CupraEtch FH™: New advanced low-etch depth soldermask and photoresist pretreatment

One key application for the manufacturing of MLB and HDI printed circuit boards are pretreatment systems aimed at providing the optimum adhesion of organic coatings such as Photoimagable Resists (such as Dry Films [DF] and Liquid Photo Imageable Resists [LPIR]) or Solder Mask's (SM). The most common way for this optimum adhesion to be achieved is to use an etching solution to roughen the copper surface to give the highest possible increase in surface area with the minimum removal of copper. Probably the most challenging of these applications is the adhesion promotion for SM. This is because the improvement in adhesion here must be on a "permanent" basis as once the SM is applied, the good adhesion of the SM to the copper surface must continue through the life of the panel through all downstream processes. This includes application of final solderable finishes such as Immersion Tin and ENIG (both of which can damage the SM integrity and can attack the SM to Copper interface) and throughout final assembly where repeated high temperature soldering applications must be withstood. The industry demand for finer lines and spaces, higher signal integrity and above all lower etch depth requirements for the above described DF, LPIR and SM pretreatments have to be balanced with the performance demands for the application in question the OEM performance demands to the final panel. In this regard, Atotech here present a new ferric-sulfate based process CupraEtch FH™ which is both technically and commercially superior to existing POR pretreatment chemistries.