A method of fabricating a microelectronic package can include mounting a microelectronic element to a substrate with a joining material. The mounting can include bonding a front surface of the microelectronic element to a first surface of the substrate with a joining material, and joining contacts arranged within a contact-bearing region of the front surface of the microelectronic element with corresponding substrate contacts at the substrate first surface, the joining creating electrical contact between the microelectronic element and the substrate. The method can also include forming an underfill between the substrate first surface and the contact-bearing region of the front surface of the microelectronic element, the underfill reinforcing the joints between the contacts and the substrate contacts, the joining material having a Young's modulus less than 75% of a Young's modulus of the underfill.