There are no guidelines for when to use any Type of solder paste, except for what is on the assembly drawing, and that may only call out the alloy and flux but does not usually mention the particle size.
If the alloy and flux are detailed on the assembly drawing, but not the specific particle size or the specific vendor's solder paste PN, then you can choose which particle size you wish but you should verify this with your customer first. The vendor's specific PN will drive the particle size. 

J-STD-005 describes what the solder paste definitions are, but not which one you should use.

I can throw this out as a general guideline, if you have a CCA with apertures smaller than .010" in any direction, you probably should look at a Type 4. Type 5 is primarily for extremely small components with pads smaller than .005" in any direction. 

Do not jump into Type 4 or Type 5 if you are accustomed to using Type 3. Special care is required during printing to ensure you are not packing the smaller fines of a Type 4 paste in between the edge of the solder mask and the edge of the pads. Paste in this area does not agglomerate as part of the solder joint. Also you can get solder paste fines packed into vias, etc. if you are not careful.
In other words, you need to ensure your paste printing process is extremely robust, repeatable, and can print paste on the center of the pads with a standard 10% reduction in the aperture size. If your printer's capabilities and/or your printing operator/process cannot do this, you are going to have major issues with entrapped fines that could come loose.

Qualify your process first before jumping into a change of Type on production CCAs. When you think you can do it, be sure to train the inspectors to be looking for these issues before you build 10,000 CCAs with solder fines floating everywhere.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Datacom - Juliano Ribeiro
Sent: Thursday, April 10, 2014 12:52 PM
To: [log in to unmask]
Subject: [TN] Mesh Type

Dear All,

I'm find the specification of the Solder Paste Mesh Type.

For example, when I need to use Mesh type 4?

Tks

 

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Juliano Bettim Ribeiro

DATACOM 

ENGENHARIA DE PROCESSOS 
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+55 (51) 8446-2135

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