The deformation of PCB board needs to be studied from several aspects such as material, structure, pattern distribution and processing process.
The uneven copper surface area on the board will deteriorate the board bend and the board curl.
Generally, a large area of copper foil is designed for grounding. Sometimes the Vcc layer is also designed with a large area of copper foil. When these large areas of copper foil are not evenly distributed on the same board. When it is on, it will cause the problem of uneven heat absorption and heat dissipation. The circuit board will of course also expand and contract. If the expansion and contraction cannot cause different stresses and deformation at the same time, the temperature of the board will have reached this time. At the upper end of the Tg value, the board begins to soften, causing permanent deformation.
The junctions (vias) of the various layers on the board limit the board's expansion and contraction.
Most of today's circuit boards are multi-layer boards, and there are joints (vias) to the rivets between the layers. The connection points are divided into through holes, blind holes and buried holes. Where there are joints, the board is limited. The effect of rising and contracting will indirectly cause the plate to bend and the plate to be warped.
Reasons for PCB board deformation:
(1) The weight of the circuit board itself will cause the board to be deformed
In general, the reflow oven uses a chain to drive the board forward in the reflow oven, that is, the two sides of the board are used as fulcrums to support the entire board. If the board has heavy parts or the size of the board is too large, It will show the phenomenon of the middle depression due to its own quantity, causing the plate to bend.
(2) The depth of V-Cut and the connecting strip will affect the deformation of the panel
Basically, V-Cut is the culprit in destroying the structure of the board. Because V-Cut cuts the groove on the original sheet, the V-Cut is prone to deformation.