Package Mounting Methods
Soldering
1) Soldering method
Soldering of semiconductor devices can be broadly classified as flow soldering and reflow soldering. In addition, reflow
soldering can be further classified into full-body heating or partial heating.
Flow soldering solders together with lead-equipped components in a single process, and is suitable for mass
production.
Reflow soldering enables high-accuracy soldering through the use of cream solder, but care must be taken with the
infrared radiation system for temperature control. In addition, to overcome the faults of the infrared radiation system,
systems combining the infrared radiation system and hot air flow are becoming popular.
Using a laser beam or light beam causes little thermal stress and enables precise soldering, making it suitable for multi-
pin LSI mounting. (Table 2)
Table 2 Soldering methods for semiconductor devices
Evaluation
Method
Heat source
Features
Productivity
Flow
Wave solder
Infrared radiation
Full-body heating
reflow
Infrared radiation and
hot air flow
VPS
Hotplate
Partial heating
reflow
Laser/light beam
Enables soldering with lead-equipped
components in a single process
Heating of entire body with beam radiation
Temperature control is relatively easier.
Uniform steam heating to 215°C
Heat conductance reduces stress.
High-accuracy spot heating
Soldering
accuracy
Temperature
accuracy
Thermal
stress
2) Soldering temperature profile
Since surface mounting applies drastic temperature variations directly to the bodies of semiconductor devices, sufficient
care must be taken with temperature control, especially for solder.
In flow soldering, a maximum temperature of 260°C for 3 to 5 seconds is common. The soldering time for the double-
wave method is the sum of the two waves.
In reflow soldering, in general preheating is performed using far infrared radiation and the actual heating is performed
using near infrared radiation. Care must be taken with infrared radiation, since the temperature depends on the color,
material, size, etc. of the semiconductor device and printed circuit board and there will be differences between the surface
and internal temperatures. In addition, it is necessary to set individual optimum temperatures, depending on the mounting
conditions. Examples of soldering temperature profiles are shown in Figure 9. Also, please check with the sales division
of our company as to whether or not the semiconductor device you are investigating is compatible with Pb-free solder.
Package surface temperature
Package surface temperature
Package surface temperature
10s max.
260°C max.
255°C
170°C
60 to 120s
10s max.
2°C/s to 5°C/s
150°C
60 to 120s
240°C max.
235°C
20s max.
215°C max.
150°C
60 to 120s
Time
(a) Hot air flow or infrared radiation reflow soldering
(Products with Pb-free solder)
Time
(b) Hot air flow or infrared radiation reflow soldering
(Products with Pb solder)
Time
(c) Vapor phase reflow
Figure 9 Examples of soldering conditions
M16
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