Cause analysis of uneven reflow heating
Author:Water stop Time:2021-06-06 15:44 Browse(778)
Cause analysis of uneven reflow heating, touch screen and OLED Forum
The reasons for the uneven heating of components in reflow soldering process are the difference of heat capacity or heat absorption of reflow soldering components, the influence of conveyor belt or heater edge, and the load of SMT reflow soldering products.

Cause analysis of uneven reflow heating

the results show that the uneven heating of components in reflow soldering process is caused by the difference of heat capacity or heat absorption of reflow soldering components, the influence of conveyor belt or heater edge, and the load of! C% S1 b( I* p8 F) r# H# Z; _ 4 ]    R4 |0 G.
b4 S* R$ s+ J/ U+ z% S& A8 k, k1. Generally, the heat capacity of PLCC and QFP is larger than that of discrete chip components, and it is more difficult to weld large area components than small ones! r5 H/ o# I( M4 G& ? 9 W" h( v3 y5 j' G& S/ c. c) B& U* ~; In SMT reflow furnace,
the conveyor belt refluxes around and becomes a heat dissipation system.
in addition,
the edge of the heating part is different from the central heat dissipation condition, and the temperature of the edge is usually low.
when the temperature requirements are different.
the temperature of the same surface is also different.
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~! v* I1 D& S( K" h3. The influence of different product load.
the adjustment of SMT reflow temperature curve should consider no load.
good repeatability under load and different load factors.
the load factor is defined as: LF=L / (L + s); Where l=the length of the assembled substrate.
s=the distance between the assembled substrates.
s=the distance between the assembled substrates    A8 G) i    b8 q0 y6 g# l1 h" \- ~: `8 I* V4 s' K7 o9 x+ m) T8 J; ~ 4. The refluxing process needs repeatable results.
the results show that the refluxing process is feasibleThe larger the load factor is, the more difficult it is.
generally.
the maximum load factor of reflow furnace ranges from 0.5 to 0.9.
this depends on the product (component welding density, different substrates) and different models of reflow furnace.
practical experience is very important for obtaining good welding effect and repeatability.
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