Cannot comment on "best buy". You'll have to determine what the better machine is for your application and duration of planned use. I suggest taking a field trip to each vendor's nearest demo facility with a few of your most hi-tech boards and stencils. Compare the machines from a structural standpoint by having the vendor remove all the skins and have a good look at the guts. This speaks to durability. Compare the machine GUIs and which is easier to create a printing recipe, record and retrieve printing SPC data, has networkability for off-line programming. Try to bring boards that are very different in size and shape to compare setup and changeover ease/difficulty. Machines vary in how the under board support tooling works. Also, board clamping can be an issue. Some systems use over-the-top board clamping while others use edge clamping for true on-contact printing. Over-the-top tooling is a problem if you have solder lands to print that are right up to the board edge. Bring your paste and print boards over and over again to check repeatability. Find out how each vendor measures repeatability during their QA checking procedures after each new machine is built. Hopefully you've got boards with 0.4mm or 0.3mm fine-pitch devices because that's where you may see a difference in repeatability. Check the post print vision systems to see how many paste formations can be inspected in a given period of time. Some systems are faster than others, therefore providing more inspections per board. Compare the stencil wiping methods too. Machines vary in types of stencil wipers they use. Compare how "smart" the machine is, meaning how much closed-loop feedback there is for various functions. This speaks to how aware the machine is of what its doing- in terms of process control. Be sure each vendor has a solderpaste measurement tool of some sort in the demo facility, such as a CyberOptics LSM, SE 200 or 300 or equivalent and a microscope to view the formations. Watch out for the "blue light specials". Happy shopping!
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