Assembly inspection Process indicators

The Bonding Process. Before the actual assembly operation, the cleanliness of the shop and tools should be verified. The shop atmosphere should be controlled as closely as possible. Temperature in the range of 18 to 32°C and relative humidity from 20 to 65 percent are best for almost all bonding operations. All parts should be fitted together without adhesive or sealant to indicate possible production problems due to fit. The suitability of fit is established by either visual inspection or direct measurement with gauge or shim. It is desirable that the extremes in mechanical tolerances also be noted and that test specimens be made with the worst possible fit to ensure that the bonding process will always provide reliable joints. 

As Fig. 53.1 indicates, visual inspection can occur after each of the several printed circuit assembly process steps. Visual inspection often has different purposes, depending on where in the assembly process it occurs.These purposes fall into the following major categories ... 

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