Problems needing attention in PCB welding

Problems needing attention in PCB welding
2022-04-20 View：110 Author：PCB
The copper clad plate is processed into a printed circuit board, through holes and assembly holes, and various components have been assembled After assembly, welding is necessary in order for the components to contact the joints The soldering process is divided into three methods: wave soldering, reflow soldering and manual soldering Using separate manual (electromagnetic) iron) welding
printed circuit board
one € Solder resistance of copper clad laminates
As the abstract material of PCB, the copper clad plate contacts with metal So, this, this is a test of the heat resistance of copper CCL guarantees its product quality during thermal shock, which is an important aspect of evaluating CCL's heat resistance At the same time, the reliability, high temperature peel strength, and heat of copper clad plate in the welding process In addition to the traditional immersion welding resistance, some application programs have been used to measure and test the efficiency of copper clad plate welding in recent years to improve the reliability of copper Such as hygroscopic heat resistance test (treatment for 3 hours, then do 260 ⠄ƒ  dip soldering test), hygroscopic reflow soldering test (reflow soldering test at 30 ⠄ƒ,  70% relative humanity for a specified time) and so on Printed circuit board At the same time, after the PCB sample is made After confirming that this kind of base material conforms to
The method for determining the dip solder resistance of copper clad laminates is basically the same as my country International (GBIT 4722-92), American IPC standard (IPC-410 1), and Japanese JIS standard (JIS-C-6481-1996).  The main requirements are:
1) The method of arbitration determination is "floating soldering method" (the sample floats on the soldering surface);
2) The sample size is 25 mm X 25 mm;
3) If the temperature measurement point is a mercury thermometer, it means that the parallel position of the mercury head and tail in the solder is (25 ± 1) mm;  the IPC standard is 25.4 mm;
4) The depth of the solder bath is not less than 40 mm.
It Generally, the heating source of solder is The greater the distance (deeper) from the temperature measurement point to the solver liquid surface, this At this time, the lower the liquid level, the longer the foam
two € Wave soldering processing
In the wave soldering process, the welding temperature is actually the welding temperature, which is related to the welding type Welding Welding As a result, the immersion welding time is relatively short If the welding temperature is too high, it will be deleted and serial warming of the circuit (coupler tube) or subtract Therefore, the welding temperature should be
three € Reflow welding

Generally, this The setting of reflow soldering temperature is related to the following aspects:
1) The type of equipment for reflow soldering;
2) Setting conditions of line speed, etc;
3) Type and thickness of substitute materials;
4) The size of the PCB, etc
This At the same reflow setting temperature, the heat resistance limit of the abstract surface temperature where copper foil bulges (blistering) occurs will change with the preheating temperature of the PCB and the presence or absence of moisture absorption It can be seen from Figure 3 that when the preheating temperature of the PCB (the surface temperature of the substrate) is lower Under the condition of setting reflow temperature
four € Manual welding
When repair welding or separate manual welding of special components Shorten the time as much as possible. The general requirement is that the glass fiber cloth substrate is a printed circuit board

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