Leaded or lead-free: what changes when an old board is rebuilt
Most legacy boards were soldered with tin-lead. Today many fabricators and component suppliers work lead-free by default. That is usually fine – but it has to be a conscious decision, not an accident.
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Why this matters
Lead-free solders melt at higher temperatures (around 217–220 °C for common SAC alloys versus 183 °C for tin-lead). Components, laminate and finish must survive this. Old component types and some base materials were never specified for it.
Surface finishes compared
| Finish | Properties | Typical use |
|---|---|---|
| HASL tin-lead | Robust, easy to solder, not RoHS-compliant | Legacy boards, applications outside RoHS scope |
| HASL lead-free | Robust, uneven surface | Through-hole and coarse SMD |
| ENIG (nickel-gold) | Flat, good shelf life | Fine-pitch SMD, high reliability |
| OSP | Cheap, limited shelf life | Consumer volume production |
| Immersion tin / silver | Flat, sensitive to handling | Specific applications |
RoHS: does it apply to you?
The EU RoHS Directive restricts lead in electrical and electronic equipment, but not every product is in scope, and there are exemptions. Means of transport such as aircraft are outside its scope, and some applications are covered by specific exemptions. Many aerospace and defence customers therefore still specify tin-lead. Clarify with your quality or regulatory department which requirement applies before the fabrication drawing is finalised.
We state the finish and solder requirement explicitly in every fabrication drawing, so the fabricator does not decide for you.
Mixing old parts with lead-free processes
If original tin-lead components are used on a lead-free board, or lead-free components on a tin-lead board, the solder joints can become less reliable. The rule is: decide one process, check every component's maximum soldering temperature and finish, and document the decision.
Questions
Can I still order boards with tin-lead finish?
Yes, many fabricators still offer HASL tin-lead, particularly for industrial and aerospace customers. We specify it if your application requires it.
Is lead-free less reliable?
Not in general. Lead-free processes are well understood today. Problems usually arise from mixing processes or using parts not rated for the higher temperatures.