It is recommended to switch to the use of Sn62 solder paste as a solution to the problem of high surface tension when melting Sn63/Pb37, because this material is an obstacle to high-quality solder joints of J-lead components. Also, since an inert (using nitrogen) environment tends to increase surface tension, open-type defects caused by edge coplanarity of J-shaped leads can be prevented by Sn62 solder paste in an air environment. If the assembly is dominated by finned lead components and solder bridging is an issue, then hopefully a little more surface tension, Sn63 solder paste retention and non-oxidizing atmosphere will allow the molten tin to be “pulled” back onto the leads.

Dubang introduces a new, gentle hydrofluorocarbon (HFC, hydrofluorocarbon) flux removal medium for removing residual rosin and residues left by newer low solids (no-clean) fluxes and solder pastes. Ionic contamination. Solvent composed of HFC43-10, trans 1, 2-dichloroethylene, cyclopentane, methanol and stabilizer, conformal coating with many plastics Both layer and component marking inks are compatible.

It is said that the addition of this very gentle carbohydrate reduces the concentration of those more aggressive residues, and at the same time has zero ozone depletion, low global warning and low toxicity characteristics, and is non-flammable. Developed a no-clean solder paste using organo-metallic chelation chemicals and dendrimer polymer as a catalyst. The compound is said to be a drop-in material that offers good chemical, physical and metallurgical properties for extending solder paste tack life and improving printing characteristics. The solder paste, called NC-559, consists of two parts: a synthetic rosin and a catalyst system. The use of catalysts in solvents has been discontinued because their higher polarity attracts the polymer network, which together with the consumed polymer prevents the formation of azeotropes during reflow soldering. The volatile portion is carried away with a portion of the catalyst system that is consumed. Post-reflow residues, compared to traditional no-clean solder pastes, are non-corrosive, non-conductive and non-hygroscopic. The result is a hard, clean, non-sticky and chemically benign surface, rather than those ionic or polar species that can cause ionic contamination in post-reflow residues. In the days of just-in-time (JIT, just-in-warehousing time e) manufacturing, for good solderability control, the inventory of empty boards may be a little larger than actual, although cost considerations require large-volume purchases.

To prevent the tendency of boards stored in warehouses to accumulate oxidation on pads, assembly manufacturers are forced to assemble and solder circuit boards in a reasonable amount of time, a step that depends on good business conditions. Therefore, it is important that SMT assembly line process engineers work with purchasing and management personnel to determine the safe storage life of empty boards. Solderability testing can determine what this deadline is in order to ensure a high-yield assembly. The most important part of manufacturing – avoiding contamination of the board before soldering.

For the final placement of fine-pitch components, carrying solid solder deposits (SSD, solid solder deposit) on empty boards is a new method to achieve 6σ and defect-free processes. This technique uses a dry-film solder mask material to provide openings of the correct length, width and spacing on component pads to receive solder paste. After reflow, the board is cleaned and the deposits are flattened into tin “bricks” so the pins can sit without slipping (Figure 1). A rosin-based, viscous glue-like flux is printed on the pads through a silk-screen process, and the board is sent to the assembler for component placement.

On the other hand, if covered with mylar, the board can be stored for up to a year and still maintain good solderability. How does lead-free solder ensure solder joint quality? Alternative alloys were evaluated by comparing the lead-free solder reflow performance of nickel/palladium and nickel/palladium/gold to those of traditional Sn/Pb materials. Tests include contact angle, pin pull, temperature cycling, cross-section (vs. fracture) and wetting balance. Although only a slight improvement in wetting balance was found (and the added cost of the gold layer), overall the alternative alloys equaled or exceeded the performance of Sn/Pb solders in terms of solder joint formation quality

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