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Don’t Get Stuck Without Coverage! USBid, Inc. and AAA Test Lab Solderability Testing

The process of designing a circuit is a painstaking business. You spend many long hours making sure your product works just right. But what if the electronic components you want to put on your circuit board don’t respond to the soldering process? You will have wasted valuable time and money along with putting your company’s reputation in danger.

That’s why USBid, Inc. offers its customers Solderability Testing for both RoHS and non-RoHS devices through the AAA Test Lab.

What is solderability?

Solderability is the measure of how well the electronic component will respond to the soldering material.

What is solderability testing?

Solderability Testing examines the terminations of devices including component leads, lugs, terminals, and wires for their suitability to be electrically connected to a circuit using solder.

What industry standards reference or require solderability testing?

Solderability testing is described by the following industries:

1) The United States Department of Defense outlines their extensive test method standards for microcircuits for military and aerospace use. Solderability testing requirements are described in Method 2003 of Mil-Std-883. The Mil-Std-883 Method 2003 is one of the oldest and most widely used standards for solderability testing. This tried-and-true method is relied upon for the safety and security of our nation’s military and space operations.

2) The joint standards of IPC (Association Connecting Electronics Industries) and JEDEC Solid State Technology Association use J-STD-002D to describe the solderability testing they require for component leads, terminations, lugs, terminals and wires. This standard defines what constitutes a defective part and an acceptable part. This joint committee recognized that storage can affect the solderability of a component so they encourage solderability testing after storage or right before the part is to be put into use.

3) IPC (Institute of Printed Circuits) also developed industry standards for assessing the solderability of printed boards. These standards as describd in IPC J-STD-003 is applicable to printed boards that will be used in consumer products like computers, business machines, life support machines, and flight control systems.

4) International Electrotechnical Commission has outlined the international standards for solderability testing in Part 21 of the IEC 60749. This standard outlines the dip & look method, but also allows for a board mounting solderablility test.

Regardless of what industry you are a part of, it is vital that you take the necessary steps to go through solderability testing. What are the two most common methods of solderability testing? There are two tests commonly used to determine solderability. One test is qualitative. The other is quantitative.

The most common is the Dip & Look Method. The Dip & Look Method is used in the AAA Test Lab and is commonly used in process QA and reliability monitoring, as a qualitative test process that passes or fails based on the physical and visual attributes exhibited by the sample.

The second most common solderability test is the Wetting Balance Analysis. Wetting balance analysis is a quantitative test used primarily as an engineering tool to measure the wetting forces imposed by the molten solder on the test surface as it is dipped and held in a solder bath as a function of time. The time it takes to go from a non-wet starting condition until wetting occurs (i.e. solder starts to flow) is used to evaluate solderability, although no industry specifications for wetting balance analysis exist, which is why it is not used as a production monitor.  Wetting force depends on the density and surface tension of the solder.

How is the Dip & Look Solderability Test actually performed?

First, you need the right equipment. At the AAA Test Lab we have a solder pot of sufficient size that can maintain solder at a specified temperature, a dipping mechanism capable of controlling the rates of immersion and emersion, as well as dwell time, of the terminations, an optical and lighting system that facilitates inspection at a minimum magnification of 10X, and steam aging equipment for 'aging' the samples prior to testing.

Once the AAA Test Lab materials are gathered, the solderability test begins.

1) First, the tester does a visual inspection per IDEA-STD-1010-B. The inspector does not wipe, clean, scrape, or abrasively clean the terminations to be tested so that the test is accurately measuring the solderability of the terminations as they are.

2) Then the flux is applied to the terminations.

3) Next comes the solder dipping which consists of immersing non-RoHs terminations in static solder at a uniform temperature of 240 +/- 10o C and RoHS terminations at 250 +/- 10o C.

4) Once the terminations have been “dipped,” then come the “look.” The terminations are examined at 10-15X magnification.

What is the tester looking for under the microscope?

The tester is looking for how completely the solder covered the terminations. The main criterion for acceptable solderability is 95% coverage of the dipped portion of the terminations by a new and continuous solder coating.  Thus, pinholes, voids, porosity, nonwetting, or dewetting must not exceed 5% of the total dipped area.

What does acceptable coverage and nonconforming coverage look like?

Below are samples of acceptable and nonconforming parts. In the first set of photos the pre-dip leads exhibit no scratches, oxidation or foreign matter. The resulting solderability test satisfactorily wet and covered the leads with a continuous coating of solder.

Acceptable

Figure 1. Pre-Dip Leads in Good Condition Figure 2. Acceptable Solder Coverage of Leads

The next set of photos were taken from a BSS199 Siemens Transistor and enlarged to better illustrate the lead condition. The pre-dip visual inspection of the leads reveal pitting, scratches and discoloration that could be the early stages of oxidation. The resulting dip test clearly displays the erratic solder coverage of the leads. This product is nonconforming and should be rejected due to the voids and nonwetting of the terminations.

Nonconforming

Figure 3. Pre-Dip Leads with Scratches and Pinhole Figure 4. Nonconforming  Solder Coverage

The leads on this device did not properly wet and the solder did not properly flow resulting in nonuniform coverage. The discoloration of the solder indicates contamination possibly caused by scratches.

Don’t get stuck with electronic components that will not pass a solderability test. Take advantage of USBid, Inc. AAA Test Lab to get quick and accurate feedback. Contact USBid, Inc. today to find out more.

 

Author   by Admin
  December 19, 2017

 

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