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SMT electronics assembly manufacturing forum.

Types of OSP Coating

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Types of OSP Coating | 6 September, 2007

Hi! I am Syed from Hitachi located in Malaysia.It seems that the discussion about OSP is very much related to the dillema that I am facing in my company.I am the Senior Executive for the SMT Department at Hitachi.Currently we are facing some issues whereby we have some difficulty of solder to spread and form on the pattern.For your information we are using Paper Phenol double layer board. Base on the supplier feedback the OSP used is "CU Coat VII" made by SANWA Laboratory Ltd.The thickness control is 0.20um. My question is: 1] Is there such type of OSP in the market?(Cu Coat VII) 2] Is the thickness suitable?

Hope to get a favourable answer through this forum.

Thanks and Regards.

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Types of OSP Coating | 7 September, 2007

what type of solder paste are you using?

Why the concern over wetting spread to the edge of pads? Are the solderjoints formed correctly at the component?


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Types of OSP Coating | 8 September, 2007

We expect to see a copper shadow along the edge of pads when soldering boards with organic solderability protection [OSP]. IPC-A-610 has defined this as acceptable for years. During early reflow stages, the flux in paste dissolves the OSP where there is contact. Generally, the flux does not spread to allow solder to cover the entire pad. Of course you will not see this copper shadow if your paste deposit is 1:1 with pad.

The thickness of OSP should be whatever the OSP supplier says it should be. There isn't any one acceptable thickness, it really depends on the type of OSP being used and your assembly process and chemistries. If possible work with the board fabricator and their OSP supplier. They should be able to give you a guideline for determining thickness. We see thickness ranges from 1500 to 3500 Angstroms for one supplier and 3000 to 5500 for another supplier. Actually, thickness is not the issue. Too little creates more problems than too much. OSP is self-limiting.

More importantly, your board fabrictor should be capable of measuring OSP thickness in order to maintain proper control.

Predominant OSP compounds are: * Benzotriazole [ ]: Initially used in metal finishing and restoration industries. Adopted for limited heat cycle solder applications for electronics. * Substituted Benzimidazole [ ]: Developed to withstand multiple heat cycles and extend storage life. * Substituted imidazole

Shikoku Glicoat SMD process is the market share leader for OSP in Japan and the Asian Rim.

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Types of OSP Coating | 9 September, 2007

Dear Members, Sorry,I might have not made myself clear on this issue and creating some confusion.Actually the problem faced is during the DIP Soldering process whereby one of the connector(IDE Pin) solder is cracked and lifted from the pattern.Visually the formation of solder looks good,it is only the solder that does not joint to the pattern.

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