The latest articles on DEV Community by JINNHOO Semiconductor (@jinnhoo_semiconductor). https://dev.to/jinnhoo_semiconductor https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4129362%2Ff765d54a-5d7f-4786-b94d-c2df9d308ffc.png https://dev.to/jinnhoo_semiconductor en JINNHOO Semiconductor Thu, 17 Sep 2026 07:55:17 +0000 https://dev.to/jinnhoo_semiconductor/the-role-of-sac305-solder-balls-in-bga-reflow-5dk6 https://dev.to/jinnhoo_semiconductor/the-role-of-sac305-solder-balls-in-bga-reflow-5dk6 <p><a href="https://jinnhoosemi.com/solder-ball.html" rel="noopener noreferrer">SAC305 solder balls</a> are widely used in lead-free BGA packaging. During assembly, the solder balls are placed between the package substrate and the corresponding PCB pads, and the reflow process transforms these individual balls into solder joints.</p> <p>Understanding what happens during reflow helps explain why solder ball specifications and assembly conditions need to work together.</p> <h2> What Happens During Reflow? </h2> <p>Before reflow, the solder balls remain solid and maintain their original spherical shape. Once the assembly enters the appropriate temperature range, the solder alloy begins to melt.</p> <p>The molten solder wets the corresponding pad surfaces and forms the connection between the package and PCB. After cooling, the solder solidifies and creates the final solder joint.</p> <p>The final joint shape is therefore influenced not only by the solder ball itself, but also by the pad design, surface finish, flux, temperature profile, and other assembly conditions.</p> <h2> Why SAC305 Is Commonly Used </h2> <p><a href="https://jinnhoosemi.com/solder-ball.html" rel="noopener noreferrer">SAC305 </a>is a lead-free tin-silver-copper alloy containing approximately 96.5% tin, 3.0% silver, and 0.5% copper.</p> <p>Its established use in lead-free electronic assembly makes it a common choice for applications such as BGA and CSP packages.</p> <p>However, SAC305 is not automatically suitable for every package. The required ball diameter, tolerance, package pitch, and assembly process still need to be considered.</p> <h2> The Importance of Consistent Solder Balls </h2> <p>A BGA package may contain hundreds or even thousands of solder ball connections. Consistency between individual balls is therefore important.</p> <p>Variation in ball diameter can influence the amount of solder available at each connection. Surface condition and cleanliness can also affect wetting during reflow.</p> <p>For this reason, solder ball manufacturing typically involves dimensional inspection and quality control before the balls are packaged for assembly.</p> <h2> Reflow Is Part of the Complete Process </h2> <p>A solder ball cannot be evaluated independently from the assembly process.</p> <p>For example, even when the solder alloy and ball diameter are correctly specified, an unsuitable reflow profile or poor pad surface condition can still affect the final solder joint.</p> <p>A reliable BGA interconnection therefore depends on the combination of solder ball characteristics, package design, PCB design, materials, and process parameters.</p> <p>For engineers working with BGA packaging, understanding this relationship can make solder ball selection more practical and help identify potential assembly issues before mass production.</p> solderball soldersphere bga advancedpackaging