Northeast Lakeview College

1203C Lakeview Terrace, Montgomery, TX 77356. For correspondence, contact Brant Ulsh at [email protected].

The factors that best account for differences in strength across all types of exercise, body types, and training histories are not well understood. The purpose of this study was to assess the effects of strength level and body composition on upper- and lower-body work capacity in adult men. From a cohort of 295 adult men (25.6 ± 7.5 years, 178 ± 8 cm, 85.2 ± 15 kg), low-strength (LS, n = 72) and high-strength (HS, n = 66) samples were selected based on 1 repetition maximum (1RM) bench press (BP) and leg strength (LP) values. Work capacity for each exercise was determined from the product of repetition weight (80% 1RM) and maximum repetitions-to-fatigue (RTF). Body composition was measured using dual-energy x-ray absorptiometry. The HS group was significantly greater than the LS group in total body mass and fat-free mass but not in age, height, fat mass, or %fat. Low-strength and HS groups were not significantly different (p > 0.05) in RTF for either BP (8.7 ± 3.1 vs. 8.3 ± 1.9 reps, respectively) or LP (15.6 ± 7.6 vs. 17.0 ± 6.3 reps, respectively), making the ratio of RTF for BP vs. LP nonsignificant (LS = 2.0 ± 1.0; HS = 2.2 ± 0.9). The HS group produced significantly greater (p < 0.001) absolute and relative work capacities for both BP and LP compared with the LS group. Repetitions-to-fatigue had a greater influence on BP (r2 = 0.74) and LP (r2 = 0.85) work capacities in the LS group than did RepWt (r2 = 0.07 and 0.28, respectively). In the HS group, RTF (r2 = 0.79) had a greater influence than RepWt (r2 = 0.10) on BP work capacity, whereas the 2 components were more similar for LP work capacity (r2 = 0.64 and 0.47, respectively). When evaluated at the same %1RM, muscular endurance is similar across divergent strength levels meaning that work capacity (load × reps) will be greater for HS individuals. Controlling for the influence of body composition variables (e.g., fat or fat-free mass) does not eliminate the difference in work capacity between strength groups suggesting that other factors are accounting for strength expression. Prescribing repetitions against a fixed relative load is largely dependent on exercise type and must be considered by strength and conditioning professionals.

ABSTRACT Post reflow yield losses cost PCB assemblers tens of millions of dollars per year! Millimeter per millimeter, a populated post reflow finished PC board may represent the costliest square footage on earth. With bare boards costing upwards of thousands of dollars, a fully loaded PC board may have individual components equally as expensive. The manager(s) responsible for process yield have an urgent need to coordinate efforts to identify “marginal” processes, address root cause analysis and to implement process improvement initiatives to improve the bottom line. During assembly, placement of the IC package can lead to defects and yield loss. IPC 7095 highlights criteria for solder bump failure as a result of poor assembly and fabrication. Unfortunately most manufactures of flip chip do not take head to IPC 7095 during the assembly operation. The same spec used as an accept reject criteria for boards can also be used as a criteria for flip chip assembly. Here poor placement and alignment of electrical test probe needles cause the defects. The variation can come from a number of areas including the probe needle itself. The CSP assembly shop could suffer yield loss due to poor processes and not be aware that the root cause lies upstream. Unfortunately those marginal processes prevent optimum efficiency and the implementation of tools to improve manufacturing techniques and likewise reduce process variation. A process must be brought into control to implement techniques such as JIT, lean manufacturing, Kaizen, etc. Last, the repair, downtime and yield loss associated with poor quality not only burdens costing structures, but also impairs the ability to accurately forecast production builds, staffing and raw material needs. The raw materials populating boards is becoming an ever increasing mix of components that include small footprint devices with hidden solder joints (BGA, CSP, etc) and modular packages. Industry predictions for CSP-type packages are growth from 10% to over 60% in the next three to four years. These newer packages, more sensitive to placement errors (due to smaller geometry and hidden solder connections), require solutions that provide real-time process details as a mandate for improving PCB yield. Looking further upstream in the manufacturing process, part of the process variation can be isolated to electrical test and probe. It is well established that the planarity of the BUMP “plane” can jeopardize yield and reliability. Poor probe processes introduce variation in the final assembly stages that might be incorrectly assigned to that process station. This paper has been written to provide the audience with an overview of some root cause areas to investigate. Table 1 suggest possible dollar values that can be recovered as well as increased reliability suggest that upstream process control is critical to not only the CSP assembly in house, but the final product deliver to the customer as well.