Our ICT Guy here at my company loves to use lots of via holes as test points - via holes which are 0.040" diameter, and spaced at 0.004" edge to edge spacing! He doesn't like to tent the via's either, so I always battle via-to-via shorts at the wave on an almost daily basis.
Any knowledgable ICT Engineers out there who know of a probe style that can pierce through tented via's? I am trying to get my company to make a PCB Fab change requirement that all via's used as test points must be tented.
Samir, From experience, the only board test situation where tented via's have difficulty with contact is with a Flying Probe type tester. Otherwise, for traditional ICT, the force of the pogo pins, correct probe type, and fixture design should do the trick with regards to piercing through the solder resist.
Otherwise, to overcome your problem at wave solder, try slowing the conveyor speed to reduce the contact length and optimize peel back. Also, is your wave inerted? Common problems associated with non-inerted waves is via-via bridges.
Well, im not sure what plane you guys are on, but I can back up my what im talking about. Ya see I wnet to Soltec traingin back in 1995 for our new wave. I got a diploma proofing that I know what i'm talking about. no one else in my company has one cause they wopuld let me know. And since i got 12 years of exeperince operating this machine it makes me the Master. Some of the ladies on my shift even call me that. One of the supervisors on days even says im the master of the SOltec. I can even run the new Vectras machines we bought. Althuough this new windows software is about as complicated as our fax machine. Give me the dos anytime as it controls the wave perfectly. In fact we run all our thru hole product on my machine since top side wetting is so hard to do. I run about 20 different boards styles on my machine that are all thru holes with no problems. They run the SMTs on the Vecras cause SMT is easier since its a newer process. Heck they even hired a new engineer to take over them waves. He thinks hes pretty smart since he went to school and has a couple years experience at other companies. The old guy that was in charge of waves was perfectly good. He'd listen to me about waves and hardly have to be out here 3 or 4 hours a day to get all 3 machines running smooth. Even then he'd spend most of the day surfing web on this computer. This new guy came in and chased him away. Now he thinks getting rid of wave touch up people is the right thing to do. Taken theyre jwabs.
Anyway, about ICT. I see these machine run too. Our ICT guy says he needs all the vias on the bottom of the board soldered. So I reduce the flux cause he says he has to clean the flux off his pins. Then I slow the conveyor so the heaters don't dry up the flux. Then I lower the wave cause I get shorts going this fast. We only have 2 or three spots to touch up on the boards but we pass ict. Listen, most educated engineers won't understand this, but then they didn't go to Soltec college either.
You're a piece of work! Why don't you work for any of the major wave companies? So how does slowing the conveyor speed eliminate drying flux? And when you slow it down, what speeds it up to make you say "I lower the wave because I get shorts going this fast".
Your new guy that wants to get rid of post wave touch-up just happens to be right. You lose money repairing assemblies and having extra people get paid to find and eliminate defects.
Get rid of your 2-3 defects per board and THEN You're a "Wave Master"