Influence of halogen-free process in smt patch processing
In the electronics industry, many customers in smt chip processing will inquire whether to provide halogen-free technology.
A brief introduction to the halogen-free process is that the finished pcba does not contain any element of 7 in the periodic table. You can search for the specific 7 contained in it!
Elimination of halogen solder paste and flux will have a greater potential impact on the chip soldering process. The purpose of adding halogen to solder paste and flux is to provide stronger deoxidation ability, enhance wettability, and thus improve soldering effect. In combination with the current development of the enterprise industry in my country, it is in the middle of the lead-free transition of SMT patches, that is, we need to use different alloys with weak wettability (lead-free) and the original alloys containing lead solder.
In solder paste, the removal of halogens may negatively affect wettability and soldering. This will be a significant change in application, requiring a longer temperature curve or a very small area of solder paste deposition.
For example, 01005 welding requires a larger flux dose, and the absence of other halogen composite materials will more easily lead to “grape ball” defects. The second defect that can become very common during non-conversion is the “Head In Pillow” defect. This defect problem occurs due to the ability of BGA devices or PCB boards to deform easily during the reflow development process.
Since the BGA or substrate will separate the solder balls from the deposited solder paste when the BGA or substrate is bent, during the reflow stage, the solder paste and the solder balls melt, but do not contact each other, and an oxide layer is formed on the respective surfaces, so that they will re-open during the cooling process. When in contact, they are unlikely to bond together, causing the weld opening to look like a “pillow”.
Because of the defects of the “grape ball” and “pillow” solder joints, the challenge for solder paste manufacturers is how to make the performance of the solderless paste as good as the company’s current solder paste. Improving the performance of reflow is not so simple. Because the catalyst has been improved, it may have a negative impact on the solder paste printing process, template life and storage time. Therefore, when evaluating non-material, the reflow performance and printing performance must be carefully tested. effect.
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