With the continuous development of electronic components, components with bottom solder terminals are becoming more and more popular. DRQFN and MQFN are two typical components with bottom solder terminals. Let's first introduce DRQFN and MQFN. Please see Figure 1 for details (the solder terminals are all at the bottom of the component). With the continuous development of electronic components, components with bottom solder terminals are becoming more and more popular. DRQFN and MQFN are two typical components with bottom solder terminals. Let's first introduce DRQFN and MQFN. Please see Figure 1 for details (the solder terminals are all at the bottom of the component).
Figure 1
Please see Figure 2-7 for a list of common soldering issues for DRQFN and MQFN .
Figure 2 (Inner row SMD pads connected to tin)
Figure 3 (Inner row of solder joints is too wide)
Figure 4 (Pillow-shaped solder joint)
Figure 5 (SMD pad solder overflow )
Figure 6 (Large bubble at grounding)
Figure 7 (Solder overflow on inner row SMD pads )
Figures 2-7 above only list some of the welding problems. In fact, there are far more welding problems for DRQFN and MQFN than these. They are really varied and are a big problem in the industry!
How to ensure reliable soldering of DRQFN and MQFN? We recommend using Wangyou DFM design for manufacturability analysis software. Here we share with you the method to solve the problem from the source, hoping it will be helpful to you.
1. Device layout:
DRQFN and MQFN should be placed at the location with the smallest thermal deformation of PCBA as far as possible, so as to reduce thermal deformation from the source, as shown in Figure 8. If it is really impossible to guarantee, it is recommended to increase the board thickness or the Tg value of the PCB board, and strictly verify the thermal deformation of PCBA during trial production.
Figure 8
2. Pad design:
Here we only list the DRQFN pad design scheme, and MQFN can be used as a reference. For details, please refer to Figures 9-10 (for large pad design, the steel mesh opening is correspondingly reduced, which can improve the steel mesh opening area ratio from the source and ensure stable tinning during printing).
Figure 9
Figure 10
3. PCB routing (refer to Figure 11):
Figure 11
4. Steel mesh opening (refer to Figure 12):
The ground pad opening should be properly away from the exhaust hole (optional), and ensuring that the welding width of the inner pad is larger than the opening width of the steel mesh can prevent false welding; ensuring that the welding width of the inner pad is smaller than the pad width can prevent bridging and solder overflow of the SMD pad (wider pads can carry more solder, which can prevent bridging).
Figure 12
5. Furnace temperature recommendations:
The welding terminals of DRQFN and MQFN components are relatively small. It is recommended to appropriately reduce the preheating time and temperature of the furnace temperature to reserve more flux activity for the welding stage; the peak temperature of the furnace should not exceed 245°, the welding time should be controlled within 60-80 seconds, and the cooling rate should not exceed 2.5°/second. Figure 13 furnace temperature settings for your reference:
Figure 13
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