【 JJY 】 How to identify SMT surface mount Solder paste?

inSMTApplied in surface mount technology (SMT) production and processingSolder pasteIt should be uniform, with good consistency, clear graphics, and adjacent graphics should not stick together as much as possible. Graphics andpadThe graphics should be as good as possible; The amount of solder paste per unit area on the solder pad is approximately8mg/Cubic millimeters, approximately at fine intervals0.5mg/Cubic millimeters. The solder paste should cover the total area of the solder pad75%Above. The solder paste should be printed without collapse, with neat edges and no excessive displacement0.2mm; The fine displacement of the spacers in the protective layer of prefabricated components shall not exceed0.1mm; The substrate must not be contaminated by solder paste. theSMTHow to identify surface mount solder paste? Now, JJY solder Paste Manufacturer will explain it to you:

InfluenceSMTThe factors influencing the quality of solder paste printing in surface mount technology (SMT) processing include: viscosity, printability (rolling, transfer), thixotropy, and room temperature service life, etc. If the printing performance of the solder paste is poor, in severe cases, the solder paste only slides on the template. In such a situation, it is impossible to print solder paste at all.

SMTThe viscosity of the solder paste for surface mount processing is one of the important factors affecting the printing performance. The viscosity is too high, the solder paste is not easy to pass through the opening of the template, and the printed lines are incomplete. The viscosity is too low, making it prone to flow and chipping, which affects the printing resolution and the smoothness of the lines. The viscosity of solder paste can be measured by a viscometer, but in practical work, the following method can be adopted: Stir the solder paste with a spatula1-3After minutes, stir a small amount of solder paste with a spatula and let it fall naturally. If the solder paste decreases slowly in sections, the viscosity will be moderate. If the solder paste does not slide at all, the viscosity is too high. If the solder paste slides down at a faster speed, it means that the solder paste is too thin and has too low viscosity.

SMTThe viscosity of the solder paste for surface mount processing is insufficient, so the solder paste will not roll on the template during printing. The direct consequence is that the solder paste cannot fully fill the openings of the template, resulting in insufficient solder paste deposition. If the viscosity of the solder paste is too high, it will stick to the wall of the template hole and cannot be completely printed on the pad. The selection of the adhesive for solder paste usually requires that its self-bonding ability be greater than its bonding ability with the template, while its bonding ability with the template hole wall is less than its bonding ability with the pad.

SMTThe shape, diameter and uniformity of solder particles in surface mount processing solder paste also affect its printing performance. Generally, the diameter of the solder particles is approximately of the opening size of the template1/5. For the spacing is0.5The size of the pad in millimeters and the opening of the template is0.25The maximum diameter of the solder particles shall not exceed millimeters0.05millimeter. Otherwise, blockage is likely to occur during the printing process. Generally speaking, fine-grained solder paste offers better print clarity, but it is prone to edge sagging and has a high chance of oxidation. Generally, considering performance and price, pin pitch is regarded as one of the important selection factors.

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