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What is the impact of soldering precision on the board?

What is the impact of soldering precision on the board?

Accuracy is one of the main data indicators in the SMT machine specifications, and the accuracy used by different SMT machine manufacturers has different definitions. In general, the accuracy of the mounting should include three items:mounting accuracy, resolution, and repeatability. The high-precision SMT machine can mount multi-lead and fine-pitch components such as SOIC and QFP, and is suitable for circuit assembly in industrial electronics and military electronic equipment. The following are three characteristics of the SMT equipment.

(1) Mounting accuracy. The mounting accuracy indicates the mounting deviation of the component relative to the calibration position on the PCB, and is defined as the integrated position error of the component terminal offset from the calibration position maximum. There are two main factors that affect the mounting accuracy, namely translation error and rotation error.

 

The translation error (the deviation of the center of the component) is mainly due to the inaccuracy of the X-Y positioning system, which includes errors such as displacement, calibration, and axis orthogonality. The main cause of the rotation error is the inaccuracy of the component alignment mechanism and the rotational error of the mounting tool. Quantitatively speaking, the accuracy of mounting SMC is ±0.01mm, and the accuracy of mounting high-density, narrow-pitch SMD is at least ±0.06mm.

(2)Resolution describes the ability of the mounting machine to resolve spatially consecutive points. The resolution of the SMT machine is determined by the resolution of the rotary or linear position sensing device on the positioning drive motor and the shaft drive mechanism. When the coordinate axis is programmed to run to a specific point, it actually reaches the point that can be resolved closest to the target position, which causes the positioning error of the placement machine and the actual target to produce a quantization error, which should be smaller than that of the SMT machine resolution, up to 1/2 of the SMT machine resolution. Resolution can also be described simply as a measure of the minimum measurement of machine operation, which is an important performance indicator when measuring the accuracy of the machine itself.

 

(3) Repeatability. Repeatability describes the ability of the mounting tool to repeatedly return to the calibration point. When defining for repeatability, the concept of bidirectional repeatability is often used, generally defined as the deviation from the mean when approaching any given point from both directions in a series of tests.

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May-13-2019

FASTPCBA