|Ask the Experts|
February 19, 2020
Trouble Soldering a PC104 Connector
|Expert Panel Responses|
Alpha is a solder materials supplier and we offer solder preforms. We have worked with PC104 connectors and have successfully helped customers to solder this type of connector with flux coated SnBi solder washers. For this assembly, a separate reflow cycle at 180C was used after the standard SMT processes, which in our case involved two reflows, top and bottom side.
I realize that the use of SnBi solder presents a new issue, in that the customer may be unfamiliar with this alloy. For through hole solder connections, SnBi is quite robust.
The eutectic version of the alloy is RoHS compliant with a melt temperature of 138C. Therefore a separate reflow of ~ 180-185C peak will not disturb the existing solder joints present on the board that used SAC305 or SACX low silver solder. Some of the PC104 pins are connected to ground and power planes, and these might be the ones that presented problems.
It is important to use a soak profile so that the board is brought to a uniform temperature, ensuring that the ground and power planes reach the same temperature as the rest of the board. The flux type needs to be optimized to address the type of board, ENIG, HASL Sn, of OSP copper finish and the connector finish.
Global Product Manager
Is there anything special with the pins that are not getting soldered? Are there the same pins that you have problems with?
Is the amount of solder the problem or the location of the pins? My recommendation would be a solder paste dispensing equipment. I've seen several out there that can really help with this issue.
If placing the component post-SMT is an option, a soldering robot with a custom tip can probably do the job as well. However, that will add processing time so extra cost to your product.
Engineering and Operations Management
I would still recommend the use of performs, however I would recommend that the math be calculated to figure out how much solder is going to be necessary to fill the void between the volume of the lead and the volume of the pcb and the perform can be sized appropriately.
The use of fixtures where the performs, made of cored solder wire typically .032", could be prepositioned, then the pins or product can be inserted into the fixture. Then by flipping the total assembly over and removing the fixture the performs would be on all the pins and ready for reflow.
When this process was developed by Western Electric the method of reflow was vapor phase as any other equipment was not powerful enough to maintain the heat and reflow all the performs. I would suggest that this could also be your problem not enough energy being inputted into the product to reflow all the performs.
I hope this is useful and if more information is needed please don't hesitate to contact me at your convenience.
Vice President, Technical Director
We use press fit PC104. Fast and reliable...Tim Swanson, NEMO Manufacturing
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