Why Assembly Jobs Go On Hold

There are a variety of reasons PCB manufacturers, assembly houses and engineering departments put jobs on hold. Once a job is started, the parts are kitted up, boards are procured and assembly time is scheduled. When this process comes to a grinding halt because something is wrong, it costs the manufacturer or assembler time, which is typically passed on to the customer in the form of additional charges. The time frame for the fix determines if the job stays on the floor for a short time or if all parts are recalled back to stock, rebagged, and the partially assembled boards go back in storage.

The number one cause of delay in assembly is a matter of communication timeliness. If a manufacturer promises a three day turn-time and they run into a problem, that promise is no longer valid because it may take two or three days to receive clarifying information necessary to resolve the issue. If time is critical, it is absolutely essential to keep communication open in order to overcome any problems in minutes versus days.

After a job has been placed on hold a number of times, the price may go up as the manufacturer attempts to recoup their losses. Because they cannot afford to shut the production lines down, even a short wait from a missing stencil or a Gerber router file may cause your job to be put on hold. The assembly company needs to change the stencil set up, fill the pick and place machines, assign the right people, do a test run, and finally process your job with intensive quality assurance and possible rework. For this reason, your job will be set aside at the station where the problem lies and cannot continue until the problem is sorted out. Ensuring that your job runs properly takes a bit of work, but having your assembled boards on time is worth the effort. The best advice is to communicate with the assembly house and make sure you have sent all the information and parts needed. Any special instructions need to be very clear and visible they can be captured in Engineering.

While communication is typically the largest and most frequent delay, there are many other delays that occur in the manufacturing and assembly process including:

Main Assembly Holds

• Missing stencil paste files requiring the job to wait while a stencil is made
• Missing XYRS files preventing the pick and place machines from knowing where to place the parts
• Missing polarity markers for diodes, rectifiers and capacitors causing confusion
• Incomplete BOM information—missing part numbers, descriptions, and reference designations
• Manufacturer part number supplied does not match description
• Customers supplying the BOM with their own internal part numbers only
• Poor quality PCB with defects that make a PCB reorder required
• Multiple versions sent of same file causes confusion as to which file should be used

Main Parts Procurement Holds

• Specifying a component that is no longer available, obsolete or available in only limited quantities
• Choosing parts with long lead times, necessitating a buyer searching around for quicker replacements
• The client choosing obscure vendors for parts

Main PCB Fabrication Holds 

• Missing Gerber board outline
• Missing drill file
• Missing or incorrect fabrication specification info
• Missing layer sequences for multi-layer boards
• Impedance specification which cannot be achieved
• Incorrect drilled hole size causing the component to not fit
• Extended lead time on PCB material—customer ordering boards without checking stock for less common materials such as thin copper foil, flex materials, or Kevlar
• Design does not pass a design rule check

Main Consignment Holds

• Supplying panelized boards without panelized stencil requiring new paste stencil
• Missing parts from the kit up
• Wrong part kitted
• Insufficient quantity, including insufficient overages
• Missing information in the fabrication file

Format Requirements on Small Parts

• Lack of proper documentation with kit (packing slip with job number, purchase order number, company name, etc.)
• Not putting a full kit together then drop shipping miscellaneous parts (split shipments with no documentation)
• Failure to including specific fabrication notes with package
• Sending alternate parts without annotating the changes in the BOM

These items can be used as a rough checklist to make certain that everything is properly organized and your design is ready to be assembled. Even with advanced preparation and forethought, there are still occasionally issues and holds. If time is of the essence, being open to quick communication is the key to meeting deadlines and keeping projects moving forward.

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