Solder Paste Jetting: An Integral Approach

Estimated reading time: 11 minutes

Figure 8: Layout GPE0435D with the smallest pitch of 0.8 mm. (Source: CyberOptics Corporation)

After the input of the CAD data and compilation of the jetting path using the compilation software, a plan is obtained. An example of a jetting path for the PCB used has been visualized using the software JPViewer and is shown in Figure 9.

The individual deposits that populate each pad are visible in Figure 10. The choice of deposit volumes to populate a given pad is provided by the job compiler to minimize jetting time for the entire PCB. For example, according to Figure 10, the pad coverage of 0603 component contains three dots, while y four 585-µm (33-nL) dots cover the pad 0805 components. It should be noted that each jetting segment is a straight line and reached via a travelling segment that is controlled by the mechanical machine specifications concerning speed and acceleration.

Production Results

The overall jetting results for the tested PCB were good, and generally, there were not any discontinuities concerning deposit volume or positioning that introduced production disturbances. An example of the overall results can be seen in Figure 10.

Jetting dot size and frequency for the GPE0435D layout is distributed according to Figure 11. There are distinct peaks in the size distribution that are tied to the provided pad sizes on the PCB. In Figure 11b, the distribution of jetting frequencies for the given PCB is shown. The most common jetting frequency is 300 Hz.

Jetting Results

The jetting results of the V49 ejector with the Senju LFAC19 paste were good relative to the provided volumetric and positioning guidelines. After a performance review, the customer had no major comments to improve. The smallest pitch for the chosen PCB was 0.8 mm, which means that the ejector does not utilize the entire volumetric span that is available. An example of jetting for the 0.8-mm pitch is provided in Figure 12 for component PQFP10X10-44 and the largest D-pack.

Figure 9: Jetting path for layout GPE0759A.

Figure 10: Jetting results on a GPE0759A layout. (Source: CyberOptics Corporation)

Figure 11: Histograms of (a) deposit size and (b) jetting frequency distribution for PCB GPE0435D.

Figure 12: Results after jetting with MY600 using V49 for (a) PQFP10X10-44 and (b) the largest D-pack.

The most common volumetric deposit is for the pads of the 0805 components. They show stable volume distribution results even if the expected volume defined by compiler were slightly higher than the actual volumes measured with the available SPI. The repeatability was approved according to customer requirements (Figure 13).

Figure 13: Pad coverage of component 0805.

For the larger pads of the 1206 components, the number of individual deposits can vary due to the compiler optimization discussed earlier, and the variation of volumetric pad coverage is slightly larger. This might be the result of a mixed jetting strategy for that particular component. Jetting results for the 1206 pads for different jetting strategies can be seen in Figure 14.

Figure 14: Different jetting strategies for the 1206 component.

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