PH NEUTRAL CLEANING AGENTS: TECHNOLOGY AND PERFORMANCE

摘要

Effective cleaning is greatly challenged by component miniaturization, larger component packages, higher lead counts, reduced conductor spacing, tighter pitch and lower standoffs. Added to these geometry challenges, the greater use of lead-free solder paste and the increasing trend of multiple thermal cycles results in difficult to remove burnt-in flux residues. However, these challenges are overcome with the use of engineered aqueous-based cleaning agents. Modern cleaning agents can be alkaline or pH neutral depending on the degree of solvency required. Each are environmentally friendly as they are biodegradable and HAP free. However, in addition to excellent material compatibility and ease of handling, pH neutral formulations have the added advantage of potentially eliminating the need for waste water neutralization. Effective cleaning processes require an optimized balance of mechanical, thermal and chemical energy. Cleaning agents provide the chemical energy. As electronic assemblies are completely washed with the cleaning agent, these are formulated with inhibition packages as this is required in order to ensure effective material compatibility with the substrate and component materials. To maintain and ensure a stable pH throughout the life of a wash, pH neutral formulations contain an adequate buffering package in order to maintain a stable pH level as flux residues accumulate with the wash solution.