HASL / HAL (Hot Air Solder Leveling) solder alloys for printed circuit boards
Lead-free and tin-lead bars for the HASL solder pots of PCB manufacturers
HASL (Hot Air Solder Leveling, also known as HAL) is the surface finish in which the printed circuit board is dipped into a bath of molten alloy and then levelled with hot-air knives. Dickmann supplies PCB manufacturers with lead-free and tin-lead alloys for HASL solder pots, in Dixtra Electronic bars of approx. 1 kg.
Why HASL
HASL deposits a layer of solder alloy on the copper pads: the surface is already solderable, keeps well over time and is among the most economical finishes. Its limitation is planarity: the deposit is less uniform than that of chemical finishes, which matters for very fine-pitch components.
Leaded HASL is the traditional version, now reserved for boards intended for applications exempted from the RoHS Directive. For all others, lead-free HASL (LF-HASL) is used, with lead-free alloys with low or no silver content.
Alloys for HASL solder pots
These are the alloys we supply to printed circuit board manufacturers. For data on the individual alloys see SAC0307, Sn99.3Cu0.7 and 99SnCuNiGe (SN100C equivalent).
| Alloy | Type | Silver | Notes |
|---|---|---|---|
| SAC0307 | Lead-free | 0.3 % | Low silver, lower cost |
| Sn99.7Ag0.3 | Lead-free | 0.3 % | No added copper, low silver |
| Sn99.3Cu0.7 | Lead-free | — | Silver-free, the most economical |
| 99SnCuNiGe (SN100C equivalent) | Lead-free | — | Silver-free; nickel and germanium limit copper erosion and dross |
| Tin-lead alloys | Leaded | — | Traditional HASL, for boards intended for RoHS-exempt applications |
Other lead-free alloys on request. All alloys are manufactured to EN ISO 9453:2020.
Managing the HASL solder pot
In HASL the bath is in contact with large areas of bare copper, so copper dissolution is faster than in wave soldering. As dissolved copper increases, the liquidus and viscosity of the alloy rise, the deposit becomes less uniform and levelling defects increase.
The solder pot temperature must be set according to the machine manufacturer's recommendations and the characteristics of the alloy.
- Top up with bars of the same alloy as the bath, at regular intervals.
- Monitor dissolved copper and iron with periodic bath analyses.
- When copper exceeds the limits, dilute or replace part of the bath.
- Remove dross and slag from the surface of the solder pot regularly.
Bath analysis and dross recovery
Dickmann analyses customers' baths on a sample of at least 250 grams of alloy and sends an impurity report with recommendations for correcting them. Dross and process residues can be returned for recovery. Full details on the page of our analysis and recovery services.
HASL, ENIG, OSP or immersion tin?
A qualitative comparison of the most common surface finishes.
| Finish | Planarity | Cost | Notes |
|---|---|---|---|
| Leaded HASL | Medium | Low | Traditional finish, only for RoHS-exempt applications |
| Lead-free HASL | Medium | Low | Robust and highly solderable; less suitable for very fine pitch |
| ENIG (electroless nickel immersion gold) | High | High | Flat surface, suitable for fine pitch and BGA |
| OSP (organic solderability preservative) | High | Low | Flat surface, shorter shelf life |
| Immersion tin | High | Medium | Flat surface; the risk of whiskers must be managed |
Formats and documentation
HASL alloys are supplied as Dixtra Electronic bars: trapezoidal cross-section, approx. 1 kg, 25 kg boxes, minimum order one box. Each lot is supplied with a certificate of analysis; RoHS and REACH declarations and safety data sheet on request.
Frequently asked questions about HASL alloys
Request a quote for HASL alloys
Tell us the alloy, the number of 25 kg boxes and your annual consumption