desiccant requirements based on bag size and storage duration.
MBB Size (inches)
Bag Area (sq in)
Desiccant Units (12-month storage)
6 x 8
96
1 unit
8 x 10
160
1-2 units
12 x 16
384
2-3 units
18 x 24
864
4-5 units
24 x 36
1,728
8-10 units
Note: One “unit” of desiccant absorbs approximately 6 grams of water vapor. Larger bags or longer storage periods require proportionally more desiccant.
Humidity Indicator Card Interpretation
HIC Spot Color
Relative Humidity
Meaning
Blue
Below indicated %
Dry condition, acceptable
Lavender/Pink
At or above indicated %
Humidity threshold exceeded
Pink (all spots)
>50% RH
Severely compromised, baking required
Standard HICs show spots for 5%, 10%, 20%, 30%, 40%, and 50% RH. For PCB storage, the 10% and 20% spots are most critical for decision-making.
When boards have absorbed excessive moisture, baking is the most practical remedy. However, IPC-1601 emphasizes that PCB baking increases cost, extends cycle time, and can degrade solderability—prevention through proper storage is always preferable.
Recommended Baking Profiles
Board Thickness
Bake Temperature
Minimum Duration
Maximum Duration
≤1.6 mm
105-125°C
2 hours
8 hours
1.6-2.4 mm
105-125°C
4 hours
12 hours
2.4-3.2 mm
105-125°C
6 hours
24 hours
>3.2 mm
105-125°C
8-12 hours
48 hours
Baking Considerations by Surface Finish
Surface Finish
Baking Recommendation
Cautions
HASL
Standard profile
Minimal concerns
ENIG
Standard profile
Extended baking may affect gold
Immersion Silver
Reduced time preferred
Oxidation risk at temperature
Immersion Tin
Standard profile
Monitor for whisker growth
OSP
NOT RECOMMENDED
Degrades OSP coating; if required, use minimum temperature/time
Critical Warning: IPC-1601 explicitly states that baking is NOT recommended for OSP-coated boards. The organic coating deteriorates at baking temperatures, compromising solderability. If baking OSP boards is absolutely necessary, use the lowest possible temperature (≤100°C) and shortest duration.
Baking Best Practices
Practice
Rationale
Preheat oven before loading
Ensures consistent temperature
Don’t stack boards tightly
Allows air circulation
Maximum stack height 25mm
Ensures center boards reach temperature
Use calibrated oven
Verify actual vs. set temperature
Cool in desiccated environment
Prevent re-absorption during cooling
Package immediately after cooling
Minimize ambient exposure
Handling and Transport Guidelines
Physical handling affects both moisture absorption and mechanical integrity. IPC-1601 provides guidance for proper handling throughout the PCB lifecycle.
General Handling Requirements
Requirement
Purpose
Wear clean, lint-free gloves
Prevent fingerprint contamination
Handle by edges only
Avoid touching solderable surfaces
Use ESD-safe practices
Protect sensitive finishes
Avoid hand lotions/creams
Oils affect solderability
Keep away from food/beverages
Prevent contamination
Store flat, not on edge
Prevent warping
ESD Protection Requirements
Item
Requirement
Standard
Work surfaces
Static dissipative
ANSI/ESD S4.1
Packaging materials
ESD protective
ANSI/ESD S541
Personnel grounding
Wrist straps, heel grounders
ANSI/ESD S20.20
Humidity
>30% RH preferred
Reduces static buildup
Transport Considerations
Factor
Recommendation
Vibration
Use cushioning materials
Temperature extremes
Avoid cargo holds with extreme temperatures
Humidity exposure
Use MBB for all shipments
Stacking
Limit weight on bottom boards
Orientation
Keep panels flat
Impact on Surface Finish Solderability
Improper storage directly affects the solderability of different surface finishes. IPC-1601 addresses finish-specific concerns in conjunction with the IPC-4550 series specifications.
Finish Degradation Mechanisms
Surface Finish
Primary Degradation Mechanism
Storage Sensitivity
HASL
Intermetallic growth (slow)
Low
ENIG
Black pad (manufacturing), handling damage
Moderate
Immersion Silver
Tarnish, sulfur exposure
High
Immersion Tin
Oxide formation, whisker growth
Moderate-High
OSP
Thermal degradation, moisture absorption
Very High
Packaging Material Compatibility
Surface Finish
Packaging Requirements
Immersion Silver
Sulfur-free, pH-neutral materials only
All finishes
Non-corrosive desiccants
OSP
Moisture barrier critical
ENIG
Standard MBB acceptable
IPC-1601 vs IPC-1602: Understanding the Transition
IPC-1602 was released in 2021 and officially supersedes IPC-1601A. However, many organizations continue to reference IPC-1601.
Key Differences
Aspect
IPC-1601A
IPC-1602
Status
Superseded
Current
Release
June 2016
2021
Document type
Guideline
Standard (stronger language)
Content scope
Similar
Updated, expanded
Industry adoption
Still widely referenced
Growing adoption
Organizations should consider transitioning to IPC-1602 for new quality system implementations while recognizing that IPC-1601A remains valid for existing references.
Implementing IPC-1601 in Your Facility
Successful implementation requires coordination across multiple functions.
Implementation Checklist
Area
Action Items
Receiving
Inspect MBB integrity, check HIC, record receipt date
Stockroom
Control temperature/humidity, implement FIFO, track shelf life
Production
Monitor floor life, reseal unused boards, document exposure time
Quality
Audit storage conditions, verify baking procedures, test solderability
Purchasing
Specify packaging requirements, communicate shelf life needs
Common Implementation Mistakes
Mistake
Consequence
Prevention
Ignoring HIC readings
Using moisture-damaged boards
Train personnel on HIC interpretation
Baking OSP boards
Solderability failure
Establish finish-specific procedures
Inadequate desiccant
Moisture accumulation in MBB
Calculate requirements per IPC-1601
Poor seal integrity
MBB protection compromised
Train on proper sealing techniques
Exceeding shelf life
Solderability degradation
Implement inventory management system
Frequently Asked Questions About IPC-1601
How long can PCBs be stored before they need baking?
Storage duration depends on packaging and environmental conditions. Boards in properly sealed moisture barrier bags with desiccant can typically be stored 6-12 months depending on surface finish. Boards stored in ambient conditions (40-65% RH) have much shorter shelf lives—often 3-6 months. When in doubt, check the humidity indicator card; if it shows elevated humidity, baking may be required regardless of storage duration. OSP-coated boards are most sensitive and should be used within 3 months of manufacture when possible.
What temperature and duration should I use for PCB baking?
IPC-1601 recommends 105-125°C for most boards, with duration based on thickness: 2-4 hours for thin boards (≤1.6mm), 4-8 hours for standard thickness (1.6-2.4mm), and 8-24 hours for thick boards (>2.4mm). Never exceed the glass transition temperature (Tg) of the laminate material. Critical exception: OSP-coated boards should not be baked if avoidable, and if baking is necessary, use minimum temperature (≤100°C) and shortest possible duration to minimize coating degradation.
Can I reuse desiccant packets from opened moisture barrier bags?
No, desiccant that has been exposed to ambient air is likely saturated and ineffective. Always use fresh desiccant when resealing boards in moisture barrier bags. Some facilities regenerate desiccant by baking at 120°C for several hours, but this requires verification of moisture absorption capacity before reuse. For critical applications, fresh desiccant is strongly recommended. The cost of desiccant is negligible compared to the cost of moisture-damaged assemblies.
What does it mean when the humidity indicator card shows pink spots?
Pink coloration on HIC spots indicates the relative humidity inside the bag has exceeded the threshold printed on that spot. If the 10% spot is pink, humidity is above 10% RH—boards should be evaluated for baking. If the 20% or 30% spots are pink, baking is definitely required before assembly. If all spots are pink (50%+ RH), the moisture barrier has been severely compromised, and extended baking plus solderability testing is recommended. Note that HIC accuracy depends on temperature; readings should be taken at room temperature.
Does IPC-1601 apply to assembled boards (PCBAs) or only bare boards?
IPC-1601 primarily addresses bare printed boards before component assembly. However, the principles of moisture protection apply throughout the manufacturing process. For assembled boards with moisture-sensitive components, IPC/JEDEC J-STD-033 provides specific handling requirements. Many of the packaging and storage concepts in IPC-1601 (MBB, desiccant, HIC) apply equally to protecting assembled boards during storage and shipment, though component-level moisture sensitivity adds complexity.
Conclusion: Making IPC-1601 Work for Your Operation
Moisture-related assembly defects are entirely preventable with proper implementation of IPC-1601 guidelines. The standard provides practical, proven procedures for protecting PCBs from the contamination, physical damage, and moisture absorption that cause soldering failures and reliability problems.
Key takeaways for successful implementation:
Control your storage environment—temperature 15-30°C, humidity 40-65% RH maximum
Use proper packaging—moisture barrier bags with adequate desiccant and humidity indicator cards
Respect shelf life limits—different surface finishes have different storage tolerances
Bake when necessary, but avoid it when possible—especially for OSP finishes
Train your personnel—everyone handling boards should understand the requirements
Implement FIFO inventory management—use oldest stock first
The cost of implementing IPC-1601 properly is trivial compared to the cost of moisture-related defects discovered during assembly or, worse, in the field. Investing in proper storage and handling practices protects your boards, your production yields, and ultimately your customers.
Inquire: Call 0086-755-23203480, or reach out via the form below/your sales contact to discuss our design, manufacturing, and assembly capabilities.
Quote: Email your PCB files to Sales@pcbsync.com (Preferred for large files) or submit online. We will contact you promptly. Please ensure your email is correct.
Notes: For PCB fabrication, we require PCB design file in Gerber RS-274X format (most preferred), *.PCB/DDB (Protel, inform your program version) format or *.BRD (Eagle) format. For PCB assembly, we require PCB design file in above mentioned format, drilling file and BOM. Click to download BOM template To avoid file missing, please include all files into one folder and compress it into .zip or .rar format.
