Why Solderability Test?

One reliable method is to check components with a solderability tester. Several international standards exist for this method. These systems test components for solderability, preferably during incoming inspection. If the results are good, the components are passed on to the production area. When the results are unacceptable, the entire lot can be returned to the manufacturer or distributor for replacement. Alternatively, the company can order from another, more reliable source before a lack of components disturbs production.

If no action is taken to test the wettability of the components, the risk is that product will not pass functional test at the end of the production cycle because of bad solder joints. The defective units need expensive repairs or they cannot be reworked. Rejects and field failures easily can exceed the investment cost of a solderability tester.

The Solderability Tester

The solderability test is performed easily with modern PC-controlled measurement equipment. First, all component-relevant data and test parameters are placed into a screenmask. Next, the component is clamped to a holder and fluxed. The holder is placed into the tester and fixed. The test begins and the system's software takes all test data, showing the test curve together with the data of the standard norm chosen to determine solderability. The test should be performed with approximately 10 sample components from the same component lot to provide a mean value.

Microtronic's LBT-210 solderability tester has software that offers statistical information such as mean value, standard deviation, etc. A camera option offers video of the test cycle and storage in memory with the appropriate test measurements and data. Additionally, it has the feature to test under nitrogen. This function can be switched on in the software. An enclosure that is flooded with nitrogen lowers and rises with the device under test.

Measurements

The most common method is a test using a solder pot filled with the same alloy that is used in the production line. Solder pots are interchangeable when more than one solder alloy is in use. The device to be tested lowers with a defined speed into the molten solder. The exact position of the surface of the solder bath is determined by non-contact laser sensor. A scraper removes all oxidation from the surface of the molten solder prior to each test.

Initially, dipping the test specimen into the molten solder causes solder displacement because the test specimen is at room temperature and the solder is not wetting the part yet. The displacement force is already measured. After the test specimen has reached the solder temperature, the wetting begins. The solder flows up the test specimen and the strong surface tension of the molten solder pulls the specimen down. These forces are measured precisely and are shown in a force-time curve on the monitor. All previous time data is available in a listing. The software calculates the measurements and provides the wetting force or meniscus angle.

This value can be compared to the values of other specimens. The advantage of the software is that it compares the data of earlier (or future) tests of the same component from the database to show a quality trend. A further test with a molten solder ball, known as a "globule" test, also is commonly used. The test sequence is similar to the solder pot test. Oxide must be removed from the molten solder ball using flux. The test specimen is placed over the middle of the globule by motorized X- and Y-axes. The globule must be replaced after each test. Solder particles of different alloys from 1-4 mm are offered with the system.

 Microtronic Solder Test Details Screen

Microtronic Solder Test

Standard Test Cycle

Revolutionary New Test Method

A revolutionary new method is available that tests using solder paste and a temperature profile. A component is placed on printed solder paste and heated through the same temperature profile that is used in production. All force parameters and values during the heating cycle are monitored and saved. This is the only known existing method of simulating and qualifying the solder profile of an in-line production solder furnace in conjunction with different solder pastes and components. The software is straightforward and allows the use of comprehensive component lists. The appropriate data sets can be generated, saved and edited for later use.

As an additional benefit, all results can be found at any time and shown in the required standard norm. Many international standards are supported by the system, and custom standards can be generated and used in the system easily.

A further function allows the measurement curve and all the measurement data to be exported in other applications. This function makes it simple to prepare reports and presentations (as PDF files that can be sent via e-mail, etc.). The printout includes all measurement parameters, curves and value listings.

If the system's computer is connected to a network, all test data can be stored on a central server and retrieved by individuals. This is significant for companies that have multiple locations because all results can be compared amongst all users over extended time periods, further increasing quality assurance levels.