Humidity Tips

By Yonela Mofokeng, MD

A practical note on humidity control, for teams storing reels, paste and moisture-sensitive parts in workable floor conditions.

Moisture faults usually start with something small on the SMT line: reels left open too long, MSL labels not checked, or a board lot loaded without bake status. Humidity Tips is a floor note for South African electronics teams that want cleaner handling around storage, prep and placement.

Humidity control only works when storage habits are written down clearly. On SMT SA jobs in Gauteng, KwaZulu-Natal and the Western Cape, the common misses are open reels, paste left out too long, and missing bake records on moisture-sensitive parts.

Humidity checks before reels open

• Room RH and temperature logged
• Reel bag condition checked before opening
• MSL label and exposure time recorded
• Paste batch and out-time written up

Read this note alongside storage, placement and reflow process pages. Humidity faults seldom appear in one step only, so the reel room, kitting bench and oven record all need to agree.

How Humidity Tips affect solder paste and FR4 handling

Humidity Tips deals with workable control for reels, paste and moisture-sensitive parts on an SMT floor. It helps teams store materials more consistently when room conditions are shifting through the day. Use it to support handling rules before moisture creates assembly problems.

Start with the material that is most moisture sensitive on the build. Coastal air in Durban and Cape Town can shift through the day, while inland sites around Johannesburg often see dry mornings followed by storm humidity later on. Those changes affect how long reels stay exposed, how paste behaves after conditioning, and when a bake decision must be made.

Take a photo of the MSL label and the opened bag as soon as the pack is issued. Add the date, time and operator name on a simple card near the kitting area so the next shift does not guess exposure history. That small record is often more useful than a long incident report after popcorning or poor wetting appears.

South African moisture handling realities

Humidity control in South Africa is rarely constant for a full production day. Sites near the coast may need tighter checks on opened reels and desiccant packs, while inland workshops must watch sudden weather swings, power cuts and storeroom doors opening during dispatch activity. If the line is running live product, note whether the lot is fresh stock, returned material or a part-loaded reel from an earlier job.

Sea air can shorten the safe window for poor storage habits, especially on fine-pitch assemblies and moisture-sensitive ICs. Dry Highveld conditions do not remove the MSL risk either, because bags get opened, parts wait at prep, and line stoppages stretch exposure time beyond what the label allows. First-article records should therefore include storage status, not only placement and solder results.

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