Study On Electrodeposited Copper Foil Of Very Low Profile Used In Printed Circuit Board Of High Density Interconnection

In response to the trend of high-frequency and miniaturization of 3G mobile communication equipment, electrodeposited copper foil of very low profile becomes one of the highlights of high-performance copper foil. In this thesis, we adopt the process of DC deposition and study electrodeposited copper foil of very low profile, in order to resolve the contradiction between low profile and high peel strength.According to the principle of electrodeposition and the process of the DC deposition, we analyse several factors. The factos include the based solution of CuSO₄-H₂SO₄, temperature, pole pitch and current density, which may affect properties of electrodeposited copper foil. The properties include surface roughness, peel strength, appearance and current efficiency, etc. The results show that the optimal process: C(Cu²⁺): 100±5 g/L, C(H₂SO₄): 120±5 g/L, temperature: 52±1℃, polar distance: 12 dm, current density: 4 A/dm², time:20 min. At then, the surface roughness is 7.0±1.0 um, thickness is 13.6±1.4 um and electrodeposited efficiency (η) is above 90 percent.However, the surface is not flat and there is pinhole. In addition, by adding appropriate additives(such as Gelatin,Hydroxyethyl cellulose,Sodium 3,3'-dithiodipropane sulfonate,Polyethylene glycol) and using the method of uniform design, we resolve this problem quickly and produce the performance of very low profile with higher peel strength. The results show that two optimal proportions of mixing additives: Gelatin: 1.2 g/L, HEC: 2.8 g/L, SPS: 6 mg/L, PEG: 0.42 ml/L or Gelatin: 2.6 g/L, HEC: 0.2 g/L, SPS: 5 mg/L, PEG: 0.27 ml/L. At this time, the surface roughness and pinhole of original sample disappears. Furthermore, the performance of surface roughness is 3.44±0.15 um, peel strength is 0.259 N/mm, thickness is 27.7±0.5 um or surface roughness is 2.58±0.10 um, peel strength is 0.238 N/mm and thickness is 27.7±0.5 um.Traditional disposal process is improved by the disposal process of low coarsening. The original sample of 12 um is treated by the disposal process of low coarsening (coarsening, solidification, blacking). At the same time, the treatment of coarsening, solidification and blacking are analyzed by several factors. There are basic solution of CuSO₄-H₂SO₄, temperature, current density and electrodeposited time, which may affect properties of electrodeposited copper foil. The properties include surface roughness, peel strength, plate shelling, etc. When we use disposal process of low coarsening, surface roughness is 4.5±0.2 um, peel strength is 0.938 N/mm. Moreover, the plate shelling is not obvious.In orde to improve the performance of peel strength, the original and low coarsening copper foil (18 um) which is treated by silane coupling agent are compared. The results show that the original foil of 18um (surface roughness is 4.3±0.2 um, peel strength is 0.40±0.05 N/mm) and treated one (surface roughness is 5.2±0.2 um, peel strength is 0.85±0.05 N/mm) are analyzed. The amount of silane coupling agent are 0.04 ml/L and 0.16 ml/L respectively. Relevantly, surface roughness and peel strength of original foil is 4.42 um and 0.54 N/mm. On the contrary, the treated one is 5.41 um and 1.36 N/mm.