BONDTESTER

What force load cells do I need for HS testing?

admin — Mon, 27 Aug 2007 17:29:04 +0100

The 4000HS machine comes equipped with work holders for solder bump shear and cold bump pull and 5kg load cells. Current understanding indicates that 5kg is more than adequate to detect brittle fracture failure (BFF), where only single bumps are being tested.

Suppose that I want to do zone shear at high speed?

admin — Mon, 27 Aug 2007 17:30:01 +0100

Zone shear is done at much lower speeds than those typically used on the 4000HS and this test is best carried out on 4000 machine. You will however need a high power XY stage and a 100kg load cell.

If you are only doing zone shear it is most sensible to upgrade or buy a suitably modified 4000 machine, rather than buy a 4000HS.

How can I know that the high speed machine is working at the correct speed?

admin — Mon, 27 Aug 2007 18:35:11 +0100

One of the output screens which can be chosen shows a trace of the velocity throughout the test. Sometimes there may be a very slight difference between the chosen value and the actual value represented in the trace. For example, a value of 1m/s may have been input but the reading from the trace is 0.98m/s. You can adjust subsequent tests to exactly 1m/s by inputting a slightly higher value in the set-up, 1.05m/s say.

How can I clear the balls before performing a high speed single ball shear?

admin — Mon, 27 Aug 2007 18:36:17 +0100

One option is to use a shear tool at a much lower speed (around 5 to 10mm/s). The alternative is to use the DAGE ball clearance jig – contact us for more details. This machine has been custom built to accommodate a wide range of device sizes and easily removes all the balls except for a single row. Remember that it is important to remove the balls cleanly from the device; otherwise debris could interfere with passage of the shear tool during the test itself and compromise the results.

What is a bond shear test?

admin — Mon, 27 Aug 2007 18:37:35 +0100

A process that uses a chisel shaped tool to shear ( push) a ball or wedge bond off a bond pad to indicate the quality of the metallurgical joint between the wire and bond pad metallization.

What do we mean by UFP, Ultra Fine Pitch?

admin — Mon, 27 Aug 2007 18:38:08 +0100

A UFP is used to define a bond pad pitch ( distance between the center of 2 adjacent bond pads on a silicon chip) of less than 50 microns. Sometimes the term "small geometry" is also used.

What is Brittle Fracture Failure (BFF)?

admin — Mon, 27 Aug 2007 18:38:54 +0100

Solder ball joint integrity has always been an issue, but never more so than with the introduction of lead-free solder. Research has noted that lead-free joints can be particularly susceptible to brittle fracture at the ball-to-pad interface. These failures can occur over the full life-cycle of a solder joint from manufacture to test and handling and finally, through its life as an end-product.

With the introduction of lead-free solder alloys, brittle fracture failures have increased and many electronics industry assemblers and OEMs have acknowledged that urgent attention is required to address the issue. Though the change to lead-free solders has brought more attention to the brittle fracture failure mode, it is a demonstrated reliability concern with many other solder alloys and pad surface finishes.

What is Zone Shear or Total Ball Shear?

admin — Mon, 27 Aug 2007 18:41:44 +0100

Zone shear is a method for shearing many solder balls in one pass of the shear tool. Either one row or many rows can be sheared in one pass. This can be done at high speed, typically 1m/s, but preferably it is carried out lower speeds such as 5mm/s. Compared with high speed single ball shear, zone shear yields poor reproducibility and only semi-quantitative information on bond strength. Failure mode must be assessed subjectively. See Zone shear page.

How does the High Speed Shear Test Procedure differ from normal shear test?

admin — Mon, 27 Aug 2007 18:42:42 +0100

High speed testing takes place at speeds up to 5000x faster than normal shear testing. In order to achieve these speeds, a slightly different set up is needed from conventional shear testing. Essentially, the sample must be accelerated towards the shear tool for the test and decelerated following the test. Therefore the area approaching and following the test ball must be cleared. See question 4 above.
The sequence of events during the test is shown diagrammatically below.

The tool is aligned to the solder ball in the normal manner and the test is initiated. A normal landing and step-back (to the pre—programmed shear height) will be completed. The sample then moves away to a distance calculated by the software. From this position the sample then accelerates to the constant test velocity and the test takes place. Following the test, the work holder decelerates to a halt.

How does the High Speed Cold Bump Pull (CBP) test procedure differ from the normal CBP test?

admin — Mon, 27 Aug 2007 18:43:12 +0100

Pull testing at high speed also requires a different setup than conventional pull testing. Because the clamping jaws must have contact with the ball, an acceleration distance between the jaws and the sample is not possible. Therefore constant velocity is achieved by accelerating both loadcell and work holder together (the jaws to bump connection joining the two).

Pull Test Procedure:
1. In this test the alignment is identical to conventional low speed testing.
2. When initiating the test, the jaws descend and grip the ball.
3. The jaws then accelerate to the target velocity pulling the sample with them. The acceleration load on the bond is kept slightly negative (compression) during the acceleration by an air driven piston which drives the work holder and sample upwards.
4. In its upward travel there is sufficient height for the work holder to reach the target velocity; the work holder then confronts a hard stop and the jaws continue moving at the test speed pulling the ball as they do so. The test is complete.