隨著電子和電信工程領域的快速發展,需要技術創新, 工程師和科學家一直在尋找提高品質的新方法, 最終產品的生命週期和可靠性. 出於這個原因, 柔性PCB資料是當前研究的重點. Flexible PCB circuit boards can be found in almost all electronic devices around us (such as printers, 掃描儀, 高清監視器, 行动电话, 小算盘, 等.). 因此, 研究 柔性PCB 資料和制造技術的改進可以最大限度地降低生產成本,提高品質和可靠性. 最終產品. 在本文中, 我們將分析 flexible PCB製造 process.
的内容 柔性PCB:
We know that 柔性PCBs容易彎曲,可以安裝微電子元件. 它也是非常輕和超薄的, 囙此,它可以安裝在為主題電子產品或最終產品設計的任何小隔間或外殼中. 柔性印刷電路板最適合需要解决外殼空間限制的應用.
常用基板資料類型 柔性PCBs:
Matrix:
The most important 材料 in a 柔性PCB 或a 剛性印製板 是其基底資料. 它是整個PCB所用的資料. 在裡面 剛性印製板, 基材通常為FR-4. 然而, in-Flex PCB, the commonly used 基底 材料 are polyimide (PI) film and PET (polyester) film. 此外, polymer films such as 筆 (polyethylene phthalate) can also be used. Diester), PTFE和芳綸等.
Polyimide (PI) "thermosetting resin" is still the most commonly used 材料 for Flex PCB. 具有優异的抗拉强度, 在-200 oC至300 oC的寬工作溫度範圍內非常穩定, 具有耐化學性, 優异的電力效能, 高耐久性和優异的耐熱性. 與其他熱固性樹脂不同, 即使在熱聚合後也能保持彈性. 然而, PI樹脂的缺點是撕裂强度差和吸濕率高. 另一方面, PET (polyester) resin has poor heat resistance, “使其不適合直接焊接”, 但它具有良好的電力和機械效能. 另一基板, PEN, 具有比PET更好的中級效能, 但不比PI好.
Liquid crystal polymer (LCP) substrate:
LCP is a rapidly popular substrate 材料 in Flex PCB. 這是因為它克服了PI基板的缺點,同時保持了PI的所有特性. LCP具有防潮性,防潮性為%, 1 GHz下的介電常數為. 這使得它在高速數位電路和 高頻射頻電路板. LCP的熔融形式稱為TLCP, 可注塑成型並壓入 柔性PCB基板, 而且很容易回收.
Resin:
Another 材料 is a resin that tightly bonds the copper foil and the base 材料. 樹脂可以是PI樹脂, PET樹脂, 改性環氧樹脂和丙烯酸樹脂. 樹脂, copper foil (top and bottom) and substrate form a sandwich called "laminate". This laminate is called FCCL (Flexible Copper Clad Laminate) and is formed by applying high temperature and high pressure to the "stack" through automatic pressing in a controlled environment. 在提到的樹脂類型中, modified epoxy resins and acrylic resins have strong adhesion properties
These adhesive resins are detrimental to the electrical and thermal properties of Flex PCB and reduce dimensional stability. These adhesives may also contain halogens that are harmful to the environment and are restricted by European Union (EU) regulations. 根據這些環境保護法規, 限制使用7種有害物質, including lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (Cr 6+), polybrominated biphenyls (PBB), polybrominated diphenyl ethers (PBDE), Bis(2-ethylhexyl) phthalate (DEHP) and butyl benzyl phthalate (BBP).
因此, 解决此問題的方法是使用不含粘合劑的2層FCCL. 2L FCCL具有良好的電力效能, 高耐熱性和良好的尺寸穩定性, 但其製造難度大、成本高.
Copper foil:
Another top 材料 in 柔性PCBs是銅. PCB跟踪, 踪迹, 墊, 通孔和孔填充銅作為導電資料. 我們都知道銅的導電效能, 但如何在PCB上列印這些銅痕迹仍然是一個討論的話題. There are two copper deposition methods on the 2L-FCCL (2-layer flexible copper clad laminate) substrate. 1-電鍍2-層壓. 電鍍法的粘合劑較少, 而層壓板含有粘合劑.
plating:
In the case where an 超薄柔性PCB 是必需的, 通過樹脂粘合劑在PI基板上層壓銅箔的傳統方法不適用. 這是因為層壓工藝具有3層結構, 那就是, (Cu-Adhesive-PI) makes the stacked layer thicker, 囙此,不建議使用雙面FCCL. 因此, 使用另一種稱為“濺射”的方法, 其中,通過“無電”電鍍,通過濕法或幹法在PI層上濺射銅. This electroless plating deposits a very thin copper layer (seed layer), 在下一個叫做“電鍍”的步驟中,再沉積一層銅, where a thicker copper layer is deposited on the thin copper layer (seed layer) Layer). 該方法不需要使用樹脂粘合劑在PI和銅之間形成牢固的粘合.
laminated:
In this method, PI基板通過覆蓋層與超薄銅箔層壓. Coverlay是一種複合膜,其中熱固性環氧粘合劑塗覆在聚醯亞胺膜上. 這種覆蓋膠具有優异的耐熱性和良好的電絕緣體, 帶折彎, 阻燃劑和空隙填充特性. The special type of cover layer is called "Photo Imageable Coverlay (PIC)", 具有優异的附著力, 良好的靈活性和環保性. 然而, the disadvantages of PIC are poor heat resistance and low glass transition temperature (Tg)
Roll annealing (RA) and electrodeposition (ED) copper foil:
The main difference between the two lies in their 制造技術. 用硫酸銅溶液電解法製備ED銅箔, in which Cu2+ is immersed in a rotating cathode roll and peeled off, 然後製作ED銅. The RA copper with different thicknesses is made of high-purity copper (>%) through a press process.
Electrodeposited (ED) copper has better conductivity than roll annealed (RA) copper, RA的延展性比ED好得多. 對於 柔性PCB板, 就靈活性而言,RA是更好的選擇, ED是導電性更好的選擇.