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Paste Dispensing



Paste Dispensing | 10 January, 2002

Okay, I've read about the pros and cons about solder paste dispensing. Now, I have a Camalot 3800 and I want to experiment about dispensing solder paste. I have a needle gauge of 25GA, 23 and 22. My pcb components are; RC 0603-1812, Size B, C and D Tant Caps, SMB Diodes, SOT23, SOT89, D2PAK or TO260, PLCC32, PLCC44, QFP100 - 0.65mm pitch, QFP112 - 0.5mm Pitch, SMD Xtals, SOIC8, SOIC14, SOIC16, SOIC20W, SOIC32, AND PBGA256. My CAMALOT3800 is equipped with a 642 Pump so I can use 2 different needle sizes to run the Show. Which combination of needle sizes will suit all my components for dispensing ? My needles come with a stopper. What other setting do i need to take note (e.g. dispensing height, shotsize etc.) ? What are the most problems that I will be facing during the run ? What is the best S. Paste mesh Size to use for the above ?

If you still have some important pointers to share....they are more than welcome !

Thanks and regards, Dreamy

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Paste Dispensing | 10 January, 2002

My recomendation is to contact a Speedline Technologies- Camalot applications engineer or customer service. One apps. eng. is Jim Kaler

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Paste Dispensing | 10 January, 2002

You are sure taking you sweet time getting this thing running. You're getting too much beach time.

NOZZLE SELECTION Typically, the only rule of thumb that applies to choosing the correct nozzle ID is that it should be one half of the required dot diameter.

Dispensing solder paste & silver epoxy Needle||Inner||Possible dot gauge||dia [mm]||range [mm] 21||0.510||0.765-1.000 22||0.410||0.615-0.820 23||0.330||0.495-0.700 25||0.250||0.375-0.570 27||0.200||0.300-0.500 28||0.180||0.270-0.450

PASTE SELECTION Once you'll go over 24 gauge (25, 26); you'll need 400-500 mesh. Some say: Mesh||Particle size mm||Needle gage||Pitch -200/+325||0.043-0.074||21 or less||standard -325/+500||0.036-0.043||23 or less||fine -400/+500||0.036-0.038||25 or less||fine

We don�t use anything but 400-500. Camelot says that the inner needle dia should be minimum of 8x the ball [solder] size.

PASTE VOLUME Volume of solder dot = 0.26*d^3

PROBLEM RESOLUTION * Unrepeatable dot size ||Incorrect needle gauge ||Incorrect shot size ||Incorrect dwell time ||Incorrect needle gap ||Bent needle ||Old material [viscosity change] ||Unrepeatable valve [one that uses air pressure to dispense] * Throughput is slow ||Needle size is smaller than necessary ||Dot dispense order is inefficient ||Up height is too great ||Dwell time is too long ||Valve park position is too far away

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