Lead free soldering with no clean solder pastes represent nowadays the most common process in electronic assembly.
A solder paste is usually considered as no-clean if it passes all IPC J-STD-004 corrosion tests: copper mirror, copper panel corrosion test, Surface Insulation Resistance (SIR) and Elecrochemical Migration (ECM).
Other SIR and ECM tests are described in Bellcore GR-78-CORE and JIS Z3197 standards.
Although SIR and ECM tests are recognized by all standards authorities to evaluate the solder paste residue corrosivity after reflow, a more selective method, the Bono test, has been developed and implemented in some French companies as a qualification criterion. It has been proven that compared to common corrosion tests, the Bono test better differentiates the nature of solder paste residues.
Although SIR and ECM tests are recognized by all standards authorities to evaluate the solder paste residue corrosivity after reflow, a more selective method, the Bono test, has been developed and implemented in some French companies as a qualification criterion. It has been proven that compared to common corrosion tests, the Bono test better differentiates the nature of solder paste residues.
Bono Test Description
This method is based on an existing test which assesses the liquid soldering flux residue corrosivity after wave soldering.
This method is based on an existing test which assesses the liquid soldering flux residue corrosivity after wave soldering.
The test board has been modified to measure the solder paste residue corrosivity from the one used in the SIR and ECM tests. It is composed of 10 electrolytic cells and is made of an FR4 epoxy substrate with a single copper layer, having a very thin anode between two cathodes.
The solder paste is printed on cathodes through a 120µm thickness stencil and reflowed according to the desired profile.
References
1. J. Guinet, X. Lambert and D. Bono, Soldering and Surface Mount Technology, No 16, February 1994
2. Inventec procedure, MO.SB.10029, January 2007
3. IPC-9201, Surface Insulation Resistance Handbook, 1996
4. L. Lach, R. Mellitz, F. Sledd, L. Turbini, J. Schodorf, Developing a Standard Test Method to Indentify Corrosive Soldering Fluxes Residues, International Conference on Solder Fluxes and Pastes 1992
5. IPC-TR-476A, Sixth Working Draft, April 1995
6. IPC J-STD-004B, 2008
7. Bellcore GR-78-Core, 1997
8. JIS Z 3197, 1986 and Z 3284, 1994
9. H. Daniel, M. Leturmy, S. Lazure, T. Vukelic, “Influence of N2 atmosphere on the contamination effects of lead-free solder paste during reflow soldering process”, APEX 2005
The solder paste is printed on cathodes through a 120µm thickness stencil and reflowed according to the desired profile.
References
1. J. Guinet, X. Lambert and D. Bono, Soldering and Surface Mount Technology, No 16, February 1994
2. Inventec procedure, MO.SB.10029, January 2007
3. IPC-9201, Surface Insulation Resistance Handbook, 1996
4. L. Lach, R. Mellitz, F. Sledd, L. Turbini, J. Schodorf, Developing a Standard Test Method to Indentify Corrosive Soldering Fluxes Residues, International Conference on Solder Fluxes and Pastes 1992
5. IPC-TR-476A, Sixth Working Draft, April 1995
6. IPC J-STD-004B, 2008
7. Bellcore GR-78-Core, 1997
8. JIS Z 3197, 1986 and Z 3284, 1994
9. H. Daniel, M. Leturmy, S. Lazure, T. Vukelic, “Influence of N2 atmosphere on the contamination effects of lead-free solder paste during reflow soldering process”, APEX 2005
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