The density of solder paste is critical in the manufacturing of a good soldered joint. It is used to hold components in place after placement, and it can also facilitate the formation of a joint. If the paste is dispensed incorrectly, it can result in short circuits or poor electrical connections.
There are two main types of solder paste, Type 3 and Type 4. Both are used on surface mount components that have lead pitches of 25 mils or less. However, the pastes are not suitable for repeatable fine pitch components, as the largest particle size reaches 1.7 mils.
For these purposes, a more efficient way of applying solder paste to small components is to use Type 4 (T4). This type of paste improves the thixotropic properties of the paste. Compared with the T3 powder, it is slightly thinner and provides a modest increase in volume consistency.
Although the rheological properties of solder paste are vital, the performance of the process is affected by many other factors. These include the stencil design and thickness, the cleanability, and the presence of flux residue.
In addition to the standard powder sizes of 1.0, 1.8, and 2.5 mils, there are also smaller sizes. For example, Type 5 paste is available in particles that range from 10-25um.
Some studies have looked at the effect of mesh size on the printing performance of solder paste. While the impact was modest, it is important to understand that this factor could have an adverse effect on pause to print TE.
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