Authored By:
Viktoria Rawinski
Rawinski GmbH
Kreuzwertheim, Germany
Summary
During dynamic times, electronics production faces global supply shortages, cost pressures and a higher development challenge. These challenges result in higher supplier and raw material change, higher quality deviations, higher waste levels and an additional environmental impact. Particularly in the PCB manufacturing industry, where volatile components outgas from the PCB substrate, solder paste and components at high temperatures during the soldering process and condense in the soldering machines as a toxic residue, the focus must be on the subject of condensate residues. Although some of this condensate residue is collected in the soldering machines during production, a certain amount of the condensate escapes and contaminates our environment as toxic hazardous waste.
It is therefore important to identify what the condensate consists of, what are its formation mechanisms and where it could be meaningfully and efficiently removed or at least inhibited in its formation. In order to increase the sustainability and environmental friendliness of electronics production, the topic of condensate formation, polymerization and crosslinking was theoretically investigated in detail in a previous paper: “Detailed Study of Condensate Residues - Analysis of the Responsible Reaction Partners as well as Reasons for Condensate Polymerization and Growth of Crystalline Structures in the Soldering Process”.
Furthermore, potential reaction mechanisms were investigated and substances were analyzed which may be involved in chemical polymerization and crosslinking reactions and thus in the formation of condensate residues. This theoretical work is the background for the next step - condensate analyses on the molecular level, identification of its components and verification of the chemical reaction processes.
Conclusions
Condensate samples from the inlet area, the peak area and the cooling area of a reflow soldering system are clearly different in their molecular signature. This is confirmed by the theoretical study of the previous paper "Detailed Study of Condensate Residues - Analysis of the Responsible Reaction Partners as well as Reasons for Condensate Polymerization and Growth of Crystalline Structures in the Soldering Process". Figure 23 gives an overview of the possible molecular components from the solder paste, printed circuit board and solder resist, which can outgas in the soldering process and react, polymerize and crosslink with each other depending on the reaction partner and temperature range.
Three main substances could be identified by the FT-IR analyses of the condensate residue. The condensate residues showed significant correlation in their molecular signal with the pure substances "2-methyl-4'-(methylthio)-2-morpholino propiophenones", "triaminotriazine" and "rosin". Based on the melting temperature of the identified substances, it can be assumed that the temperature range of the outgassing is not necessarily correlated with the soldering zone in which the condensate residue has the highest concentration of the substance.
On the one hand, the reason for this is the distribution of the soldering atmosphere in the soldering machine (extraction from the various zones and a redistribution of the soldering atmosphere, condensate management, etc.), but on the other hand it also depends on the size and reaction speed of the outgassing molecules that interact with each other. This is also demonstrated by the fact that, for example, crystalline growth of 2-methyl-4'-(methylthio)-2-morpholinopropiophenone takes place in a different area of the soldering system than the outgassing of its starting components.
Initially Published in the SMTA Proceedings
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