Effectiveness and Characterization of OSP Film in Lead free Process of PCB Copy Board
Performance and Characterization of OSP Film in Lead free Process Printed Circuit Board
OSP films are mainly composed of organometallic polymers and small organic molecules entrained during deposition, such as fatty acids and azoles. The organometallic polymer provides the corrosion resistance, copper surface adhesion and surface hardness required by OSP. The degradation temperature of organometallic polymers must be higher than the melting point of lead-free solders to withstand the lead-free process. Otherwise, OSP film will be degraded after lead-free processing. The degradation temperature of OSP film depends largely on the heat resistance of organometallic polymer. Another important factor affecting the oxidation resistance of copper is the volatility of azole compounds, such as benzimidazole and benzimidazole. During lead-free refluxing, small molecules of OSP film will evaporate, which will affect the oxidation resistance of copper. Gas chromatography-mass spectrometry (GC-MS), thermogravimetric analysis (TGA) and photoelectron spectroscopy (XPS) can be used to scientifically explain the heat resistance of OSP.
Ass spectral analysis
The test copper plate is coated with: a) new HTOSP film; b) Industry standard OSP film; And c) another industrial OSP film. Scrape off about 0.74-0.79 mg of OSP film from the copper plate. These coated copper plates and scraped samples have not undergone any reflow treatment. In this experiment, H/P6890GC/MS instrument and syringe without syringe were used. The syringe without syringe can directly desorb the solid sample in the sample chamber. The syringe without syringe can transfer the sample in the small glass tube to the inlet of the gas chromatograph. The carrier gas can continuously bring volatile organic compounds into the gas chromatographic column for collection and separation. Place the sample near the top of the chromatographic column so that thermal desorption can be effectively repeated. After desorbing enough samples, the gas chromatography starts to work. In this experiment, RestekRT-1 (0.25mm id * 30m, membrane thickness 1.0mm) gas chromatographic column was used. Temperature rise program of gas chromatographic column: After heating at 35 ° C for 2 minutes, the temperature starts to rise to 325 ° C, and the temperature rise rate is 15 ° C/minimum. The thermal desorption condition is: after heating at 250 ° C for 2 minutes. The mass/charge ratio of the separated volatile organic compounds is detected by mass spectrometry in the range of 10-700 Daltons. The retention time of all organic small molecules was also recorded.
Thermogravimetric analysis (TGA)
Similarly, a new HTOSP film, industry standard OSP film, was coated with another layer of industrial OSP film on the sample About 17. Scrape 0 mg OSP film from the copper plate as the data test sample Before TGA test, samples and films cannot be refluxed without lead Use TA Instruments' 2950TA to conduct TGA test under nitrogen protection The operating temperature shall be maintained at room temperature for 15 minutes, and then increased to 700 ° C/min at the rate of 10 ° C
Photoelectron spectroscopy (XPS)
Photoelectron Spectroscopy (XPS), also called Chemical Analysis Electron Spectroscopy (ESCA), is a chemical surface analysis method XPS can measure the 10 nm chemical composition of the coating surface Apply HTOSP film and industry standard OSP film on the copper plate, and then conduct 5 times of lead-free reflow XPS is used to analyze HTOSP films before and after reflux treatment The industry standard OSP film after five lead-free refluxes was analyzed by XPS The instrument used is VGESCALABMarkII
Through hole solderability test
Using solderability test boards (STVs) for through-hole solderability testing. There are a total of 10 solderability test board STV arrays (each array has 4 STVs) coated with a film thickness of about 0.35m Then, the coated STV is subjected to a series of high temperature, lead-free reflow treatment in the solder paste reflow furnace Each test condition includes 0, 1, 3, 5 or 7 consecutive refluxes For each reflow test condition, each type of film has 4 STVs After reflow, all STVs are subject to high temperature lead-free wave soldering Through hole weldability can be determined by checking each STV and calculating the number of correctly filled through holes The acceptance criteria of the through-hole is that the filled solder must be filled to the top of the plated through-hole or the upper edge of the through-hole
Each STV has 1196 through holes
Test the solderability through a tin-dip balance
The solderability of OSP film can also be determined by dip tin balance test. Apply HTOS P film on the test plate of the tin immersion balance. After 7 times of lead-free refluxing, t peak value=262 ℃ Use BTUTR in combination with IR/convection reflux furnace backflows in air Carry out moisture balance test according to IPC/EIAJ-STD-003A Section 4. 3.1.4. Use "RoboTICProcessSystems" automatic moisture balance tester, EF-8000 flux, non cleaning flux and SAC305 alloy solder
Welding bonding force test
Welding bonding force can be measured by shearing force. Coat the HTOSP film on the BGA pad test board (diameter 0.76mm), with a thickness of 0.25 and 0 respectively of 48 mm, and conduct three times of lead-free reflux treatment at the highest temperature of 262 ° C
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