A camera module includes an image sensor, a number of metal balls, and a cover glass. The image sensor includes an active surface and a number of pads. The active surface includes an imaging zone and a non-imaging zone surrounding the imaging zone. The imaging zone is configured to sense incident light and to convert the incident light into corresponding electric signals. The pads are formed on the non-imaging zone. The metal balls are stacked on three of the pads, which are not linear. The numbers of the metal balls on each of the three pads are equal to each other such that heights of the metal balls on each of the three pads are substantially equal to each other. The cover glass is positioned on the metal balls.