A PCBA that has been assembled and has passed test does not always need moisture barrier packaging. The boards that do are those with MSL 2 or higher components on them (MSL 1 needs no dry packing) that also meet any one of the following: they will be heated again later (rework, repair, a second reflow), they will be stored for a long time or in a warehouse where humidity is hard to control, they travel long distances by sea or through large temperature swings, or the customer specification requires it. In these cases we suggest sealing the board in an anti-static foil bag together with a humidity indicator card and desiccant.
J-STD-033 covers components, not whole boards. There is no single standard at board level; the usual basis is the MSL of the sensitive components on the board plus the customer specification. If you work in warehousing or quality and have to decide “does this need vacuum packing”, walk through Figure 1 first.
Figure 1. Decision flow: does this PCBA need moisture barrier packaging? (General case; still depends on the individual case and the customer specification.)
- PCBA assembled and tested. Does the customer specification define the packaging? Yes → follow the customer specification.
- If no: does the board have MSL 2 or higher components and will it be heated again (rework, repair, second reflow, or mounted on another board as a module)? Yes → Top level: anti-static foil bag + humidity indicator card + desiccant, with MSL and sealing date marked on the bag.
- If no: long storage, hard-to-control warehouse humidity, or sea freight / long transport with large temperature swings? Yes → Top level: anti-static foil bag + humidity indicator card + desiccant; a small number of boards waiting for use can sit in a low-humidity dry cabinet.
- If no: does the board leave the ESD protected area (EPA)? Yes → Middle level: anti-static shielding bag + outer carton cushioning; vacuum is not always needed.
- If no: Entry level: anti-static transfer tray + foam.
Diamonds are decisions and boxes are conclusions; the three levels are distinguished by color and text label.
Table 1. Situation → suggested packaging level
| Situation | Main risk | Suggested packaging | Basis |
|---|---|---|---|
| Next station inside the plant, moving within the ESD protected area | ESD, impact | Anti-static transfer tray + foam; no moisture bag needed | This site’s guide to choosing anti-static bags |
| No MSL 2 or higher components, no heating after shipment, short delivery, controlled environment | ESD | Anti-static shielding bag + outer carton cushioning; vacuum not always needed | Component supplier handling document: boards that will not see a high-temperature process again need no special handling |
| MSL 2 or higher components, and later rework, repair, second reflow, or mounting on another board as a module | Cracking and delamination of the package when heated after absorbing moisture | Anti-static foil bag + humidity indicator card + desiccant, with MSL and sealing date marked | J-STD-033D, Chapter 6 (board rework) |
| Long-term storage (stock boards, spare boards, repair stock) | Flux residue + moisture: leakage, corrosion | Same as above; a small number of boards waiting for use can go in a low-humidity cabinet | University journal research |
| Sea freight, long distance, large temperature swings | Condensation inside the container | Same as above, then packed in an outer carton | Container condensation white paper |
| Customer specification applies | Per the specification | Per the specification (MSL label, indicator card dots, desiccant quantity, etc.) | No single standard at board level |
| Conformal coating or potting already applied | The coating is permeable to moisture | Do not skip packaging because of it; decide as above | Conformal coating data, university research |
Table 2. Packaging materials and what they do
| Material | What it does | What to watch on a PCBA | Jiahon |
|---|---|---|---|
| Anti-static foil bag (MBB) | Blocks moisture and also shields against static | Must hold the whole board; pins and standoffs can puncture the bag | Available, custom sizes: anti-static foil bag |
| Humidity indicator card (HIC) | Shows on opening whether the inside of the bag took up moisture | Place where it is visible as soon as the bag is opened | Available: blue six-dot humidity indicator card; blue is dry, pink is humid; the color change is reversible (once the 60% dot has changed, do not reuse the card); the product page figure shows dots from 10% to 60% |
| Desiccant | Adsorbs residual moisture in the bag | Quantity depends on bag volume and water vapor transmission rate; IPC-1601A Appendix B has a quantity table by bag size | Please inquire |
| Anti-static foam, cushioning sheets | Separates sharp parts and holds the board | Separate the board before it goes into the bag | Available: anti-static EVA foam |
| Heat sealer, vacuum sealer | Closes the bag | Check the seal after sealing | Please inquire |
| Low-humidity dry cabinet | Temporary storage after opening, or while waiting for rework or shipment (not packaging) | Its job is to stop the board absorbing more moisture | Available: ultra-low humidity electronics dry cabinet; the product page lists two humidity classes, 1% to 10% RH and 1% to 3% RH |
| Temperature and humidity meter | Monitors the sealing area and the warehouse | Mount where it represents the air on site | Available: temperature and humidity meter HT3C21; LCD shows temperature and relative humidity |
1. Tell the two moisture risks apart
The first needs heat to happen. A component takes up moisture; when it goes through the reflow oven or is heated by hot-air rework, the moisture turns to vapor at once and the package may crack or delaminate (the popcorn effect). The scope of J-STD-033 is components that go through whole-board reflow, and it also covers hot-air spot rework. A semiconductor supplier’s handling document also states that a soldered board that will not go through reflow or another high-temperature process again needs no special handling.
The second happens even without heat. After flux residue absorbs moisture, under high humidity and voltage bias it can leak current or corrode, and in serious cases metal dendrites grow and cause a short (electrochemical migration). Several papers from university research teams point to residue type, humidity and cleanliness. This has nothing to do with MSL: it depends on how clean the board was, what humidity it sits in and for how long. For how to show customers that a board is clean, see How to prove a circuit board is clean.
2. J-STD-033 covers components; there is no single standard at board level
- J-STD-033: handling, packing and use of moisture-sensitive components. The 2018 D edition contents have a separate chapter on board rework (Chapter 6), and 6.2 is baking of assembled boards, but the body of the standard is still about components.
- J-STD-075: classification of non-IC components (passives, connectors, switches, etc.) for assembly process sensitivity, including moisture sensitivity levels and marking.
- IPC-1601A: guidelines for handling and storage of printed boards (bare boards), covering the assembly and soldering stages. Sources differ on whether it applies directly to finished soldered boards; check the source text.
Among the IPC / JEDEC documents found for this article, none sets packaging rules specifically for a finished, soldered PCBA. In practice, people identify the sensitive components on the board, use their MSL as the handling basis for the whole board, and then add the customer specification on top. Where a module supplier exists, the whole module is controlled as a moisture-sensitive item and a pre-bake is required before repair. This is industry practice, not standard text.
3. The 4 cases that need moisture barrier packaging
- It will be heated again. Rework, repair, a second reflow, or the board will be mounted on another board as a module. A component’s exposure time accumulates from the moment the package is opened; reflow or rework does not reset it, and drying according to the standard is what resets it. If a board sits in the plant for a long time after reflow, its components may already be past floor life at rework and need baking first; to stop the clock, keep the board in a low-humidity environment. Component suppliers word this slightly differently; follow the component data.
- Long storage, or hard-to-control warehouse humidity. Stock boards, spare boards and repair stock all belong here. “Long” has no universal number of days; it depends on warehouse temperature and humidity, how clean the board is, and whether it may be reworked later.
- Sea freight or long distance with large temperature swings. Temperature and humidity change sharply in transit and water can condense inside the container; container condensation research and desiccant suppliers both recommend ventilation and desiccant. A board sealed in a foil bag already has one layer of separation.
- The customer specification requires it. The customer may specify an MSL label, indicator card dot colors or a desiccant quantity. Where there is a specification, it prevails.
Conversely, if the board has no MSL 2 or higher components, will not be heated after shipment, will reach the customer soon and the environment is controlled, an anti-static bag or anti-static shielding bag plus outer carton cushioning is usually enough. This is the general case and still depends on the individual case and the customer specification.
4. How to set up the packaging
Dry packing has four parts: moisture barrier bag (MBB), desiccant, humidity indicator card and label; what each does is explained in What is MSL for moisture-sensitive components?. Points for applying it to a PCBA are below; see Table 2 for materials.
- The board must be dry before sealing. For components J-STD-033 dries first and then bags; doing the same for boards is a reasonable extension. A board that has already taken up moisture and is sealed in simply locks the moisture in.
- Do not let the board puncture the bag. Protruding pins, standoffs and connectors can puncture or tear the bag. Separate them with foam first, and check the bag surface and seals after sealing.
- Mark MSL and the sealing date on the bag, and put the humidity indicator card where it can be seen as soon as the bag is opened.
- Desiccant quantity follows the bag. Calculate from bag volume and water vapor transmission rate; a bag you seal yourself has no ready-made shelf life, so ask the bag supplier for the transmission rate data.
- When you need static protection but not moisture protection, a shielding bag is enough. A shielding bag is not a moisture barrier bag; unless the bag states a water vapor transmission rate, use a foil bag for moisture protection.
5. What to do after opening
- Look at the card and record the time. All six dots blue means the inside of the bag was dry; if any dot has turned pink, the bag has been exposed to moisture, so isolate the board and check before it goes on the line. Also record the opening time and accumulate the exposure hours.
- If the time limit is exceeded or the card has changed color, do not force the board onto the line. Decide whether to bake according to J-STD-033 Chapter 6 and the customer specification. Before rework in particular, check how long the board sat between reflow and rework and what floor life the sensitive components on it have.
- Do not apply the default component baking conditions directly to a board. Connector plastic housings, batteries and low-temperature carriers may not tolerate high temperature, and industry experts warn against using the component default high-temperature values; the conditions depend on the heat-sensitive parts on the board, the board material and the customer specification. Surface finish also limits baking: a PCB maker’s data says baking is not recommended for OSP boards, and if necessary use the low end of the temperature range and a short time (single source; general case; still depends on the individual case).
- Re-seal boards that are not used up. Replace the desiccant and check the card before sealing, or put the boards in a low-humidity dry cabinet for temporary storage. A dry cabinet stops the board absorbing more moisture; it does not replace baking.
6. Conformal coating and potting are not moisture protection
Most organic coatings let water molecules through, and university research also points out that the effect of conformal coating is limited by board characteristics and process. For boards already coated or potted, still decide using the four cases above: packaging blocks moisture from outside but cannot block the residue the board carries, so cleanliness has to be handled before packaging.
If you need to confirm bag size, the number of humidity indicator cards or the sealing method, please contact Jiahon; we can help match a setup to your board size and shipping conditions. This article is a general explanation. For the actual packaging specification and baking conditions, follow the component supplier data for the parts on the board, the customer specification and the current edition of the IPC / JEDEC standards.
Further reading
To look at the related process steps together, continue with these:
- What is MSL for moisture-sensitive components? Packaging, exposure time and baking in J-STD-033
- How to choose anti-static bags: antistatic, conductive and shielding compared, and when a foil bag is required
- How to prove a circuit board is clean: four documents for passing a customer audit in one go
- How to choose WIP transfer packaging for an electronics plant: from ergonomics to set-count calculation, an evaluation report taken apart
- Dry cabinet vs nitrogen cabinet: 4 selection points for storing moisture-sensitive items
- Storage and baking conditions for moisture-sensitive components: what to do in each of 4 states after opening
- What is the popcorn effect: why moisture-laden ICs and boards burst in the reflow oven: what happens to a poorly packed board in the oven
Related products in this article
Specifications are as on each product page; for actual configuration, price and lead time, please inquire.
- Anti-static foil bag (custom sizes; moisture barrier plus static shielding)
- Blue six-dot humidity indicator card (shows on opening whether the bag took up moisture)
- Ultra-low humidity electronics dry cabinet (the product page lists two humidity classes, 1% to 10% RH and 1% to 3% RH)
- Anti-static shielding bag (flat-top and zip-lock styles; for moisture protection use a foil bag)
- Anti-static EVA foam (black carbon type; the standard model is a 6-compartment tray, and there are custom size, thickness and compartment versions with adhesive back)
- Anti-static logistics transfer box (anti-static PP material, with-lid and without-lid versions, several sizes)
- Temperature and humidity meter HT3C21 (LCD shows temperature and relative humidity)
Standards and sources
The standards cited here should be checked against the current edition from the issuing body.
- IPC/JEDEC J-STD-033D, Handling, Packing, Shipping and Use of Moisture, Reflow, and Process Sensitive Devices. Issuers: IPC (Global Electronics Association) and JEDEC.
- ECA/IPC/JEDEC J-STD-075 (2008 edition), Classification of Non-IC Electronic Components for Assembly Processes. Issuers: ECA, IPC, JEDEC.
- IPC-1601A, Printed Board Handling and Storage Guidelines. Issuer: IPC (Global Electronics Association).
- IEEE TCPMT 2025, Enhancing Humidity Robustness of Electronics: Understanding the Crucial Role of Solder Flux Chemistry in Determining Humidity Boundary for Failure. Issuer: IEEE (IEEE Transactions on Components, Packaging and Manufacturing Technology); listing page: Technical University of Denmark research database.
- Moisture in Sea Containers: What causes the problems and how to solve them? (2018 white paper). Issuer: Virginia Tech, Center for Packaging and Unit Load Design.