Boron's function in collagen production is primarily as a cofactor. It is necessary for proper utilization of the minerals calcium, magnesium, and phosphorous. Boron has been shown to increase bone growth and strength, and it contributes to cartilage maturation. Boron supplementation has also been shown to increase testosterone levels in postmenopausal women, which, in turn, improves collagen production.
References: Newnham, Rex E. "Essentiality of boron for healthy bones and joints."Environmental health perspectives 102, no. Suppl 7 (1994): 83.