Reasons for blistering of multilayer circuit board
(1) Improper suppression leads to the accumulation of air, moisture and pollutants;
(2) In the process of pressing, due to insufficient heat, too short cycle, poor quality of semi cured sheet and incorrect function of press, the curing degree is problematic;
(3) Poor blackening treatment of inner circuit or surface pollution during blackening;
(4) The inner plate or semi cured sheet is contaminated;
(5) Insufficient glue flow;
(6) Excessive glue flow - almost all the glue content in the semi cured sheet is extruded out of the plate;
(7) Under the demand of no function, the inner layer board shall minimize the occurrence of large copper surface (because the bonding force of resin to copper surface is far lower than that of resin and resin);
(8) When vacuum pressing is used, the pressure is insufficient, which will damage the glue flow and bonding force (the residual stress of the multilayer plate pressed by low pressure is also less).
Solution to foaming of multilayer circuit board
(1) The inner layer board shall be baked and kept dry before lamination pressing.
Strictly control the process procedures before and after pressing to ensure that the process environment and process parameters meet the technical requirements.
(2) Check the Tg of the pressed multilayer board, or check the temperature record of the pressing process.
Bake the pressed semi-finished products at 140 ℃ for 2-6 hours, and continue the curing treatment.
(3) Strictly control the process parameters of oxidation tank and cleaning tank of blackening production line, and strengthen the inspection of the appearance quality of the board surface.
Try double-sided copper foil (dtfoil).
(4) Cleaning management of operation area and storage area shall be strengthened.
Reduce the frequency of manual handling and continuous plate removal.
During stacking operation, all kinds of bulk materials shall be covered to prevent pollution.
When the tool pin must be subject to the surface treatment of lubricating off pin, it shall be separated from the laminated operation area and cannot be carried out in the laminated operation area.
(5) Appropriately increase the pressure intensity of pressing.
Appropriately slow down the heating rate and increase the glue flow time, or add more kraft paper to ease the heating curve.
Replace the semi cured sheet with high glue flow or long gelling time.
Check whether the steel plate surface is flat and free of defects.
Check whether the length of the locating pin is too long, resulting in insufficient heat transfer due to the lack of tightness of the heating plate.
Check whether the vacuum system of the vacuum multilayer press is in good condition.
(6) Properly adjust or reduce the pressure used.
The inner layer board before pressing needs to be baked and dehumidified, because the water will increase and accelerate the glue flow.
Use semi cured sheets with low glue flow or short gelling time.
(7) Try to etch away the useless copper surface.
(8) Gradually increase the pressure strength used for vacuum pressing until it passes five floating welding tests (288 ℃ for 10 seconds each time)
