WirePullTesting

WirePullTesting概述

Wire Pull Testing (WPT), or bond pull testing, is one of several available time-zero tests for wire bond strength and quality. It consists of applying an upward force under the wire to be tested, effectively pulling the wire away from the die.

拉線測(cè)試(WPT)，或稱(chēng)鍵合力度拉扯測(cè)試，是評(píng)價(jià)金線鍵合力度與質(zhì)量的有效方法之一。方法:在鍵合金線的下方施加一個(gè)向上的拉力使鍵合部從芯片表面被拉開(kāi)，并對(duì)拉力的大小進(jìn)行測(cè)量。

Wire pull testing requires a special equipment commonly referred to as a wire pull tester (or bond pull tester), which consists of two major parts: 1) a mechanism for applying the upward pulling force on the wire using a tool known as a pull hook; and 2) a calibrated instrument for measuring the force at which the wire eventually breaks. This breaking force is usually expressed in grams-force.

拉線測(cè)試所需設(shè)備:拉線測(cè)試設(shè)備(鍵合力度拉扯測(cè)試設(shè)備)，主要由兩部分構(gòu)成，1)由一機(jī)械裝置驅(qū)動(dòng)一拉鉤產(chǎn)生一向上的拉力，2)經(jīng)校準(zhǔn)后的力度測(cè)試裝置，用來(lái)測(cè)量金線從芯片表面拉開(kāi)時(shí)的力度。該力度一般用gF(克力)來(lái)表示。

There exist many variants or test conditions for performing the WPT, but the most widely used test condition for conventional wirebonded devices is the double-bond wire pull test. This procedure consists of applying the pull hook under a wire that is attached at both ends (say, one end to a bond pad on the die, and the other end to the bonding finger or bonding post of the package). The pull hook is usually positioned at the highest point along the loop of the wire, and the pulling force is usually applied perpendicular to the die surface (vertically if the die surface is horizontal).

目前有多種方法與測(cè)試環(huán)境對(duì)金線鍵合力度進(jìn)行測(cè)試，但運(yùn)用最多最廣泛的方法是雙線鍵合拉線測(cè)試。該方法將拉鉤置于已經(jīng)鍵合在芯片和封裝材料兩端的金線下方(即，其中一端為金線與芯片之間的鍵合點(diǎn)，另一端為金線與封裝材料之間的鍵合點(diǎn))。拉鉤通常置于金線弧度的最高點(diǎn)，拉扯力度方向與芯片表面垂直(若芯片表面為一平面)。

The wire pull tester measures the pulling force at which the wire or bond fails. The measured force is then recorded in grams-force. Aside from the bond strength reading, the operator must also record the bond failure mode. Failure mode in this context refers to one of the following: 1) first bond (ball bond) lifting; 2) neck break; 3) midspan wire break; 4) heel break; and 5) second bond (wedge bond) lifting. First or second bond lifting is unacceptable and should prompt the process owner to investigate why such a failure mode occurred.

拉線測(cè)試裝置用于測(cè)試金線被拉扯開(kāi)時(shí)代力度，該力度用gF(克力)單位記錄。在記錄鍵合力度讀數(shù)的同時(shí)，亦需記錄拉線失效模式。拉線失效模式為以下之一:1)第一鍵合點(diǎn)(金球鍵合點(diǎn))被拉起，2)金線頸部斷開(kāi)，3)金線中部斷開(kāi)(指金線弧度與線腳之間--NovHeaven)，4)線腳部分?jǐn)嚅_(kāi)，5)第二鍵合點(diǎn)(楔型線腳)被拉起。其中第一鍵合點(diǎn)與第二鍵合點(diǎn)被拉起的模式是不被接受的，需提示流程負(fù)責(zé)人研究其產(chǎn)生的原因。

拉線測(cè)試一般用于半導(dǎo)體封裝流程的前段，其為監(jiān)控生產(chǎn)能力與穩(wěn)定性的重要標(biāo)準(zhǔn)之一，一般SPC測(cè)試中的重要一項(xiàng)。

拉線測(cè)試相關(guān)國(guó)際標(biāo)準(zhǔn):MIL-STD-883E-2011 (美軍標(biāo)MIL-STD-883E中的方法2011，該標(biāo)準(zhǔn)為非互聯(lián)網(wǎng)免費(fèi)共享，需購(gòu)買(mǎi))。