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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Frank S

#15583

Help me increase my first pass yields | 4 June, 1998

If you could measure and chart 3 variables in my process, what would they be? The boards that I produce are on panels that are 12up and 2x4 up. All boards are single sided paper base w/o plated thru holes. They are on scored panels that measure 7" x 17". Bare boards packed 25 in a bundle are removed fron the cellophane wrapping, hand stamped and then IC's are installed by machine before proceeding to SMT. SMT operations consist of dispensing glue on the board with a needle type glue dispenser. This inline system feeds the board into the SMT machine. The SMT machine populates 420+ parts on the panel and then the panel proceeds to a conveyer where it stops until it is visually inspected. Once satisfied the inspector releases the board to the curing oven. The board is inverted, top side parts are installed on a progressive assembly line, the board is wave soldered, touched up and then tested on a bed of nails fixture. Current first pass yields are 85%

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Pete M

#15588

Re: Help me increase my first pass yields | 4 June, 1998

Be more specific on your problems? | If you could measure and chart 3 variables in my process, what would they be? | The boards that I produce are on panels that are 12up and 2x4 up. All boards are single sided paper base w/o plated thru holes. They are on scored panels that measure 7" x 17". | Bare boards packed 25 in a bundle are removed fron the cellophane wrapping, hand stamped and then IC's are installed by machine before proceeding to SMT. SMT operations consist of dispensing glue on the board with a needle type glue dispenser. This inline system feeds the board into the SMT machine. The SMT machine populates 420+ parts on the panel and then the panel proceeds to a conveyer where it stops until it is visually inspected. Once satisfied the inspector releases the board to the curing oven. The board is inverted, top side parts are installed on a progressive assembly line, the board is wave soldered, touched up and then tested on a bed of nails fixture. Current first pass yields are 85%

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Dave F

#15587

Re: Help me increase my first pass yields/Whoa Let's Not Chart Yet | 4 June, 1998

| If you could measure and chart 3 variables in my process, what would they be? | The boards that I produce are on panels that are 12up and 2x4 up. All boards are single sided paper base w/o plated thru holes. They are on scored panels that measure 7" x 17". | Bare boards packed 25 in a bundle are removed fron the cellophane wrapping, hand stamped and then IC's are installed by machine before proceeding to SMT. SMT operations consist of dispensing glue on the board with a needle type glue dispenser. This inline system feeds the board into the SMT machine. The SMT machine populates 420+ parts on the panel and then the panel proceeds to a conveyer where it stops until it is visually inspected. Once satisfied the inspector releases the board to the curing oven. The board is inverted, top side parts are installed on a progressive assembly line, the board is wave soldered, touched up and then tested on a bed of nails fixture. Current first pass yields are 85% Frank: Three key factors that determine overall first pass yield are: 1 How well do you set-up your individual processes. 2 What is the quality of your in-bound materials 3 Are the individual processes capable Charting is generally used when the process is in control. You have at least 12 processes (each with a yield) that combine to produce your the overall 85% yield. Divide your overall process into individual steps and determine which step is hurting you the most. Fix that process. Go to the next most painful. Fix it. Get your processes in control. Monitor that it stays in control. Dave F PROCESS STEPS YIELD Fabricate bare boards Receive piece parts Hand stamp IC installation Dispense glue SMT machine placement Visual inspection Glue cure Install top side parts Wave solder Touched up Test TOTAL 85%

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M. Faisal Pandit

#15586

Re: Help me increase my first pass yields | 4 June, 1998

Frank, A couple of suggestions: 1. You may consider investing in a SPC Software package which would allow you to do a detailed analysis of your process. Panasonic's CIM Software Product, PanaPRO, has a well defined SPC application that can be used for this purpose. 2. The Feburary issue of SMT magazine has an article on Process Control authored by me and a collegue, which addresses process improvement related concerns. Thanks, M. Faisal Pandit faisal@pansonicfa.com Software Development Manager Panasonic Factory Automation

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Chrys

#15585

Re: Help me increase my first pass yields | 4 June, 1998

| If you could measure and chart 3 variables in my process, what would they be? | The boards that I produce are on panels that are 12up and 2x4 up. All boards are single sided paper base w/o plated thru holes. They are on scored panels that measure 7" x 17". | Bare boards packed 25 in a bundle are removed fron the cellophane wrapping, hand stamped and then IC's are installed by machine before proceeding to SMT. SMT operations consist of dispensing glue on the board with a needle type glue dispenser. This inline system feeds the board into the SMT machine. The SMT machine populates 420+ parts on the panel and then the panel proceeds to a conveyer where it stops until it is visually inspected. Once satisfied the inspector releases the board to the curing oven. The board is inverted, top side parts are installed on a progressive assembly line, the board is wave soldered, touched up and then tested on a bed of nails fixture. Current first pass yields are 85% Where's your yield fallout coming from? Solder skips/shorts? Missing parts? Wrong/reversed parts? Gotta identify the problem before fixing it.

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Steve Schrader

#15584

Re: Help me increase my first pass yields | 5 June, 1998

| If you could measure and chart 3 variables in my process, what would they be? | The boards that I produce are on panels that are 12up and 2x4 up. All boards are single sided paper base w/o plated thru holes. They are on scored panels that measure 7" x 17". | Bare boards packed 25 in a bundle are removed fron the cellophane wrapping, hand stamped and then IC's are installed by machine before proceeding to SMT. SMT operations consist of dispensing glue on the board with a needle type glue dispenser. This inline system feeds the board into the SMT machine. The SMT machine populates 420+ parts on the panel and then the panel proceeds to a conveyer where it stops until it is visually inspected. Once satisfied the inspector releases the board to the curing oven. The board is inverted, top side parts are installed on a progressive assembly line, the board is wave soldered, touched up and then tested on a bed of nails fixture. Current first pass yields are 85%

The others are right, you need to find out where your defects are coming from, but I wouldn't spend a lot of time with software packages or charts just yet. With 15% fallout, you must be doing a lot of rework on the failed boards, just ask your rework people what they are constantly reworking then figure out which process is causing them.

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