碰面 is a separable verb (离合词) meaning 'to meet up' or 'to run into each other'. The first syllable 碰 and the second syllable 面 can split apart to insert a measure word or time expression, e.g., 碰个面 ('meet briefly'), 碰过一次面 ('have met once'). It's similar to 见面 but slightly more informal and often implies a chance encounter. When specifying who you meet, use 跟/和 before the person: 跟他碰面.