本研究對聚亞醯胺(polyimide,PI)表面增加粗糙度(Surface Roughness)，分別使用FEPA規範型號為F280、F240、F220與F150氧化鋁(Alumina)顆粒，以不同空氣壓力對聚亞醯胺表面進行噴砂，使用壓力為0.15x106帕(Pa)至0.5x106帕(Pa)，結果發現粗糙度隨著氧化鋁粒徑上升及壓力提升也隨之上升，並且均勻度相當好，粗糙度範圍在118–1189nm間，標準差皆為平均粗糙度的10%以內。
使用噴砂後的聚亞醯胺，以刮刀塗布上溶劑為水的奈米銀懸浮液，經過乾燥後，用高溫爐以220℃與280℃燒結20分鐘，再依American Society for Testing and Materials (ASTM) D3359與D4541規範測試奈米銀顆粒與PI基板之黏著性，將兩規範做相關性連結，得到其相對範圍。實驗結果為奈米銀對聚亞醯胺黏著隨粗糙度增加而上升，且可到達ASTM D3359的5B等級(最高)。
然而提升PI基板表面粗糙度雖有助於黏著性的提升，缺點為銀膜的體積電阻率也會上升。最佳值為使用型號F220的氧化鋁顆粒，使用0.4MPa的壓力噴砂兩次，使PI基板的粗糙度改善至792nm，塗上奈米銀後以280℃燒結，可得體積電阻率為1.48 x10-5Ω・cm的銀膜，電阻率大約為塊材銀(bulk silver)的9.4倍。當長度為11µm的銀絲3wt%取代12wt%銀顆粒後，與未加銀絲取代銀顆粒相比可改善13%的片電阻，且銀的使用量可以減少22.5%。
液滴乾燥研究中，液滴中奈米銀的濃度(固含量)會影響咖啡環的形成與其寬度，濃度0.08wt%以下將不會有咖啡環的形成。且液滴體積越大，環的寬度將增加。將溶劑為水的奈米銀懸浮液加入正丙醇，可降低液滴與玻璃之接觸，當正丙醇濃度為10wt%，有助於咖啡環的形成。奈米銀濃度為0.08wt%，液滴體積為1µL，正丙醇濃度為10wt%的水溶液，液滴乾燥後可得到咖啡環寬度為6.7微米(µm)，環內約300微米距離較少銀奈米粒子殘留。

The technique of sandblasting was utilized in this study on polyimide (PI) substrate. Alumina particles, F280, F240, F220, F150 (FEPA nomenclature) under air pressure 0.15x106 Pa to 0.50x106 Pa was used here. It was found that the average surface roughness of PI substrate increased with particle size and air pressure. The range of roughness was between 118 – 1189 nm, while the standard deviation was within 10% of average roughness suggesting reasonable uniformity of the process.
After sandblasting, the PI substrate was coated by silver ink by the doctor blade method. Solvent of the ink was water. The sample was then sintered at 220℃ and 280℃ for 20 minutes and then tested for adhesion by ASTM D3359 and D4541, with the intention to establish definite correlation between these two methods. Our results showed that the adhesion between silver colloids and PI substrate increased with increasing surface roughness and could reach the highest 5B level for rough PI substrate.
Nevertheless the increase in adhesion was accommodated by simultaneous increase in electrical resistivity of silver film after sintering. The optimal condition after compromise was: using F220 particle, 0.4 MPa air pressure to increase surface roughness to 792 nm. The adhesion level could reach 5B level and the electrical resistivity was 1.48x10-5 Ω-cm (about 9.4 times bulk value). If we substitute 12 wt% silver colloid by 3 wt% silver nanowire (11 micron in length), we could improve about 13% in electrical resistivity while the total quantity of silver was reduced by 22.5%.
On the study of drying behavior of ink droplet, it was found that coffee ring would not form when the solid content was below 0.08 wt%. It was also found that the ring width increased with droplet volume. Adding n-propanol would reduce the contact angle between ink and glass substrate. When the solid content was 0.08 wt%, droplet volume of 1 µl, 10% propanol in the solvent, one would obtain a good quality ring with width of 6.7 µm and almost no particles were observed within 300 µm from the ring.

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Standard Test Methods for Measuring Adhesion by Tape Test (ASTM D3359-08)

Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers (ASTM D4541-95)