Lead-free solder and RoHS — the requirements behind the reflow profile

The solder tin you work with today is chemically a different material than the one an electronics operator used twenty years ago. The change doesn't just come from new technology but from legislation — the EU's RoHS Directive — which has changed what solder tin can consist of and thus how the entire reflow process must be controlled.

RoHS (Restriction of Hazardous Substances) is an EU directive that limits the use of a number of hazardous substances in electrical and electronic equipment. The directive has since been tightened — first with RoHS 2, later with the addition of more phthalates in 2015 — and from 22 July 2019 it covers virtually all electrical and electronic equipment on the European market, with only a few exceptions.

• 01Lead — previously a fixed component of solder
• 02Mercury and cadmium
• 03Hexavalent chromium
• 04Flame retardants PBB and PBDE
• 05Four selected phthalates added in a later update

Since August 21, 2023, new trucks over 3.5 tonnes must have second-generation smart tachographs installed. Smart tachograph 2 communicates digitally with authorities at roadside checks (ITS communication) and automatically records border crossings and ferry/train trips.

• 01Always follow the documented reflow profile for the specific product — never guess on the temperature
• 02Keep an eye on the oven's zones so heating and cooling happen at the right pace
• 03Be aware of the risk of 'tin whiskers' — thin metal wires that can grow from pure tin surfaces over time and create short circuits
• 04Report immediately if you see signs of overheating, discolouration or skewed components after reflow

RoHS is about what is allowed to be in the product when it is made. The WEEE directive takes over when the product is one day outdated: it imposes on manufacturers a responsibility to collect and recycle electronic waste so that the materials — including the metals you work with every day — can be extracted and reused instead of ending up as waste. The two sets of rules therefore hang together: RoHS limits the damage while the product is used; WEEE limits the damage when it should no longer be used.

As an operator you rarely feel WEEE directly in your everyday life but the documentation you help create about components and materials is part of the foundation that later makes it possible to properly comply with both rule sets.

“A few degrees in the reflow oven sounds like nothing — but it is the difference between a durable solder joint and one that fails at the customer.”

— Professional view on materials in electronics production.