201247904 六、發明說明： 【發明所屬之技術領域】 本發明係有關於銀基合金線材，且特別是有關於一種 電子封裝打線接合之高可靠度的合金線材。 【先前技術】 一般半導體及發光二極體（LED)之電子產品為了確 保使用壽命，均要求良好的可靠度，而車用電子產品對可 靠度的要求尤其嚴苛。以電動車的應用為例，電動車馬達 控制單元的變頻器（Inverter)是將電池的電能轉換成車輛動 能最重要元件，其最關鍵的絕緣閘雙極電晶體（Insulated Gate Bipolar Transistor ; IGBT)功率模組(power module)所 承受的電壓與電流遠高於一般功率元件及消費性電子產 品。另外，如高鐵、火車、捷運、工具機、廠房設備、船 舶、電廠等也同樣需要使用高電壓大電流功率元件。針對 這些高電壓大電流電子產品，其封裝打線接合需要可靠度 更南的鲜線材料。 封裝打線接合線材除了提供晶片與基板之訊號與功率 傳輸，亦可兼具散熱功能，因此作為打線接合的金屬線材 必須有極佳的導電性與導熱性，並且需要有足夠的強度與 延展性。但為了避免打線接合之熱壓過程導致晶片破裂， 同時使線材與銲墊接觸良好以確保良好的接合性，線材的 硬度不能太高。此外，由於封裝之高分子封膠常含有腐蝕 性氯離子，且高分子封膠本身具環境吸濕性，線材必須有 良好的抗氧化性與耐腐蝕性。 4 201247904 另外’打線接合的第一接點（銲球點）從溶融狀態冷 卻至室溫過程會有高熱量經由線材傳出，因而在銲球點附 近的線材產生熱影響區（Heat Affected Zone)，亦即此區域 的線材將因為熱量堆積而發生晶粒成長現象，產生局部的 粗大晶粒，這些局部的粗大晶粒強度較低，導致拉線試驗 (Wire Pull Test)時，線材會由此熱影響區斷裂而影響接合強 度0 、當半導體或發光二極體封裝完成，產品在使用過程， 通過線材的高電流密度也可能帶動内部原子產生電遷移現 象（Electron Migration)，使得線材一端形成孔洞，因而 降低導電性與導熱性，甚至造成斷線及產品失效；通電流 部燒溶’使電壓急速上升，最後同樣 此問題對於高電壓大電流電子產品 的封裝尤其嚴重，是影響這些電子產品可靠度的主要因素。 目前常見的封料線，例如包括下列幾種選擇： 接八界二，可具有低電p且率，但是金線與铭墊打線 =界面會大i的形成脆性介金屬化合物(包括_ ΑιιΑ14、入115入12等），使得導電 金屬反應會伴隨產生許多柯肯低。此外’金/銘界面介 加提高接合界面電阻率，而2孔洞(K—)，更 ⑺銅線：近年來，封裝產^點的可靠度降低。 及發光二極體打線接合的㈣#開始採賴線作為半導體 性，但卻很容易氧化，故在綠飼線雖具有較佳的導電 封保護，打線接合製程更需=存及運送過程均需要密 在後續封裝電子產品可靠卜/P責的氮氣加氫氣輔助，且 式驗仍然會遭遇氧化及腐蝕性 201247904 的問題。此外，銅線材質太硬，打線接合容易造成晶片破 裂等問題。_在-些研究巾提出在鱗表面鑛上其他金 屬鍍層以改善易氧化及腐钱問題的方法（例如參照美國專 利 US 7645522B2、US 2003/0173659Al、us 782〇9l3B2)， 但由於銅線本身硬度高，造成打線接合步驟易失敗，故仍 無法達到高電壓大電流電子產品封裝時所需的可靠度。 (3) 銀線：銀是在所有材料中電阻率最低的元素，但是 純銀在含硫的環境會有硫化腐蝕的問題，同時純銀線在鋁 墊上打線接合時也會生成脆性的介金屬化合物（Ag2A1或 Ag4Al)。此外，純銀線在含水氣的封裝材料内部很容易發 生電解離子遷移現象(Ion Migration)。亦即，純銀在含水氣 環境會經由電流作用水解溶出銀離子，再與氧反應成為不 穩定的氧化銀（AgO)，此氧化銀因而會進行去氧化作用 (Deoxidize)形成銀原子’並向正極成長出樹葉紋理狀〇eaf vein)的銀鬚，最後造成正負電極的短路（請參考：H.201247904 VI. Description of the Invention: TECHNICAL FIELD OF THE INVENTION The present invention relates to silver-based alloy wires, and more particularly to a highly reliable alloy wire for wire bonding of electronic packages. [Prior Art] Generally, electronic products of semiconductors and light-emitting diodes (LEDs) require good reliability in order to ensure the service life, and the reliability of automotive electronic products is particularly demanding. Taking the application of electric vehicles as an example, the inverter of the electric vehicle motor control unit is the most important component for converting the electric energy of the battery into the kinetic energy of the vehicle, and its most important insulated gate bipolar transistor (IGBT). The power module is subjected to voltages and currents much higher than those of general power components and consumer electronics. In addition, high-voltage, high-current power components are also required for high-speed rail, trains, MRT, machine tools, plant equipment, ships, and power plants. For these high-voltage, high-current electronic products, the package wire bonding requires a more reliable fresh wire material. In addition to providing signal and power transmission between the wafer and the substrate, the package wire bonding wire can also have a heat dissipation function. Therefore, the wire bonding wire must have excellent electrical and thermal conductivity and require sufficient strength and ductility. However, in order to avoid cracking of the wafer by the hot pressing process of wire bonding, and to make the wire and the pad in good contact to ensure good bonding, the hardness of the wire should not be too high. In addition, since the encapsulated polymer seal often contains corrosive chloride ions, and the polymer seal itself has environmental hygroscopicity, the wire must have good oxidation resistance and corrosion resistance. 4 201247904 In addition, the first contact (bump point) of the wire bonding is cooled from the molten state to the room temperature, and high heat is transmitted through the wire, so that the wire near the solder ball point generates a heat affected zone (Heat Affected Zone). That is, the wire in this area will grow due to heat accumulation, resulting in local coarse grains, which are low in strength, resulting in a wire pull test. The heat affected zone breaks and affects the joint strength. When the semiconductor or LED is packaged, the high current density of the wire may also cause the internal atom to generate electromigration (Electron Migration), which causes the wire to form a hole at one end. Therefore, the conductivity and thermal conductivity are reduced, and even the disconnection and product failure are caused; the current is burned and the voltage is rapidly increased. Finally, this problem is particularly serious for the packaging of high-voltage and high-current electronic products, which is affecting the reliability of these electronic products. The main factor of degree. At present, common sealing materials include the following options: Connected to the eight boundary two, which can have a low power p rate, but the gold wire and the Ming pad wire = the interface will be large i to form a brittle intermetallic compound (including _ ΑιιΑ 14, Into 115 into 12, etc., so that the conductive metal reaction will be accompanied by a lot of Kirken low. In addition, the 'Gold/Ming interface improves the joint interface resistivity, while the 2-hole (K-), and (7) copper wire: In recent years, the reliability of the package production point has decreased. And the light-emitting diode wire bonding (4) # began to use the line as a semiconductor, but it is easy to oxidize, so although the green feed line has better conductive seal protection, the wire bonding process needs to be stored and transported Condensed in the subsequent packaging of electronic products, reliable nitrogen / hydrogen, and the test will still encounter the problem of oxidation and corrosion 201247904. In addition, the copper wire material is too hard, and the wire bonding is liable to cause problems such as cracking of the wafer. _In some research papers, other metal coatings on scale surface minerals are proposed to improve the problem of oxidative and rotten money (for example, refer to US Pat. No. 7,645,522 B2, US 2003/0173659 Al, us 782 〇 9l3B2), but due to the hardness of the copper wire itself High, causing the wire bonding step to fail easily, so the reliability required for high voltage and high current electronic product packaging cannot be achieved. (3) Silver wire: Silver is the lowest resistivity element in all materials, but pure silver has the problem of vulcanization corrosion in a sulfur-containing environment, and a pure silver wire also forms a brittle intermetallic compound when it is wire bonded on an aluminum pad ( Ag2A1 or Ag4Al). In addition, the pure silver wire is prone to Ion Migration inside the aqueous gas encapsulating material. That is, pure silver will hydrolyze and dissolve silver ions in an aqueous gas environment, and then react with oxygen to become unstable silver oxide (AgO), which will deoxidize to form silver atoms and conduct to the positive electrode. The silver whiskers of the leaf texture 〇eaf vein are grown, and finally the short circuit of the positive and negative electrodes is caused (please refer to: H.
Tsutomu, Metal Migration on Electric Circuit Boards, Three Bond Technical News, Dec. 1, 1986.)。此外，在一些研究 中提出在銀線表面鍍上其他金屬鍍層以改善硫化腐蝕及銀 離子遷移的問題的方法（例如參照美國專利US 6696756)， 但所形成的線材仍無法達到理想的可靠度及電阻率。 (4) 合金線：合金線例如包括以金為主的合金以及以銀 為主的合金。這些合金例如更包括銅、鉑、錳、鉻、鈣、 銦等元素，然而這些合金線仍然無法同時兼具低阻抗及高 可靠度的性質。 綜上所述，現有的各種純金屬線材、表面鍵金屬的複 6 201247904 合線材、以及添加元素的合金線材都無法滿足高電壓大電 流電子產品封裝的需求，因此，目前亟需一種具高可靠度 的線材。 【發明内容】 在本發明實施例中，提供一種銀基合金線材，其係至 少由銀、纪、錯及始所形成之合金線材，其中該合金線材 中銀：鈀的重量比=90〜99.99 : 0.01〜10， 且鍺的含量在 1500ppm以下，翻的含量在350ppm以下，且該合金線材 包括一中心部分及一外圍部分，且該中心部分具有長條形 晶粒或等轴晶粒，該外圍部分具有等轴晶粒，且在該合金 線材中具有退火孿晶結構(annealing twins structure)的晶粒 數量佔該合金線材的所有晶粒數量的20%以上。 在本發明另一實施例中，提供一種銀基合金線材的製 造方法，包括：提供一粗線材，該粗線材係至少由銀、鈀、 鍺及鉑所形成之合金線材其中該合金線材中銀：鈀的重量 比=90〜99.99 : 0.01〜10，且錯的含量在1500ppm以下，翻 的含量在350ppm以下；以及交替進行複數道冷加工成形 步驟及複數道退火步驟，以逐次縮減該粗線材的線徑而形 成一細線材，其中，該些冷加工成形步驟及該些退火步驟 至少包括下列步驟：進行倒數第二道冷加工成形步驟；之 後，進行倒數第二道退火步驟，該倒數第二道退火步驟的 退火溫度為〇.5Tm〜0.7Tm，退火時間為1〜5秒，其中，Tm 為該粗線材的材質的絕對溫標的熔點；之後，進行最後一 道冷加工成形步驟，使得該最後一道冷加工成形步驟所形 201247904 第:：=形步驟所形成_之 秒。 ‘ 、U火，皿度鬲20°C〜10〇°C，退火時間為2〜30 顯易i讓他目的、特徵、和優點能更明 細說明如下：+出較佳霄施例’並配合所附圖式，作詳 【實施方式】 發明本發明之不同特徵舉出數個不同的實施例。本 -二=的元件及安排係為了簡化，但本發明並不以這 描包括Γ舉:而言，於第二元件上形成第-元件的 括具與第二元件直接接觸的實施例，亦包 第-响第二元件之間、使得 明起見，本發明在不同施例。此外，為簡 代表所述各實施例及::二:字： 由合種銀基合金騎及其形成方法，除了藉 良，使線材的可靠度可大幅提升。 财饤改 2發明一實施例，，銀基合金線材係 =添加卿叙合金線材，該合金 ^ 〜部分及-外圍部分’且該中心部分具有長條形^粒或 8 201247904 蓉鱼!fe曰斗九 ’該外圍部分具有等軸晶粒，且在該合金線材中 、 辛日日結構（annealing twins structure)的晶粒數量佔 該合金線材的所有晶粒數量的20%以上。 七4知的合金線大多仍含有一定量的金元素，這些 金原子在封裝打線接合時會與鋁墊形成介金屬化合物，造 成接合界面脆裂，並伴隨著產生許多柯肯達孔洞 (Kirkendall holes) ’導致封裝產品接點的可靠度降低。因 此，在本發明一較佳實施例中，合金線材以銀（Ag)為主成 分，並完全避免添加金（Au)元素，故可避免脆性金鋁介金 屬化合物的形成而提升合金線材的可靠度。此外，大量的 退火孿晶結構可提升材料強度，故可提升可靠度。 第1圖顯示在本發明一實施例中之銀基合金線材的形 成方法的流程圖。參照第1圖，在步驟102中，提供一粗 線材，該粗線材係至少由銀、鈀、鍺及鉑所形成之合金線 材。在步驟104中，交替進行複數道冷加工成形步驟及複 數道退火步驟，以逐次縮減該粗線材的線徑，以形成—細 線材。上述步驟的詳細方法敘述如下。 參照步驟102,提供一粗線材，該粗線材係至少由 把、錯及賴形成之合金線材。銀、㉟、鍺及麵禮: 因為這四種元素在相平衡圖上可以完全互相固溶（疋 Solution) ’不會產生任何脆性的介金屬相析出物 ㈣ 成的合金線材可具有較佳的延展性，聽、錯及^所形 也不會對電阻率有太大的影響。 t添加 經實驗發現，適量㈣可㈣效提升銀線 及抗硫化腐減力，同時由於其擴散速輪低 ^化 久表面生 9 201247904 成物的阻隔性，可以避免銀的離子遷移問題。此外，其對 於銀與鋁墊的界面介金屬反應也有抑制效果。然而，當鈀 的含量過高時，則會造成合金線材的電阻升高。此外，適 量的鍺（Ge)可以有效提升線材的抗氧化及硫化性，同時可 以提高銲點的接合強度，但是鍺的含量過高時，則會使線 材延展性降低。另外，適量的鉑（Pt)可增強線材的抗氧化、 硫化性及氯離子腐蝕性，並對於銀的離子遷移現象亦有明 顯抑制效應，同時也減少銀合金線與鋁墊形成介金屬化合 物，然而當鉑的含量過高時，則會使線材的電阻率明顯提 高。 在一實施例中，粗線材中銀為主要成份，並添加把、 錯、I自，其中把的含量約為0.01〜l〇wt%;錯含量在1500 ppm 以下，較佳介於10 ppm〜1500 ppm ;翻含量在350 ppm以 下，較佳介於5 ppm〜350 ppm ;且銀、I巴、鍺、翻的含量 和為100wt%(例如，銀的含量約為90〜99.99wt%)。在另一 實施例中，合金線材更包括棚，且删的含量在20 ppm以 下，較佳介於1 ppm~ 20 ppm。在此實施例中，銀、絶、錯、 鉑、硼的含量和為100wt%。適量的硼可以在銀合金產生晶 界偏析（Grain Boundary Segregation)，一般雜質元素在材料 晶界偏析大多會造成材料沿晶脆斷’但棚的晶界偏析不但 不會引起晶界脆化，反而扮演晶界強化的有益角色，可以 明顯提升線材的延展性及抗疲勞性。然而，棚的的含量過 高時，仍會造成晶粒内部的脆化。在其他實施例中，上述 粗線材也可包括其他元素，但應避免所添加的元素與銀形 成介金屬相的析出物，造成材質脆化、腐蝕性提高、或導 10 201247904 電性降低等問題。因此，所添加的元素較佳可以銀原子完 全互溶而不會有析出物的形成，以確保線材的延展性。 應注意的是，在其他例子中，合金線材可更包括其他 金屬、非金屬元素、或其他雜質成分，本發明並不限定為 銀-鈀-鍺-鉑的四元合金或銀-鈀-鍺-鉑-硼的五元合金。因 此，只要控制粗線材中銀：鈀的重量比=90〜99.99 : 0.01〜10，且銀為此粗線材的主要成份，且鈀、鍺、鉑、硼 或其他成份的含量不大於銀的含量即在本發明之範嘴内。 此外，由於在實際冶煉、精煉、冷加工成形等的過程中， 難以完全除去所有雜質而準確達成數學上或理論上的特定 濃度，因此當上述雜質含量的範圍落於對應的標準或規格 所訂定的允收範圍内，仍視為在本發明的範疇之内。本發 明所屬技術領域中具有通常知識者應當瞭解依據不同的性 質、條件、需求等等，上述對應的標準或規格會有所不同， 故下文中並未列出特定的標準或規格。 在一實施例中，粗線材的形成方法係將銀、鈀、鍺及 鉑加熱熔融後，經澆鑄而成為鑄錠。而後，對鑄錠進行冷 加工，以形成上述至少由銀、鈀、鍺及鉑所形成之粗線材。 在另一實施例中，則是將銀、鈀、鍺及鉑加熱熔融後，以 連續鑄造的方式形成上述粗線材。在一實施例中，粗線材 的線徑約為5~10 mm。 參照步驟104,交替進行複數道冷加工成形步驟及複數 道退火步驟，以逐次縮減該粗線材的線徑。第2圖則顯示 步驟104所述複數道冷加工成形步驟及退火步驟更詳細的 步驟。在第2圖中，步驟104所述的複數道冷加工成形步 201247904 驟及退火步驟至少包括下列步驟：在 第一道冷加工成形步驟，該第—道々力，104_1中，進行 的線材之間的變形量為·以±、=工成形步驟所形成 104-2中，進行第—道退火 超^0%。。在步驟 溫度為m，退火時間為 的冷加工成形步驟及退火步^視需步要驟重-二及购 次。而後，在步驟1〇4_3中，進 稷父替進仃數 步驟。在步驟104_4中，進行倒數第加工成形 數第二道退火步驟的退火溫度為步驟\該倒 :1:5 #，其中’ Tm為該粗線材的材質的:對 得該最:驟、:04-”，進行最後一道冷加工成形;二使 道二加1成形步驟所形成的線材與該倒數第二 上:::::㈣所形成的線材之間的變形量為1%: 不超過15%。上述變形量係指因冷加工成形步驟而對 進：!：：的材料所造成的截面積縮減率。在步驟购中， =後-道退火步驟’該最後一道退火步驟的退火溫产 門^第二道退火步驟的退火溫度高2〇t~UKTC，退火$ 2〜30秒。應注意的是，在一實施例中，步驟⑽也可 步驟驟（步驟1〇4-3、1〇4_5)及二道退火 在貝細例中，上述冷加工成形步驟包括抽線、擠型 =則述之組合。或者，上述冷加王成形步驟及退火步驟可 二、任何已知或未來發展的冷加工/退火方式。 在上述冷加工成形及退火步驟後所形成的細線材為至 12 201247904 少由銀、鈀、鍺及鉑所形成之合金線材，其中，該合金線 材包括一中心部分及一外圍部分，且該中心部分具有長條 形晶粒或等軸晶粒，該外圍部分具有等軸晶粒，且在該細 線材中具有退火孿晶結構（annealing twins structure)的晶粒 數量佔該細線材的所有晶粒數量的20%以上。在一實施例 中，細線材的線徑為10〜50 μιη。相較於傳統的金屬線材， 上述細線材可具有較佳的可靠度。 上述退火孿晶結構的形成原因可根據物理冶金學原理 推論（請參考 George E. Dieter, Mechanical Metallurgy, McGRAW-HILL Book Company, 1976, P. 135-141.及 R.W. Cahn, Physical Metallurgy, 1970, P.l 184-1185 )。退火孿晶 結構的形成是由於在冷加工製程時在材料内部累積應變能 (strain)，這些應變能在後續退火熱處理時會驅動部分區域 之原子均勻剪移（Shear)至與其所在晶粒内部未剪移原子 形成相互鏡面對稱之晶格位置，此即為退火孿晶（Anneaiing Twin)，而其相互對稱之界面即為孿晶界（Twin Boundary)。退火孿晶主要發生在晶格排列最緊密之面心 立方（Face Centered Cubic ; FCC)結晶材料，其孿晶界為 低能量之Σ 3特殊晶界，結晶方位均為丨1丨1丨面。相較於 一般退火再結晶（Recrystallization )所形成高角度晶界 (High Angle Grain Boundary )，孿晶界的界面能大約只有 高角度晶界的5%。此外，一般而言，疊差能（StackingFauh Energy)愈小的材料愈容易產生退火孿晶，而合金線材的 主要成伤銀、把的疊差能均大約在5〇 erg/cm2以下，故容 易形成退火孿晶。亦即，並非所有金屬都能輕易形成孿晶 13 201247904 結構。例如，鋁雖為面心立方結晶構造材料，但其疊差能 大約200 erg/cm2，故極少出現退火孿晶。 此外，第2圖所述的冷加工成形步驟也為退火孿晶結 構形成的因素之一。足夠的冷加工變形量所累積應變能可 提供原子驅動力以產生退火孿晶，但如果冷加工變形量太 大’在退火熱處理初始再結晶（Primary Recrystallization) 階段即會引發多數晶粒成核（Nuclei of Recrystallized Grains )，因而形成大量的微細晶粒，降低退火孿晶的產 生機會。應注意的是，第2圖所述形成合金線材的方法僅 為本發明一較佳實施例，然而本發明之合金線材的形成方 法並非以此為限。 第3A、3B圖顯示本發明一實施例所形成之銀基合金 線材300。第3A圖顯示銀基合金線材300的一部分的線段 的示意圖。第3B圖顯示沿著平行於第3A圖所示合金線材 3〇〇的長度方向的縱切面圖。 參照第3A圖，銀基合金線材300為主成分銀至少添加 絶、鍺、鉑所形成的合金線材。參照第3B圖，合金線材 3〇〇的縱切面為面心立方（face-centered cubic)晶相的多晶 結構(polycrystalline structure) ’且整體皆為等軸晶粒302。 此外，各晶粒之間是以向角度晶界304為界，其中具有退 火孿晶結構（annealing twins structure)306的晶粒的數量， 是佔此銀基合金線材300的所有晶粒數量的20%以上。在 —較佳實施例中，退火孿晶結構的晶粒的數量佔合金線材 的所有晶粒數量的30%至60%，其中’等軸晶粒302的尺 寸例如介於Ο.ίμιη至6μηι ’其長徑比介於1至2。在第 14 201247904 3C圖中’合金線材雖大體仍為等轴晶粒搬，但其中心部 分更包括長條形絲。其中，長條形晶粒的長徑比大 於2上这中〜部位係指從線材的軸心起算沿著線材半徑 方向的3 G %的線材半徑值的範_的部位。 一在-實施例中，合金線材3〇〇中銀：鈀的重量比 ，〜99.99 : 0.01〜10 ’鍺含量在·啊以下，較佳介於 U) ppm〜· Ppm。銘含量在35()啊以下，較、 ppm〜350 ppm。其中，銀為此合金線材3〇〇的主要严，$ 鈀、鍺、鉑或其他成份的含量不大於銀的含量。在另:， 施例中，合金線材更包括硼，且硼的含量在2〇ρριη以^實 較佳介於1 ppm〜20 ppm。上述合金之優點例如包括下】， 未添加金，故可避免金鋁界面介金屬脆裂；2.添如鈀以. 善銀合金線材的抗腐蝕及離子遷移破壞，並且抑制報合改 線與鋁墊的界面介金屬反應；3·添加鍺以增強銀合金線/ 的抗氧化及疏化性，同時提高銲點的接合強度；4添加= 以增強線材的抗氧化、硫化性及氯離子腐蝕性，同^和鉑 銀的離子邊移現象及銀/鋁界面介金屬反應；5.添加硼=制 化合金晶界，提升線材的延展性及抗疲勞性。 乂強 然而，應注意的是，上述銀基合金線材雖以銀為主 成分並包含特定比例的I巴、鍺、翻、删，然而本發明之2 _並非以此為限。在其他例子中，銀基合金線材可更勺= 其他金屬、非金屬凡素、或其他不可避免的雜質成分。廊 >主意的是，其他金屬it素的添加需視應用上的需要調整〜 以避免影響合金線材的性質。例如，在上述合金線^中加 入銅時，固然會產生材質強化效應，但是銅元素會使人= 15 201247904 ::“硫化腐蝕性能大幅降低，而且由於銀_銅合 金㈢在日日，生不連續析出物，而造成斷線。此外，銅也 會使σ金=更^增向變脆’使得抽線製程困難，同時在打 線接合過程也谷易造成晶片擊穿。 另：加稀土元素可以使合金的晶粒細化，但 =於封ϋ接合的線材應用需求’細晶粒有較多晶界， 1晶界會阻，電子傳輸’使合金電阻率提高，故不適用 於而速運作及r%頻積體電路電子產品之封裝需求。此外， 稀土的化學活性會提高其氧化及靠破壞，使得封裝線材 在通電=時較容易_ ’而不利於電子產品的可靠度。再 者’在合金中添加舞會使材料延展性變差；在合金中添加 低炼=的銦或锡會形成m使線材《溫性變差，持續 通電流容易造成線材融斷；添加鈹(Be)為具毒性之易燃性 固體乾燥叔塵或煙霧都是有毒的；添力口釘⑽）、錢⑽）、 餓(〇S)、銀(ΐΓ)時，其熔點（分別為 2310〇C、1965。0 3045°C 和2410°C)均遠高於銀的沸點（2212〇c)，因此其熔煉極為困 難’且會大幅增加電阻率。又，部分添加元素在相平衡圖 上曰與銀幵/成j丨金屬相的析出物(precipitati〇n)，而造成材 質的脆化及較高腐蝕性，更會降低線材的導電性。 相幸父於傳統的線材’本發明各種實施例中之合金線材 例如可具有下列優點，包括： ⑴電阻低： 雖然銀具有較低的電阻率，但在傳統製程中之銀線材 之晶粒係微細晶粒（平均粒徑約為0 5〜2 μΠΐ)，故具有大量 高角度晶界’因而造成電阻率提高。此外，銀線材在鋁墊 201247904 上打線接合時會生成脆性的介金屬化合物（鋁化二銀 (Ag2Al)或鋁化四銀(Ag4Al))，故會造成導電性降低。 而本發明之合金線材係包括大量的退火孿晶 (Annealing Twin )，退火孿晶組織的孿晶界（Twin Boundary)為調諧（Coherent)結晶構造，屬於低能量之Σ 3特殊晶界，其界面能僅為一般高角度晶界的5 %。因此這 些退火孿晶之對稱晶格排列對電子傳輸的阻礙極小，而能 展現較低的電阻率。 (2) 機械強度佳： 本發明各實施例中之合金線材中包括至少20%的晶粒 内部含有退火孿晶（Annealing Twin )組織，故可維持線材 較佳的機械強度。更進一步說明，由於孿晶結構與其所在 之晶粒具有不同結晶方位（Crystal Orientation)，因此可以p且 擔差排（Dislocation)的移動，而產生材料強化效應。藉 此可維持與一般微細晶粒結構線材相近之拉伸強度，但由 於差排及原子可經由孿晶界跨移（CrossSlip),其延展性 反而高於一般微細晶粒形成的線材。 (3) 具抗氧化、抗腐蝕能力： 一般而言，銀在含硫環境下常有硫化腐蝕的問題，故 會在銀上艘其他貴金屬以避免硫化。然而，責金屬在打 接合結球過程也會完全溶入熔融的銀銲球基材内，使得寺 線接合完成的球輝點成分僅是含微量保護性責金屬的銀二 金’因此打線接合料銲點仍會發生·腐㈣象，因: 仍無法有效避免銀電解離子遷移所造成球銲點短路現象， Μ及在銘塾打線接合時的柯肯達孔洞效應。 201247904 …、而’本發明各實施例中之合金線材中⑽I少2 ^ 的晶粒内部含有退火孿晶（AnnealingTwin) 一，由於: 晶界的較低的界面能’可以避免成為氧化、硫化及_ 腐姓的路輕，故能展現較佳的抗氧化性與耐腐餘性。 (4) 封裝過程中晶粒成長不易： 傳統的線材之微細晶粒結構經過打線接合後’錄球 凝固熱里在其附近線材累積，會使得其晶粒迅速成長而= 成熱影響區，因而降低拉線試驗強度。然而，本發明各實 施例之合金線材至少20%的晶粒内部含有退火孿晶 (Annealing Twin)組織，這些退火學晶（a議aiingTwin) 組織具有較低的界面能，結構較一般高角度晶界穩定。因 此，不僅在高溫狀態下孿晶界本身不易移動，更會對其所 在晶粒之周圍的高角度晶界產生固鎖作用，使這些高角产 晶界亦無法移動’因而整體晶粒組織不會有明心粒： 現象。故即使在打線接合過程中第一接點（銲球點'） 融狀態冷卻至室溫，也可以維持原有晶粒尺寸。此外 封裝產品在經歷各種高溫可靠度試驗時，也較不 田 粒不穩定成長。 導致晶 (5) 電子遷移率低： 在傳統製程中，純銀線材在含水氣的封裝材料内立/ 容易發生電解離子遷移現象(Ion Migration)，最後迕成^很 電極的短路。此外，純銀線與鋁墊打線接合時， 正負 ._ _ 由於報在 鋁原子基地(Matrix)的擴散係數較鋁原子在銀基地 么 1〇2至10。倍，此一界面擴散速度的巨大差異會造成所二约 柯肯達孔洞，導致電阻率升高及打線接合銲球失效。明的 18 201247904 而在本發明的合金線材中，由於原子經由低能量孿晶 界或跨越孿晶界的擴散速率極低，因此當應用於電子產品 時，即使在高密度電流下其線材内部原子也不易移動。 綜合上述優點，本發明之合金線材可以用於要求高可 靠性的高電壓大電流電子產品，尤其是功率元件的封裝打 線接合用的線材。當然，依使用者的需求，亦可將本發明 之合金線材應用於其他技術領域與用途，例如：音響線、 訊號或功率傳輸線、變壓器線等，而合金線材的線徑亦可 依據需求加以變化，而不限定為上述例示的範圍。 此外，經實驗發現，合金線材中至少20 %的晶粒含有 退火孿晶結構才可達到上述優點。因此，雖然在習知打線 接合用的金屬線材的製程中，或許偶有出現退火孿晶結構 的情況，但是含退火孿晶結構的晶粒數量通常為線材所有 的晶粒的10 %以下或甚至完全不含退火孿晶結構，故仍然 無法具有上述之優點。 本發明經過諸位發明人長久、精心的研究，利用特定 組成的合金元素並配合冷加工變形量與退火溫度時間的控 制，可形成内部含有大量退火孿晶的材料組織，獲得一種 可具低電阻率、高導熱性、高強度、高延展性、優良抗氧 化腐蝕性之封裝導線。更詳細而言，合金組成提供導電性 與機械性質的隶佳協調’拿晶界則具有可以有效抑制電遷 移現象、提升材料強度及延展性等特性，因此在進行打線 接合的封裝時，不僅具有極低的電阻率，且在可靠度試驗 時更展現極佳的成績。例如，在最嚴苛的壓力銷測試 19 201247904 (Pressure Cooker Test ; PCT)中，在溫度（Ta)=12rc、相 對溼度(RH)=100%、2大氣壓的條件下可耐受128小時以 上’遠高於一般電子產品可靠度測試所要求96小時。在另 一實施例中’在高度加速壽命試驗中（Highly Accelerated Stress Test，HAST ) ’ 在溫度（Ta)=148 °C、相對渔度 (RH)=90%、3.6伏特的偏壓的條件下可達到128小時以上， 也遠高於一般電子產品可靠度測試規範所要求96小時。因 此，在本發明各實施例中之合金線材可以應用於各種高速 電源交換積體電路中，例如輸入電壓範圍在4.5V至17V， 工作頻率1200KHZ的壓降型直流式電壓交換積體電路 (Buck DC/DC Converter)，而不限於應用在一般速度較慢的 500KHZ以下的壓降型直流式電壓交換積體電路。 【比較例1】具少量孿晶組織的合金線材 利用南週波電熱真空炫煉合金，其合金組成為 Ag-8wt%Au-3wt%Pd-0.005wt.%La。將上述合金以連續鑄造 方式獲得線徑6 mm之粗線材。進行8次冷加工成形步驟 抽線延伸與退火熱處理，以形成線徑25.4 μπι之細線材。 而後，進行倒數第二道冷加工成形步驟抽線延伸而成為線 徑22.6μιη之細線材，再經過600°C退火5秒。最後進行最 後一道冷加工成形步驟抽線形成17·5μιη之細線材，並進行 最後一道退火步驟，其退火溫度為700°C、退火時間為1〇 秒。完成最終退火步驟後，捲線完成打線接合所需要之合 金線材產品。 第4圖顯示此比較例1之合金線材的剖面圖，其中心 20 201247904 部位具有長條形晶粒及少數非常粗大的等軸晶粒，外圍則 具有微細的等轴晶粒，其晶粒尺寸大約1 // m，退火孿晶結 構大約只佔總晶粒數置的10 %。 將上述具少量退火孿晶結構之合金線材通過0.2A的 電流1200小時進行測試，結果如第5圖所示。參照第5圖， 比較例1的合金線材在通電流後，中心部位的長條形晶粒 消失，整體晶粒尺寸則大幅成長大約8/zm，且線材發生燒 溶現象。 【實施例1】具大量孿晶組織的合金線材 利用高週波電熱熔煉以銀為主要成份的合金，其成分 可參照表1。表1顯示合金中鈀、鍺、鉑、硼的含量，而 合金中的其他成分則為銀。亦即，銀的含量及表1中鈀、 鍺、鉑、硼的含量總合達到100wt%。將上述合金以連續鑄 造方式獲得線徑6 mm之粗線材。進行12次冷加工成形步 驟抽線延伸與退火熱處理，以形成線徑22.6 μπι之細線材。 而後，進行倒數第二道冷加工成形步驟抽線延伸而成為線 徑20μιη之細線材，再經過530°C退火2秒。最後進行最後 一道冷加工成形步驟抽線形成17.5 μπι之細線材，並進行最 後一道退火步驟，其退火溫度為600°C、退火時間為15秒。 完成最終退火步驟後，捲線完成打線接合所需要之合金線 材產品。 201247904 表1 ίε 鍺 舶 (wt%) (wtppm) (wtppm) (wtppm) 組成1 1.00 50 50 … 組成2 1.00 50 250 … 組成3 1.00 50 350 … 組成4 2.00 500 50 … 組成5 1.00 500 250 — 組成6 1.00 500 350 … 組成7 1.00 1500 50 … 組成8 1.00 1500 250 — 組成9 2.00 1500 350 … 組成10 3.20 50 50 …· 組成11 3.20 50 250 組成12 3.20 50 350 組成13 3.20 500 50 組成14 3.20 500 250 --- 組成15 3.20 500 350 … 組成16 3.20 1000 50 … 組成17 3.20 1000 250 … 組成18 3.20 1000 350 組成19 6.00 50 50 … 組成20 6.00 50 250 … 組成21 6.00 50 350 組成22 6.00 500 50 … 組成23 6.00 500 250 組成24 8.00 500 350 … 組成25 10.00 1000 50 組成26 10.00 1000 250 — 組成27 10.00 1000 350 … 組成28 3.00 50 50 20 組成29 6.00 50 150 15 組成30 10.00 50 50 10 第6圖顯示在實施例1所列表1各種組成銀基合金線 材中組成 10 之 Ag-3.2wt.%Pd-50ppmGe-50ppmPt 合金線材 的剖面圖，其中心部位具有長條形晶粒，外圍的等軸晶粒 尺寸大約4 μ m，大於比較例1合金線材的外圍等軸晶粒。 如第6圖所示，實施例1之合金線材有超過總晶粒數量30 22 201247904 %的晶粒具有退火孿晶結構。 將上述合金線材通過〇.2A的電流i小 試，結果如第7圖所示。參照第7圖，實施例i中^丁柳 的合金線材在通電流後，中，位的成ίο 圍的等軸晶粒僅略微成長，且線材未發线熔現^料外 比較例1之第5圖）。 、對照 可靠度測試： 另外’利用實施例1中組成10之合金線材進 合以形成高速電源交換器產品，並對此高速電源交換， 品進行一系列可靠度試驗，其結果綜合示於表2，其 嚴苛的壓力锅測試（Pressure Cooker Test PCT)會^ 喪 受12δ小時以上，遠高於一般電子產品可靠度測試所寸 96小時，另一同樣嚴苛的高加速壽命試驗（ Accelerated Stress Test，HAST)實際可達到 128 小時以^ly 也遠高於一般電子產品可靠度測試規範所要求96小時。 表2 試驗項目 (TEST ITEM) 試驗條件 (TEST CONDITION) 1.前處理測試 (Precondition Test) 烘烤(125°C ; 24小時） 溫濕度測試(30°C ; 60°/〇RH ; 192小 時）； 重流(Reflow):260+0/-5 °C ; 3 次 2.壓力鍋測試 (Pressure Cooker Test ； PCT) Ta=121°C ; 100%RH ; 2 大氣壓； 96小時 3溫度循環測試 (Temperature Cycling Test ； TCT) Ta=-65 °C〜150°C(氣態溫度衝擊 (air to air)) ; 15 分鐘；1000 次循環 201247904 4.溫濕度測試 (Temperature&Humidity Test ； THT) Ta=85°C ; 85%RH;無偏壓；1000 小 時 通過 5.高溫儲存測試 (High Temperature Storage Test ； HTST) Ta=150°C ; 1000 小時 通過 6.低溫儲存測試 (Low Temperature Storage Test ； LTST) Ta=-40°C ; 1000 小時 通過 7.高度加速壽命試驗 (Highly Accelerated Stress Test ； HAST) Ta=148°C ; 90%RH ; 3.6 伏特的偏 壓；96小時 通過 8.冷熱衝擊測試 (Thermal shock Test ； TST) Ta=-65°C〜150°C ; 5 分鐘；1000 次循環 通過 表3則顯示在各實施例中不同金屬成分比例所形成的 合金線材的性質及可靠度測試結果。 表3 強度 (Rf) 電阻 (μΩαη) 壓力鍋測試 (168hr) 溫度循環測試 (lOOOCyc) 高溫儲存測試 (1000hr) 組成1 8.55 1.88 通過 通過 通過 組成2 8.76 1.90 通過 通過 通過 組成3 8.92 1.93 通過 通過 通過 組成4 8.62 1.89 通過 通過 通過 組成5 8.67 1.91 通過 通過 通過 組成6 8.73 1.95 通過 通過 通過 組成7 8.81 1.92 通過 通過 通過 組成8 8.87 1.96 通過 通過 通過 組成9 8.94 1.99 通過 通過 通過 組成10 9.47 2.76 通過 通過 通過 組成11 9.63 2.79 通過 通過 通過 組成12 9.87 2.81 通過 通過 通過 組成13 9.62 2.84 通過 通過 通過 組成14 9.83 2.87 通過 通過 通過 組成15 9.95 2.91 通過 通過 通過 組成16 9.71 2.88 通過 通過 通過 組成17 9.89 2.92 通過 通過 通過 24 201247904 組成18 10.11 2.97 通過 通過 通過 組成19 11.35 4.12 通過 通過 通過 組成20 11.49 4.15 通過 通過 通過 組成21 11.62 4.19 通過 通過 通過 組成22 11.57 4.20 通過 通過 通過 組成23 11.71 4.24 通過 通過 通過 組成24 11.92 4.27 通過 通過 通過 組成25 12.01 4.29 通過 通過 通過 組成26 12.53 4.31 通過 通過 通過 組成27 12.87 4.35 通過 通過 通過 組成28 8.52 1.74 通過 通過 通過 組成29 9.36 2.70 通過 通過 通過 組成30 11.42 4.10 通過 通過 通過 雖然本發明已以數個較佳實施例揭露如上，然其並非 用以限定本發明，任何所屬技術領域中具有通常知識者， 在不脫離本發明之精神和範圍内，當可作任意之更動與潤 飾，因此本發明之保護範圍當視後附之申請專利範圍所界 定者為準。 25 201247904 【圖式簡單說明】 第1圖顯示在本發明一實施例之銀基合金線材的形成 方法的流程圖。 第2圖顯示步驟104所述複數道冷加工成形步驟及退 火步驟更詳細的步驟。 第3A-3C圖顯示本發明一實施例所形成之銀基合金線 材。第3A圖顯示合金線材外觀，第3B圖顯示整體線材均 為等軸晶粒，第3C圖顯示線材的中心部位具有長條形晶 粒，外圍則具有等軸晶粒。 第4-5圖顯示本發明一比較例之合金線材。第4圖為 原先的合金線材，第5圖則顯示通電流試驗後的合金線材。 第6-7圖顯示本發明一實施例之合金線材。第6圖為 原先的合金線材，第7圖則顯示通電流試驗後的合金線材。 【主要元件符號說明】 3 00〜合金線材 302〜等軸晶粒 304〜南角度晶界 306〜退火孿晶結構 3 0 8〜長條形晶粒 26Tsutomu, Metal Migration on Electric Circuit Boards, Three Bond Technical News, Dec. 1, 1986.). In addition, in some studies, a method of plating other metal plating on the surface of the silver wire to improve the problem of sulfide corrosion and silver ion migration has been proposed (for example, refer to US Pat. No. 6,696,756), but the formed wire still cannot achieve the desired reliability and Resistivity. (4) Alloy wire: The alloy wire includes, for example, a gold-based alloy and a silver-based alloy. These alloys include, for example, elements such as copper, platinum, manganese, chromium, calcium, and indium. However, these alloy wires are still not capable of both low impedance and high reliability. In summary, the existing pure metal wire, surface bond metal composite 6 201247904 wire and alloy wire of added elements can not meet the needs of high voltage and high current electronic product packaging. Therefore, there is a need for high reliability. Degree of wire. SUMMARY OF THE INVENTION In an embodiment of the present invention, a silver-based alloy wire is provided, which is an alloy wire formed by at least silver, gyration, and error, wherein the weight ratio of silver:palladium in the alloy wire is 90 to 99.99: 0.01~10, and the content of bismuth is below 1500ppm, the content of tumbling is below 350ppm, and the alloy wire comprises a central portion and a peripheral portion, and the central portion has elongated grains or equiaxed grains, the periphery The portion has equiaxed grains, and the number of crystal grains having an annealing twins structure in the alloy wire accounts for more than 20% of the total number of grains of the alloy wire. In another embodiment of the present invention, there is provided a method of manufacturing a silver-based alloy wire, comprising: providing a thick wire material of an alloy wire formed of at least silver, palladium, rhodium, and platinum, wherein the alloy wire is silver: Palladium weight ratio = 90~99.99: 0.01~10, and the wrong content is below 1500ppm, the turning content is below 350ppm; and alternately performing multiple cold forming steps and multiple annealing steps to successively reduce the line of the thick wire Forming a thin wire, wherein the cold forming step and the annealing step comprise at least the following steps: performing a penultimate cold forming step; thereafter, performing a penultimate annealing step, the penultimate annealing step The annealing temperature is 〇5Tm~0.7Tm, and the annealing time is 1~5 seconds, wherein Tm is the melting point of the absolute temperature standard of the material of the thick wire; then, the last cold forming step is performed, so that the last cold forming step Formed 201247904 The ::== step formed by the _ seconds. ', U fire, the degree of 鬲 20 ° C ~ 10 〇 ° C, annealing time is 2 ~ 30 易易 i let his purpose, characteristics, and advantages can be more clearly explained as follows: + better than the example 'and cooperate BRIEF DESCRIPTION OF THE DRAWINGS [Embodiment] Various features of the invention are set forth in the various embodiments. The elements and arrangements of the present and the second are for the sake of simplicity, but the present invention does not include the following: in the embodiment, the embodiment in which the second element is directly in contact with the second element is also Between the first and second components of the package, the invention is described in different embodiments. In addition, for the sake of simplicity, the following embodiments and:: two: word: The method of riding a silver-based alloy and forming the same, in addition to borrowing, the reliability of the wire can be greatly improved. According to an embodiment of the invention, the silver-based alloy wire system = the addition of the Qingshi alloy wire, the alloy ^ ~ part and - the peripheral portion ' and the center portion has a long strip shape or 8 201247904 squid! The peripheral portion of the bucket has an equiaxed grain, and in the alloy wire, the number of grains of the annealing twins structure accounts for more than 20% of the total number of grains of the alloy wire. Most of the alloy wires of the 7th 4th still contain a certain amount of gold. These gold atoms will form a metal intermetallic compound with the aluminum pad during the bonding of the package wires, causing the interface to be brittle and accompanied by many Kirkend Holes. ) 'The reliability of the contacts of the packaged product is reduced. Therefore, in a preferred embodiment of the present invention, the alloy wire is mainly composed of silver (Ag), and the addition of gold (Au) element is completely avoided, so that the formation of the brittle gold-aluminum intermetallic compound can be avoided and the reliability of the alloy wire can be improved. degree. In addition, a large number of annealed twin structures increase the strength of the material and therefore improve reliability. Fig. 1 is a flow chart showing a method of forming a silver-based alloy wire in an embodiment of the present invention. Referring to Fig. 1, in step 102, a thick wire is provided, the thick wire being an alloy wire formed of at least silver, palladium, rhodium, and platinum. In step 104, a plurality of cold forming steps and a plurality of annealing steps are alternately performed to successively reduce the wire diameter of the thick wire to form a thin wire. The detailed method of the above steps is described below. Referring to step 102, a thick wire is provided, the thick wire being an alloy wire formed of at least a handle, a fault, and a layup. Silver, 35, enamel and facial ritual: Because these four elements can completely dissolve each other on the phase equilibrium diagram (疋Solution) 'The alloy wire which does not produce any brittle intermetallic phase precipitates (4) can be better Extensibility, hearing, error, and shape do not have much effect on resistivity. t Additions It has been found through experiments that an appropriate amount (4) can improve the silver line and resist sulfur and sulphur reduction, and at the same time, due to the low barrier of the diffusion speed wheel, the ion migration of silver can be avoided. In addition, it also has an inhibitory effect on the interfacial metal transition of silver and aluminum pads. However, when the content of palladium is too high, the electrical resistance of the alloy wire is increased. In addition, an appropriate amount of germanium (Ge) can effectively improve the oxidation resistance and vulcanization of the wire, and at the same time increase the joint strength of the solder joint, but when the content of germanium is too high, the ductility of the wire is lowered. In addition, an appropriate amount of platinum (Pt) can enhance the oxidation resistance, sulfidability and chloride ion corrosion of the wire, and also has a significant inhibitory effect on the ion migration phenomenon of silver, and also reduces the formation of a metal intermetallic compound between the silver alloy wire and the aluminum pad. However, when the content of platinum is too high, the electrical resistivity of the wire is remarkably improved. In one embodiment, the silver in the thick wire is the main component, and the addition, the error, and the I are added, wherein the content is about 0.01 to 1% by weight; the wrong content is less than 1500 ppm, preferably between 10 ppm and 1500 ppm. The content of the tumbling is below 350 ppm, preferably between 5 ppm and 350 ppm; and the content of silver, I bar, ruthenium, and ruthen is 100% by weight (for example, the content of silver is about 90 to 99.99% by weight). In another embodiment, the alloy wire further comprises a shed and is contained in an amount of less than 20 ppm, preferably from 1 ppm to 20 ppm. In this embodiment, the content of silver, absolute, wrong, platinum, and boron is 100% by weight. Appropriate amount of boron can produce grain boundary segregation in silver alloy. Generally, the segregation of impurity elements at the grain boundary of the material will cause the material to break along the crystal brittleness. However, the grain boundary segregation of the shed will not cause the grain boundary embrittlement, but instead It plays a beneficial role in strengthening the grain boundary and can significantly improve the ductility and fatigue resistance of the wire. However, when the content of the shed is too high, the internal embrittlement of the crystal grains is still caused. In other embodiments, the above-mentioned thick wire may also include other elements, but the precipitation of the added element and the metal to form a metal phase phase should be avoided, resulting in embrittlement of the material, improvement of corrosivity, or reduction of electrical conductivity of the conductor 10 201247904. . Therefore, it is preferred that the added elements be completely mutually soluble by the silver atoms without the formation of precipitates to ensure the ductility of the wires. It should be noted that in other examples, the alloy wire may further include other metals, non-metal elements, or other impurity components, and the invention is not limited to a silver-palladium-ruthenium-platinum quaternary alloy or silver-palladium-ruthenium. - a five-element alloy of platinum-boron. Therefore, as long as the weight ratio of silver:palladium in the thick wire is controlled to be 90 to 99.99: 0.01 to 10, and silver is the main component of the thick wire, and the content of palladium, rhodium, platinum, boron or other components is not more than the content of silver. Within the scope of the invention. In addition, since it is difficult to completely remove all impurities in the process of actual smelting, refining, cold forming, etc., and accurately achieve a mathematical or theoretical specific concentration, when the above impurity content falls within the corresponding standard or specification Within the scope of the acceptance, it is still considered to be within the scope of the present invention. Those of ordinary skill in the art to which this invention pertains should understand that the above-described corresponding standards or specifications may vary depending on the nature, conditions, requirements, etc., and therefore no specific standards or specifications are listed below. In one embodiment, the method of forming the thick wire is to heat-melt silver, palladium, rhodium, and platinum, and then cast into an ingot. Thereafter, the ingot is cold worked to form the above-mentioned thick wire formed of at least silver, palladium, rhodium, and platinum. In another embodiment, the above-mentioned thick wire is formed by continuous casting after heating, melting silver, palladium, rhodium, and platinum. In one embodiment, the thick wire has a wire diameter of about 5 to 10 mm. Referring to step 104, a plurality of cold forming steps and a plurality of annealing steps are alternately performed to successively reduce the wire diameter of the thick wire. Figure 2 shows the more detailed steps of the plurality of cold forming steps and annealing steps described in step 104. In FIG. 2, the plurality of cold forming steps 201247904 and the annealing step described in step 104 include at least the following steps: deformation between the wires in the first cold working forming step, the first ballast force, 104_1. In the amount of 104-2 formed by the ± and = forming steps, the first pass annealing was performed at 0%. . In the step temperature m, the annealing time is the cold forming step and the annealing step is as important as the second and the second. Then, in step 1〇4_3, the step-by-step step is taken. In step 104_4, the annealing temperature of the second annealing step of the last processing number is the step of the step: 1:5 #, where 'Tm is the material of the thick wire: the right: the first:: 04 -", the last cold forming is performed; the deformation between the wire formed by the forming process of the second plus 1 forming step and the wire formed by the penultimate upper::::: (4) is 1%: not more than 15% The above deformation amount refers to the reduction ratio of the cross-sectional area caused by the material of the :::: due to the cold working forming step. In the step purchase, the = post-annealing step 'the annealing annealing step of the last annealing step ^ The annealing temperature of the second annealing step is 2〇t~UKTC, and the annealing is 2~30 seconds. It should be noted that, in an embodiment, step (10) may also be performed (steps 1〇4-3, 1〇4_5). And two-way annealing in the shell example, the cold forming step includes a combination of drawing, extrusion, and the following. Alternatively, the cold forming step and the annealing step may be followed by any known or future developed cold working/ Annealing method. The thin wire formed after the above cold forming and annealing steps is 12 201247904 An alloy wire formed of less silver, palladium, rhodium and platinum, wherein the alloy wire comprises a central portion and a peripheral portion, and the central portion has elongated grains or equiaxed grains, the peripheral portion Having an equiaxed grain, and the number of grains having an annealing twins structure in the thin wire accounts for more than 20% of the total number of grains of the thin wire. In one embodiment, the wire of the thin wire The diameter is 10~50 μηη. Compared with the traditional metal wire, the above-mentioned thin wire can have better reliability. The reason for the formation of the above-mentioned annealed twin structure can be inferred according to the principle of physical metallurgy (please refer to George E. Dieter, Mechanical Metallurgy, McGRAW-HILL Book Company, 1976, P. 135-141. and RW Cahn, Physical Metallurgy, 1970, Pl 184-1185). The formation of the annealed twin structure is due to the accumulation of strain energy inside the material during the cold working process ( Strain), these strains will drive the atomic uniform shearing (Shear) of a partial region to the mirrored surface of the uncut atoms in the grain within the subsequent annealing heat treatment. It is called the crystal lattice position, which is Anneaiing Twin, and its symmetrical interface is Twin Boundary. Annealing twins mainly occur in the facet cube with the closest lattice arrangement (Face Centered Cubic; FCC) crystalline material, the twin boundary is low energy Σ 3 special grain boundary, the crystal orientation is 丨1丨1丨. Compared to the high angle grain Boundary formed by general annealing recrystallization, the interfacial energy of the twin boundary is only about 5% of the high angle grain boundary. In addition, in general, the smaller the stacking material (StackingFauh Energy), the easier it is to produce annealed twins, and the main strands of the alloy wire are silver and the stacking energy is about 5 〇erg/cm2, so it is easy. Annealed twins are formed. That is, not all metals can easily form twins 13 201247904 structure. For example, although aluminum is a face-centered cubic crystal structure material, its stacking energy is about 200 erg/cm2, so annealing twins rarely occur. Further, the cold working forming step described in Fig. 2 is also one of the factors for annealing the twin structure. Sufficient cold work deformation can accumulate strain energy to provide atomic driving force to produce annealed twins, but if the cold work deformation is too large, most grain nucleation will occur during the initial recrystallization stage of the annealing heat treatment (Nuclei of Recrystallized Grains), thus forming a large number of fine grains, reducing the chance of annealing twins. It should be noted that the method of forming the alloy wire described in Fig. 2 is only a preferred embodiment of the present invention, but the method of forming the alloy wire of the present invention is not limited thereto. 3A and 3B are views showing a silver-based alloy wire 300 formed in an embodiment of the present invention. Fig. 3A shows a schematic view of a line segment of a portion of the silver-based alloy wire 300. Fig. 3B shows a longitudinal sectional view along the longitudinal direction parallel to the alloy wire 3A shown in Fig. 3A. Referring to Fig. 3A, the silver-based alloy wire 300 is an alloy wire formed by adding at least bismuth, antimony or platinum as a main component silver. Referring to Fig. 3B, the longitudinal section of the alloy wire 3〇〇 is a polycrystalline structure of a face-centered cubic phase and the entirety is an equiaxed grain 302. In addition, each of the crystal grains is bounded by an angular grain boundary 304, wherein the number of crystal grains having an annealing twins structure 306 is 20 of the total number of crystal grains of the silver-based alloy wire 300. %the above. In a preferred embodiment, the number of grains of the annealed twin structure is from 30% to 60% of the total number of grains of the alloy wire, wherein the size of the 'equal grain 302 is, for example, between Ο.ίμιη to 6μηι' Its aspect ratio is between 1 and 2. In the 14th 201247904 3C diagram, the alloy wire is generally still equiaxed, but the central portion thereof further includes a long wire. Here, the aspect ratio of the elongated grain is greater than 2, and the middle portion refers to a portion of the wire radius value of 3 G % from the axial center of the wire. In the embodiment, the weight ratio of silver to palladium in the alloy wire 3〇〇, ～99.99: 0.01~10 锗 锗 content is below AH, preferably between U) ppm and Ppm. The content of Ming is below 35 (), compared to ppm to 350 ppm. Among them, silver is mainly used for this alloy wire, and the content of palladium, rhodium, platinum or other components is not more than the content of silver. In another embodiment, the alloy wire further comprises boron, and the boron content is preferably 2 ppm to 20 ppm. The advantages of the above alloys include, for example, the following: no gold is added, so that the metal-aluminum interfacial metal embrittlement can be avoided; 2. Adding palladium to the corrosion resistance and ion migration damage of the good silver alloy wire, and suppressing the reorganization and rectification Interfacial metal reaction of aluminum pad; 3) Adding antimony to enhance the oxidation resistance and thinning property of the silver alloy wire, and improve the joint strength of the solder joint; 4Add = to enhance the oxidation resistance, vulcanization and chloride ion corrosion of the wire Sex, the ion edge shift phenomenon of platinum and platinum and the interfacial metal reaction of silver/aluminum interface; 5. Adding boron = grain boundary of the alloy to improve the ductility and fatigue resistance of the wire. However, it should be noted that the above-mentioned silver-based alloy wire is mainly composed of silver and contains a specific ratio of I bar, yttrium, turn, and deletion. However, the present invention is not limited thereto. In other examples, silver-based alloy wires may be more scooped = other metals, non-metals, or other unavoidable impurity components. Gallery > The idea is that the addition of other metal iteins needs to be adjusted according to the needs of the application ~ to avoid affecting the properties of the alloy wire. For example, when copper is added to the above alloy wire ^, a material strengthening effect will occur, but the copper element will make people = 15 201247904 :: "sulfurization corrosion performance is greatly reduced, and because of the silver - copper alloy (three) in the day, life is not Continuously precipitated, causing wire breakage. In addition, copper will also make σ gold = more ^ become more brittle ' making the drawing process difficult, and at the same time in the wire bonding process is also easy to cause wafer breakdown. Another: adding rare earth elements can The grain of the alloy is refined, but the application of the wire in the sealing and bonding is required. 'The fine grain has more grain boundaries, the grain boundary is blocked, and the electron transport' increases the resistivity of the alloy, so it is not suitable for speed operation. And the packaging requirements of r%-fluid circuit electronic products. In addition, the chemical activity of rare earths will increase their oxidation and damage, making it easier for package wires to be energized = 'not conducive to the reliability of electronic products. Adding a dance to the alloy will deteriorate the ductility of the material; adding indium or tin to the alloy will form m to make the wire "temperately deteriorated, and continuous current can easily cause the wire to be melted; adding beryllium (Be) is Flammable flammability Solid dry dust or smoke is toxic; when it is nailed (10), money (10), hungry (〇S), silver (ΐΓ), its melting point (2310〇C, 1965. 0 3045°C and 2410 ° C) is much higher than the boiling point of silver (2212 〇 c), so its melting is extremely difficult 'and will greatly increase the resistivity. Also, some of the added elements on the phase equilibrium diagram 曰 and silver 幵 / j j 丨 metal phase Precipitati〇n, which causes embrittlement and high corrosivity of the material, and further reduces the electrical conductivity of the wire. Fortunately, the conventional wire rods of the present invention, for example, may have the following Advantages include: (1) Low resistance: Although silver has a low resistivity, the grain of the silver wire in the conventional process is fine grain (average particle size is about 0 5~2 μΠΐ), so it has a large number of high angles. The grain boundary 'causes the resistivity to increase. In addition, when the silver wire is wire bonded on the aluminum pad 201247904, a brittle intermetallic compound (Ag2Al or Ag4Al) can be formed, which causes electrical conduction. The property is reduced. The alloy wire of the present invention includes a large amount of retreat. Annealing Twin, the Twin Boundary of the annealed twin structure is a tuned (Coherent) crystal structure, which belongs to the low energy Σ 3 special grain boundary, and its interface energy is only the general high angle grain boundary 5 Therefore, the symmetric lattice arrangement of these annealed twins has little hindrance to electron transport and can exhibit lower resistivity. (2) Good mechanical strength: at least 20% of the alloy wires in the embodiments of the present invention are included. The inside of the grain contains an Annealing Twin structure, so that the mechanical strength of the wire can be maintained. Further, since the twin structure has a different crystal orientation (Crystal Orientation), it can be used. The movement of Dislocation produces a material reinforcement effect. Therefore, the tensile strength similar to that of the general fine grain structure wire can be maintained, but the difference between the row and the atom can be shifted by the twin boundary (CrossSlip), and the ductility is higher than that of the general fine grain. (3) Anti-oxidation and anti-corrosion ability: Generally speaking, silver often has the problem of sulphide corrosion in a sulfur-containing environment, so other precious metals on the silver will be used to avoid vulcanization. However, the metal is also completely dissolved into the molten silver solder ball substrate during the bonding process, so that the ball-point component of the temple line bonding is only the silver two gold with a small amount of protective metal. Therefore, the wire bonding material is welded. The point still occurs. Corruption (4) Image, because: It is still unable to effectively avoid the short circuit of the ball joint caused by the migration of silver electrolysis ions, and the Kirkenda hole effect when the wire is bonded. 201247904 ... and 'the alloy wire in each embodiment of the present invention has less than 2 ^ of crystal grains containing annealing Twin (Annealing Twin), because: the lower interface energy of the grain boundary can avoid oxidation, vulcanization and _ The path of the rot is light, so it can show better oxidation resistance and corrosion resistance. (4) The grain growth during the packaging process is not easy: the fine grain structure of the conventional wire material is bonded after the wire bonding, and the wire is accumulated in the vicinity of the solidification heat of the ball, which causes the grain to grow rapidly and becomes a heat affected zone. Reduce the strength of the cable test. However, at least 20% of the grain of the alloy wire of each embodiment of the present invention contains an Annealing Twin structure, and these annealed twins have a lower interfacial energy and a generally higher angle crystal structure. The world is stable. Therefore, not only in the high temperature state, the twinning boundary itself is not easy to move, but also the high-angle grain boundary around the grain in which it is located is locked, so that these high-angle grain boundaries cannot be moved, and thus the overall grain structure does not There is a clear heart: phenomenon. Therefore, even if the first contact (bump point) is cooled to room temperature during the wire bonding process, the original grain size can be maintained. In addition, when the packaged product undergoes various high-temperature reliability tests, it is also less stable than the field. Lead to crystals (5) Low electron mobility: In the traditional process, pure silver wire is liable to the Ion Migration in the water-containing encapsulation material, and finally becomes a short circuit of the electrode. In addition, when the pure silver wire is bonded to the aluminum pad, it is positive or negative. _ _ Since the diffusion coefficient in the aluminum atomic base (Matrix) is 1 to 2 to 10 compared with the aluminum atom in the silver base. In this case, the large difference in the diffusion speed of this interface will cause the two Kirkenda holes, resulting in an increase in resistivity and failure of the wire bonding ball. Ming 18 201247904 In the alloy wire of the present invention, since the atom has a very low diffusion rate through the low energy twin boundary or across the twin boundary, when applied to an electronic product, the internal atom of the wire is even at a high density current. It is also not easy to move. In view of the above advantages, the alloy wire of the present invention can be used for high voltage and high current electronic products requiring high reliability, especially for wire bonding of power components. Of course, according to the needs of the user, the alloy wire of the present invention can also be applied to other technical fields and applications, such as: audio wires, signal or power transmission lines, transformer wires, etc., and the wire diameter of the alloy wires can also be changed according to requirements. It is not limited to the scope of the above exemplification. In addition, it has been found experimentally that at least 20% of the grains in the alloy wire contain an annealed twin structure to achieve the above advantages. Therefore, although in the process of conventional metal wire for wire bonding, there may be occasions when an annealed twin structure occurs, but the number of crystal grains containing an annealed twin structure is usually less than 10% of all the crystal grains of the wire or even It does not contain an annealed twin structure at all, so it still cannot have the above advantages. The invention has been studied by the inventors for a long time and meticulously, and the alloying elements with specific composition and the control of the cold working deformation amount and the annealing temperature time can form a material structure containing a large amount of annealed twin crystals, and obtain a low resistivity, Packaged wire with high thermal conductivity, high strength, high ductility and excellent oxidation resistance. In more detail, the alloy composition provides excellent coordination between electrical conductivity and mechanical properties. 'The crystallographic boundary has the characteristics of effectively suppressing electromigration, improving material strength and ductility, and therefore, when performing wire bonding, not only has Very low resistivity and excellent performance in reliability testing. For example, in the most severe pressure pin test 19 201247904 (Pressure Cooker Test; PCT), it can withstand more than 128 hours under the conditions of temperature (Ta)=12rc, relative humidity (RH)=100%, 2 atmospheres. It is much higher than the 96 hours required for the reliability test of general electronic products. In another embodiment, 'Highly Accelerated Stress Test (HAST)' at a temperature (Ta) = 148 ° C, relative fishing (RH) = 90%, 3.6 volts bias It can reach more than 128 hours, and is also much higher than the 96 hours required by the general electronic product reliability test specification. Therefore, the alloy wire in the embodiments of the present invention can be applied to various high-speed power exchange integrated circuits, for example, a voltage drop type DC voltage exchange integrated circuit having an input voltage range of 4.5V to 17V and an operating frequency of 1200KHZ (Buck) DC/DC Converter), not limited to the voltage drop type DC voltage switching integrated circuit applied below the generally slower speed of 500KHZ. [Comparative Example 1] Alloy wire with a small amount of twin structure The alloy was alloyed by a Southern Zhoubo electrothermal vacuum, and its alloy composition was Ag-8wt%Au-3wt%Pd-0.005wt.%La. The above alloy was obtained by continuous casting to obtain a thick wire having a wire diameter of 6 mm. 8 cold working forming steps were carried out by drawing extension and annealing heat treatment to form a thin wire having a wire diameter of 25.4 μm. Then, the second last cold working forming step was carried out by drawing to form a thin wire having a wire diameter of 22.6 μm, and then annealing at 600 ° C for 5 seconds. Finally, the final cold forming step is taken to form a thin wire of 17·5 μm, and a final annealing step is performed, which has an annealing temperature of 700 ° C and an annealing time of 1 〇 second. After the final annealing step is completed, the winding wire completes the alloy wire product required for wire bonding. Figure 4 is a cross-sectional view showing the alloy wire of Comparative Example 1, in which the center 20 201247904 has elongated grains and a few very coarse equiaxed grains, and the periphery has fine equiaxed grains, and the grain size thereof At approximately 1 // m, the annealed twin structure accounts for only about 10% of the total number of grains. The above-mentioned alloy wire having a small amount of annealed twin structure was tested by passing a current of 0.2 A for 1200 hours, and the results are shown in Fig. 5. Referring to Fig. 5, after the current is passed through the alloy wire of Comparative Example 1, the elongated crystal grains at the center portion disappear, and the overall grain size is greatly increased by about 8/zm, and the wire is burned. [Example 1] Alloy wire having a large amount of twin structure The composition of the alloy containing silver as a main component by high-frequency electrothermal melting can be referred to Table 1. Table 1 shows the contents of palladium, rhodium, platinum, and boron in the alloy, and the other components in the alloy are silver. That is, the content of silver and the total content of palladium, rhodium, platinum, and boron in Table 1 reached 100% by weight. The above alloy was obtained in a continuous casting manner to obtain a thick wire having a wire diameter of 6 mm. Twelve cold forming steps were performed by wire drawing extension and annealing heat treatment to form a thin wire having a wire diameter of 22.6 μm. Then, the second last cold working forming step was carried out by drawing to form a thin wire having a wire diameter of 20 μm, and then annealing at 530 ° C for 2 seconds. Finally, the final cold forming step is performed to form a thin wire of 17.5 μm, and the final annealing step is performed, and the annealing temperature is 600 ° C and the annealing time is 15 seconds. After the final annealing step is completed, the coil wire completes the alloy wire product required for wire bonding. 201247904 Table 1 ίε 锗 (wt%) (wtppm) (wtppm) (wtppm) Composition 1 1.00 50 50 ... Composition 2 1.00 50 250 ... Composition 3 1.00 50 350 ... Composition 4 2.00 500 50 ... Composition 5 1.00 500 250 — Composition 6 1.00 500 350 ... Composition 7 1.00 1500 50 ... Composition 8 1.00 1500 250 — Composition 9 2.00 1500 350 ... Composition 10 3.20 50 50 ...· Composition 11 3.20 50 250 Composition 12 3.20 50 350 Composition 13 3.20 500 50 Composition 14 3.20 500 250 --- Composition 15 3.20 500 350 ... Composition 16 3.20 1000 50 ... Composition 17 3.20 1000 250 ... Composition 18 3.20 1000 350 Composition 19 6.00 50 50 ... Composition 20 6.00 50 250 ... Composition 21 6.00 50 350 Composition 22 6.00 500 50 ... Composition 23 6.00 500 250 Composition 24 8.00 500 350 ... Composition 25 10.00 1000 50 Composition 26 10.00 1000 250 — Composition 27 10.00 1000 350 ... Composition 28 3.00 50 50 20 Composition 29 6.00 50 150 15 Composition 30 10.00 50 50 10 Figure 6 shows Example 1 is a cross-sectional view of an Ag-3.2 wt.% Pd-50 ppm Ge-50 ppm Pt alloy wire of composition 10 in various compositions of a silver-based alloy wire, having a strip at the center thereof Grain size of equiaxed grains periphery about 4 μ m, is larger than Comparative Example 1 periphery equiaxed alloy wire or the like. As shown in Fig. 6, the alloy wire of Example 1 has an average grain number of 30 22 201247904% of the crystal grains having an annealed twin structure. The above alloy wire was passed through a current i of 〇.2A, and the results are shown in Fig. 7. Referring to Fig. 7, in the example i, the alloy wire of the Dingliu is only slightly grown after the current is passed, and the equiaxed grains of the position are slightly grown, and the wire is not melted. Figure 5). Control reliability test: In addition, 'the alloy wire of composition 10 in Example 1 is used to form a high-speed power exchanger product, and a series of reliability tests are carried out on the high-speed power exchange, and the results are shown in Table 2. Its rigorous Pressure Cooker Test (PCT) will be stunned for more than 12δ hours, much higher than the average electronic product reliability test for 96 hours, and another equally severe high accelerated life test (Acelerated Stress Test). , HAST) can actually reach 128 hours to ^ly also far higher than the 96 hours required by the general electronic product reliability test specification. Table 2 Test item (TEST ITEM) Test conditions (TEST CONDITION) 1. Precondition Test Bake (125 ° C; 24 hours) Temperature and humidity test (30 ° C; 60 ° / 〇 RH; 192 hours) Reflow: 260+0/-5 °C; 3 times 2. Pressure Cooker Test (PCT) Ta=121°C; 100%RH; 2 atmospheres; 96 hours 3 temperature cycle test (Temperature Cycling Test ; TCT) Ta=-65 °C~150°C (air to air); 15 minutes; 1000 cycles 201247904 4. Temperature & Humidity Test (THT) Ta=85° C; 85% RH; no bias; 1000 hours pass 5. High Temperature Storage Test (HTST) Ta = 150 ° C; 1000 hours pass 6. Low Temperature Storage Test (LTST) Ta = -40 ° C; 1000 hours pass 7. Highly Accelerated Stress Test (HAST) Ta = 148 ° C; 90% RH; 3.6 volt bias; 96 hours pass 8. Thermal shock test ; TST) Ta = -65 ° C ~ 150 ° C; 5 minutes; 1000 cycles through Table 3 It shows the nature and results of the reliability test alloy wire embodiments different embodiment of the metal component formed in proportion. Table 3 Strength (Rf) Resistance (μΩαη) Pressure cooker test (168hr) Temperature cycle test (lOOOCyc) High temperature storage test (1000hr) Composition 1 8.55 1.88 Passing through composition 2 8.76 1.90 Passing through composition 3 8.92 1.93 Passing through composition 4 8.62 1.89 by passing the composition 5 8.67 1.91 by passing the composition 6 8.73 1.95 by passing the composition 7 8.81 1.92 by passing the composition 8 8.87 1.96 by passing the composition 9 8.94 1.99 by passing the composition 10 9.47 2.76 by passing the composition 11 9.63 2.79 by passing through the composition of 9.87 2.81 by passing through the composition 13 9.62 2.84 by passing the composition 14 9.83 2.87 by passing the composition 15 9.95 2.91 by passing the composition 16 9.71 2.88 by passing the composition 17 9.89 2.92 by passing the 24 201247904 composition 18 10.11 2.97 by passing the composition 19 11.35 4.12 by passing the composition 20 11.49 4.15 by passing the composition 21 11.62 4.19 by passing the composition 22 11.57 4.20 Passing through the composition 23 11.71 4.24 Passing through the composition 24 11.92 4.27 Passing through the composition 25 12.01 4.29 Passing through the composition 26 12.53 4.31 Passing through the composition 27 12.87 4.35 Passing through the composition 28 8.52 1.74 Passing through the composition 29 9.36 2.70 By passing through the composition 30 11.42 4.10 by passing the above, although the invention has been disclosed in several preferred embodiments as above, which are not intended to limit the invention, any one of ordinary skill in the art, without departing from the spirit of the invention And the scope of the invention is to be construed as being limited by the scope of the appended claims. 25 201247904 [Simplified description of the drawings] Fig. 1 is a flow chart showing a method of forming a silver-based alloy wire according to an embodiment of the present invention. Figure 2 shows the more detailed steps of the plurality of cold forming steps and the annealing step described in step 104. Fig. 3A-3C shows a silver-based alloy wire formed in an embodiment of the present invention. Fig. 3A shows the appearance of the alloy wire, and Fig. 3B shows that the entire wire is equiaxed, and Fig. 3C shows that the center of the wire has elongated crystal grains and the outer periphery has equiaxed grains. Fig. 4-5 shows an alloy wire of a comparative example of the present invention. Figure 4 shows the original alloy wire, and Figure 5 shows the alloy wire after the current test. 6-7 show an alloy wire according to an embodiment of the present invention. Figure 6 shows the original alloy wire, and Figure 7 shows the alloy wire after the current test. [Main component symbol description] 3 00~ alloy wire 302~ equiaxed grain 304~South angle grain boundary 306~annealed twin structure 3 0 8~ long strip grain 26