EEVblog Electronics Community Forum
Electronics => Manufacturing & Assembly => Topic started by: madhu.wesly01 on January 12, 2019, 09:46:03 am
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Hi, :)
I have designed few PCBs and got them fabricated. When I compared my PCBs with other available commercial/industrial Boards, I observed lot of difference in Quality and exposed copper PAD strength. Actually, I have maintained better specifications only for my boards fabrication - 4Layer, FR4, TG170, 0.8mm thickness, 35microns for outer layer, and 17.5micron for inner layers, ENIG finish, Green solder mask. What might be the culprit here for the issue??? Any suggestions/pointers on this will be appreciated.
It would be good if I can get good resources on Key Engg. specs of PCB manufacturing.
Thanks in Advance.
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what do you mean by 'strength'. ?
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Hi @mrpackethead,
Please find reply below for your query:
what do you mean by 'strength'. ?
Reply: The actual issue I came across is - As we need to solder wires for external Battery power supply / Data lines on to the exposed Pads on PCB, after soldering, though there is not much strain(by pulling the soldered wire with some force), the soldered wires along with the Pads came off from a couple of PCBs.
I think this will answer your query.
Thanks in advance.
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That's a problem with your design (not using a through hole connection, no strain relief and tie-down). Some fabs may have boards with better copper adhesion but it really doesn't get that much better.
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Yes, totally aggree. Soldering wires to pads is just asking for trouble if you have no other mechancial method of holding them in place.
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You can add small via holes in the corners of the wire solder pads to increase the resistance to tear, but it is no magic fix. As previous commenters already mentioned, you must add some strain relief feature. If the pad does not break away, you can still get fatigue cracks on the copper strands just where the solder ends. Sometimes this could be just inside the wire jacket.
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Thanks for your help guys.
Good to know about strain relief, tie-down, un-plated holes in the PCB which help me in getting out-of this issue.
I would like to know if I could find the PCB fab specifications on what constitutes a industrial, commercial or automotive grade PCBs. Does anyone knows what are the major characteristics that define these groups?? Here I am thinking few below and what should I choose for these while uploading my Gerber data:
a. Copper thickness, b. dielectric material, c. TG, d. solder mask, e. Board thickness
Thanks in advance.
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I'm not sure these groups exist, you spec your board according to its requirements.
This post https://www.tempoautomation.com/blog/automotive-industry-standards-for-pcb-design-and-manufacture/ (https://www.tempoautomation.com/blog/automotive-industry-standards-for-pcb-design-and-manufacture/) discusses the various requirements for automotive but if you were to download the PCB requirements discussed I think you might find they can be met with perfectly normal boards . Automotive assemblies however can specify components with specific automotive approvals for extra fun & cost when sourcing.
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Madhu,
Familiarise yourself with IPC documentation on class 1 to 3 board definitions ,
This information is found in various IPC publications. www.ipc.org/ (http://www.ipc.org/)
Documents can be purchased from IPC alternatively Your local university library should be able to get them in or may be already has them in the reference collection.
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That's a problem with your design (not using a through hole connection, no strain relief and tie-down). Some fabs may have boards with better copper adhesion but it really doesn't get that much better.
Sure it does. I had so many lifted pads when soldering SMD parts from PCBs fabbed in china, that I completely stopped using them for prototypes. My time is worth more than whatever the company was saving by it.