| 摘要: | FR-4即玻璃纖維增強電子級環氧樹脂，具良好電氣絕緣性能、高機械強度、高耐熱性、高化學穩定度以及製造成本低的優勢，使它成為印刷電路板（PCB）基板的重要材料。而在FR-4分板切割方面，常用的技術有V-cut切割、高壓水射流切割與鑽石輪刀切割等。一般而言，輪刀切割法具有切割快速與良好的切面品質，一直是FR-4基板的主要分割技術。然而，隨者更輕薄短小、更高功能元件的市場需求，多層、更高密度的電路製作的需求也益發重要，面對線與線距縮小至數十微米或更小時，傳統上使用機械式的鑽石輪刀切割方式已逐漸呈現出極限性。
使用雷射切割具有: 精確、切口小、適用於複雜的形狀、無機械接觸可避免切割力造成損傷等優勢，被認為是有潛力的技術。然而，玻璃纖維和環氧樹脂的混合物對於雷射切割也具有一定的挑戰，如: 玻璃纖維在加工過程容易產生碎屑、毛刺和裂紋等問題，這些碎屑和毛刺會影響到基板的微精度和可靠性，此外環氧樹脂在雷射切割過程中容易因高熱效應，產生碳化層，碳化層會影響基板的電阻和介電常數，從而影響基板的電性能和信號傳輸性能，因此需要後處理以去除殘留的碳化物。為降低一般雷射切割的碎屑、毛刺與高熱效應問題，本研究使用超快雷射切割FR-4基板，期以超短脈衝期的高瞬間功率與低熱效應，提升切割品質。
本研究以飛秒雷射對厚度為0.2 mm與0.8 mm的FR-4基板分別在大氣與水中進行切割，比較切面品質與切割速率。結果顯示，相較於在大氣中切割，在水中切割，可獲得較少的碎屑殘留與較低的熱效應。在參數: 功率14.99 W、頻率500 kHz、掃描速度500 mm/s、水位高度2118 μm與掃描1250次下，可以得到近乎機械切割的高品質橫截面。此外，本研究亦對圖案化切割以及加工參數進行討論。
;FR-4, or glass fiber-reinforced electronic-grade epoxy resin, is a crucial material for printed circuit boards (PCBs) due to its excellent electrical insulation, high mechanical strength, elevated heat resistance, chemical stability, and cost-effectiveness. In the context of FR-4 substrate cutting, commonly employed techniques include V-cutting, high-pressure water jet cutting, and diamond wheel cutting. Generally, diamond wheel cutting has been the primary method for FR-4 substrate separation, offering fast cutting and good surface quality. However, with the market demand for smaller, lighter, and more high-functional components, the need for multi-layer and higher density circuit fabrication has become increasingly vital. As line widths and spacings shrink to tens of micrometers or smaller, traditional mechanical diamond wheel cutting methods are showing limitations.
Laser cutting, with advantages such as precision, small kerf, suitability for complex shapes, and no mechanical contact to prevent cutting force-induced damage, is considered a promising technology. However, the mixture of glass fiber and epoxy resin presents challenges for laser cutting. Glass fiber can generate debris, burrs, and cracks during processing, affecting the substrate′s micro-precision and reliability. Additionally, epoxy resin is prone to forming a carbonized layer due to the high thermal effects of laser cutting, influencing the substrate′s resistance and dielectric constant, thereby impacting electrical and signal transmission performance. Post-processing is necessary to remove residual carbonization.
To address issues like debris, burrs, and high thermal effects associated with conventional laser cutting, this study employs ultrafast laser cutting on FR-4 substrates. The aim is to enhance cutting quality by utilizing high instantaneous power and low thermal effects during ultra-short pulse durations. Using a femtosecond laser, the study compares the cutting quality and speed of 0.2 mm and 0.8 mm thick FR-4 substrates cut in both atmospheric and underwater conditions. Results indicate that cutting underwater yields fewer residual debris and lower thermal effects compared to cutting in the atmosphere. Under the parameter set: power 14.99 W, frequency 500 kHz, scan speed 500 mm/s, water level height 2118 μm, and 1250 scans, high-quality cross-sections comparable to mechanical cutting can be achieved. The study also discusses patterned cutting and processing parameters. |
