For your testing challenges
Lead-free solder or contamaination resulting from the solder process frequently leads to contacting problems, and the pseudo errors associated with them during the process of contacting surfaces with OSP coating. In addition OSP and flux residues tend to accumulate on the plunger tip. In order to keep the contamination on plunger tips to a minimum, and to reliably penetrate the top layer on the soldered points, aggressive tip styles with a specialised palladium-nickel plating developed by INGUN is used.
Selecting the optimum tip style is based on the surface texture of the test point and customer-specific test requirements:
- Pad without solder
- Pad with solder
- Open via
- Closed via
The reliable contacting of test points without solder poses the biggest challenge. The tip style 70, which is characterised by its asymmetrical, sharp-edged cutting geometry, was developed specifically for pads. Moreover, the tip of the plunger is significantly smaller in comparison to other tip styles, which leads to deeper penetration of the tip into the PCB at the same spring force due to higher contact pressure. This interplay enables the reliable penetration of tough top layers. Image 1 shows how the edge of tip style 70 penetrated into the surface of the pad. A clear depression and displacement of material can be seen. This results in reliable contacting.
We recommend tips styles 38, 91, 97, and 98 for pads with solder and open vias. Tip styles 38, 97, and 98 from the INGUN E-TYPE® FUSION range are available for closed vias. Overview Tip Style Test Probes
Increased First Pass Yield
For reliable contacting
When contacting test points, first of all it is important to achieve reliable contact. Furthermore, consistent resistance, kept as low as possible, is required to perform measurements which are both precise and repeatable. The following chart shows results from measurements performed on OSP-coated PCBs. The measurements were conducted up to 50,000 test cycles in the INGUN testing laboratory. During the test, the behaviour of tips style 70 on pads without solder, tip style 98 on open vias, as well as tip style 38 on pads with solder was examined.
Image 2 shows the tip styles selected for the test all achieved reliable contact with the test point. The first pass yield, contact achieved during the first test cycle, is over 99 % in each case. This leads to significant cost and time savings in the test field.
The signal quality chart (see image 3) shows the measurement accuracy achieved on each test point with OSP coating. The resistance values are considerably lower than 50 mΩ, which enables precise measurement. Furthermore, measurements at these low resistance values exhibit only slight fluctuations. The test probes in the INGUN E-TYPE® FUSION series achieve an ideal compromise between signal quality and reliable contact thanks to their features, which enable reliable contacting of tough surfaces.
With regard to the mechanical wear on the test probe, the probes were in good condition and fully functional after 50,000 test cycles, see images 4 and 5. Minimal deposits can be seen on the edge of tip style 70. However, these are not in the area of the contact zone, which means good signal quality is still guaranteed.
For the best edge-retention properties
The palladium-nickel plating, which was specifically developed for the test probes in the INGUN E-TYPE® FUSION series, are characterised by a surface hardness value three times higher than standard gold plating. With these characteristics solid layers of contamination and top layers, such as OSP can be penetrated without the tip style losing its edge-retention properties, and ultimately its aggressiveness. Another positive effect of the plating is that it repels contamination, which reinforces the self-cleaning effect of each tip style – for unimpaired contact.
Increased Contact force
For reliable penetration of the test surface
The INGUN E-TYPE® FUSION test probes based on the established INGUN E-TYPE® technology and enables the highest contact reliability on the PCB without subjecting it to excessive stress. This provides a 100 % higher contact force when impacting the test surface, which is achieved by the increased spring pre-load. The FUSION test probes, however, have the same spring force at working stroke as a standard test probe (GKS), see image 6. The additional contact force initially gained ensures reliable penetration of insulated top layers and a contact surface between probe and PCB which is up to 25 % larger due to the penetration depth.