Sandra A. (Giovannangelo) MacMillan, age 71, of Billerica, died Monday, April 3, 2017, lovingly surrounded by her sons and niece. She was the beloved wife of the late John A. MacMillan, Jr., to whom she was married 50 years. Sandra was born in Cambridge, August 6, 1945, the daughter of the late Antonio and Edna (Souza) Giovannangelo. She worked her entire career in the electronics and computer industries. She had many interests and friends that kept her busy in her free time, but nothing held her focus like family with her three granddaughters taking center stage in her thoughts. Sandra was loved by everyone who met her and will be missed by all. She is survived by her sons, Steven A. MacMillan and his wife, Angela, of Lowell, and Patrick F. MacMillan and Wayne J. MacMillan, both of Billerica; her daughter-in-law, Christine MacMillan of Billerica and her three loving grandchildren, Sara of Lowell, and Sarah and Rebecca, both of Billerica. She also leaves her niece, Donna Winitzer and her husband, Chuck, and their four children, all of Woburn. She was also the mother of the late John A. MacMillan, III.