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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Use of solder paste for leaded thru hole parts????

Upinder Singh

#15194

Use of solder paste for leaded thru hole parts???? | 30 June, 1998

Hi all . Thanks to Ryan, Brian , Justin and Dave for the timely help earlier. I would appreciate if somebody could help me in the stated issue: I am trying to to place one thru hole 20 pin connector along with the SMT components by paste printing and reflow. Can anybody suggest me the size of the holes on the screen / stencil (by how much should it be bigger or smaller than the hole size on the board) to get a good filling of paste and a good fillet after reflow? What other care needs to be taken while trying stabalizing this process?? U can also reach me at (414) 783-6080 email: upinders@hotmaiil.com and don't forget smtnet. Regards Upinder ===============

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Earl Moon

#15196

Re: Use of solder paste for leaded thru hole parts???? | 30 June, 1998

| Hi all . | Thanks to Ryan, Brian , Justin and Dave for the timely help earlier. | I would appreciate if somebody could help me in the stated issue: | I am trying to to place one thru hole 20 pin connector along with the SMT components by paste printing and reflow. Can anybody suggest me the size of the holes on the screen / stencil (by how much should it be bigger or smaller than the hole size on the board) to get a good filling of paste and a good fillet after reflow? | What other care needs to be taken while trying stabalizing this process?? | U can also reach me at (414) 783-6080 | email: upinders@hotmaiil.com | and don't forget smtnet. | Regards | Upinder | =============== It depends on several factors. One would be the type of SMT devices requiring what type stencil thickness, as an example for fine pitch. This would corelate to the size connector pins and pad/hole sizes so determination could be made if a step down stencil would be necessary. If SMT devices are not fine pitch (unlikely) a thicker stencil could be used to deposit more paste on pads and in holes. Also, bigger annular rings provide more area for paste application but this is dependent on connector pin spacing and size. Additionally, square or round pins are preferred over those rectangular. With the specified paste amount on the pads and in the holes, the pins will push through, and retain, a certain amount. During reflow, wetting action will be effected both in the up and down direction as gravity and capillary action takes place. Another factor concerns hole to board thickness ratios. If if this ratio is numerically large (say 6:1 or more) less solder filling will be effected in the holes and around the pins meaning less desirable fillets. What are your specific parameters relative to all the above? I suspect these are simple boards, but? Earl Moon

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Upinder Singh

#15197

Re: Use of solder paste for leaded thru hole parts???? | 6 July, 1998

| | Hi all . | | Thanks to Ryan, Brian , Justin and Dave for the timely help earlier. | | I would appreciate if somebody could help me in the stated issue: | | I am trying to to place one thru hole 20 pin connector along with the SMT components by paste printing and reflow. Can anybody suggest me the size of the holes on the screen / stencil (by how much should it be bigger or smaller than the hole size on the board) to get a good filling of paste and a good fillet after reflow? | | What other care needs to be taken while trying stabalizing this process?? | | U can also reach me at (414) 783-6080 | | email: upinders@hotmaiil.com | | and don't forget smtnet. | | Regards | | Upinder | | =============== | It depends on several factors. One would be the type of SMT devices requiring what type stencil thickness, as an example for fine pitch. This would corelate to the size connector pins and pad/hole sizes so determination could be made if a step down stencil would be necessary. | If SMT devices are not fine pitch (unlikely) a thicker stencil could be used to deposit more paste on pads and in holes. Also, bigger annular rings provide more area for paste application but this is dependent on connector pin spacing and size. Additionally, square or round pins are preferred over those rectangular. | With the specified paste amount on the pads and in the holes, the pins will push through, and retain, a certain amount. During reflow, wetting action will be effected both in the up and down direction as gravity and capillary action takes place. | Another factor concerns hole to board thickness ratios. If if this ratio is numerically large (say 6:1 or more) less solder filling will be effected in the holes and around the pins meaning less desirable fillets. | What are your specific parameters relative to all the above? I suspect these are simple boards, but? | Earl Moon ====================================== Thanks Earl. Well following is the data regarding the product. 1. The panel consists of 21 boards. 2. The surface I mentioned would have 3 SMds and 1 T/hole connector. 3. PCB thickness is 55 mils and the width of the hole on the PCB for the thru-hole connector is 40 mil. 4. Leads of the connector are rectangular with 10 mil thickness and 24 mil width, with a pitch of 90 mil between the leads. 5. Two of the SMT components are 10 pin relays with a pitch of 100 mil (0.1") and the other one is 16 pin SOIC with a pitch of 50 mil. 6. The stencil which we are using right now for SMDs is 8 mil thick. Because of the space constraint we cannot think of a step down stencil. Any advice....??? Regards Upinder ===============

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Bob Willis

#15195

Re: Use of solder paste for leaded thru hole parts???? | 10 July, 1998

You can get a report and CD ROM on pin in hole reflow assembly from the SMTA main office in the USA. They also have a new report on Double Sided Reflow Design and Assembly. | Hi all . | Thanks to Ryan, Brian , Justin and Dave for the timely help earlier. | I would appreciate if somebody could help me in the stated issue: | I am trying to to place one thru hole 20 pin connector along with the SMT components by paste printing and reflow. Can anybody suggest me the size of the holes on the screen / stencil (by how much should it be bigger or smaller than the hole size on the board) to get a good filling of paste and a good fillet after reflow? | What other care needs to be taken while trying stabalizing this process?? | U can also reach me at (414) 783-6080 | email: upinders@hotmaiil.com | and don't forget smtnet. | Regards | Upinder | ===============

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