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PCB HASL What are the advantages and disadvantages?

2020/01/09 16:50
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PCB HASL What are the advantages and disadvantages?
HASL is a common type of PCB board, usually high-precision multi-layer PCB, widely used in various types of electronic equipment, communication products, computers, medical equipment, aerospace and other fields and products.
PCB HASL What are the advantages and disadvantages?
Spraying tin is a step and process flow of the PCB board in the production process. Specifically, the PCB board is immersed in the molten solder pool, so that all exposed copper surfaces will be covered by solder, and then the hot air cutter will removal of excess solder on the PCB. Because the surface of the printed circuit board and the solder paste are similar substances after soldering, the soldering strength and reliability are better. However, due to their processing characteristics, the surface flatness is not good HASL process, particularly for packages such as BGA type small electronic components, due to the small welding area, if the flatness is poor it may cause problems such as a short circuit, it is necessary to smooth of better technology to solve this problem HASL. Of gold will generally choose process (note not gold plating), using a chemical displacement reaction principle and method for re-processing, increasing the thickness of the nickel layer is about 0.03 ~ 0.05um or 6um improve the surface flatness.
1, components better wetting of the welding process, the solder easier.
2, the exposed copper surface to avoid corrosion or oxidation.
Not suitable for fine pitch solder pins and the components too small, because of the poor surface smoothness of HASL. PCB manufacturers in processing easily solder balling (solderbead), the fine gap of the pin (FinePitch) Component easily cause a short circuit. When using double sided SMT process, since the second surface has passed a reflow temperature, discharge occurs very easily re-melted tin solder balls or the like to produce drops by gravity into a spherical solder joint dropped, resulting in less surface thereby affecting the level of welding problems.
As technology advances, the industry has now emerged proofing PCB QFP and BGA assembly process is suitable HAL pitch smaller, but less practical. Some currently employed OSP PCB proofing processes and leaching technology to replace the HASL process; also makes a number of technological developments in factories using immersion tin, immersion silver technology, coupled with the trend in recent years, lead-free, tin spray process using subjected to further limit.