Design for Manufacture - Guides?

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#1
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Afternoon all.

I'm currently in the process of designing a new board that is to be mass produced (>1k production run) and I was wondering if anyone out there had some good information and or advice that they could share with me. No doubt the precautions I take now will save me much future heartache.

Any Web Links, Books, etc would be greatly appreciated.

Issues that I need to understand more are the costs involved with using a mixed board (SMT and TH components - ie extra time taken to hand solder Through hole components), dealing with component clearances when Pick and place machines are being used, etc.

My board is a stand alone controller so it has some bigish 5mm pitch screw down terminals (TH), and a handful of through hole (TH) chokes. I need to keep these components through hole.

I can see it is going to be a fairly lengthy learning process but its a bridge i just have to cross.

(the board I'm designing is relatively simple, 40 components or so, double sided using pth technology)

Look foward to some replies. I figure this thread should be useful not just for me but for the wider AVRfreaks community.

oddbudman

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HI oddbudman,
I wish you luck with your project. I have been using Atmega8515 and Atmega32, and always develop the PCB board with both DIP and TQFP type packages. The DIP make development easy, while the TQFP are easier to purchase (shorter lead time) and easy for the factory to handle. Exteranl eeproms I prepare the board for both TQFP and SOIC for purchasing reasons. resistors capacitors transistors if they can be I use SMD.

Regarding the mechanical issues, I would recommend seeking the advice of a professional mechanical Engineer.

Michael

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Any IO lines that go off the board should have some sort of protection even if only a 100 ohms in series with them.

Keep it simple it will not bite as hard

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In the past I have always talked to manufacturing about a prototype board and asked their opinion. It really helps to do this. You get insight into problems production might have, they get an input which they appreciate and costing and clearances will be something they should have all written down.

Even if you only take something on paper or a rough prototype, sitting down with them and talking through the board really works for me.

Hope this helps.

Trev

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I agree with Trevor's comments.

Talk to the component suppliers and select components readily available.

Talk to the assembly house and try to understand the assembly process.

Ask whether parts will be placed manually or by machines.
Whether the soldering will be done in a wave soldering or reflow process.

Whether the preheating of components will be affected by a mix of small ( low thermal capacity ) and large ( high thermal capacity ) components.

Enquire about the chemisty of the soldering proces ( no clean flux or some form of cleaning eg solvent or aqueous cleaning) and how residues might affect post assembly testing ( eg poor contact on a bed of nails etc )

Enquire about two pass assembly SMD and reflow followed by PTH and wave soldering.

Alternatively SMD in a wave soldering process and consequent requirement for component orientation with respect to board travel through the wave soldering machine ( to minimise solder shorts )

Enquire ( with your parts and PWB/PCB suppliers ) about the age and SOLDERABILITY of components.

Discuss the assembly proces and design your board ( panelisation ) to suit the manufacturing process that is the requirements of the assembly line with respect to the conveyers/palettes/ frames used during the assembly.

Dont forget testing requirements..include suitable connectors/testpoints in your PCB design to make testing/calibration/programing as worry free as possible.

Testing may be visual inspection, MDA ( manufacturing defect analysis), ICT functional ( in circuit bed of nails test) or hotbed testing.

Do not ignore the packaging of finished boards, you may have to package them in order to ship from assembly house to final assembly and distribution facility.

Hope I did not preach at you, good luck.

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I agree with Trevor's comments.

Talk to the component suppliers and select components readily available.

Talk to the assembly house and try to understand the assembly process.

Ask whether parts will be placed manually or by machines.
Whether the soldering will be done in a wave soldering or reflow process.

Whether the preheating of components will be affected by a mix of small ( low thermal capacity ) and large ( high thermal capacity ) components.

Enquire about the chemisty of the soldering proces ( no clean flux or some form of cleaning eg solvent or aqueous cleaning) and how residues might affect post assembly testing ( eg poor contact on a bed of nails etc )

Enquire about two pass assembly SMD and reflow followed by PTH and wave soldering.

Alternatively SMD in a wave soldering process and consequent requirement for component orientation with respect to board travel through the wave soldering machine ( to minimise solder shorts )

Enquire ( with your parts and PWB/PCB suppliers ) about the age and SOLDERABILITY of components.

Discuss the assembly proces and design your board ( panelisation ) to suit the manufacturing process that is the requirements of the assembly line with respect to the conveyers/palettes/ frames used during the assembly.

Dont forget testing requirements..include suitable connectors/testpoints in your PCB design to make testing/calibration/programing as worry free as possible.

Testing may be visual inspection, MDA ( manufacturing defect analysis), ICT functional ( in circuit bed of nails test) or hotbed testing.

Do not ignore the packaging of finished boards, you may have to package them in order to ship from assembly house to final assembly and distribution facility.

Hope I did not preach at you, good luck.

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When laying out the board if you must link adjacent pins, run tracks off the pads rather than put a track directly between the pads. Inspection and test can then see it is a tracked connection not a blob of solder.

Keep it simple it will not bite as hard

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If you have no SMD parts on the bottom of the board, it's likely that the TH parts will be wave soldered. (Top reflowed, bottom wave). Wave soldering is even possible with SMD on the bottom, but with more restrictions.