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How to Prevent PCB from Warping? Here's The Answer

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Ceramic substrates,PCB factory manufacturing process anti-plate warping methods are as follows:

  1.Engineering design:matters needing attention in PCB design:

  The arrangement of interlaminar semi-cured sheets should be symmetrical,such as six-layer sheets,the thickness between 1-2 and 5-6 layers and the number of sheets of semi-cured sheets should be the same,otherwise the core and semi-cured sheets of multi-layer sheets should be simply warped after lamination;the product of the same supplier should be used for multi-layer core board and semi-cured sheets;the circuit graphic area of outer A and B surfaces should be as close as possible.If the A side is a large copper side and the B side only takes a few lines,the printed circuit board will simply warp after etching.If the line area difference between the two sides is too large,some independent grids can be added to the sparse side to balance.

  2.Drying plate before cutting:

  The purpose of drying the copper clad sheet before cutting(150 degrees Celsius,8+2 hours)is to remove the moisture in the sheet,and to solidify the resin in the sheet completely,further eliminate the remaining stress in the sheet,which is helpful to avoid the warping of the sheet.Nowadays,many double-sided and multi-layer boards still adhere to the process of drying before or after cutting.But there are also some exceptions.Now the time rules of drying boards in PCB plants are not the same.They are available from 4 to 10 hours.It is advocated that the decision should be made according to the grade of printed boards produced and the warpage requirements of customers.After cutting into splices,drying is still the blanking of the whole bulk material after drying.Both methods are feasible.It is advocated that after cutting,drying plate.The inner panel should also be baked.

  3.Longitudinal and latitudinal directions of semi-cured sheets:

  The longitudinal and latitudinal shortening rates of semi-cured laminates are different after lamination.It is necessary to distinguish the meridional and latitudinal directions when cutting and laminating.Otherwise,after lamination,the warpage of finished sheet can be easily formed,and even the pressure baking sheet can hardly be corrected.Many of the reasons for the warping of multilayer plates are that the longitude and latitude of the semi-cured sheets are not clearly distinguished during lamination,and they are formed by random stacking.

  How to distinguish between longitude and latitude?The direction of rolled semi-cured sheets is longitude,while the width direction is latitude;for copper foil sheets,the direction of long side is longitude and latitude,and the direction of short side is longitude.If it is uncertain,it can be consulted with the manufacturer or supplier.

  4.Stress relief after lamination:

  After hot pressing and cold pressing,the multilayer board is removed,trimmed or milled,and then dried flat in the oven at 150 degrees Celsius for 4 hours to gradually release the stress in the board and completely solidify the resin.This process can not be omitted.

  5.Straightening is necessary for thin plate plating.

  Special clamping rollers should be made for plating and graphic plating of 0.4-0.6 mm ultra-thin multilayer plates.After clamping thin plates on the flying bars on the automatic plating line,the clamping rollers on the flying bars are strung together with a round stick,and then all the plates on the rolls are drawn straight,so that the plated plates will not be deformed.Without this method,the sheet would be tortuous and difficult to remedy after electroplating a copper layer of 20 to 30 microns.

  6.Cooling of plate after hot air leveling:

  Printed board hot air rectification is usually impacted by solder bath(about 250 degrees Celsius).After removal,it should be placed on flat marble or steel plate to cool naturally and sent to the post-processing machine for cleaning.This is good for preventing the board from warping.Some factories to enhance the brightness of the appearance of lead and tin,hot air leveling plate immediately into cold water,a few seconds after removal for post-processing,such a hot and cold impact on certain types of plates is likely to warp,stratification or blistering.Air float bed can be installed on other equipment for cooling.

  7.Treatment of warping board:

  Ceramic substrates,well-managed factories and printed boards will be inspected for 100%flatness during final inspection.All unqualified boards will be picked out and placed in the oven,baked at 150 degrees Celsius and under heavy pressure for 3 to 6 hours,and cooled naturally under heavy pressure.Then the plate is removed by pressure relief and checked for flatness,which can save part of the board.Some boards need two or three times of drying and pressing before they can be leveled.If the above mentioned anti-warping process is not implemented,some boards are useless for drying and pressing,and can only be scrapped.

Ceramic substrates

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