Substrates are used to enable a connection between a semiconductor and a printed circuit board. A typical test panel consists of about 50 to 100 single substrates and has a size of approximately 250 mm x 80 mm. Each substrate has about 1000 to 2000 test points requiring about 100,000 pads being contacted to achieve 100 % continuity and isolation testing. For testing substrates on semiconductor side, structures as small as 10µm have to be reliably contacted.
To meet this challenge the S3–8 utilizes eight freely moveable test heads and achieves a test rate of 100 ohmic two-point measurements per second. Optionally the test system can be fitted with a vacuum table for a capacitance based test.
Prior to electrical test, an optical alignment of the test sample correlates the shrinkage and offset of the finished product with the testing data and adjusts automatically. Two 5 Megapixel color cameras with a resolution of 1.2 µm ensure positioning accuracy of ±1.5 µ. The S3 systems work with a micro needle with a contacting pressure that is programmable from 0.3 g up to 2.5 g to ensure best test yield and repeatability without damaging the contact pads. The maximum test area of the substrate tester S3–8 is 350 mm x 310 mm (13.8” x 12.2”).
Jochen Kleinertz, vice president PCB Test Group at Xcerra explains: “Today’s established test systems are mostly single sided and therefore do not allow 100% ohmic continuity tests. However, more and more customers are asking for this type of test. The expertise of atg Luther &Maelzerin double sided test systems together with the unique multi head technology makes outstanding accuracy, speed and throughput possible. We expect that this high throughput capability will enable double sided testing of substrate boards with flying probe test systems despite the high test point counts. This will allow our customers to use new test options for high end substrate boards, which were not available in the past.”
