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Products > Packages > Semiconductor Device Mount Manual > NOTES ON MOUNTING > BGA Bonding Process >

CHAPTER 4 NOTES ON MOUNTING


4.3 BGA Bonding Process
4.3.1 Case 1. Insufficient heat application

If the reflow temperature profile is inappropriate, the solder joint may not receive sufficient heat. Figure 4-8 shows an example of what is observed to happen to the solder joint when the heat application conditions are changed. Both the external appearance and a cross-sectional view are shown.
If the peak temperature is too low and the time at melting point or higher is too short, the solder paste and solder balls may not melt and fuse together (Condition 1), or, even if they do melt, the form of the joint may be bad and the stand-off too high (Condition 2). As the peak temperature is raised and the time at melting point lengthened, the form of the solder joint improves (Condition 3). The best solder bond can therefore be obtained by setting appropriate heat application conditions (Condition 4).


State of Solder Joint under Various Heat Application Conditions
Figure 4-8. State of Solder Joint under Various Heat Application Conditions
To 4.3 BGA Bonding ProcessTo 4.3.2 Case 2. Unmelted solder