Product and Geographic Information Net sales by market (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Mar. 31, 2018	Apr. 01, 2017	Apr. 02, 2016
Revenue from External Customer [Line Items]
Revenue, Net	$ 113,393	$ 110,840	$ 70,967	$ 72,684	$ 49,918	$ 33,779	$ 29,658	$ 47,668	$ 367,884	$ 161,023	$ 184,391
Printed Circuit Board [Member]
Revenue from External Customer [Line Items]
Revenue, Net									256,430	88,771	94,121
Component Test [Member]
Revenue from External Customer [Line Items]
Revenue, Net									32,790	22,381	19,901
Semiconductor [Member]
Revenue from External Customer [Line Items]
Revenue, Net									55,171	29,557	38,262
Industrial Machining [Member]
Revenue from External Customer [Line Items]
Revenue, Net									$ 23,493	$ 20,314	$ 32,107