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Reduction of Condensate Residues in the Reflow Process
Increased electronics manufacturing results in an increased amount of condensate residue. The problem is not only to meet the increased cleaning requirements with increasing production, it is much more the absence of knowledge about the condensate residue formation process and how this residue can be minimized and inhibited in its formation.
Production Floor
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Authored By:
Viktoria Rawinski
Rawinski GmbH
Bavaria, Germany
Summary
Increased electronics manufacturing results in an increased amount of condensate residue. The problem is not only to meet the increased cleaning requirements with increasing production, it is much more the absence of knowledge about the condensate residue formation process and how this residue can be minimized and inhibited in its formation. Some of the substances in the condensate residue are harmful to health. They cause skin irritations and allergic reactions. Some of them contaminate the environment as toxic hazardous waste. Therefore, this paper focuses on the reduction of condensate residues from a soldering process based on previous white papers “Detailed Study of Condensate Residues in the Soldering Process – Analysis of the Responsible Reaction Partners as Well as Reasons for Condensate Polymerization and Growth of Crystalline Structures” and “Molecular Fingerprint of Condensate Residues in the Soldering Process – Detailed FT-IR Spectroscopic Analyses and Identification of Reaction Partners” presented at SMTA International Conference in 2021 and 2023.
After theoretical study of the formation process and FT-IR spectroscopic analyses of the condensate residues, substances were identified that play a significant role in condensate formation. Three of these substances need to be highlighted: Rosin from the solder paste, photo initiator from the solder mask and Triaminotriazine from the PCB substrate. Based on these results, experimental tests were performed with condensate residue samples from soldering process and reaction partners that were identified as potentially effective in inhibiting polymerization, cross-linking reactions and crystallization processes.
Condensate residue components can be physically and chemically bound and selectively modified. This allows the inhibition of polymerization and cross-linking processes, the reduction of crystalline growth and the effective control of chemical reactions. For the experimental procedures, samples of various condensate residue from the soldering process were combined with the reagents and were then subjected to a thermal process. The following FT-IR analyses enable the identification of the resulting reaction products. This allows the visualization of the chemical changes and helps to understand the chemical reaction processes.
Important conclusions can be drawn as a result. Experiments have shown that it is possible to successfully modify crystalline structures of the photo initiator in the condensate residue by a specific chemical reaction, and thus inhibited crystalline growth. It is also possible to modify the polymerization and crosslinking behavior of rosin in the condensate residue in so far that a crosslinking reaction can be effectively inhibited. This work is therefore another important step on the way to sustainable electronics production, increasing maintenance cycles combined with reduced cleaning requirements.
Conclusions
In summary, it could be shown under laboratory conditions that it is possible to influence chemical processes in the condensate residue and to inhibit polymerization, cross-linking reactions and crystallization processes.
Reagent A led to a peak reduction and moderate changes in the spectrum of the condensate sample from the peak range. While reagents B and C did not trigger any visible change in the spectrum. On the one hand, this may be due to the fact that reagent A was specifically selected for chemical manipulation of the cross-linked rosin components, where substances B and C are chemically less effective. On the other hand, condensate from this area of the reflow machine was subjected to a so-called pyrolysis, which already led to a similar change in the chemical structure as in a reaction with reagent A.
While reagent B showed no clear effect on the chemical reaction in the condensate samples from the inlet area, the peak area and the cooling area, this substance resulted in a reduction of the peaks in the spectrum. The analyses of the condensed reaction products on the aluminum foil confirmed this. The lowest condensed traces were present in all condensate samples. Substance B shows very good absorbing behavior. It can be used in addition to reagents A and C to absorb gaseous reaction products.
Reagent C showed an effective chemical change in condensate samples from the inlet and cooling areas. This was clearly visible in corresponding spectra. An exemplary reaction process from the family of reagent C - citric acid illustrated the mechanism of action.
Initially Published in the SMTA Proceedings
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