In today's electronics industry, the demand has grown for products to be better, faster, and more user friendly. This has created a constant over turn of electronic devices causing manufactures to shorten their time-to-market window. OEMs (Original Equipment Manufactures) who performed their own preproduction and prototype assembling, no longer have the time and or equipment available to meet the market's needs. This started the creation of the contract manufacturing business where facilities were configured to handle quick turn assemblies known as rapid prototyping.

Typical prototype assembly work in electronics manufacturing usually means a small quantity of printed circuit boards manufactured over a programmed period of time. Rapid prototyping is a form of prototype assembly work that is performed in a short (1-5 day) time frame and typically costs more than that of standard prototype work.

Rapid Prototyping Obstacles:
The major cost and delivery time factors for any prototype assembly job are the issues that tend to develop prior to and during manufacturing. These designs can be loosely characterized as management driven or environment induced. For example, the assembly environment has a tendency to create restraints while the management drivers reflect the capability to overcome the difficulties imposed by the nature of the assembled products and the market. Some of these cost issues are easy to measure such as volume, cycle time, changeover time, and delivery performance. Other obstacles require extensive computing such as DPO (defects per opportunity) which take into account the number of components plus the number of solder joints per board. Many of the common problems are derived from non-measured issues such as gerber file inaccuracies and reflow profile setups. Table 1 is a list of some these potential pitfalls and cost drivers that are sometimes experienced before or during a prototype assembly build.

Conducting a Time Study:
There are several variables to consider when conducting a time study for any PCB assembly. It is important to first know the quantity of boards you are building. This will help determine what assembly level (ex. prototype, preproduction, small production, and large production) to use. It will also assist in defining the equipment level required for the build. The next factors to consider are the quantity and type of components being assembled. How many and whether the components are thru hole, surface mount, or both will dictate the type of equipment required as well as the process needed. Some other considerations include the initial setup time which is essential for performing tasks such as equipment programming and setup, process implementation, and board testing. Time spent refining these translates into costs known as the Non Recurring Engineering fees or NRE. The costs to perform the actual build are dictated by the quantity, level and design of the board. If the assembly is more prototype in nature, a large portion of the costs will be associated with labor. As the board and component quantities increase so does the need for more automated equipment. The cost of the machine, depreciation and maintenance create more of the expense offsetting the decrease in required labor.

Time Study Example:
Table 2 (below) is an example of a mixed technology board in which a time study was conducted at different quantity levels using various operations. The board consists of 543 SMT and 320 thru hole components. The assembly levels are categorized based on quantity of boards. The calculated times are based on estimated labor hours and equipment capability.

Rapid Prototyping Setup Checklist:
Please use our helpful checklist to guide you in the initial prototype setup process. The list has been broken up into 3 sections that include the automated and manual requirements, along with items that are common to both.

Table 2 - Time vs. Volume