PCB007 Magazine

PCB-Apr2015

Issue link: https://iconnect007.uberflip.com/i/490885

Contents of this Issue

Navigation

Page 37 of 76

38 The PCB Magazine • April 2015 FeAture product will not perform as required. Figures 4 and 5 show the final assembled fixture. Final QC and Test Setup This is the final phase of the process. The fixture is setup up on the test machine and test- ed for proper operation. The wiring is verified and if any faults are found they are corrected. The unit under test (UUT) is then introduced to the fixture. Due to the extreme density and re- quired precision of the alignment two different methods are incorporated. Typically for a sub- strate fixture an optical alignment process us- ing pre-determined fiducials is used. This views the UUT once placed on the test head and can make corrections in both X, Y and Theta. For HDI fixture, either the process is the use of an electrical alignment system where an electrical stimulus is applied to pre-determined features on the actual UUT or a combination of both is used. Again, X, Y and Theta corrections can be made to guarantee proper and accurate probing of the features of the UUT. Once this process is complete the fixture is ready for production use. Summary As can be seen above the HDI and substrate fixture technology is truly an art form. Long gone are the luxuries of just using a plated drill file on an old drill machine and automatically dropping pins. Even the multi-plate fixtures that are used today have no comparison to the criti- cal manufacturing requirements of the HDI and substrate fixtures. North America has yet to see much of this type of volume testing at the bare board level but in Asia it has become common- place. I was able to witness this type of technol- ogy while visiting a few shops in China. Watch- ing the sheer volume processing utilizing auto- mated equipment and HDI/substrate fixturing was very impressive. The care and attention to detail required to successfully manufacturer and further test this type of product is truly for the patient and steady handed engineer/technician. This is the wave of the future as chip packages- get smaller and smaller. Just think, as the pins get down to 25 µ the human eye will have trouble even seeing this pin without magnification and since the human hair is roughly 70 µ we will truly be splitting hairs! PCB SPLITTING HAIRS: THE MANUFACTURE OF HDI AND SUBSTRATE TEST FIxTURES continues Figure 4: assembly. Figure 5: assembly. Todd kolmodin is the vice president of quality for Gardien Services uSa, and an expert in electrical test and reliability issues.

Articles in this issue

Links on this page

Archives of this issue

view archives of PCB007 Magazine - PCB-Apr2015