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How Can Polytetrafluoroethylene Circuit Board be Processed to Avoid Falling Off and Foaming?

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  In printed circuit board,polytetrafluoroethylene board is a kind of high frequency board,which has the advantages of high temperature resistance,corrosion resistance and high insulation.With the advantage of this board,it is used to process circuit board in many military products.However,because of the particularity of this kind of plate,the surface of the base material is smooth and the material is soft,which brings difficulties in the processing.Among them,the adjustable ones are resistance welding and milling shape.The following DPC ceramic small braid will tell you how to process the polytetrafluoroethylene circuit board without falling or foaming

  Welding resistance machining(comparison of two machining processes)

  1.General process:plate brushing-static setting(15 minutes)-silk screen welding resistance-static setting(15 minutes)-pre drying-static setting(15 minutes)-silk screen-static setting(15 minutes)pre drying-static setting(15 minutes)-exposure-static setting(15 minutes)-Development-single stage curing 155℃/60min

  2.Disadvantages of the product:lack of static storage,and then curing for staged baking,resulting in bubbles at the junction of substrate and graphics.

  Improved processing flow:

  1)brush plate-static(15 minutes)-silk screen solder mask-parallel static(30-60 minutes)-pre drying-static(15 minutes)-silk screen-static(60 minutes)pre drying-static(15 minutes)-exposure-static(15 minutes)-Development-single stage curing(80℃/20min+90℃/20min+100℃/20min+120℃/20min+155℃/60min)

  2)Long standing time,parallel standing,curing and sectional roasting together,the remarkable product is perfect.

  Analysis of improvement effect:the glass fiber cloth of polytetrafluoroethylene plate is obviously rough.The speed should be strictly controlled in the process of silk screen printing.The slower the speed is,the less bubbles are.As a result,the thickness of silk screen printing ink is thinner.The junction between the substrate and the line is covered with ink evenly,so that the diluent inside the ink will simply volatilize,which will not cause the board to shrink sharply when it is cured and baked at high temperature,resulting in Make ink bubble.However,the bottom copper plate with more than 1 oz must be placed horizontally after silk screen printing.Because of the high line,it can prevent the ink from accumulating in the same direction,resulting in uneven thickness of the ink.In the post curing error,polytetrafluoroethylene(PTFE)plate is a special material,and the expansion and contraction phenomenon is significantly larger than that of the general plate under high temperature.Therefore,it is necessary to cure the solder resist ink from low temperature to high temperature to prevent the solder mask from foaming.Through 288℃/10s/3 thermal shock test,the bonding rate between the solder mask and the base material was verified,without dropping.

  Through the sharing of the above DPC ceramic knits,we can know that the long standing time,parallel standing,post curing and sectional baking can make a non foaming and non dropping polytetrafluoroethylene circuit board.

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