1. Selective stamp soldering – Solder joint analysis
Analysis of solder joints in the selective stamp soldering Written by Fehérvári Péter Mentor: Csurka Péter
Automotive Electronics
Confidential | Fehérvári Péter | 22/04/2011 | © Robert Bosch GmbH All rights reserved, also regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the event of applications for industrial property rights.

2. Solder-ball forming during stamp soldering
Solder ball forming is a phenomenon caused by many factors and manifested in small solder alloy balls around the solder joint
The possible causes are improper fluxing or preheat profile, wetting problems because of surface contaminations, solder mask defects, escaping gases from the PCB laminate

3. Solder-ball forming during stamp soldering
The concerned PCB-s showed uneven PTH plating surface which can be a root cause of blow holes
Problems occured with immersion tin and also with HASL plated PTH barrels.
Although the surface of the HASL was satisfactory, the underlying copper plating was uneven and critical thin.

4. Solder-ball forming during stamp soldering
The mechanism of solder ball forming is in correlation with the escaping gases from the PCB laminate resin, caused by the higher temperatures and contact times used in lead free technology
The higher copper dissolution rate of the lead free solder alloy aggravates the problem, the critical thin copper plating can completely dissolve which results free out gassing from the PCB laminate.

5. Solder-ball forming during stamp soldering
The proposed actions are primarily to eliminate te root cause, which means strict quality control over the PCB supplier’s products. Lead free soldering is more sensitive of PCB quality.
The yield can be improved by heat treating of the PC boards, thus removing volatile materials from the laminate.

6. Manufacturing and process regulations for EL13
The task was to collect the related documents; regulations, datasheets, heat profiles etc. for each production phases and organize them to a html coded table
To collect the required documents, the concerned engineers has been contacted and the database of Salzgitter has been examined