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[讨论]请教OSP板和化银板的区别 [复制链接]

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离线jaisonliu

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只看楼主倒序阅读使用道具楼主发表于: 2014-06-05

请教OSP板和化银板的区别

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离线fufred5917

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只看该作者沙发发表于: 2014-06-05

OSP

•OSP is Organic Solder Preservative and designed to produce a thin, uniform, protective layer on the copper surface of the PCB's. •It is gaining popularity with the search for lead free techniques and fine pitch solutions.
•For PCB manufacturers it's very simple and easy to control. •For PCB assembly, it has superior capabilities over traditional HASL with regard to coplanarity.
•Careful handling is needed as acidic fingerprints degrade the OSP and leave the copper susceptible to oxidisation. •It causes major problems at ICT with the bed of nails fixture contact. More aggressive probing is required to break through the OSP layer .

离线fufred5917

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只看该作者藤椅发表于: 2014-06-05

Immersion Ag

•During the soldering process the silver layer gets dissolved into the solder joint leaving a tin/lead/silver alloy on the copper which provides very reliable solder joints for BGA packages. •It's also a drop in replacement for HASL for soldering operations.
•There is although an underlying question mark over silver 'migration', but newer finishes have anti-migration agents added to minimise the effect. •There are no suggestions that there will be any negative effects seen at in circuit test stage.
•Immersion silver is a relatively recent addition to the PCB finish.

离线fufred5917

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只看该作者板凳发表于: 2014-06-05

OSP Pros and Cons

Pro's: • For PCB manufacturers it's very simple and easy to control.
•Comparable per unit cost to HASL, excellent coplanarity •Lead free process, improved solderability, no 'black pad' issues.
•Fine pitches(<0.5mm) Con's:
•Significant changes needed to assembly process with the type of flux and number of heat cycles. •Not ICT friendly, aggressive ICT fixture probes can potentially damage the PCB
•Manual handling precautions needed •Shortage shelf life