Package Mounting Methods
Package mounting methods can be broadly classified into two methods. One is the flow solder mounting method, and the
other is the reflow solder mounting method. In this section, the reflow soldering mounting method for mounting surface
mount type packages will be explained.
Selection of mounting materials
1. Printed circuit board design
Desirable conditions for printed circuit boards
Since surface mounting is high density and the semiconductor device bodies as well as the printed circuit board will be
directly subjected to high stress during the processes, printed circuit boards which will minimize the load transferred from
the printed circuit board to the semiconductor device bodies as much as possible should be selected.
Printed circuit boards with higher performance than in the past for characteristics such as heat resistance, moisture
resistance, dimensional change ratio, warpage, dimensional accuracy, etc. are desired.
Warpage and heat for surface mounting
Among the various conditions mentioned in the previous paragraph, let's consider the problems of warpage and heat. In
conventional mounting, the heat of soldering is blocked by the printed circuit board, so that the semiconductor device
body on the opposite side is not greatly affected. But in surface mounting, the semiconductor device body is subjected to
high temperatures, and directly receives heat stress. In addition, since the semiconductor device body is adhered directly to
the printed circuit board, warpage or shrinkage due to the soldering becomes stress applied directly to the semiconductor
device body or poles. (Figure 1)
[ Lead-through mounting ]
Printed circuit board
[ Surface mounting ]
Printed circuit board
Before soldering
Heat tempering
Figure 1 Warpage and heat during surface mounting
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