|
|
|
|
|
|
|
||||||||
The Best Method for Reworking Ultra-Micro Chips
Board Talk
|
||||||||
TranscriptPhil And welcome to Board Talk with Jim Hall and Phil Zarrow, The Assembly Brothers, pick and place. We are here to discuss process, situations, problems, dilemmas and remedies. Jim, today we have a question from TG. We are struggling to solder and rework small parts, 0201s and 01005s. I have been using the small nozzle hot air solder rework station with adjustable air flow. The minimum air flow on the unit will blow small parts across the workbench in the blink of an eye. My world of reworking small packages with lead-free solder is painful. I am open to any suggestions that you might have. Jim, what do you think we could do to help eliminate TG’s pain here? Jim As in many cases dealing with these ultra-micro chips, you are probably going to have to buy some new hardware, some new tools. You mentioned the minimum air flow on the unit you are using will blow the small parts away. I would venture a guess that when the unit you are using was designed, 01005s didn’t exist. When they were setting a minimum air flow they had no idea that was not low enough. Which raises the question, is hot air the best tool to use for these chips? It is like so much of the whole process with these small chips. The steps are the same, but the degree of difficulty because of their size in this case very low mass and weight, just makes them very difficult. Many people, addressing repair, feel that it is not practical to handle these manually with tweezers or anything. They can be cracked or damaged too easily. You need at least a semi-automatic vacuum pick up with remote movement so that human hands don’t actually touch the parts. The best way to actually reflow them? I really don’t know. Maybe IR, infrared. Maybe a small, specialized soldering tip, like these little fork-shaped tips that have been used at times. Maybe that is the best, I don’t know. I don’t know but I would look for modern, relatively new rework stations that have been designed specifically to handle these parts. It is like everything else, you have to change your process to deal with these. In printing, we have to go to thinner stencils. Go back to paste, we have to paste with smaller particles, type 4 and type 5, to get through these small apertures. We have to optimize our printing. Maybe put nano coatings on our stencils. We have to get special nozzles. Some older placement machines don’t have the accuracy to deal with these parts. Probably the most obvious is AOI. Older AOI machines, the cameras on them just don’t have enough resolution. You don’t get enough pixels on the solder joint to give you a robust image that you can accurately evaluate. So, you have no choice but to get a new machine or at least a new camera with finer resolution. That is what TG unfortunately is dealing with here. These things are painful. These are incredibly difficult. Phil There are a number of stations out there that use infrared. They have been out for a long time. This may be a good time to step up to the plate and look at those as well. You look around and you will see some other solutions, including possibly even robotic approaches. I don’t know how you decide who is going to be the poor person to rework these things, but I certainly wouldn’t want to be doing it. Jim They are problematic throughout the process. They are so tiny, you can’t see them with the naked eye. You have to use magnification, in many cases higher magnification than you have been using in the paste. All of the above can apply to the rework process. There are so many steps, take it apart, remove it, clean the pads, place paste or flux down, place the part, reflow it successfully, all without the damaging the adjacent parts. If there are multiple micro-chips and they are close together, the spacing between them is only a couple of mils. Reworking them is just going to be difficult. You are going to have to work it out, what works best for you. I’m afraid you are probably going to have to buy some new equipment. Phil One thought is, you might find the designer who actually designed these and bring him down. Sit him down, give him a tweezer and say here you give it a shot. This is again another example of designing for repairability. It is one thing to design these in with all of the foibles that Jim mentioned, but when you have to rework them, it is an additional hell. You’ve been listening to Board Talk with Jim Hall and Phil Zarrow. Jim has imparted a great deal of wisdom on this subject. No matter how you are reworking those little buggers, just don’t solder them like my brother. |
||||||||
Comments
|
||||||||
|
|
|
|
|
|
|