Wave Soldering Solder Pull Tip is How to Form

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Wave soldering, sometimes found at the top of the components and pins or solder joints with icicle or stalactite-like solder, this phenomenon is called pull tip, as shown in Figure.

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Pull-tip occurs mainly at the end of the copper-clad circuit of a PCB. This can be caused if the liquid solder on the PCB is obstructed from falling when the PCB passes through a wave. In high-voltage and high-frequency circuits, this defect can be very harmful and requires special attention.
Causes of pull-tip formation
Poor solderability of the substrate, oxides or contaminants on the pads;
The quality, dosage or application method of the flux is not suitable to wet the surface of the solder joint and remove oxides;
The preheating temperature is too low or the preheating time is too short, making the component pins or printed boards absorb too much heat, affecting the fluidity and wettability of the solder;
Low solder purity and excessive impurity content;
Clamping speed is not suitable, the welding time is too short or too long;
Clamping tilt angle is not appropriate, the PCB out of the wave after the cooling wind angle can not be blown in the direction of the solder tank, in order to avoid rapid cooling of the solder, excess solder can not be gravity and cohesion pull back to the solder tank.
From the shape of the tip of the pull can be roughly judged from the temperature of the solder tank and the clamping speed is appropriate. If the tip of the pull has a metallic luster and a fine tip, it means that the temperature of the solder bath is low or the clamping speed is fast; if the tip of the pull is round, short, thick and no luster, it means that the reason is just the opposite.
Solutions
Cleaning the surface to be soldered, ensuring that the substrate surface is clean and free of oxides or contamination;
Adjusting and selecting the appropriate flux;
Setting the preheat temperature reasonably;
Adjusting the solder bath temperature, clamping speed and wave height;
The copper content in the solder bath should be controlled below 0.3%;
Separating large copper foil surfaces: If there are large copper foil surfaces, they can be separated into small pieces with solder resist film to improve soldering performance.
Fitech Flux
Shenzhen Fitech Co., Ltd. produces fluxes including rosin type and epoxy resin type, which are highly active and can effectively remove oxides and contaminants to improve soldering reliability. Welcome to call us for more information.