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December 22, 2025 - Updated
December 3, 2025 - Originally Posted

T4 vs T5 Solder Paste Particle Size

I know the 5 ball rule and AR of +66 for type 4 paste but what is the rule for type 5? I cant seem to print .0201 or .01005 and micro BGA consistently with a 4 mil thick stencil. How do I determine the need for T5 and justify the cost increase if T4 could still work?

K.P.

Expert Panel Responses

While 0201 will still work with T4 paste, 01005 and µBGA typically requires T5 solder paste and stencil thickness 3 mil (75µm). A mix of 01005 and large components might require the use of step stencil technology.

Manuel Schöllig
Product Manager Soldering
Inventec Dehon

Product manager for soldering products, including solder pastes, liquid and tacky fluxes.

Type 5 solder paste can theoretically print through an aperture size of 5 mils (5-ball rule) although 7-8 mil aperture size is recommended. That should be well below the typical dimensions for 0201 Imperial, 01005 Imperial, and microBGA aperture sizes. Keep in mind that the aspect ratio should be kept above 1.5 and the area ratio above 0.60 as well. For a 4 mil thick stencil, the minimum aperture size should be greater than 9.6 mils to meet the aspect ratio and area ratio rules.

Before considering a switch from Type 4 to Type 5 solder powder size, I suggest checking the print setup.

Is there good contact between the stencil and the pads?
Are there high spots on the PCB (legend marking ink, or high copper) that could cause "off-contact" printing?
Is there good and repeatable alignment between the apertures and the pads?

It also may be beneficial to use a ceramic type nano-coating on the stencil. This tends to improve solder paste release, and minimize variation from print to print.

Tony Lentz
Field Applications
FCT Assembly

Tony has worked in the electronics industry since 1994. He worked as a process engineer at a circuit board manufacturer for 5 years. Since 1999, Tony has worked for FCT Companies as a laboratory manager, facility manager, and most recently a field application engineer. He has extensive experience doing research and development, quality control, and technical service with products used to manufacture and assemble printed circuit boards. He holds B.S. and M.B.S. degrees in Chemistry.

Both those sizes should print. Worth checking legend height etc first often it produces a stand off so high the pads cant hit the stencil so paste cant deposit properly.

Greg York
Technical Sales Manager
BLT Circuit Services Ltd

Greg York has over thirty two years of service in Electronics industry. York has installed over 600 Lead Free Lines in Europe with Solder and flux systems as well as Technical Support on SMT lines and trouble shooting.

Based on my experience and what I’ve seen as best practices in the SMT industry, Type 4 paste is generally at its limit when printing 0201 metric, 01005, and micro-BGA, due to its particle size (~20–38 µm). At such fine geometries, the traditional “5-ball rule” no longer guarantees stable print results; the real driving factor becomes the Area Ratio (AR) of the stencil:

AR ≥ 0.66 for reliable release
AR ≥ 0.75 is safer on micro-BGAs due to paste volume variation

As far as I know, there is no formal standard (IPC or others) that mandates when Type 5 must be used. However, there is a very strong industry consensus:

if the apertures fall below or very close to the AR limit with Type 4, then the recommended option is to move to Type 5 (~15–25 µm). The smaller particle size significantly improves aperture filling, transfer efficiency, and volume consistency on ultra-fine features.\

From a quality and cost perspective, the justification is clear: Type 5 paste reduces insufficients, head-in-pillow, and volume variation on micro-BGAs. In most cases, a single µBGA defect costs more than the price difference between T4 and T5 paste.

Practical rule I usually follow

0201 metric / 01005 → Type 5
µBGA < 0.35 mm pitch → Type 5 minimum
µBGA < 0.30 mm pitch → Type 6

And if you are already experiencing issues with Type 4 + 4-mil stencil, the combination that typically delivers the best results is Type 5 + 3-mil stencil, and if possible, nano-coating to improve release.

Andres Rojas
Engineering Director / Master IPC Trainer (MIT)
AMMSA Solutions

More than 20 years of technical experience in the electronics industry in roles ranging from Process & Project Engineer to engineering manager and Technical Applications Engineer for Latin Americas. IPC Master Trainer, International speaker and consultant.

Particle Size T5's "5 ball rule and AR of 066 (050) " is same as T4 particle. 5 ball is Printing result. Aspect Ratio is related to Visicosity of Solder Paste and flatness of laser cutting Wall.
Printing .0201 or .01005 and micro BGA consistently with a 4 mil thick stencil could observe 2.1) the solder paste rolling before squagee (45° Squeege better than 60° Squeege); and 2.2) Paste releasing from the stencil Aperture (Releasing Speed and Stencil Pressure).

Zhongwei Chen
Process Supervisor
NexPCB Co; Ltd

25 years experience in SMT/COB industry, 10 years in Optical film by Sputtering and Evaporation.

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