Electrical Test

As a China PCB Manufacturer, E3PCB has been spending full energy in striving for the high quality of printed circuit boards while keeping the PCB production cost-effective. 100% electrical test has to be performed on each piece of PCB boards prior to their playing a real role in customers’ projects just to guarantee the smooth implementation of optimal performance and functions, which has been a crucial link in our PCB fabrication process.

Electrical test mainly comes in circuit Continuity and Isolation test. Due to increasing density of board traces, electrical test is covering from increasingly higher difficulties so that the advent of new types of test technologies is embraced for compatibility with the development of PCB industry.

• Continuity test refers to a process to check whether resistance value between nodes within the same netlist is less than continuity threshold so as to verify disconnections that are usually called opens.
• Isolation test refers to a process to check whether resistance value between nodes of different nets is more than isolation threshold so as to verify shorts.

As the improvement of electronic technologies and increasing complexities of electronic products, gone are the days when only visual inspection is relied on since visual inspection only works relatively well for double-layer PCBs or multi-layer PCBs prior to lamination. Nowadays, with the development of vias such as blind/buried vias, it’s difficult for visual inspection to reach that far.

In E3PCB, two primary electrical test methods are being applied: Bed of Nails Fixture Test and Flying Probe Test. For either method, guidelines in accordance with IPC 9252 are rigorously adhered to so that reliability of end products will be fully guaranteed.

Bed of Nails Fixture Test

Bed of nails fixture test, also called a calm shell or universal grid, is implemented through dozens of stiff testing fixtures just like what its name is described.

Fixtures with springs are connected to each test point on each circuit board. Springs are capable of equipping each test point with pressure of 100g to 200g to ensure excellent contact of test points. Such fixtures that are arranged in a matrix manifest themselves as a bed of nails. Controlled by test software, programming should be carried out on test points and test signals, through which testers are allowed to obtain information concerning all test points. To implement this test, fixtures will be selected and assembled according to distribution and positions of test nodes or points on a board.

Flying Probe Test

Depending on moving probes to test electrical performance of each net on a bare circuit board, flying probe tester is actually an upgrading version of bed of nails tester. With fixtures replaced by probes that can move at a high speed, the min test pitch of a flying probe tester can be as small as 0.2mm.

During testing, unit under test (UUT) is conveyed to the inside of tester through belt or other transfer systems. Probes are then fixed to make them contact with test pad and vias. In this case, a single component of UUT can be tested through connection between multiplexing system, drivers and sensors.

Flying probe test is responsible for testing of shorts, opens and component values. Furthermore, a camera is equipped on the tester to find lost components and inspect components in terms of their shape, polarity and capacitance. Therefore, it is fit for both bare PCB fabrication and electronic assembly.

Either bed of nails fixture test or flying probe test, the tested items mainly cover from opens, shorts, capacitance to resistance in a circuit on each bare board. In addition, some reports can be summarized through testing results including cross section, solderability, peel strength etc. so that ideal performance and all functions of bare boards can be totally realized in your practical projects.

Free PCB Inspection Will Be Carried Out on All PCBs Manufactured by E3PCB

As a company certified by ISO 9001:2008, E3PCB conforms to the most rigorous quality management standards and regulations in circuit board manufacturing process. Electrical test is a critical link connecting in-house PCB manufacturing and customers’ projects, we automatically carry out electronical test on all circuit boards before shipping them out. If your required test items aren’t covered, please send us a message. We’ll work out a solution at very short time.