The goal of this exercise is to help you learn the superstructure for empirical research reports.

The Exercise

Complete the Revision Checklist for Empirical Research Reports as you examine the report below.

The Report

NORTHWEST ENGINEERING CONSULTANTS
Interoffice Memorandum

This report describes the results of my laboratory tests of five circuit-board cleaners that are potential alternatives to our present cleaner, CFC-113. You asked me to use these cleaners in one of our board-cleaning stations and to compare the effectiveness of each with CFC-113. These tests indicate that all cleaners performed satisfactorily; however, the alcohol mixture was best in meeting our time and cleanliness standards.

Method

At a circuit-board cleaning station, I used each of five cleaning fluids: (1) terpenes, (2) deionized water, (3) alcohol, (4) lemon juice, (5) HCFC-141b. I washed 20 circuit boards with each cleaning fluid using our standard spray settings (5 gpm, nozzle aperture at 3 mm). This test was performed in two steps:

First, I washed 50 boards (10 boards with each cleaner), varying the cleaning time (the period that the board was in the spray) from 5 seconds to 23 seconds. Starting at 5 seconds I increased each board's cleaning time by 2 seconds so that, when the tenth board was cleaned, the time was 23 seconds. Then, with a standard quality-assurance 10-power magnifying glass, I inspected each board for cleanliness. My criteria for this inspection was the same as we now use for determining circuit-board acceptability prior to shipping.

From this inspection I determined the minimum amount of time each fluid needed to be sprayed on a board for it to be cleaned to acceptable standards, referred to hereafter as the minimum acceptable wash time (MAWT).

Second, I washed 50 more boards (ten boards per cleaner) for the MAWT determined for each cleaner in the first part of my test. Then I inspected each of these boards to the previous criteria and recorded the number of boards that failed.

Results

The MAWT for each cleaner is shown in Table 1. (CFC-113 is also shown for comparison.):

Table 1—Minimum acceptable wash times for circuit-board cleaners

From the sample of ten circuit boards cleaned to MAWT by each cleaner, the number of boards that failed the post inspection is shown in Table 2. (CFC-113 is also shown for comparison.) Also shown are the number of criteria, out of the 20 criteria the inspection called for, on which each board failed:

Table 2—Number of boards that failed inspection after MAWT cleaning

Discussion

All of the cleaners that I tested appear to be able to meet our requirements for washing circuit boards and, therefore, could be satisfactory replacements for CFC-113. However, the alcohol mixture seemed to perform the best: it had a short MAWT and no failures in the tests. Moreover, alcohol was one of the easiest to handle; both terpenes and HCFC-141b have special handling requirements that make them somewhat more difficult to pour into the cleaning-station tanks.

Conclusions and recommendations

Alcohol performed the best and was among the easiest to handle. Therefore, from our perspective in the lab, it would be an excellent replacement for CFC-113.