Reasons for false welding of patch resistance

1. Incoming material inspection, that is, check whether the PAD is oxidized, whether there is oxidation at the welding end of 0603 resistance, or whether one end is oxidized and the other end is not oxidized; Has the relatively big influence to the stele;

2. Mesh 0.12, 1:1 is ok, check the impact of mesh tension on printing;

3. The mold formation after the solder paste printing, whether there is a collapsed edge, little tin, tin dirty, etc., has a greater impact on the steles and Bridges;

4. Check the patch, whether the CHIP after the patch is offset, and whether the solder paste is pressed on the green paint.

5. The design of resistance solder pad of PCB, whether the distance between the pads is too narrow or too wide, the solder paste amount of the solder pad and the size of both sides of the solder pad have a great impact on the steles.

6. The setting of furnace temperature curve, which should be adjusted according to the characteristics of flux and the capacity of the equipment, can try to improve the time and temperature of the insulation zone, so that the insulation zone and the reflux zone a good soft transition;

7. Direction of PCB into furnace.

If so, suggest to change solder paste.

Of course, standing should be caused by the size of the solder pad.

Also, can you specify your process conditions, such as the type of solder paste, temperature setting, whether there is nitrogen or not, the type of furnace, these related factors should be a unified reference to determine whether there is room for improvement under the existing conditions.

8 is the problem of incoming material pull, but with soldering iron can not necessarily see this element is oxidized, because if the material oxidation is not serious, in the high temperature of the soldering iron, it is easy to destroy that layer of oxide film, I suggest you put the element with a bit of tin paste, in the reflow, see whether the tin test.