SMT007 Magazine

SMT-Apr2016

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44 SMT Magazine • April 2016 needs to be added this hourly rate is 42% for manufacturers with less than 500 employees [3] . This consists of both voluntary (medical, dental and life insurance, etc.) and involuntary (i.e., social security, unemployment insurance, etc.). This puts the loaded cost at $20/21 per hour. There are numerous indirect costs associ- ated with the cost of having a skilled soldering technician on hand including their ongoing training overhead. The technicians responsible for the rework process have a real cost of train- ing associated with their expertise, certification and ongoing training. Numerous costs are as- sociated with training. Included in this list are the fully loaded cost of the trainer spread over the number of associates being trained, the lost pay linked to the time when the soldering tech- nician was not providing manufacturing sup- port to output, the equipment used for training purposes, as well as any training space costs. By taking in to account a trainer's base salary, the number of employees that they support for training, how often the recertification training takes place, the training equipment and the floor space costs dedicated towards training, these indirect costs can be calculated. These in- direct costs for a $20–30M EMS company op- erating the Midwest in the neighborhood of $6.00 per hour [4] . Supervisory labor is also a part of the indi- rect portion of a rework technician's labor costs. Whether it be a dedicated supervisor responsi- ble only for the rework area, a floor supervisor who spends some of their time in the area or a process engineer supervising temporary help for a given rework job, supervision of rework personnel is part of the cost of rework. If tem- porary associates are brought in for large rework projects, the cost of their supervision needs to be considered. In this rework cost model it adds another 10% [5] to the cost of the rework techni- cians effective hourly wages. Rework yield and the associated cost of the circuit board assembly is a major cost driver as- sociated with the cost of reworking an assembly. Effectively, this means at very low board value that outsourcing makes less and less sense. Con- versely, for complicated repairs where the yield is going to be suspect, outsourcing becomes the better option assuming the board value is sev- eral hundred dollars or more. PCB rework stud- ies have placed the rework yield in the 92–96% range [6] . Since this is a manual process and is a function of the skill level of the operators, their training and experience this is to be expected given the much higher yields in the original as- sembly process area. In order to see how this cost model plays To ouTsourcE or noT To ouTsourcE Pcb rEWork Table 1: Effective U.S. rework technician cost, lower/mid-tier EMS provider [1] . Table 2: example removal and replacement cost, 0.5 mm QFP100.

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