(2000), "Enhanced under-board heater from Metcal reduces the risk of board and component damage during BGA rework", Soldering & Surface Mount Technology, Vol. 12 No. 2. https://doi.org/10.1108/ssmt.2000.21912bad.015
Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Enhanced under-board heater from Metcal reduces the risk of board and component damage during BGA rework
Keywords Metcal, Heaters, Rework, Ball grid array
The complexity and reduced size of array packages, such as BGAs and certain types of CSPs, has made the successful rework of such devices, particularly on large multi-layer PCBs, increasingly challenging.
One of the primary reasons for damage caused during the rework process of BGAs is insufficient under-board heating. This can create large delta temperature (T) gradients across a PCB, which can cause both board and component warpage, resulting in major defects such as unsoldered joints and solder shorts.
Insufficient underside heating also demands excessive topside heating to be applied in order to quickly bring the solder joints of a BGA to reflow temperature. This can cause other serious problems, such as component delamination (or "pop corning"), where atmospheric moisture absorbed by a plastic component expands under rapid heating and creates an internal cavity that can produce external blistering of its plastic casing.
To overcome these problems, Metcal has developed an enhanced underboard heater for use on its BGA 3590 Micro OvenTM rework system (Plate 5).
Plate 5 Enhanced under-board heater from Metcal
The new 1,400-Watt heater assembly is one of the most powerful systems currently available. The heater consists of a specially designed domed dish and diffuser to allow the forced convection hot air to heat up more quickly and to then be evenly distributed across the underside of a large PCB. As a result, a T of less than 30°C across a 400mm x 400mm board can be easily achieved.
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