JP3932235B2 - Ball forming apparatus and method for wire bonder - Google Patents

Ball forming apparatus and method for wire bonder Download PDF

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JP3932235B2
JP3932235B2 JP04809899A JP4809899A JP3932235B2 JP 3932235 B2 JP3932235 B2 JP 3932235B2 JP 04809899 A JP04809899 A JP 04809899A JP 4809899 A JP4809899 A JP 4809899A JP 3932235 B2 JP3932235 B2 JP 3932235B2
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discharge
voltage
current
wire
time
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JP2000252316A (en
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正直 浦
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Kaijo Corp
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    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
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    • H01L2224/85045—Reshaping, e.g. forming the ball or the wedge of the wire connector by heating means, e.g. "free-air-ball" using a corona discharge, e.g. electronic flame off [EFO]
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Description

【０００１】
【発明の属する技術分野】
本発明は、被ボンディング部品としての半導体デバイスの組立工程において、第１ボンディング点、例えば半導体チップ上の電極と第２ボンディング点、例えばリードフレームに配設された外部リードとをワイヤを用いて接続するワイヤボンディング装置に関し、特に、ワイヤの先端に所定の大きさのボールを形成してボンディングを行うワイヤボンダ用ボール形成装置及びその方法に関する。
【０００２】
【従来の技術】
従来、金線又は銅、アルミニウムなどのワイヤを用いて第１ボンディング点となるＩＣチップ上の電極（パッド）と、第２ボンディング点となるリードとを接続するワイヤボンディング装置においては、先ずキャピラリから送り出されたワイヤの先端と放電電極（トーチロッド）との間に高電圧を印加することにより放電を起こさせ、その放電エネルギーによりワイヤの先端部を溶融してキャピラリ内に挿通されたワイヤの先端にボールを形成するようにしている。
【０００３】
図３は、キャピラリ８から送り出されたワイヤ７の先端と放電電極９との間に高電圧を印加してキャピラリ８の先端にボールを形成させるための従来のワイヤボンダ用ボール形成装置の構成をブロック図で示したものである。
【０００４】
図３に示すように、従来のワイヤボンダ用ボール形成装置は、高電圧を発生する直流高圧電源１の正極端子（＋）は、ワイヤ７の保持及び開放を行うクランパ６を介してボンディングツールとしてのキャピラリ８に挿通されたワイヤ７に対して正極電圧を与えるように成っている。一方、直流高圧電源１の負極端子（−）は定電流開閉器２及び放電安定器５を介して放電電極９に対し負極電圧与えるように成っている。
【０００５】
前記放電安定器５は、放電中の電流が何らかの原因により減少してもインダクタＬの自己誘導作用によりこの電流の減少分に相当する電圧を上昇させて放電を安定維持させるためのものである。
【０００６】
前記定電流開閉器２には、定電流開閉器２に内蔵されたスイッチ回路（図示せず）の開閉制御を成すためのタイマ回路４が接続されており、このタイマ回路４には放電開始信号であるトリガ信号Ｔｒが印加されるように成っている。
【０００７】
また、前記定電流開閉器２には、キャピラリ８の先端に送り出されたワイヤ７と放電電極９との放電路に流れる電流（以下放電電流という）の大きさを制御するための放電電流設定器１０が接続されいる。
【０００８】
また、前記放電電流設定器１０の入力部はマイクロコンピュータ２０の出力部に接続されており、前記マイクロコンピュータ２０は、入力装置としてのキーボード実行スイッチ２１より入力されたボール径の数値より、所定のボール径の形成に必要な放電電流を計算し、計算された放電電流値を前記放電電流設定器１０の入力部に出力する。
【０００９】
前記定電流開閉器２は、放電電流を前記放電電流設定器１０より出力される電圧の大きさに応じた一定の電流（定電流）になるように制御する。
【００１０】
以上に示した図３の構成よりなる装置を用いてボールの形成を行うには、放電電流設定器１０は、マイクロコンピュータ２０により設定された所定の放電電流を流すように定電流開閉器２に対して出力電圧を与える。
【００１１】
そして、外部からのトリガ信号Ｔｒによってタイマ回路４がトリガされると、タイマ回路４からは定電流開閉器２に内蔵されたスイッチ回路（図示せず）に対してタイマ回路４で設定された所定時間、スイッチ回路を“オン”動作させるための制御信号が発生する。
【００１２】
定電流開閉器２に内蔵されたスイッチ回路の“オン”動作によって放電安定器５を介して放電電極９とクランパ６によって保持されたワイヤ７の先端とのギャップ（放電路）Ｓに対して直流高電圧が印加され、ワイヤ７の先端と放電電極９との間で放電が成される。放電開始から一定時間経過後、タイマ回路４は定電流開閉器２に内蔵されたスイッチ回路を“オフ”状態に制御し、放電を終了させる。
【００１３】
放電により発生した熱エネルギー（ジュール熱）によってワイヤ７の先端が溶融されて、キャピラリ８の先端にはボールが形成される。
【００１４】
【発明が解決しようとする課題】
近年の集積回路（ＩＣ）の高密化に伴うパッドサイズ、パッドピッチの縮小化により、キャピラリ８の先端に形成するボールのサイズ（直径）も小さいもの（ボールの直径が５０μｍ以下）が要求されている（以下にボールのサイズが小さいものを小ボールという）。
【００１５】
従来のボール形成装置においては、所定の放電エネルギーをワイヤ７の先端と放電電極９との間に印加するために、一定の放電電流を流す定電流制御が行われている。
【００１６】
しかしながら、放電時に一定電流を流してボールを形成するワイヤボンダ用ボール形成装置では下記の解決すべき課題を有している。
【００１７】
第一に、高電圧の印加によるキャピラリ８の先端に送り出されたワイヤ７と放電電極９との間の気体（空気）の絶縁破壊により放電電流が流れ、この電流が大きいと放電エネルギーによる発熱が起こり、このためワイヤ７付近の空気に急激な熱膨張が発生し、この空気の急激な熱膨張により形成中のボールが飛散することがある。特に、小ボールを形成する場合には、ボールの飛散が発生することがある。
【００１８】
このため、従来のボール形成装置で小ボールを形成する場合には、ワイヤ７と放電電極９との間の放電電流値を小さくし、また、放電時間を長くすることにより急激な放電エネルギーの発生を押さえていた。
【００１９】
しかしながら、上記の方法では放電時間が長くなるため、ワイヤボンディングに要する時間が増え、半導体デバイスの生産数が低下する。
【００２０】
第二に、放電エネルギーが一定値の場合、単位時間当たりに発生する熱エネルギーも一定となり、ボールの形成が進むとボールの表面からの放熱量が増大し、ボールの表面温度が低下し、ボール径のばらつきが発生することがある。特に、小ボールの形成では、ボール径のばらつきが発生しやすい。
【００２１】
そこで、本発明は、電流設定手段から出力される出力値を時間とともに直線的に上昇する電圧に変換する電圧−時間変換手段と、前記電流設定手段の出力値と前記電圧変換手段の出力値との加算を行う加算手段とを備え、前記加算手段からの信号により放電中の電流を制御することにより放電エネルギーを徐々に増加させ、所定の形状のボールを形成するワイヤボンダ用ボール形成装置及びその方法を提供することを目的とする。
【００２２】
【課題を解決するための手段】
本発明によるワイヤボンダ用ボール形成装置は、キャピラリ先端から送り出されたワイヤの先端と放電電極との間に高電圧を印加することにより放電を起こさせ、その放電エネルギーによりワイヤの先端部を溶融してボールを形成するワイヤボンダ用ボール形成装置であって、放電電流を設定する電流設定手段と、前記電流設定手段から出力される出力値を受けて、時間とともに直線的に上昇する電圧に変換する電圧−時間変換手段と、前記電流設定手段の出力値と前記電圧変換手段の出力値との加算を行う加算手段とを備え、前記加算手段からの信号により放電中の電流を制御する構成としたものである。
【００２３】
また、本発明によるワイヤボンダ用ボール形成装置の電圧−時間変換手段は、積分回路でなるものである。
【００２４】
また、本発明によるワイヤボンダ用ボール形成方法は、キャピラリ先端から送り出されたワイヤの先端と放電電極との間に高電圧を印加することにより放電を起こさせ、その放電エネルギーによりワイヤの先端部を溶融してボールを形成するワイヤボンダ用ボール形成方法であって、放電電流を設定する電流設定手段と、前記電流設定手段から出力される出力値を受けて、時間とともに直線的に上昇する電圧に変換する電圧−時間変換手段と、前記電流設定手段の出力値と前記電圧変換手段の出力値との加算を行う加算手段とを備え、前記加算手段からの信号により放電中の電流を制御することにより所定のボール径を形成するものである。
【００２５】
【発明の実施の形態】
以下図面を参照して、本発明によるワイヤボンダ用ボール形成装置の実施の形態について説明する。
【００２６】
図１は、本発明によるワイヤボンダ用ボール形成装置のブロック図を示したものである。なお、図３に示した従来の装置と同一機能及び構成を有するものについては同一の参照符号用いて表し、詳細な説明は省略する。
【００２７】
図１に示すように、高電圧を発生する直流高圧電源１及び放電を安定させる放電安定器５は図３に示す従来の装置と同様である。
【００２８】
図３に示す、放電電流を設定する電流設定手段としての放電電流設定器１０の入力部には、マイクロコンピュータ２０の出力部が接続されている。また、前記マイクロコンピュータ２０には、所定のボール径を設定するキーボード実行スイッチ２１が接続されており、前記キーボード実行スイッチ２１より入力されたボール径の数値より、前記マイクロコンピュータ２０は、所定のボール径の形成に必要な放電電流値を計算し、計算された放電電流値を電流設定手段としての放電電流設定器１０に出力する。
【００２９】
電流設定手段としての放電電流設定器１０は、前記マイクロコンピュータ２０から出力された放電電流値を電圧に変換し、変換した電圧を電圧−時間変換手段としての積分器１１及び加算手段としての加算器１２に出力する。
【００３０】
電圧−時間変換手段としての積分器１１は前記放電電流設定器１０からの出力電圧を受けて、時間とともに直線的に上昇する電圧に変換し、加算手段としての加算器１２の他の入力端子に出力する。
【００３１】
尚、電圧−時間変換手段としての積分器１１は、演算増幅器、コンデンサ、定電流器又は抵抗等より構成されており、コンデンサを流れる電流の時間積分に比例する性質を利用し、入力電圧の時間積分に比例した出力電圧を得ている。
【００３２】
また、電圧−時間変換手段としての積分器１１には、外部からの信号により積分された出力電圧を初期化する入力端子が設けられており、放電完了後に外部信号（図１に示すＣｒ）より積分器１１の出力電圧の初期化が行われ、積分器１１の出力電圧は“ゼロ”となる。
【００３３】
前記加算器１２は、電流設定手段としての前記放電電流設定器１０からの出力電圧と電圧−時間変換手段としての前記積分器１１からの出力電圧との加算を行い、反転器１３に出力する。
【００３４】
前記加算器１２は、演算増幅器、抵抗より構成されており、正極性の入力電圧を加算し、出力は入力電圧の極性を反転した負極性の出力電圧となる。
【００３５】
前記反転器１３は加算器１２からの負極性の出力電圧の極性を反転し、正極性の出力電圧を定電流開閉器２に出力する。
【００３６】
また、前記定電流開閉器２には放電時間を制御するタイマ回路４が接続されている。
【００３７】
前記タイマ回路４は、制御装置（図示せず）より放電開始信号であるトリガ信号Ｔｒにより内部のタイマ回路４が動作を開始し、動作開始から一定時間まで“オン”動作信号を前記定電流開閉器２に内蔵されたスイッチ回路（図示せず）に出力する。
【００３８】
前記定電流開閉器２は、前記反転器１３の出力電圧の大きさに比例した放電電流を流すように制御する。また、このときの放電電流の“オン−オフ”制御は前記タイマ回路４の出力信号により制御される。
【００３９】
以下に、上記構成よりなるワイヤボンダ用ボール形成装置の動作について、図１及び図２を参照して説明する。図２は、図１の各部の出力波形を示す図である。
【００４０】
図１に示すように、最初に、所望のボール径に関するデータがキーボード実行スイッチ２１よりマイクロコンピュータ２０に入力され、マイクロコンピュータ２０によりボールの形成に必要な放電電流のデータが演算され、演算結果である放電電流値をマイクロコンピュータ２０内のメモリ（図示せず）に記憶する。但し、キーボード実行スイッチ２１によるボール径に関するデータは、マイクロコンピュータ２０内のメモリ（図示せず）に記憶されているため、キーボード実行スイッチ２１によるマイクロコンピュータ２０への入力は、ボール径に関するデータを変更するときのみ行えばよい。
【００４１】
図１に示すように、ワイヤ７と放電電極９が所定の距離Ｓ離間された状態にあるとき、外部の制御手段（図示せず）よりタイマ回路４にトリガ信号Ｔｒが印加されてタイマ回路４が作動し、放電電極９とワイヤ７との間で放電が開始される。タイマ回路４は、トリガ信号Ｔｒが印加されてからタイマ回路４で設定された所定時間（図２のＴ０からＴ１までの時間）定電流開閉器２に内蔵されたスイッチ回路（図示せず）を“オン”動作させるための制御信号（図１及び図２のｅ）を発生する。
【００４２】
また、マイクロコンピュータ２０は、タイマ回路４にトリガ信号Ｔｒが印加されると同時に、マイクロコンピュータ２０内のメモリ（図示せず）に記憶されている放電電流値を電流設定手段としての放電電流設定器１０に出力する。
【００４３】
放電電流設定器１０は、前記マイクロコンピュータ２０から出力された放電電流値としての信号に応じた電圧値に変換し、変換した電圧値（図２のＶ１）は出力電圧（図１及び図２のａ）として、電圧−時間変換手段としての積分器１１及び加算手段としての加算器１２に出力する。
【００４４】
電圧−時間変換手段としての積分器１１は前記放電電流設定器１０からの出力電圧を受けて、時間とともに直線的に上昇する電圧（図１及び図２のｂ）に変換し、加算手段としての加算器１２の他の入力端子に出力する。
【００４５】
電圧−時間変換手段としての積分器１１からの出力電圧は、前記放電電流設定器１０からの出力電圧の印加直後は“ゼロ”であり、積分回路内部のコンデンサーに電荷が徐々に蓄積されて出力電圧が上昇し、タイマ回路４の制御信号が図２で示すＴ１の時点で最大出力電圧値（図２のＶ２）となる。
【００４６】
前記加算器１２は、電流設定手段としての放電電流設定器１０からの出力電圧（図１及び図２のａ）と電圧−時間変換手段としての前記積分器１１からの出力電圧（図１及び図２のｂ）との加算を行い、加算した電圧（図１及び図２のｃ）を反転器１３に出力する。
【００４７】
尚、前記反転器１３からの出力電圧値は図２に示すようにＴ０で−Ｖ１となり、その後直線的に上昇し、放電完了時のＴ１で−（Ｖ１＋Ｖ２）となる。
【００４８】
前記反転器１３は、加算器１２からの出力電圧（図２のｃ）の極性を反転し、極性が反転された出力電圧（図２のｄ）を、定電流開閉器２に出力する。
【００４９】
定電流開閉器２は、加算器１２からの出力電圧の極性が反転された前記反転器１３の出力電圧の大きさ対応した、放電電流を流すよう制御する。
【００５０】
即ち、反転器１３からの出力電圧値は、図２に示すようにＴ０でＶ１となり、その後直線的に上昇し、放電完了時のＴ１で（Ｖ１＋Ｖ２）まで上昇する。
【００５１】
このときの放電電流は、放電開始よりワイヤ７と放電電極９との間の絶縁破壊が行われた直後に図２に示すＩｓの大きさの電流が流れ、その後電流値は直線的に上昇し、反転器１３からの出力電圧値が図２に示す（Ｖ１＋Ｖ２）に達した時には、図２に示すＩｅの大きさの電流が流れる。
【００５２】
タイマ出力信号がＴ１に達した時点で、定電流開閉器２内部のスイッチ回路は“オフ”となり、放電電流を遮断する。また、定電流開閉器２内部のスイッチ回路が“オフ”状態と同時に、積分回路には外部からのリセット信号Ｃｒが印加され、積分回路の出力電圧は“ゼロ” となり初期化される。
【００５３】
以上の実施例で説明した放電電流を制御することにより、放電中の放電エネルギーを制御することができる。
【００５４】
即ち、ワイヤの先端と放電電極との間の放電エネルギーＰは、一般にワイヤと放電電極間電圧Ｅ、放電電流Ｉ、放電時間Ｔとの積となり、次のように表される。
放電エネルギーＰ＝放電電極間電圧Ｅ・放電電流Ｉ・放電時間Ｔ・・・（１）
【００５５】
（１）式より、放電電極間電圧Ｅを一定とすると、放電電流を時間とともに直線的に増加することにより、単位時間当たりの放電エネルギーも放電電流と同様に直線的に時間とともに増加していく。
【００５６】
また、積分器１１を構成するコンデンサー又は抵抗の値を変えることにより、積分器１１の時間に対する出力電圧の傾きが変化する。積分器１１の時間に対する出力電圧の傾きが変化することにより、加算器１２から反転器１３を経由して出力される出力電圧の時間に対する傾きも変化し、定電流開閉器２による放電電流の大きさも変わるため、放電エネルギーを制御することができる。例えば、積分器１１の時間に対する出力電圧の傾き（変化率）を大きくすることにより、所定の放電エネルギーを発生する時間が短くなり、これにより放電時間の短縮が行える。
【００５７】
以上のように、放電時の放電電流を時間に対して増加させることにより、放電電極９とワイヤ７の先端で発生する放電エネルギーを制御することができ、所定のボールの形成を行うことができる。
【００５８】
また、積分器１１の時間に対する出力電圧の傾きを変化させることにより放電時間が短縮される。
【００５９】
【発明の効果】
以上述べたように、ボールの形成時に放電エネルギーを制御することにより、放電時の急激な空気の熱膨張が起こらないため、ボールの飛散の発生を防ぐことができる。また、ボール形成進行中のボール表面からの輻射損失分を補うため、ばらつきの少ない小ボールを形成することができる。
【００６０】
更に、積分器の時間に対する出力電圧の傾きを変化させることにより、放電時間を短縮することができるため、ワイヤボンディング時間の短縮が可能となる。
【図面の簡単な説明】
【図１】本発明によるボール形成装置のブロック図である。
【図２】図１に示すボール形成装置のトリガ信号Ｔｒ、タイマ回路出力信号、放電電流設定器出力電圧、積分器出力電圧、積分器リセット信号、加算器出力電圧、反転器出力電圧積、放電電流の各波形を示す図である。
【図３】従来のボール形成装置のブロック図である。
【符号の説明】
１ 直流高圧電源
２ 定電流開閉器
４ タイマ回路
５ 放電安定器
６ クランパ
７ ワイヤ
８ キャピラリ
９ 放電電極（トーチロッド）
１０ 放電電流設定器
１１ 積分器
１２ 加算器
１３ 反転器
２０ マイクロコンピュータ
２１ キーボード実行スイッチ[0001]
BACKGROUND OF THE INVENTION
According to the present invention, in an assembly process of a semiconductor device as a part to be bonded, a first bonding point, for example, an electrode on a semiconductor chip and a second bonding point, for example, an external lead disposed on a lead frame are connected using a wire. In particular, the present invention relates to a wire bonder ball forming apparatus and method for forming a ball of a predetermined size at the tip of a wire for bonding.
[0002]
[Prior art]
Conventionally, in a wire bonding apparatus for connecting an electrode (pad) on an IC chip serving as a first bonding point and a lead serving as a second bonding point using a wire such as gold wire, copper, or aluminum, first from the capillary Discharge occurs by applying a high voltage between the tip of the fed wire and the discharge electrode (torch rod), and the tip of the wire is inserted into the capillary by melting the tip of the wire by the discharge energy. A ball is formed on the surface.
[0003]
FIG. 3 is a block diagram of a conventional wire bonder ball forming apparatus for forming a ball on the tip of the capillary 8 by applying a high voltage between the tip of the wire 7 fed from the capillary 8 and the discharge electrode 9. It is shown in the figure.
[0004]
As shown in FIG. 3, in the conventional wire bonder ball forming apparatus, the positive terminal (+) of the DC high-voltage power source 1 that generates a high voltage is used as a bonding tool via a clamper 6 that holds and opens the wire 7. A positive voltage is applied to the wire 7 inserted through the capillary 8. On the other hand, the negative terminal (−) of the DC high voltage power supply 1 is configured to apply a negative voltage to the discharge electrode 9 via the constant current switch 2 and the discharge stabilizer 5.
[0005]
The discharge stabilizer 5 is for maintaining a stable discharge by increasing the voltage corresponding to the decrease of the current by the self-inductive action of the inductor L even if the current during the discharge decreases for some reason.
[0006]
The constant current switch 2 is connected to a timer circuit 4 for performing switching control of a switch circuit (not shown) built in the constant current switch 2, and the timer circuit 4 has a discharge start signal. The trigger signal Tr is applied.
[0007]
The constant current switch 2 includes a discharge current setting device for controlling the magnitude of a current (hereinafter referred to as a discharge current) flowing in the discharge path between the wire 7 sent to the tip of the capillary 8 and the discharge electrode 9. 10 is connected.
[0008]
Moreover, the input part of the discharge current setting device 10 is connected to the output part of the microcomputer 20, and the microcomputer 20 has a predetermined value from the numerical value of the ball diameter input from the keyboard execution switch 21 as an input device. The discharge current required for forming the ball diameter is calculated, and the calculated discharge current value is output to the input part of the discharge current setting device 10.
[0009]
The constant current switch 2 controls the discharge current to be a constant current (constant current) corresponding to the magnitude of the voltage output from the discharge current setting device 10.
[0010]
In order to form a ball using the apparatus having the configuration shown in FIG. 3 as described above, the discharge current setting device 10 is connected to the constant current switch 2 so that a predetermined discharge current set by the microcomputer 20 flows. In contrast, an output voltage is given.
[0011]
When the timer circuit 4 is triggered by an external trigger signal Tr, the timer circuit 4 sets a predetermined circuit set by the timer circuit 4 to a switch circuit (not shown) built in the constant current switch 2. For a time, a control signal is generated to turn on the switch circuit.
[0012]
With respect to the gap (discharge path) S between the discharge electrode 9 and the tip of the wire 7 held by the clamper 6 through the discharge ballast 5 by the “ON” operation of the switch circuit built in the constant current switch 2. A high voltage is applied, and a discharge is generated between the tip of the wire 7 and the discharge electrode 9. After a lapse of a certain time from the start of discharge, the timer circuit 4 controls the switch circuit built in the constant current switch 2 to the “off” state and ends the discharge.
[0013]
The tip of the wire 7 is melted by the thermal energy (Joule heat) generated by the discharge, and a ball is formed at the tip of the capillary 8.
[0014]
[Problems to be solved by the invention]
Due to the reduction in pad size and pad pitch accompanying the recent increase in density of integrated circuits (ICs), the size (diameter) of the ball formed at the tip of the capillary 8 is required to be small (ball diameter is 50 μm or less). (Hereinafter, small balls are called small balls).
[0015]
In the conventional ball forming apparatus, constant current control for supplying a constant discharge current is performed in order to apply predetermined discharge energy between the tip of the wire 7 and the discharge electrode 9.
[0016]
However, a wire bonder ball forming apparatus that forms a ball by flowing a constant current during discharge has the following problems to be solved.
[0017]
First, a discharge current flows due to dielectric breakdown of gas (air) between the wire 7 and the discharge electrode 9 sent to the tip of the capillary 8 due to the application of a high voltage, and if this current is large, heat is generated by the discharge energy. For this reason, rapid thermal expansion occurs in the air in the vicinity of the wire 7, and the ball being formed may be scattered by the rapid thermal expansion of the air. In particular, when a small ball is formed, the ball may be scattered.
[0018]
For this reason, when a small ball is formed by a conventional ball forming apparatus, the discharge current value between the wire 7 and the discharge electrode 9 is reduced, and the discharge time is lengthened to generate a sudden discharge energy. I was holding down.
[0019]
However, in the above method, since the discharge time becomes long, the time required for wire bonding increases, and the number of semiconductor devices produced decreases.
[0020]
Second, when the discharge energy is a constant value, the heat energy generated per unit time is also constant, and as the ball formation progresses, the amount of heat released from the ball surface increases, the ball surface temperature decreases, Variation in diameter may occur. In particular, the formation of small balls tends to cause variations in ball diameter.
[0021]
Therefore, the present invention provides a voltage-time conversion means for converting an output value output from the current setting means into a voltage that rises linearly with time, an output value of the current setting means, and an output value of the voltage conversion means. A wire bonder ball forming apparatus and method for forming a ball having a predetermined shape by gradually increasing discharge energy by controlling a current during discharge according to a signal from the adding means. The purpose is to provide.
[0022]
[Means for Solving the Problems]
The wire bonder ball forming apparatus according to the present invention causes a discharge by applying a high voltage between the tip of the wire fed from the tip of the capillary and the discharge electrode, and melts the tip of the wire by the discharge energy. A wire bonder ball forming apparatus for forming a ball, comprising: a current setting means for setting a discharge current; and a voltage that receives an output value output from the current setting means and converts it into a voltage that rises linearly with time— It comprises a time conversion means, and an addition means for adding the output value of the current setting means and the output value of the voltage conversion means, and is configured to control the current during discharge by a signal from the addition means. is there.
[0023]
The voltage-time conversion means of the wire bonder ball forming apparatus according to the present invention comprises an integrating circuit.
[0024]
Also, the wire bonder ball forming method according to the present invention causes a discharge by applying a high voltage between the tip of the wire fed from the capillary tip and the discharge electrode, and the tip of the wire is melted by the discharge energy. A wire bonder ball forming method for forming a ball by receiving a current setting means for setting a discharge current and an output value output from the current setting means, and converting it into a voltage that rises linearly with time. A voltage-time conversion unit; and an addition unit that adds the output value of the current setting unit and the output value of the voltage conversion unit, and controls a current during discharge by a signal from the addition unit to determine a predetermined value. The ball diameter is formed.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a wire bonder ball forming apparatus according to the present invention will be described below with reference to the drawings.
[0026]
FIG. 1 is a block diagram of a wire bonder ball forming apparatus according to the present invention. Components having the same functions and configurations as those of the conventional apparatus shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0027]
As shown in FIG. 1, a DC high voltage power source 1 that generates a high voltage and a discharge stabilizer 5 that stabilizes discharge are the same as those of the conventional apparatus shown in FIG.
[0028]
The output part of the microcomputer 20 is connected to the input part of the discharge current setting device 10 as a current setting means for setting the discharge current shown in FIG. Further, a keyboard execution switch 21 for setting a predetermined ball diameter is connected to the microcomputer 20, and the microcomputer 20 determines the predetermined ball diameter based on the numerical value of the ball diameter input from the keyboard execution switch 21. A discharge current value necessary for forming the diameter is calculated, and the calculated discharge current value is output to a discharge current setting device 10 as current setting means.
[0029]
The discharge current setting device 10 as current setting means converts the discharge current value output from the microcomputer 20 into voltage, and the converted voltage is an integrator 11 as voltage-time conversion means and an adder as addition means. 12 is output.
[0030]
The integrator 11 as voltage-time conversion means receives the output voltage from the discharge current setter 10 and converts it into a voltage that rises linearly with time, and is applied to the other input terminal of the adder 12 as addition means. Output.
[0031]
The integrator 11 as a voltage-time conversion means is composed of an operational amplifier, a capacitor, a constant current device, a resistor, or the like, and utilizes the property proportional to the time integration of the current flowing through the capacitor, and the time of the input voltage. An output voltage proportional to the integral is obtained.
[0032]
Further, the integrator 11 as a voltage-time conversion means is provided with an input terminal for initializing an output voltage integrated by an external signal, and from an external signal (Cr shown in FIG. 1) after the discharge is completed. The output voltage of the integrator 11 is initialized, and the output voltage of the integrator 11 becomes “zero”.
[0033]
The adder 12 adds the output voltage from the discharge current setter 10 as current setting means and the output voltage from the integrator 11 as voltage-time conversion means, and outputs the result to the inverter 13.
[0034]
The adder 12 includes an operational amplifier and a resistor. The adder 12 adds a positive input voltage, and an output is a negative output voltage obtained by inverting the polarity of the input voltage.
[0035]
The inverter 13 inverts the polarity of the negative output voltage from the adder 12 and outputs the positive output voltage to the constant current switch 2.
[0036]
The constant current switch 2 is connected to a timer circuit 4 that controls the discharge time.
[0037]
The timer circuit 4 starts the operation of the internal timer circuit 4 in response to a trigger signal Tr which is a discharge start signal from a control device (not shown). To a switch circuit (not shown) built in the device 2.
[0038]
The constant current switch 2 is controlled so that a discharge current proportional to the magnitude of the output voltage of the inverter 13 flows. Further, the “on / off” control of the discharge current at this time is controlled by the output signal of the timer circuit 4.
[0039]
The operation of the wire bonder ball forming apparatus having the above-described configuration will be described below with reference to FIGS. FIG. 2 is a diagram showing an output waveform of each part in FIG.
[0040]
As shown in FIG. 1, first, data relating to a desired ball diameter is input to the microcomputer 20 from the keyboard execution switch 21, and the microcomputer 20 calculates discharge current data necessary for ball formation. A certain discharge current value is stored in a memory (not shown) in the microcomputer 20. However, since the data related to the ball diameter by the keyboard execution switch 21 is stored in a memory (not shown) in the microcomputer 20, input to the microcomputer 20 by the keyboard execution switch 21 changes the data regarding the ball diameter. You only need to do it.
[0041]
As shown in FIG. 1, when the wire 7 and the discharge electrode 9 are separated by a predetermined distance S, a trigger signal Tr is applied to the timer circuit 4 from an external control means (not shown), and the timer circuit 4 Is activated, and discharge is started between the discharge electrode 9 and the wire 7. The timer circuit 4 includes a switch circuit (not shown) built in the constant current switch 2 for a predetermined time (time from T0 to T1 in FIG. 2) set by the timer circuit 4 after the trigger signal Tr is applied. A control signal ("e" in FIGS. 1 and 2) for generating an "on" operation is generated.
[0042]
In addition, the microcomputer 20 applies a trigger signal Tr to the timer circuit 4 and simultaneously uses a discharge current value stored in a memory (not shown) in the microcomputer 20 as a current setting means. 10 is output.
[0043]
The discharge current setting device 10 converts the voltage value according to the signal as the discharge current value output from the microcomputer 20, and the converted voltage value (V1 in FIG. 2) is the output voltage (in FIG. 1 and FIG. 2). As a), it outputs to the integrator 11 as a voltage-time conversion means and the adder 12 as an addition means.
[0044]
The integrator 11 as voltage-time conversion means receives the output voltage from the discharge current setter 10 and converts it into a voltage that rises linearly with time (b in FIGS. 1 and 2), and as an addition means. Output to the other input terminal of the adder 12.
[0045]
The output voltage from the integrator 11 as the voltage-time conversion means is “zero” immediately after the application of the output voltage from the discharge current setting device 10, and the charge is gradually accumulated in the capacitor inside the integration circuit and output. The voltage rises and the control signal of the timer circuit 4 reaches the maximum output voltage value (V2 in FIG. 2) at time T1 shown in FIG.
[0046]
The adder 12 includes an output voltage (a in FIGS. 1 and 2) from the discharge current setter 10 as a current setting unit and an output voltage (in FIGS. 1 and 2) from the integrator 11 as a voltage-time conversion unit. 2b) and the added voltage (c in FIGS. 1 and 2) is output to the inverter 13.
[0047]
As shown in FIG. 2, the output voltage value from the inverter 13 becomes −V1 at T0, then rises linearly, and becomes − (V1 + V2) at T1 when the discharge is completed.
[0048]
The inverter 13 inverts the polarity of the output voltage (c in FIG. 2) from the adder 12, and outputs the output voltage (d in FIG. 2) with the inverted polarity to the constant current switch 2.
[0049]
The constant current switch 2 controls to flow a discharge current corresponding to the magnitude of the output voltage of the inverter 13 in which the polarity of the output voltage from the adder 12 is inverted.
[0050]
That is, the output voltage value from the inverter 13 becomes V1 at T0 as shown in FIG. 2, then rises linearly, and rises to (V1 + V2) at T1 when the discharge is completed.
[0051]
As for the discharge current at this time, immediately after the dielectric breakdown between the wire 7 and the discharge electrode 9 is performed from the start of discharge, a current of the magnitude of Is shown in FIG. 2 flows, and then the current value increases linearly. When the output voltage value from the inverter 13 reaches (V1 + V2) shown in FIG. 2, a current of magnitude Ie shown in FIG. 2 flows.
[0052]
When the timer output signal reaches T1, the switch circuit inside the constant current switch 2 is turned “OFF”, and the discharge current is cut off. At the same time as the switch circuit inside the constant current switch 2 is in the “off” state, the reset signal Cr from the outside is applied to the integration circuit, and the output voltage of the integration circuit is initialized to “zero”.
[0053]
By controlling the discharge current described in the above embodiments, the discharge energy during discharge can be controlled.
[0054]
That is, the discharge energy P between the tip of the wire and the discharge electrode is generally the product of the voltage E between the wire and the discharge electrode, the discharge current I, and the discharge time T, and is expressed as follows.
Discharge energy P = Discharge electrode voltage E, Discharge current I, Discharge time T (1)
[0055]
From the equation (1), when the discharge electrode voltage E is constant, the discharge current increases linearly with time, so that the discharge energy per unit time also increases linearly with time similarly to the discharge current. .
[0056]
Further, the slope of the output voltage with respect to the time of the integrator 11 is changed by changing the value of the capacitor or the resistor constituting the integrator 11. When the slope of the output voltage with respect to the time of the integrator 11 changes, the slope of the output voltage output from the adder 12 via the inverter 13 also changes, and the magnitude of the discharge current by the constant current switch 2 changes. In addition, the discharge energy can be controlled. For example, by increasing the slope (rate of change) of the output voltage with respect to the time of the integrator 11, the time for generating the predetermined discharge energy is shortened, and thus the discharge time can be shortened.
[0057]
As described above, by increasing the discharge current during discharge with respect to time, the discharge energy generated at the discharge electrode 9 and the tip of the wire 7 can be controlled, and a predetermined ball can be formed. .
[0058]
Further, the discharge time is shortened by changing the slope of the output voltage with respect to the time of the integrator 11.
[0059]
【The invention's effect】
As described above, by controlling the discharge energy at the time of ball formation, rapid thermal expansion of air during discharge does not occur, so that the occurrence of ball scattering can be prevented. Moreover, in order to compensate for the radiation loss from the ball surface during ball formation, small balls with little variation can be formed.
[0060]
Furthermore, since the discharge time can be shortened by changing the slope of the output voltage with respect to the integrator time, the wire bonding time can be shortened.
[Brief description of the drawings]
FIG. 1 is a block diagram of a ball forming apparatus according to the present invention.
2 shows a trigger signal Tr, a timer circuit output signal, a discharge current setter output voltage, an integrator output voltage, an integrator reset signal, an adder output voltage, an inverter output voltage product, and a discharge of the ball forming apparatus shown in FIG. It is a figure which shows each waveform of an electric current.
FIG. 3 is a block diagram of a conventional ball forming apparatus.
[Explanation of symbols]
1 DC High Voltage Power Supply 2 Constant Current Switch 4 Timer Circuit 5 Discharge Ballast 6 Clamper 7 Wire 8 Capillary 9 Discharge Electrode (Torch Rod)
DESCRIPTION OF SYMBOLS 10 Discharge current setting device 11 Integrator 12 Adder 13 Inverter 20 Microcomputer 21 Keyboard execution switch

Claims (3)

キャピラリ先端から送り出されたワイヤの先端と放電電極との間に高電圧を印加することにより放電を起こさせ、その放電エネルギーによりワイヤの先端部を溶融してボールを形成するワイヤボンダ用ボール形成装置であって、
放電電流を設定する電流設定手段と、前記電流設定手段から出力される出力値を受けて、時間とともに直線的に上昇する電圧に変換する電圧−時間変換手段と、前記電流設定手段の出力値と前記電圧−時間変換手段の出力値との加算を行う加算手段とを備え、
前記加算手段からの信号により放電中の電流を制御すること
を特徴とするワイヤボンダ用ボール形成装置。A wire bonder ball forming apparatus that causes a discharge by applying a high voltage between the tip of the wire fed from the capillary tip and the discharge electrode, and melts the tip of the wire by the discharge energy to form a ball. There,
A current setting means for setting a discharge current; a voltage-time conversion means for receiving an output value output from the current setting means and converting it into a voltage that rises linearly with time; and an output value of the current setting means; Adding means for adding with the output value of the voltage-time conversion means,
A wire bonder ball forming apparatus, wherein a current during discharge is controlled by a signal from the adding means. 前記電圧−時間変換手段は、積分回路でなることを特徴とする請求項１記載のワイヤボンダ用ボール形成装置。2. The wire bonder ball forming apparatus according to claim 1, wherein the voltage-time conversion means is an integrating circuit. キャピラリ先端から送り出されたワイヤの先端と放電電極との間に高電圧を印加することにより放電を起こさせ、その放電エネルギーによりワイヤの先端部を溶融してボールを形成するワイヤボンダ用ボール形成方法において、
放電電流を設定する電流設定手段と、前記電流設定手段から出力される出力値を受けて、時間とともに直線的に上昇する電圧に変換する電圧−時間変換手段と、前記電流設定手段の出力値と前記電圧変換手段の出力値との加算を行う加算手段とを備え、
前記加算手段からの信号により放電中の電流を制御すること
を特徴とするワイヤボンダ用ボール形成方法。In a wire bonder ball forming method in which a discharge is caused by applying a high voltage between a tip of a wire fed from a capillary tip and a discharge electrode, and the tip of the wire is melted by the discharge energy to form a ball. ,
A current setting means for setting a discharge current; a voltage-time conversion means for receiving an output value output from the current setting means and converting it into a voltage that rises linearly with time; and an output value of the current setting means; Adding means for adding the output value of the voltage conversion means,
A wire bonder ball forming method, wherein a current during discharge is controlled by a signal from the adding means.
JP04809899A 1999-02-25 1999-02-25 Ball forming apparatus and method for wire bonder Expired - Lifetime JP3932235B2 (en)

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Application Number Priority Date Filing Date Title
JP04809899A JP3932235B2 (en) 1999-02-25 1999-02-25 Ball forming apparatus and method for wire bonder

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Publication number Priority date Publication date Assignee Title
US7347352B2 (en) 2003-11-26 2008-03-25 Kulicke And Soffa Industries, Inc. Low loop height ball bonding method and apparatus
JP5094542B2 (en) * 2008-05-14 2012-12-12 株式会社カイジョー Ball forming apparatus and method for forming wire bonder

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