Is double-sided mounting still possible with the latest packages?

When I think of packages like some DFN or 0201 resistors I wonder where they would place glue dots. My UDFN is 1.2mm x 1mm. And glue dots on 0.5mm pitch WLP seem completely out. Is it still possible to fix parts at the bottom of a PCB for soldering?

Gluing is seldom needed/used these days. How the process is done exactly will depend on your fab.

But most will first populate the high-density side and solder it, and in a second run, the other side will be done. The components on the high-density side will usually be held by their surface tension. The manufacturer will also slightly change the temperature profile for the second side, so the higher temperature “capacity” of the high-density side will keep the components in place.

Some packages can not be reflowed twice, because of their high-temperature sensibility. These should be placed on the side soldered last.

But the most important thing is, talk to your manufacturer, they can help you and very often can provide you with their assembly/layout guidelines. If you follow them it will save you a lot of money and trouble in the end. Proper PCB assembly is not a totally straightforward process. It requires communication between the customer and the assembler and a lot of tweaking.

Read More: How Does BGA Soldering Work

#PCB Assembly

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Oliver Smith

Oliver is an experienced electronics engineer skilled in PCB design, analog circuits, embedded systems, and prototyping. His deep knowledge spans schematic capture, firmware coding, simulation, layout, testing, and troubleshooting. Oliver excels at taking projects from concept to mass production using his electrical design talents and mechanical aptitude.
Picture of Oliver Smith

Oliver Smith

Oliver is an experienced electronics engineer skilled in PCB design, analog circuits, embedded systems, and prototyping. His deep knowledge spans schematic capture, firmware coding, simulation, layout, testing, and troubleshooting. Oliver excels at taking projects from concept to mass production using his electrical design talents and mechanical aptitude.

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