Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Aperture sizes for printing SMD adhesive

Mark Alder

#12566

Aperture sizes for printing SMD adhesive | 19 February, 1999

Please could you suggest a recommended aperture sizes for printing of smd adhesives. Any recommendations on stencil thickness as well as stencil finish will be appreciated.

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Tony A

#12567

Re: Aperture sizes for printing SMD adhesive | 19 February, 1999

| Please could you suggest a recommended aperture sizes for | printing of smd adhesives. Any recommendations on stencil thickness as well as stencil finish will be appreciated. |

Mark, talk to Irene Horvath at I Source Technical Services, Inc. Her number is 949-453-1500. I use their stencils and they have been helping me for over three years. Their home page is www.i-source.com

Thanks

Tony A

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Dave F

#12568

Re: Aperture sizes for printing SMD adhesive | 22 February, 1999

| Please could you suggest a recommended aperture sizes for | printing of smd adhesives. Any recommendations on stencil thickness as well as stencil finish will be appreciated. | Mark: About the only rule of printing adhesives is: Keep it off the pads. As, an indicator, here are a bunch of approaches. If you don't like these your adhesive supplier and possibly your printer supplier are good sources of help also. TTYL Dave F

Stencil, adhesive

1 Using a 0.012" thick stencil Dot dia = (distance between pads-1 mil)*0.90/2

comp type standoff aperature 0402 0.002 0.030 0603 0.003 0.035 0805 0.003 0.045 1206 0.004 0.050 TAJA 0.004 0.050 TAJB 0.005 0.065 TAJC 0.006 0.080 TAJD 0.010 0.090 SOIC 0.015 0.080 PLCC 0.030 0.080

Print speed 2 to 8 IPS Metal squeegee blade Direct contact printing Downstop 0.075

Adhesive: High viscosity 600-700kcps Higher thixotropic index High contrast colors

2 Stencil material: metal or plastic, no difference in print, metal is easier to clean, no static prob., available Stencil thickness: Chips 0.006", SOIC 0.010" Snapoff: to increase dot height, up to 0.040" can be used Squeegee material: metal on metal, polycarbonate on plastic Print speed: 1 to 2" per sec Squeegee pressure: 0.3 to 0.3 kg/cm ... enough to clean wipe the stencil Seperation speed: Slow ... 0.1 to 0.5 mm/sec over 3mm seperation distance Print sequence: print print

3 comp no dots aperature dot pitch 0603 2 0.020 0.015 0805 2 0.024 0.020 1206 2 0.032 0.024 SOT23 2 0.028 0.028 1812 2 0.055 0.043 SO8 2 0.055 0.043 SO14 2 0.055 0.043 position dots 1/3 to 1/2 under component

4 Comp aperature 0402 0.012-0.016" 0603 0.016-0.020" 0805 0.020-0.024" 1206 0.040-0.047" miniMELF 0.040" SOT23 0.040" 1812 0.050-0.060"

5 plastic stencil: natural acetal stencil thickness: 2mm less variation printing 0.6 to 2.8 mm dia aperatures, but holes too small to print 0.6mm. 1mm is best tradeoff. not all glues are the same, but roughly: aperature diameter equals print diameter print height equals 1/3 thickness

6 Gluing with epoxy (0805) 0.006" 0.050"x 0.020" perpendicular w/rounded corners (0603) 0.006" 0.040"x0.015" perpendicular w/rounded corners

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