IPC-1602 Standard for the Handling and Storage of Printed Boards

IPC-1602 provides requirements for the handling, packaging, transportation, and storage of printed circuit boards (PCBs). The standard evolved from IPC-1601, formerly titled Guidelines for Printed Board Handling and Storage. During revision, requirements for controlling printed boards throughout PCB and electronics manufacturing processes were added. The document was therefore changed from a guideline into a standard containing requirements and acceptance criteria, and it was assigned the new designation IPC-1602.

IPC-1602 covers protection and moisture-control requirements throughout PCB design, fabrication, assembly, transportation, and storage. Its requirements are intended to protect printed boards from contamination, physical damage, loss of solderability, and moisture absorption. The standard also considers packaging materials and methods, production environments, product handling and transfer, and the development of bake-out profiles for moisture removal.

1. Introduction

1.1 Background

Historically, the PCB industry relied on military specifications to guide packaging and storage. Many of those documents are now outdated or are not applicable to lead-free processes and newer materials. IPC-1602 updates these requirements and covers the complete process from PCB fabrication through assembly.

1.2 Scope

This standard defines requirements for PCB handling, packaging materials and methods, environmental conditions, and storage. The objective is to prevent contamination, mechanical damage, moisture absorption, electrostatic discharge (ESD) damage, and solderability degradation. Particular attention is given to delamination and hole-wall damage caused by moisture during the higher temperatures used in lead-free soldering.

1.3 Application

The standard applies to organizations and personnel involved in PCB design, fabrication, assembly, transportation, storage, and quality assurance.

1.4 Terms and Definitions

Relevant terminology includes assembler, dry packaging, humidity indicator card (HIC), moisture barrier bag (MBB), mandatory requirements expressed as "shall," recommendations expressed as "should," sulfur-free materials, and water vapor transmission rate (WVTR).

• Dry packaging: Packaging in which desiccant material and a humidity indicator card are placed together with the printed board inside a moisture barrier bag, which is then sealed.

• Humidity indicator card (HIC): A card printed or deposited with humidity-sensitive chemicals that indicate relative humidity. HICs commonly contain a sequence of circular indicator spots. Each color change corresponds to a higher relative humidity. When humidity exceeds the value printed beside an indicator spot, its color changes, such as from blue to pink or from brown to blue-green. When humidity decreases, the color returns to blue or brown.

• Moisture barrier bag (MBB): A package designed to inhibit water-vapor penetration. MBBs are made from materials with a low water vapor transmission rate and generally include a metallized aluminum layer, which gives the bag a reflective and opaque appearance.

• Sub-lamination: A printed-board subassembly formed by laminating two or more layers together during sequential lamination. The sub-lamination is subsequently laminated with other layers to form a complete printed board.

1.5 Superseded Document

IPC-1602 supersedes IPC-1601A and changes the document from a guideline into a standard. The latest version identified here is IPC-1602A.

1.6 Order of Precedence

If a conflict exists between this standard and the customer's procurement documentation, the customer's documentation takes precedence. If a conflict exists between this standard and a referenced document listed in Section 2, IPC-1602 takes precedence.

2. Applicable Documents

The standard references documents from IPC, JEDEC, ESD, ISO, ASTM, SAE, the European Union, and military standards. The listed documents include:

• IPC-HDBK-001, supplementary handbook and guidelines for J-STD-001

• IPC-T-50, terms and definitions for electronic circuit interconnections and packaging

• IPC-A-311, process control for phototool production and use

• IPC-TR-585, time, temperature, and humidity stresses affecting the solderability of finished boards

• IPC-TM-650, Test Methods Manual, Method 2

• IPC-2221, Generic Standard on Printed Board Design

• IPC-4552, performance specification for electroless nickel/immersion gold (ENIG) plating for printed circuit boards

• IPC-4553, specification for immersion silver on printed boards

• IPC-4554, specification for immersion tin on printed boards

• IPC-4556, specification for electroless nickel/electroless palladium/immersion gold (ENEPIG)

• IPC-6010-FAM, printed board performance specification family

• IPC-6017, qualification and performance specification for printed boards containing embedded passive devices

• IPC-7092, design and assembly process implementation for embedded components

• NCMS Solderability Component Long Term Storage Report — "Moisture Measurement in PCB's and Impact of Design on Desorption Behaviour"

• J-STD-001, Requirements for Soldered Electrical and Electronic Assemblies

• IPC/JEDEC J-STD-033, handling, packing, shipping, and use of moisture/reflow-sensitive surface-mount devices

• IPC/JEDEC J-STD-609, marking and labeling of components, printed boards, and printed board assemblies for lead, lead-free, and other attributes

• ANSI/ESD S541, Packaging Materials for the Protection of Electrostatic Discharge Sensitive Items

3. Printed Board Fabrication and Packaging

3.1 Printed Board Materials

All materials must be protected against damage caused by the environment, handling, and storage. Prepreg must be protected from moisture and ultraviolet radiation and stored in sealed bags. Operators should wear gloves when handling prepreg and avoid folding it.

The protection requirements for copper-clad laminate (CCL) during fabrication and handling focus on two areas. The first is handling and foreign-material control, which prevents material damage and contamination. The second is environmental control, particularly the moisture absorption behavior of cores before etching.

3.2 Inner-Layer Production

Phototool handling: Temperature and humidity must be controlled to prevent scaling and dimensional distortion.

Etched cores and sub-lamination: The boards must be protected against moisture absorption. When necessary, bake the material at 105–120 °C for 2 hours, with the stack height limited to 25.4 mm. After baking, the boards should be cooled promptly and laminated without delay. Some suppliers recommend 120 °C for 1 hour.

Moisture management is particularly important for sub-laminations used in sequential lamination. Excess moisture inside the board can migrate into the prepreg during the second lamination cycle. This may reduce the glass-transition temperature (Tg) and cause delamination or blow holes. Moisture content should be checked before lamination to determine whether baking is necessary.

After cooling, boards can rapidly absorb moisture again. If lamination will not take place within 24 hours, the boards must be moisture-barrier packaged or stored in a dry environment.

3.3 Processing of Laminated Boards

Processing equipment must be compatible with the board dimensions and material construction, and statistical process control (SPC) should be used to manage the process.

During handling, boards must be protected against ESD and fingerprint contamination. Environmental controls should minimize moisture absorption. Baking is recommended after drilling or routing when the process has introduced excessive moisture.

Before packaging, the moisture content of printed boards intended for lead-free soldering should be no higher than 0.1%. For boards intended for leaded soldering, the moisture content should be no higher than 0.2%. Moisture content can be evaluated using IPC-TM-650, Method 2.6.28.

3.4 Bake-Out for Moisture Removal

Baking increases cost and production time and can reduce solderability. It should therefore be used as a corrective measure when process control has failed and the printed board has absorbed excessive moisture. Bake-out conditions vary with the surface finish. Typical conditions are 105–125 °C for 4–6 hours, preferably in nitrogen or under vacuum to reduce oxidation.

• OSP: Baking can damage the organic solderability preservative. A short, low-temperature bake in a low-oxygen nitrogen environment is recommended. In severe cases, the coating may need to be removed and reapplied.

• ENIG: Baking can oxidize the underlying nickel layer, so a low-oxygen environment is recommended.

• General effects: Baking accelerates intermetallic compound (IMC) growth, which can create solderability problems such as weak wetting.

• Immersion silver: Immersion silver is sensitive to sulfur and chlorine. Baking can cause tarnishing or corrosion, so solderability must be verified.

• Immersion tin: Baking accelerates IMC growth and can significantly shorten the already limited shelf life, identified here as approximately 12 months. Sample-board validation is strongly recommended before baking.

• Last-resort recovery: Stripping and recoating can restore solderability, but this is often expensive. Scrapping and remanufacturing the boards may be more economical.

The bake profile should be customized according to board thickness, copper distribution, initial moisture content, and other board characteristics. To reduce damage to the inner-layer structure, the bake temperature should remain below the Tg of the inner-layer material.

4. Packaging, Storage, and Transportation

4.1 Packaging Evaluation

Packaging evaluation should consider material moisture sensitivity, physical protection, the characteristics of the final surface finish, and ESD requirements.

For most polymer-based laminates, packaging should include a moisture barrier bag, desiccant, and humidity indicator card. The bag should be heat sealed.

Tin-Lead Finish

The NCMS report indicates that the wetting performance of tin-lead finishes gradually decreases after 8–9 months and then tends to stabilize. The fundamental causes of solderability degradation are the growth and oxidation of the intermetallic phases Cu₆Sn₅ and Cu₃Sn, rather than the packaging itself. The thinnest areas, such as corners inside plated through-holes, lose solderability most rapidly, typically within 6–12 months. Other surface areas can generally retain solderability for 1–2 years.

Immersion Tin

Tin oxidizes relatively quickly, and moisture-barrier packaging can slow the oxidation process. However, as with tin-lead finishes, the main causes of solderability degradation are the growth and oxidation of Cu₆Sn₅ and Cu₃Sn intermetallic phases. These mechanisms are likewise not primarily related to packaging.

Immersion Silver

Immersion silver solderability is not highly sensitive to oxidation, but the finish is extremely sensitive to sulfur and chlorine compounds, which can cause a significant reduction in solderability. Packaging must prevent exposure to contaminants and humid air. Sulfur-absorbing, pH-neutral materials, such as corrosion-inhibiting paper, are typically used.

Electroless Nickel/Immersion Gold (ENIG)

The immersion gold layer is a thin, porous deposit that protects the underlying nickel from oxidation. Its packaging requirements are generally similar to those for tin-lead finishes.

Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG)

ENEPIG is a multifunctional finish with advantages over ENIG. It can support wire bonding and is less susceptible to black-pad defects. For soldering applications, its packaging requirements are similar to those for ENIG. For bonding applications, the surface should be protected from scratching with neutral, sulfur-free paper.

Electroplated Gold

Electroplated gold is generally thicker and has lower porosity, providing better protection for the nickel underlayer than ENIG. Its packaging requirements are generally similar to those for tin-lead finishes.

Organic Solderability Preservative (OSP)

OSP-finished boards must be completely dry and cooled to room temperature before packaging. Otherwise, condensation can damage the coating. Packaging materials should be sulfur-free.

4.2 Dry-Packaging Requirements

• Moisture barrier bag: WVTR ≤ 0.002 g/100 in²/24 h. The bag must also resist puncture.

• Desiccant: The quantity should be calculated using the formula in J-STD-033. The desiccant must be sulfur-free.

• HIC: The card should contain 5%, 10%, and 60% RH indicator points and must not contact the printed boards.

• Witness board: Optional. It can be used to monitor moisture absorption.

• Immersion silver boards: Use sulfur-protective paper, such as Silver Saver material, as an isolation layer.

• Sealing: Heat sealing is required. Partial vacuum may be used, but a complete vacuum should be avoided.

• Bulk-packaging limits: Each bag should contain no more than 10 boards when the board area is at least 0.093 m², or no more than 25 boards when the area is less than 0.093 m². Separate boards with sulfur-free paper or ESD bags.

4.3 Outer Packaging

Outer packaging must protect the boards against impact and movement. Packaging materials must be free from contamination, and ESD-sensitive boards must be clearly identified.

4.4 Marking

Markings should include lead-free/RoHS identification, ESD warnings, moisture-sensitivity symbols, date codes, and other applicable product information.

• Lead-free/RoHS compliant marking

• ESD marking

• Moisture-sensitivity marking

5. PCB Receiving, Storage, and Assembly

5.1 Before Opening the Package

Inspect the package for integrity before opening it. Open the package in the factory environment and meet one of the following conditions:

1. Place the boards in a dry environment at ≤ 10% RH for no more than 1 hour.

2. Complete dry repackaging within 30 minutes. The original desiccant and HIC may be reused if they remain suitable.

If the 60% indicator spot on the HIC has changed color during inspection, the HIC and desiccant must be replaced.

5.2 Storage

Dry packaging remains effective for at least 12 months when stored below 40 °C and 90% RH.

5.3 After Opening

Read the HIC immediately after opening. If the indication is abnormal, measure the board moisture content and bake or repackage the boards with fresh dry packaging when necessary.

5.4 Production Environment

Temperature and humidity must meet the requirements of J-STD-001. The production environment must prevent contamination and fingerprint transfer. ESD-sensitive boards should be handled in accordance with ANSI/ESD S20.20.

5.5 In-Plant Storage Containers

Workshop storage containers must be clean, sulfur-free, and suitable for ESD protection.

5.6 Soldering Operations

Before soldering, confirm that the board moisture content is below the maximum acceptable moisture content (MAMC).

5.7 Maximum Acceptable Moisture Content

The MAMC is typically 0.1%–0.5% by resin weight, depending on the board design, material construction, and soldering temperature.

5.8 Moisture-Content Evaluation

Moisture content can be evaluated by the weight-loss method described in IPC-TM-650, Method 2.6.28, by thermogravimetric analysis (TGA), or by capacitance testing.