Difference between HumiSeal 1B31 and 1A33
HumiSeal 1B31 en 1A33 are two widely used Conforme coating materials in PCB-assemblage, Prototype PCB-assemblage, en SMT-assemblage, but they differ significantly in chemical type, performance, and application scenarios.
Understanding these differences helps manufacturers choose the right coating based on environment, cost, and reliability requirements.

Key difference: material type
The most fundamental difference is the coating chemistry:
- HumiSeal 1B31 → Acrylic coating
- HumiSeal 1A33 → Polyurethane (urethane) coating
Acrylic and polyurethane coatings have very different properties in terms of drying, durability, and resistance.
Drying and processing speed
HumiSeal 1B31 is known for its fast drying and easy processing, making it ideal for high-speed production lines in SMT-assemblage. It can become tack-free in around 10 minutes and reaches usable properties quickly
HumiSeal 1A33, on the other hand, typically requires longer curing time to achieve full performance, especially at room temperature
This means:
- 1B31 → better for fast turnaround and high throughput
- 1A33 → better for performance over speed
Chemical and environmental resistance
HumiSeal 1A33 provides much stronger chemical resistance and durability compared to 1B31. Polyurethane coatings are specifically known for resisting solvents, abrasion, and harsh environments
HumiSeal 1B31 offers good moisture protection but is less resistant to aggressive chemicals.
So:
- 1B31 → general protection (humidity, dust)
- 1A33 → harsh environments (chemicals, industrial exposure)
Herwerken en repareren
This is one of the biggest practical differences in PCB-assemblage:
- 1B31 (acrylic) → very easy to remove and rework using solvents
- 1A33 (urethane) → difficult to remove due to high chemical resistance
Voor Prototype PCB-assemblage, 1B31 is usually preferred because engineers often need to modify or repair boards.
Flexibility and mechanical performance
Both coatings offer flexibility, but their behavior differs:
- 1B31 → flexible and suitable for general applications
- 1A33 → more durable and resistant to mechanical stress, abrasion, and long-term wear
Typische toepassingen
HumiSeal 1B31 is commonly used in:
- Consumentenelektronica
- LED drivers and power supplies
- General SMT-assemblage production
- Prototype PCB-assemblage (due to easy rework)
HumiSeal 1A33 is commonly used in:
- Industrial electronics
- Automotive systems
- Aerospace and defense applications
- Harsh environments requiring chemical resistance
Cost and production considerations
- 1B31 → lower cost + faster processing
- 1A33 → higher cost + better long-term protection
For large-scale PCB-assemblage, the choice often depends on whether speed or durability is the priority.
Summary comparison
| Functie | HumiSeal 1B31 | HumiSeal 1A33 |
|---|---|---|
| Chemistry | Acryl | Polyurethaan |
| Drying speed | Very fast | Slower |
| Herwerkbaarheid | Easy | Difficult |
| Chemische weerstand | Matig | Hoog |
| Kosten | Onder | Higher |
| Geschikt voor | General electronics | Harsh environments |
Definitief inzicht
The choice between HumiSeal 1B31 and 1A33 depends on your application:
- Kies 1B31 voor fast, cost-effective, and rework-friendly coating in PCB-assemblage en SMT-assemblage
- Kies 1A33 voor maximum durability and chemical resistance in demanding environments
In practice, many manufacturers use 1B31 for standard products en 1A33 for high-reliability or industrial applications, especially after validation in Prototype PCB-assemblage.
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