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1. From the perspective of smt processing and welding, the development of BGA packaging
From the perspective of smt welding, the mounting tolerance of BGA chips is 0.3mm, which is much lower than the previous QFP chip mounting accuracy requirement of 0.08mm. Generally speaking, SMT patch proofing and placement are done in a space of the size of a little finger or even smaller, then a larger placement tolerance means higher reliability and placement accuracy.
Then we assume that a large-scale integrated circuit has 400 I/O electrode pins, the same pin spacing is 1.27mm, and the traditional QFP chip has 4 sides, each side has 100 pins, then the final The side length is at least 127mm, so that the entire chip surface area should be 160 (square centimeters).
If we use the BGA package for processing, the electrode pins of the final SMT chip are evenly arranged under the chip in a 20*20 row, and the side length only needs to be 25.4mm at most, and the volume is less than 7 (square centimeters). .
From the above analysis, we can conclude two great improvements:
One: The number of chip soldering pins decreases
As the saying goes: "The more you do, the more mistakes you make." The opposite is that we reduce the number and procedures of welding as little as possible, so the probability of error will become less. Therefore, reducing the number of soldered pins is an important method that can improve the quality and reliability of welding. It can be said indirectly that BGA packaging has huge technical advantages and development potential compared to traditional QFP packaging.
2: Welding volume becomes smaller
From the brain interface of Tesla CEO Elon Musk to the skin display, what we see is not only technological progress, but also an application of highly intelligent and miniaturized products. There is a computer weighing a few kilograms in the sky, so the change of soldering volume also conforms to a future development trend, and it is also a huge late-comer advantage of BGA packaging.
Therefore, whether it is from the PCBA package of labor and materials or the future development trend, our development of BGA packaging must be bright.
Second, the main reason for the insufficient tin on the solder joints of smt patch processing
In smt patch processing, soldering is an important link, which is related to the performance and appearance of the circuit board. In actual production and processing, poor soldering may occur due to some reasons, such as common solder joints. Not full, will directly affect the quality of smt patch processing. So what is the reason why the tin is not full in the smt patch processing? The following introduces the product inspection requirements of Weilishi smt patch processing.
The main reasons for the insufficient tin on the solder joints of smt patch processing:
1. The wetting performance of the flux in the solder paste is not good, and it cannot meet the requirements of good tinning;
2. The activity of the flux in the solder paste is not enough to remove the oxides on the PCB pads or SMD soldering positions;
3. The flux expansion rate of the flux in the solder paste is too high, and voids are prone to appear;
4. The PCB pad or SMD soldering position has serious oxidation, which affects the tinning effect;
5. Insufficient amount of solder paste at the solder joints leads to insufficient soldering and vacancies;
6. If there is insufficient tin on some solder joints, the reason may be that the solder paste has not been fully stirred before use, and the flux and tin powder cannot be fully fused;
7. The preheating time is too long or the preheating temperature is too high during reflow soldering, which causes the flux activity in the solder paste to fail;
At present, most SMT chip processing manufacturers adopt advanced testing equipment to monitor the quality of the production process. During the reflow soldering process, AOI inspection equipment is generally used for quality control. Due to the high cost of automatic parameter adjustment and feedback in the quality control process, manual settings are required. Under this circumstance, it is even more necessary for electronic patch companies to formulate some practical and effective specifications and systems, strictly implement the established specifications, and achieve process stability through manual monitoring. In the formulation of quality control specifications for electronic patch prices, the response ability of operators and the control of equipment are very important.
