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Analysis and Improvement of Explosive Plate in PCBA Reflow Welding

2019-09-20 11:36:39
With the development of electronic products in the direction of multi-function, high-density, miniaturization, three-dimensional, etc., a large number of micro-devices are being used more and more, which means that more and more device I/O per unit area, and heating elements will also More and more, the need for heat dissipation is becoming more and more important.

At the same time, the thermal stress warping caused by the different CTEs of many materials makes the risk of assembly failure more and more serious, and the probability of early failure of electronic products will increase. The bigger it is. Flash Gold manufacturer china.

Therefore, the soldering reliability of PCBA becomes more and more important. The following describes the shortage of the blasting plate in reflow soldering and its improvement method for your reference.

While the PCB is heated, part of the free volume of water can be dissipated through the microporous PCB substrate, thereby reducing the molar volume fraction of water that may accumulate at the voids or microcracks, which is beneficial to the explosion of the PCB. improve. However, if the surface of the PCB has a large area of copper foil pattern coverage, when the PCB is heated, the large copper foil surface above the buried hole blocks the water vapor that escapes outward after being heated, so that the pressure of water vapor in the microcrack increases, resulting in occurrence of The chance of a burst is greatly increased.Ceramic PCB manufacturer china.

Pre-explosion plate countermeasures

(1) The necessary conditions for eradicating the occurrence of a blasting plate
The biggest problem in PP storage is to prevent it from absorbing moisture, and the moisture in the air is easily condensed on the PP to become adsorbed water. In order to maintain the original performance of the PP, the suitable storage conditions are: temperature (10 ~ 20) °C, humidity < 50% RH (preferably stored in vacuum). It has been reported that storage of sheets at 5°C for one month or longer does not successfully produce high quality multilayer boards, so refrigeration is also undesirable. Multilayer pcb solution china.

Strictly control the storage conditions of PCB finished products, especially in rainy weather, increase the power of the dehumidifier to control the humidity of the warehouse; Improve the packaging of PCB products for lead-free process, use vacuum film + aluminum film packaging to ensure preservation Time and dryness; look for new materials with good heat resistance and low moisture absorption.

(2)Sufficient conditions for suppressing the occurrence of bursting; optimizing the quality of “browning” process, increasing the adhesion between layers in the PCB; selecting high-quality browning syrup; strengthening the monitoring of the quality of incoming raw materials, such as the resin content of PP material (RC%), Key indicators such as resin gel time (GT), resin fluidity (RF%), and volatile matter content (VC%).

In order to ensure the uniformity and occupancy of the resin present in the impregnated fiber space, it is ensured that the finally formed substrate material has low water absorption, better dielectric properties, good interlayer adhesion and dimensional stability.

(3) Gas permeability of the Shanshan copper foil surface According to the above-mentioned positional characteristics of the explosion plate and the mechanism of the occurrence of the explosion. Obviously, when the surface of the PCB has a large area of copper foil layer design, the internal water vapor will not be released, so it is necessary to open a window to the area with a large copper surface on the surface to improve the explosion phenomenon.

(4) Optimizing the peak temperature of reflow soldering To ensure good wetting, the peak temperature of reflow is appropriately reduced.