Quality Factors of Lead-Free Solder Sphere (Ball)

Lead-free solder spheres are predominantly used in applications that involve chip scale packages, flip chip wafer bumping and ball grid arrays like LBGA, CBGA and PBGA components. Products available out there in this category cover all kinds of alloy options including lead-free, eutectic, high-lead and low-silver content and even custom created options for different applications with specific requirements. However, with the current industry shift towards adopting lead-free solder paste and products, solder spheres of this specific type are the most in demand. Due to the tiny size of solder balls and the fact that a single device or circuit board can contain thousands of these spheres, you would definitely want to be sure of the product quality being offered to you. Let’s examine the quality factors of lead-free solder spheres that you should bear in mind when selecting the most suitable alternative for your PCB assembly.

Diameter and spheroid tolerance

Consistency in design is of paramount importance if you wish to enjoy predictable performance and usability from your lead-free solder spheres. It is important that the product you choose has uniform diameters as well as a tight diameter and spheroid tolerance. This factor becomes even more important when your desired solder ball size is smaller than average because in such cases, you will have to maintain an even tighter control over diameter and sphericity (measure of how round or spherical the ball is) tolerance.

Alloy smelting tech used for production

The process and technology used for smelting solder alloys is also an important factor to consider. Accurate metal proportions should be maintained in the lead-free solder spheres and proper process optimization should be maintained to avoid alloy segregation that will eventually lead to multiple peaks. Your manufacturer should also be able to guarantee consistency in production and repeatability of quality parameters from one batch to next. Any variations will severely hamper your own SMT assembly line.

Additional quality parameters

Alloy purity, dimensional consistency and resistance to oxidation are important quality parameters that you should consider when looking for the right lead-free solder sphere product. Low levels of oxides present in the solder balls ensure that reliable and strong solder bumps and joints are formed every time with a suitable flux and process profile. The weight of individual balls should also be consistent or else, it may end up misbalancing your BGA components entirely.

Product packaging related parameters

Lead-free solder spheres can oxidize - which is one of the biggest challenges faced by users of this product. Probing for spheres inside their container can also cause them to get contaminated with the impurities present in one’s hand or get scored or deformed by the impact of user’s fingers. All these issues however, can be avoided if the solder spheres you purchase come in smart packaging that ensures minimum exposure of the contents inside the jar and maximizes their shelf life.

Companies also offer lead-free solder spheres manufactured in accordance with custom alloy combinations, ball dimensions and micro-additive levels. If the product you are getting checks out on the above listed factors, you are making the right purchase choice.

Alpha Assembly Solutions Inc. is the global leader in the development, manufacturing and sales of innovative specialty materials used in a wide range of industry segments, including electronics assembly, power electronics, die attach, LED lighting.