Issue link: https://iconnect007.uberflip.com/i/1002143
62 PCB007 MAGAZINE I JULY 2018 developable LPiSM specifically formulated for high temperature storage applications with a matching laminate. The results of the cross- hatch test according to EN ISO 2409 show that a purely mechanical treatment will not enable a long-term thermal storage/resistance even at 150°C. The measuring of breakdown voltage on a steel plate with 20 µm dry thickness (Figure 6) during 200°C storage for a total of 20 days in- dicates that with increasing thermal load insu- lation generally decreases and begins to fluctu- ate after approximately 10 days. This can po- tentially be caused by fissures and pores or mi- crobubbles. Figure 7 shows that the aim at least to main- tain the CTI value of the laminate can be met even after a 2000 hours thermal load at 175°C with specialty coatings. The Tg and CTE values as indicated in Table 3 seem to be largely independent of the cur- ing temperature. An additional triple reflow soldering process at 265°C seems to lead to a post cross-linking because the corresponding Tg values increase by approximately 20°C. The severe thermal load applied as indicated in Table 4 leads to a slight increase in the Tg Figure 4: Adhesion of LPiSM after temperature storage at 175°C. Figure 5: Adhesion of LPiSM after temperature storage at 200°C. Figure 6: Breakdown voltage during temperature storage at 200°C (coated steel plates). Figure 7: Tracking resistance after temperature storage at 175°C.