Moisture Barrier Bag (MIL-PRF-81705 Type I) — Procurement Guide & Supplier Specs

MIL-PRF-81705 governs the foil/PET/polyethylene laminate used for moisture barrier bags (MBBs) in electronics, medical, and defense packaging. This guide explains the four common Types and Classes, what spec lines actually matter for procurement, and how to write a clean RFQ that gets apples-to-apples quotes from suppliers.

Types and Classes at a glance

MIL-PRF-81705 covers four Types (I–IV) by construction and three Classes by water-vapor transmission rate (WVTR). For surface-mount components and PCB assemblies, the workhorse is Type I, Class 1: a metallized 4-ply laminate (PET / foil / nylon / LDPE), WVTR ≤ 0.0005 g/100in²/24h at 100°F / 90% RH.

Type II is similar without the foil layer and is reserved for less-critical applications. Type III is heavy-duty for long-term storage. Always quote the Type, Class, and laminate thickness — a "barrier bag" without those is unverifiable.

Heat seal and seal integrity

The bag is only as good as its seal. Procurement specs should mandate a 10 mm minimum continuous heat seal, dwell time and temperature documented per the seal-validation report.

Suppliers should ship coupons from each lot so the buyer's incoming QA can pull bags for ASTM F88-style peel strength checks. If your contract manufacturer is reusing bags, the seal width must be sufficient to allow a second seal above the original cut line.

Desiccant and humidity indicator card pairing

An MBB without correctly-sized desiccant is a sealed humid pocket. IPC/JEDEC J-STD-033 specifies the desiccant volume per bag size.

The standard pairing is silica-gel desiccant + 5%/10%/60% HIC (Humidity Indicator Card); if the 10% dot turns pink, the bag is breached. Bulk buyers should source MBB + desiccant + HIC + label as a kitted SKU with one line item and one lot code — easier to audit, easier for incoming inspection.

MOQ and lead-time benchmarks

Stock sizes from major North American distributors ship same-day in cases of 100. Custom sizes typically require MOQ 1,000–5,000 bags and 3–5 week lead time including artwork plate, depending on whether the bag is plain or printed with PO number, MSL level, and customer logo.

Add 1–2 weeks for first-article peel and WVTR test reports. Tyson Supply Chain stocks the common 8×10, 12×16, 18×24 inch sizes at our Los Angeles warehouse.

Frequently Asked Questions

Is MIL-PRF-81705 Type I Class 1 the same as ESD-shielding?

No. MIL-PRF-81705 governs moisture barrier performance. ESD shielding is governed separately by ANSI/ESD S541 (and the older MIL-B-81705 Type III, which is the static-shielding type). For moisture-sensitive AND ESD-sensitive parts, you need a bag rated to both. Most production MBBs in electronics are dual-rated; always confirm both certificates on the data sheet.

What WVTR should I require for high-pin-count BGAs (MSL 5–6)?

Class 1 (≤ 0.0005 g/100in²/24h) is the safe default for MSL 4 and above. For MSL 5/6 packages with long shelf-life expectations, also tighten the desiccant-volume calculation per J-STD-033 and require a 60% HIC dot (not just 10%) so any humidity excursion is caught early.

Can I source MIL-PRF-81705 bags off-the-shelf without DLA approval?

Yes for commercial use — many suppliers self-certify against the MIL-PRF-81705 dimensional and performance requirements without being on the DLA-qualified products list. For DoD or DLA prime contracts, require QPL listing. For commercial electronics, a third-party lab test report (Intertek, SGS) is the typical evidence.

How do I write the RFQ so vendor quotes are comparable?

Specify (1) Type and Class, (2) inside dimensions (W × L), (3) layer construction and total thickness, (4) seal width, (5) printing requirements, (6) test reports required (WVTR, peel, ESD if applicable), (7) packaging unit (loose, 100-case, 1000-case), and (8) lot traceability. Vendors quoting on incomplete RFQs will assume the cheapest construction.