1. Correct Components
It is required that the characteristic marks such as type, model, nominal value and polarity of each assembly tag component must meet the requirements of the product assembly drawing and schedule, and cannot be pasted in the wrong place.
Charmhigh P&P Machine
2. Accurate Location
The terminals or pins of the components should be aligned and centered with the pad pattern as much as possible, and it is also necessary to ensure that the soldering end of the component contacts the solder paste pattern. The mounting position of components must meet the process requirements. The mounting position requirements for Chip components at both ends, wing-shaped pins and J-shaped pins devices, and ball-shaped pins devices are as follows:
①Chip components with two ends: the self-positioning effect of the Chip components at two ends is relatively large. When mounting, more than 1/2 of the component width is overlapped on the pad, and the two ends in the length direction only need to Lap to the corresponding pad and contact the solder paste pattern, it can be self-positioned during reflow, but if one of the terminals is not lapped to the pad or does not contact the solder paste pattern, it will shift during reflow or drawbridge.
②wing-shaped pins and J-shaped pins devices,For SOP, SOJ, QFP, PLCC and other devices, the self-positioning effect is relatively small,Mounting offset cannot be corrected by reflow soldering.
If the mounting position exceeds the allowable deviation range,It must be manually corrected before entering the reflow oven for welding.Otherwise, it must be repaired after reflow soldering,
It will cause waste of man-hours and materials, and even affect product reliability.When the mounting position is found to exceed the allowable deviation range during the production process, the mounting coordinates should be corrected in time.
Manual mounting or manual timing requires that the mounting position is accurate, the pins are aligned with the pad, and centered. Do not place it incorrectly. Drag it on the solder paste to find the alignment, so as to avoid sticking of the solder paste pattern and cause bridging.
③Ball Pin Devices:Since the pad area of BGA, CSP and other spherical pin devices is relatively large relative to the area of the component body,The self-positioning effect is very good, so as long as these two points are met,One is that the solder balls of the BGA correspond to the corresponding pads one by one;Second, the maximum offset between the center of the solder ball and the center of the pad is less than 1/2 of the diameter of the solder ball.
3. The pressure (pick and place height) is appropriate.
The pick and place pressure (Z-axis height) should be appropriate.The patch pressure is too small,component solder ends or pins float on the surface of the solder paste, and the solder paste cannot stick to the components., easy to produce position shift during transfer and reflow soldering,In addition, because the height of the Z axis is too high,When the component is dropped from a high place during the mounting, it will cause the position of the mounting to shift;
If the chip pressure is too high and the amount of solder paste is extruded too much, it is easy to cause solder paste sticking, Bridging is easy to occur during reflow soldering. At the same time, the position of the chip will be shifted due to sliding, and components will be damaged in severe cases.
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