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Organic Solderability Preservative (OSP)

by: Sep 28,2018 2152 Views 0 Comments Posted in PCB Manufacturing Information

Organic Solderability Preservative (OSP) SMT

—A Method of Surface Finish Technologies

Background:

In recent years, electronic products are developing towards light, thin, short, miniaturized and multi-functional. At the same time, PCB is also developing towards high precision, high speed, high density and so on. In particular, the rapid development of SMT makes the hot air leveling process increasingly unsuited to the requirements of PCB manufacturing process. Meanwhile, the welding material, such as Sn-Pb, used in the hot air leveling process also fails to meet the environmental protection requirements. With the official implementation of the European ively bonds to copper and protects the copper until soldering. In simple terms, OSP is a chemical process to grow a layer of organic coating on the clean bare copper surface, which has anti-oxidation, heat shock and moisture resistance, to protect the copper surface from rust (oxidation or vulcanization, etc.) in normal environment. However, at subsequent welding temperatures, the protective film must be easily removed by the flux, so that the exposed clean copper surface can be immediately combined with the molten solder to form a solid solder spot in a very short time.

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Brief Introduction:

OSP is a process for surface treatment of printed circuit board (PCB) copper foil in accordance with RoHS instructions, which uses a water-based organic compound that rust (oxidation or vulcanization, etc.) in normal environment. However, at subsequent welding temperatures, the protective film must be easily removed by the flux, so that the exposed clean copper surface can be immediately combined with the molten solder to form a solid solder spot in a very short time.


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Main Materials of OSP:

1.    Rosin

2.    Active resin

3.    Azole

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Technological Process:

The brief process of OSP is as follows:

(If you want to know more about the manufacturing process, please click here: PCBWay YouTube Official Account)

Oil Removal →Second-level Washing → Micro-corrosionSecond-level Washing → Acid Washing → DI Washing → Film Formation → DI Washing → Dry

1.    Oil Removal:

The effect of oil removal directly affects the quality of film formation. Poor oil removal, resulting in uneven film thickness. On the one hand, the concentration can be controlled within the process range by analyzing the solution. On the other hand, always check the oil removal effect is good, if the oil removal effect is not good, it should be replaced in time.

2.    Micro-corrosion:

The purpose of Micro-corrosion is to form a crude copper surface which is easy to do the film formation. The thickness of the micro-corrosion directly affect the film-forming rate, therefore, to form a stable film thickness, it is very important to maintain the stability of micro-corrosion thickness. The general micro-corrosion thickness shall be controlled at 1.0um to 1.5um which is more appropriate, so that before each production, the micro-corrosion rate can be measured and the micro-corrosion time can be determined according to the micro-corrosion rate.

3.    Film Formation:

It would be better to use the DI washing both before and after the film formation and the PH should be limited to between 4.0 and 7.0 to prevent contamination of the film forming solution. The key of OSP process is to control the thickness of anti-oxidation film which can easily affect welding performance. Generally, the film thickness is appropriate between 0.2-0.5um. For example, the thinner the film is, the poorer thermal shock capacity will be.

Disadvantages of OSP:

OSP certainly has its shortcomings, such as the variety of actual recipes and performance. What’s more, the protective film is extremely thin and prone to scratches (or bruises) and must be carefully manipulated and transported. At the same time, OSP film (OSP film on the unwelded plate) will change color or crack, which will affect weldability and reliability. That is to say, the certification and  different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers in China, PCBWay prides in being your best business partners as well as good friends in the every aspect of your PCB needs.

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Therefore, if you are worrying about choosing a manufacturer in China, PCBWay will be the best choice for you.

Why PCBWay?

Because with more than a decade in the field of PCB prototype and fabrication, PCBWay is committed to meeting the needs of customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers in China, PCBWay prides in being your best business partners as well as good friends in the every aspect of your PCB needs.




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