mproving Parylene Adhesion

Parylene provides an entirely conformal, durable, pinhole-free substrate coating of extreme utility for an exceptional range of materials, products and purposes. Despite its many advantages, parylene's chemical structure can actually interfere with the reliable interface adhesion required for optimal performance. The chemical vapor deposition (CVD) process that generates so many of parylene's benefits also nullifies chemically-based substrate adhesion; only mechanical adhesion is possible.

Implementing optimal adhesion can require surface modification via application of adhesion promoting agents or methods. The materials and processes used for these purposes are largely dependent on the substrate surface and component's specific operational environments and functions. Although most adhesion promotion methods are used prior to CVD, several can be integrated into the coating-process itself, Among the methods of adhesion promotion used with parylene are:

·        Thorough surface-cleaning, which stimulates enhanced adhesion by eliminating accumulated substrate contaminants whose presence can diminish overall coating quality.

·        Heat-treating. for three hours at temperatures of 140°C, beneficially activates longer-term adhesion and insulation.

·        Active, wired devices profit from bilayer component-encapsulation processes.

While these techniques have their uses for parylene adhesion promotion, the chemical monolayer Silane A-174 (3-Methacryloxypropyltrimethoxysilane - C10H20O5Si) is used most frequently to modify substrate surfaces and improve parylene adhesion.

The Uses of Silane A-174

Silane A-174's value as an adhesion promoting agent stems largely from its versatility. It can be successfully applied to substrate materials like elastomer, glass, metal, paper, plastic or quartz, among a wide range of surface substances. The A-174 silane molecule develops a robust chemical bond with the substrate, facilitating the improved surface adhesion capacity of parylene’s mechanical property. Optimal parylene adhesion is commonly achieved by a treatment with A-174 silane prior to initiating the CVD process. However, regarding appropriate procedural scheduling:

·        it is recommended that A-174's application be completed after any necessary masking operations have been finished;

·        depending on substrate materials, manual spray, soaking, or vapor phase silane processing techniques may be used to apply A-174.

Process Balance

While the silane promotes adhesion, the parylene assures protection. Thus, appropriately proportional intermixtures of silane A-174 and parylene need to be used, in all cases. Corrosion-resistance can be diminished where the relationship between parylene and silane is inexact, causing part and function deterioration from both beneath- and external to the conformal covering. This is especially the case with medical implants, where reliable component function is mandatory, despite being subjected to persistent exposure to often harsh bodily fluids.

Of the two basic methods for applying silane A-174 to substrates, the first, in-chamber vapor delivery, is somewhat easier to enact but offers significantly diminished coating outcomes. Silane vapor promotion is impossible to efficiently supervise during real time, causing a proportional loss of effective process monitoring. As a consequence:

·        the potential of operator error increases,

·        leading to a far greater incidence of insufficient or excessive silane promotion;

·        imperfect silane surface-conformity frequently develops under these conditions,

·        stimulating degraded parylene coverage during the subsequent deposition cycle.

Thus, the problems inherent in achieving inappropriate production-intermixture alluded to above are more likely to occur, adding to production downtime and expense, as well as customer dissatisfaction.

The wet application method of silane application further allows inspection and monitoring of the immersion-solution throughout the process. Following silane A-174 immersion, CVD processes for parylene application should be implemented within 30 hours.

Mixing only the quantity of silane required for the procedure at hand is recommended, to assure appropriate preparation/application and safe work conditions, Silane's 24-hour shelf-life precludes storage of any excess, which should be discarded immediately in a solvent sink, subsequently drained, then rinsed with IPA. At all times, avoid breathing the solution's vapors or causing contact with skin or eyes:

Conclusion

Improving substrate adhesion is necessary because parylene will peel-off some substrates, if not appropriately treated with silane A-174. Immersion methods of application provide the most reliable solution.

簡單譯文

改善Parylene粘附力

       Parylene提供完全保形，耐用，無針孔的基材涂層，具有極高的實用性，適用于各種材料，產品和用途。盡管聚對二甲苯具有許多優點，但它的化學結構實際上可能會干擾最佳性能所需的可靠界面附著力?；瘜W氣相沉積（CVD）工藝產生如此多的聚對二甲苯的益處也使基于化學的基材粘附無效; 只能進行機械粘合。

       實施最佳粘合可能需要通過施加粘合促進劑或方法進行表面改性。用于這些目的的材料和工藝在很大程度上取決于基板表面和部件的特定操作環境和功能。盡管在CVD之前使用了大多數粘合促進方法，但是幾種可以整合到涂層工藝本身中。與聚對二甲苯一起使用的粘合促進方法包括：

·徹底的表面清潔，通過消除累積的基材污染物來刺激增強的附著力，其存在會降低整體涂層質量。

·熱處理。在140°C的溫度下保溫3小時，有利于激活長期粘合和絕緣。

·活動的有線設備從雙層組件封裝過程中獲益。

       雖然這些技術用于促進聚對二甲苯粘合，但化學單層硅烷A-174（3-甲基丙烯酰氧基丙基三甲氧基硅烷-C10H20O5Si）最常用于改性基材表面并改善聚對二甲苯粘合性。

硅烷A-174的用途

       硅烷A-174作為粘合促進劑的價值很大程度上源于其多功能性。它可以成功地應用于基體材料，如彈性體，玻璃，金屬，紙張，塑料或石英，以及各種表面物質。A-174硅烷分子與基材形成牢固的化學鍵，有助于提高聚對二甲苯的機械性能的表面粘附能力。最佳的聚對二甲苯粘合通常通過在開始CVD過程之前用A-174硅烷處理來實現。但是，關于適當的程序安排：

·建議在完成必要的掩蔽操作后完成A-174的申請;

·取決于基材材料，可以使用手動噴涂，浸泡或氣相硅烷處理技術來施加A-174。

流程平衡

       雖然硅烷促進粘合，但聚對二甲苯確保了保護。因此，在所有情況下，需要使用適當比例的硅烷A-174和聚對二甲苯的混合物。當聚對二甲苯和硅烷之間的關系不精確時，可以減少耐腐蝕性，從而使共形覆蓋物的下方和外部部分和功能劣化。對于醫療植入物尤其如此，其中可靠的組件功能是強制性的，盡管經常暴露于通?？量痰捏w液中。

在將硅烷A-174應用于基材的兩種基本方法中，第一種室內蒸汽輸送在某種程度上更容易實施，但涂層效果顯著降低。硅烷蒸氣促進不可能在實時有效監督，導致有效過程監測的比例損失。作為結果：

·操作員錯誤的可能性增加，

·導致硅烷促進不足或過量的發生率更高;

·在這些條件下經常發生不完美的硅烷表面整合，

·在隨后的沉積循環期間刺激降解的聚對二甲苯覆蓋。

因此，在上面提到的實現不適當的生產 - 混合的固有問題更可能發生，增加了生產停工和費用，以及顧客不滿意。

       硅烷應用的濕法施加方法還允許在整個過程中檢查和監測浸沒溶液。在硅烷A-174浸漬之后，應在30小時內實施用于聚對二甲苯的CVD工藝。

建議僅混合手頭程序所需的硅烷量，以確保適當的制備/應用和安全的工作條件，硅烷的24小時保質期不允許存儲任何多余的，應立即丟棄在溶劑槽中，隨后耗盡，然后用IPA沖洗。在任何時候，避免呼吸溶液的蒸氣或導致皮膚或眼睛接觸：

結論

       改善基材粘合是必要的，因為如果沒有用硅烷A-174適當處理，聚對二甲苯將剝離一些基材。浸入式應用方法提供了最可靠的解決方案。

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