Welding Area Treatment; Module Installation - Huawei ME909u-521 Hardware Manual

HUAWEI ME909u-521 LTE LGA Module
Hardware Guide
Figure 6-9 Equipment used for rework

6.10.4 Welding Area Treatment

Step 1 Remove the old solder by using a soldering iron and solder braid that can wet the
solder.
Step 2 Clean the pad and remove the flux residuals.
Step 3 Solder pre-filling: Before the module is installed on a board, apply some solder paste
to the pad of the module by using the rework fixture and stencil or apply some solder
paste to the pad on the PCB by using a rework stencil.

6.10.5 Module Installation

Install the module precisely on the module and ensure the right installation direction of
the module and the reliability of the electrical connection with the PCB. It is
recommended that the module be preheated in order to ensure that the temperature
of all parts to be soldered is uniform during the reflow process. The solder quickly
reflows upon heating so the parts are soldered reliably. The solder joints undergo
proper reflow duration at a preset temperature to form a favorable Intermetallic
Compound (IMC).
Issue 05 (2017-12-15)
 The LGA module has many solder pads and the pads are large. Therefore, common
soldering irons and heat guns cannot be used in the rework. Rework must be done using
either infrared heating rework stations or hot air rework stations. Infrared heating rework
stations are preferred, because they can heat components without touching them. In
addition, infrared heating rework stations produce less solder debris and less impact on
modules, while hot air rework stations may cause shift of other components not to be
reworked.
 You must not reuse the module after disassembly from PCB during rework.
 It is proposed that a special clamp is used to remove the module.
It is recommended that a fixture and a mini-stencil be made to apply the solder paste in the
rework.
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