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Pasting a thru-hole part at SMT

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#52784

Pasting a thru-hole part at SMT | 4 December, 2007

I have a thru-hole connector that I am trying to paste on my screen printer and then reflow it. I need to know if any of you have done this before and what your stencil would look like? It is a 28 pin connector.

Please let me know.

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#52787

Pasting a thru-hole part at SMT | 4 December, 2007

If you want to do this process, you should ask how to design the board for this process. Regular hole dimensions in the board will not work for this process.

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#52788

Pasting a thru-hole part at SMT | 4 December, 2007

Ok, How should the PCB be designed to accomodate this?

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#52790

Pasting a thru-hole part at SMT | 4 December, 2007

Search the fine SMTnet Archives for previous discussion. This technique has been called 'pin-in-paste,' 'paste-in-hole,' 'intrusive reflow,' 'alternative assembly and reflow technology' and who can remember all the other consultant buzz-words. Look at the following current thread that provides a link to a trade journal article on lead-free paste-in-hole and a pastage of guidelines from that article: http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=52780

Beyond the fine SMTnet Archives, look at: * UIC, Comprehensive Guidelines for the Implementation of the AART Process http://www4.uic.com/wcms/WCMS2.nsf/index/Resources_44.html

* IPC-7525, Table 2 Process window for intrusive soldering * "Stencil Design for Mixed Technology Through-hole / SMT Placement and Reflow" Coleman, WE; Photo Stencil, Colorado Springs, CO http://www.smtnet.com/express/200003/stencil/

* Our ol' friend Bob Willis has been involved in PIH and written several articles. The link below provides links to some of Bob's and others' writings on the topic: http://www.smtinfo.net/Db/_Pin%20In%20Paste%20Soldering.html

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#52792

Pasting a thru-hole part at SMT | 4 December, 2007

Frankly it's not a good process for large connectors. Messes up your screen printer and you get min acceptable solder joints, if that. Select solder is the way to go, especially with all the smaller units out there.

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#52793

Pasting a thru-hole part at SMT | 4 December, 2007

Real Chunks: Do you think a 28-pin connector is too large? For us, it's all about the number of rows. One or two rows are no big whoop. Three rows and greater, now that's when it gets messier.

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#52794

Pasting a thru-hole part at SMT | 4 December, 2007

this is a two row connector that I'm talking about. We were going to select solder it or wave it but we are just trying to make the process faster and if I can get this to work, it will definitely save time for us.

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#52796

Pasting a thru-hole part at SMT | 4 December, 2007

With two rows, you can overprint to the outside to make up the solder volume. It's when you have rows in the middle that things get tough.

A good stencil house should already have overprint libraries for this.

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#52799

Pasting a thru-hole part at SMT | 5 December, 2007

Hi, Is depend on the size, you may also able to using different type of solderpaste to accomdate instead on PCB.

Hun

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#52801

Pasting a thru-hole part at SMT | 5 December, 2007

We have done Paste-In-Hole process for 4 years.I think this prcess is suitable for 28-pins connector. Of course, you must assure the connecotr can endure high temperature firstly.Secondly, you need calculate the volume of solder paste, you can refere to this formula as belows: H=Hole diameter D=Lead diameter T=Board thickness L=Width of lead in the X direction (For square lead) W=Width of lead in the Y direction (For square lead) ��=3.14 Hole Volume (HV)=(��)(H/2)(H/2)(T) Lead Volume (LV)=(��)(D/2)(D/2)(T) (For round leads) Lead Volume (LV)=(L)(W)(T) (For square or rectangular leads) Annular Ring Area(RA)=(��)(L/2)(L/2)-(��)(H/2)(H/2) Required solder volume (SV)=HV-LV "Required Print Volume (PV)=(2)(SV) (50%) " Required Print Area (PA)=(F)(PV)/stencil thickness F=Inspection Factor .7=no fillet .9=fillet on both sider 0.8=fillet on primary side 1.0=large fillet on both sides Note: Must consider the solder paster volume for annular ring.

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#52803

Pasting a thru-hole part at SMT | 5 December, 2007

All posters here are right. My point was you have to design your board to the process. You cannot simply take any connector and change it to Pin and Paste. So much depends on your aperture openings, hole size to pin size, board thickness, number of rows, etc. Plus the results are vary as well. Depending on your paste, voids, balling wetting all are characteristics of different pastes. Connectors can be a major heat sink as well. Profiling for large connectors can be a challenge.

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