Alignment and bonding techniques

Details Alignment and bonding techniques Alignment and bonding techniques

1996-03-15

1997-12-23

Walberg, Teresa J.

Electric heating

Metal heating

Wire, rod, or bar bonding

219 5622, 219 8518, 219209, 22818021, 361760, 361779, B23K 100, B23K 3053

Patent

active

057009872

ABSTRACT:
A method for aligning and soldering a first device (11) to a substrate (16) comprises the steps of providing a plurality of solder elements (17) between the first device and the substrate, aligning the first device, and then reflowing and cooling the solder elements to bond the first device to the substrate. The improvement comprises, first, reflowing only a first group of solder elements and then cooling the elements of the first group, thereby to tack the first device to the substrate. Thereafter, we reflow only a second group of the plurality of solder elements and cool the second group, thereby to provide a more secure bond between the device and the substrate without interfering with the alignment of the first device. This method reduces the amount of energy needed for each fellow step, thereby reducing stresses and maintaining better alignment. In an illustrative embodiment, three groups of solder elements are provided, each group containing four solder elements to be heated by individual heater elements (39). Separate circuits (27, 28, 29) are provided for energizing sequentially the three groups for reflow. Thus, four solder elements are initially reflowed and cooled to provide good tacking between the first device and the substrate. Thereafter, the other groups are actuated sequentially with heat dissipation occurring between each successive actuation. Thermal barriers (34, 38) are preferably included between each heater element and the first device and between the heater element and the substrate to concentrate heat on the solder element (17). The first device is illustratively a laser (11) that is aligned with an optical fiber (12) prior to bonding.

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