IPC J-STD-004 flux classification: what ROL0, ROL1 and ROM1 mean
Codes such as ROL0, ROL1 or ROM1 appear on the technical data sheets of flux-cored wires, solder pastes and liquid fluxes. They are the classes of the IPC J-STD-004 standard, which describes a flux with three pieces of information: what it is made of, how active it is and how much halide it contains. This guide explains how to read them and how to use them to choose a flux.
Dickmann Srl · updated
How to read a J-STD-004 code
The code consists of three parts. The first two letters indicate the flux base, the third letter the activity level, the final digit the halide content. ROL0, for example, means: rosin-based flux (RO), low activity (L), with halides below 0.05 % by weight (0).
| Part of the code | Values | Meaning |
|---|---|---|
| Base (first two letters) | RO | Rosin: natural colophony |
| RE | Resin: synthetic resin or modified rosin | |
| OR | Organic: organic flux, often water-soluble | |
| IN | Inorganic: inorganic flux, for non-electronic uses | |
| Activity (third letter) | L | Low: low activity |
| M | Moderate: moderate activity | |
| H | High: high activity | |
| Halides (final digit) | 0 | Halides below 0.05 % by weight |
| 1 | Halides above 0.05 %: up to 0.5 % for L1, between 0.5 and 2 % for M1, above 2 % for H1 |
The standard also defines the test methods used to assign the class, including corrosion, surface insulation resistance (SIR) and halide content. The thresholds are those of revisions B and C; “halide-free” is not the same as “halogen-free”.
The most common classes in electronics
In electronics, low-activity fluxes are used above all, because their residues can remain on the board. More active fluxes are needed on difficult or oxidised surfaces and generally require cleaning. Some examples from the range of Dickmann flux-cored wires and AIM solder pastes:
| Class | Description | Examples in the range | Cleaning |
|---|---|---|---|
| ROL0 | Rosin, low activity, halides below 0.05 % | Alfa C, Dixtra No Clean, AIM Glowcore flux-cored wires; AIM H10 paste | Normally not required |
| ROL1 | Rosin, low activity, halides up to 0.5 % | AIM M8 paste (class according to J-STD-004B) | Assess according to specification |
| ROM1 | Rosin, moderate activity, halides between 0.5 and 2 % | Impetol B flux-cored wire | Recommended in electronics |
| ORH1 | Organic, high activity, halides above 2 % | — | Mandatory |
No-clean is not a class
“No-clean” is a commercial term, not a J-STD-004 class: it indicates a flux whose residues are designed to remain on the board without washing. In practice, no-clean fluxes are almost always class L0 or L1. If the board is to be conformally coated, if appearance matters or if the specification requires it, no-clean residues must also be removed.
The old designations R, RMA and RA, derived from the military standard MIL-F-14256, do not correspond exactly to the J-STD-004 classes either: RMA usually corresponds to low-activity fluxes, RA to more active fluxes. For a reliable comparison, always read the J-STD-004 class stated on the technical data sheet.
How to choose the class
For the liquid and gel fluxes in the range, see the page liquid and gel fluxes.
- Electronic boards without washing: low-residue L0 fluxes (for example ROL0).
- Halogen-free specifications: classes ending in 0 and, if required, products declared halogen-free according to the standard specified by the customer.
- Oxidised surfaces, brass, old copper: M or H classes, with cleaning of residues.
- Wave and selective soldering: no-clean liquid fluxes, alcohol-based or VOC-free, suited to the bath alloy.