Indium Corporation - Mailchimp

Dispensing Die-Attach Solder Paste

The picture shows a “Dispensing Component Kit”. I find this is extremely helpful in quickly verifying your powder/needle combination. This particular kit is put together by EFD.

As pitches and solder volumes decrease with overall package size, so do paste deposit sizes. You may be thinking of utilizing a smaller powder size or needle size. I’ve listed some guidelines to help your progression (Remember you can always call or e-mail me for a specific question):

23 gauge or larger  Type 3 powder (25-45micron)
25 gauge needle  Type 4 powder (20-38micron)
27 gauge needle  Type 5 powder (15-25micron)
30 gauge or smaller  You can try Type 6 powder (5-15micron) but this is sometimes difficult and expen$ive.

The problem with finer particle sizes relates to surface area. Smaller particles have more surface per volume of paste, which is more challenging for a flux. A flux vehicle needs to reduce oxides on the backside of the die, the leadframe surface, as well as each paste alloy particle. It is best practice to use the largest powder diameter that will still be around 1/7th of the needle’s inner diameter. I generally use a needle that is 2/3 the desired deposit diameter.

These steps in planning will head you in the right direction, but if you are still experiencing clogging with a solder paste that should go through the size needle you selected:

1) Lower the pressure, 30psi is the max. pressure I’d ever think about subjecting a paste to.
2) Review storage suggestions and check for flux separation.
3) Use a larger needle tip if possible.
4) Try a conical needle. These are generally plastic, and tapered to help the paste flow properly through the equipment.
5) Double check the dispensing equipment, verify all the internal parts are working properly.