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.

拉线测试(WPT)，或称键合力度拉扯测试，是评价金线键合力度与质量的有效方法之一。方法:在键合金线的下方施加一个向上的拉力使键合部从芯片表面被拉开，并对拉力的大小进行测量。

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.

拉线测试所需设备:拉线测试设备(键合力度拉扯测试设备)，主要由两部分构成，1)由一机械装置驱动一拉钩产生一向上的拉力，2)经校准后的力度测试装置，用来测量金线从芯片表面拉开时的力度。该力度一般用gF(克力)来表示。

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).

目前有多种方法与测试环境对金线键合力度进行测试，但运用最多最广泛的方法是双线键合拉线测试。该方法将拉钩置于已经键合在芯片和封装材料两端的金线下方(即，其中一端为金线与芯片之间的键合点，另一端为金线与封装材料之间的键合点)。拉钩通常置于金线弧度的最高点，拉扯力度方向与芯片表面垂直(若芯片表面为一平面)。

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.

拉线测试装置用于测试金线被拉扯开时代力度，该力度用gF(克力)单位记录。在记录键合力度读数的同时，亦需记录拉线失效模式。拉线失效模式为以下之一:1)第一键合点(金球键合点)被拉起，2)金线颈部断开，3)金线中部断开(指金线弧度与线脚之间--NovHeaven)，4)线脚部分断开，5)第二键合点(楔型线脚)被拉起。其中第一键合点与第二键合点被拉起的模式是不被接受的，需提示流程负责人研究其产生的原因。

拉线测试一般用于半导体封装流程的前段，其为监控生产能力与稳定性的重要标准之一，一般SPC测试中的重要一项。

拉线测试相关国际标准:MIL-STD-883E-2011 (美军标MIL-STD-883E中的方法2011，该标准为非互联网免费共享，需购买)。