What are the key points of lead-free solder paste printing technology? JJY tells you

Lead-free solder pasteWhat are the key points of printing technology? Solder paste is made by evenly blending small round balls of tin alloy with half the volume of organic auxiliary materials. However, due to the significant difference in specific gravity between the two, it is inevitable that separation and sedimentation will occur after being stored for too long. Moreover, when the storage temperature is relatively high, the separation phenomenon will deteriorate even more, and oxidation is also more likely to occur, which will have adverse effects on printability, rheology and even solderability later on. So it can only be placed in the refrigerator.5-7℃Refrigeration is carried out to ensure its purpose and lifespan. Now, let's have the editor explain what technical requirements there are?

Technical key points:

①. Before printing, the scraper, steel mesh and other tools must be inspected. Make sure it is clean, free of dust and debris (clean thoroughly if necessary) to prevent the solder paste from being contaminated and affecting its desoldering property. The blade of the scraper should be straight without any notches. The steel mesh should be straight without obvious deformation. There must be no residual tin paste hard lumps or other debris on the edge of the open slot.

②. The base plate should be fixed with fixtures or vacuum devices to prevent it from being printed during the processPCBOffset occurs and it can improve the separation effect of the steel mesh after printing.

③. Connect the steel mesh withPCBAdjust the positions between them to fit as well as possible (large gaps can lead to solder leakage, and horizontal misalignment can cause solder paste to be printed outside the solder pad). ;

④. The amount of solder paste added to the steel screen at the beginning of printing should be appropriate, generallyA5Specification steel mesh plus200gLeft and right,B5Specification steel mesh plus300gLeft and rightA4 Specification steel mesh plus400gLeft and right;

⑤. As the printing operation continues, the amount of solder paste on the steel screen will gradually decrease. At an appropriate time, an appropriate amount of fresh solder paste should be added.

All the soldered surfaces must be full, neat and beautiful when using lead-free solder paste, especially the surface gloss.

There are no omissions or unsoldered areas in the solder paste soldering temple. The solder paste did not cause problems such as false soldering, monument standing, continuous soldering or residue due to overheating or insufficient temperature.

The solder paste fully penetrates the bonding area. Are all the exposed parts of the circuit board covered with solder paste?

If there are any joints in the raw materials and solder paste soldering parts, they must not deteriorate or be damaged due to heating.

Lead-free solder pasteThe rosin in the medium must not disperse and invade the contact areas or the gaps that should be left.

Solder paste absorbs water easily.HygroscopicOnce moisture is absorbed, various properties will deteriorate significantly, inevitably causing a lot of trouble in subsequent operations (such as tin balls). Therefore, the relative humidity in the on-site printing environment must not exceed this limit50％The temperature range should be maintained at22-25℃And wind should be completely avoided to reduce the occurrence of drying out. Otherwise, the printing will be lost very easily This will cause the oxidation of the solder paste, which in turn will consume the energy of the flux in terms of rust removal function, resulting in insufficient rust removal ability of the foot surface and the pad surface that should be present. It may even lead to the collapse of the bridge, the flying of solder balls everywhere, and reduce the adhesion time.Tack TimeIt is also shortened for it.

For those who want to know about solder paste, solder paste, low-temperature solder paste, solder wire and solder bar, welcome to consult Shenzhen JJY Industrial Technology Co., LTD. Let's learn and grow together!