Abstract: In this paper, a low cost non-destructive testing method for millimeter wave (MMW) ball grid array (BGA) package is proposed, which mainly consists of fuzz buttons and two single-layer substrates. In this structure, the fuzz button acts the vertical interconnecting medium between the solder ball and the substrate, and thus realizing signal transmission. Meanwhile,due to its small contact force, the fuzz button could protect the package ball during testing process. The dielectric filling coaxial structure, formed by the fuzz buttons and the substrate, and the high-low impedance lines on the substrate participate in impedance matching. By means of electromagnetic simulation software HFSS, a good transmission performance in MMW frequency band can be obtained. Finally, based on the framework discussed above, a sample socket is designed and fabricated for Ka band. The measurement shows that the port return loss is better than -14 dB in the operating frequency band of 21-33 GHz.