Five causes of PCB board deformation and six solutions 2021-10-08

PCB The circuit board is deformed 5 Reasons and 6 A solution

With the development of surface mount technology, high precision 、 high velocity 、 Intelligent development , Yes PCB The flatness of the plate also has higher requirements .PCB Plate deformation is a very troublesome thing for many assembly plants , Today I want to share with you some pcb Causes and solutions of plate deformation ！

Lead to PCB Cause analysis of plate deformation ：
1. When the circuit board is designed, the copper sheet is unevenly distributed , Warping occurs after pressing .
2. The circuit board is impacted by external cold and heat , Sudden cooling and sudden heating .
3. Poor quality of circuit board .
4. The panel size is too large .
5. The circuit board is irregular .

in the light of PCB The solution to the cause of plate deformation ：
1、 Reduce temperature
The temperature is PCB The main source of plate stress , Just reduce the temperature of the reflow furnace or slow down the heating and cooling speed of the circuit board in the reflow furnace , The occurrence of bending and warping can be greatly reduced .
2、 Adopt high Tg The board of
Tg It is the temperature at which the material changes from glass state to rubber state ,Tg The lower the value of the material , Indicates that the faster the circuit board starts to soften after entering the reflow furnace , And it takes longer to become soft rubber , Of course, the more serious the deformation of the circuit board , Adopt higher Tg The plate can increase its ability to bear stress and deformation .
3、 increase PCB The thickness of the plate
If there is no light requirement ,PCB It is better to use 1.6mm The thickness of the , It can greatly reduce the risk of bending and deformation .
4、 Reduce PCB Size of panels and number of panels
Most of the reflow furnaces are driven by chains PCB The board moves forward , Try to put PCB The long edge of the plate is placed on the chain of the reflow furnace as the edge of the plate , Can reduce PCB The concave deformation caused by the weight of the plate itself , Reducing the number of panels is also based on this reason . That is to say, when it comes to the furnace , Try to use the narrow side perpendicular to the furnace passing direction , It can achieve the lowest sag deformation .
5、 Used furnace tray fixture
Whether it is heat expansion or cold contraction , The tray can be fixed PCB Wait until the temperature of the board is below Tg After the value starts to harden again , Can also maintain the original size .
If a single-layer pallet cannot be lowered PCB Deformation of plate , Then add another layer of cover , hold PCB The board is clamped with two layers of pallets , This can greatly reduce PCB The plate is deformed after passing through the reflow furnace .
6、 Use real connection instead 、 Stamp hole , replace V-Cut The use of
since V-Cut Will destroy PCB The structural strength of the panel between panels , Try not to use V-Cut Partition of , Or lower V-Cut The depth of the .

The above is pcb Causes and solutions of plate deformation , I hope that's helpful ！

Knowledge supplement ：
On the automated surface mount line , As the home of various components PCB If the plate is uneven , It will cause inaccurate positioning 、 Components cannot be inserted or attached to the holes and surface mounting pads of the circuit board , In serious cases, the automatic inserting machine may be damaged .

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