焊接面罩，也稱為阻焊面罩，是一層薄薄的聚合物，用於 PCB板 以防止焊點形成橋接。 焊接面罩還可以防止氧化，適用於 PCB 板上的銅跡線。

What is PCB solder resistance type? The PCB welding mask acts as a protective coating on the copper trace line to prevent rust and prevent solder from forming Bridges that lead to short circuits. PCB焊接面罩主要有4種類型——環氧樹脂液體、液體可照相、乾膜可照相以及頂部和底部掩模。

四種電焊面罩

焊接面罩的製造和材料各不相同。 如何使用以及使用哪種焊接面罩取決於應用。

頂部和底部側蓋

頂部和底部焊接掩模電子工程師經常使用它來識別綠色阻焊層中的開口。 該層是通過環氧樹脂或薄膜技術預先添加的。 然後使用與掩模對準的開口將元件引腳焊接到電路板上。

The conductive trace pattern on the top of the circuit board is called the top trace. 與頂面罩類似，底面罩用於電路板的反面。

環氧樹脂液體阻焊層

Epoxy resins are the cheapest alternative to welding masks. Epoxy is a polymer that is screen printed on a PCB. 絲網印刷是一種使用織物網來支撐油墨阻擋圖案的印刷工藝。 The grid allows identification of open areas for ink transfer. In the final step of the process, heat curing is used.

液體光學成像阻焊層

液體光導掩模，也稱為LPI，實際上是兩種不同液體的混合物。 Liquid components are mixed prior to application to ensure a longer shelf life. It is also one of the more economical of the four different PCB solder resistance types.

LPI 可用於絲網印刷、絲網噴漆或噴塗應用。 The mask is a mixture of different solvents and polymers. 結果，可以提取粘附到目標區域表面的薄塗層。 該掩模用於焊接掩模，但 PCB 不需要任何當今常見的最終電鍍塗層。

與舊的環氧樹脂油墨相比，LPI 對紫外線很敏感。 面板需要用面罩覆蓋。 經過短暫的“固化週期”後，電路板會使用光刻或紫外激光暴露在紫外光下。

Before applying the mask, the panel should be cleaned and free of oxidization. 這是在特殊化學溶液的幫助下完成的。 這也可以使用氧化鋁溶液或用懸浮的浮石擦洗面板來完成。

One of the most common ways to expose panel surfaces to UV is by using contact printers and film tools. The top and bottom sheets of the film are printed with an emulsion to block the area to be welded. Use the tools on the printer to fix the production panel and film in place. The panels were then simultaneously exposed to an ULTRAVIOLET light source.

另一種技術使用激光來創建直接圖像。 But in this technique, no film or tools are needed because the laser is controlled using a reference mark on the panel’s copper template.

LPI 遮罩有多種顏色可供選擇，包括綠色（啞光或半光）、白色、藍色、紅色、黃色、黑色等。 LED 行業和電子行業中的激光應用正在鼓勵製造商和設計師開發更強的白色和黑色材料。

乾膜光成像阻焊層

A dry film photoimagable welding mask is used, and vacuum lamination is used. 然後對乾膜進行曝光和顯影。 After the film is developed, openings are positioned to produce patterns. 在此之後，元件被焊接到釬焊墊上。 然後使用電化學工藝將銅層壓到電路板上。

銅在孔中和走線區域中分層。 錫最終被用來幫助保護銅電路。 In the final step, the membrane is removed and the etching mark is exposed. 該方法還使用熱固化。

Dry film welding masks are commonly used for high-density patch boards. 結果，它不會倒入通孔中。 These are some of the positives of using a dry film welding mask.

決定使用哪種焊接面罩取決於多種因素——包括 PCB 的物理尺寸、要使用的最終應用、孔、要使用的組件、導體、表面佈局等。

大多數現代 PCB 設計都可以獲得可光成像的阻焊膜。 Therefore, it is either LPI or dry film resistance film. The surface layout of the board will help you determine your final choice. If the surface topography is not uniform, the LPI mask is preferred. If a dry film is used on uneven terrain, gas may be trapped in the space formed between the film and the surface. Therefore, LPI is more suitable here.

但是，使用 LPI 也有缺點。 Its comprehensiveness is not uniform. You can also get different finishes on the mask layer, each with its own application. For example, in cases where solder reflow is used, the matte finish will reduce solder balls.

Build solder masks into your design

在您的設計中加入阻焊膜對於確保掩模應用處於最佳水平是必不可少的。 When designing a circuit board, the welding mask should have its own layer in the Gerber file. In general, it is recommended to use a 2mm border around the function in case the mask is not fully centered. 您還應該在焊盤之間留出至少 8 毫米的距離，以確保不會形成橋接。

Thickness of welding mask

Thickness Welding mask will depend on the thickness of the copper trace on the board. 一般來說，最好使用 0.5mm 的焊接面罩來掩蓋走線。 If you are using liquid masks, you must have different thicknesses for different features. 空層壓板區域的厚度可能為 0.8-1.2 毫米，而具有復雜特徵（例如膝蓋）的區域將具有較薄的延伸部分（約 0.3 毫米）。

結論

總之，焊接面罩設計對應用功能有嚴重影響。 它在防止鏽蝕和焊接橋樑方面起著至關重要的作用，這會導致短路。 因此，您的決定需要考慮本文中提到的不同因素。 希望這篇文章可以幫助您更好地了解PCB電阻膜的TYPE。 如果您有任何問題，或者只是需要聯繫我們，我們隨時樂意為您提供幫助。