Directive 2002/95/EC from the European Parliament forbids the use of lead, mercury, cadmium and hexavalent chromium, as well as flame retardants PBB and PBDE, in electrical and electronic products such as home appliances, telecommunication devices and devices for entertainment electronics.
The materials named above, such as lead, mercury, etc., are no longer permitted to be contained in connectors.
It must be possible to process the connector in new, controlled production processes, which differ considerably from the old ones.
There must be forward and backward compatibility with regard to the connection finishing in association with the production process.
Which consequences does this have for the connector?
At the moment, the PCB connectors are predominantly finished with a tin/lead surface (90% tin and 10% lead) in the connection area.
The main purpose of the lead component is to reduce the surface tension of the tin, and to avoid whisker formation.
In the soldering paste, the lead is responsible for reducing the high melting temperature of the tin.
By eliminating the lead in the soldering pastes, the melting temperature of the soldering paste is increased by approximately 20° C (36° F). This considerably increases the demands on the insulator's thermal stability.
With the insulator materials currently used, in addition to the lead present in the connection area, it is also possible that halogens are released during the soldering process, which must be avoided in the future.
As a consequence, ODU will convert to lead-free finishing of the soldered connections in 2004, which means that only pure tin will be used in the finishing process. ODU has already switched over to LCP in the insulator materials.
In brief, the connector of the future must display the following fundamental properties:
- Lead-free surface finishing in the soldered connection area
- High thermal stability up to 260°C (500° F)
What does this mean for ODU distributor Clarke & Severn Electronics ' customers?
To assess the technical comparability, extensive field tests have already been carried out at key customers; in these tests, connectors finished without lead were subjected to different soldering processes. With the help of photomicrographs and X-ray examinations, it is possible to furnish proof that the practical suitability is ensured without restrictions.
No negative differences could be determined, even during long-time and aging simulations.
Corresponding shear tests demonstrate strength comparable to soldered connections containing lead. The subject of process compatibility is still especially relevant.
In this regard, field tests have shown that, in addition to conventional soldering of connection pins that contain lead with soldering paste that contains lead, the following combinations are also possible:
- Connection pins finished without lead soldered with soldering paste containing lead
- Connection pins finished without lead soldered with soldering paste without lead
- Connection pins finished with lead soldered with soldering paste without lead
In contrast to the conventional soldering process, it can be established that when lead-free soldering pastes are used, the temperature profile during the entire process is approximately 20° C (36°F) higher, so that short-term (150 sec.) peak temperatures of 245° C (473° F) and higher can arise (peak up to 260°C or 500° F), which the insulator plastic must withstand without damage.
By using LCP as an insulator material, as was already mentioned, it is possible to reach the necessary thermal stability, on the one hand, while also simultaneously fulfilling the requirement of halogen-free processing, on the other.
Now that ODU has already adapted the insulator material to the process conditions, which means that LCP is used for all SMT and THR product series, the finishing process will be converted to 100% pure tin in 2004.
In this way, all legal requirements will be met before the deadline set by the law, which represents a considerable advantage for both the final customer and for the users of ODU's connectors.