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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


High complex board manufacturing

Views: 3185

#58105

High complex board manufacturing | 16 February, 2009

Hi to everyone, we are building a high complex board (>1000 0402's, Micro BGA, QFP 0.4mm pitch, TSOP), we are trying to know what kind of equipment do you recommend to use in our factory, we already have Screen Printer, Chip shooters, Reflow oven, AOI, Stencil cleaner (manual), X ray, ICT... what else does a world class factory can recommend?

Thanx in advance

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#58212

High complex board manufacturing | 26 February, 2009

Zero Defect!

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aj

#58221

High complex board manufacturing | 28 February, 2009

A good SMT Engineer !

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#58222

High complex board manufacturing | 2 March, 2009

Hi Jorge, The success of such production purely depends on process control. One needs to first understand the board layout in detail, and evaluate any critical components for their temperature handling capabilities. Remember, you are dealing with complexity! So ... choose the right type of Solder Paste!

Here are few suggestions: 1. Calculate optimum stencil apperture openings to avoid process defects such as side balling, bridging, no/less solder, etc. 2. I recommend use of an Ultrasonic Stencil cleaner, to eliminate failure caused by clogged stencil appertures. 2. Measure the solder paste height after stencil printing and record data. 3. Carry our a DFM of the PCB design by evaluating with respect to your placement machine capability. 4. Setup an optimum Reflow Profile using a populated PCB and analysing all hot/cold spots on board. Allow yourself sufficient time for this operation. 5. In addition to the above, you should consider a 5DX automated X-Ray system post reflow, with an in-line AOI pre-reflow for Process verification during production.

Study the Cleaning, Conformal coating, and Underfill requirement (if any) and look out for suitable equipments for the same.

Cheers!!! Sachin (India)

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#58223

High complex board manufacturing | 2 March, 2009

I'm not a world class factory, but imo equipement wise, 3D paste inspection might be a thing for you to look into.

grtz, Loco.

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#58224

High complex board manufacturing | 2 March, 2009

Jorge,

Seems You have good Infrastructure in Place, here are few concerns to be consider before switch over for Alpha run. 1. Study PWB Design which to run for(Pad Design/Layout/Geometry across the Designations, Spacing between each locations, Solder Mask finish> Glossy/Matte & Plating). 2. Select Solder Paste according to Your Customer or In-House Specifications which is compatible for expected Process. 3. Use Chemical Etch / Electro Polished Stencil with proper Aspect Ratios (AR=>1.5) & Area Ratios(ArR=>0.66) as Calculated. Also try to select Square Rectangle Aperture Openings for 0402 Chips with up to 10% reduction, seriously consider Stencil Thickness from 4.5 Mils to 5.5 Mils. 4. Though Your Process has to run with Manual Stencil Cleaning, set the frequency as low as 4 to 5 Print Cycles. Use Ethanol / Iso Profile Alcohols with Lint-free cloth to clean Stencil foil. Though Aperture openings are optimized 16 Mils, set a frequency to use Air/Brush Cleaning at QFPs, TSSOPs, CSPs & �BGA Locations to ensure no Aperture Blockage. 5. Ensure 100% Placement Accuracy at Pre Reflow specially at 0402 Chips to avoid Over Hangs / Tomb-stoning. 6. Stick to Ramp Soak Spike(RSS)/Low Long Spike (LLS) Type Reflow Profiles. Much better to fall Time & Temperature graph under Supplier Specifications. 7. Trigger immediate feedback & take Containment Actions from Post Print, Post Place & Post Reflow to previous operations. 8. Check for HiPs (Head-in-Pillows) at �BGA locations at AXI/AOI. Also check for Joint Integrity by Fly selected Locations. 8. Run first 2 cards & ensure to undergone relevant Tests & approve for further Process. 9. Calculate FPY & share the report to Your Teams & Customer if required, also appreciated to share with SMTnet ! 10. Enjoy the Job & Celebrate the Success, Good Luck.

Tnx, David, India.

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#58226

High complex board manufacturing | 2 March, 2009

Thanx for all your recomendations, we already ask for a 3D SPI and help us well, we are asking for a ultrasonic stencil cleaner. By the way how do you deal with the 'head in pillow' defects? is there a solder paste alloy / profile issue?

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#58227

High complex board manufacturing | 2 March, 2009

You may need a glue despinser if you populate bottom side then wave. maybe a board deatacker at front of the line how about a multifunction pick and place machine so you can process all parts out there. we cleaned our stencils for years then we got a ultrasonic cleaner big differance our stencils are now clean. Good Luck

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#58234

High complex board manufacturing | 3 March, 2009

Well Jorge,

Typically, these defects are caused from Manufacturing Process of the Devices than Assembly Process. Still you may may go to tackle Possibilities/Causes across the Line.

1. Solder Paste Alloy Chemistry: Go for High Temperature Flux Activation which helps to remove Moistures from PCB Pads & Device Spheres. 2. Device: Ensure Alloy used for Spheres are absolutely compatible with Solder Paste to be Processed. Also refer Temperature Vs Time Graph from Part Manufacturer. Moisture accumulation during Manufacturing / Assembly Process & improper Molding factors which may leads for Warpage during Reflow are also shall cause for HiP. 3. Printing: Print M/A with >25% out of Lands in PCB, Insufficient/Inconsistent Alloy deposition which causes for poor Tackiness between Device Spheres & Paste deposited. Also note that Aperture Opening Designs in Your Stencil draws a huge role for these defects. 4. Placement: Placement M/A, Diluted Placement Forces leads for Device Misplace during Assembled Cards Transportation. 5. Reflow Profile: Improper (Insufficient/Dry Out)Flux Activation at Soak Phase. Let Reflow Profile outcomes fall under Part & Solder Paste Supplier Specifications.

Note: These defects have reported as Dangerous Assembly Defects since the Cards built with such defects shall pass all In-House Tests with minimum Electrical Joints & leads for Potential Failures !

Tnx, David, India.

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#58286

High complex board manufacturing | 6 March, 2009

Ain't that the truth. The most underrated item on any production floor

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