PCB007 Magazine

PCB007-July2018

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JULY 2018 I PCB007 MAGAZINE 31 • Leaching experiments: Extracts were analyzed by GC-MS and HPLC-MS— identification of leach-out products. • Pyrolysis: GC-MS—identification of high molecular weight compounds Elemental Analysis This is a destructive technique that identi- fies the basic chemical characteristics by quan- titively isolating the elements carbon, hydro- gen, nitrogen and sulphur (CHNS). This meth- od examines the properties of the solder mask but can only be used as an early indicator. Al- though it is apparent that there is a discrep- ancy between the critical and non-critical sol- der masks, this method cannot determine the impact of this discrepancy on the plating pro- cesses. Figure 2 indicates that the presence of sul- phur is the key difference between the criti- cal and non-critical solder masks. This is bet- ter demonstrated in Figure 3. Whilst there is most likely a rational explana- tion for the presence of sulphur, the question that should be considered is whether weight percentages over 3.0 are required and whether an alternative exists. This is beyond the exper- tise of our facility and as such will not be fur- ther extrapolated upon. Fourier Transform Infrared Spectroscopy (FTIR) FTIR is a non-destructive technique that could be applied onsite. It is a quick test requir- ing no preparation resulting in a wave num- ber according to the molecules' ability to ab- sorb infrared light. This method can be used to identify the functional groups. Figure 4 dem- onstrates that at wave numbers of between 1075 and 1077 cm -1 a signal can be observed for the critical sample. From the elemental anal- ysis it has already been established that sam- ple ID 3 has a sulphur weight percentage of 3.7%. The wave number at 1075 cm -1 probably indicates the presence of sulphur. This method Figure 1: Demonstration of the state-of-the-art analysis applied.

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