P2 Tech No-Clean
Technology Review

Released October 1996

View a summary of the no-clean cleaning technology review findings.


No-clean approaches can be defined as any approach to a process that allows a previously required cleaning step to be eliminated. When applicable, no-clean strategies are usually the best possible alternative to a current cleaning process. All of the costs and wastes associated with cleaning are completely eliminated.

The PPRC’s investigation found that published literature about no-clean approaches focused on one specific application: no-clean applications for soldering in electronics assembly. Two different types of approaches have been used to eliminate the cleaning step required after traditional soldering: using no-clean fluxes and, very recently, using fluxless soldering. This article will focus on no-clean fluxes and will briefly introduce fluxless soldering.

Flux Basics
Fluxes are used in electronics manufacturing to promote the wetability required to make a good solder joint. Specifically, soldering flux performs the following functions:

Two types of soldering are most commonly encountered in high-volume electronics assembly processes, and each type uses a different form of flux.

In addition to coming in a liquid or paste form, fluxes come in three primary types of formulations, each of which has different requirements for post-solder cleaning.

A number of industry-standard tests are used to evaluate fluxes and their residues. The tests are used individually or in combination in a number of the evaluations of no-clean fluxes reported on in the literature. Therefore, it is important to be at least introduced to these test methods. These tests are used collectively to categorize fluxes in one of three categories — low, moderate or high activity. In general, the higher the activity of a flux, the more reactive/corrosive the flux and its residue is. The tests are:

No-clean fluxes are mostly low-activity and sometimes medium-activity. Fluxes that require cleaning are typically medium- or high-activity. Additional background information on soldering and fluxes is readily available. (Ref. 1) Additional background information on no-clean soldering can also be found in a number of sources. (Ref. 1-4)

dot Technical Issues and No-Clean Approaches
A discussion of the technical feasibility of no-clean approaches and results that indicate visible residues are not necessarily detrimental. Further information that using a no-clean flux does not necessarily eliminate all cleaning in the solder area, and that use of an alternative atmosphere, such as nitrogen, can improve the no-clean process. Lastly, those considering a change to no-clean will require specific testing.

dot No-Clean Economics
A summary of research that evaluates the conversion to and operational costs of no-clean approaches.

dot Gaps in Existing No-Clean Research
An analysis of areas that merit further study.

dot Summary of No-Clean Technology Review Findings

dot Cleaning-related Projects in the Pollution Prevention Research Projects Database

dot Other Cleaning-related Internet Sites

dot No-Clean Bibliography

If you have topical suggestions for future P2 Technology Reviews, please send an e-mail message to Chris Wiley at cwiley@pprc.org. We also invite your general comments and feedback on the P2 Technology Reviews.

© 1999, Pacific Northwest Pollution Prevention Resource Center
phone: 206-352-2050, e-mail: office@pprc.org, web: www.pprc.org